CN107525733A

CN107525733A - Well head downhole corrosion speed correlation model algorithm and the downhole corrosion speed on-line monitoring method using this algorithm

Info

Publication number: CN107525733A
Application number: CN201710675014.7A
Authority: CN
Inventors: 刘晶姝; 龙媛媛; 谭晓林; 杨为刚; 刘瑾; 刘丽; 柳言国
Original assignee: China Petroleum and Chemical Corp; Technology Inspection Center of Sinopec Shengli Oilfield Co
Current assignee: China Petroleum and Chemical Corp; Technology Inspection Center of Sinopec Shengli Oilfield Co
Priority date: 2017-08-09
Filing date: 2017-08-09
Publication date: 2017-12-29
Anticipated expiration: 2037-08-09
Also published as: CN107525733B

Abstract

Well head downhole corrosion speed correlation model algorithm and the downhole corrosion speed on-line monitoring method using this algorithm, pass through experimental study, determine the relevance of underground different depth corrosion rate and well head corrosion rate, establish well head downhole corrosion speed correlation model algorithm, and then utilize well head corrosion rate, calculate the corrosion rate of underground different depth, new compensation method is studied to solve the problems, such as that heavy wall column inductance probe test piece measured value deviates linear relationship with former inductance probe mathematical modeling curve, realize that well head corrosion rate is monitored on-line, the corrosion condition for solving the problems, such as underground equipment can not be monitored effectively.With significant economic and social benefit, there is good popularizing application prospect.

Description

Well head downhole corrosion speed correlation model algorithm and the downhole corrosion speed using this algorithm Rate on-line monitoring method

Technical field

The invention belongs to oilfield monitoring technical field, more particularly to well head downhole corrosion speed correlation model algorithm and use The downhole corrosion speed on-line monitoring method of this algorithm.

Background technology

CO₂It is initially to start in 1962 as the additive of acidifying and frac treatment used in people, hereafter As a kind of well treatment medium, its purposes has been developed rapidly.As deep layer contains CO₂The exploitation of oil gas field and three Re-injection CO in secondary oil recovery₂The extensive use of intensified oil reduction technique (EOR), CO₂Etching problem annoyings the hair of oil and gas industry all the time Exhibition.CO₂Oil well produced liquid is driven rich in CO₂, meeting water can cause to produce well underground equipment heavy corrosion.According to preliminary screening, in triumph Oil field, it is adapted to CO₂The low permeability oil field reserves of the displacement of reservoir oil are just up to more than 200,000,000 tons, if all using CO₂The displacement of reservoir oil is developed, and can be improved oil field and be adopted Yield 10%~15%, it is contemplated that 33,000,000 tons to 47,000,000 tons of newly increased recoverable reserves.Therefore, it is necessary to by targetedly studying For CO₂The extensive use of drive technology solves the bottleneck problem of extraction well underground equipment corrosion, and can instruct Produced Liquid collection defeated along journey Corrosion protection, strong guarantee CO₂Drive the economy of downhole hardware and the operation of surface gathering system corrosion protection scheme and reliable Property, there is significant economic and social benefit.

Solve the problems, such as any kind of corrosion control, first it is to be understood that its etching characteristic, its secondary monitoring from corrosion, The basic procedure of management and the corrosion control of corrosion data is carried out.CO₂The corrosion monitoring technology of well is driven, well head can be subdivided into Corrosion and the corrosion monitoring problem of underground, traditional monitoring means are mainly lacing film (ring) technology, and this technology has economic throw Enter the characteristics of small, but its test period is grown, result of the test by the error of man's activity it is big the shortcomings of, can not also react corrosion in addition Process data, can effectively solve above technical problem for current on-line corrosion monitoring technology.Inductance corrosion monitoring technology It is an on-line monitoring technique developed in recent years, due to the measuring principle that it is electromagnetic induction, there is measurement sensitivity Height, to the blanket feature of medium, it has been obtained for extensive use in oil refining and chemical industry, but for the corrosion of pit shaft A series of problems also be present in monitoring.

The content of the invention

Downhole corrosion it is an object of the invention to provide well head downhole corrosion speed correlation model algorithm and using this algorithm Speed on-line monitoring method, the algorithm used are that the relevance model reckoning underground of downhole corrosion speed and well head corrosion rate is rotten Speed is lost, mainly studies new compensation method, it is inclined to solve inductance probe measured value and former inductance probe mathematical modeling curve The problem of offline sexual intercourse, by experimental study, the relevance of downhole corrosion situation and well head Corrosion results is determined, and then utilized The corrosion rate monitoring result of well head, the corrosion rate of underground is calculated, so as to understand underground equipment corrosion condition and Corrosion developing Trend.

The corrosion monitoring of Oil/gas Well underground equipment is also available without mature and stable technology in addition to link at present, by Corrosive environment in underground is harsher, and compared with well head environment, becoming of gradually rising is presented in its temperature, pressure and its corrosivity Gesture, for the on-line corrosion monitoring of underground equipment, due to by electronic component heat resistance, and underground oil sets annular space The technical conditions limitation such as narrow and small, it is also difficult to achieve at present, therefore proposes and monitor well head corrosion rate using inductance probe, utilize Well head downhole corrosion speed correlation model, the thinking of downhole corrosion speed is calculated according to well head corrosion rate.

First, the technical scheme used is：

Propose well head downhole corrosion speed correlation model algorithm and monitored on-line using the downhole corrosion speed of this algorithm Method, solve the problems, such as above-mentioned.

By experiment, the relevance model algorithm of research underground different depth corrosion rate and well head corrosion rate, and then Using the Corrosion monitoring result of well head, the corrosion condition for solving the problems, such as underground equipment can not be monitored effectively.

Well head and the relevance model (i.e. algorithm) of downhole corrosion speed are based on C.de Waard (DM models)；With height Containing CO₂Corrosive environment is research object, using six factors, the experiment of five horizontal quadratures, model is carried out using orthogonal experiment data Amendment, well head, the downhole corrosion rate prediction model established respectively.By the temperature of well head and underground, CO₂Partial pressure, stagnation pressure three Crucial corrosion influence factors, temperature parameter is normalized to, determines the functional relation of well head, downhole corrosion speed and temperature respectively, Recycle downhole temperature to be carried out with thermograde empirical equation existing for wellhead temperature for calculation, finally give well head and downhole corrosion The relevance model of speed.

By inductance probe real time on-line monitoring well head corrosion rate, the relevance model of well head downhole corrosion speed is utilized The corrosion rate of underground different depth is calculated, and then understands the corrosion condition of underground equipment.

Inductance probe and the material of lacing film should be consistent with by the material of well logging down-hole string.

Due to CO₂It is complicated to drive underground media environment and velocity flow pattern, has that corrosivity is strong, the feature of high pressure multiphase mixed flow, General corrosion and local corrosion coexist in system.Oil field CO₂Drive corrosion protection and following bottleneck be present：(1) HTHP causes Serious CO₂Corrosion, lacks fast and reliable on-line corrosion monitoring means.(2) well fluids downhole water content is to influence CO₂Displacement is imitated An important factor for rate and corrosion rate, lack corresponding CO₂The monitoring means of the parameters such as partial pressure, water content.(3) various corruption are integrated Monitoring technology, various monitoring informations are lost, carries out comprehensive etch state assessment.

New compensation method is studied to solve heavy wall column inductance probe test piece measured value and former inductance probe mathematical modulo Type curve deviates the problem of linear relationship.

It the advantage is that：

According to statistics, there is 2731 mouthfuls of producing well Bin Nan oil recovery factories, wherein driving a well 2085 mouthfuls, producing well is during production run The problems such as tube corrosion, fracture, eccentric wear, not fuel-displaced producing well occurs, is, it is necessary to carry out stopping production operation maintenance, wherein downhole corrosion Maintenance activity accounts for more than 20% caused by reason.Assuming that annual total operation frequency is 0.9 (the total operation frequency in 2014 Nian Binnan oil recovery factories Secondary is 0.924), to be calculated according to group material and labor service etc. expense caused by well servicing operation is stopped every time for 100,000 yuan, annual operation cost With up to 187,650,000 yuan.Wherein both conservative estimations can reduce by 20% underground equipment maintenance and replacing, then will be shore every year Southern oil recovery factory saves 37,530,000 yuan of fund, has significant economic and social benefit.(the section of direct economic benefit caused by 2016 Branch) be：37530000 yuan/2085 mouthfuls * 2 mouthfuls=3.6 ten thousand yuan.

There are 7.67 hundred million tons of low-permeability oil deposit reserves SHENGLI PETROLEUM AREA at present, accounts for the 15.4% of total resources, since " 95 ", Every year in newly-increased proved reserves, hyposmosis added reserves are all at 20,000,000 tons or so.According to preliminary screening, in Shengli Oil Field, it is adapted to the low permeability oil field reserves of carbon dioxide drive just up to more than 200,000,000 tons, if all using CO₂The displacement of reservoir oil is developed, and can improve oil Field recovery ratio 10%~15%, it is contemplated that 33,000,000 tons to 47,000,000 tons of newly increased recoverable reserves.CO₂Drive in oil recovery process, CO₂Noted After entering underground, it there are about 50%~60% and be forever sealed in underground, remaining 40%~50% returns with associated gas Ground.Carbon dioxide present in crude oil, it can cause to produce well underground equipment heavy corrosion, in high temperature and high pressure environment, due to CO₂To the highly corrosive (7~20mm/a) of carbon steel and the presence of tension, the corrosion failure of down-hole string or early stage can be caused disconnected Split and (fail within most fast 6 months).

Shengli Oil Field only implements CO in overall aqueous low (6%) and stable high 89 block in the correct principle village at present₂Drive guide Experiment.Shengli Oil Field will provide the carbon dioxide air source of 1,500,000 sides every year, realize CO₂Drive technology is in pure beam Niu Zhuan, existing river, orphan The popularization and application of the higher hypotonic block of other moisture content such as east.

This project achievement in research energy on-line monitoring equipment is corroded and corrosion control effect, quickly and accurately judges underground CO₂ Corrosion condition and existing hidden danger, adjustment corrosion inhibiter adding amount is instructed, facility etc. is changed in maintenance, is reduced to greatest extent because of corrosion Caused by loss.To CO₂The security evaluation and Integrity Management of underground equipment and surface gathering system operation are driven, avoids safe thing Therefore have great importance.To be CO₂The extensive use of drive technology solves the bottleneck problem of extraction well underground equipment corrosion, and energy Instruct the defeated corrosion protection along journey of Produced Liquid collection, strong guarantee CO₂Drive downhole hardware and surface gathering system corrosion protection scheme The economy and reliability of operation, there is significant economic and social benefit, there is good popularizing application prospect.

Brief description of the drawings

Fig. 1 is temperature and CO₂Influence of the partial pressure to corrosion rate.

Fig. 2 is inductance probe output data curve legend.

Fig. 3 correspondingly corrodes the lacing film surface microscopic topographic under the conditions of most serious for A3 steel.

Fig. 4 is A3 steel well head lacing films linearity curve consistent with inductance probe data.

Fig. 5 is N80 steel well head lacing films linearity curve consistent with inductance probe data.

