CN105019889A - Low-temperature oxidation rate prediction and safety protection method for light oil reservoir crude oil - Google Patents
Low-temperature oxidation rate prediction and safety protection method for light oil reservoir crude oil Download PDFInfo
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Abstract
The invention provides a low-temperature oxidation rate prediction and safety protection method for light oil reservoir crude oil, and belongs to the field of oil exploitation engineering. The method comprises the following steps: 1, measuring the relative density of crude oil; 2, determining whether the crude oil is of a light oil reservoir, and if so, turning to a third step; 3, actually measuring the temperature of a single-well stratum of the oil reservoir; 4, determining the temperature of the oil reservoir; 5, calculating the reaction time arriving at a safety oxygen value by utilizing the following formula, namely implementing oxidation rate prediction: y=1.336*10<-7>e<4732.6/T>, wherein y is the reaction time arriving at the safety oxygen value, the unit of y is day, T is the temperature of the oil reservoir determined in step 4, the unit of T is K, and e is a constant in natural logarithm of mathematics; 6, determining the underground residence time of injected fluid; and 7, comparing the underground residence time of the injected fluid with the reaction time arriving at the safety oxygen value.
Description
Technical field
The invention belongs to oil exploitation engineering field, be specifically related to a kind of light oil reservoirs crude oil low-temperature oxidation rate prediction and safe precaution method, be applicable to air injection, Air-foam supplements oil reservoir stratum energy and improve recovery ratio.
Background technology
Air injection and air foam are light oil reservoirs raising recovery ratio new technologies, and air foam is mainly used in the steady oil of " three is high " oil field precipitation and the raising recovery ratio that are in development late stage; Hypotonic, the gas injection as extensive in northwest China oil field of ultralow permeable reservoir and water-deficient area that air injection is mainly used in water filling makeup energy difficulty supplement stratum energy exploitation, to raising field output and recovery ratio significant.
Due to air source extensively, the not abundantest by the restriction in region and space, source of the gas, cost the most cheap (comparing with flue gas with CO2, N2).The oil reservoir kind that air injection is suitable for, the degree of depth, scope are comparatively extensive.
There is unlike the whole process of, air injection the risk that the associated gas (natural gas) in crude oil blasts with air with other gas of note, therefore the safety issue of air injection is everybody focus paid close attention to and problem worried most always.But gas explosion must possess three conditions:
1) first condition is suitable concentration of natural gas: in air, (oxygen concentration 21%) concentration of natural gas is in 3.21% ~ 10.32% scope, and concentration is greater than or less than this scope and all can not explodes;
2) second condition is suitable oxygen concentration: be greater than 10% ~ 11%;
3) the 3rd condition is the existence of high temperature burning things which may cause a fire disaster.
So-called " suitable concn " refers to the concentration that can blast.Often kind of fuel gas, in oxygen, has a scope that can blast.Exceed this scope, namely use very strong incendiary source to excite blast.This concentration range is explosion limit.
Three lacks one and namely can not blast.Therefore in actual applications, as long as the strict Valid concentration controlling oxygen and natural gas, just can eliminate safe hidden trouble completely.
In-house laboratory investigation and site test results show, in air injection process, the oxygen generation low-temperature oxidation in crude oil and air is reacted, and with the rising of temperature, oxidizing reaction rate exponentially rises regularly, follows Arrhenius empirical formula: k=k
0e
– Ea/RT, along with the prolongation in reaction time, consume the oxygen in air gradually thus the oxygen content in the natural gas of producing well output and air Mixture reached within the scope of safe oxygen.
How to predict the oxygen that injects air and crude oil generation low-temperature oxidation is reacted thus the reaction time making oxygen content in safe range guarantees air injection project safety and the rational key point of safety precaution.
After current prediction oil reservoir injection air, low-temperature oxidation reaches the method for safe oxygen time normally: understood by crude oil low-temperature oxidation laboratory experiment for needing the oil reservoir of air injection.Model experiment comprises:
(1) calorimeter experiment is accelerated:
Measure that can the air that inject with crude oil, heat-producing chemical reaction occur under reservoir conditions, can crude oil the experiment of spontaneous combustion, determine the reactivity of Reservoir Crude Oil and air, determine oxidation reaction kinetics parameter.
(2) little isothermal reactor experiment:
Carry out the experiment of little isothermal reactor, measure different pressures, temperature, water, oil saturation, air Injection speed, enriched gas to the impact of reaction speed.Determine oxidation reaction kinetics parameter, determine the reactivity of Reservoir Crude Oil and air.
(3) high-pressure oxidation pipe experiment:
Measure the composition of the rear output gas of the output of oil, gas break through and breakthrough.
(4) isothermal flue gas flooding experiment:
Under reservoir temperature pressure condition, simulated flue gas sweep oily process, determine oil recovery factor.
