CN109236281B - Device and method for detecting annular pressure of gas storage and natural gas well - Google Patents
Device and method for detecting annular pressure of gas storage and natural gas well Download PDFInfo
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- 239000002343 natural gas well Substances 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000001514 detection method Methods 0.000 claims abstract description 89
- 230000008859 change Effects 0.000 claims abstract description 22
- 239000007788 liquid Substances 0.000 claims abstract description 15
- 230000007774 longterm Effects 0.000 claims abstract description 15
- 238000004458 analytical method Methods 0.000 claims abstract description 9
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 62
- 239000003345 natural gas Substances 0.000 claims description 31
- 239000000463 material Substances 0.000 claims description 30
- 238000011084 recovery Methods 0.000 claims description 24
- 230000006835 compression Effects 0.000 claims description 18
- 238000007906 compression Methods 0.000 claims description 18
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- 230000008569 process Effects 0.000 claims description 12
- 239000012530 fluid Substances 0.000 claims description 11
- 238000012544 monitoring process Methods 0.000 claims description 9
- 238000012360 testing method Methods 0.000 claims description 7
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 6
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- 238000005755 formation reaction Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention provides a device and a method for detecting annular pressure of a gas storage and a natural gas well, and relates to the field of petroleum exploration and development. The detection device comprises a needle valve, a gas-liquid separator, a pressure gauge, a flowmeter and data acquisition equipment, wherein the needle valve, the gas-liquid separator and the flowmeter are sequentially connected, the pressure gauge is positioned in front of the needle valve, and the data acquisition equipment is respectively connected with the flowmeter and the pressure gauge; detecting by a detection device, and calculating to obtain an annular pressure relief curve, a relief speed curve, a relief quantity curve and an annular pressure gathering curve; and analyzing the annular pressure and the discharge flow, and predicting the annular pressure change condition. By adopting the detection device and the detection method, the wellhead annulus pressure condition can be conveniently and accurately detected, the annulus pressure and the discharge flow of any gas storage and the A and B annuluses of the natural gas well can be obtained through analysis data, meanwhile, the annulus pressure long-term change condition can be predicted through short-time detection, and the detection efficiency can be effectively improved.
Description
Technical Field
The invention relates to the field of petroleum exploration and development, in particular to an annular pressure detection device and method for a gas storage and a natural gas well.
Background
With the increasing expansion of the market demand of natural gas, the investment in the aspect of building the underground gas storage is gradually strengthened, the exploitation of the natural gas well is further increased, and meanwhile, the requirements on both the economy and the safety of the operation of the gas storage and the natural gas well are also stronger. Through long-term investigation, the gas storage and the natural gas well are influenced by factors such as geological conditions, and annulus pressure is easy to generate. Such continuous annular pressure (SCP) is typically caused by fluid flow through the well control isolation layer due to leaks in the well components (i.e., leaks at tubing joints, leaks in packing seals, etc., or cement failure (or poor bond) or cement sheath failure). Any pressurized formation may cause continuous annular pressure (SCP), including gas bearing formations, aquifers, shallow gas zones, shallow water zones, or due to biological factors. In the method for managing annular pressure of gas storage and natural gas well, although an annular pressure leakage detection method is already formed at home and abroad, most of the methods are qualitative analysis and lack of quantitative description methods when analyzing and judging the degree of annular pressure.
Disclosure of Invention
The object of the present invention is to provide an annular pressure detection device which solves the aforementioned problems of the prior art.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the utility model provides a gas storage and natural gas well annular pressure detection device, detection device includes needle valve, gas-liquid separator, manometer, flowmeter and data acquisition equipment, the needle valve gas-liquid shunt with the flowmeter is connected in order, the manometer is located before the needle valve, data acquisition equipment respectively with the flowmeter with pressure testing arrangement links to each other.
Preferably, the detection device further comprises a power supply and an alkali liquor barrel, wherein the power supply supplies power to the data acquisition equipment, and the alkali liquor barrel is connected to the tail part of the testing device and is used for neutralizing acid gas in the tail gas.
Preferably, the needle valve and the gas-liquid separator in the detection device are connected by a high-pressure hose line.
Preferably, a connecting valve is further arranged between the needle valve and the on-off valve of the wellhead to be tested, and the connecting valve can be connected in a conversion mode according to an interface of the field well in actual use, so that the equipment can stably and continuously detect annular pressure and flow.