Fig. 6 is N80 steel underground lacing film linearity curve consistent with inductance probe data.

Fig. 7 is J55 steel well head lacing films linearity curve consistent with inductance probe data.

Fig. 8 is J55 steel underground lacing film linearity curve consistent with inductance probe data.

Fig. 9 is the fitting result of inductance probe data and lacing film data.

Figure 10 is change curve of the A3 materials corrosion rate with different parameters.

Figure 11 is change curve of the N80 materials corrosion rate with different parameters.

Figure 12 is change curve of the J55 materials corrosion rate with different parameters.

Figure 13 is change curve of the underground N80 materials corrosion rate with different parameters.

Figure 14 is change curve of the underground J55 materials corrosion rate with different parameters.

Figure 15 is technology path 1.

Difference CO when Figure 16 is 20 DEG C₂The pH value of potassium-containing hydrogen salt (saturation or supersaturation) generation water under pressure.

Difference CO when Figure 17 is 60 DEG C₂The pH value of potassium-containing hydrogen salt (saturation or supersaturation) generation water under pressure.

Difference CO when Figure 18 is 100 DEG C₂The pH value of potassium-containing hydrogen salt (saturation or supersaturation) generation water under pressure.

Figure 19 is three kinds of lacing film measured datas.

Relations of the Figure 20 between A3 model predication values and measured value.

Relations (≤45 DEG C) of the Figure 21 between A3 model predication values and measured value.

Relations (＞ 45 DEG C) of the Figure 22 between A3 model predication values and measured value.

Relations (≤45 DEG C) of the Figure 23 between model predication value and N80 well head measured values.

Relations (＞ 45 DEG C) of the Figure 24 between model predication value and N80 well head measured values.

Relations (≤45 DEG C) of the Figure 25 between model predication value and J55 well head measured values.

Relations (＞ 45 DEG C) of the Figure 26 between model predication value and J55 well head measured values.

(≤45 DEG C of relations of the Figure 27 between model predication value and N80 undergrounds measured value.

Relations (＞ 45 DEG C) of the Figure 28 between model predication value and N80 undergrounds measured value.

Relations (≤45 DEG C) of the Figure 29 between model predication value and J55 undergrounds measured value.

Relations (＞ 45 DEG C) of the Figure 30 between model predication value and J55 undergrounds measured value.

Figure 31 is the relation curve of downhole corrosion speed and downhole temperature.

Figure 32 is wellhead temperature and the relation curve of well head corrosion rate.

Figure 33 tests for 1# wells inside authentication.

Figure 34 is 1# well A3 steel incipient stability sections scene inductance probe data.

Figure 35 is 1# test well well head A3 inductance probe Monitoring Datas.

Figure 36 is No. 1 test well well head N80 inductance probe Monitoring Data figure.

Figure 37 is iron ion content and the corresponding relation of corrosion rate.

Figure 38 is a kind of structural representation for the inductance probe that can be used in the technical program.

Figure 39 is 4-11x101 scenes link scheme of installation.

Figure 40 is 2# test well A3 material inductance probe Monitoring Datas.

Figure 41 is iron ion content and the corresponding relation of inductance probe corrosion rate.

Figure 42 is No. 2 test well N80 material inductance probe Monitoring Datas.

Figure 43 is comparison diagram before and after used inductance probe mathematical modeling compensation.

Figure 44 is 1# well corrosion rate maximums.

Figure 45 is 2# well corrosion rate maximums.

Figure 46 is 3# well corrosion rate maximums.

Embodiment

Embodiment 1.

(1) well head downhole corrosion speed correlation model algorithm and the downhole corrosion speed on-line monitoring side using this algorithm Method.

(2) CO₂Drive corrosion regularity research：

1. the steel material of corrosion test：

Inductance probe and the material of lacing film are the general steel of oil field tubing and casing in corrosion experiment, including J55, N80 and A3 Steel.Each steel chemical constituent is analyzed as follows：

The chemical constituent of A3 steel is as shown in table 2-1 in experiment：

The chemical constituent (%) of table 2-1 experiment A3 steel

The chemical constituent of N80 steel is as shown in table 2-2 used in experiment：

The chemical constituent (%) of table 2-2 experiment N80 steel

The chemical constituent of J55 steel is as shown in table 2-3 used in experiment：

The chemical constituent (%) of table 2-3 experiment J55 steel

2. experiment reagent.

Calcium chloride, sodium carbonate, sodium acid carbonate, potassium chloride, magnesium chloride, absolute ethyl alcohol, concentrated hydrochloric acid, hexamethylenetetramine, steaming Distilled water and diesel oil.

Simulated produced fluids can use several configurations in above reagent to form.

According to the ion salinity scope 7500-75000mg/L of live Produced Liquid, solution is voluntarily configured, this is this area Known technology, various ion concentrations such as following table, unit are (mol/L).

The simulated produced fluids composition voluntarily configured is as shown in Table 2-4：

Ion concentration table (mol/L) corresponding to table 2-4 difference salinities

3. experimental program.

In view of six kinds of corrosion influence factors are included herein：Temperature, flow velocity, salinity, water content, CO₂Partial pressure, stagnation pressure, such as Fruit is all cooked experiment of single factor to every kind of factor, does not as a result have very big actual utility and reference value.So herein from just Test method is handed over to carry out conceptual design, because orthogonal test has the characteristics of neat comparable, dispersed, and can be to result Recurrence processing is carried out, and makes erosion model result that more there is convincingness.

(1) setting of temperature conditionss.

According to current present situation, wellhead temperature range intervals are 20-80 DEG C, and it is that well depth often declines that downhole temperature, which rises rule, 100 meters, temperature raises 3.5-4 DEG C, most of to level off to 3.5 DEG C after consulting pertinent literature, therefore temperature is according to 3.5 DEG C of progress Calculate, if with 2200 meters of well depth for depth capacity, the temperature of this depth is 97 DEG C.The temperature recorded as shown in Figure 1 for document Degree and CO₂Influence result of study of the partial pressure to corrosion rate, it is seen then that its temperature breakthrough is at 100 degree.Fig. 1 temperature and CO₂Partial pressure Influence to corrosion rate.

Influence of the Temperature Distribution of foundation case above, comprehensive well head and underground to corrosion rate, the parameter setting of temperature Scope is as shown in table 2-5.

The setting range of table 2-5 well heads and underground experimental temperature

Node	1	2	3	4	5
						Temperature/DEG C	35	45	60	85	105
About well depth/m	0	600	1200	1800	2400

(2) stagnation pressure and CO are tested₂Partial pressure is set.

According to the oil well of different output, its CO₂The scope of partial pressure is not quite similar, therefore in order that experimental result has generally Applicable effect, the depth bounds selected according to temperature, bibliography set experiment pressure on the measure numerical value of oil well stream pressure Power scope, as shown in table 2-6.

Table 2-6 down-hole simulations test stagnation pressure setting range

Node	1	2	3	4	5
						Stagnation pressure/MPa	0.5	2	6	11	14
About well depth/m	0	600	1200	1800	2400

From CO₂Partial pressure is analyzed, and generally, partial pressure is less than 0.483 × 10⁵During Pa, homogeneous corrosion easily occurs；When point It is pressed in 0.483 × 10⁵~2.07 × 10⁵Different degrees of pitting corrosion may occur between Pa；When partial pressure be more than 2.07 × 10⁵During Pa, serious local corrosion occurs.

CO₂Nobody is detailed so far probed into for partial pressure measure；And due to CO₂Critical-temperature and pressure all than relatively low Respectively 304k and 7.52Mpa, supercritical fluid is converted to greatly at underground 1000 meters (temperature is substantially in 333k or so), CO₂Partial pressure is to CO₂Solubility in water does not have obvious scale effect yet, so only by CO₂Partial pressure get critical pressure Power, it is enough to inquire into CO in this pressure limit₂Influence of the partial pressure to corrosion.Secondly, selected node have also contemplated that in document and carry The partial pressure value of the bright different etch states of generation, node are selected as shown in table 1-7.

Table 2-7 down-hole simulations test CO₂Partial pressure parameter setting

Node	1	2	3	4	5
						Partial pressure/MPa	0.04	0.2	4.5	6	7.5

According to the actual condition of oil well, the pressure of well head is substantially in 1Mpa or so, therefore the stagnation pressure of well head simulated experiment was both Select in 1Mpa, and CO₂The parameter of partial pressure is then carried out according to the influence nodal value of different mol ratio and partial pressure to etch state Selection, specifically as shown in Table 2-8.

Table 2-8 well head simulated experiments CO₂Partial pressure parameter setting

Node	1	2	3	4	5
						Partial pressure/MPa	0.04	0.1	0.2	0.4	0.6

(3) flow velocity selects.

When flow velocity is relatively low, corrosion rate will accelerate with the increase of flow velocity；When flow velocity is higher, corrosion rate is complete Controlled by charge transfer, now, the change of flow velocity is inessential, and the influence of temperature becomes major influence factors.Therefore test The flow velocity of scheme is in low flow velocity section.

According to prior understanding, the movement velocity scope of sucker rod is about 1-3 beats/min, and stroke is about 5-8 rice around here.Press Section is calculated like this, and the most fast movement velocity of sucker rod is set as 3 beats/min, and stroke is 8 meters, and it is calculated with this Movement velocity=6*8/60=0.8m/s.Most slow speed=2*5/60=0.17m/s, according to this actual conditions, the flow velocity of selection Scope is as shown in following table 2-9：

Table 2-9 well heads and underground flow parameters scope

Node	1	2	3	4	5
						Flow velocity	0.1	0.3	0.6	0.9	1.1

(4) water content parameter setting.

In Produced Liquid system, if forming Water-In-Oil (water/oil) emulsion, the water of steel will be prevented or substantially reduced Wetability, so as to reduce corrosion rate；If on the contrary, forming oil-in-water (oil/water) emulsion, obvious water wetting occurs and makees With.In many oil pipes, the transformation from water/fat liquor to oil/water emulsion occurs in w (H₂O it is) 30%~40%, according to warp Test, as w (H₂O) when being 30%, corrosion rate Chang Mingxian is reduced but is also had an exception.The water content ranges to sum up selected such as following table 2- Shown in 10：

Table 2-10 well heads and underground water content parameter area

Node	1	2	3	4	5
						Water content	0	15	35	60	90

Result obtained by such selection can either confirm current conclusion, and and can realizes that the field is not reaching at present Target.

(5) selection of salinity.

The analysis data of three oil recovery factories provided according to Shengli Oil Field, salinity scope minimum 9045, up to 69369, scope is very wide in range.In order to improve the broad applicability of experimental result, salinity scope covers the scope of the above, ginseng Number selection is as shown in following table 2-11.

Table 2-11 well heads and underground experiment salinity parameter area

Node	1	2	3	4	5
						Salinity	7500	15000	30000	50000	75000

Herein for A3, tri- kinds of steel of J55, N80 need to establish three groups of orthogonal schemes：

A3 well head low-pressure orthogonal test schemes, five kinds of factors, five levels of selection, refer to table 2-12, stagnation pressure 1Mpa.

