CN117418806A - Flow optimization control method for high-pressure gas well ground pipeline - Google Patents
Flow optimization control method for high-pressure gas well ground pipeline Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 54
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 174
- 239000003345 natural gas Substances 0.000 claims abstract description 104
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B34/00—Valve arrangements for boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
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- E21B47/00—Survey of boreholes or wells
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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Abstract
The invention discloses a flow optimization control method of a high-pressure gas well ground pipeline, which comprises the following steps: step S1, establishing a multi-stage throttling temperature and pressure calculation model of a high-pressure/ultrahigh-pressure gas well ground pipeline; s2, calculating a multi-stage throttling series and a corresponding caliber; s3, calculating multi-stage throttling natural gas flow and adjusting caliber distribution pressure difference; and S4, inputting the calculated parameters to each stage of throttle valve to realize remote automatic control. The invention avoids the situation that the ground pipeline of the high-pressure ultrahigh-pressure gas well test operation is damaged by ultrahigh pressure, and carries out multi-throttle linkage adjustment according to real-time measured data; meanwhile, enough pressure drop is ensured to ensure the stable operation of the separator and the throttle valve, and theoretical support is provided for optimizing the natural gas flow and increasing the yield.
Description
Technical Field
The invention relates to the technical field of natural gas development of high-pressure/ultrahigh-pressure gas wells, in particular to a flow optimization control method for a ground pipeline of a high-pressure gas well.
Background
With the continuous deep development of natural gas exploration, high-temperature high-pressure high-yield gas wells are more and more common, in the production process of high-pressure/ultrahigh-pressure gas well ground test operation, the maximum well closing pressure of a well head is sometimes up to 100MPa, the rated pressure of a separator used by a ground pipeline is often lower than 10MPa, and in order to prevent ultrahigh-pressure natural gas fluid from entering separation equipment to bring serious potential safety hazards, the ground test pipeline needs to be throttled and depressurized, so that the pressure of the natural gas fluid is reduced below the rated working pressure of the separation equipment.
In general, in medium-low pressure environment, the required pressure reduction requirement can be met by using a single throttling device, but for a high-pressure/ultrahigh-pressure gas well, the excessively high pressure difference is extremely easy to cause the damage of throttling equipment and cause throttling failure, in this case, multistage throttling is required to be additionally arranged to gradually reduce the pressure so as to meet the pressure requirement of a separator, in the ground test process, the prior art usually only uses the pressure drop limit borne by a single throttling valve as the setting basis of throttling caliber and throttling stage number, the conditions of unreasonable distribution of very large caliber of bearing pressure drop of the former stage, very small caliber of bearing pressure drop of the latter stage and very large caliber of pressure drop of the latter stage can occur in some pressure environments, and in this way, the situation that the flow is greatly reduced due to the excessively small caliber of the single throttling valve can be caused
Therefore, in the multi-stage throttling operation flow of the high-pressure/ultra-high-pressure gas well ground test operation, the invention can calculate and redistribute the caliber and the pressure drop of each stage of throttling device to maximize the final total flow, automatically distribute the pressure difference according to real-time data, schedule each throttling valve at any time to adjust the opening, and provide basis for safe production and stable operation of the ultra-high-pressure gas well ground test operation flow and increase production and efficiency.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a flow optimization control method for a high-pressure gas well ground pipeline. The book is provided with
The scheme of the invention is that
A flow optimization control method of a high-pressure gas well ground pipeline comprises the following steps:
step S1, establishing a multi-stage throttling temperature and pressure calculation model of a high-pressure/ultrahigh-pressure gas well ground pipeline;
s2, calculating a multi-stage throttling series and a corresponding caliber;
s3, calculating multi-stage throttling natural gas flow and adjusting caliber distribution pressure difference;
and S4, inputting the calculated parameters to each stage of throttle valve to realize remote automatic control.
Specifically, step S1 specifically includes: according to the wellhead temperature and pressure obtained through initial measurement, the fluid change of the whole ground pipeline is regarded as an adiabatic process, the rated pressure condition of the separator is regarded as the final pressure of the ground test pipeline, so that the pressure drop required by the throttling process is obtained, and the temperature and pressure fields of the ground pipeline and the front and the rear of the throttle valve are established.
