CN113445988A - Method for evaluating productivity of gas well of low-permeability carbonate rock gas reservoir - Google Patents
Method for evaluating productivity of gas well of low-permeability carbonate rock gas reservoir Download PDFInfo
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Abstract
The invention provides a method for evaluating the productivity of a gas well of a low-permeability carbonate rock gas reservoir, which comprises the following steps of: selecting a low-permeability carbonate gas reservoir gas well as a target gas well; performing flow cell division on a gas field or a block where the target gas well is located based on a flow cell division method, and determining a flow cell where the target gas well is located; dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage; obtaining production test data for evaluating the productivity of the target gas well at different production stages; and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data. The continuous, quick and accurate evaluation and management of the gas well productivity of the low permeability carbonate gas reservoir can be realized only by the conventional production data of field test without any productivity test in the production period of the gas well, and a basis is provided for the formulation and adjustment of gas well measures and the planning of gas field development schemes.
Description
Technical Field
The invention belongs to the field of oil and gas field development, and particularly relates to a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir.
Background
The productivity management is the core content of gas field development, and is directly related to the establishment and adjustment of gas well operation dynamics, the planning of a gas field development scheme and the evaluation of gas area economic benefits, the key points are that the productivity of the gas well is evaluated, a reasonable working system is determined according to the productivity evaluation result, and the gas well productivity management is timely and accurately carried out, so that the method has important significance in fully exerting the productivity of the gas well and ensuring stable gas supply of the gas area.
The traditional gas well productivity evaluation mainly depends on productivity test, and usually requires closing a well under a plurality of stable working systems to restore the pressure to be stable, and then the test data is used for obtaining a productivity equation to calculate the unimpeded flow to carry out empirical production allocation. In order to reduce the test time, a 'one-point method' productivity test is usually adopted on site, the method only needs to test the stable yield and the corresponding stable flow pressure under one working system, and then the unimpeded flow of the gas well is calculated by combining the empirical productivity coefficient value of the gas area. As gas wells are continuously developed, formation pressure drops and the unobstructed flow rate varies, and the tests need to be repeated at different stages of gas well production to determine current productivity. In summary, existing capacity evaluation methods rely on stable pressure, yield test data.
However, because the low-permeability carbonate gas reservoir gas well is affected by the karst environment, compared with the conventional gas reservoir gas well, the low-permeability carbonate gas reservoir gas well has the characteristics of low reservoir permeability, strong heterogeneity and more development wells, and the characteristics result in low coverage rate and accuracy rate and poor timeliness for evaluating the productivity of the low-permeability carbonate gas reservoir gas well, and the specific reasons are as follows:
(1) the permeability of the reservoir is low, so that the balance time of the productivity test is long, under the conditions of high gas supply demand and large number of developed wells, the economic cost is restricted, and the productivity test of gas wells with about 80% of gas reservoirs can not be carried out in each production stage, so that the timely, comprehensive and accurate evaluation of the gas well productivity is difficult.
(2) The reservoir heterogeneity is strong, so that the physical properties of the reservoir in the transverse direction and the longitudinal direction are discontinuous and the difference is large, the difference is large in the binomial coefficient A value, the binomial coefficient B value, the binomial coefficient alpha value and the like which are obtained by the productivity test of different blocks, and when the binomial coefficient A value, the binomial coefficient B value and the binomial coefficient alpha which are averaged by other blocks of gas wells or gas fields and blocks are directly utilized without depending on the productivity test, the influence on the accuracy of the productivity evaluation is large; in addition, alpha is also influenced by factors such as a pressure system, high-pressure physical deformation and the like, but the value of alpha in the existing one-point method capacity equation basically depends on-site experience or parameter correction such as a reservoir and the like, and the accurate evaluation of capacity is also influenced.
(3) The large number of development wells not only restricts the range and the breadth of the productivity test, but also puts high requirements on the timeliness of the calculation process.
Disclosure of Invention
The invention aims to provide a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir, so as to overcome the technical defects.
In order to solve the technical problems, the invention provides a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir, which comprises the following steps:
selecting a low-permeability carbonate gas reservoir gas well as a target gas well;
performing flow cell division on a gas field or a block where the target gas well is located based on a flow cell division method, and determining a flow cell where the target gas well is located;
dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage;
obtaining production test data for evaluating the productivity of the target gas well at different production stages;
and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data.
Further, dividing different production stages of the target gas well, and acquiring production test data of the target gas well in different production stages, wherein the early development stage refers to a time period from 0 day of development to x days of development, and the daily gas production is greater than 0, and the production test data for evaluating the capacity of the target gas well in the early development stage comprises the following steps:
the average daily gas production for the target gas well x days prior to development, and the wellhead oil pressure for the development day x.
And respectively evaluating the capacity of the target gas well at different production stages according to the flow unit and the production test data, wherein the method for evaluating the capacity at the early development stage comprises the following steps:
step 101, acquiring production data of all gas wells with gas test and production of a flow unit where a target gas well is located, wherein the production data comprises gas test unobstructed flow, average daily gas production of a production gas well x days before the early development stage and wellhead oil pressure of the development x day, and the average daily gas production of the production gas well corresponding to each gas test unobstructed flow;
102, regression is carried out by utilizing a multiple linear equation to obtain the correlation among the unobstructed flow of the test gas, the average daily gas production and the wellhead oil pressure on the development day x, and the following formula is obtained:
in the formula:
qAOFthe gas test unobstructed flow of the gas well which has the gas test and is put into production in the flow unit of the target gas well is 104m3/d；
qgxThe average daily gas production of the gas well which is subjected to gas test and put into production in the previous x days of the early development stage is 104m3/d；
pOil xThe gas well has a gas test in a flow unit where the target gas well is located, and the gas well after production develops wellhead oil pressure of x day in the early development stage, wherein the pressure is MPa;
β1is a constant term, β2～β5Is a regression coefficient;
103, acquiring the average daily gas production rate q of the target gas well x days before the early development stagegxAnd wellhead oil pressure p on day xOil xSubstituting the formula (1) into the formula (1), and calculating the early unobstructed flow of the similar gas testing unobstructed flow of the target gas well;
and 104, establishing a regression curve of the gas test unobstructed flow of all the gas wells with the gas test and the production time of more than n years in the flow unit where the target gas well is located and the average daily gas production of the previous n years of the production gas well corresponding to each gas test unobstructed flow, and determining the production allocation of the target gas well in the early development stage according to the regression curve, wherein n is a positive integer.
