Method for determining pressure of water-invaded gas reservoir waste stratum
阅读说明：本技术 一种水侵气藏废弃地层压力的确定方法 (Method for determining pressure of water-invaded gas reservoir waste stratum ) 是由 熊钰 郭美娟 孙泽威 吴道铭 彭杨 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种水侵气藏废弃地层压力的确定方法,包括以下步骤：拟合地层压力与体积系数之间的关系、以及地层压力与粘度之间的关系；拟合地层压力与累计水侵量之间的关系；对目标水侵气藏的岩样进行气水相对渗透率测试,获得含水饱和度与实验气水相对渗透率比之间的关系；计算不同压力条件下的平均含水饱和度,并得到其与压力之间的关系；将所述平均含水饱和度代入所述含水饱和度与实验气水相对渗透率比之间的关系中,获得实际的气水相对渗透率比,并以此获得理论气水相对渗透率比；利用水气比公式,获得水气比、以及压力与水气比之间的关系,并以此确定极限水气比条件下的废弃地层压力。本发明能够获得更符合实际情况的废弃地层压力。(The invention discloses a method for determining the pressure of a water-invaded gas reservoir waste stratum, which comprises the following steps: fitting a relationship between formation pressure and volume coefficient, and a relationship between formation pressure and viscosity; fitting the relation between the formation pressure and the accumulated water invasion; performing gas-water relative permeability test on a rock sample of the target water-invaded gas reservoir to obtain the relation between water saturation and experimental gas-water relative permeability ratio; calculating the average water saturation under different pressure conditions, and obtaining the relation between the average water saturation and the pressure; substituting the average water saturation into the relation between the water saturation and the experimental gas-water relative permeability ratio to obtain an actual gas-water relative permeability ratio and obtain a theoretical gas-water relative permeability ratio; and obtaining the water-gas ratio and the relation between the pressure and the water-gas ratio by using a water-gas ratio formula, and determining the pressure of the waste stratum under the condition of the limit water-gas ratio. The invention can obtain the pressure of the waste stratum which is more in line with the actual situation.)
1. A method for determining the pressure of a water-invaded gas reservoir waste stratum is characterized by comprising the following steps:
acquiring PVT data of a target water-invaded gas reservoir, and obtaining a relation between formation pressure and a volume coefficient and a relation between the formation pressure and viscosity through fitting;
acquiring production dynamic data of a target water invasion gas reservoir, and obtaining a relation between formation pressure and accumulated water invasion amount through fitting;
performing gas-water relative permeability test on a rock sample of the target water-invaded gas reservoir to obtain the relation between water saturation and experimental gas-water relative permeability ratio;
calculating to obtain the average water saturation of the target water cut gas reservoir rock sample under different pressure conditions according to a substance balance principle, and obtaining the relation between the pressure and the average water saturation;
substituting the average water saturation into the relation between the water saturation and the experimental gas-water relative permeability ratio to obtain the actual gas-water relative permeability ratio and the relation between the pressure and the actual gas-water relative permeability ratio, and calculating to obtain the theoretical gas-water relative permeability ratio according to the relation between the pressure and the actual gas-water relative permeability ratio;
obtaining a water-gas ratio and a relation between pressure and the water-gas ratio according to a volume coefficient, viscosity, water invasion and theoretical water-gas relative permeability ratio under a condition without pressure and by combining a water-gas ratio formula;
and determining the pressure of the abandoned formation under the condition of the limit water-gas ratio according to the relation between the pressure and the water-gas ratio.
2. The method of claim 1, wherein the steady state method is used to determine the pressure of the water-invaded gas reservoir formation at the time of the gas-water relative permeability test of the rock sample of the target water-invaded gas reservoir.
3. The method of claim 2, wherein the testing is performed in a steady state method, each rock sample is tested three times, and the average of the three times is used as the final test result.
