CN-121997525-A - Method for evaluating productivity of small-pressure-difference high-yield gas well

CN121997525ACN 121997525 ACN121997525 ACN 121997525ACN-121997525-A

Abstract

The invention discloses a capacity evaluation method of a low-pressure-difference high-yield gas well, which belongs to the technical field of gas well development, and comprises the steps of calculating correction coefficients beta corresponding to different alpha coefficients, drawing correction coefficient beta plates corresponding to different alpha coefficients, collecting typical gas well capacity test data, fitting to obtain Darcy seepage term coefficients A and non-Darcy seepage term coefficients B, calculating unimpeded flow and stable experience number alpha coefficients of the gas well, calculating gas yield corresponding to different gamma-rays based on formation pressure of the gas well with different stable experience number alpha coefficients, darcy seepage term coefficients A in a pressure square form and non-Darcy seepage term coefficients B in a gas well pressure form, adding data into the plates, drawing a one-point method capacity evaluation comprehensive correction plate, calculating gamma-rays by using test oil yield, formation pressure and bottom hole flow pressure of the well, inquiring correction coefficient beta in the comprehensive correction plate, and substituting the calculation formula of the one-point method containing the correction coefficient beta to evaluate the gas well capacity.

Inventors

CAI JUNJUN
LIU WEI
HU YI
JIANG JUN
LI YUEYANG
WANG BEI

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (10)

1. The productivity evaluation method of the low-pressure-difference high-yield gas well is characterized by comprising the following steps of: deducing a theoretical expression of a 'one-point method' productivity evaluation correction coefficient beta; Calculating correction coefficients beta corresponding to different alpha coefficients, and drawing a correction coefficient beta plate corresponding to the different alpha coefficients; Collecting typical gas well productivity test data, fitting to obtain a Darcy seepage term coefficient A in a pressure square form and a non-Darcy seepage term coefficient B in a gas well pressure form, and calculating an unobstructed flow and stable empirical number alpha coefficient of the gas well; Calculating gas production amounts corresponding to different gammas on the basis of stratum pressure of the gas well with different stable experience alpha coefficients, darcy seepage term coefficient A in a pressure square form and non-Darcy seepage term coefficient B in a gas well pressure form, adding data into a plate of the second step, and drawing a 'one-point method' capacity evaluation comprehensive correction plate; And fifthly, calculating gamma from the oil testing test yield, the formation pressure and the bottom hole flow pressure of the well, inquiring a correction coefficient beta in the plate of the fourth step, substituting a 'one-point method' calculation formula containing the correction coefficient beta, and evaluating the productivity of the gas well.
2. The method for evaluating the productivity of a low-differential-pressure high-yield gas well according to claim 1, wherein in the first step, the gas well correction coefficient beta is only related to the stable empirical number alpha and the ratio of the production differential pressure to the formation pressure gamma, and the expression is as follows: Wherein gamma is the ratio of the production pressure difference of the gas well to the formation pressure; p R is the stratum pressure of a certain system in the productivity test well, the unit is MPa, and p wf is the bottom hole flow pressure, and the unit is MPa.
3. The method for evaluating the productivity of a low-differential-pressure high-yield gas well according to claim 2, wherein the stable empirical number alpha is determined by the following formula: wherein A is the Darcy seepage term coefficient of the square form of the gas well pressure, MPa 2 ·(10 4 m 3 /d) -1, and B is the non-Darcy seepage term coefficient of the square form of the gas well pressure, MPa 2 ·(10 4 m 3 /d) -2.
4. The method of producing a high yield gas well with small pressure difference according to claim 3, wherein the correction factor β is calculated based on the different γ and the different α coefficients in the first step.
5. The method of producing capacity of a low pressure differential high yield gas well according to claim 4, wherein in said third step, the gas well production capacity test data comprises formation pressure, gas production and bottom hole flow pressures corresponding to different gas production.
6. The method for evaluating the productivity of a low-differential-pressure high-yield gas well according to claim 5, wherein in the third step, the Darcy seepage term coefficient A in the form of square gas well pressure and the non-Darcy seepage term coefficient B in the form of gas well pressure are determined by fitting productivity test wells, and the productivity equation when gas well seepage enters a quasi-steady state is as follows: the expressions of A are respectively: The expressions of B are respectively: Wherein A represents a gas well stable Darcy seepage term coefficient, MPa 2 /(10 4 m 3 /d, B represents a gas well stable non-Darcy seepage term coefficient, MPa 2 /(10 4 m 3 /d) 2 , K represents gas reservoir permeability, 10 -3 μm 2 , h is reservoir thickness, m; Representing temperature, K; is the viscosity of the gas, mPas; The method comprises the steps of expressing deviation factors, dimensionless, r e being the well radius of a gas release zone, m, r w being the well radius of a borehole, m, h reservoir thickness in m, S being the skin factor, dimensionless, D being the non-Darcy seepage coefficient, (m 3 /d) -1 ).
7. The method for evaluating the productivity of a low pressure differential high-yield gas well according to claim 6, wherein in the third step, the productivity of the gas well is determined by A, B and p R , and the expression is: The method comprises the steps of q g , wherein the unit of gas yield is 10 4 m 3 /d, A represents a stable Darcy seepage term coefficient of a gas well, MPa 2 /(10 4 m 3 /d, B represents a stable non-Darcy seepage term coefficient of the gas well, MPa 2 /(10 4 m 3 /d) 2 , gamma is the ratio of the production pressure difference of the gas well to the formation pressure, p R is the formation pressure of a certain system in a productivity test well, the unit of the formation pressure is MPa, and p w f is the bottom hole flow pressure, and the unit of the bottom hole flow pressure is MPa.
8. The method for evaluating the productivity of a low-differential-pressure high-yield gas well according to claim 7, wherein in the fifth step, gamma is calculated from the test oil yield, the formation pressure and the bottom hole flow pressure of the well, and the alpha coefficient of the gas well is inquired.
9. The method for evaluating the productivity of the low-differential-pressure high-productivity gas well according to claim 8, wherein the correction coefficient beta is queried in the plate of the fourth step according to the gamma and alpha coefficients, and finally the productivity of the gas well is evaluated by a 'one-point method' calculation formula containing the correction coefficient beta.
10. The method for evaluating the productivity of a low-differential-pressure high-yield gas well according to claim 9, wherein the expression of the gas well q AOF is: Wherein p R is the formation pressure of a certain system in the productivity test well, the unit is MPa, p wf is the bottom hole flow pressure, the unit is MPa, beta is the correction coefficient, and q g is the test gas production, and the unit is 10 4 m 3 /d.