Dividing different production stages of a target gas well, and acquiring production test data of the target gas well in the different production stages, wherein the development middle stage refers to a period from development for 31 days to reduction of oil pressure of a wellhead to output pressure of the wellhead, and the production test data for evaluating the production energy of the target gas well in the development middle stage comprise:
the formation pressure, the deviation factor and the gas viscosity of the produced gas well of the flow unit where the target gas well is located, and the bottom hole flow pressure of the target gas well.
And respectively evaluating the capacity of the target gas well at different production stages according to the flow unit and the production test data, wherein the capacity evaluation method at the middle development stage comprises the following steps:
step 201, determining coefficients A and B of a binomial capacity equation of a target gas well in the early development stage;
step 202, establishing a correlation relation regression curve of the product of the gas well stratum pressure-gas viscosity and the deviation factor of the produced gas well in the flowing unit of the target gas well at different testing time, obtaining the current stratum pressure of the target gas well and substituting the current stratum pressure into the correlation relation regression curve to obtain the product of the gas viscosity and the deviation factor of the target gas well under the current stratum pressure;
step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd Bm；
Step 204, obtaining the unobstructed flow of the target gas well under the current formation pressure;
step 205, substituting the unobstructed flow of the target gas well under the current formation pressure into the regression curve established in the step 104 to determine the production allocation of the target gas well in the development middle period;
the current formation pressure at each of the above steps is referred to as the current formation pressure of the target gas well during development.
In step 201, determining the values of the coefficients a and B for developing the early-stage gas well binomial energy production equation is specifically performed according to the following formulas:
in the formula:
pRis the original formation pressure of the target gas well, MPa;
qAOF early stageIs the open flow rate of the target gas well at an early stage of development, 104m3/d；
PwfxThe bottom hole flowing pressure of the target gas well on the x day of the early development is MPa;
qgxis the average daily gas production of the target gas well x days prior to the early stage of development, 104m3/d。
Step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd BmThe method comprises the following steps:
Am＝AZmμgm/Zμg (4)
Bm＝BZmμgm/Zμg (5)
in the formula:
a is the coefficient A value of the developed early gas well binomial productivity equation found according to equation (2) in step 201;
b is the coefficient B value of the developed early gas well binomial productivity equation found according to equation (3) in step 201;
Zμgis the product of the deviation factor of the target gas well at the original formation pressure and the gas viscosity;
Zmμgmis the product of the deviation factor and the gas viscosity for the target gas well at the current formation pressure.
In step 204, the unobstructed flow of the target gas well under the current formation pressure is obtained, which is specifically as follows:
in the formula:
pRmis the current formation pressure of the target gas well;
qmiddle stage of AOFIs a target gas wellCurrent unobstructed flow.
Dividing different production stages of a target gas well, and acquiring production test data of the target gas well in the different production stages, wherein the final development stage refers to a time period that the oil pressure of a wellhead is lower than the output pressure of the wellhead and the gas well is scrapped, and the production test data for evaluating the capacity of the target gas well in the final development stage comprises the following steps:
and the gas testing non-resistance flow or early-stage non-resistance flow of all the produced gas wells under the same flow unit and the final accumulated gas of the produced gas wells corresponding to the gas testing non-resistance flow.
And respectively evaluating the capacity of the target gas well in different production stages according to the flow unit and the production test data, wherein the capacity evaluation method in the later development stage comprises the following steps:
step 301, obtaining the gas testing non-resistance flow or the early non-resistance flow of all produced gas wells under the same flow unit and the final accumulated gas production result of the produced gas wells corresponding to the gas testing non-resistance flow, wherein the gas testing non-resistance flow refers to the non-resistance flow obtained by the gas testing and the early non-resistance flow refers to the early non-resistance flow calculated by using the development early productivity evaluation method when the gas testing is not available;
step 302, establishing a correlation relation regression curve of the final accumulated gas of the production gas wells corresponding to the gas testing non-resistance flow or the early non-resistance flow of all the production gas wells in the step 301 and the gas testing non-resistance flow;
step 303, selecting a yield decreasing stage of the target gas well in the later development stage, and predicting final accumulative gas under different decreasing types by using an Arps decreasing model, wherein the decreasing types comprise exponential decreasing, harmonic decreasing and hyperbolic decreasing;
and 304, substituting the gas test non-resistance flow or the early-stage non-resistance flow of the target gas well into the correlation relation regression curve in the step 302 to obtain the final accumulated gas yield under the corresponding non-resistance flow, wherein the descending type closest to the final accumulated gas yield is determined as the descending type of the target gas well, and guiding the production allocation of the target gas well in the later development stage according to the descending rule corresponding to the descending type.