Factor, water-glass corresponding to table 2-12 A3 orthogonal tests

N80, J55 low pressure orthogonal test scheme, five kinds of factors, five levels of selection, refer to table 2-13, stagnation pressure is 1Mpa。

Factor, water-glass corresponding to table 2-13 N80, J55 low pressure orthogonal tests

N80, J55 down-hole high pressure orthogonal test scheme, from six kinds of factors, five levels, table 2-14 is referred to, because N80, J55 is applied to tube and casing in downhole.Pressure becomes big with the increasing of well depth.

Factor, water-glass corresponding to table 2-14 N80, J55 high pressure orthogonal tests

Experimental procedure：

The first step, by reactor good seal, the air-tightness of verifying attachment.

Second step, the preparation of drug solution, from CaCl₂, MgCl₂, anhydrous Na₂CO₃, NaHCO₃, KCl, five kinds of medicines enter The preparation of row simulated produced fluids, experiment the previous day have configured stand-by.This is the known technology of this area, therefore not repeated description.

3rd step, the pre-treatment of corrosion coupon, lacing film is taken out from the package, after being wiped with absolute ethyl alcohol, blown with air duct It is dry, and be put into stand-by in drying receptacle.Piece suspension device and accessory are got out, lacing film is installed stand-by.

4th step, solution is fitted into reactor according to experiment setting value (1L), and starts heater, temperature is raised to Above predetermined temperature in table.

5th step, inductance probe and lacing film are connected with reactor, are filled with nitrogen first to setting value, are re-filled with CO₂ To steady pressure, nitrogen pressure and CO₂Pressure reaches the stagnation pressure in above table.

6th step, inductance probe collector is connected, log-on data software, starts to communicate.

7th step, observed data read situation and pressure changing, are finely adjusted and syndrome check.

8th step, after experiment maintains 2-4 days, inductance probe data and curves are intercepted, lacing film is taken out into reactor.

The processing of 9th step, inductance probe and lacing film, the corrosion product on inductance probe and lacing film surface is taken out with cleaning agent, Weighed after drying, record data, wait follow-up calculate.

Tenth step, solution in reactor is extracted out with water pump, recycled.

11st step, analyze data, calculate single group corrosion rate.

12nd step, single group laboratory report is write, by photo before and after reaction, inductance probe corrosion data, lacing film corrosion number According to being analyzed.

Corrosion rate calculates method.

(1) weight loss method.

Weight-loss method is that most common corrosion rate calculates method in laboratory corrosion research, also most directly perceived, maximally effective equal Even corrosion measurement method.Hanging slice method step is also very simple, handles lacing film well before experiment, and drying is stand-by, with a ten thousandth balance Weigh and record.After experiment, lacing film is handled with cleaning agent, after the corrosion product on surface is removed totally, drying is weighed.

Its principle can be represented with this following equation：

M --- the weight before lacing film corrosion, g；

m_t--- the weight after lacing film corrosion, g；

S₁--- the surface area of lacing film, m²；

The time of t --- corrosion experiment, h；

The density of ρ --- Experiment Metal, g/cm.

(2) inductance probe monitoring method.

Inductance probe is a kind of means of indirect method measurement corrosion rate of rising in recent years, and advantage is can be right in real time The corrosivity of medium is detected, and electric signal caused by corrosion is converted into data signal by data communication software, and reflect The speed variation tendency of whole corrosion process.Pass through inductance probe work station, additionally it is possible to obtain the corrosion rate of random time section Value, is contrasted, and find out relation between the two with the corrosion rate gone out of weight loss.As shown in Fig. 2 red curve generation Table corrosion tendency, ordinate represent inductance probe test piece residual thickness, and abscissa represents the time, are intercepted with purple and blue vertical line Any one section of corrosion tendency line can be obtained by the corrosion rate of this period of time.Fig. 2 inductance probe output data curve legends.

Experimental result.By observation, A3 lacing films, N80 lacing films and J55 lacing films in well head and underground have different degrees of Corrosion.Inductance probe also has situation about being corroded.Fig. 3 correspondingly corrodes the lacing film surface microscopic shape under the conditions of most serious for A3 steel Looks.

From the lacing film and inductance probe surface topography after well head and underground experiment, homogeneous corrosion is belonged to, is had light The local corrosion patterns such as microdot erosion.

Corrosion rate monitoring result.

A3 corrosion Orthogonal experiment results under well head condition (stagnation pressure 1Mpa) see the table below shown in 2-15：

Table 2-15 A3 orthogonal experiment group numbers and experimental result

As can be seen from the above table, inductance probe and the data of lacing film have differences, and the relative average error of the two is 17.9%.

N80 corrosion Orthogonal experiment results under well head condition (stagnation pressure 1Mpa) see the table below shown in 2-16：

Table 2-16 well head N80 orthogonal experiment group numbers and experimental result

As can be seen from the above table, inductance probe and the data of lacing film have differences, and the relative average error of the two is 18.1%.

The N80 corrosion Orthogonal experiment results of down-hole high pressure condition (stagnation pressure 1Mpa) see the table below shown in 2-17：

Table 2-17 shaft bottoms N80 orthogonal experiment group numbers and experimental result

As can be seen from the above table, inductance probe and the data of lacing film have differences, and the relative average error of the two is 18.4%.

J55 corrosion Orthogonal experiment results under well head condition (stagnation pressure 1Mpa) see the table below shown in 2-18：

Table 2-18 well head J55 orthogonal experiment group numbers and experimental result

As can be seen from the above table, inductance probe and the data of lacing film have differences, and the relative average error of the two is 18.7%.

The J55 corrosion Orthogonal experiment results of down-hole high pressure condition see the table below shown in 2-19：

Table 2-19 shaft bottoms J55 orthogonal experiment group numbers and experimental result

As can be seen from the above table, inductance probe and the data of lacing film have differences, and the relative average error of the two is 18.0%.

Data analysis.

Corrosion coupon and the correlation research of inductance probe Monitoring Data.

As can be seen that inductance probe and lacing film number from all 125 groups shown in table 2-15 to table 2-19 of experimental data According to having differences, therefore the data of corrosion coupon and inductance probe are carried out with qualitative and quantitative relation research.It is A3 to see Fig. 4 Steel well head lacing film linearity curve consistent with inductance probe data.Fig. 5 is the uniformity of N80 steel well head lacing films and inductance probe data Curve.Fig. 6 is N80 steel underground lacing film linearity curve consistent with inductance probe data.Fig. 7 is that J55 steel well head lacing films and inductance are visited The consistent linearity curve of pin data.Fig. 8 is J55 steel underground lacing film linearity curve consistent with inductance probe data.

Pass through the above-mentioned analysis to tri- kinds of materials of A3, N80, J55, it can be seen that have between inductance probe and lacing film latent Uniformity.It is therefore desirable to further inquire into both quantitative function relations.

In terms of the analysis of data, SPSS softwares have a wide range of applications.So the lacing film drawn and inductance spy will be tested Pin data are brought into mathematical software.Import 100 groups of experimental datas in addition to well head J55 data, the data conduct of J55 well heads Verify that data use.Process is as follows：1. importing data, it is fitted.2. a variety of curve matchings.

By data with linear, quadratic term, it is compound, cube, the functional form such as index, power function, log is fitted and excellent Choosing, as a result as shown in Figure 9：(orange curve is polynomial fitting curve to the fitting result of inductance probe data and lacing film data, black Color is linear fit curve, substantially with orange curve co-insides).

After the fitting to 100 groups of inductance probes and lacing film data, preferably go out two kinds of fitting results, as shown in Figure 9.Can See two kinds of fitting results, both the two had two kinds of fit correlations of phenomenon and multinomial.

The measured data that J55 well heads are monitored, compare with the result after being calculated using above fit correlation, on the one hand test Whether accurate demonstrate,prove fit correlation, contrast that fit correlation in addition, closer to measured value.

The contrast of table 2-20 fitting results and measured value

From above-mentioned comparing result, the result of linear fit closer to inductance probe measured value, its match value with The average relative error of inductance probe measured value is 0.7%, and fitting of a polynomial result and the average relative error of measured value are 4.4%, therefore it is as follows to illustrate that inductance probe measured value with lacing film measured value has linear relationship：

Y=1.1877X-0.0013

Y is the corrosion rate of inductance probe monitoring in above formula, and X is the corrosion rate of lacing film monitoring, is closed with superior function System is the correction model of inductance probe.

Well head inductance probe corrosion data is gathered, lacing film corrosion data should be gathered simultaneously during application for the first time, for inductance Probe monitors the amendment of corrosion rate value.

There are certain restraining factors in the measuring method of lacing film and inductance probe, but lacing film number on data accuracy According to being internationally recognized corrosion rate measuring method, therefore actual corrosion rate needs to be defined by lacing film measurement data.Pass through In the functional relation for analyzing the lacing film data and inductance probe data found above, it can be seen that the two exists extraordinary Corresponding relation.Therefore, the correction model of inductance probe measurement data is so far completed.

The purpose for carrying out the corrosion influence factors research of well head and underground has at following 2 points：

Investigate well head and subsurface environment, influence of each influence factor to corrosion rate.

(1) the orthogonal mean analysis result of well head A3/N80/J55 steel：See Figure 10 for A3 material corrosion rates with different parameters Change curve.

Pass through Figure 10, it can be determined that temperature be 105 DEG C, CO₂Partial pressure pressure is 0.1Mpa, flow velocity 0.1m/s, aqueous Measure as 90%, salinity is corroded the most serious in the case of being 50000mg/L.

This combination is not in orthogonal test, and in order to verify the correctness of orthogonal test analysis result, spy is to corroding the combination Verification experimental verification is carried out, the lacing film corrosion rate drawn is the 23rd group in 6.542mm/a, with orthogonal test and is in same corrosion The reason for level, both difference are the difference of flow velocity, but result is close is that in the case of a high temperature, corrosion product adhesion is good, It is smaller by flow rate effect.

The influence size order of each factor is from the point of view of the result of average：Water content (extreme difference K1=2.40)>Temperature (k3 =1.2)>Salinity (K4=1.1)>Flow velocity (k5=1.0)>CO₂Partial pressure (k2=0.9), it is seen that it is maximum to corrosion impact because Element is water content, minimum for CO₂Partial pressure.

It is change curve of the N80 materials corrosion rate with different parameters to see Figure 11, and Figure 12 is J55 material corrosion rates with not The change curve of same parameter.

According to Figure 11 and Figure 12, it can be seen that two kinds of materials are 60 DEG C in temperature, CO₂Partial pressure is 0.6MPa, salinity For 15000mg/L, profit corrodes the most serious in the case of 90%.Two kinds of materials difference wherein above flow velocity, still Difference is simultaneously little, and influence of the flow velocity to corrosion rate is not very big, and corrosion rate is substantially all to fluctuate in 1mm/a.For The quality of the screening operation of corrosion inhibiter after ensureing, considers when selection in J55 orthogonal tests maximum corrosion rate occurs pair The flow velocity 0.6m/s answered.The influence size order of each factor is from the point of view of the result of average：Water content (extreme difference K1=2.55)> CO₂Partial pressure (k2=1.725)>Temperature (k3=1.52)>Salinity (K4=1.335)>Flow velocity (k5=0.825).

