CN112392473B - Method for evaluating injection and production capacity of low-permeability gas reservoir gas well - Google Patents
Method for evaluating injection and production capacity of low-permeability gas reservoir gas well Download PDFInfo
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Abstract
The invention belongs to the technical field of injection and production of low-permeability tight gas reservoir gas wells, and particularly relates to a method for evaluating injection and production capacity of a low-permeability tight gas reservoir gas well. According to the method, through a gas substance balance equation, a gas inflow equation during gas production and a gas outflow equation during gas production, a gas injection inflow equation and a gas injection outflow equation are obtained, so that a gas well yield relation under different stratum pressures and a gas well gas injection relation under different stratum pressures are obtained, and then gas production capacity evaluation and gas injection capacity evaluation are carried out; and performing operation management on the gas storage according to the evaluation result. The method comprehensively utilizes the inflow equation during gas production, the outflow equation during gas production and the material balance equation, realizes quantitative fine prediction of the gas injection and production amount of the gas reservoir, and can predict daily pressure change and gas injection and production amount of the gas reservoir. The method predicts the utilization of the previous period data to estimate the next period index, has timeliness and improves accuracy. The invention fills the blank of the injection and production capacity evaluation of the reconstructed gas storage of the low permeability gas reservoir.
Description
Technical Field
The invention belongs to the technical field of injection and production of low-permeability tight gas reservoir gas wells, and particularly relates to a method for evaluating injection and production capacity of a low-permeability tight gas reservoir gas well.
Background
The underground gas storage is an underground artificial gas reservoir, and has great significance in emergency gas supply, strategic reserve and the like. The gas storage has the production characteristics of cyclic reciprocation and quick-in and quick-out, and the gas well is required to have stronger injection and production capacity. Accurate evaluation of gas well injection and production capability is a key for ensuring safe and stable operation of a gas storage.
The gas well injection and production capacity evaluation usually adopts a node method, namely, based on a system analysis idea, the injection and production capacity under different stratum pressure conditions is predicted by drawing an inflow and outflow curve and an injection and absorption curve. For medium-high permeability gas reservoirs, the pressure conduction speed is high, and the integral pressure change of the reservoir area is relatively balanced. However, for a hypotonic gas reservoir, local pressure holding and pressure drop funnels can be caused by rapid injection and production, the pressure distribution of a plane stratum is unbalanced, and the prediction difficulty is high. The method is influenced by the accuracy of formation pressure prediction, and a large error may exist in the gas well injection and production capacity of the whole period simply by using a node method.
Disclosure of Invention
The invention provides a low-permeability gas reservoir type gas storage well injection and production capacity evaluation method, and aims to quantitatively and finely predict the gas injection and production capacity of a gas reservoir.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a method for evaluating the injection and production capacities of a low-permeability gas reservoir gas well comprises the following steps,
step one: obtaining a gas injection inflow equation and a gas injection outflow equation through a gas substance balance equation, a gas inflow equation during gas production and a gas outflow equation during gas production, so as to obtain a gas well yield relation under different formation pressures and a gas well gas injection relation under different formation pressures;
step two: carrying out gas production capacity evaluation;
step three: performing gas injection capability evaluation;
step four: and (3) performing operation management on the gas storage according to the evaluation results obtained in the second step and the third step.