The invention further provides a method for detecting annular pressure of a gas storage and a natural gas well, which comprises the following steps:
s1, detecting through an annular pressure detection device of a gas storage and a natural gas well, and calculating to obtain an annular pressure relief curve, a relief speed curve and a relief amount curve;
s2, detecting an annular pressure gathering curve of 24 hours or a specified time period through an annular pressure detection device of the gas storage and the natural gas well;
s3, analyzing the annular pressure and the discharge flow, and predicting the annular pressure change condition.
Preferably, step S0 is further included before step S1, the gas storage and the natural gas well annulus pressure detection device are tightly connected with the on-off valve of the wellhead through a connecting valve, the gas storage and the natural gas well annulus pressure detection device are calibrated, and the power supply of the gas storage and the natural gas well annulus pressure detection device is turned on.
Preferably, the step S3 specifically includes the following steps:
s31, judging whether the pressure change condition of the annular space A or the pressure change condition of the annular space B is known according to the annular space volume; if the working condition is the annular working condition A, the step S32 is directly carried out, and if the working condition is the annular working condition B, the step S33 is carried out;
s32, determining the equivalent leak diameter by using a pressure recovery curve according to the known annular volume, so as to determine the open-drain flow and long-term pressure recovery curve;
s33, aiming at the situation that the annular volume is unknown, firstly, the annular volume is determined by utilizing a complete pressure relief curve and a partial pressure recovery curve, then the annular volume is combined with the partial pressure recovery curve to determine the equivalent leak point diameter, and finally, the open leak flow, the closed leak flow and the long-term pressure recovery curve are determined according to the equivalent leak point diameter.
Preferably, the step S32 specifically includes the steps of:
(1) establishing an oil sleeve annulus pressure problem simplified model: a. both communicating vessels are closed vessels; b. the pressure change in the container B is measurable; c. the volume of container B is known;
(2) according to the measured pressure relief curve, selecting the time of two points A, B, t A And t B Corresponding pressure value P A And P B Then at Δt=t A -t B The change in the amount of gaseous material in container B is calculated by the following formula:
in n A -the detection time is t A The amount, mol, of the gaseous substance in the container B;
n B -the detection time is t B The amount, mol, of the gaseous substance in the container B;
P A -the detection time is t A The pressure of the gas in the container B is equal to MPa;
P B -the detection time is t B The pressure of the gas in the container B is equal to MPa;
v-volume of vessel B, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the container B is dimensionless;
Z B -the detection time is t B The compression coefficient of the gas in the container B is dimensionless;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T anu -temperature in annulus, K;
Δn—variation of the amount of gaseous substance in container B, mol;
as the communication flow is known:
in Deltan rel -the amount of substance flowing into the container B gas at Δt, mol;
Δt-detection time t A And t B Time interval s between;
q-flow of gas in nozzle per unit time, m 3 /s；
P sd -the pressure outside the container B, i.e. the normal atmospheric pressure, pa;
T sd -the temperature outside the container B, i.e. the local meteorological temperature, K;
the following formula is obtained according to the law of conservation of mass:
(3) selecting two flow sections on the container B, wherein the fluid parameter arranged on the first flow section is p 1 ，u 1 ，t 1 ，ρ 1 And the fluid parameter at the second flow cross section is p 2 ，u 2 ，t 2 ，ρ 2 ；
Establishing a Bernoulli equation of gas for two flow sections:
the flow rate of the gas at the first flow cross section is 0, so u 1 Let the pressure and density at this time be p respectively =0 0 And ρ 0 . And the Bernoulli equation reduction at this time yields the following formula:
at p 2 And p is as follows 0 The ratio of (2) is unknown, the following can be deduced:
further simplifying the formula to obtain the following formula:
finally obtain
Let u be 2 ＝C＝C c Is the critical flow rate at the second flow cross section, andthe above equation is simplified to the following equation:
in the formula, k is a gas heat insulation coefficient, and can take 1.3 for natural gas without dimension;
from Bernoulli's equation, the flow velocity u at the second flow cross section can be determined 2 Further, the flow rate q at the position is obtained 2-2 The formula is as follows:
q in 2-2 Flow at the second flow section, m 3 /s；
A-the cross-sectional area at the second flow section, m 2 ；
d 2-2 -equivalent leak diameter at the second flow cross section, m;