Specifically, the pressure drop calculation process includes the following sub-steps:
step S11, under the subcritical state, calculating the relation between the natural gas flow and the pressure ratio of the upstream and downstream of the throttling, wherein the calculation formula is,
in step S12, in the critical state, the relation between the natural gas flow and the pressure ratio of the upstream and downstream of the throttling is calculated, wherein the calculation formula is,
step S13, calculating the throttling pressure drop of the gas flowing through the fixed oil nozzle, wherein the calculation formula is,
wherein Q is g -natural gas current state flow, 10 4 m 3 /d; q-natural gas production (under standard conditions); p (P) 1 -pressure upstream of the restrictor, MPa; p (P) 2 -a pressure downstream of the restrictor; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 -the natural gas compression factor under corresponding temperature and pressure conditions; gamma ray g -natural gas relative density; k—natural gas adiabatic index; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma-natural gas relative density;
specifically, in step S2, when the flow state of the gas flowing through the fixed choke reaches the critical flow state, the pressure drop generated by throttling will not affect the actual yield of the natural gas any more, and the natural gas fluid flow is only related to the diameter of the choke, so that the caliber of the choke can be reasonably calculated by distributing the pressure on the premise of ensuring that the pressure drop is enough for safe production, and the calculation formula is as follows:
wherein Q is sc Natural gas production, 10 4 m 3 /d；P 1 ，P 2 -pressure upstream and downstream of the restrictor, MPa; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma ray g -natural gas relative density.
Specifically, the method also comprises the step of calculating the erosion wear of the throttle manifoldThe step (1) comprises gradually increasing with the decrease of the pressure before throttling according to the theoretical calculation value of the erosion rate as the standard, maintaining a stable flow rate after the fluid reaches the critical rate, increasing the calculated erosion rate continuously, and slowing down the theoretical rate while increasing, wherein the actual flow rate is always lower than the erosion flow rate, namely the safe critical rate V 2 The critical rate V 2 The calculation formula of (c) is as follows,
specifically, in step S3, the natural gas flow under the corresponding throttle valve is calculated according to the calculated number of throttle stages and the throttle caliber, and then the pressure drop and caliber of each stage of the multi-stage throttle are adjusted on the premise of guaranteeing the stability of the total pressure difference and the single-stage throttle pressure difference until the total natural gas flow reaches the maximum value, namely the flow maximization optimization method of the multi-stage throttle of the high-pressure/ultra-high-pressure ground test pipeline.
Specifically, step S4 includes the sub-steps of:
s41, reassigning the throttling caliber d to achieve the optimized flow under the corresponding working condition;
step S42, the obtained parameters are sent to opening controllers of all levels of throttle valves in real time through a unified controller and a circuit, and the opening controllers determine the required caliber and the needle valve descending degree;
step S43, the opening controller controls the electromagnetic valve, the communication gas path fills high-pressure gas into the closed cylinder, the piston is pushed and the return spring is compressed, the entering depth of the throttle needle valve is lifted, a sensor at the position of the cylinder head at the tail end of the needle valve can record the current entering depth of the needle valve in real time, and the sensor feeds back to the electromagnetic valve to be closed automatically after the condition is met;
the method also comprises the step of reducing the caliber, and specifically comprises the following steps: when the pipeline fluid pressure change needs to be reduced in caliber, the electromagnetic valve is used for controlling the gas in the evacuation cylinder, the reset spring is used for pushing the needle valve to reduce the throttling caliber, the requirement on pipeline throttling pressure drop is met, and the multistage throttling simulation calculation real-time remote control can be performed at any time in the natural gas production process.
A computer program product comprising a computer program which, when executed by a processor, implements a method of optimizing control of flow of a high pressure gas well surface pipeline as claimed in any one of claims 1 to 7.
A computer-readable storage medium storing a computer program which, when executed by a processor, implements a flow rate optimization control method of a high pressure gas well surface pipeline according to any one of claims 1 to 7.
The invention has the beneficial effects that:
1. the invention avoids the condition that the ground pipeline of the high-pressure ultrahigh-pressure gas well test operation is damaged by ultrahigh pressure, and carries out multi-throttle linkage adjustment according to real-time measured data
2. The invention ensures enough pressure drop to ensure the stable operation of the separator and the throttle valve, and simultaneously provides theoretical support for optimizing the natural gas flow and increasing the yield.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a technical roadmap of the invention;
FIG. 2 is a graphical representation of the relationship of orifice size to flow rate in accordance with the present invention;
FIG. 3 is a schematic diagram of wellhead pressure versus maximum natural gas flow rate in accordance with the present invention;
FIG. 4 is a schematic diagram of wellhead temperature versus maximum natural gas flow rate in accordance with the present invention;
FIG. 5 is a schematic diagram of wellhead temperature pressure versus maximum natural gas flow in accordance with the present invention;
FIG. 6 is a schematic diagram of the real-time flow maximization control of the complete set of ground test lines of the present invention;
FIG. 7 is a schematic diagram of an automatically adjusted throttle model of the present invention;
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The technical scheme of the present invention is selected from the following detailed description in order to more clearly understand the technical features, objects and advantageous effects of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention and should not be construed as limiting the scope of the invention which can be practiced. All other embodiments, which can be made by a person of ordinary skill in the art based on the embodiments of the present invention without making any inventive effort, are within the scope of the present invention.