The gas well yield relation equation under different formation pressures and the gas well gas injection relation equation under different formation pressures in the first step are obtained as follows:
equation of gas mass balance
G＝G Collecting
Wherein:
p is the formation pressure at the end of injection/production and MPa;
P i the formation pressure is the initial injection/production period and is MPa;
z is a compression factor corresponding to the pressure p, and is dimensionless;
Z i is the pressure p i Corresponding compression factors, dimensionless;
G p to accumulate gas injection/production rate 10 4 m 3 ；
G is a movable storage capacity, 10 4 m 3 ；
During gas production, p in formula (1) i More than p, gp is the accumulated gas production and is a positive value; when injecting gas, p in formula (1) i P is less than Gp is the accumulated gas injection quantity, and is a negative value;
inflow equation (2) during gas production
Wherein:
m (p) is the pseudo pressure, MPa 2 /mPa·s；
Pi is the formation pressure in the early stage of gas production and MPa;
pwf is the formation pressure at the end of gas production and MPa;
q collecting Is daily gas production, 10 4 m 3 /d；
A is the Darcy flow coefficient;
b is the non-Darcy flow coefficient;
μ g is the viscosity of the gas, mPas;
z is a natural gas deviation coefficient, and is dimensionless;
flow equation during gas production (4)
Wherein:
pwf is the bottom hole pressure of the gas well and MPa;
ptf is the wellhead pressure of the gas well and MPa;
twf is the bottom hole temperature of the gas well in the flow string, K;
ttf is the wellhead temperature of the gas well in the flow string, K;
the intersection point of inflow and outflow curves during gas production is the gas well yield under different stratum pressures, as shown in formula (5):
q collecting ＝a 1 ·p 3 +b 1 ·p 2 +c 1 ·p+d 1 (5)
Wherein:
a 1 the three-term coefficients of the inflow-outflow intersection curve of the produced gas;
b 1 the method comprises the steps of flowing in and out of a cross curve binomial coefficient for the produced gas;
c 1 a polynomial coefficient for inflow and outflow intersection curves for the produced gas stream;
d 1 a constant term for inflow and outflow intersection curves of the produced gas;
the gas injection and gas production are the reverse processes, so the gas injection inflow equation is the gas production outflow equation, namely equation (4), and Pwf is larger than Pi; the gas injection outflow equation also corresponds to the gas intake inflow equation, as shown in (6)
Wherein: q Pouring Daily gas filling amount of 10 4 m 3 /d；
Similarly, the intersection point of inflow and outflow curves during gas injection is the gas well gas injection amount under different formation pressures, as shown in formula (7):
q pouring ＝a 2 ·p 3 +b 2 ·p 2 +c 2 ·p+d 2 (7)
a 2 The three-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
b 2 the two-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
c 2 a polynomial coefficient for the inflow and outflow intersection curves of the gas injection;
d 2 the constant term of the intersection curve of inflow and outflow of gas injection.
The method for evaluating the gas production capacity in the second step comprises the following steps:
the first step: the historical gas production data of the previous period is carried into a gas material balance equation to obtain the movable reservoir capacity in the gas production period of the evaluation gas well, which is marked as G Collecting 。
And a second step of: drawing a dynamic flow-in curve and a dynamic flow-out curve of the produced gas under different formation pressures by using a flow-in equation and a flow-out equation during gas production, wherein the intersection point of the curves is the yield of the gas well under different formation pressures, and thus the relation between the regressive formation pressure and the yield is obtained;
and a third step of: static pressure p of stratum before gas production Initial picking Carrying out regression formation pressure and yield relation, and calculating to obtain gas well first day gas production q 1 st part ；
Fourth step: static pressure p of stratum before gas production Initial picking Movable reservoir volume G in gas production period Collecting Gas production rate q on first day 1 st part Is carried into a gas material balance equation, and the stratum pressure p after gas production for one day is calculated 1 st part ；
Fifth step: formation pressure p after one day of gas production 1 st part Bringing into the relation between regressive formation pressure and yield to obtain the gas well next-day gas production q Adopts 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p 1 st part 、G Collecting 、q Adopts 2 Bringing into a gas material balance equation to obtain the formation pressure p of the next day Adopts 2 。
Sixth step: similarly, the ith gas production q is calculated iteratively by using the gas material balance equation and regressive formation pressure and yield relationship Picking i And ith formation pressure p Picking i ；
Seventh step: daily gas production q for gas well Picking i And (5) accumulating and summing to obtain a prediction result of the gas production of the new period gas well.