The invention has the following beneficial effects:
the method for evaluating the productivity of the gas well of the low-permeability carbonate rock gas reservoir can continuously, quickly and accurately evaluate and manage the productivity of the gas well of the low-permeability carbonate rock gas reservoir by using conventional production data of field test without any productivity test in a gas well production period, and provides a basis for gas well measure formulation and adjustment and gas field development scheme planning; particularly, aiming at the situations that the coverage rate and accuracy of capacity evaluation are low and the timeliness is poor due to the low permeability, strong heterogeneity, multiple wells and low-cost development of the current low permeability carbonate gas reservoir, the technical idea of continuously evaluating the capacity in the middle and final stages of development by utilizing the early-stage capacity evaluation result based on flow unit division without capacity test is provided, and meanwhile, the evaluation precision is further improved by continuously restraining and correcting the correlation of various dynamic indexes under the same flow unit.
In order to make the aforementioned and other objects of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
FIG. 1 is a flow chart of a method for evaluating the productivity of a gas well of a hypotonic carbonate gas reservoir.
FIG. 2 is a correlation coefficient R of gas production quantity in early days of development of a production gas well corresponding to gas test non-resistance flow of a low-permeability carbonate gas reservoir gas well and gas test non-resistance flow of each gas test non-resistance flow at different times2The relationship of (1).
Fig. 3 is a regression curve of the correlation between the gas test unobstructed flow rate of the gas well with the flow cell a1 having the gas test and the production time > 3 years and the production rate of the gas well 3 years before the production.
FIG. 4 is a regression plot of gas viscosity versus the product of deviation factors at different formation pressures for a producing well of flow cell A1.
Fig. 5 is a relationship curve of the test gas open flow rate or the final accumulated gas of the producing gas wells corresponding to the development early open flow rate and the test gas open flow rate of all the producing gas wells of the flow unit a 1.
Fig. 6 is a plot of the target gas well a well daily production at the end of development for flow cell a 1.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
In the present invention, the upper, lower, left and right sides of the figure are regarded as the upper, lower, left and right sides of the method for evaluating the productivity of the gas well of the hypotonic carbonate gas reservoir described in the present specification.
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
The first embodiment:
the embodiment relates to a method for evaluating the productivity of a gas well of a hypotonic carbonate gas reservoir, which comprises the following steps of:
selecting a low-permeability carbonate gas reservoir gas well as a target gas well;
performing flow cell division on a gas field or a block where the target gas well is located based on a flow cell division method, and determining a flow cell where the target gas well is located;
dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage;
obtaining production test data for evaluating the productivity of the target gas well in different production stages;
and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data.
In the whole development period of the gas well of the low-permeability carbonate rock gas reservoir, the obtained field conventional production test data comprise original formation pressure, daily gas production, daily water production, wellhead oil pressure and wellhead casing pressure. For a low-permeability carbonate gas reservoir gas well, the low-permeability carbonate gas reservoir gas well is subjected to the constraints of the conditions in various aspects such as long capacity test balance time, high downstream gas supply demand, more wells, cost restriction and the like, so that various capacity tests are lacked in the whole development period, and the evaluation difficulty of each production stage is as follows:
the following evaluation difficulties exist in the early development stage:
and a gas test is lacked, so that the unimpeded flow of the test gas cannot be obtained, and the test production time needs to be shortened as much as possible so as to achieve the reasonable production allocation of the gas well as soon as possible.
Therefore, before evaluating a target gas well, all production data of the gas well with gas test and production under the same flow unit are required to be collected, wherein the production data comprise gas test non-resistance flow, average daily gas production of the production gas well x days before the early development stage and wellhead oil pressure data of the development day x corresponding to each gas test non-resistance flow; and then, a multivariate linear equation is used for regression of the correlation relationship of production data, and then the correlation parameters of the average daily gas yield of x days before the early development of the target gas well and the wellhead oil pressure of the development day x are substituted into the regression mode to calculate the early unimpeded flow of the target gas well similar to the unimpeded flow of the test gas.
The following evaluation difficulties exist in the middle development stage:
the method comprises the steps of firstly, on-site capacity test guidance reasonable production allocation under the condition of lack of current reservoir elastic energy, secondly, calculating the current non-resistance flow by means of the early non-resistance flow of a single well due to lack of single-well non-resistance flow data, and thirdly, in the face of reservoir heterogeneity, selecting an average capacity equation A, B of the whole and block of a gas field or an average value of a one-point method capacity coefficient alpha, or ignoring alpha, wherein the alpha is influenced by factors such as a pressure system and high-pressure physical properties, and the like, and still depending on-site experience or correction of parameters such as the reservoir, so that accurate evaluation of capacity is influenced.
In order to solve the above problems, the embodiment provides a method for calculating the coefficients a and B of the early binomial productivity equation by using the early unimpeded flow, then establishing a fast and reliable correction relationship between the formation pressure, the deviation coefficient and the gas viscosity under the same pressure system by using a small flow unit through flow unit division to simulate a homogeneous gas reservoir, fast calculating the coefficients a and B of the current binomial productivity equation of the gas well under the same flow unit, and finally evaluating the unimpeded flow at the current time.
The following evaluation difficulties exist at the end of development:
the reservoir permeability is low, and the working system, the process measures and the like are frequently changed, so that the yield decreasing curve at the last stage of development has uncertainty on the decreasing type identification, and the reasonable production allocation of the gas well at the current stage is influenced.
In the embodiment, in order to avoid the above problems, a correlation relationship between the test gas non-resistance flow or the early non-resistance flow of all the produced gas wells based on the flow unit and the final accumulated gas of the produced gas wells corresponding to the test gas non-resistance flows is established (the evaluation results of the test gas non-resistance flow and the early non-resistance flow of the same flow unit gas well can be used as sample points, and as the number of the produced gas wells increases, the number of the samples continuously increases, so that the correlation relationship is continuously restrained and corrected), a method of utilizing the test gas non-resistance flow or the early non-resistance flow to restrain and decrease is provided, and a capacity evaluation method without any capacity test data in the full-open period of the gas wells is realized.