(5) adiabatic air drives experiment:
The displacement situation of high-temperature oxydation leading edge in simulating oil deposit.
Etc. (6) warm air drives experiment:
When fuel factor is not the principal element improving recovery ratio, at simulating oil deposit temperature, air sweeps oily process.
Carry out low-temperature oxidation experimental period by indoor laboratory very long, workload is large, and cost is high, and is not that each oil reservoir all has the condition of carrying out laboratory experiment, affects and limits the filed application of air injection and air foam flooding shaft, be unfavorable for large-scale promotion.
Summary of the invention
The object of the invention is to solve the difficult problem existed in above-mentioned prior art, a kind of light oil reservoirs crude oil low-temperature oxidation rate prediction and safe precaution method are provided, determine that oil well output gas reaches oxidation time needed for safe oxygen, each oil reservoir needing air injection or Air-foam to supplement stratum energy or raising recovery ratio solving prior art existence need carry out the problem that indoor low temperature oxidation experiment understands crude oil low-temperature oxidation speed, and solution laboratory experiment workload is large, the time is very long, technical sophistication, costly problem; Solution never possesses the problem of the Forecast Oil Reservoir Distribution crude oil low-temperature oxidation speed of carrying out indoor low temperature oxidation experiment; Solve the problem that one-house show cannot carry out experiment; Solve the temperature limit problem of suitable air injection oil reservoir.
The present invention is achieved by the following technical solutions:
A kind of light oil reservoirs crude oil low-temperature oxidation rate prediction and safe precaution method, applying light crude oil low-temperature oxidation rate prediction formula can predict crude oil oxidation rate at different temperatures, reach oxidation time needed for safe oxygen, application is injected the methods such as tracer monitoring and is determined to inject fluid in the subsurface detention time, contrasted in the subsurface detention time by required oxidation time and injection fluid, can accurately know inject air oxygen before arrival withdrawal well whether within the scope of safe oxygen, and according to two time extents corresponding security precautions technology scheme of extraction respectively.
Said method comprising the steps of:
The first step: measure relative oil density;
Second step: determine whether as light oil reservoirs, in this way, then proceeds to the 3rd step;
3rd step, actual measurement oil reservoir individual well formation temperature;
4th step, determines reservoir temperature;
5th step, utilizes formulae discovery below to reach the safe oxygen value reaction time, namely achieves oxidation rate prediction:
y＝1.336×10
-7e
4732.6/T
Wherein, y is for reaching the safe oxygen value reaction time, and unit is sky, and T is the reservoir temperature that the 4th step is determined, the unit constant that to be K, e be in mathematics in natural logrithm;
6th step, determines to inject fluid in the subsurface detention time;
7th step, compares and injects fluid in subsurface detention time and reach the safe oxygen value reaction time,
If injection fluid was greater than in the subsurface detention time reach the safe oxygen value reaction time, then output gas safety, regularly carry out output gas containing oxygen monitoring at well head; If injection fluid was less than in the subsurface detention time reach the safe oxygen value reaction time, then there is hidden danger in output gas, proceeds to the 8th step;
8th step, carries out the safety precaution of beam body.
The described first step is achieved in that and obtains crude oil sample at the wellhead of the oil reservoir oil well that need carry out air injection, then carries out relative oil density mensuration to crude oil sample, obtains relative oil density.
Described second step is achieved in that
Relative oil density refers to the ratio of oil density and 4 DEG C of pure water density under ground standard condition (20 DEG C, 0.1MPa).Relative oil density be less than or equal to 0.852 be called light crude oil.Namely this step judges whether the relative oil density that the first step records is less than or equal to 0.852, in this way, is then light oil reservoirs.
Described 3rd step is achieved in that
Under lower going-into-well in the middle part of thermometer (mechanical type or electronic temp meter) to each producing well and Injection Well oil reservoir, record downhole temperature or temperature gradient.
Described 4th step is achieved in that
The each well observed temperature obtained according to the 3rd step is (due to different instruments, personnel, condition etc., probe temperature value has certain fluctuation, temperature can not be determined with single a bite well, need the data of many mouthfuls of wells to go forward side by side row relax) and well depth data carry out statistical regression analysis, obtain temperature and well depth relation formula;
Depth data in the middle part of oil reservoir is substituted into described temperature and well depth relation formula, determine oil reservoir middle portion temperature, and the unit of oil reservoir middle portion temperature is scaled thermodynamic temperature by Celsius temperature.
Described 6th step adopts one of two kinds of methods below to realize:
1, direct method: inject tracer to water injection well, from corresponding oil well sampling monitoring tracer output, sees the tracer peak of injection from oil well, be defined as injecting water and namely inject fluid in the subsurface detention time from the time of well arrival oil well;
2, according to inter-well distance, indirect method: determine to inject fluid at stratum fltting speed according to water filling current intelligence, determines that injecting fluid arrives the withdrawal well time.