(2) the orthogonal mean analysis result of underground N80/J55 steel：See Figure 13 for underground N80 materials corrosion rate with different ginsengs Several change curves.Figure 14 is change curve of the underground J55 materials corrosion rate with different parameters.

According to Figure 13, it can be seen that two kinds of materials are 45 DEG C in temperature, CO₂Partial pressure is 6.0MPa, and salinity is 50000mg/L, profit are 90%, and stagnation pressure corrodes the most serious in the case of being 6MPa.In terms of flow velocity, above two kinds of materials Difference, but difference and little.Because influence of the flow velocity to corrosion rate is not very big, corrosion rate is substantially all 5mm/a fluctuates, and for the quality of the screening operation of corrosion inhibiter after ensureing, considers that selection occurs in J55 orthogonal tests Corresponding flow velocity 0.6m/s during maximum corrosion rate.The influence size order of each factor is from the point of view of the result of average：

N80：Water content (extreme difference K1=10.342)>Temperature (k2=6.213)>Stagnation pressure (k3=5.397)>CO₂Partial pressure (k4 =4.67)>Flow velocity (k5=3.216)>Salinity (K6=2.134).

J55：Water content (extreme difference K1=10.135)>Temperature (k2=5.915)>Stagnation pressure (k3=5.285)>CO₂Partial pressure (k4 =4.42)>Flow velocity (k5=3.025)>Salinity (K6=2.035).

Factor to affect extreme value corresponding to the extreme difference analyzed more than (water content 90%, temperature 45 C, stagnation pressure 6MPa, CO₂Partial pressure 6MPa, salinity 50000mg/L) carry out one group of zero-G test, the results showed that the lacing film of N80 materials, on this condition Weight-loss corrosion speed be 20.3412mm/a.

In order to verify the combinations of values of each influence factor corresponding to corrosion rate maximum that range analysis goes out, if be not With Parameter Conditions corresponding to corrosion rate maximum under hole condition.Therefore following checking test is done.

Each factor chooses at 3 points.

Table 2-21 undergrounds N80 material stagnation pressure checking tests

By above checking test, i.e., in the case that other conditions are constant, change stagnation pressure numerical value, it is seen then that its corrosion rate Changed, further illustrate that stagnation pressure in the presence of necessarily influenceing, there is part literature research stagnation pressure pair to downhole corrosion speed Corrosion rate is as can be seen from the above results, really influential without influence.

Table 2-22 undergrounds N80 temperature checking tests

The selection of checking test point, it is the extreme point that the corrosion rate maximum gone out in extreme value analysis occurs, such as temperature 45 Degree nearby chooses 2 points, respectively 40 and 55 degree.

Table 2-23 undergrounds N80 material flow velocity checking tests

Table 2-24 undergrounds N80 material salinity checking tests

Table 2-25 undergrounds N80 material water content checking tests

Table 2-26 undergrounds N80 material CO2 partial pressure checking tests

The corrosion rate (20.3412mm/a) for the most harsh experiment that above all of checking data and extreme difference determine is carried out pair Than, it is seen then that checking numerical value is respectively less than 20.3412mm/a, thus may determine that the experimental condition that single factor test is combined, is most harsh Experimental condition.

Because medium is in a manner of turbine stirring in reactor, therefore effect of the medium to inductance probe and lacing film is oblique To shearing force, and effect of the live Produced Liquid to tubing and casing is vertical shearing force, in order to investigate this fluidised form Difference whether the measurement result of corrosion rate can be had an impact, spy using dynamic simulation experimental device to experimental result carry out Checking.

Choice experiment group number：Underground N80 materials, the 25th group of (105 degree, flow velocity 1.1m/s of temperature, 6 MPas of partial pressure, salinity 30000,14 MPas of stagnation pressure, water content 15).

Influence checking test of the table 2-27 fluidised forms to corrosion rate

From experimental result as can be seen that fluidised form has certain influence on corrosion rate result, but influence simultaneously unobvious.

J55 with N80 experiment conclusions are consistent.

1) range analysis corrosion factor weighing factor order is：Oil-water ratio>Temperature>Stagnation pressure>CO₂Partial pressure>Flow velocity>Mineralising Degree.2) material corrosion most serious condition：Temperature 45 C, salinity 50000mg/L, water-oil factor 90%, stagnation pressure 6MPa, CO₂Partial pressure Saturation.

Embodiment 2, well head associate Journal of Sex Research with downhole corrosion speed：

Intend due to the foregoing testing experiment for having carried out substantial amounts of downhole corrosion rate, therefore for the corrosion condition prediction of underground Its technology advantage and disadvantage is determined using two technology paths, and eventually through laboratory and on-site verification.

Technology path 1：Figure 15 passes through to existing CO₂The screening and amendment of forecast model, directly carry out well head and underground is rotten The prediction of speed is lost, if can be associated by a certain corrosion influence factors, such as the foundation such as salinity, then research purpose reaches Into, if can not associate, also can directly apply corrosion influence factors related data, to corrosion directly predicted.

Technology path 2：Evade influence of all kinds of influence factors to downhole corrosion speed, it is directly different deep by test measurement The downhole corrosion speed of degree, data correlation is directly carried out using downhole corrosion speed, well head corrosion rate, and depth, establishes well The relation of mouth corrosion rate and downhole corrosion speed.

Technology path 1：

Model discrimination：

Erosion model is exactly substantially the complex relationship formula formed by various parameters, has been selected most normal in current world wide Three kinds of models carry out this item purpose modeling work, strive for being improved on the basis of existing model, obtain one more Erosion model with practicality.

1. the Norsok M506 models of Norway are that have the empirical model for representing meaning at present, the model is according to low temperature The empirical model that test data and high temperature field data are established, this model at home and abroad anti-CO₂Corrode selection and determination One major criterion of corrosion allowance design, but its shortcoming is not account for the aqueous influence to crude oil system corrosion rate. So for the research work of this item purpose and do not apply to.

2. at present, ripe forecast model is mostly semiempirical model, the DMW models that De Warrd and Miliiams are established Have become prediction CO₂The basis of corrosion.De Warrd2003 have studied crude oil ratio according to the interfacial tension between oil-water-pipe Weight and influence of the moisture content to corrosion rate, the predictor formula for considering the crude oil factor is drawn.

3.S.Nesic models are mainly from CO₂The microcosmic mechanism of corrosion is set out, the chemistry on bond material surface, electrochemistry Reaction, mass transport process of the ion at material and solution interface, and ion spreads in corrosion products film and transition process etc. The forecast model of foundation.But because mechanism model is still mainly stuck in the research work in laboratory, it is not preferable Combine with the corrosion data of on-the-spot test, and the also less corrosion condition considered in the case of oil mixing with water.

De.warrd model introductions：

In the most widely used CO in corrosion research field of industrial gas oil₂Erosion model is De.Waard models. In recent study, the scene corrosion number for two kinds of different API degree crude oil that scale-model investigation personnel accumulate between have chosen 20 years According to and relevant parameter, including flow velocity (being obtained by calculation of yield), caliber, CO₂Partial pressure and the HCO for producing water sample_2-Concentration, Angle of deviation of water content, oil well well casing and vertical direction etc..Corrosion thinning amount is to come from account on the spot to measure by micrometer Data mean value.

Erosion model newest C.de Waard considers influence of the crude oil to corrosion, it is seen that the influence that the model includes because The influence factor of element and this paper studies, which has, preferably coincide.At the same time, Waard models are applied to without addition corrosion inhibiter Oil well, the Corrosion results of this experiment are also to be obtained in the case where no corrosion inhibiter adds.In summary, C.de Waard It is more conform with this item purpose research application.

But De.Waard models are primarily directed to CO₂Partial pressure is less than 1MPa condition, so if wanting to realize it at this Application in research, it is necessary to which being modified to it to apply.In order to preferably react the CO under many factors effect₂Corrosion rule Rule, the erosion model of this paper will be based on C.de Waard models, for the specified conditions of this paper studies, according to data As a result carry out returning processing and analysis, and further obtain suitable erosion model.

De.Waard models are formed substantially：

The calculation formula of C.de Waard models is：

Vr and Vm represents maximum power reaction rate and CO respectively₂Influence of the mass transport process to corrosion.Vr and Vm meter It is as follows to calculate formula：

Log(V_r)=5.07-+0.58log (P_CO2)–0.34(pH_a–pH_CO2) 2-3

P_CO2It is the CO containing fugacity coefficient₂Partial pressure, unit MPa；PHa is the PH values under actual condition；pH_CO2For Identical CO₂The pH value of pure water under partial pressure；T represents temperature, and unit is DEG C；Uliq is flow velocity, unit m/s；D is the interior of pipe Footpath, unit m.

When considering the influence of pH value, temperature will influence CO₂Solubility and H₂CO₃Ionization number.

pH_CO2=3.82+0.00384T -0.5log (P_CO2) 2-5

Under normal circumstances, the pH value of medium can be derived by measuring, but the pH of medium is difficult to direct measurement at high temperature under high pressure, So can determine its pH value according to international standard ISO15156-2 for HTHP system to replace pHa, method is shown in figure 16-Figure 17：

1：Ca²⁺=1000meq/L, 2：Ca²⁺=100meq/L, 3：Ca²⁺=10meq/L, 4：HCO_2-=10meq/L, 5： HCO_2-=30meq/L, 6：HCO_2-=100meq/L.

-------Ca²⁺<HCO_2-__________Ca²⁺<HCO_2-———Ca²⁺<HCO_2-。

-------Ca²⁺<HCO_2---------Ca²⁺<HCO_2-———Ca²⁺<HCO₃。

-------Ca²⁺<HCO_2-______Ca²⁺<HCO_2-———Ca²⁺<HCO₃。

(2) the corrosion prediction scale-model investigation of unlike material.

The model filtered out above, be for A3 steel low pressure range (pressure is less than 2MPa) under the conditions of set, in order to The corrosion rate forecast model of unlike material, well head low-pressure and down-hole high pressure is studied, studies the corrosion rate of unlike material first Changing rule under same test conditions.Under the conditions of well head low-pressure, the relation of N80, J55 and A3 corrosion rate：See that Figure 19 is Three kinds of lacing film measured datas.

It can be seen that under the same test conditions from the corrosion rate curve of three of the above material, the change of corrosion rate Change has uniformity, but the corrosion rate that the 23rd group of data can be seen that A3 steel is more abnormal, therefore removes this group in subsequent analysis Data.

The predicted condition of forecast model is for A3 steel corrosions, for its corrosion rate of N80 and J55 materials with corrosion bar The changing rule of part is consistent with A3 steel, therefore N80 and J55 corrosion rate is predicted, can use for reference the erosion model of A3 steel, is led to The method for crossing data fitting finds rule.The identical property between forecast model and A3 steel measured values is determined first.