u in the above 2 The following equation can be used to obtain:
and is also provided withThe carry-over constant is finally calculated to the following equation:
when the fluid flow rate of the second flow cross section reaches the critical flow rate, the flow formula may be expressed as follows:
(4) equivalent leak diameter expression: bringing the flow expression into an equation for conservation of the amount of gaseous material yields the following equation:
if the two selected points are before reaching the critical point, the equivalent leak diameter is:
if the two selected points reach the critical point, the equivalent leakage point diameter:
(5) knowing the equivalent leak diameter, an open bleed, a closed bleed and a long-term annulus pressure recovery curve can be obtained;
the open bleed flow is the product of the initial slope of the fitted curve and the predicted time:
the closed leakage flow is the product of flow and predicted time:
Q c ＝qt (48)
(6) fitting by using a least square method and using an actually measured pressure recovery curve to obtain a partial pressure recovery curve, and predicting the partial pressure recovery curve to obtain a long-term annulus pressure recovery curve through the following steps:
preferably, step S33 specifically includes the steps of:
a, establishing a technical ring air pressure quantitative analysis model, wherein n is as follows 1 N is the amount of substance of the gas flowing into the container 2 For the amount of material of the gas flowing out of the container, a gas state equation is established as follows:
PV＝ZnRT (49)
p in the formula is the absolute pressure of gas and MPa;
v-volume of gas, m 3 ；
Z is the compression coefficient of the gas, and is dimensionless;
n-the amount of material of the gas, mol;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T-the temperature of the gas, K;
during the pressure release process, the detection time t A And time t B The pressure values of (2) are P respectively A And P B Then at Δt=t A -t B The amount of gaseous material flowing out of the container can be derived by:
in n A -the detection time is t A The amount of material in the annulus, mol;
n B -the detection time is t B The amount of material in the annulus, mol;
P A -the detection time is t A Pressure in the annulus, MPa;
P B -the detection time is t B Pressure in the annulus, MPa;
V 0 annulus (closed vessel) volume, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the annular space is dimensionless;
Z B -the detection time is t B The compression coefficient of the gas in the annular space is dimensionless;
T anu -temperature in annulus, K;
the change in the amount of material in the container deltan is shown by the following formula:
and B, analyzing the total amount of the gas in the container in the pressure release process: in the pressure release process, the quantity v of the gaseous material flowing out of the annulus per unit time n Can be measured by a flow meter, so that the amount of material flowing out of the annulus is measured at a time deltatThe following formula can be obtained from mass conservation:
in n 1 And V 0 Are unknown;
closing the device for releasing the gas, wherein only the gas flows into the annular space, and monitoring a pressure curve of the pressure value in the annular space, wherein the curve represents the function relation between the pressure and the time and is recorded as P=f (t);
a. closing the device for releasing gas, and monitoring the annular pressure value in delta t time to obtain the function relation P=f (t) of the pressure and the time
Obtaining the amount of the substance of the gas flowing into the annular space within the delta t time through integration;
b. closing the device for releasing gas, monitoring the annular pressure value in a period of time to obtain a pressure-time functional relation P=f (t), and selecting the pressure value as P on a pressure-time curve 1 At the same time, the pressure value P after a small time dt in the vicinity of the curve 2 Let P be 1 And P 2 The slope of the straight line between the two is the pressure value P 1 A derivative of pressure with respect to time; since dt is very small, the change in Z is not considered in the analysis, and the gas inflow rate is considered to be uniform and constant;
where z is the compression coefficient,dimensionless;
P r the contrast pressure of the natural gas is equal to that of the natural gas,dimensionless;
p-absolute pressure of natural gas, pa;
P c -critical pressure of natural gas, pa;
T r comparison of Natural gasThe temperature of the mixture is set to be higher than the temperature,dimensionless;
t-absolute temperature of natural gas, K;
T c -critical temperature, K, of natural gas;
ρ r -the relative density of the natural gas,dimensionless;
ρ -density of natural gas kg/m 3 ；
ρ a Density of air, kg/m 3 ；
D, obtain V 0 Is provided with the expression of (1)
The annulus pressure predictive function expression is therefore as follows:
e, converting the model into a model with a known volume for calculation and analysis to obtain an equivalent leak point diameter, an open bleed flow, a closed bleed flow and a long-term annulus pressure prediction model.