The invention provides a prediction method of multi-stage throttling in high-pressure/ultra-high-pressure gas well ground test operation, which comprises the following steps:
s1: establishing a multi-stage throttling temperature pressure calculation model of a high-pressure/ultrahigh-pressure gas well ground pipeline
Taking the wellhead temperature pressure obtained through initial measurement as a ground throttling initial temperature pressure condition, taking the fluid change of the whole ground pipeline as an adiabatic process, taking the rated pressure condition of the separator as the final pressure of a ground test pipeline, obtaining the pressure drop required by the throttling process, and establishing a temperature pressure field before and after the ground pipeline and a throttle valve;
s2: calculating the multi-stage throttling series and the corresponding caliber according to the required pressure drop
According to the critical flow condition of the fluid and the throttling pressure drop principle as the basis, a throttling pressure drop model is established, the calculated temperature pressure field is substituted into the model to calculate the needed throttling caliber, whether the throttling meets the safe pressure drop condition is judged according to critical erosion, if not, the throttling level is increased, and the calculation process is repeated until the pressure difference of a single throttling model accords with the pressure difference limit of a throttling valve;
s3: calculating multi-stage throttling natural gas flow and adjusting caliber distribution pressure difference to achieve maximum flow
According to the calculated throttling level number and throttling caliber, natural gas flow under the corresponding throttling valve is calculated, then the pressure drop and caliber of each stage of the multi-stage throttling are regulated on the premise of guaranteeing the stability of the total pressure difference and the single-stage throttling pressure difference, and the flow maximization optimization method of the multi-stage throttling of the high-pressure/ultrahigh-pressure ground test pipeline is obtained until the total natural gas flow reaches the maximum value
S4: remote automatic control is carried out by inputting the calculated parameters to the throttle valves of each stage
The obtained flow maximization caliber parameters are distributed to opening controllers (PLC) of all throttle valves, the needle valve descending degree is adjusted through a remote controller, calculation simulation and redistribution can be carried out at any time according to data measured in real time by pipelines in the process, and the flow is kept in the maximization state on the premise of ensuring the safety and stability of the ultrahigh-pressure ground pipelines.
Throttle physical model
The high pressure/ultra-high pressure gas well ground flow throttling oil nozzle adopts an adjustable needle valve oil nozzle, and is characterized by being convenient to adjust, collecting related information such as throttling caliber and the like, achieving the purpose of controlling the throttling oil nozzle caliber by adjusting the needle valve in-going distance, playing a key role in controlling natural gas pressure difference and oil gas yield in combination in the natural gas production process, compared with a fixed oil nozzle, the needle valve can be operated more easily when stratum pressure fluctuates and the valve is opened for increasing production, and well closing pressure relief is not needed to be replaced.
The required parameters such as the throttling level and the throttling caliber are obtained through calculation of critical erosion and throttling pressure drop, then the optimal calculation of throttling flow is carried out, the obtained optimal caliber is obtained, the electromagnetic valve is activated through the opening controller to charge air in the cylinder, the piston is pushed to achieve the opening control of the valve core of the needle valve, and the electromagnetic valve is regulated by the position sensor on the cylinder cover.
Critical fluid flow conditions
The flow of the fluid mixture through the choke is of the nozzle type, and the flow regime is generally considered to be an adiabatic expansion process for analytical treatment, and in general the flow of natural gas in the pipeline is divided into two types: critical and subcritical flows.