The contrast table of table 2-28 model predication values and A3 steel measured values

Sequence number	Model predication value	A3 steel measured values	Relative error
				1	0.006320151	0.0024	62.0%
2	0.010847183	0.1035	89.5%
				3	0.022802008	0.2281	90.0%
4	0.035261281	0.6331	94.4%
				5	0.016800128	0.8454	98.0%
6	0.009610199	0.4584	97.9%
				7	0.017350934	1.2151	98.6%
8	0.028888421	0.0286	1.0%
				9	0.035569233	0.1887	81.2%
10	0.007656713	0.5274	98.5%
				11	0.041010214	0.4581	91.0%
12	0.036011797	0.8784	95.9%
				13	0.121311899	3.3863	96.4%
14	0.027021614	4.998	99.5%
				15	0.042063636	0.126	66.6%
16	0.062622185	2.8714	97.8%
				17	0.093174043	0.3592	74.1%
18	0.022875856	0.4151	94.5%
				19	0.055099124	2.1599	97.4%
20	0.078093413	2.1012	96.3%
				21	0.124389274	2.6407	95.3%
22	0.051303856	0.4073	87.4%
				24	0.079132633	0.0365	59.1%
25	0.154521112	0.5154	70.0%

It is very big that the error of model predication value and measured value is can be seen that from the result of upper table, because currently without examining The especially complete CO of worry factor₂Forecast model, the model of use is mainly for the relatively low oil well of water content, it is contemplated that temperature, CO₂ The influence of partial pressure and flow velocity to corrosion rate, and this item purpose research is, salinity high oil well high for moisture content, synthesis is examined Temperature, stagnation pressure, CO are considered₂The influence of partial pressure, flow velocity, water content, salinity to corrosion rate, therefore error is inevitable greatly.

By the A3 steel data of actual measurement, the methods of by data process of fitting treatment, the pass between actual value and predicted value is determined Connection relation, so as to obtain forecast model of the A3 steel under the conditions of well head low-pressure.

25 groups of predicted value is directly fitted with measured value first, preference curve result is as shown in figure 20：A3 models Relation between predicted value and measured value.

(1) when temperature≤45 DEG C：See relations (≤45 DEG C) of the Figure 21 between A3 model predication values and measured value.

(2) when 45 DEG C of temperature ＞：See relations (＞ 45 DEG C) of the Figure 22 between A3 model predication values and measured value.It is logical The relative error of match value and A3 steel measured values after over-fitting is as shown in following table 2-29：

The contrast (≤45 DEG C) of corrosion rate and measured value after the fitting of table 2-29 A3 steel

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.0024	0.0025	4.0%
2	0.4025	0.4011	0.3%
				3	2.5679	2.56	0.3%
4	0.6331	0.6331	0.0%
				5	0.8454	0.8468	0.2%
6	0.4584	0.4597	0.3%
				7	1.2151	1.2056	0.8%
8	0.1887	0.1897	0.5%
				9	0.5274	0.5199	1.4%
Mean error			0.9%

The contrast (45 DEG C of ＞) of corrosion rate and measured value after the fitting of table 2-30 A3 steel

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.4581	0.4878	6.1%
2	3.3863	3.3861	0.2%
				3	0.3592	0.359	0.1%
4	0.4151	0.4141	0.2%
				5	2.6407	2.6400	0.0%
6	0.0365	0.0397	8.1%
				7	0.5154	0.5149	0.1%
Mean error			2.11%

In the case that the contrast of above match value and measured value can be seen that less than or equal to 45 DEG C, average relative error For 0.9%, in the case of 45 DEG C, average relative error 2.11%, it is seen that the goodness of fit of fitting result and true value is higher.

For well head and underground N80 and J55 forecast model：

Data fitting method is directly used first, for the original predictive result of A3 steel, if data be present with N80 and J55 Incidence relation.

If above incidence relation is not present, the corrosion rate of A3 steel actual measurement is further analyzed, is surveyed with N80 and J55 Association between corrosion rate, then by the revised forecast model of A3 steel, obtain N80 and J55 forecast model.

With reference to the model value of A3 steel and the fit correlation of measured value, following N80 and J55 fitting result are obtained.

Fit correlation between well head model predication value and N80 measured values is as follows：

During temperature≤45 DEG C：See relations (≤45 DEG C) of the Figure 23 between model predication value and N80 well head measured values.

During 45 DEG C of temperature ＞：See relations (＞ 45 DEG C) of the Figure 24 between model predication value and N80 well head measured values.

The contrast (≤45 DEG C) of corrosion rate and measured value after the fitting of table 2-31 N80 well heads

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.00771	0.00773	0.3%
2	0.24865	0.24877	0.0%
				3	1.8899	1.899	0.5%
4	3.2614	3.2712	0.3%
				5	4.618	4.6234	0.1%
6	4.2439	4.25	0.1%
				7	2.7789	2.7877	0.3%
8	0.2378	0.2398	0.8%
				9	0.23148	0.2389	3.1%
Mean error			0.6%

The contrast (45 DEG C of ＞) of corrosion rate and measured value after the fitting of table 2-32 N80 steel well head

Eliminate outside some abnormal datas, it is seen that the relative error of N80 match values and well head measured value be respectively 0.6% and 0.5%, data coincidence is preferable.Fit correlation between well head model predication value and J55 measured values is as follows：

Temperature≤45 DEG C：Relations (≤45 DEG C) of the Figure 25 between model predication value and J55 well head measured values.

45 DEG C of temperature ＞：See relations (＞ 45 DEG C) of the Figure 26 between model predication value and J55 well head measured values.

The contrast (≤45 DEG C) of corrosion rate and measured value after the fitting of table 2-33 J55 well heads

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.93826	0.9401	0.2%
2	1.9458	1.9465	0.0%
				3	1.3935	1.3942	0.1%
4	1.7734	1.3987	21.1%
				5	3.7925	3.6785	3.0%
6	2.098	2.099	0.0%
				7	0.1795	0.183	1.9%
8	0.58721	0.6077	3.4%
				Mean error			3.7%

The contrast (45 DEG C of ＞) of corrosion rate and measured value after the fitting of table 2-34 J55 steel well head

Eliminate outside some abnormal datas, it is seen that the relative error of J55 match values and well head measured value be respectively 3.7% and 1.0%, data coincidence is preferable.

Fit correlation between underground model predication value and N80 measured values is as follows：

(1) temperature≤45 DEG C：Relations (≤45 DEG C) of the Figure 27 between model predication value and N80 undergrounds measured value.

(2) 45 DEG C of temperature ＞：Relations (＞ 45 DEG C) of the Figure 28 between model predication value and N80 undergrounds measured value.

The contrast (≤45 DEG C) of corrosion rate and measured value after the fitting of table 2-35 N80 undergrounds

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.00114	0.0011	3.5%
2	3.34273	3.789	11.8%
				3	9.81846	7.5098	23.5%
4	11.08	11.1145	0.3%
				5	4.91793	4.897	0.4%
6	16.22929	16.1986	0.2%
				7	11.6774	11.6779	0.0%
8	2.3304	2.4567	5.1%
				Mean error			5.6%

The contrast (45 DEG C of ＞) of corrosion rate and measured value after the fitting of table 2-36 N80 steel underground

Eliminating outside some abnormal datas, it is seen that the relative error of N80 match values and measured value is respectively 5.6% and 6.3%, Data coincidence is preferable.

Fit correlation between underground model predication value and J55 measured values is as follows：

Temperature≤45 DEG C：Relations (≤45 DEG C) of the Figure 29 between model predication value and J55 undergrounds measured value.

45 DEG C of temperature ＞：Relations (＞ 45 DEG C) of the Figure 30 between model predication value and J55 undergrounds measured value.

The contrast (≤45 DEG C) of corrosion rate and measured value after the fitting of table 2-37 J55 undergrounds

Sequence number	Measured value (mm/a)	Match value (mm/a)	Relative error
				1	0.0045	0.005	10.0%
2	0.6556	0.7123	8.0%
				3	6.2188	6.2976	1.3%
4	6.8913	6.6678	3.2%
				5	8.0876	8.4567	4.4%
6	2.9064	2.9346	1.0%
				7	16.6049	16.5431	0.4%
8	9.9523	9.96	0.1%
				9	1.7639	1.5098	14.4%
Mean error			4.7%

The contrast (45 DEG C of ＞) of corrosion rate and measured value after the fitting of table 2-38 J55 steel underground

Eliminate outside some abnormal datas, it is seen that J55 match values and down-hole simulation experiment measured value relative error be respectively 4.7% and 4.9%, data coincidence is preferable.

Technology path 2：

This experiment contemplate come from the temperature due to well head, the temperature of underground and well depth exist certain empirical relation (according to 3.5 DEG C of estimations of downhole temperature gradient)：

I.e.：T_Underground=T_{Well head}+ 0.035h (relational expression 1).

Therefore, if wellhead temperature and the function of the change of well head corrosion rate can be found out respectively by experiment, and The correlation function of downhole temperature and downhole corrosion speed, then can downhole corrosion speed and well are calculated by relation above formula generation The relation of mouth corrosion rate.

Due to the corrosion rate of either well head or underground, the more than temperature one of its influence factor, so if single Pure by transformation temperature, and other conditions are constant, then the relation obtained can be far from each other with actual conditions, therefore this project is by well Temperature, the CO of larger difference with underground be present in mouth₂Three partial pressure, stagnation pressure crucial corrosion influence factors, are normalized to temperature parameter, Well head and downhole corrosion speed and the functional relation of normalized temperature are determined respectively, and then pass through temperature and the relation of well depth, generation The correlation model of the well head corrosion rate that swaps out and downhole corrosion speed.

(1) down-hole simulation test parameters is set：N80 materials.

After test measurement, and mean value computation, the corresponding result of obtained downhole temperature and downhole corrosion speed is such as Shown in following table：

Table 2-39 down-hole simulations test parameters sets table

By above numerical value, downhole corrosion speed Y is fitted_UndergroundWith downhole temperature T_UndergroundFunctional relation it is as shown in figure 31： Figure 31 is the relation curve of downhole corrosion speed and downhole temperature.

Y_Underground=0.00007750T_Underground ³-0.01784687T_Underground ²+1.21903620T_Underground-19.68881518

(relational expression 2).

(2) well head simulated test parameter setting：N80 materials.

After test measurement, and mean value computation, the corresponding result of obtained wellhead temperature and well head corrosion rate is such as Shown in following table：

Table 2-40 wellhead temperatures and the corresponding table of well head corrosion rate

By numerical fitting, graph of a relation such as Figure 32 of wellhead temperature and well head corrosion rate is obtained：Wellhead temperature and well head The relation curve of corrosion rate.

I.e.：T_{Well head}=59.755Y_{Well head} ^0.4744(relational expression 3).

Relation above formula 1,2,3 is carried out for calculation, can obtain downhole corrosion speed Y_UndergroundWith well head corrosion rate Y_{Well head}, and Underground depth h incidence relation formula is as follows：

Y_Underground=0.00007750 × (59.755Y_{Well head} ^0.4744+0.035h)³-0.01784687×(59.755Y_{Well head} ^0.4744+ 0.035h)²+1.21903620×(59.755Y_{Well head} ^0.4744+0.035h)-19.68881518

From above-mentioned relation formula, if installing on-line monitoring inductance probe in well head, you can know the corruption of well head in real time Speed is lost, and then the downhole corrosion speed of different depth can be calculated.