The gas wells mentioned above are all gas wells under the same flow cell, and the same method can be adopted for evaluating other flow cells.
According to the embodiment, the capacity test is not needed, and the continuous evaluation of the unimpeded flow in the early and middle stages is realized only by using conventional production data, so that the evaluation accuracy is improved, and the evaluation range is expanded.
Second embodiment:
the embodiment relates to a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir, which comprises the following steps:
selecting a low-permeability carbonate gas reservoir gas well as a target gas well;
performing flow cell division on a gas field or a block where the target gas well is located based on a flow cell division method, and determining a flow cell where the target gas well is located;
dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage;
the method comprises the following steps of dividing different production stages of a target gas well, specifically according to the following method:
in the early stage of development: developing for 0-x days, and the daily gas production is more than 0;
in the middle stage of development: developing a time period from x +1 day to the time period that the oil pressure of the wellhead is reduced to the output pressure of the wellhead;
at the end of development: and the oil pressure is lower than the wellhead output pressure until the gas well is abandoned.
Obtaining production test data for evaluating the productivity of the target gas well in different production stages;
and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data.
The early division and production characteristics related to development:
according to the production characteristics of a gas well of a hypotonic carbonate gas reservoir, 0 month to x days (excluding days with daily gas production of 0 value) are defined as the early development stage of the gas well, and the early stage is divided according to the following steps:
the determination of the development early time node is guided by mathematically regressing the correlation relationship (the calculation result is shown in table 1) between the gas test non-resistance flow (which means that two conditions of gas test and production are provided) of the gas test non-resistance flow of the low-permeability carbonate gas reservoir gas well at different production times and the daily gas yield of the production gas well at the early development stage (10d, 30d, 90d and 330d) corresponding to the gas test non-resistance flow. The trend of the correlation relationship under different production times shows that the longer the production time of the gas well is, the better the production stability of the gas well is, namely, the correlation relationship coefficient R of the regression curves of the gas test unobstructed flow and the early daily gas production rate2The better, but at the same time, the presence of a phase 30d was also found early in developmentThe point of inflection of the coefficient of relevance (fig. 2). By combining the requirements of making reasonable early production allocation and exerting gas well production capacity as soon as possible on site, not consuming excessive reservoir energy and obtaining higher economic benefit, and comprehensively considering the factors of evaluation time and better correlation, the evaluation criterion for determining the early production capacity in the embodiment is the early 30d yield (in the embodiment, R after 30d is obtained)2Both greater than 0.8), i.e., x ═ 30.
Other hypotonic carbonate reservoir applications may use smaller intervals (e.g., 10d, 20d, 30d, 40d, 50d, etc.) at different early time periods, and then combine the respective gas fields, time of inflection point occurrence in the block, downstream gas supply requirements, and economic efficiency to select comprehensively. If the gas field of the target gas well does not have relevant data, refer to the early division time 30d in this example.
The daily gas production of 10d, 30d, 90d and 330d refers to the average daily gas production in the period of time, which does not contain zero daily gas production.
The hypotonic carbonate gas reservoir gas well refers to a gas well with an effective permeability of between 0.1 and 10 mD.
Table 1 correlation table of gas test non-resistance flow of low permeability carbonate gas reservoir gas well and gas production rate of production gas well corresponding to each gas test non-resistance flow at different early stages
| Early time (d) | Correlation relationships | Coefficient of correlation R2 |
| 10 | Y＝0.2097X+0.3679 | 0.7254 |
| 30 | Y＝0.23X+0.3147 | 0.8198 |
| 90 | Y＝0.27X+0.3 | 0.8615 |
| 330 | Y＝0.3246X-0.1 | 0.8892 |
The abscissa of fig. 2 is the different production times in the early stage of development (i.e., 30d corresponding to the average daily gas production within 30d in the early stage of development), and the ordinate is the correlation coefficient R of the daily gas production in the early stage of development of the gas well of the low permeability carbonate gas reservoir with the gas test open flow rate corresponding to each gas test open flow rate2FIG. 2 shows the correlation coefficient R at 30d2R after 30d at the inflection point2Relatively close meaning.
It should be noted that the production test data for evaluating the capacity of the target gas well in the early development stage at least includes:
the average daily gas production of the target gas well x days before development and the wellhead oil pressure corresponding to the x day of the daily gas production.
The division basis and production characteristics in the middle of development:
the time from the day of development x +1 (31 d in the example) to the time when the oil pressure at the wellhead is reduced to the output pressure of the system is the middle stage of gas well development, because the reservoir still has a certain elastic capacity space in the time period from the day of development x +1 to the time when the oil pressure at the wellhead is reduced to the output pressure of the system, the stable production of the reservoir can be transited from the last stage to a new stable production stage under the condition of reduced elastic capacity of the reservoir (for example, the characteristic of 'step-shaped' stable production is presented).
Notably, production test data for evaluating the production capacity of the target gas well in the development period needs to be acquired, and the production test data at least comprises the following components:
the formation pressure, the deviation factor and the gas viscosity of the produced gas well of the flow unit where the target gas well is located, and the bottom hole flow pressure of the target gas well.
The division basis and production characteristics at the end of development:
the reason why the time period from the wellhead oil pressure being lower than the wellhead output pressure to the abandonment of the gas well is the last stage of gas well development is that the yield is decreased after the wellhead pressure of the gas well is lower than the system pressure, and the difference between the characteristic stage of the yield and the previous stage is obvious.
In particular, production test data for evaluating the capacity of the target gas well at the end of development is acquired, and the production test data at least comprises the following components:
and the gas testing non-resistance flow or early-stage non-resistance flow of all the produced gas wells under the same flow unit and the final accumulated gas of the produced gas wells corresponding to the gas testing non-resistance flow.