The parameters before natural gas throttling of the ground test pipeline are as follows: pressure (P) 1 ) Temperature (T) 1 ) And flow rate (V) 1 ) The method comprises the steps of carrying out a first treatment on the surface of the The various parameters behind the throttle are; p (P) 2 、T 2 And V 2 . The throttling process is generally considered to be isentropic adiabatic expansion, so the pressure is reduced (P 2 ＜P 1 ) The flow speed is increased (V 2 ＞V 1 ) The temperature decreases (T 2 ＜T 1 ) The pressure ratio before and after throttling under critical flow conditions is given by:
(1)
wherein: p1-pressure before throttling, MPa; p2-post-throttling pressure, MPa; k is specific heat, dimensionless;
in the natural gas adiabatic throttling process, the pressure of natural gas is converted into fluid kinetic energy, the flow speed is increased, the pressure is reduced, the irreversible pressure drop caused by throttling is larger along with the smaller caliber of a throttling nozzle, the flow speed obtained after throttling is also larger, but the fluid speed obtained by the method has an upper limit, when the ratio of the pressures at the upstream and downstream of the throttling valve reaches a certain value, the flow speed is close to the sound velocity, at the moment, the flow speed is not increased any more when the throttling pressure difference is increased, and the sound wave or pressure wave propagation speed is kept. This is the so-called critical flow state of the nozzle.
Throttle process pressure drop calculation
When the fluid flows through the throttle, the sudden reduction of the caliber of the natural gas fluid pipeline can greatly convert the pressure energy of the natural gas into kinetic energy, so that the flow speed of the fluid is suddenly and greatly increased, and a pressure difference is generated before and after the throttle nozzle. According to the principle of isentropic expansion during natural gas throttling, the relationship between the natural gas flow and the pressure ratio of the upstream and downstream of the throttling is as follows in a subcritical state:
wherein: q (Q) g Natural gas flow, 10 4 m 3 /d；P 1 -pressure upstream of the restrictor, MPa; p (P) 2 -a pressure downstream of the restrictor; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 -the natural gas compression factor under corresponding temperature and pressure conditions; gamma ray g -natural gas relative density; k—natural gas adiabatic index;
for critical flow, based on critical pressure ratio
Flow rate Q of natural gas in known gas well g Temperature T before throttling 1 And pressure P 1 At the time, the throttled pressure P can be determined 2 Thereby calculating the throttle pressure drop of the gas flowing through the fixed nozzle.
Wherein: p (P) 1 ，P 2 -pressure upstream and downstream of the restrictor, MPa; t (T) 1 -temperature upstream of the restrictor, K; Q-Natural gas yield (under Standard State), 10 4 m 3 /d; d-diameter of the orifice of the restrictor, mm; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma-natural gas relative density;
the process of throttling the surface pipeline not only reduces the pressure of the natural gas fluid, but also limits the flow rate of the natural gas. Under certain inlet pressure conditions, when the outlet pressure drops to the critical pressure, the natural gas velocity in the nozzle reaches the local sonic velocity. At this time, when the pressure difference further increases, the downstream flow does not affect the upstream flow any more, and this phenomenon is called a locking phenomenon of the nozzle tip. When the inside of the oil nozzle reaches a critical flow state, the flow in the oil nozzle is not changed on the premise of not adjusting the aperture.
The caliber of the throttle nipple of the gas well is determined mainly according to the temperature and pressure before and after the throttle of the gas well. When the flowing state of the gas flowing through the fixed choke reaches the critical flowing state, the pressure drop generated by throttling does not influence the actual yield of the natural gas any more, and the natural gas fluid flow is only related to the diameter of the choke, so that the caliber of the choke can be reasonably calculated through distributing the pressure on the premise of ensuring the pressure drop to be safe and production, and the caliber of the choke is obtained by the following steps:
wherein: q (Q) sc Natural gas production, 10 4 m 3 /d；P 1 ，P 2 -pressure upstream and downstream of the restrictor, MPa; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma ray g -natural gas relative density;
erosion wear of choke manifold
In the natural gas exploitation process, due to factors such as underground stratum rock debris crushing and the like, produced natural gas is often accompanied with a considerable degree of sand or other solid particles, when fluid carrying the solid particles enters a surface pipeline choke manifold, obvious erosion phenomenon is caused to a choke nipple, the erosion phenomenon of particles becomes more obvious as the pressure drop is larger and the flow speed is higher as the throttle caliber is smaller, and long-term high-pressure high-speed fluid with particles passes through the choke nipple manifold, so that serious abrasion is caused to a throttle valve and the inner wall of the manifold, and the risk such as leakage perforation and even puncture of the manifold is aggravated. At present, API RP 14E is mainly adopted as a fluid pipeline flow erosion design criterion, a calculation formula for predicting fluid erosion wear is provided, and critical erosion speed V e The definition is as follows:
V e ＝C/(ρ m ) 0.5 (6)
in ρ m Density of mixture, g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the C-an empirical constant;
for intermittent flow with non-negligible rock debris particle content, C is taken to 100, and continuous flow is taken to 120; for continuous flows where the cuttings content is not negligible and where the choke manifold takes anti-erosion measures, C is preferably 150.