The method for evaluating the gas injection capacity in the third step comprises the following steps:
the first step: the historical production data of the gas injection in the previous period are carried into a gas material balance equation, and the movable reservoir capacity G in the gas injection period of the gas well is evaluated Pouring ；
And a second step of: drawing a gas injection inflow dynamic curve and a gas injection outflow dynamic curve under different formation pressures by using a gas injection inflow equation and a gas injection outflow equation, wherein the intersection point of the curves is the gas well gas injection quantity under different formation pressures, and thus a regression formation pressure and gas injection quantity relational expression is obtained;
and a third step of: static pressure p of stratum before gas injection Injecting the primary injection Carrying out regression formation pressure and gas injection quantity relation, and calculating to obtain gas well first day gas injection quantity q Note 1 ；
Fourth step: static pressure p of stratum before gas injection Injecting the primary injection Movable reservoir volume G in gas injection period Pouring Air injection quantity q on first day Note 1 Carrying out gas substance balance equation, and calculating to obtain formation pressure p after one day of gas injection Note 1 ；
Fifth step: formation pressure p after one day of gas injection Note 1 Carrying out regression on the relation between formation pressure and gas injection quantity to obtain the gas injection quantity q of the gas well on the next day Note 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p Note 1 、G Pouring 、q Note 2 Bringing into a gas material balance equation to obtain the formation pressure of the next dayp Note 2 ；
Sixth step: similarly, the ith gas injection quantity q is calculated by iteration through the relation between the regressive formation pressure and the gas injection quantity and the gas material balance equation Annotate i And ith formation pressure p Annotate i ；
Seventh step: daily gas injection q for gas well Annotate i And (5) accumulating and summing to obtain a prediction result of the gas injection quantity of the gas well in the new period.
The beneficial effects are that:
1. the method comprehensively utilizes the outflow equation, the material balance equation and the material balance equation during gas production, realizes quantitative fine prediction of the gas injection and production amount of the gas reservoir, and can predict daily pressure change and the gas injection and production amount of the gas reservoir.
2. The invention estimates the index of the next period by using the data of the previous period, and the prediction has timeliness and improves the accuracy.
3. The invention fills the blank of the reconstruction of the gas storage in the low permeability gas reservoir and the evaluation of the injection and production capacity.
The foregoing description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention more clearly understood, it can be implemented according to the content of the specification, and the following detailed description of the preferred embodiments of the present invention will be given.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments 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 other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a graph of the pressure drop across XX-1 well of XX gas storage in an embodiment of the invention;
FIG. 2 is a graph of XX gas storage XX-1 well formation pressure versus daily gas production in an embodiment of the invention;
FIG. 3 is a graph of a XX-1 well injection pressure rise for a XX gas storage in an embodiment of the invention;
FIG. 4 is a graph of XX gas storage XX-1 well formation pressure versus daily gas injection amount in an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment one:
a method for evaluating the injection and production capacities of a low-permeability gas reservoir gas well comprises the following steps,
step one: obtaining a gas injection inflow equation and a gas injection outflow equation through a gas substance balance equation, a gas inflow equation during gas production and a gas outflow equation during gas production, so as to obtain a gas well yield relation under different formation pressures and a gas well gas injection relation under different formation pressures;
step two: carrying out gas production capacity evaluation;
step three: performing gas injection capability evaluation;
step four: and (3) performing operation management on the gas storage according to the evaluation results obtained in the second step and the third step.
The method comprehensively utilizes the outflow equation, the material balance equation and the material balance equation during gas production, realizes quantitative fine prediction of the gas injection and production amount of the gas reservoir, and can predict daily pressure change and the gas injection and production amount of the gas reservoir. The method has timeliness in prediction and improves accuracy.