The third embodiment:
the embodiment relates to a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir, which comprises the following steps:
selecting a low-permeability carbonate gas reservoir gas well as a target gas well;
performing flow unit division on a gas field or a block where a target gas well is located based on a flow unit division method;
dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage;
the method comprises the following steps of dividing different production stages of a target gas well, specifically according to the following method:
in the early stage of development: developing for 0-x days, and the daily gas production is more than 0;
in the middle stage of development: developing a time period from x +1 day to the time period that the oil pressure of the wellhead is reduced to the output pressure of the wellhead;
at the end of development: and the oil pressure of the well head is lower than the output pressure of the well head until the time period that the gas well is scrapped.
Obtaining production test data for evaluating the productivity of the target gas well at different production stages;
and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data, wherein the productivity evaluation is as follows:
the method for evaluating the capacity in the early development stage comprises the following steps:
step 101, acquiring production data of all gas wells with gas test and production of a flow unit where a target gas well is located, wherein the production data comprises gas test unobstructed flow, average daily gas production of a production gas well x days before the early development stage and wellhead oil pressure of the development x day, and the average daily gas production of the production gas well corresponding to each gas test unobstructed flow;
102, regression is carried out by utilizing a multiple linear equation to obtain the correlation among the unobstructed flow of the test gas, the average daily gas production and the wellhead oil pressure on the development day x, and the following formula is obtained:
in the formula:
qAOFthe gas test unobstructed flow of the gas well which has the gas test and is put into production in the flow unit of the target gas well is 104m3/d；
qgxThe average daily gas production of the gas well which is subjected to gas test and put into production in the previous x days of the early development stage is 104m3/d；
pOil xThe gas well has a gas test in a flow unit where the target gas well is located, and the gas well after production develops wellhead oil pressure of x day in the early development stage, wherein the pressure is MPa;
β1is a constant term, β2～β5Is a regression coefficient;
since the target gas well is a new production gas well, and the purpose of the early development stage is to predict the early non-resistance flow of the new production gas well, after the average daily gas yield of the production gas wells with the gas test non-resistance flow and corresponding to the gas test non-resistance flow of all the production gas wells with the gas test in the flow unit where the target gas well is located on the early development stage and the regression curve of the wellhead oil pressure on the x-th day are developed, namely the formula (1), the next step needs to be executed.
103, acquiring the average daily gas production rate q of the target gas well x days before the early development stagegxAnd day x wellhead oil pressure pOil xSubstituting the formula (1) into the formula (1), and calculating the early unobstructed flow of the similar gas testing unobstructed flow of the target gas well;
the wellhead oil pressure corresponding to the production date of the average daily gas production rate on the x day refers to the average pressure of continuous differential pressure less than or equal to 0.1 for 5 days before and after the day, and can be shortened to 3 days if the pressure is not consistent within 5 days.
And 104, establishing a regression curve of the gas test unobstructed flow of all the gas wells with the gas test and the production time of more than n years in the flow unit where the target gas well is located and the average daily gas production of the previous n years of the production gas well corresponding to each gas test unobstructed flow, and determining the production allocation of the target gas well in the early development stage according to the regression curve, wherein n is a positive integer.
Dividing different production stages of a target gas well, and acquiring production test data of the target gas well in the different production stages, wherein the development middle stage refers to a development period from x +1 day to a period from the reduction of wellhead oil pressure to wellhead output pressure, and the production test data for evaluating the production energy of the target gas well in the development middle stage comprise:
the formation pressure, the deviation factor and the gas viscosity of the produced gas well of the flow unit where the target gas well is located, and the bottom hole flow pressure of the target gas well.
And respectively evaluating the capacity of the target gas well at different production stages according to the flow unit and the production test data, wherein the capacity evaluation method at the middle development stage comprises the following steps:
step 201, determining coefficients A and B of a binomial capacity equation of a target gas well in the early development stage;
step 202, establishing a correlation relation regression curve of the product of the gas well stratum pressure-gas viscosity and the deviation factor of the produced gas well in the flowing unit of the target gas well at different testing time, obtaining the current stratum pressure of the target gas well and substituting the current stratum pressure into the correlation relation regression curve to obtain the product of the gas viscosity and the deviation factor of the target gas well under the current stratum pressure;
step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd Bm；
Step 204, obtaining the unobstructed flow of the target gas well under the current formation pressure;
step 205, substituting the unobstructed flow of the target gas well under the current formation pressure into the regression curve established in the step 104 to determine the production allocation of the target gas well in the development middle period;
the current formation pressure at each of the above steps is referred to as the current formation pressure of the target gas well during development.
In step 201, determining the values of the coefficients a and B for developing the early-stage gas well binomial energy production equation is specifically performed according to the following formulas:
in the formula:
pRis the original formation pressure of the target gas well, MPa;
qAOF early stageIs the open flow of the target gas well early in development, 104m3/d；
PwfxThe bottom hole flowing pressure of the target gas well on the x day of the early development is MPa;
qgxis the average daily gas production of the target gas well x days prior to the early stage of development, 104m3/d。
Step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd BmThe method comprises the following steps:
Am＝AZmμgm/Zμg (4)
Bm＝BZmμgm/Zμg (5)
in the formula:
a is the coefficient A value of the developed early gas well binomial productivity equation found according to equation (2) in step 201;
b is the coefficient B value of the developed early gas well binomial productivity equation found according to equation (3) in step 201;
Zμgis the product of the deviation factor of the target gas well at the original formation pressure and the gas viscosity;
Zmμgmis the product of the deviation factor and the gas viscosity for the target gas well at the current formation pressure.
