CN117609668A - Calculation method for average formation pressure drop rate - Google Patents
Calculation method for average formation pressure drop rate Download PDFInfo
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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
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
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Abstract
The invention relates to the technical field of oil and gas field development, in particular to a calculation method of average formation pressure drop rate. Method for calculating average formation pressure drop rate, and drawing isothermal compression coefficient and average formation pressure of natural gasCurve of isothermal compression coefficient and average formation pressure of natural gas by multiplication of meditation functionFitting the curve to obtain a fitted exponentiation coefficient alpha and an exponentiation exponent beta; and then the average formation pressure reducing speed is obtained through calculation of the formula (8). The invention utilizes the exponentiation function relation between the isothermal compression coefficient and the average formation pressure to realize the rapid calculation of the average formation pressure drop rate, and the average lamination is analyzedThe force variation law provides a reference and a reference.
Description
Technical Field
The invention relates to the technical field of oil and gas field development, in particular to a calculation method of average formation pressure drop rate.
Background
The average formation pressure is a key index in gas reservoir development, is an index for acquiring other development indexes, recognizes and grasps the change rule of the average formation pressure, and has important significance for gas reservoir development. The change rule of the average formation pressure comprises the value and the descending rate of the average formation pressure, and the calculation method of the average formation pressure value is quite large. According to the physical meaning, the decreasing rate of the average formation pressure refers to the derivative of the average formation pressure with respect to time at any moment, and the existing research on the decreasing rate of the average formation pressure is mainly obtained by the difference value of the average formation pressure at adjacent moments, and the derivative of the average formation pressure with respect to time is not directly calculated.
Starting from the isothermal compression coefficient, the calculation method for the average formation pressure reduction rate is established by utilizing the change rule of the isothermal compression coefficient along with the average formation pressure, so that the change rule of the average formation pressure can be recognized, theoretical reference can be provided for other researches, and the method has a strong practical application value for gas reservoir development.
Disclosure of Invention
The present invention aims to solve the above problems and provide a method for calculating an average formation pressure drop rate.
The technical scheme of the invention is as follows:
isothermal compression coefficient C of natural gas under stratum condition g Is defined as:
wherein: c (C) g Is the isothermal compression coefficient of natural gas, MPa -1 ；
V g Is the volume of natural gas under stratum conditions, m 3 ；
Is the average formation pressure, MPa;
separating the variables in the formula (1), and deriving the production time t to obtain:
wherein: t is the production time, d;
q g for gas production under formation conditions, m 3 /d；
Is the average formation pressure drop rate, MPa/d;
gas volume coefficient B g Is defined as:
wherein: b (B) g Is a gas volume coefficient, dimensionless;
q sc is the gas production rate under the ground standard condition, m 3 /d；
Z r Is thatCorresponding deviation coefficient, dimensionless;
t is the reservoir temperature, K;
p sc standard pressure, MPa;
Z sc is p sc Corresponding deviation coefficient, dimensionless;
T sc is the standard temperature, K;
substituting the formula (3) into the formula (2) to obtain:
according to the volumetric method, the control reserves of the gas well in the current state are:
wherein: g is the original geological reserve of natural gas, m 3 ；
G p For accumulating gas yield, m 3 ；
Substituting the formula (5) into the formula (4) to obtain:
(6) In the natural gas isothermal compression coefficient C g With average formation pressure p r Changes occur, resulting in the (6) form being more difficult to solve directly. Isothermal compression coefficient C of natural gas g The method belongs to natural gas high-pressure physical property parameters, and is characterized in that the following high-precision relational expression exists in analysis of natural gas high-pressure physical property data:
wherein: alpha is the isothermal compression coefficient of natural gas and the average formation pressure C g -The curve adopts an exponentiation coefficient obtained by multiplication and meditation function fitting, and has no dimension; beta is the isothermal compression coefficient of natural gas and the average formation pressure C g -/>The curve adopts an exponentiation exponent obtained by multiplication and meditation function fitting, and has no dimension;
substituting the formula (7) into the formula (6), and deriving:
i.e. when knowing the average formation pressure at a certain momentAnd cumulative gas production G p Then, the average formation pressure drop rate can be calculated by adopting the method (8)>
The invention has the technical effects that:
the invention establishes a calculation method of the average formation pressure drop rate, realizes the rapid calculation of the average formation pressure drop rate by utilizing the exponentiation function relation between the isothermal compression coefficient and the average formation pressure, and provides a reference and a reference for analyzing the average formation pressure change rule.