Described 8th step is achieved in that
According to injection fluid in subsurface detention time and the difference size reaching safe these two times in oxygen value reaction time, one or more safety measures below extraction in 5 kinds of measures:
1. and 5. (5) if the difference of two times is less than or equal to 10 days, then measure is adopted;
(6) if the difference of two times is greater than 10 days but be less than or equal to 20 days, then measure is adopted 1., 2. and 5.;
(7) if the difference of two times is greater than 20 days but be less than or equal to 30 days, then measure is adopted 1., 2., 3. and 5.;
(8) if the difference of two times is greater than 30 days, then 5 kinds of measures need all to adopt;
5 kinds of safety measures are:
1. within increasing preposition foam solution section 300m3: increase a preposition pure foam liquid section before air injection, foam solution section size is according to the difference of two times, and difference is larger, then preposition section of foam volume is larger;
2. control injection rate: compared with water filling, reduce injection rate, difference is larger, then injection rate reduces more;
3. temporarily close down producing well: the corresponding line oil well closing well of air injection or air foam well, the closed-in time is the difference of two times;
4. newly-built flooring-safe facility: build emptying pipe support height emptying casing gas; Production fluid enters uncovered fluid reservoir, and make gas emptying after gas emptying or air inlet liquid/gas separator, production fluid enters closed gathering system again;
5. strengthen the monitoring of output gas oxygen content: encrypt a line producing well casing gas containing oxygen monitoring, with Portable monitor or use on-line computing model Real-Time Monitoring, once find to exceed standard containing oxygen in output gas, close down oil well immediately and suspend Injection Well and construct.
Compared with prior art, the invention has the beneficial effects as follows: application the present invention, in known reservoir temperature situation, just can fast and easy prediction air injection or air foam time air in oxygen react in underground and crude oil to reach within the scope of safe oxygen value needed for the reaction time; Can determine to inject fluid in once holdup time by method such as note tracer etc.; By the contrast to two times, just accurately can to know after oil reservoir injection air or air injection foam in producing well output gas oxygen content whether in safety value, therefore can work out when working out geology (reservoir engineering) scheme and effectively prevent has channeling measure, guarantee the holdup time of air in oil reservoir, thus ensure that oxygen content in the gaseous mixture of producing well output is in safe range.When working out scheme of project construction and scene injects design and production management system, corresponding safe precaution measure and on-site supervision system can taked according to the difference of two times, reducing the labour intensity of safe precaution measure cost and site operation personnel.
Accompanying drawing explanation
Fig. 1 is air injection field test reservoir temperature and keto consumpting speed relation curve.
Fig. 2 is the step block diagram of the inventive method.
Fig. 3 tells to breathe out Shanshan Oil Field crude oil low-temperature oxidation experimental temperature and reaction rate curve.
Fig. 4 triumph battalion's 204 pieces of low-temperature oxidation experimental temperatures and keto consumpting speed curve.
Fig. 5 reservoir temperature with reach safe oxygen time curve.
Fig. 6 is female 10 pieces of ground temperature gradient curves in the embodiment of the present invention.
Fig. 7 is female 16 well group waterline direction of propulsion schematic diagrames in the embodiment of the present invention.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is described in further detail:
Carry out in oil field in air oil drive technology, what everybody worried most is that safety problem and natural gas explode in atmosphere, as carried out, in air gas-lift production process, explosive incident occurred, liquefied gas blast is also more common in daily life, so worry very much the safety problem of air injection.Most people only sees the aerial blast of natural gas, but low-temperature oxidation can be there is with crude oil (natural gas) in the oxygen do not understood in air, can there is low-temperature oxidation in fact all organic matters, spontaneous combustion, plastic ageing etc. as coalfield are all because the reason of low-temperature oxidation reaction.
After learning that crude oil also low-temperature oxidation can occur, the air injection displacement of reservoir oil will be carried out in some oil fields, when carrying out safety demonstration, normally room is carried out indoor low temperature oxidation experiment to survey reaching the time of safe oxygen concentration or is tried to achieve activation energy to predict by formula by experiment.Such time is very very long, and each oil reservoir will carry out an experiment, and in the demonstration whether air injection is feasible, the time is very very long, and pre-verification just needs hundreds of thousands unit as carried out indoor low temperature oxidation experiment, wastes time and energy expensive.If infeasible, then experiment fees is propped up from where is also a problem.In addition, due to understood by laboratory experiment inject stratum the oxygen of air and crude oil low-temperature oxidation after oxygen content reaction time of reaching safe oxygen limit value have that cost is high, workload is large, experimental period temperature is long, and due to the restriction such as experimental instrument and equipment, funds, can not each need the oil reservoir of air injection or air foam all to have the condition of carrying out laboratory experiment.