The density of the gas-liquid two-phase mixture can be determined by the following empirical formula:
wherein: p-operating pressure, MPa; s is S l -specific gravity of the liquid under standard conditions, dimensionless; r is the gas-liquid ratio, dimensionless; t is the working condition temperature, K; s is S g -gas specific gravity under standard conditions (air=1); z-gas compression factor, dimensionless.
When the flow rate of the fluid increases to a critical erosion rate, the fluid erodes the restriction member, and the faster the flow rate, the more serious the erosion. The throttle valve is eroded by high-pressure fluid for a long time to cause serious abrasion to the throttle part, the pressure difference which can be born by the throttle part is influenced by factors such as the structure, the material, the fatigue degree and the like of the throttle part, and the longer the time is, the larger the pressure difference is, the larger the flow velocity is, and the higher the damage degree is.
For a given wellhead pressure, the gas well yield depends on the flow area of the throttle valve, when high pressure gas flows through the throttle valve, the pore canal is short, the flow speed is high, potential energy is not changed, and the gas well yield can be regarded as an adiabatic process, and then the flow stabilization flow energy equation can be written as:
solving to obtain:
flow velocity V after throttling 2 Is determined by
Wherein: v (V) 2 -post-throttle flow rate, m/s;T 2 -post-throttling temperature, K; p (P) 2 -post-throttling pressure, MPa; d, the caliber of the throttling oil nozzle is mm; z is Z 2 —T 2 And P 2 The gas compression coefficient under the condition is dimensionless.
According to the principle of the critical flow nozzle, after the fluid passes through the throttling part, p 2 ≤0.546p 1 (p 2 For throttled pressure, p 1 Pressure before throttling) the fluid flow rate reaches a critical flow rate. Regardless of the pressure change before and after throttling, as long as the critical flow rate is reached, the flow rate of the fluid is equal to the sonic velocity of the fluid at that temperature (sonic velocity at 15 ℃ C. Is 340m/s, and the flow rate of the fluid increases by 0.6m/s for every 1 ℃ C. Increase in temperature) at the point where the flow passage cross-sectional area is minimum.
FIG. 2 is a graph showing the calculated fluid flow rate distribution, the erosion rates of different calibers and pressures are predicted, the predicted flow rate of the fluid is mainly changed according to the change of the pressure difference, the predicted flow rate is gradually increased along with the reduction of the pressure before throttling according to the theoretical calculation value of the erosion rate as the standard, the calculated erosion rate is continuously increased when the fluid reaches the critical rate, and the theoretical rate is gradually reduced while the calculated erosion rate is increased, and the actual flow rate is always lower than the erosion flow rate, namely the safe critical rate.
Multi-stage throttle flow calculation
According to the wellhead temperature and pressure, the throttling caliber and the relative density of the natural gas, the relationship between the natural gas flow and the natural gas flow in the surface test flow pipeline is reflected as follows.
The relationship between wellhead pressure and maximum natural gas flow is shown in fig. 3, when the relative densities of the throttling caliber and the natural gas are constant, the maximum natural gas flow increases as the wellhead pressure increases, the two show obvious positive correlation, and the natural gas flow also increases as the wellhead temperature increases. When the temperature is constant relative to the natural gas density, the throttling caliber is increased, the maximum natural gas flow can be obviously increased, the allowable maximum natural gas flow difference under different calibers is larger, and the throttling caliber is a key factor influencing the natural gas flow in the throttling process. The natural gas relative density has less effect on the maximum flow rate of the natural gas, and the natural gas flow rate is smaller when the relative density is larger.
FIG. 4 is a graph of wellhead temperature versus natural gas flow. It can be seen from the figure that when the wellhead pressure is constant, the natural gas flow rate shows a tendency to slowly decrease as the wellhead temperature increases, the natural gas flow rate is lower instead as the temperature increases, and meanwhile, under the condition of temperature influence, the influence of the throttling caliber on the natural gas flow rate is great, compared with the relative density, the natural gas flow rate trend influence is smaller, but the natural gas flow rate difference under different relative densities is smaller.
From this, it can be calculated that, during the natural gas throttling process, the maximum natural gas flow rate will increase significantly according to the increase of the wellhead pressure, but will decrease slowly with the increase of the wellhead temperature, the natural gas flow rate will increase significantly with the increase of the throttling caliber, the natural gas flow rate will increase more when the relative density increases, but the higher natural gas relative density will make the natural gas flow rate smaller.