The embodiment applies the gas material balance equation, the inflow equation during gas production and the outflow equation during gas production in the prior art to the evaluation of the injection and production capacity of the reconstructed gas storage of the low permeability gas reservoir, and fills the blank of the evaluation of the injection and production capacity of the reconstructed gas storage of the low permeability gas reservoir.
Embodiment two:
on the basis of the first embodiment, the process for obtaining the gas well yield relation under different formation pressures and the gas well gas injection relation under different formation pressures in the first step is as follows:
equation of gas mass balance
G＝G Collecting
Wherein:
p is the formation pressure at the end of injection/production and MPa;
P i the formation pressure is the initial injection/production period and is MPa;
z is a compression factor corresponding to the pressure p, and is dimensionless;
Z i is the pressure p i Corresponding compression factors, dimensionless;
G p to accumulate gas injection/production rate 10 4 m 3 ；
G is a movable storage capacity, 10 4 m 3 ；
During gas production, p in formula (1) i More than p, gp is the accumulated gas production and is a positive value; when injecting gas, p in formula (1) i P is less than Gp is the accumulated gas injection quantity, and is a negative value;
inflow equation (2) during gas production
Wherein:
m (p) is the pseudo pressure, MPa 2 /mPa·s；
Pi is the formation pressure in the early stage of gas production and MPa;
pwf is the formation pressure at the end of gas production and MPa;
q collecting Is daily gas production, 10 4 m 3 /d；
A is the Darcy flow coefficient;
b is the non-Darcy flow coefficient;
μ g is the viscosity of the gas, mPas;
z is a natural gas deviation coefficient, and is dimensionless;
flow equation during gas production (4)
Wherein:
pwf is the bottom hole pressure of the gas well and MPa;
ptf is the wellhead pressure of the gas well and MPa;
twf is the bottom hole temperature of the gas well in the flow string, K;
ttf is the wellhead temperature of the gas well in the flow string, K;
the intersection point of inflow and outflow curves during gas production is the gas well yield under different stratum pressures, as shown in formula (5):
q collecting ＝a 1 ·p 3 +b 1 ·p 2 +c 1 ·p+d 1 (5)
a 1 The three-term coefficients of the inflow-outflow intersection curve of the produced gas;
b 1 the method comprises the steps of flowing in and out of a cross curve binomial coefficient for the produced gas;
c 1 a polynomial coefficient for inflow and outflow intersection curves for the produced gas stream;
d 1 a constant term for inflow and outflow intersection curves of the produced gas;
the gas injection and gas production are the reverse processes, so the gas injection inflow equation is the gas production outflow equation, namely equation (4), and Pwf is larger than Pi; the gas injection outflow equation also corresponds to the gas intake inflow equation, as shown in (6)
Wherein: q Pouring Daily gas filling amount of 10 4 m 3 /d；
Similarly, the intersection point of inflow and outflow curves during gas injection is the gas well gas injection amount under different formation pressures, as shown in formula (7):
q pouring ＝a 2 ·p 3 +b 2 ·p 2 +c 2 ·p+d 2 (7)
a 2 The three-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
b 2 the two-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
c 2 a polynomial coefficient for the inflow and outflow intersection curves of the gas injection;
d 2 the constant term of the intersection curve of inflow and outflow of gas injection.