In order to address this problem, after present inventor carries out the injection air that monitors in network analysis and the field trial that grasps and underground crude oil generation low-temperature oxidation by the experimental data collected output gas oxygen content, carry out network analysis containing data such as oxygen monitoring time, oil reservoir subsurface temperatures.And both are contrasted, and quote the empirical formula that Arrhenius formula Arrhenius equation chemical reaction rate constant the most frequently used in Chemical Kinetics varies with temperature relation, obtain the rate equation that China's light oil reservoirs crude oil and oxygen react, by this formula, as long as know reservoir temperature, just can directly calculate the time reaching safe oxygen, not need to carry out indoor low-temperature oxidation experiment, save time and manpower, financial resources.Quick and convenient, simple.
The present invention contains oxygen monitor value, oxidization time and temperature data process according to domestic and international low-temperature oxidation reaction laboratory experiment and mining site air injection (air foam) test, obtain reservoir temperature and low-temperature oxidation reaction rate empirical formula, apply this formula and can predict quickly and easily under different reservoir temperature.After the oxygen generation low-temperature oxidation of the air of light crude oil and injection is reacted, oxygen in air reaches the time of safe oxygen, thus supplements stratum energy for air injection, air foam and improve the selection of recovery ratio oil reservoir, constructure scheme preferably and in the construction of mining site air injection, carry out safe precaution measure provide foundation.The experimental study of crude oil low-temperature oxidation lab and field air injection shows, crude oil low-temperature oxidation speed follows Arrhenius empirical formula, and reservoir temperature is higher, and reaction rate is faster.
The present invention is obtained by domestic and international crude oil low-temperature oxidation in-house laboratory investigation and the research of air injection field test analysis on monitoring result.By crude oil low-temperature oxidation laboratory experiment interpretation of result research, find that crude oil low-temperature oxidation speed and temperature relation follow Arrhenius empirical formula i.e. exponentially relation; By analyzing and researching to monitoring the data such as output gas oxygen content, reaction time, formation temperature in air injection (Air-foam) field test, find oxidation rate (keto consumpting speed) and reservoir temperature relation also exponentially relation, follow Arrhenius empirical formula equally, different light oil reservoirs crude oil low-temperature oxidation speed and oil property, rock property have nothing to do, only relevant with reservoir temperature.As long as therefore know reservoir temperature, just can predict crude oil low-temperature oxidation speed (keto consumpting speed), thus after can predicting gas injection quickly and easily, output gas reaches the safe oxygen time.
The derivation of equation is specific as follows:
1, domestic and international crude oil low-temperature oxidation in-house laboratory investigation
By to domestic and international crude oil low-temperature oxidation in-house laboratory investigation and showing, with the rising of temperature, oxidizing reaction rate exponentially rises regularly, namely the relation of low-temperature oxidation speed and temperature all follows Arrhenius empirical formula, by to Central Plains, triumph, tell 5 crude oil low-temperature oxidation laboratory experiment result datas analysis and research such as Kazakhstan, Indonesia H oil field, find the rising with temperature, oxidizing reaction rate K exponentially rises regularly, follows Arrhenius empirical formula:
K＝k
0e
-Ea/RT(1)
K in formula (1)
0and E
abe two empiricals, have certain physical significance.K
0for pre-exponential factor, be also called frequency factor, its unit is identical with k.Ea is activation energy, and unit is Jmol-1; R is gas constant; T is thermodynamic temperature, and unit is K.
Are taken the logarithm in formula (1) both sides,
lnK＝-Ea/RT+lnk
0(2)
Second step: experimental data example 1 verifies Arrhenius empirical formula.Breathing out the analysis of Shanshan Oil Field acceleration calorimeter low-temperature oxidation Data Processing in Experiment to telling, obtaining low-temperature oxidation speed and temperature dependence.
Tell the low-permeability oil deposit crude oil underground viscosity of breathing out Shanshan Oil Field and be less than 1mPa? s, reservoir temperature 85 DEG C, reservoir pressure 24MPa. adopt and accelerate calorimeter experiment, the oxygen demand under mensuration different temperatures in the unit volume crude oil time.Laboratory measurement 85 DEG C (reservoir temperatures), 120 DEG C, 150 DEG C, 180 DEG C, 230 DEG C, oxidation rate during 250 DEG C of situations, result is as shown in table 1.Experimental result shows, under reservoir temperature, oxygen wear rate is low, and along with the rising gradually of temperature, OUR is accelerated, and when temperature reaches about 250 DEG C, crude oil and air can form combustion reaction, and oxidation rate is accelerated greatly, are 100 times of initial temperature.