Preferably, the step S3 further includes: and S4, after the test is finished, closing a power supply of the gas storage and natural gas well annular pressure detection device, and disconnecting the gas storage and natural gas well annular pressure detection device from a wellhead.
The beneficial effects of the invention are as follows:
the invention provides a device and a method for detecting the annular pressure of a gas storage and a natural gas well, which can conveniently and accurately detect the annular pressure condition of a wellhead, obtain the annular pressure and the discharge flow of the annular pressure A and the annular pressure B of any gas storage and the natural gas well through analysis data, and simultaneously predict the condition of the annular pressure change for a long time through short time detection, thereby effectively improving the detection efficiency.
Drawings
FIG. 1 is a schematic diagram of an annular pressure detection device for a gas storage and a natural gas well;
FIG. 2 is a simplified model of oil jacket annulus pressure problems;
FIG. 3 is a simplified model of a nozzle flow process;
FIG. 4 is a schematic representation of an annulus pressure predictive analysis model.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the detailed description is presented by way of example only and is not intended to limit the invention.
Example 1
The embodiment provides an annular pressure detection device for a gas storage and a natural gas well, which comprises a detection device, wherein the detection device comprises a needle valve, a gas-liquid separator, a pressure gauge, a flowmeter and data acquisition equipment, the needle valve is used for limiting the flow flowing into the gas-liquid separator in the wellhead pressure release process, the flow flowing into the gas-liquid separator can be controlled and regulated through regulating the needle valve, the gas-liquid separator is mainly used for separating gas and liquid in fluid leaked from a wellhead, the damage of liquid materials leaked from the wellhead to the flowmeter and the influence of measurement accuracy are reduced as much as possible, the flowmeter is mainly used for testing the flow and the flow velocity of gas passing through the wellhead in the pressure release process, the opening degree of the needle valve has larger influence on real-time flow and flow velocity, and the accumulated flow influence is smaller.
The needle valve, the gas-liquid shunt and the flowmeter are sequentially connected, the pressure gauge is positioned in front of the needle valve, and the data acquisition equipment is respectively connected with the flowmeter and the pressure gauge.
In order to collect acid harmful gases such as hydrogen sulfide contained in the natural gas discharged from a wellhead and meet the environmental protection requirement, the detection device further comprises an alkali liquor barrel arranged at the tail part of the testing device; the power data acquisition equipment normally operates to provide necessary electric quantity, and the power is externally arranged and convenient to replace.
The needle valve in the detection device is connected with the gas-liquid separator through a high-pressure hose line.
The connection valve can be switched and connected according to an interface of the field well in actual use, so that the equipment can stably and continuously detect annular pressure and flow.
Example 2
The embodiment provides an annular pressure detection method, which comprises the following steps:
s0, tightly connecting the gas storage annular pressure detection device with a wellhead through a connecting valve, calibrating the gas storage annular pressure detection device, and opening a power supply of the gas storage annular pressure detection device and the natural gas well annular pressure detection device;
s1, opening a switching valve and a needle valve, and acquiring data of a pressure detection device and a flowmeter in real time through data acquisition equipment to obtain an annular pressure relief curve, a relief flow velocity and a flow curve;
s2, when the reading of the pressure gauge is about 0 or 0.1MPa, completely closing the needle valve; and acquiring data of the pressure detection device in real time through data acquisition equipment to obtain an annular pressure aggregation curve.
S3, analyzing the annular control pressure, the annular pressure and the discharge flow, and predicting the annular pressure change condition;
s31, judging whether the annular volume is the pressure change condition of the annular space A or the pressure change condition of the annular space B according to whether the annular volume is known; if the working condition is the annular working condition A, the step S32 is directly carried out, and if the working condition is the annular working condition B, the step S33 is carried out;
s32, determining the equivalent leak diameter by using a pressure recovery curve according to the known annular volume, so as to determine the open-drain flow and long-term pressure recovery curve;
s33, aiming at the situation that the annular volume is unknown, firstly, the annular volume is determined by utilizing a complete pressure relief curve and a partial pressure recovery curve, then the annular volume is combined with the partial pressure recovery curve to determine the equivalent leak point diameter, and finally, the open leak flow, the closed leak flow and the long-term pressure recovery curve are determined according to the equivalent leak point diameter.