Further, the method for evaluating the gas production capacity in the second step comprises the following steps:
the first step: the historical gas production data of the previous period is carried into a gas material balance equation to obtain the movable reservoir capacity in the gas production period of the evaluation gas well, which is marked as G Collecting 。
And a second step of: drawing a dynamic flow-in curve and a dynamic flow-out curve of the produced gas under different formation pressures by using a flow-in equation and a flow-out equation during gas production, wherein the intersection point of the curves is the yield of the gas well under different formation pressures, and thus the relation between the regressive formation pressure and the yield is obtained;
and a third step of: static pressure p of stratum before gas production Initial picking Carrying out regression formation pressure and yield relation, and calculating to obtain gas well first day gas production q 1 st part ；
Fourth step: static pressure p of stratum before gas production Initial picking Movable reservoir volume G in gas production period Collecting Gas production rate q on first day 1 st part Is carried into a gas material balance equation, and the stratum pressure p after gas production for one day is calculated 1 st part ；
Fifth step: formation pressure p after one day of gas production 1 st part Bringing into the relation between regressive formation pressure and yield to obtain the gas well next-day gas production q Adopts 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p 1 st part 、G Collecting 、q Adopts 2 Bringing into a gas material balance equation to obtain the formation pressure p of the next day Adopts 2 。
Sixth step: similarly, the ith gas production q is calculated iteratively by using the gas material balance equation and regressive formation pressure and yield relationship Picking i And ith formation pressure p Picking i ；
Seventh step: daily gas production q for gas well Picking i And (5) accumulating and summing to obtain a prediction result of the gas production of the new period gas well.
Further, the method for evaluating the gas injection capacity in the third step comprises the following steps:
the first step: the historical production data of the gas injection in the previous period are carried into a gas material balance equation, and the movable reservoir capacity G in the gas injection period of the gas well is evaluated Pouring ；
And a second step of: drawing a gas injection inflow dynamic curve and a gas injection outflow dynamic curve under different formation pressures by using a gas injection inflow equation and a gas injection outflow equation, wherein the intersection point of the curves is the gas well gas injection quantity under different formation pressures, and thus a regression formation pressure and gas injection quantity relational expression is obtained;
and a third step of: static pressure p of stratum before gas injection Injecting the primary injection Carrying out regression formation pressure and gas injection quantity relation, and calculating to obtain gas well first day gas injection quantity q Note 1 ；
Fourth step: static pressure p of stratum before gas injection Injecting the primary injection Movable reservoir volume G in gas injection period Pouring Air injection quantity q on first day Note 1 Carrying out gas substance balance equation, and calculating to obtain formation pressure p after one day of gas injection Note 1 ；
Fifth step: formation pressure p after one day of gas injection Note 1 Carrying out regression on the relation between formation pressure and gas injection quantity to obtain the gas injection quantity q of the gas well on the next day Note 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p Note 1 、G Pouring 、q Note 2 Bringing into a gas material balance equation to obtain the formation pressure p of the next day Note 2 ；
Sixth step: similarly, the ith gas injection quantity q is calculated by iteration through the relation between the regressive formation pressure and the gas injection quantity and the gas material balance equation Annotate i And ith formation pressure p Annotate i ；
Seventh step: daily for gas wellAir injection quantity q Annotate i And (5) accumulating and summing to obtain a prediction result of the gas injection quantity of the gas well in the new period.
In actual use, in evaluating gas well productivity, there are three expression of the pressure in formula (6): pressure, pressure square, pseudo pressure. However, the pressure is only suitable for high pressure conditions (pressure greater than 34MPa, temperature greater than 93 ℃); the square pressure is only suitable for low-pressure high-temperature conditions (the pressure is less than 12MPa and the temperature is higher than 93 ℃); only pseudo-pressure is applicable to any pressure, any temperature. Because the pressure change amplitude of the gas storage is larger, the embodiment selects the pseudo pressure for calculation, and is more scientific and reasonable.
The method comprehensively utilizes the outflow equation, the material balance equation and the material balance equation during gas production, realizes quantitative fine prediction of the gas injection and production amount of the gas reservoir, and can predict daily pressure change and the gas injection and production amount of the gas reservoir. The method predicts the utilization of the previous period data to estimate the next period index, has timeliness and improves accuracy.
Embodiment III:
referring to fig. 1-4, a method for evaluating the injection and production capacities of a low-permeability gas reservoir gas well is shown.