Table 1
The oxygen consumption of oxidation reaction per unit oil-sand under Shanshan Oil Field crude oil different temperatures breathed out by table 1 for telling, make temperature and reaction rate curve as shown in Figure 3 by the process of his-and-hers watches 1 experimental data, tell that to breathe out Shanshan Oil Field crude oil low-temperature oxidation reaction rate regression formula as follows:
lnK＝-5886.6/T+16.94 (3)
Coefficient R
2=0.9491
Formula (3) turns to exponential form:
K＝2.27×10
7e
–5886.6/T(4)
(4), in formula: K-oxidizing reaction rate, unit is Nml.ml
-1.d
-1; T-thermodynamic temperature, unit is K.
3rd step: experimental data example 2 verifies Arrhenius empirical formula.The analysis of 204 pieces of crude oil static state constant-temperature oxidation reaction Data Processing in Experiment is sought to the pure beam of triumph, obtains low-temperature oxidation speed and temperature dependence.
Utilize core and the crude oil sample crude oil static state constant-temperature oxidation reaction experiment at different temperature of battalion 204 pieces, the depletion rate of test oxygen.(note: keto consumpting speed is defined as unit interval internal consumption 1% oxygen content, identical with oxidation rate physical significance, but unit is different, laboratory or on-the-spot test oxygen content and the reaction time all very convenient, it is on-the-spot common method, being oxidized the different of (reaction) speed to represent to test from laboratory standard, being defined as keto consumpting speed in the present invention)
Seek the experimental result of keto consumpting speed under 204 pieces of crude oil static oxidization different temperatures as shown in table 2.
| Temperature/DEG C | 85 | 120 | 140 | 160 | 180 | 200 |
| Thermodynamic temperature/K | 358.15 | 393.15 | 413.15 | 433.15 | 453.15 | 473.15 |
| Keto consumpting speed/1%/h | 0.066 | 0.22 | 0.605 | 1.619 | 3.291 | 5.573 |
Table 2
By to after experimental result data process, to keto consumpting speed mapping under different temperatures, obtain temperature and keto consumpting speed relation as shown in Figure 4, crude oil low oxidation temperature and keto consumpting speed regression formula as follows:
lnVo＝-6820.1/T+16.127 (5)
Coefficient R
2=0.9885
Formula (5) turns to exponential form:
Vo＝1.01×10
7e
–6820.1/T(6)
(6), in formula: Vo-keto consumpting speed, unit is 1%/h; T-thermodynamic temperature, unit is K.
4th step: field test data is compiled.Collect the reservoir temperature in the different oil reservoir of domestic each air injection field test, the time after injection air and oil well output gas composition analysis result, obtain oxygen content in output gas, temperature, reaction time data.
By compiling oxygen content monitoring result in different time points oil well casing output gas component after 5 air injections such as domestic grand celebration, Baise, prolongation and Central Plains or air foam field test reservoir temperature, air injection, to obtain in output gas content oxygen amount lower than oxygen consumption speed in crude oil low-temperature oxidation reaction under 3% (safe oxygen concentration) time and reservoir temperature and keto consumpting speed data as shown in table 3.
Table 3
5th step: field test data analyzing and processing, finds the rule between oxidation rate and temperature.The temperature obtained in field test, time, oxygen content data are processed, the relation between analysis and research temperature and keto consumpting speed (oxidation rate).
In air, oxygen content is 21% at normal atmospheric pressure, due to inject air in the earth formation with crude oil generation low-temperature oxidation, by required time when oxygen content is 3% in output gas in his-and-hers watches 3 can calculate oxidation keto consumpting speed (low-temperature oxidation speed).
Keto consumpting speed V
o=(21-3)/t (7)
In formula (7): V
ofor keto consumpting speed, unit 1%/h (1% oxygen content/hour); T is the reaction time, and unit is h (hour).
In order to crude oil low-temperature oxidation keto consumpting speed after studying different light oil reservoirs mining site air injection and temperature relation whether with tell breathe out Shanshan Oil Field, the pure beam of triumph seeks the crude oil low-temperature oxidation laboratory experiment temperature such as 204 pieces and oxidation reaction length velocity relation has identical rule.In order to the comparativity of data, convert reservoir temperature unit, reservoir temperature unit adopts Kelvin.Result is as shown in table 4 afterwards for reservoir temperature and keto consumpting speed relation de process.
Table 4
In his-and-hers watches 4 after 5 different oil reservoir injection air, in crude oil low temperature oxidization process, keto consumpting speed (oxidation rate) mapping under reservoir temperature, obtains temperature and the keto consumpting speed relation curve of good relationship, as shown in Figure 1.