In step 204, the unobstructed flow of the target gas well under the current formation pressure is obtained, which is specifically as follows:
in the formula:
pRmis the current formation pressure of the target gas well;
qmiddle stage of AOFIs the current unobstructed flow rate of the target gas well.
Dividing different production stages of a target gas well, and acquiring production test data of the target gas well in the different production stages, wherein the final development stage refers to a time period that the oil pressure of a wellhead is lower than the output pressure of the wellhead and the gas well is scrapped, and the production test data for evaluating the capacity of the target gas well in the final development stage comprises the following steps:
and the gas testing non-resistance flow or early-stage non-resistance flow of all the produced gas wells under the same flow unit and the final accumulated gas of the produced gas wells corresponding to the gas testing non-resistance flow.
And respectively evaluating the capacity of the target gas well in different production stages according to the flow unit and the production test data, wherein the capacity evaluation method in the later development stage comprises the following steps:
step 301, obtaining the gas testing non-resistance flow or the early non-resistance flow of all produced gas wells under the same flow unit and the final accumulated gas production result of the produced gas wells corresponding to the gas testing non-resistance flow, wherein the gas testing non-resistance flow refers to the non-resistance flow obtained by the gas testing and the early non-resistance flow refers to the early non-resistance flow calculated by using the development early productivity evaluation method when the gas testing is not available;
step 302, establishing a correlation relation regression curve of the final accumulated gas of the production gas wells corresponding to the gas testing non-resistance flow or the early non-resistance flow of all the production gas wells in the step 301 and the gas testing non-resistance flow;
step 303, selecting a yield decreasing stage of the target gas well in the later development stage, and predicting final accumulative gas under different decreasing types by using an Arps decreasing model, wherein the decreasing types comprise exponential decreasing, harmonic decreasing and hyperbolic decreasing;
and 304, substituting the gas test non-resistance flow or the early-stage non-resistance flow of the target gas well into the correlation relation regression curve in the step 302 to obtain the final accumulated gas yield under the corresponding non-resistance flow, wherein the descending type closest to the final accumulated gas yield is determined as the descending type of the target gas well, and guiding the production allocation of the target gas well in the later development stage according to the descending rule corresponding to the descending type.
Fourth embodiment:
the embodiment relates to a method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir, which comprises the following steps:
selecting a gas well A of a gas field of a hypotonic carbonate gas reservoir M as a target gas well, wherein the gas well is put into production in 5-month-12-day 2001, and has no test gas, no test gas and no resistance flow;
carrying out flow cell division on an M gas field where a target gas well is located based on a flow cell division method, dividing 36 flow cells in total, and determining that the flow cell where the target gas well is located is A1;
dividing different production stages of the target gas well A, including an early development stage, a middle development stage and a final development stage;
the method comprises the following steps of dividing different production stages of a target gas well, specifically according to the following method:
in the early stage of development: the development time ranges from 0 day to 30 days (6 months and 11 days in 2001), the daily gas production is more than 0, and the 30-day determination method is shown as the development early division basis, namely x is 30;
in the middle stage of development: developing a period from 31 days (6 months and 12 days in 2001) to the time when the wellhead oil pressure is reduced to the wellhead output pressure (6 months and 20 days in 2015);
at the end of development: and the oil pressure of the well head is lower than the output pressure of the well head until the time period of gas well abandonment (the gas well abandonment comes from 6-21 months in 2015).
In the early stage of development: the gas test non-resistance flow of all gas wells which have gas test and are put into production and are located in the flow unit A1 of the target gas well A, the average daily gas production of the put-into-production gas wells corresponding to the gas test non-resistance flow in the first 30 days of the early development and the wellhead oil pressure in the 30 th day of the development (the data are utilized to establish the correlation relationship of the three data); the average daily gas production rate in the early 30 days of the target gas well development and the wellhead oil pressure corresponding to the early 30 days (the early unobstructed flow is calculated by substituting the indexes into the former relation).
In the middle stage of development: the deviation factor and the gas viscosity tested under different lamination pressure conditions of the flow unit where the target gas well is located (the relationship among the three in the flow unit is established by using the data, and the yield equation coefficient A, B value of the same flow unit can be corrected quickly); the original formation pressure of the target gas well, the current formation pressure, and the bottom hole flow pressure early in development (the A, B value at the previous stage of computation).
At the end of development: and the gas testing non-resistance flow or early-stage non-resistance flow of all the produced gas wells in the flow unit of the target gas well and the final accumulated gas of the produced gas wells corresponding to the gas testing non-resistance flow.
And respectively evaluating the productivity of different production stages of the target gas well according to the flow unit division result and the production test data, which comprises the following steps:
the method for evaluating the capacity in the early development stage comprises the following steps:
step 101, acquiring all production data of gas wells with gas test and production of a flow unit A1 where a target gas well A is located, wherein the production data comprises gas test non-resistance flow, average daily gas production of a production gas well 30 days before the early development period and wellhead oil pressure of the development 30 th day, and the production data corresponds to each gas test non-resistance flow;
102, by utilizing a multivariate linear equation to regress the correlation among the unobstructed flow of the test gas, the average daily gas production and the wellhead oil pressure on the development day 30, obtaining the following formula:
in the formula:
qAOFthe gas test unobstructed flow of the gas well which has the gas test and is put into production in the flow unit of the target gas well is 104m3/d；
qgxThe average daily gas production of the gas well which is subjected to gas test and is put into production in the flowing unit of the target gas well 30 days before the early development stage is 104m3/d；
pOil xThe gas well has a gas test in a flow unit where the target gas well is located, and the well mouth oil pressure of the gas well after production is developed in the early development stage at day 30, namely MPa;
since the target gas well a does not have the test gas data, the next step is performed.