The XX gas storage of the low-carburized rock type gas storage is completed by two rounds of injection and production, and a gas injection and production well 3 is built in the gas storage. Before the third gas injection, the average stratum pressure of the gas reservoir is 10.2MPa, the comprehensive material balance equation and the inflow and outflow equation are subjected to iterative calculation, and the gas reservoir is predicted to be capable of injecting 2.46 hundred million parties in the 200-day gas injection period and capable of extracting 1.31 hundred million parties in the 120-day gas extraction period. The period finally has 2.49 hundred million prescription of actual gas injection, 1.30 hundred million prescription of actual gas production, the calculated result is very consistent with the actual production, and the error is less than 2%. (as shown in Table 1)
Table 1 XX analysis table for evaluation results of gas injection and production in second period of gas storage
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Under the condition of no conflict, the technical features related to the examples can be combined with each other according to actual situations by a person skilled in the art so as to achieve corresponding technical effects, and specific details of the combination situations are not described in detail herein.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
While the invention is susceptible of embodiments in accordance with the preferred embodiments, the invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.
Claims (3)
1. A method for evaluating the injection and production capacities of a low-permeability gas reservoir gas well is characterized by comprising the following steps,
step one: obtaining a gas injection inflow equation and a gas injection outflow equation through a gas substance balance equation, a gas inflow equation during gas production and a gas outflow equation during gas production, so as to obtain a gas well yield relation under different formation pressures and a gas well gas injection relation under different formation pressures;
step two: carrying out gas production capacity evaluation;
step three: performing gas injection capability evaluation;
step four: performing operation management on the gas storage according to the evaluation results obtained in the second step and the third step;
the gas well yield relation equation under different formation pressures and the gas well gas injection relation equation under different formation pressures in the first step are obtained as follows:
equation of gas mass balance
（1）
Wherein:
P powder (D) The pressure of the stratum at the end of injection/production is MPa;
P i the formation pressure is the initial injection/production period and is MPa;
Z powder (D) Is the pressure p Powder (D) Natural gas compression factor, dimensionless;
Z i is the pressure p i Natural gas compression factor, dimensionless;
G p to accumulate gas injection/production rate 10 4 m 3 ；
G is gas production period/gas injection period, and the movable storage capacity is evaluated, 10 4 m 3 ；
In the process of gas production, in the formula (1)，G p The accumulated gas production is positive; during gas injection, the formula (1) is +.>，G p For accumulated gas injection, it is negative;
inflow equation (2) during gas production
（2）
（3）
Wherein:
m (p) is the pseudo pressure, MPa 2 /mPa·s；
Pi is the formation pressure in the early stage of gas production and MPa;
P wf the pressure of the stratum at the end of gas production is MPa;
q collecting Is daily gas production, 10 4 m 3 /d；
A is the Darcy flow coefficient;
b is the non-Darcy flow coefficient;
is the viscosity of the gas, mPas;
z is a natural gas deviation coefficient, and is dimensionless;
flow equation during gas production (4)
（4）
Wherein:
P wf is the bottom hole pressure of a gas well, and is MPa;
P tf the pressure is the wellhead pressure of the gas well and MPa;
the intersection point of inflow and outflow curves during gas production is the gas well yield under different stratum pressures, as shown in formula (5):
（5）
a 1 the three-term coefficients of the inflow-outflow intersection curve of the produced gas;
b 1 a binomial coefficient for the inflow-outflow intersection curve of the produced gas;
c 1 a polynomial coefficient for inflow and outflow intersection curves of the produced gas stream;
d 1 a constant term for inflow and outflow intersection curves of the produced gas;
the gas injection and the gas production are the reverse processes, so that the gas injection inflow equation is the gas production outflow equation, namely the equation (4), and at the moment, P wf Greater than P i The method comprises the steps of carrying out a first treatment on the surface of the The gas injection outflow equation also corresponds to the gas intake inflow equation, as shown in (6)
（6）
Wherein: q Pouring Daily gas filling amount of 10 4 m 3 /d；
Similarly, the intersection point of inflow and outflow curves during gas injection is the gas well gas injection amount under different formation pressures, as shown in formula (7):
（7）
a 2 the three-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
b 2 the two-term coefficients of the intersection curve of the inflow and outflow of the gas injection;
c 2 a polynomial coefficient for the inflow and outflow intersection curves of the gas injection;
d 2 the constant term of the intersection curve of inflow and outflow of gas injection.