And S4, after the test is finished, closing a power supply of the gas storage and natural gas well annular pressure detection device, and disconnecting the gas storage and natural gas well annular pressure detection device from a wellhead.
Note that step S32 is specifically the following steps:
(1) establishing an oil sleeve annular pressure problem simplified model, as shown in figure 2, wherein a. Both communicating vessels are closed vessels; b. the pressure change in the container B is measurable; c. the volume of container B is known;
(2) according to the measured pressure relief curve, selecting the time of two points A, B, t A And t B Corresponding pressure value P A And P B Then at Δt=t A -t B The change in the amount of gaseous material in container B is calculated by the following formula:
in n A -the detection time is t A The amount, mol, of the gaseous substance in the container B;
n B -the detection time is t B The amount, mol, of the gaseous substance in the container B;
P A -the detection time is t A The pressure of the gas in the container B is equal to MPa;
P B -the detection time is t B The pressure of the gas in the container B is equal to MPa;
v-volume of vessel B, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the container B is dimensionless;
Z B -the detection time is t B The compression coefficient of the gas in the container B is dimensionless;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T anu -temperature in annulus, K;
Δn—variation of the amount of gaseous substance in container B, mol;
as the communication flow is known:
in Deltan rel -the amount of substance flowing into the container B gas at Δt, mol;
Δt-detection time t A And t B Time interval s between;
q-flow of gas in nozzle per unit time, m 3 /s；
P sd -the pressure outside the container B, i.e. the normal atmospheric pressure, pa;
T sd -the temperature outside the container B, i.e. the local meteorological temperature, K;
the following formula is obtained according to the law of conservation of mass:
(3) selecting two containers BThe flow cross section is shown in FIG. 3, and the fluid parameter provided on the first flow cross section (1-1) is p 1 ，u 1 ，t 1 ，ρ 1 And the fluid parameter at the second flow section (2-2) is p 2 ，u 2 ，t 2 ，ρ 2 ；
Establishing a Bernoulli equation of gas for two flow sections:
the flow rate of the gas at the first flow cross section is 0, so u 1 Let the pressure and density at this time be p respectively =0 0 And ρ 0 . And the Bernoulli equation reduction at this time yields the following formula:
at p 2 And p is as follows 0 The ratio of (2) is unknown, the following can be deduced:
further simplifying the formula to obtain the following formula:
finally obtain
Let u be 2 ＝C＝C c Is the critical flow rate at the second flow cross section, andthe above equation is simplified to the following equation:
in the formula, k is a gas heat insulation coefficient, and can take 1.3 for natural gas without dimension;
from Bernoulli's equation, the flow velocity u at the second flow cross section can be determined 2 Further, the flow rate q at the position is obtained 2-2 The formula is as follows:
q in 2-2 Flow at the second flow section, m 3 /s；
A-the cross-sectional area at the second flow section, m 2 ；
d 2-2 -equivalent leak diameter at the second flow cross section, m;
u in the above 2 The following equation can be used to obtain:
and is also provided withThe carry-over constant is finally calculated to the following equation:
when the fluid flow rate of the second flow cross section reaches the critical flow rate, the flow formula may be expressed as follows:
(4) equivalent leak diameter expression: bringing the flow expression into an equation for conservation of the amount of gaseous material yields the following equation:
if the two selected points are before reaching the critical point, the equivalent leak diameter is:
if the two selected points reach the critical point, the equivalent leakage point diameter:
(5) knowing the equivalent leak diameter, an open bleed, a closed bleed and a long-term annulus pressure recovery curve can be obtained;
the open bleed flow is the product of the initial slope of the fitted curve and the predicted time:
the closed leakage flow is the product of flow and predicted time:
Q c ＝qt (77)