Step 103, obtaining the average daily gas production rate q of the target gas well A30 days before the early development stageg30And wellhead oil pressure p at day 30OilWherein q isg30Is 30.0X 104m3/d，pOil24.8MPa, and the early unobstructed flow of the target gas well can be calculated and obtained by substituting the formula (1) into the formula (165.3 multiplied by 10)4m3/d；
It should be noted that the 30d wellhead oil pressure corresponds to the last day of the production date of the average daily gas production, and the continuous pressure difference of 5 days before and after the day is required to be less than or equal to 0.1, and can be shortened to 3 days if the pressure difference is not met within 5 days.
And 104, establishing a regression curve of the gas test unobstructed flow of all the gas wells with the gas test and the production time of more than n years of the flow unit A1 and the average daily gas production of the previous n years of the produced gas wells corresponding to the gas test unobstructed flow, and determining the production allocation of the target gas well in the early development stage according to the regression curve, wherein n is a positive integer.
In the embodiment, the practical condition of the development of the M gas field is referred to (not only the downstream gas supply requirement and certain economic benefit of the M gas field are met, but also the likeThe gas field can also refer to the constraint condition), n is 3, the daily gas production of the target gas well A, namely the reasonable production allocation in the first three years is 30.2 multiplied by 10, through the regression flow unit A1, the gas test unobstructed flow rate of all gas wells with the gas test unobstructed flow rate and the operation time of more than 3 years and the regression curve (figure 3) of the correlation relationship between the daily gas production of the previous 3 years of the operation gas wells corresponding to the gas test unobstructed flow rate4m3D (as can be seen from the relation regressed in fig. 3, the early clear flow rate was evaluated as 165.3 × 0.1648+2.9534, which is 30.2), and the whole was 30.0 × 104m3/d。
In fig. 3, the abscissa represents the gas test non-resistance flow rate of all gas wells with gas test and production time > 3 years of the flow cell a1, and the ordinate represents the average daily gas production rate of the previous 3 years of the production gas wells corresponding to each gas test non-resistance flow rate. When the non-resistance flow of the target gas well is known, the daily gas production level of 3 years can be quickly calculated by using the chart, for example, the early calculated non-resistance flow of the A well is 165.3 multiplied by 104m3D, then the daily yield corresponding to 3 years is 165.3 multiplied by 0.1648+2.9534 is 30.2 multiplied by 104m3/d。
Compared with the conventional productivity test mode, the evaluation method in the early development stage has the following characteristics:
the method is an early productivity evaluation based on the flow cell constraint condition, the constraint condition mainly aims at the characteristic of strong heterogeneity of a reservoir, large reservoir difference on a plane is divided into a plurality of small flow cells, and the flow cells can be further simplified into a homogeneous gas reservoir due to similar medium temperature and pressure, fluid and physical properties. By the method, the accuracy of the empirical formula is guaranteed, the calculation efficiency is improved, and the method has the advantages that: the idea that the traditional evaluation mainly utilizes a simplified capacity test 'one-point method' is avoided, and the experience value of the 'one-point method' capacity equation usually takes the same value according to the previous test data of a gas field, so that the accurate calculation of the unimpeded flow is directly influenced particularly for the hypotonic carbonate gas reservoir with strong reservoir heterogeneity; in addition, alpha changes greatly under different pressure system conditions, but the alpha value in the existing one-point method capacity equation basically depends on-site experience or experience correction, and the accurate evaluation of capacity is also influenced; partial improvement of the 'one-point method' can be realized by using the 'one-point method' productivity equation empirical values of all well testing data of a gas field or a block to evaluate different formation coefficients or carrying out empirical correction according to reservoir dynamic and static characteristic analogy, but the evaluation of the unimpeded flow is not accurate enough because high-pressure physical properties are ignored.
Different from the traditional method, in the embodiment, by establishing the correlation between the average daily gas yield of the commissioning gas well, which corresponds to the gas test non-resistance flow rate and the gas test non-resistance flow rate of all the gas wells with gas test and commissioning under the same flow unit, in the first 30 days of the development and the wellhead oil pressure in the 30 th day of the development, and by strictly dividing the early time of the target gas well and strictly checking the early data (the constraint of the calculation parameters in the empirical formula and the calculation method), the early non-resistance flow rate can be quickly and accurately evaluated only by using the on-site conventional test data, and the early rational production allocation of the gas well can be guided.
The capacity evaluation method in the middle development period comprises the following steps:
step 201, determining a coefficient value A and a coefficient value B of an early binomial productivity equation of the target gas well A according to the following formulas:
in the formula:
pRis the original formation pressure, MPa, of the target gas well a;
qAOF early stageIs the open flow of the target gas well a early in the development, 104m3/d；
Pwf30Is the target gas well a at day 30 (corresponding to q) early in developmentg30End date) bottom hole flow pressure, MPa;
qg30is the average daily gas production of the target gas well A30 days prior to the early stage of development, 104m3/d；
Step 202, establishing a correlation relationship regression curve (see fig. 4) of the product of the gas well formation pressure-gas viscosity and the deviation factor of the produced gas well under different test time by the flow unit A1, obtaining the current formation pressure of the target gas well A and substituting the current formation pressure into the correlation relationship regression curve to obtain the product of the gas viscosity and the deviation factor of the target gas well under the current formation pressure;
the abscissa of fig. 4 is the formation pressure and the ordinate is the gas viscosity x deviation factor, such as the current formation pressure of 22MPa, then the product of 0.0002x 22-0.0036 x 22+0.1509 is 0.1685 mp.s.