Using inductance probe, laboratory carries out the corrosion simulated experiment of individual well, verifies the accuracy of above association results.Its Middle wellhead temperature presses 35 DEG C, wellhead back pressure 1MPa, well head carbon dioxide content 40%.

Underground trials condition is as shown in the table：The experimental condition of table 2-41 different depths

Analog reslt is as shown in the table：Table 2-42 is predicted and actual measurement comparison between corrosion table

From the result as can be seen that predicted value and the error of measured value are controlled within 10%, illustrate correlation model Predicted value be accurate.Studied by the laboratory simulation of this part, brief summary is as follows：

Pass through the analysis to live Produced Liquid composition, and the analysis of other industrial and minerals, it is determined that laboratory simulation test Correlated condition, determining the simulation corrosion factor of underground and well head includes temperature, stagnation pressure, CO₂Partial pressure, flow velocity, salinity, Yi Jihan Water.

Using inductance monitoring system and weight loss method, laboratory simulation HTHP dynamic test is completed, for The materials such as A3/N80/J55, carry out well head and down-hole simulation experiment amounts to 125 groups.

By the association analysis of corrosion coupon and inductance probe data, as a result show, the lacing film of laboratory simulation test and Inductance probe data have good uniformity, and quantitative incidence relation be present.

Analyzed by well head and the corrosion influence factors of underground, the results showed that, the row of well head and downhole corrosion influence factor Sequence is water content>Temperature>Stagnation pressure>CO₂Partial pressure>Flow velocity>Salinity.Wherein the corrosion most serious of underground when corresponding parameter difference For：45 degree of temperature, water content 90%, stagnation pressure 6MPa, CO₂Partial pressure 6MPa, flow velocity 0.6m/s, salinity 50000mg/L.

By the data analysis to well head and underground, C.de Waard CO are used for reference₂Corrosion prediction model, is intended by data The method of conjunction, A3, N80, J55 material under the conditions of well head, and the corrosion prediction mould of underground N80 and J55 material are determined respectively Type, by laboratory proofing, match value is consistent with measured value, and relative error is small, illustrates the accurate of forecast model.

Utilize the corrosion rate of well head, it is determined that the corrosion rate of well head and underground exists related to underground depth multinomial Formula relation:

Pass through the analogue measurement in laboratory, it was demonstrated that predicted value and the error of measured value illustrate to associate mould within 10% Type is true and reliable.

Embodiment 3. rises as application example from there.

CO₂Drive on-line corrosion monitoring system application study.

1. shore one ore deposit 1# experiment well corrosion monitoring application studies of south.

The experiment initial time of 1# test wells is on December 7th, 2015.

(1) installation of well head monitoring device and data analysis.

The field working conditions environment of one ore deposit 1# experiment wells of shore south is (in December, 2015)：

Wellhead temperature：18 DEG C, well head stagnation pressure：0.5Mpa, rod stroke：3m, sucker rod jig frequency：4th, liquid is produced daily： 31.8t, daily output water：27t, water content in crude oil：85%.

The liquids and gases sampling analysis data of the Produced Liquid of 1# test wells following (analysis time：December 23 in 2015 Day).

The Produced Liquid gas analysis result of table 3-1 1# test wells

Table 3-2 1# test well Produced Liquid fluid analysis results

1. inductance probe Monitoring Data：

Kiss is not present in the range of every influence factor that laboratory simulation experiment is set in the field working conditions of this experiment well The experiment condition point of conjunction, thus install initial stage according to scene parameter, done laboratory proofing experiment, to contrast experiment room with The data difference (inductance probe material A3 steel) at scene.

With reference to live industrial and mineral, determine that inside authentication experimental condition is：

Salinity：56900mg/L, water content 85%, stagnation pressure 0.5MPa, CO₂Partial pressure 0.4MPa, flow velocity 0.4m/s, temperature： 16℃。

A.A3 materials well head inductance probe Monitoring Data and analysis.See that Figure 33 tests for 1# wells inside authentication.

It is 1# well A3 steel incipient stability sections scene inductance probe data to see Figure 34.

Visible with the primary data contrast at scene, the stage corrosion rate in laboratory is 1.688mm/a, live corrosion rate For 1.699mm/a, relative error 0.67%, it is seen then that data coincidence is preferable.

See Figure 35 1# test well well head A3 inductance probe Monitoring Datas.

The initial time of 1# test wells, well head A3 inductance probes and lacing film installation is 7 days to 2015 12 December in 2015 The moon 30, the Monitoring Data of inductance probe is as shown in figure 35.Corrosion during data and curves, A3 steel inductance probe installation Reducing thickness 6098nm, section corrosion rate are 0.097mm/a.

Following table show well head inductance probe measured value, and A3 well head model predication values, and with well head lacing film measured value Comparing result.It can be seen that the corrosion rate that the weight loss data of the lacing film of the same period is drawn is 0.092mm/a, with inductance probe The relative error of measured value is 5.1%；The annual corrosion rate of A3 steel is 0.09058mm/a, predicted value and well head under the conditions of the industrial and mineral The error of inductance probe measured value is 6.6%.

The contrast of table 3-3 A3 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

B.N80 materials well head inductance probe Monitoring Data and analysis.

N80 materials inductance probe and the installation initial time of lacing film are on May 5,30 days to 2016 December in 2015, electricity Feel probe Monitoring Data it is as shown in figure 35, from corrosion curve as can be seen that N80 inductance probes install during corrosion thinning amount For 25217nm, section corrosion rate is 0.076mm/a.

It is No. 1 test well well head N80 inductance probe Monitoring Data figure to see Figure 36.

The corrosion rate that the weight loss data of the lacing film of the same period is drawn is 0.072mm/a, relative error 5.2%.

The condition tested according to inside authentication, the experiment of N80 materials is carried out, determines laboratory test results and field monitoring knot The uniformity of fruit.As a result show, the weight loss data of laboratory test are 0.073mm/a, relative error 1.3%.

The N80 well head corrosion prediction models drawn according to laboratory test, the annual corrosion rate of N80 steel is under the conditions of the industrial and mineral 0.06901mm/a, predicted value and the error of inductance probe well head measured value are 5.4%, and the error with lacing film well head measured value is 4.1%, it is seen that predicted value and the measured value goodness of fit are higher.

The contrast of table 3-4 N80 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

During N80 material tests, respectively on January 4th, 2016, on 2 4th, 2016, on March 4th, 2016, and On March 20th, 2016, on May 5th, 2016, the detection of iron content in Produced Liquid is carried out, as a result as shown in following table 3-5.

Table 3-5 iron ion content testing results

Inductance probe monitoring corrosion rate value corresponding to sample time and the relation of iron ion content are as shown in figure 37：Iron from The corresponding relation of sub- content and corrosion rate.

As seen from the above analysis, as the rising of iron ion content, corresponding inductance probe corrosion rate are also presented Ascendant trend, the two meets polynomial relation.

(2) correlation of well head and downhole corrosion data.

The live link schematic diagram of 1# test wells is as shown in figure 39：4-11x101 scenes link scheme of installation.

First group of link (N80) of link the 12, the 6th, the 3rd link (J55) and the 9th link (A3) are set at 600m.

Second group of link (N80) of link the 13, the 5th, the 2nd link (J55) and the 8th link (A3) are set at 900m.

The 3rd group of link (N80) of link the 14, the 4th, the 1st link (J55) and the 7th link (A3) are set at 1200m. Valve pump and pin oil drain are set at 1303.56m, wire-wrapped screen is set at 1312.71m.

Table 3-6 undergrounds different depth predicted value and the corrosion rate value (mm/a) of actual measurement

As seen from the above table, the predicted value of underground J55 links measured value and model contrasts, its relative error is respectively 4.8%, 7.5% and 6.3%, mean error 6.2%.The predicted value of underground N80 links measured value and model contrasts, its relative error point Not Wei 3.8%, 6.7% and 6.5%, mean error 5.7%.

By result above as can be seen that the relevance of well head and downhole data is preferable, well head corrosion rate and well are utilized The downhole corrosion rate values that lower corrosion rate correlation model is extrapolated are compared with being gone out using downhole corrosion influence factor data-speculative Numerical value is accurate, and analysis reason is as follows：The influence factor being related in model in the past can not possibly cover all influence factors, Influence including ion, the temperature of underground, pressure, partial pressure etc. are sharp as support, institute without real-time field measurement data in addition Data are generally empirical value or estimated value, therefore these factors limit the accuracy of model.And utilize laboratory Accuracy rate is high compared with field data when data are predicted, and is because the temperature of laboratory data, pressure etc. are the specific of experiment Parameter, it is relatively more accurate.

The prediction carried out using the correlation model of well head corrosion rate and downhole corrosion speed, due to for single well, this The influence of all kinds of complicated factors has been evaded in kind prediction, and the change of rate of corrosion is only associated with depth, therefore predicted value is more direct The value degree of accuracy of prediction is high.

Embodiment 4

Shore one ore deposit 2# experiment well corrosion monitoring application studies of south.

The starting test period of 2# test wells is on January 23rd, 2016.

The mount scheme of 2# test well well head corrosion monitoring systems is still inductance probe and lacing film.

Shore south one ore deposit 2# experiment wells field working conditions environment be：Wellhead temperature：25 DEG C, wellhead back pressure：0.8MPa, daily output Liquid：10.5t, daily output water：7.3t, rod stroke：2.4m, sucker rod jig frequency：5.

The liquefied gas analyze data in April, 2015 is as follows：Salinity 72334.4mg/L, chlorion 38995mg/L, always Carbanion 5796.9mg/L, CO₂Content is 45%, water content in crude oil：70%.

(1) well head inductance corrosion monitoring system.

A.A3 steel inductance probe well head Analysis on monitoring data.Figure 40 2# test well A3 material inductance probe Monitoring Datas.

The initial time of No. 2 test wells, well head A3 inductance probes and lacing film installation is 23 days to 2016 5 January in 2016 The moon 3, the Monitoring Data of inductance probe is as shown in figure 40.Corrosion during data and curves, A3 steel inductance probe installation Reducing thickness 32381nm, section corrosion rate are 0.117mm/a.

The contrast of table 3-7 A3 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

The corrosion rate that the weight loss data of the lacing film of the same period is drawn is 0.110mm/a, relative error 5.9%.

Laboratory model prediction result under the hole condition is 0.108mm/a, and the relative error with hanging film scene measured value is 1.8%, the error with inductance probe measured value is 7.6%.

During A3 material tests, respectively on January 23rd, 2016, on 2 15th, 2016, on March 15th, 2016, with And on April 15th, 2016, on May 5th, 2016, the detection of iron content in Produced Liquid is carried out, as a result as shown in following table 3-8.

Table 3-8 iron ion content testing results

Inductance probe monitoring corrosion rate value corresponding to sample time and the relation of iron ion content are as shown in figure 41：Iron from The corresponding relation of sub- content and inductance probe corrosion rate.

As seen from the above analysis, as the rising of iron ion content, corresponding inductance probe corrosion rate are also presented Ascendant trend, the two meets polynomial relation, is coincide with the result of 1# test wells.