4. The method of determining water-invaded gas reservoir formation pressure of claim 1 wherein said average water saturation is calculated by the following equation:
in the formula: swAverage water saturation,%; weTo accumulate water intrusion, m3；SwiIs PiWater saturation under pressure,%; g is the geological reserve of the gas reservoir, m3；BgiIs PiVolume coefficient under pressure, m3/m3。
5. The method of determining water-invaded gas reservoir formation pressure of claim 1 wherein said water-gas ratio is calculated by the formula:
in the formula: rsThe water-gas ratio is zero dimension; krg/KrwThe relative permeability ratio of gas and water is dimensionless; mu.sgIs the gas phase viscosity, mPa.s; mu.swIs a liquid phase viscosity, mPa.s; b isgIs the gas phase volume coefficient, m3/m3；BwIs the volume coefficient of liquid phase, m3/m3。
Technical Field
The invention relates to the technical field of water-invasion gas reservoir development, in particular to a method for determining the pressure of a water-invasion gas reservoir waste stratum.
Background
Many foreign scholars consider that the waste formation pressure is the limit formation pressure of a gas well with industrial exploitation value, is the pressure when the gas reservoir yield is reduced to waste yield, and is mainly determined by the gas reservoir burial depth, reservoir heterogeneity, permeability, bottom water energy and the like; the domestic scholars think that the pressure of the waste stratum is determined by combining factors such as geology, mining process technology, gas transmission pressure and economic indexes, the waste conditions of different types of gas reservoirs are different, and the size of the waste conditions influences the recoverable years and the final recovery degree of the gas reservoirs.
The prior art generally adopts an empirical formula method and an economic limit yield method to calculate the pressure of the waste stratum of the gas reservoir. The empirical formula method cannot fully consider the characteristics of gas reservoir fluid, process technology and other factors, and only selects a calculation formula for calculation according to a wide range of gas reservoir types, so that a calculation result and actual results generate large errors; the economic limit yield method only considers the factors of operating cost, unconsidered interest rate, price rise and the like, so that the calculation result is smaller than the actual result. Therefore, it is necessary to develop a determination method suitable for the pressure of the water-invaded gas reservoir waste stratum.
Disclosure of Invention
In view of the above problems, the present invention aims to provide a method for determining the pressure of a water-invaded gas reservoir waste formation.
The technical scheme of the invention is as follows:
a method for determining the pressure of a water-invaded gas reservoir waste stratum comprises the following steps:
acquiring PVT data of a target water-invaded gas reservoir, and obtaining a relation between formation pressure and a volume coefficient and a relation between the formation pressure and viscosity through fitting;
acquiring production dynamic data of a target water invasion gas reservoir, and obtaining a relation between formation pressure and accumulated water invasion amount through fitting;
performing gas-water relative permeability test on a rock sample of the target water-invaded gas reservoir to obtain the relation between water saturation and experimental gas-water relative permeability ratio;
calculating to obtain the average water saturation of the target water cut gas reservoir rock sample under different pressure conditions according to a substance balance principle, and obtaining the relation between the pressure and the average water saturation;
substituting the average water saturation into the relation between the water saturation and the experimental gas-water relative permeability ratio to obtain the actual gas-water relative permeability ratio and the relation between the pressure and the actual gas-water relative permeability ratio, and calculating to obtain the theoretical gas-water relative permeability ratio according to the relation between the pressure and the actual gas-water relative permeability ratio;
obtaining a water-gas ratio and a relation between pressure and the water-gas ratio according to a volume coefficient, viscosity, water invasion and theoretical water-gas relative permeability ratio under a condition without pressure and by combining a water-gas ratio formula;
and determining the pressure of the abandoned formation under the condition of the limit water-gas ratio according to the relation between the pressure and the water-gas ratio.
Preferably, when the gas-water relative permeability of the rock sample of the target water-invaded gas reservoir is tested, a steady-state method is adopted for testing.
Preferably, when the steady state method is used for testing, each rock sample is tested three times, and the average experimental result of the three times is taken as the final experimental result.