Mining site air injection test temperature and keto consumpting speed regression formula are:
LnV
O＝-4732.6/T+10.963 (8)
Coefficient R
2=0.956
Formula (8) turns to exponential form:
V
O＝5.77×10
4e
-4732.6/T(9)
In formula (9): V
o-keto consumpting speed, unit is 1%/h; T-thermodynamic temperature, unit is K.
6th step: application mining site air injection test temperature and keto consumpting speed regression formula, can predict the low-temperature oxidation keto consumpting speed (oxidation rate) under different reservoir temperature, thus can predict that different reservoir temperature is issued to the safe oxygen time.
That injects air is generally 21% containing oxygen, and safe oxygen value be high limit with 2.5%, and applying equation (9) and can reach safe oxygen number of days and predicts the outcome as shown in table 5 keto consumpting speed under different temperatures.
Table 5
According to table 5 keto consumpting speed with reach safe oxygen time (d, sky) data and obtain Fig. 5.
In his-and-hers watches 5 reservoir temperature with reach safe oxygen time data and process, oxygen content in prediction output gas can be obtained and reach safe oxygen (oxygen content is 2.5%) time formula and be:
y＝1.336×10
-5e
4732.6/T(10)
(10), in formula: Y-reaches safe oxygen required time, unit is d (unit is that is 24 hours, sky, mining site is convenient to timing and operation with sky, need not be accurate to second); T-reservoir temperature, the unit constant that to be K, e be in mathematics in natural logrithm, its value approximates 2.718281828.
As long as there is the temperature needing air injection oil reservoir, after just can applying the oxygen generation low-temperature oxidation that this formula (10) can predict after air injection in crude oil and air, corresponding oil well output gas reach safe oxygen limit value required time (my god).
After obtaining required time, the application injection direct monitoring method of tracer or oil reservoir injection are adopted dynamic-analysis method and are determined to inject fluid subsurface detention time (inject fluid and arrive the withdrawal well time), contrast in subsurface detention time and required oxidation time by injecting fluid, can accurately know inject air oxygen before reaching production well whether within the scope of safe oxygen.The corresponding safe precaution measure of extraction is wanted, to guarantee air injection, air foam construction safety for different situations.
During concrete use, as shown in Figure 2, an embodiment of the inventive method is as follows:
The female 10 blocks of oil reservoirs structure in that female oil field is positioned at Eastern Depression of Baise Basin, read to organize at Eogene the fault block oil reservoir stratigraphic dip 10 ~ 20 ° that monocline background that stratum east northeast inclines is formed by tomography cutting, reservoir reads group two sections of basal sandstones for that, belongs to shallow gyittja.Average pore 19.1%, average air permeability 106.0 × 10
-3μm
2, oil saturation 63.0%.Oil reservoir buried depth 826 ~ 920m, midpoint of pay zone is 873m.
The first step: get crude oil sample and measure relative oil density
To female 10 pieces 6 mouthfuls well wellhead crude oil samples, carry out crude oil property analysis, analysis result is average ground relative oil density 0.8412, average viscosity 16.18mPa.s, 30 DEG C, freezing point.Oil property is better, has the features such as low-density, low viscosity and high-solidification point.Female 10 pieces of crude oil property analysis results are as shown in table 6,
Table 6
Second step: determine whether as light oil reservoirs
Female 10 pieces of relative oil densities are 0.8412, are less than 0.852, are light crude oil, and female 10 blocks of oil reservoirs are light oil reservoirs, can apply predictor formula of the present invention.
3rd step, actual measurement oil reservoir individual well formation temperature
Ground temperature temperature is recorded to female 10 pieces of 6 mouthfuls of down-hole bottom hole temperature bombs, as shown in table 7.
Table 7
4th step, determines reservoir temperature
By carrying out statistical regression analysis to 6 mouthfuls of well temperature and well depth data, obtain temperature and well depth relation formula t=0.0379h+24.966.Can find from formula, female 10 pieces of geothermal gradients are 3.8 DEG C/100m.In the middle part of female 10 blocks of oil reservoirs, the degree of depth is 873m, and substitution temperature and well depth relation formula determination reservoir temperature are 58.05 DEG C, and being scaled thermodynamic temperature is 331.2k.Female 10 pieces of geothermal gradient curves as shown in Figure 6.
5th step, utilizes formula (10) to calculate and reaches the safe oxygen value reaction time
According to female 10 pieces of reservoir temperatures be 331.2K substitute into formula y=1.336 × 10
-5e
4732.6/T, reaching the good time number of days of the required reaction of safe oxygen is 21.46 days.
6th step, determines to inject fluid in the subsurface detention time
Female 10 pieces of air injection wells are female 16 wells, for determining to inject fluid in the subsurface detention time at female 16 wells, different tracer is injected to this well oil jacket, the female 16-1x of corresponding oil well, female 16-2 and female 18x well have carried out production fluid sampling and tracer content monitoring, female 16-1x and female 16-2 well have monitored the tracer of casing section, and female 18x well has monitored the tracer of oil pipe section.