FIG. 5 is a graph of the flow rate change of the maximum natural gas flow rate under the influence of wellhead pressure and wellhead temperature, wherein the natural gas flow rate at low temperature and high pressure can be seen to be larger, and the caliber has a larger influence on the natural gas flow rate than the relative density.
ADVANTAGEOUS EFFECTS OF INVENTION
1. A multi-stage throttling temperature and pressure prediction model of a high-pressure/ultrahigh-pressure ground test pipeline is established based on wellhead temperature and pressure, the required pipeline pressure drop and the throttling progression are predicted according to rated pressure selected by a separator, and then the throttling caliber is calculated according to the critical flow judgment condition of a throttling choke and the erosion condition of a choke manifold as the standard
2. And (3) calculating the maximum flow of the natural gas under the working condition according to the calculated throttling series and caliber, optimizing the flow on the basis of ensuring enough throttling pressure drop and within the single-stage throttling erosion safety range, and calculating the corresponding throttling series and throttling caliber according to the optimized flow.
3. The parameters are transmitted to opening controllers of all levels of throttling devices, high-pressure gas is filled into a closed cylinder of the throttling devices by using electromagnetic valves so as to achieve the purpose of remotely adjusting the throttling caliber, and the optimal configuration can be calculated at any time according to pipeline sensors, and real-time adjustment or opening and closing can be completed.
Computing examples
The present invention is described and illustrated in terms of actual case analysis in conjunction with field cases.
Target well base information
To illustrate the object and advantages of the present invention, a high pressure high production gas well (called A1 well) in the north-west of the Sichuan is selected as an example for analysis, and the basic data of the A1 well are shown in table 1:
table 1 A1 well base parameters
| Parameter name | Numerical value | Parameter name | Numerical value |
| Natural gas density | 0.73g/cm 3 | Wellhead pressure | 64.2MPa |
| Natural gas relative density | 0.562 | Wellhead temperature | 56.2℃ |
| Critical temperature | 190.4K | Constant pressure specific heat | 46.44J/kmol·k |
| Critical pressure | 4.62MPa | Coefficient of heat transfer | 1.5W/m 2 ·k |
| Compression factor | 0.866 |
Multi-stage throttle prediction
According to the specification of the on-site separator, the pressure of the tail end of the ground pipeline needs to be controlled within 10MPa, and a total of two-stage throttling is obtained through calculation:
the first-stage throttling caliber is 12.53mm, the pre-throttling pressure is 64.2MPa, the post-throttling pressure is 34.88MPa, the erosion rate is 332.79m/s, the actual flow rate is 297.68m/s, and erosion cannot occur.
The aperture of the second-stage throttling is 6.27mm, the pressure before throttling is 34.88MPa, the pressure after throttling is 9.96MPa, the critical flow rate is 375.36m/s, the rated pressure of the separation equipment is met, and the throttling nozzles cannot be eroded. At the moment, the pressure drop and erosion prevention requirements of the working condition can be met by the throttling progression and the throttling caliber.
Flow maximization prediction
According to the throttle level and throttle caliber under the corresponding working condition of the selected A1 well, respectively calculating the two stages of throttle caliber to obtain a first stage maximum flow of 352.11 ten thousand m 3 And/d, the maximum flow rate of the second stage is 56.87 ten thousand m 3 However, since the throttle nozzles are connected in series, the final flow rate is 56.87 ten thousand m 3 /d。
At present, the erosion rate is still used as the limit range of the maximum pressure drop of the single-stage throttling, the maximum flow rate is set, and the corresponding throttling caliber is obtained by substituting the maximum flow rate into a model for calculation, so that the caliber distribution for the two-stage throttling is finally obtained:
the first-stage throttling caliber is 7.17mm, the pre-throttling pressure is 64.2MPa, the post-throttling pressure is 24.73MPa, the erosion rate is 332.79m/s, the actual flow rate is 332.73m/s, and erosion cannot occur.
The aperture of the second-stage throttling is 10.28mm, the pressure before throttling is 24.73MPa, the pressure after throttling is 7.06MPa, the critical flow rate is 384.12m/s, the rated pressure of the separation equipment is met, and the throttling nozzles cannot be eroded. At the moment, the pressure drop and erosion prevention requirements of the working condition can be met by the throttling progression and the throttling caliber.