B.N80 steel inductance probe well head Analysis on monitoring data.See that Figure 42 monitors for No. 2 test well N80 materials inductance probes Data.

Red curve represents inductance probe corrosion losses value, and blue curve represents inductance probe temperature.N80 inductance probes Section corrosion losses value is 689nm.Corrosion rate is 0.0112mm/a, and corrosion is slight.Model predication value under the conditions of this is 0.0108mm/a, the two relative error are 3.5%.

The contrast of table 3-9 N80 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

(2) correlation of well head and underground link data.

The live link scheme of 2# test wells is the same as No. 1 test well.

Table 3-10 undergrounds different depth predicted value and the corrosion rate value (mm/a) of actual measurement

As seen from the above table, the predicted value of underground J55 links measured value and model contrasts, its relative error is respectively 7.9%, 6.5% and 8.0%, mean error 7.5%.The predicted value of underground N80 links measured value and model contrasts, its relative error point Not Wei 7.4%, 7.7% and 7.4%, mean error 7.5%.

By result above as can be seen that the relevance of well head and downhole data is preferable, well head corrosion rate and well are utilized The downhole corrosion rate values that lower corrosion rate correlation model is extrapolated are compared with being gone out using downhole corrosion influence factor data-speculative Numerical value is accurate, and analysis reason is as follows：

Embodiment 5

3. shore one ore deposit 3# experiment well corrosion monitoring application studies of south

Test pound sign：10x100.

Hole condition condition：Stroke：4th, jig frequency：3.5th, wellhead temperature：20 DEG C, wellhead back pressure：0.9MPa, daily output liquid：8t, daily output Water：7.4t, water content：97%.

(1) well head corrosion monitoring.

Mount scheme：The mount scheme of 3# test well well head corrosion monitoring systems is still inductance probe and the comprehensive prison of lacing film Survey.Test initial time：In October, 2016.Well head corrosion monitoring application result：

The contrast of table 3-11 A3 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

The contrast of table 3-12 N80 material inductance probe corrosion rates and lacing film corrosion rate and predicted value

The inductance probe prison of well head A3 and N80 material is can be seen that from the well head corrosion monitoring result of the test of above table Survey result and lacing film measured result, and model prediction result are consistent, and error is below 6%.

(2) correlation of well head and underground link data.The live link scheme of 3# test wells is the same as 1, No. 2 test well.

Table 3-13 undergrounds different depth predicted value and the corrosion rate value (mm/a) of actual measurement

As seen from the above table, the predicted value of underground J55 links measured value and model contrasts, its relative error is respectively 5.6%, 6.9% and 6.3%, mean error 6.3%.The predicted value of underground N80 links measured value and model contrasts, its relative error point Not Wei 8.7%, 5.9% and 6.9%, mean error 7.2%.

The result：Estimated value and the error of measured value are controlled within 10%, are illustrated the estimated value of correlation model and are Accurately.Relevance model is successfully established.

Using well head inductance probe measured result, underground is calculated not by " well head downhole corrosion speed correlation model " With the corrosion rate change curve of well depth, it is known that 3 mouthfuls of well corrosion rate maximums respectively appear in 1# well depth 910m, 2# well depths At 980m, 3# well depth 900m.Such as Figure 44, Figure 45, shown in Figure 46.

By in the different types of corrosion monitoring apparatus development of well head and underground and field test, realizing well head and underground The comprehensive monitoring of equipment, may be summarized as follows：

The well head inductance monitoring of (1) No. 1 test well completes the field test of A3 steel materials and N80 materials.Monitoring result The well head corrosion monitoring speed for showing A3 steel and N80 materials is respectively 0.097mm/a and 0.076mm/a.Monitor and tie with lacing film Fruit contrasts, and relative error is respectively 5.1% and 5.2%, and inductance probe measured value contrasts with well head corrosion rate prediction result, phase It is respectively 6.6% and 5.4% to error.

The well head experiment of (2) No. 2 test wells completes the field test of A3 and N80 materials.As a result A3 and N80 well are shown Mouth corrosion monitoring speed is respectively 0.117mm/a and 0.0112mm/a.It is higher with the lacing film monitoring result contrast goodness of fit, it is relative to miss Difference is respectively 5.9% and 4.9%.Inductance probe measured value contrasts with well head forecast model, and relative error is respectively 6.0% He 5.8%.

The well head experiment of (3) No. 3 test wells completes the field test of A3 and N80 materials.As a result A3 and N80 well are shown Mouth corrosion monitoring speed is respectively 0.108mm/a and 0.096mm/a.It is higher with the lacing film monitoring result contrast goodness of fit, it is relative to miss Difference is respectively 5.7% and 4.9%.Inductance probe measured value contrasts with well head forecast model, and relative error is respectively 7.6% He 3.5%.

(4) the regular iron ion content testing result of test well, i.e. corrosion rate liter consistent with corrosion rate result of variations During height, iron ion content also accordingly increases, and the two meets polynomial relation.

(5) the measured value result of underground link is visible with the predicted value contrast that well head and underground correlation model determine, its Relative error is respectively less than 10%, illustrates that the well head corrosion rate of correlation model determination and the relation of downhole corrosion speed are reliable 's.Studied by laboratory simulation, it is determined that CO₂Drive the corrosion regularity of well, it is determined that the power of the corrosion influence factors of its underground Weight order is water content>Temperature>Stagnation pressure>CO₂Partial pressure>Flow velocity>Salinity.

Corresponding parameter difference during by well head and the analysis of the corrosion influence factors of underground, wherein the corrosion most serious of underground For：45 degree of temperature, water content 90%, stagnation pressure 6MPa, CO₂Partial pressure 7.5MPa, flow velocity 0.6m/s, salinity 50000mg/L.

Pass through the analogue measurement in laboratory, it was demonstrated that predicted value and the error of measured value are hung within 10% by scene The checking of loop data, it was demonstrated that model predication value and the error of field measurement value are also controlled within 10%, illustrate that correlation model is true It is real reliable.Realize the project objective by corrosion condition under well head inductance probe corrosion rate image well.

The inductance probe used in the technical program and compensation method can be Application No.：Electricity in 2017103383610 Feel probe and compensation method.A kind of entitled high voltage induction probe for measuring rate of metal corrosion and its compensation method.

A kind of high voltage induction probe for measuring rate of metal corrosion, including six core glasses envelope screen air plug, O-ring seal gear Circle, O-ring seal, transition conduit, casting glue, wire, probe rod, protective cap, compensation test piece and measurement test piece.Six described core glass The air plug of glass envelope screen draws measurement signal by inner lead, by insulated enclosure between lead and shell, wire and boat Shell isolated insulation is inserted, while good sealing function can be played under high-temperature high-pressure medium, is prevented after piercing probe in pipeline Medium ooze out.Described O-ring seal back-up ring and O-ring seal coordinate cone structure, and device is picked out to probe and probe and is risen Sealing function.

Described transition conduit one end is connected with air plug, and the other end is welded and fixed after being connected with the rear end of screw thread and probe rod, is surveyed Amount test piece is fixed on the front end of probe rod.

Described wire is enclosed in inside probe rod, the connection measurement test piece of one end of wire and compensation test piece, wire it is another One end is connected to glass envelope screen air plug.Described compensation test piece is enclosed in the inside of measurement test piece, and measurement test piece isolation welding, Avoid producing galvanic corrosion.Described protective cap and the connected mode of probe rod are to be threaded togather.

Using the technique welded again after being first threadedly coupled between above-mentioned transition conduit and probe rod, even if ensureing weld bond cracking, Because threaded portion keeps connecting, probe rod is unlikely to come off into channel interior.

In the back-up ring groove and o-ring groove on conical section that six core glasses envelope screen air plug is connected with transition conduit respectively It is equiped with O-ring seal back-up ring and O-ring seal.

By the process filling of casting glue inside above-mentioned probe rod, prevent from occurring loosening because of vibration and crack conditions, Internal supporting role is risen to measurement test piece and probe rod, improves the anti-pressure ability of probe, once piercing probe, rising prevents probe from oozing Dew and the effect of corrosion.

Above-mentioned protective cap interlocks perforate, and protective cap adds jackscrew locking, while also 2 spiral shells after being connected with probe rod Line destroys fabrication hole, and screw thread is destroyed at hole, ensures that protective cap does not take off with probe rod.

A kind of compensation method for the high voltage induction probe for measuring rate of metal corrosion：

To ensure in the case where probe length is constant, during probe thickness increase, the reality of probe can be accurately measured Value is thinned in border, eliminates the influence that non-linear section of the thickness more than 8mm is brought to measurement accuracy, the present invention is using following step Suddenly：

Step 1: taking suitable test piece physical size, pass through technique for temperature compensation and mathematical modeling continuous benefit free of discontinuities Technology is repaid, the reality of measurement test piece is thinned and forms good fitting with model compensation；Step 2: will be all by backoff algorithm Measure theory value list one by one, form is made, can is surveyed after resistance using looking into reading in gatherer process afterwards Table method obtains actual Reducing thickness.

Above-mentioned test piece physical size includes the external diameter R of tubulose test piece, the internal diameter r of tubulose test piece, the wall thickness of tubulose test piece δ, the test piece length L of tubulose test piece.

Above-mentioned technique for temperature compensation and mathematical modeling Continuous Compensation technology free of discontinuities be to temperature compensation test piece and Measurement test piece compensates respectively, makes that the reality of measurement test piece is thinned and model compensation forms good fitting, make measurement result with it is true Real value is coincide.

What above-mentioned form included is external diameter from 9.5mm until be thinned for 7.5mm segments all measured values and its Intermediate function, it is succinct directly perceived after list, it is easy-to-look-up.

The present invention has advantages below：

Measurement corrosion indirectly, by measuring the corrosion rate of phase same material component come the corrosion condition of indirect reaction pipeline, It is to be added up by the corrosion thinning amount of a period of time to calculate rate of corrosion, measurement is convenient and swift, workable.

Can adapt to the measuring environment of high pressure, overall highest of the probe including measurement test piece can pressure-resistant 60Mpa, it is long Time is not in damage using inductance probe.

Resist fluids impact capacity and bend resistance ability are strong, protection test piece, by the technique of casting glue fix wire and Solder terminal, prevents from occurring loosening because of vibration and crack conditions make probe safety coefficient double.

Measurement thickness of test piece increases to 1mm, and service life increase, temperature-compensating and the dual penalty method of mathematical modeling make measurement As a result it is more accurate.

Measurement test piece is isolated with compensation test piece, compensation test piece is in absolute stability state, survey is penetrated into measured medium Behind inner space where amount test piece, probe destruction will not be made.

Measurement test piece uses material of the same race with probe rod, avoids producing galvanic corrosion.

The actual measurement resistance of probe is obtained by high precision instrument using the compensation method of the present invention, actual measurement resistance and theory Depth Macro or mass analysis is thinned, according to the nonlinear characteristic of theoretical curve, segmented compensation function is set, develops mathematical compensation model, Compensated by actual contrast, precision is higher than 1%.