(6) fitting by using a least square method and using an actually measured pressure recovery curve to obtain a partial pressure recovery curve, and predicting the partial pressure recovery curve to obtain a long-term annulus pressure recovery curve through the following steps:
the step S33 specifically includes the following steps:
a, establishing a technical ring air pressure quantitative analysis model, as shown in figure 4, in the model, n 1 N is the amount of substance of the gas flowing into the container 2 For the amount of material of the gas flowing out of the container, a gas state equation is established as follows:
PV＝ZnRT (78)
p in the formula is the absolute pressure of gas and MPa;
v-volume of gas, m 3 ；
Z is the compression coefficient of the gas, and is dimensionless;
n-the amount of material of the gas, mol;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T-the temperature of the gas, K;
during the pressure release process, the detection time t A And time t B The pressure values of (2) are P respectively A And P B Then at Δt=t A -t B The amount of gaseous material flowing out of the container can be derived by:
in n A -the detection time is t A The amount of material in the annulus, mol;
n B -the detection time is t B The amount of material in the annulus, mol;
P A -the detection time is t A Pressure in the annulus, MPa;
P B -the detection time is t B Pressure in the annulus, MPa;
V 0 annulus (closed vessel) volume, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the annular space is dimensionless;
Z B -detectionTime t B The compression coefficient of the gas in the annular space is dimensionless;
T anu -temperature in annulus, K;
the change in the amount of material in the container deltan is shown by the following formula:
and B, analyzing the total amount of the gas in the container in the pressure release process: in the pressure release process, the quantity v of the gaseous material flowing out of the annulus per unit time n Can be measured by a flow meter, so that the amount of material flowing out of the annulus is measured at a time deltatThe following formula can be obtained from mass conservation:
/>
in n 1 And V 0 Are unknown.
Closing the device for releasing the gas, wherein only the gas flows into the annular space, and monitoring a pressure curve of the pressure value in the annular space, wherein the curve represents the function relation between the pressure and the time and is recorded as P=f (t);
a. closing the device for releasing gas, and monitoring the annular pressure value in delta t time to obtain the function relation P=f (t) of the pressure and the time
Obtaining the amount of the substance of the gas flowing into the annular space within the delta t time through integration;
b. closing the device for releasing gas, monitoring the annular pressure value in a period of time to obtain a function relation P=f (t) of pressure and time, and selecting the pressure value as the pressure value on a curve of the pressure and the timeP 1 At the same time, the pressure value P after a small time dt in the vicinity of the curve 2 Let P be 1 And P 2 The slope of the straight line between the two is the pressure value P 1 Since dt is very small, the change in Z is not considered in the analysis and the gas inflow rate is considered uniform and constant;
where z is the compression coefficient,dimensionless;
P r the contrast pressure of the natural gas is equal to that of the natural gas,dimensionless;
p-absolute pressure of natural gas, pa;
P c -critical pressure of natural gas, pa;
T r -the comparative temperature of the natural gas,dimensionless;
t-absolute temperature of natural gas, K;
T c -critical temperature, K, of natural gas;
ρ r -the relative density of the natural gas,dimensionless;
ρ -density of natural gas kg/m 3 ；
ρ a Density of air, kg/m 3 ；
D, obtain V 0 Is provided with the expression of (1)
The annulus pressure predictive function expression is therefore as follows:
e, converting the model into a model with a known volume for calculation and analysis to obtain an equivalent leak point diameter, an open bleed flow, a closed bleed flow and a long-term annulus pressure prediction model.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which is also intended to be covered by the present invention.