Under the working condition, the maximum flow rate is calculated to obtain the first-stage maximum flow rate of 115.30 ten thousand m 3 And/d, the maximum flow rate of the second stage is 99.66 ten thousand m 3 And/d, the final flow rate is 99.66 ten thousand m because the throttle nozzles are connected in series 3 /d。
The calculation simulation method for maximizing the flow is also required to be established on the premise of meeting the rated pressure of the ground pipeline separator of the high-pressure/ultrahigh-pressure gas well and the erosion pressure drop of the throttle valve, and on the basis, the calculation simulation method calculates the maximizing configuration in real time according to the working condition change, and redistributes the maximizing configuration to each throttle device to realize remote real-time regulation and control.
Linkage and remote control of models and devices
After the flow calculation based throttling series and related parameters of the throttling caliber are completed, the computer performs unified scheduling distribution by collecting real-time data before and after throttling, and the flow is as follows:
(1) Taking the measured wellhead pressure as an initial pressure condition, obtaining pressure drop according to the final pressure of the separator, calculating a throttling flow rate condition according to the erosion flow rate, and calculating to obtain at least the required throttling level and throttling caliber;
(3) Redistributing the obtained caliber parameters according to a flow optimization calculation model to achieve the optimized flow under the corresponding working condition, wherein the calculation process needs to ensure that the total pressure drop and the single-stage pressure drop meet the requirements at any time;
(4) The obtained parameters are sent to opening controllers of all levels of throttle valves in real time through a circuit by a unified controller, and the opening controllers determine the required caliber and the needle valve descending degree;
(5) The opening controller controls the electromagnetic valve, the communication gas circuit fills high-pressure gas into the closed cylinder, the piston is pushed and the reset spring is compressed, the descending depth of the throttle needle valve is lifted, a sensor positioned at the position of the cylinder head at the tail end of the needle valve can record the current descending depth of the needle valve in real time, and the sensor feeds back to the electromagnetic valve to be closed automatically after meeting the condition;
(6) When the pressure change of pipeline fluid is required to be reduced, the electromagnetic valve is used for controlling the gas in the air cylinder to be withdrawn, the reset spring is used for pushing the needle valve to reduce the throttling caliber, the requirement on the throttling pressure drop of the pipeline is met, and the multistage throttling simulation calculation real-time remote control can be performed at any time in the natural gas production process;
as shown in fig. 6 and 7, the steps (1) (2) (3) are throttle valves at each level, (4) are gas injection pipeline filtering pressure reducing valves, (5) are electromagnetic valves, three-position five-way electromagnetic valves are selected, the upper part, the middle part and the lower part are respectively corresponding to gas injection, closing and gas release, (6) are opening controllers which are connected with a real-time simulation computer and control the electromagnetic valves, (7) are position sensors, when the throttle needle valve reaches the required depth, the throttle valves are fed back to the opening controllers, and then the gas injection process of the electromagnetic valves is closed, and (8) the multi-stage throttle simulation computer performs real-time calculation and real-time regulation by collecting pipeline pressure parameters.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
It should be noted that, for simplicity of description, the foregoing method embodiments are all expressed as a series of action combinations, but it should be understood by those skilled in the art that the present application is not limited by the described order of action, as some steps may take other order or be performed simultaneously according to the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments and that the acts and elements referred to are not necessarily required in the present application.
In the foregoing embodiments, the descriptions of the embodiments are focused on, and for those portions of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.
Those skilled in the art will appreciate that implementing all or part of the above-described methods in the embodiments may be accomplished by computer programs stored in a computer-readable storage medium, which when executed, may include the steps of the embodiments of the methods described above. Wherein the storage medium may be a magnetic disk, an optical disk, a ROM, a RAM, etc.
The foregoing disclosure is illustrative of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (9)
1. The flow optimization control method of the high-pressure gas well ground pipeline is characterized by comprising the following steps of:
step S1, establishing a multi-stage throttling temperature and pressure calculation model of a high-pressure/ultrahigh-pressure gas well ground pipeline;
s2, calculating a multi-stage throttling series and a corresponding caliber;
s3, calculating multi-stage throttling natural gas flow and adjusting caliber distribution pressure difference;
and S4, inputting the calculated parameters to each stage of throttle valve to realize remote automatic control.
2. The method for optimizing and controlling the flow rate of the ground pipeline of the high-pressure gas well according to claim 1, wherein the step S1 is specifically: according to the wellhead temperature and pressure obtained through initial measurement, the fluid change of the whole ground pipeline is regarded as an adiabatic process, the rated pressure condition of the separator is regarded as the final pressure of the ground test pipeline, so that the pressure drop required by the throttling process is obtained, and the temperature and pressure fields of the ground pipeline and the front and the rear of the throttle valve are established.