The actual measurement resistance collected and theoretical thinned depth are compiled into the data table of comparisons, by corresponding numerical value in formula also one And list, so uniformly it is being thinned ideally, measured value is definitely objective and accurate, hereafter often measures an actual measurement resistance, Can is shown the actual numerical value after compensation by look-up table, convenient and reliable.

The inventive method can cause small-caliber pipeline to use this inductance probe.

Accurate measurement Corrosion results, the service life and peace of probe can be added in the case where measurement test piece thickeies Overall coefficient.

Embodiment

Embodiment one

A kind of high voltage induction probe for measuring rate of metal corrosion, including six core glasses envelope screen air plug 1, transition conduit 4, probe Bar 7, compensation test piece 9 and measurement test piece 10, it is characterised in that：

The rear end of transition conduit 4 is sealed screen air plug 1 with six core glasses and is fixedly connected, and front end and the screw thread of probe rod 7 of transition conduit 4 connect It is welded and fixed after connecing, the rear end of measurement test piece 10 is fixedly connected with the front end of probe rod 7, and the compensation insulation-encapsulated of test piece 9 is measuring In test piece 10.One end of wire 6 is sealed screen air plug 1 with six core glasses and is connected, and the other end and the measurement test piece 10 and compensation of wire 6 try Piece 9 connects.

Wire 6 is located in transition conduit 4 and probe rod 7, and glue is filled between wire 6 and the inwall of transition conduit 4 and probe rod 7 5。

Protective cap 8 is set with measurement test piece 10, the rear end of protective cap 8 is connected with the nose threads of probe rod 7, and with multiple Jackscrew is fixed, and multiple holes 11 are offered on protective cap 8.

Embodiment two

A kind of sheet inductance probe compensation method for being used to measure corrosive pipeline, comprises the steps：

1st, obtain testing the actual measurement resistance of piece：

It is 9.5-7.5mm to test piece internal diameter r=7mm, external diameter R, then has：

δ=0.5- (R-r)/2 ... ... ... formula 2

S=3.14* (R²-r²) ... ... ... formula 3

ρ_Survey=L/s ... ... ... ... formulas 4

h_max=1000000* δ ... ... ... formulas 5

△ ρ=ρ_Survey-ρ_Mend... ... ... ... formula 6

△=Δ ρ/ρ_Mend... ... ... ... formula 7

h_{Actual measurement}=△ * 262144 ... ... ... formulas 8

Symbol explanation in examination：

Measure test piece external diameter R (units：Mm), test piece internal diameter r (units：Mm), thickness of test piece δ (units：Mm), test piece length L (units：Mm), the sectional area s (units of test piece：mm²), theoretical maximum corrosion depth h_max(unit：Nm), test piece resistance value ρ_Survey (unit：M Ω), compensation test piece resistance ρ_Mend(unit：M Ω), resistance difference △ ρ, difference value △, actual measurement resistance h_{Actual measurement}(unit： nm)。

It is hereby achieved that the actual measurement resistance of measurement test piece.

2nd, the measure theory value added after backoff algorithm.

Measure theory value can be obtained by adding backoff algorithm according to the actual measurement resistance calculated, when actual displayed, The intuitively data that we need to see are exactly measure theory value, it is assumed that measure theory value h_{It is theoretical}(unit：Nm), according to mathematical modulo Comparison diagram (such as Figure 43) before and after type compensation is not as can be seen that measure theory value is linear change, so backoff algorithm is according to song Line form uses segmented compensation.

h_{It is theoretical}=3.75*h_{Actual measurement}+ 65535, h_{Actual measurement}≤-52428

h_{It is theoretical}=2.5*h_{Actual measurement}, -52428 ＜ h_{Actual measurement}＜ 0

h_{It is theoretical}=h_{Actual measurement}, h_{Actual measurement}≥0

3rd, form is drawn.

According to above-mentioned calculation formula, actual measurement resistance h can be obtained_{Actual measurement}, measure theory value h_{It is theoretical}Important intermediate variables with some, With this method calculate external diameter R from 9.5mm be thinned to 7.5mm during total data, wherein, internal diameter r be 7mm it is constant.Data meter After having calculated, form is depicted as, the foundation as look-up table.

Following table, the part sheet inductance probe drawn by backoff algorithm compensate value comparison table.

It is long	79.06	79.06	79.06	79.06	79.06	79.06	79.06
								External diameter (width)	8.06	8.04	8.02	8.00	7.98	7.96	7.94
Internal diameter (thickness)	7.00	7.00	7.00	7.00	7.00	7.00	7.00
								UR(δ)	(0.030)	(0.020)	(0.010)	(0.000)	0.010	0.020	0.030
Sectional area	12.53	12.28	12.03	11.78	11.52	11.27	11.02
								Resistance (m Ω)	6.31	6.44	6.57	6.71	6.88	7.01	7.17
Resistance value and	6.3751	6.5050	6.6400	6.7804	6.9266	7.0788	7.2376
								Theoretical depth	(30000)	(20000)	(10000)	(0)	10000	20000	30000
Resistance difference	(0.4053)	(0.2754)	(0.1404)	(0.0000)	0.1462	0.2985	0.4972
								Difference value	(0.0598)	(0.0406)	(0.0207)	(0.0000)	0.0216	0.0440	0.0674
18	(15669)	(10648)	(5429)	(0)	5651	11539	17678
								Existing measure theory value	(39172)	(26619)	(13572)	(0)	5651	11539	17678

Claims

1. well head downhole corrosion speed correlation model algorithm, it is characterised in that comprise the following steps：

The first step, with CO₂Corrosive environment is research object, using six factors, the experiment of five horizontal quadratures, research temperature, CO₂Partial pressure, Stagnation pressure, salinity, oil-water ratio and flow velocity are to well head and the influence degree of downhole corrosion speed；

Second step, based on C.de Waard DM models, model is modified using orthogonal experiment data, established respectively Well head, downhole corrosion rate prediction model；

3rd step, by temperature, CO₂Three partial pressure, stagnation pressure crucial corrosion influence factors, are normalized to temperature parameter, determine well respectively The functional relation of mouth, downhole corrosion speed and temperature；

4th step, the thermograde empirical equation existing for temperature and well depth carry out, for calculation, obtaining well head and downhole corrosion speed Relevance model.

2. well head downhole corrosion speed correlation model algorithm according to claim 1, it is characterised in that comprise the following steps： Orthogonal experiment data are drawn according to following experiment in the first step：

First, by reactor good seal, the air-tightness of verifying attachment；

Second, the preparation of simulated produced fluids, made according to tested well water matter corrosivity anions and canons component content；

3rd, the pre-treatment of corrosion coupon；

4th, simulated produced fluids are fitted into reactor according to experiment setting value, and start heater, temperature is raised to predetermined Temperature；

5th, inductance probe and lacing film are connected with reactor, nitrogen is filled with first to setting value, is re-filled with CO₂Pressed to stable Power；

6th, inductance probe collector is connected, log-on data software, starts to communicate；

7th, observed data reads situation and pressure changing；

8th, after experiment maintains 2-4 days, inductance probe data and curves are intercepted, lacing film is taken out into reactor；

9th, the processing of inductance probe and lacing film, the corrosion product on inductance probe and lacing film surface is taken out with cleaning agent, after drying Weigh, record data, wait follow-up calculate；

Tenth, solution in reactor is extracted out with water pump, recycled；

11st, analyze data, calculate single group corrosion rate；

12nd, single group laboratory report is write, by photo before and after reaction, inductance probe corrosion data, lacing film corrosion data is carried out Analysis.

3. well head downhole corrosion speed correlation model algorithm according to claim 1, it is characterised in that comprise the following steps： The influence degree obtained in the described first step is：1), range analysis corrosion factor weighing factor order is：Oil-water ratio ＞ temperature ＞ stagnation pressure ＞ CO₂Partial pressure ＞ flow velocity ＞ salinities；2), material corrosion most serious condition：Temperature 45 C, salinity 50000mg/L, Water-oil factor 90%, stagnation pressure 6MPa, CO₂Partial pressure saturation.

4. well head downhole corrosion speed correlation model algorithm according to claim 1, it is characterised in that comprise the following steps： The forecast model obtained in described second step is：

N80_MaterialWell head Y=-230.92m⁶+1147.9m⁵-2170.7m⁴+1953.8m³-833.93m²+152.52m-7.6437；

N80_MaterialUnderground Y=-0.1795m⁵+2.6596m⁴-13.787m³+28.627m²-19.178m+4.0761；

J55_MaterialWell head Y=-124.09x⁵+462.1x⁴-563.22x³+255.23x²-22.782x+0.429；

J55_MaterialUnderground Y=-0.2492x⁵+3.7408x⁴-19.728x³+42.23x²-30.637x+7.0631。

5. well head downhole corrosion speed correlation model algorithm according to claim 1, it is characterised in that comprise the following steps： The following relation obtained from the 3rd described step and the 4th step：

Relational expression 1：T_Underground=T_{Well head}+0.035h；

Relational expression 2：Y_Underground=0.00007750T_Underground ³-0.01784687T_Underground ²+1.21903620T_Underground-19.68881518；

And relational expression 3：T_{Well head}=59.755Y_{Well head} ^0.4744；

Carry out for calculation, obtain downhole corrosion speed Y_UndergroundWith well head corrosion rate Y_{Well head}, and underground depth h incidence relation formula such as Under：

Relational expression 4：Y_Underground=0.00007750 × (59.755Y_{Well head} ^0.4744+0.035h)³-0.01784687× (59.755Y_{Well head} ^0.4744+0.035h)²+1.21903620×(59.755Y_{Well head} ^0.4744+0.035h)-19.68881518。

6. use the downhole corrosion speed on-line monitoring method of well head downhole corrosion speed correlation model algorithm, it is characterised in that bag Include the following steps：

Pass through inductance probe real time on-line monitoring well head corrosion rate；

The corrosion rate of underground different depth is calculated using the relevance model of well head downhole corrosion speed, and then understands underground and sets Standby corrosion condition.

7. the downhole corrosion speed according to claim 6 using well head downhole corrosion speed correlation model algorithm is supervised online Survey method, it is characterised in that comprise the following steps：

Well head inductance probe corrosion data is gathered, lacing film corrosion data should be gathered simultaneously during application for the first time, for inductance probe Monitor the amendment of corrosion rate value.

8. the well incision rate according to claim 6 using well head downhole corrosion speed correlation model algorithm is monitored on-line Method, it is characterised in that include the following steps：

9. the well incision rate according to claim 7 using well head downhole corrosion speed correlation model algorithm is monitored on-line Method, described makeover process are completed according to following correction model：

Y=1.1877X-0.0013

Y is the corrosion rate of inductance probe monitoring in above formula, and X is the corrosion rate of lacing film monitoring.

10. the downhole corrosion speed according to claim 6 using well head downhole corrosion speed correlation model algorithm is online Monitoring method, it is characterised in that comprise the following steps：The relevance model of well head downhole corrosion speed is：Y_Underground= 0.00007750×(59.755Y_{Well head} ^0.4744+0.035h)³-0.01784687×(59.755Y_{Well head} ^0.4744+0.035h)²+ 1.21903620×(59.755Y_{Well head} ^0.4744+0.035h)-19.68881518。