Receiving time to peak is 41 ~ 46 days.Female 16 well-group tracer outputs and interpretation results as shown in table 8.
Table 8
In plane, female 16 well groups inject water waterline direction of propulsion as shown in Figure 7.It is the fastest to female 18x well direction fltting speed that monitoring result shows that female 16 well oil pipe sections inject water, and female 16 casing sections injection water are the slowest to female 16-2 well direction fltting speed.
7th step, compares and injects fluid in subsurface detention time and reach the safe oxygen reaction time
It is 41 ~ 46 days in the subsurface detention time that female 16 wells inject water, and it is 21.46 days that the oxygen of injection air reacts the reaction time reaching safe range value, and the oxygen injecting air is greater than reaction required time in the subsurface detention time, pacifies safety of giving vent to anger.
7th step, air injection, air foam safe precaution measure
Female 10 pieces of air injection foams, do not need to increase special safety device at surface gathering system.But perfectly safe for ensuring safety, producing well still needs carry out 2 casing gas containing oxygen monitoring with Portable monitor every day, understands output gas oxygen content, once find has channeling closing well immediately.At producing well scene, " in 20m, No Open Flames " warning mark is set.
On November 16th, 2012 is after female 16 wells start air injection foam, started timing every day Portable monitor November 23 and casing gas is carried out containing oxygen monitoring to well group oil well female 16-1x well, female 18 wells, to on January 11st, 2013, the oxygen that contains of two mouthfuls of wells is 0.2%, has no the air of injection from producing well extraction.On January 10th, 2013, female 16-2 well started the air (air is 55 days in the subsurface detention time) seeing injection, and the air of injection and crude oil there occurs low-temperature oxidation and reacts, and had the rear significant product C O output of oxidation.
Corresponding oil well has carried out output gas and has regularly sampled, and carry out the analysis of gas-chromatography precise quantitative, it is as shown in the table for result.Output gas contains oxygen all within the scope of safe oxygen.Female 10 pieces of female 16 well group air injection foam production casing gas proximate analysis are as shown in table 9, and therefrom can find out, female 10 pieces of female 16 well air injection foam test results show, low-temperature oxidation rate prediction result is actual consistent with scene.
Table 9
That is predicted by method of the present invention is issued to safety time at different reservoir temperature, can be used for optimizing air injection (air foam) reservoir engineering scheme, control the air holdup time in the earth formation, optimize and inject and productions, gathering system engineering proposal, optimize injection construction parameter, containing oxygen monitoring system with enter well, producing well management system.
The air of injection can be made to be detained oxidation in the earth formation according to existing technical condition and method and reach the safety content of oxygen time, according to formula, determine required reservoir temperature conversely, thus for selecting suitable air injection oil reservoir to provide scientific basis.
The present invention calculates the time being issued to safe oxygen concentration at different reservoir temperature quickly and easily.Work out pre-blast protection measure for the selection and demonstration of air injection (Air-foam) oil reservoir, air injection reservoir engineering schematic design, air injection inject engineering proposal, ground surface works scheme, Field design, on-site construction operations, the monitoring of producing well output gas and safety management system reliable basis is provided.The method can be used for " three is high " supplementary stratum energy relevant with air injection and raising recovery ratio fields such as oil reservoir development later stage air drives, Air-foam drives in oil exploitation.Also can be used for hypotonic, the special law quality reservoirs such as hypotonic due to reservoir properties difference cannot water filling and because region reason is without the air injection makeup energy of water filling water source oil reservoir.
To this method solve in oilfield exploitation air injection makeup energy and improve in recovery efficiency technique, the prediction of safe oxygen required time is reached after the reaction of crude oil low-temperature oxidation, for in air injection (air foam) work progress, the reliable foundation of the science that provides of effective prevention security incident, solves the safety problem that everybody worries.By the recovery ratio of the development degree and " three high " oil reservoir that improve the low-grade reserves of China significantly after enforcement, thus improve the crude output of China significantly, have a extensive future.
The empirical data that the measured result that the present invention is reacted by the oxygen generation low-temperature oxidation that domestic air (air foam) drives in-place oil and injection air in field test is formed can predict the time being issued to safe oxygen concentration at each reservoir temperature quickly and easily, by injection fluid the comparing in the subsurface detention time obtained with methods such as tracer methods, reliable basis is provided for effectively working out safety precautions scheme, on-the-spot preventive action and management system, use manpower and material resources sparingly, improve the controllability of safety precaution.