2. The method for evaluating the gas injection and production capacity of the low-permeability gas reservoir gas well according to claim 1, wherein the method for evaluating the gas production capacity in the second step is as follows:
the first step: substituting the historical gas production data of the previous period into a gas material balance equation to obtain a movable reservoir capacity G in the gas production period of the evaluation gas well;
and a second step of: drawing a dynamic flow-in curve and a dynamic flow-out curve of the produced gas under different formation pressures by using a flow-in equation and a flow-out equation during gas production, wherein the intersection point of the curves is the yield of the gas well under different formation pressures, and thus the relation between the regressive formation pressure and the yield is obtained;
and a third step of: static pressure p of stratum before gas production Initial picking Substituting regression stratum pressure and yield relation, and calculating to obtain gas well first day gas production q 1 st part ；
Fourth step: static pressure p of stratum before gas production Initial picking Movable reservoir capacity G in gas production period and gas production quantity q in first day 1 st part Substituting the pressure into a gas material balance equation, and calculating to obtain the formation pressure p after gas production for one day 1 st part ；
Fifth step: formation pressure p after one day of gas production 1 st part Substitution backThe relation between the formation pressure and the yield is obtained to obtain the gas production quantity q of the gas well on the next day Adopts 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p 1 st part 、G、q Adopts 2 Substituting the gas material balance equation to obtain the formation pressure p of the next day Adopts 2 ；
Sixth step: similarly, the ith gas production q is calculated iteratively by using the gas material balance equation and regressive formation pressure and yield relationship Picking i And ith formation pressure p Picking i ；
Seventh step: daily gas production q for gas well Picking i And (5) accumulating and summing to obtain a prediction result of the gas production of the new period gas well.
3. The method for evaluating the gas injection and production capacity of the low-permeability gas reservoir gas well according to claim 1, wherein the method for evaluating the gas injection and production capacity in the third step is as follows:
the first step: substituting the historical production data of the previous period gas injection into a gas material balance equation, and evaluating the movable reservoir capacity G in the gas injection period of the gas well;
and a second step of: drawing a gas injection inflow dynamic curve and a gas injection outflow dynamic curve under different formation pressures by using a gas injection inflow equation and a gas injection outflow equation, wherein the intersection point of the curves is the gas well gas injection quantity under different formation pressures, and thus a regression formation pressure and gas injection quantity relational expression is obtained;
and a third step of: static pressure p of stratum before gas injection Injecting the primary injection Substituting the relation between the regressive formation pressure and the gas injection quantity to calculate the gas injection quantity q of the gas well on the first day Note 1 ；
Fourth step: static pressure p of stratum before gas injection Injecting the primary injection Movable reservoir capacity G in gas injection period and gas injection quantity q in first day Note 1 Substituting the gas material balance equation, and calculating to obtain formation pressure p after one day of gas injection Note 1 ；
Fifth step: formation pressure p after one day of gas injection Note 1 Substituting the relation between the regressive formation pressure and the gas injection quantity to obtain the gas injection quantity q of the gas well on the next day Note 2 The method comprises the steps of carrying out a first treatment on the surface of the Will p Note 1 、G、q Note 2 Substituting the gas material balance equation to obtain the formation pressure of the next dayp Note 2 ；
Sixth step: similarly, the ith gas injection quantity q is calculated by iteration through the relation between the regressive formation pressure and the gas injection quantity and the gas material balance equation Annotate i And ith formation pressure p Annotate i ；
Seventh step: daily gas injection q for gas well Annotate i And (5) accumulating and summing to obtain a prediction result of the gas injection quantity of the gas well in the new period.
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