Preferably, the average water saturation is calculated by the following formula:
in the formula: swAverage water saturation,%; weTo accumulate water intrusion, m3；SwiIs PiWater saturation under pressure,%; g is the geological reserve of the gas reservoir, m3；BgiIs PiVolume coefficient under pressure, m3/m3。
Preferably, the water-gas ratio is calculated by the following formula:
in the formula: rsThe water-gas ratio is zero dimension; krg/KrwThe relative permeability ratio of gas and water is dimensionless; mu.sgIs the gas phase viscosity, mPa.s; mu.swIs a liquid phase viscosity, mPa.s; b isgIs the gas phase volume coefficient, m3/m3；BwIs the volume coefficient of liquid phase, m3/m3。
The invention has the beneficial effects that:
according to the invention, the water invasion characteristic of the water-gas reservoir and the PVT characteristic of the actual gas reservoir fluid are considered, and an indoor gas-water relative permeability test experiment is combined, so that the water invasion gas reservoir waste formation pressure more conforming to the actual condition can be obtained; meanwhile, the method solves the problem of large error of a calculation result caused by calculating the pressure of the water-invaded gas reservoir waste stratum by using a conventional method, and compared with the prior art, the method is simpler in principle, easy to operate and more suitable for determining the pressure of the water-invaded gas reservoir waste stratum.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic illustration of the relationship between formation pressure and volume factor according to an embodiment of the present invention;
FIG. 2 is a schematic illustration of the relationship between formation pressure and viscosity according to an embodiment of the present invention;
FIG. 3 is a schematic illustration of the relationship between formation pressure and cumulative water intrusion according to one embodiment of the present invention;
FIG. 4 is a schematic illustration of the relationship between water saturation and experimental gas-water relative permeability ratio for one embodiment of the present invention;
FIG. 5 is a schematic illustration of the relationship between pressure and average water saturation for an embodiment of the present invention;
FIG. 6 is a schematic diagram of the relationship between pressure and actual gas-water relative permeability ratio for one embodiment of the present invention;
FIG. 7 is a schematic diagram of the relationship between pressure and water-to-air ratio in accordance with an embodiment of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples. It should be noted that, in the present application, the embodiments and the technical features of the embodiments may be combined with each other without conflict. It is noted that, unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The use of the terms "comprising" or "including" and the like in the present disclosure is intended to mean that the elements or items listed before the term cover the elements or items listed after the term and their equivalents, but not to exclude other elements or items.
The invention provides a method for determining the pressure of a water-invaded gas reservoir waste stratum, which comprises the following steps:
s1: acquiring PVT data of the target water-invaded gas reservoir, wherein the PVT data comprises data such as temperature, pressure, volume coefficient, viscosity and the like monitored in real time in the production process, and obtaining the relation between the formation pressure and the volume coefficient and the relation between the formation pressure and the viscosity through fitting.
S2: and acquiring production dynamic data of the target water invasion gas reservoir, wherein the production dynamic data comprises real-time monitored pressure and accumulated water invasion in the production process, and the relation between the formation pressure and the accumulated water invasion is obtained through fitting.
S3: and carrying out gas-water relative permeability test on the rock sample of the target water invasion gas reservoir to obtain the relation between the water saturation and the experimental gas-water relative permeability ratio.
In a specific embodiment, when the gas-water relative permeability test is carried out on the rock sample of the target water-invaded gas reservoir, the test is carried out by adopting a steady state method. Optionally, when the steady-state method is used for testing, each rock sample is tested three times, and the average experimental result of the three times is taken as the final experimental result.
It should be noted that, in addition to the steady-state method selected in the above embodiment for gas-water relative permeability test, the invention may also adopt an unsteady-state method for gas-water relative permeability test.
S4: according to the material balance principle, calculating by the formula (1) to obtain the average water saturation of the target water cut gas reservoir rock sample under different pressure conditions, and obtaining the relation between the pressure and the average water saturation;
in the formula: swAverage water saturation,%; weTo accumulate water intrusion, m3；SwiIs PiWater saturation under pressure,%; g is the geological reserve of the gas reservoir, m3；BgiIs PiVolume coefficient under pressure, m3/m3。
S5: substituting the average water saturation into the relation between the water saturation and the experimental gas-water relative permeability ratio to obtain the actual gas-water relative permeability ratio and the relation between the pressure and the actual gas-water relative permeability ratio, and calculating to obtain the theoretical gas-water relative permeability ratio according to the relation between the pressure and the actual gas-water relative permeability ratio;
s6: obtaining the water-gas ratio and the relation between the pressure and the water-gas ratio according to the volume coefficient, the viscosity, the water invasion amount and the theoretical water-gas relative permeability ratio without pressure and by combining a water-gas ratio formula shown in the formula (2);
in the formula: rsThe water-gas ratio is zero dimension; krg/KrwThe relative permeability ratio of gas and water is dimensionless; mu.sgIs the gas phase viscosity, mPa.s; mu.swIs a liquid phase viscosity, mPa.s; b isgIs the gas phase volume coefficient, m3/m3；BwIs the volume coefficient of liquid phase, m3/m3。
S7: and determining the pressure of the abandoned formation under the condition of the limit water-gas ratio according to the relation between the pressure and the water-gas ratio.