Technique scheme is one embodiment of the present invention, for those skilled in the art, on the basis that the invention discloses application process and principle, be easy to make various types of improvement or distortion, and the method be not limited only to described by the above-mentioned detailed description of the invention of the present invention, therefore previously described mode is just preferred, and does not have restrictive meaning.
Claims (7)
1. light oil reservoirs crude oil low-temperature oxidation rate prediction and a safe precaution method, is characterized in that: said method comprising the steps of:
The first step: measure relative oil density;
Second step: determine whether as light oil reservoirs, in this way, then proceeds to the 3rd step;
3rd step, actual measurement oil reservoir individual well formation temperature;
4th step, determines reservoir temperature;
5th step, utilizes formulae discovery below to reach the safe oxygen value reaction time, namely achieves oxidation rate prediction:
y＝1.336×10
7e
4732.6/T
Wherein, y is for reaching the safe oxygen value reaction time, and unit is sky, and T is the reservoir temperature that the 4th step is determined, the unit constant that to be K, e be in mathematics in natural logrithm;
6th step, determines to inject fluid in the subsurface detention time;
7th step, compares and injects fluid in subsurface detention time and reach the safe oxygen value reaction time, is greater than and reaches the safe oxygen value reaction time, then output gas safety, regularly carry out output gas containing oxygen monitoring at well head if inject fluid in the subsurface detention time; If injection fluid was less than in the subsurface detention time reach the safe oxygen value reaction time, then there is hidden danger in output gas, proceeds to the 8th step;
8th step, carries out the safety precaution of beam body.
2. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 1 and safe precaution method, it is characterized in that: the described first step is achieved in that and obtains crude oil sample at the wellhead of the oil reservoir oil well that need carry out air injection, then relative oil density mensuration is carried out to crude oil sample, obtain relative oil density.
3. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 2 and safe precaution method, is characterized in that: described second step is achieved in that
Judging whether the relative oil density that the first step records is less than or equal to 0.852, in this way, is then light oil reservoirs.
4. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 3 and safe precaution method, is characterized in that: described 3rd step is achieved in that
Under lower going-into-well in the middle part of thermometer to each producing well and Injection Well oil reservoir, record downhole temperature or temperature gradient.
5. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 4 and safe precaution method, is characterized in that: described 4th step is achieved in that
The each well observed temperature obtained according to the 3rd step and well depth data carry out statistical regression analysis, obtain temperature and well depth relation formula;
Depth data in the middle part of oil reservoir is substituted into described temperature and well depth relation formula, determine oil reservoir middle portion temperature, and the unit of oil reservoir middle portion temperature is scaled thermodynamic temperature by Celsius temperature.
6. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 5 and safe precaution method, is characterized in that: described 6th step adopts one of two kinds of methods below to realize:
(1), direct method: inject tracer to water injection well, from corresponding oil well sampling monitoring tracer output, see the tracer peak of injection from oil well, be defined as injecting water and namely inject fluid in the subsurface detention time from the time of well arrival oil well;
(2), indirect method: determine to inject fluid at stratum fltting speed according to water filling current intelligence, determine that injecting fluid arrives the withdrawal well time according to inter-well distance.
7. light oil reservoirs crude oil low-temperature oxidation rate prediction according to claim 6 and safe precaution method, is characterized in that: described 8th step is achieved in that
According to injection fluid in subsurface detention time and the difference size reaching safe these two times in oxygen value reaction time, one or more safety measures below extraction in 5 kinds of measures:
1. and 5. (1) if the difference of two times is less than or equal to 10 days, then measure is adopted;
(2) if the difference of two times is greater than 10 days but be less than or equal to 20 days, then measure is adopted 1., 2. and 5.;
(3) if the difference of two times is greater than 20 days but be less than or equal to 30 days, then measure is adopted 1., 2., 3. and 5.;
(4) if the difference of two times is greater than 30 days, then 5 kinds of measures need all to adopt;
5 kinds of safety measures are:
1. preposition foam solution section 300m is increased
3within: before air injection, increase a preposition pure foam liquid section, foam solution section size is according to the difference of two times, and difference is larger, then preposition section of foam volume is larger;
2. control injection rate: compared with water filling, reduce injection rate, difference is larger, then injection rate reduces more;
3. temporarily close down producing well: the corresponding line oil well closing well of air injection or air foam well, the closed-in time is the difference of two times;
4. newly-built flooring-safe facility: build emptying pipe support height emptying casing gas; Production fluid enters uncovered fluid reservoir, and make gas emptying after gas emptying or air inlet liquid/gas separator, production fluid enters closed gathering system again;
5. strengthen the monitoring of output gas oxygen content: encrypt a line producing well casing gas containing oxygen monitoring, with Portable monitor or use on-line computing model Real-Time Monitoring, once find to exceed standard containing oxygen in output gas, close down oil well immediately and suspend Injection Well and construct.
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