Drawings
FIG. 1 shows the gas yield q under the ground standard condition of well C according to the experimental example of the invention sc Is a change pattern of (a).
FIG. 2 shows the average formation pressure and cumulative gas production G for well C according to an embodiment of the present invention p Is a change pattern of (a).
FIG. 3 shows the isothermal compression coefficient and average formation pressure C of natural gas in well C according to an embodiment of the present invention g -p r Curve fitting the graph.
FIG. 4 is a graph showing the comparison between the average formation pressure drop rate calculated by the method of the present invention and the numerical simulation for well C according to the experimental example of the present invention.
Detailed Description
A calculation method for the average formation pressure drop rate comprises the following steps:
step 1: with isothermal compression coefficient C of natural gas g On the ordinate, in terms of average formation pressurePlotting the isothermal compression coefficient of natural gas and the average formation pressure C g -/>A curve;
isothermal compression coefficient of natural gas by multiplication of the meditation function and average formation pressure C g -Fitting a curve to obtain an exponentiation coefficient alpha and an exponentiation exponent beta;
calculating the average formation pressure drop speed at different production time t through a formula (8)
Specific experimental example-well C
Well C is produced by adopting a mode of pre-setting and post-setting constant pressure, and the natural gas original geological reserve g= 151619000m of well C 3 Gas yield q under ground standard condition sc The change rule of (1) is shown in figure 1; average formation pressureAnd cumulative gas production G p The change rule of (2) is shown in figure 2; the average formation pressure drop rate is calculated by the method provided by the invention.
A calculation method for the average formation pressure drop rate comprises the following steps:
step 1: with isothermal compression coefficient C of natural gas g On the ordinate, in terms of average formation pressurePlotting the isothermal compression coefficient of natural gas and the average formation pressure C g -/>A curve;
isothermal compression coefficient of natural gas by multiplication of the meditation function and average formation pressure C g -Fitting the curve, wherein the fitting process is shown in fig. 3; resulting in an exponentiation coefficient α= 1.74723 and an exponentiation exponent β= -1.19793;
step 2: calculating the average formation pressure drop speed at different production time t through a formula (8)The calculation results are shown in FIG. 4.
Average formation pressure reduction rate calculated by the method provided by the inventionComparing with the numerical simulation results, it can be seen that the calculation result of the invention almost coincides with the numerical simulation results, and has good calculation accuracy, which shows that the invention is suitable for calculating the average formation pressure reduction rate.
Claims (1)
1. A method of calculating an average formation pressure drop rate, characterized by: the method comprises the following steps:
plotting natural gas isothermal compression coefficient and average formation pressureA curve;
isothermal compression coefficient and average formation pressure of natural gas by exponentiation functionFitting a curve to obtain an exponentiation coefficient alpha and an exponentiation exponent beta;
through the following (8)
Wherein:is the average formation pressure drop rate, MPa/d;
is the average formation pressure, MPa;
t is the production time, d;
alpha is the isothermal compression coefficient and average formation pressure of natural gasCurve fitting by exponentiation functionThe obtained exponentiation coefficient is dimensionless;
beta is the isothermal compression coefficient and average formation pressure of natural gasThe curve is fitted through an exponentiation function to obtain an exponentiation exponent without dimension;
q sc is the gas production rate under the ground standard condition, m 3 /d；
G is the original geological reserve of natural gas, m 3 ；
G p For accumulating gas yield, m 3 ；
Calculating to obtain average formation pressure drop rate
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| CN202311580413.7A CN117609668B (en) | 2023-11-24 | 2023-11-24 | Calculation method for average formation pressure drop rate |
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| CN117609668A true CN117609668A (en) | 2024-02-27 |
| CN117609668B CN117609668B (en) | 2024-10-25 |
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6101447A (en) * | 1998-02-12 | 2000-08-08 | Schlumberger Technology Corporation | Oil and gas reservoir production analysis apparatus and method |
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- 2023-11-24 CN CN202311580413.7A patent/CN117609668B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6101447A (en) * | 1998-02-12 | 2000-08-08 | Schlumberger Technology Corporation | Oil and gas reservoir production analysis apparatus and method |
Non-Patent Citations (2)
| Title |
|---|
| 宗鹏 等: "煤储层压力变化规律模拟研究", 煤炭科学技术, vol. 51, no. 8, 5 August 2022 (2022-08-05), pages 169 - 177 * |
| 张磊 等: "气藏平均地层压力跟踪计算新方法", 石油学报, vol. 42, no. 4, 15 April 2021 (2021-04-15), pages 492 - 499 * |
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