In the development process of a gas reservoir, the recoverable life and the final recovery degree of the gas reservoir are influenced by the pressure of the waste stratum, and the influence factors of the pressure of the waste stratum of different types of gas reservoirs are different. According to the method, the gas reservoir fluid property and the influence of water invasion on the pressure of the abandoned formation in the exploitation process are considered, so that the method is more pertinent, and the obtained pressure result of the abandoned formation is more in line with the actual situation of water invasion of the gas reservoir.
In a specific embodiment, taking a water-invaded gas reservoir as an example, the method for determining the pressure of the abandoned formation of the water-invaded gas reservoir comprises the following steps:
(1) PVT data were obtained for the target water invaded gas reservoir with results as shown in table 1:
TABLE 1 PVT data for target water invaded gas reservoir (43.4 ℃)
Pressure (MPa)
Volume factor (10)-3m3/m3)
Viscosity (10)-3mPa·s)
34.474
3.188
33.90
27.579
3.719
26.15
20.684
4.719
20.46
13.789
7.014
16.24
10.342
9.475
14.54
6.895
14.630
13.07
5.729
17.853
12.61
4.826
21.420
12.28
3.792
27.653
11.91
2.758
38.230
11.55
2.310
45.762
11.40
The data of table 1 were fitted to yield the relationship between formation pressure and volume coefficient as shown in fig. 1 and the relationship between formation pressure and viscosity as shown in fig. 2.
As can be seen from FIG. 1, the pressure is in a power function relationship with the volume coefficient, and the maximum volume coefficient is 45.76210 when the pressure is 2.310MPa-3m3/m3(ii) a When the pressure is less than 10MPa, the volume coefficient is sharply reduced along with the increase of the pressure; when the pressure is more than 10MPa, the volume coefficient is slowly reduced along with the increase of the pressure; the minimum volume coefficient is 3.18810 when the pressure is 34.474MPa- 3m3/m3。
As can be seen from FIG. 2, the pressure is exponential to the viscosity, and the viscosity is at least 11.410 at 2.310MPa- 3mPa · s, pressure 34.474MPa, viscosity up to 33.910-3mPa · s, and the viscosity increases more and more with the increasing pressure.
(2) Dynamic data of production of the target water invaded gas reservoir were obtained, and the results are shown in table 2:
TABLE 2 production dynamics data for target water invaded gas reservoir
Pressure (MPa)
Cumulative water intrusion (10)4m3)
Pressure (MPa)
Cumulative water intrusion (10)4m3)
9.8
0
8.21
390.5962799
9.77
0.019595102
7.71
732.8741569
9.75
0.051152652
7.5
734.1375754
9.74
0.117752967
7.2
1205.429709
9.73
0.206013602
6.84
1809.168971
9.26
23.89148283
6.87
1854.180522
8.71
124.7002288
6.75
2036.73387
8.45
127.1780511
6.44
2443.534462
8.27
343.9967337
6.13
3123.161035
8.25
345.4120492
5.87
3698.928299
8.21
390.5962799
5.83
3700.251343
The data of table 2 were fitted to yield the relationship between formation pressure and cumulative water invasion as shown in fig. 3.
As can be seen from FIG. 3, the cumulative water invasion is quadratic in pressure, the original formation pressure of the formation is 9.8MPa, the formation water invasion is weak at the beginning, the water invasion begins to increase when the pressure is reduced to 9.26MPa, and the cumulative water invasion reaches 3700.2513X 10 when the pressure is reduced to 5.83MPa4m3。
(3) And (3) performing gas-water relative permeability test on the rock sample of the target water-invaded gas reservoir by adopting a steady-state method, wherein the test result is shown in table 3:
TABLE 3 gas-water relative permeability test results
Water saturation (%)
Experiment Krg/Krw
26.35
217.75
38.36
100.35
51.79
25.125
61.5
0.694117647
76.38
0.004012036
The data from table 3 were fitted to yield the relationship between water saturation and experimental gas-water relative permeability ratio as shown in figure 4.