3. The method for optimizing and controlling the flow rate of a high-pressure gas well surface pipeline according to claim 2, wherein the pressure drop calculation process comprises the following sub-steps:
step S11, under the subcritical state, calculating the relation between the natural gas flow and the pressure ratio of the upstream and downstream of the throttling, wherein the calculation formula is,
in step S12, in the critical state, the relation between the natural gas flow and the pressure ratio of the upstream and downstream of the throttling is calculated, wherein the calculation formula is,
step S13, calculating the throttling pressure drop of the gas flowing through the fixed oil nozzle, wherein the calculation formula is,
wherein Q is g -natural gas current state flow, 10 4 m 3 /d; q-natural gas production (under standard conditions); p (P) 1 -pressure upstream of the restrictor, MPa; p (P) 2 -a pressure downstream of the restrictor; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 -the natural gas compression factor under corresponding temperature and pressure conditions; gamma ray g -natural gas relative density; k—natural gas adiabatic index; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma-natural gas relative density.
4. The method according to claim 1, wherein the step S2 is specifically that when the flow state of the gas flowing through the fixed choke reaches the critical flow state, the pressure drop generated by the throttling will not affect the actual yield of the natural gas any more, and the natural gas fluid flow is only related to the diameter of the choke, so that the diameter of the choke can be reasonably calculated by distributing the pressure on the premise of ensuring that the pressure drop is enough for safe production, and the calculation formula is as follows:
wherein Q is sc Natural gas production, 10 4 m 3 /d；P 1 ，P 2 -pressure upstream and downstream of the restrictor, MPa; d-throttle caliber, mm; t (T) 1 -temperature upstream of the restrictor, K; z is Z 1 —T 1 And P 1 A gas compression factor under conditions; gamma ray g -natural gas relative density.
5. The method of optimizing control of flow in a high pressure well surface line according to claim 4, further comprising the step of calculating the erosion wear of the choke manifold, including gradually increasing as the pressure before throttling decreases based on the theoretical calculation of the erosion rate, maintaining a steady flow rate after the fluid reaches the critical rate, the calculated erosion rate increasing continuously, the theoretical rate decreasing as the theoretical rate increases, the actual flow rate always being lower than the erosion flow rate, i.e., the safe critical rate V 2 The critical rate V 2 The calculation formula of (c) is as follows,
6. the method for optimizing and controlling the flow of the ground pipeline of the high-pressure gas well according to claim 1, wherein the step S3 is specifically a method for optimizing the flow maximization of the multi-stage throttling of the high-pressure/ultra-high-pressure ground test pipeline by calculating the natural gas flow under the corresponding throttling valve according to the calculated throttling level and throttling caliber and then adjusting the pressure drop and caliber of each stage of the multi-stage throttling on the premise of guaranteeing the stability of the total pressure difference and the single-stage throttling pressure difference until the total natural gas flow reaches the maximum value.
7. The method for optimizing and controlling the flow rate of a high-pressure gas well surface pipeline according to claim 1, wherein the step S4 comprises the following substeps:
s41, reassigning the throttling caliber d to achieve the optimized flow under the corresponding working condition;
step S42, the obtained parameters are sent to opening controllers of all levels of throttle valves in real time through a unified controller and a circuit, and the opening controllers determine the required caliber and the needle valve descending degree;
step S43, the opening controller controls the electromagnetic valve, the communication gas path fills high-pressure gas into the closed cylinder, the piston is pushed and the return spring is compressed, the entering depth of the throttle needle valve is lifted, a sensor at the position of the cylinder head at the tail end of the needle valve can record the current entering depth of the needle valve in real time, and the sensor feeds back to the electromagnetic valve to be closed automatically after the condition is met;
the method also comprises the step of reducing the caliber, and specifically comprises the following steps: when the pipeline fluid pressure change needs to be reduced in caliber, the electromagnetic valve is used for controlling the gas in the evacuation cylinder, the reset spring is used for pushing the needle valve to reduce the throttling caliber, the requirement on pipeline throttling pressure drop is met, and the multistage throttling simulation calculation real-time remote control can be performed at any time in the natural gas production process.
8. A computer program product comprising a computer program which, when executed by a processor, implements a method of optimizing control of flow of a high pressure gas well surface pipeline according to any one of claims 1 to 7.
9. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements a flow optimization control method of a high pressure gas well surface pipeline according to any one of claims 1 to 7.
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