Description

Method for evaluating productivity of small-pressure-difference high-yield gas well Technical Field The invention belongs to the technical field of gas well development, and particularly relates to a productivity evaluation method of a low-pressure-difference high-yield gas well. Background In 1987, chen Yuanqian uses the square pressure form binomial energy production equation as the basis, takes the average value of 0.25 of the stable experience numbers (hereinafter referred to as "alpha") of 68 test points of 16 gas wells of 6 gas fields in China, and deduces a "one-point method" energy production evaluation calculation formula, which is generally called as a conventional "one-point method" in the industry. Because the alpha coefficient is valued, the conventional 'one-point method' can calculate the absolute unimpeded flow (hereinafter called q AOF) of the gas well only by one test system, and further evaluate the productivity of the gas well. The method has the advantages of integrating theories, experience and convenience, has the characteristics of convenient application and acceptable error, and therefore gradually becomes a main method for evaluating the single-point test productivity of the gas well. In the past 20 th century, china oil and southwest oil and gas field companies found a group of gas reservoirs with high permeability and high gas well yield in Sichuan basin, such as Feixian oolitic beach gas reservoirs in northeast China, chuanzhong Anyue Temple group gas reservoirs and the like, and the alpha coefficient of gas wells in the gas reservoirs is generally smaller than 0.25. The mining field application finds that the conventional 'one-point method' is adopted to multiply the gas well q AOF, and if the alpha coefficient of the gas well is smaller, the evaluation error of the conventional 'one-point method' is larger. Taking an MX145 well as an example, the formation pressure is 74.5MPa, the production pressure difference of a special well completion test oil test well is 0.029-0.266 MPa, the daily gas yield is 22.58-82.84×104m3/d, the binomial q AOF is 1077×104m3/d, and the calculation result of the conventional one-point method is 3139-7226×104m3/d. For this type of gas well, it should be careful to choose a conventional "one point method" to evaluate the gas well q AOF. On the other hand, if the alpha coefficient of the gas well is greater than 0.25, the conventional "one point method" will underestimate the gas well q AOF to some extent. The alpha coefficient range in the Chen Shi 'one-point method' original document is examined to be 0.1374-0.3436, so that if the alpha coefficient of the gas well is not in the range, larger calculation errors can be possibly generated, and particularly for a high-permeability high-yield small alpha coefficient gas well, the conventional 'one-point method' calculation errors are unacceptable. Disclosure of Invention In order to solve the technical problems, the invention provides a productivity evaluation method of a low-pressure-difference high-yield gas well, which can improve the conventional 'one-point method' productivity evaluation precision, and particularly aims at the low-pressure-difference high-yield gas well. The invention aims at realizing the following technical scheme: The productivity evaluation method of the low-pressure-difference high-yield gas well comprises the following steps of: deducing a theoretical expression of a 'one-point method' productivity evaluation correction coefficient beta; Calculating correction coefficients beta corresponding to different alpha coefficients, and drawing a correction coefficient beta plate corresponding to the different alpha coefficients; Collecting typical gas well productivity test data, fitting to obtain a Darcy seepage term coefficient A in a pressure square form and a non-Darcy seepage term coefficient B in a gas well pressure form, and calculating an unobstructed flow and stable empirical number alpha coefficient of the gas well; Calculating gas production amounts corresponding to different gammas on the basis of stratum pressure of the gas well with different stable experience alpha coefficients, darcy seepage term coefficient A in a pressure square form and non-Darcy seepage term coefficient B in a gas well pressure form, adding data into a plate of the second step, and drawing a 'one-point method' capacity evaluation comprehensive correction plate; And fifthly, calculating gamma from the oil testing test yield, the formation pressure and the bottom hole flow pressure of the well, inquiring a correction coefficient beta in the plate of the fourth step, substituting a 'one-point method' calculation formula containing the correction coefficient beta, and evaluating the productivity of the gas well. Preferably, in the first step, the correction coefficient β of the gas well is related to the stable empirical number α and the ratio γ of the production pressure difference to the formation pre