As can be seen from FIG. 4, the water saturation and the gas-water relative permeability ratio are in a power function relationship, when the water saturation is small, the gas-water relative permeability is large, along with the increase of the water saturation, the gas-water relative permeability is sharply reduced, and when the water saturation is 60%, the relative permeability is close to 0.
(4) Calculating the average water saturation of the target water invaded gas reservoir rock sample under different pressure conditions according to the formula (1), and it should be noted that in the embodiment, the geological reserve of the target water invaded gas reservoir is 67.48 × 108m3The calculation results are shown in table 4:
TABLE 4 calculation of average Water saturation
Pressure (MPa)
Average water saturation (%)
6.895
0.446322782
5.729
0.692390642
4.826
0.949377556
3.792
1.314851086
2.758
1.756345251
2.31
1.971234979
The data of table 4 were fitted to obtain the relationship between pressure and average water saturation as shown in fig. 5.
As can be seen from FIG. 5, the average water saturation is logarithmic to the pressure, and as the pressure is continuously decreased, the average water saturation gradually increases, thus reflecting the water invasion process.
(5) Substituting the average water saturation obtained in the step (4) into the relation between the water saturation obtained in the step (3) and the experimental gas-water relative permeability ratio to obtain the actual gas-water relative permeability ratio, wherein the result is shown in table 5:
TABLE 5 calculation of the actual versus theoretical gas-water relative permeability ratio
Pressure (MPa)
Actual Krg/Krw
Theory Krg/Krw
6.895
8.015041447
4.981549323
5.729
0.120711011
0.137450744
4.826
0.00591389
0.008523596
3.792
0.000263292
0.000353119
2.758
1.65598E-05
1.46291E-05
2.31
5.49638E-06
3.68245E-06
And fitting the data of the table 5 to obtain the relationship between the pressure and the actual gas-water relative permeability ratio shown in fig. 6, and calculating to obtain the theoretical gas-water relative permeability ratio according to the relationship between the pressure and the actual gas-water relative permeability ratio, wherein the result is shown in the table 5.
(6) The water-air ratio under different pressure conditions was calculated according to equation (2), and the results are shown in table 6:
TABLE 6 Water-to-air ratio calculation results
Pressure (MPa)
Theory Krg/Krw
μg(10-3mPa·s)
Bg(10-3m3/m3)
Water-to-gas ratio
6.895
4.981549323
13.12521172
14.86488619
0.391654816
5.729
0.137450744
12.62094
17.92012917
16.45453984
4.826
0.008523596
12.24376147
21.30605599
306.051887
3.792
0.000353119
11.8256883
27.17468533
9100.604831
2.758
1.46291E-05
11.42189057
37.46994514
292551.6322
The data of table 6 were fitted to obtain the relationship between pressure and water-gas ratio as shown in fig. 7.
(7) And (4) determining the pressure of the abandoned formation under the condition of the limit water-gas ratio according to the relation between the pressure obtained in the step (6) and the water-gas ratio.
In this embodiment, when the water-air ratio is 30 × 104m3/m3In time, the calculated pressure value of the waste stratum is 4.6984MPa, and the recoverable year is 5.118 years; when the water-gas ratio is 20 multiplied by 104m3/m3In time, the calculated pressure value of the waste stratum is 4.8305MPa, and the recoverable year is 4.52 years; since the water-air ratio is difficult to reach 30X 104m3/m3 when no foam is added, the limit pressure calculated according to 30 is obviously small, and therefore the water-air ratio is 20X 104m3/m3The value of (d) is used as a limiting water gas ratio, and the calculated abandonment formation pressure of 4.8305MPa is the final abandonment formation pressure result.
It should be noted that the limit water-gas ratios of different target water-invasion gas reservoirs are different, and the specific limit water-gas ratio is determined by those skilled in the art according to the mining area, the well type, the construction conditions, and the like of the target gas reservoir.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：一种岩土地质开采装置