Claims (6)
1. The method for detecting the annular pressure of the gas storage and the natural gas well is characterized by comprising the following steps of:
s1, detecting through an annular pressure detection device of a gas storage and a natural gas well, and calculating to obtain an annular pressure relief curve, a relief speed curve and a relief amount curve;
s2, detecting an annular pressure gathering curve of 24 hours or a specified time period through an annular pressure detection device of the gas storage and the natural gas well;
s3, analyzing the annular pressure and the discharge flow, and predicting the annular pressure change condition;
the step S3 specifically comprises the following steps:
s31, determining whether the annular volume is known or not, if the annular volume is known, determining that the annular volume is the annular volume A, directly entering the step S32, and if the annular volume is not known, determining that the annular volume B, entering the step S33;
s32, (1) establishing an oil sleeve annulus pressure problem simplified model: a. the two communicating vessels consist of a vessel A and a vessel B, wherein the vessel A and the vessel B are closed vessels; b. the pressure change in the container B is obtained by measurement; c. the volume of container B is known;
(2) according to the measured pressure relief curve, selecting the time of two points A, B, t A And t B Corresponding pressure value P A And P B Then at Δt=t A -t B The change in the amount of gaseous material in container B is calculated by the following formula:
in n A -the detection time is t A The amount, mol, of the gaseous substance in the container B;
n B -the detection time is t B The amount, mol, of the gaseous substance in the container B;
P A -the detection time is t A The pressure of the gas in the container B is equal to MPa;
P B -the detection time is t B The pressure of the gas in the container B is equal to MPa;
v-volume of vessel B, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the container B is dimensionless;
Z B -the detection time is t B The compression coefficient of the gas in the container B is dimensionless;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T anu -temperature in annulus, K;
Δn—variation of the amount of gaseous substance in container B, mol;
as a result of the communication flow, it is:
in Deltan rel -the amount of substance flowing into the container B gas at Δt, mol;
Δt-detection time t A And t B Time interval s between;
q-flow of gas in nozzle per unit time, m 3 /s；
P sd -the pressure outside the container B, i.e. the normal atmospheric pressure, pa;
T sd -the temperature outside the container B, i.e. the local meteorological temperature, K;
the following formula is obtained according to the law of conservation of mass:
(3) selecting two flow sections on the container B, wherein the fluid parameter arranged on the first flow section is p 1 ，u 1 ，t 1 ，ρ 1 And the fluid parameter at the second flow cross section is p 2 ，u 2 ，t 2 ，ρ 2 ；
Establishing a Bernoulli equation of gas for two flow sections:
the flow rate of the gas at the first flow cross section is 0, so u 1 Let the pressure and density at this time be p respectively =0 0 And ρ 0 The method comprises the steps of carrying out a first treatment on the surface of the And the Bernoulli equation reduction at this time yields the following formula:
at p 2 And p is as follows 0 If the ratio of (2) is unknown, the following equation is deduced:
further simplifying the formula to obtain the following formula:
finally obtain
Let u be 2 ＝C＝C c Is the critical flow rate at the second flow cross section, andthe above equation is simplified to the following equation:
k is a gas heat insulation coefficient, and is 1.3 for natural gas, and is dimensionless;
obtaining the flow velocity u at the second flow section according to Bernoulli equation 2 Further, the flow rate q at the position is obtained 2-2 The formula is as follows:
q in 2-2 Flow at the second flow section, m 3 /s；
a-cross-sectional area at the second flow section, m 2 ；
d 2-2 -equivalent leak diameter at the second flow cross section, m;
u in the above 2 The following formula was used to obtain:
and p is 0 ＝Zρ 0 RT 0 ,The carry-over constant is finally calculated to the following equation:
when the fluid flow rate of the second flow cross section reaches the critical flow rate, the flow formula is expressed as follows:
(4) equivalent leak diameter expression: bringing the flow expression into an equation for conservation of the amount of gaseous material yields the following equation:
if the two selected points are before reaching the critical point, the equivalent leak diameter is:
if the two selected points reach the critical point, the equivalent leakage point diameter:
(5) knowing the equivalent leak diameter, obtaining an open bleed, a closed bleed and a long-term pressure recovery curve;
the open bleed flow is the product of the initial slope of the fitted curve and the predicted time:
the closed leakage flow is the product of flow and predicted time:
Q c ＝qt (19)
(6) fitting by using a least square method and using an actually measured pressure recovery curve to obtain a partial pressure recovery curve, and predicting by the following formula to obtain a long-term pressure recovery curve:
s33, specifically comprising the following steps:
a, establishing a technical ring air pressure quantitative analysis model, wherein n is as follows 1 N is the amount of substance of the gas flowing into the container 2 For the amount of material of the gas flowing out of the container, a gas state equation is established as follows:
PV＝ZnRT (20)
p in the formula is the absolute pressure of gas and MPa;
v-volume of gas, m 3 ；
Z is the compression coefficient of the gas, and is dimensionless;
n-the amount of material of the gas, mol;
r-ideal gas constant, r= 8.314472m 3 ·Pa/(K·mol)；
T-the temperature of the gas, K;
during the pressure release process, the detection time t A And time t B The pressure values of (2) are P respectively A And P B Then at Δt=t A -t B The amount of gaseous material flowing out of the container is determined by the following derivation:
in n A -the detection time is t A The amount of material in the annulus, mol;
n B -the detection time is t B The amount of material in the annulus, mol;
P A -the detection time is t A Pressure in the annulus, MPa;
P B -the detection time is t B Pressure in the annulus, MPa;
V 0 annular volume, m 3 ；
Z A -the detection time is t A The compression coefficient of the gas in the annular space is dimensionless;
Z B -the detection time is t B The compression coefficient of the gas in the annular space is dimensionless;
T anu -temperature in annulus, K;
the change in the amount of material in the container deltan is shown by the following formula:
and B, analyzing the total amount of the gas in the container in the pressure release process: in the pressure release process, the quantity v of the gaseous material flowing out of the annulus per unit time n Measured by a flow meter, so that the amount of material of the gas flowing out of the annulus is within a time delta tThe following formula is obtained from mass conservation:
in n 1 And V 0 Are unknown;
closing the device for releasing the gas, wherein only the gas flows into the annular space, and monitoring a pressure curve of the pressure value in the annular space, wherein the curve represents the function relation between the pressure and the time and is recorded as P=f (t);
a. closing the device for releasing gas, and monitoring the annular pressure value in delta t time to obtain the function relation P=f (t) of the pressure and the time
Obtaining the amount of the substance of the gas flowing into the annular space within the delta t time through integration;
b. closing the device for releasing gas, monitoring the annular pressure value in a period of time to obtain a pressure-time functional relation P=f (t), and selecting the pressure value as P on a pressure-time curve 1 At the same time, the pressure value P after a small time dt in the vicinity of the curve 2 Let P be 1 And P 2 The slope of the straight line between the two is the pressure value P 1 A derivative of pressure with respect to time; since dt is very small, the change in Z is not considered in the analysis and the gas is consideredThe inflow speed is uniform and unchanged;
where z is the compression coefficient,dimensionless;
P r the contrast pressure of the natural gas is equal to that of the natural gas,dimensionless;
p-absolute pressure of natural gas, pa;
P c -critical pressure of natural gas, pa;
T r -the comparative temperature of the natural gas,dimensionless;
t-absolute temperature of natural gas, K;
T c -critical temperature, K, of natural gas;
ρ r -the relative density of the natural gas,dimensionless;
ρ -density of natural gas kg/m 3 ；
ρ a Density of air, kg/m 3 ；
D, obtain V 0 Is provided with the expression of (1)
The annulus pressure predictive function expression is therefore as follows:
e, converting the model into a model with a known volume for calculation and analysis to obtain an equivalent leak point diameter, an open bleed flow, a closed bleed flow and a long-term annulus pressure prediction model;
the device for detecting the annular pressure of the gas storage and the natural gas well comprises a needle valve, a gas-liquid separator, a pressure gauge, a flowmeter and data acquisition equipment, wherein the needle valve, the gas-liquid separator and the flowmeter are sequentially connected, the pressure gauge is positioned in front of the needle valve, and the data acquisition equipment is respectively connected with the flowmeter and the pressure gauge.
2. The method according to claim 1, wherein the gas storage and natural gas well annulus pressure detection device further comprises a power supply and an alkali liquor barrel, wherein the power supply supplies power to the data acquisition equipment, and the alkali liquor barrel is connected to the tail part of the detection device and is used for neutralizing acid gas in tail gas.
3. The method of claim 1, wherein the gas reservoir is connected to the needle valve and the gas-liquid separator in the natural gas well annulus pressure detection device by a high-pressure hose line.
4. The method according to claim 1, wherein a connecting valve is further included between the needle valve and the on-off valve of the wellhead to be tested, and the connecting valve is connected in a switching manner according to an interface actually used by the field well, so as to ensure stable and continuous annular pressure and flow detection of the equipment.
5. The method according to claim 1, wherein the step S1 is preceded by a step S0 of tightly connecting the gas storage and natural gas well annular pressure detection device with the wellhead through a connecting valve, calibrating the gas storage and natural gas well annular pressure detection device, and turning on the power supply of the gas storage and natural gas well annular pressure detection device.
6. The method according to claim 1, wherein the step S3 further comprises: and S4, after the test is finished, closing a power supply of the gas storage and natural gas well annular pressure detection device, and disconnecting the gas storage and natural gas well annular pressure detection device from a wellhead.
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