Step 203, correcting the coefficient A value and the coefficient B value of the initial gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected coefficient A value and the corrected value B are AmAnd BmThe method comprises the following steps:
Am＝AZmμgm/Zμg (4)
Bm＝BZmμgm/Zμg (5)
in the formula:
a is the coefficient A value of the developed early gas well binomial productivity equation found according to equation (2) in step 201;
b is the coefficient B value of the developed early gas well binomial productivity equation found according to equation (3) in step 201;
Zμgis the product of the deviation factor of the target gas well a at the original formation pressure and the gas viscosity;
Zmμgmis the product of the deviation factor of the target gas well a at the current formation pressure and the gas viscosity;
step 204, developing a calculation formula for evaluating the unimpeded flow of the gas well in the middle period as follows:
in the formula:
pRmis the current formation pressure of the target gas well a;
qmiddle stage of AOFIs the order of eyesCurrent unobstructed flow for standard gas well a
Step 205, calculating the unobstructed flow of the target gas well under the current formation pressure by the formula (6) in the step 204;
step 206, substituting the unobstructed flow of the target gas well A under the current formation pressure into the regression curve established in the step 104 to determine the production allocation of the target gas well in the development middle period;
the current formation pressure at each of the above steps is referred to as the current formation pressure of the target gas well during development.
Taking the target gas well A of the flow cell A1 as an example, the original formation pressure of the well is known to be 31.0MPa, and the daily gas production of the early 30 days of development is known to be 30.0 multiplied by 104m3D, early clear flow evaluated 165.3X 104m3And d (no choke flow evaluation is shown in the early development stage), the early bottom hole flow pressure is 29.5MPa, and the early productivity binomial equation A, B values can be determined to be 2.40 and 0.02 respectively by using the equation (2) and the equation (3) in the step 201.
With the production of the gas well, the elastic energy of the stratum is continuously reduced, the unimpeded flow is reduced, and the reasonable production allocation needs to be reevaluated and formulated. Considering that the reservoir physical property of the flow cell A1 where the target gas well A is located is good, the early-stage non-resistance flow rate and the early-stage production allocation are high, the non-resistance flow rate evaluation and the reasonable production allocation are made by combining the production stability condition of the gas well on site, and the detailed evaluation result is shown in Table 2. Taking an example of evaluating the non-resistance flow rate and making a corresponding reasonable production allocation in 5/3/2004, at the date, it is known that the product of the gas deviation factor and the viscosity under the original formation pressure is 0.23 (the value is a test result, a chart of fig. 4 is not used, if the test result is selected, if the original test condition is not met, the relation between the formation pressure of the flow unit and the product of the deviation factor and the viscosity can be referred to), and at the current date, the formation pressure is 22.0MPa, and the relation between the formation pressure of fig. 4 and the deviation factor and the viscosity correlation of the gas field can be referred to (Y is 0.0002X2-0.0036X +0.1509) calculates a corrected deviation factor multiplied by viscosity of 0.17; in combination with the value of the early calculated productivity binomial A, B, the corrected productivity binomial A, B values can be calculated to be 1.77 and 0.02 respectively by using the equations (4) and (5) in the step 203; finally substituting into step 204 formula (6) can calculate the unobstructed flow rate of 129.4 multiplied by 10 under the current formation pressure of 22.0MPa4m3And d, further determining the daily gas yield of the target gas well A, namely the current reasonable production allocation is 24.3 multiplied by 10 according to the regression curve (figure 3) of the gas test unobstructed flow of all the gas wells with the gas test and the production time of more than 3 years of the flow unit A1 and the average daily gas yield of the previous 3 years of the gas wells corresponding to the gas test unobstructed flow of each gas test unobstructed flow4m3D, rounding to 24.0X 104m3And/d, the calculation process is similar at the rest time. The changed gas well formation pressure can be obtained by pressure test, wellbore pressure gradient, vertical pipe flow formula and the like.
Table 2 table of calculation results of medium-term unobstructed flow and production allocation of target gas well a of flow cell a1
Compared with the conventional capacity test mode, the evaluation method in the middle development period has the following characteristics:
the method has the advantages that the unimpeded flow calculation in the middle development period based on the flow unit is established, the influence of temperature and fluid on the viscosity and deviation factors (high-pressure physical properties) can be ignored through the constraint of the flow unit, on one hand, the reliability of the correlation relation between the formation pressure and the viscosity and the deviation factors is improved, on the other hand, the large amount of and complicated calculation workload of chart fitting or repeated iteration in the process of obtaining the common viscosity and deviation factors is reduced, the method has the characteristics of simplicity, convenience, rapidness and accuracy, and is particularly suitable for the situations of large number of wells and large evaluation workload of low permeability carbonate gas reservoir gas wells.
Secondly, a medium-term unobstructed flow calculation method based on an early-term unobstructed flow evaluation result is established, continuous evaluation of the early-term unobstructed flow and the medium-term unobstructed flow of the same flow unit under a test-free condition is realized, the problems that a yield equation binomial A, B value is required to produce data such as a production well test, a correction isochronous well test, a point method well test and the like are solved, the capacity evaluation range of the low-permeability carbonate gas reservoir gas well in the medium-term development is effectively expanded, and the evaluation timeliness is improved.
The capacity evaluation method at the final stage of development is as follows:
step 301, obtaining the gas testing non-resistance flow or the early non-resistance flow of all produced gas wells under the same flow unit and the final accumulated gas production result of the produced gas wells corresponding to the gas testing non-resistance flow, wherein the gas testing non-resistance flow refers to the non-resistance flow obtained by the gas testing and the early non-resistance flow refers to the early non-resistance flow calculated by using the development early productivity evaluation method when the gas testing is not available;
step 302, establishing a correlation relation regression curve (shown in figure 5) of the final accumulated gas of the production gas wells corresponding to the test gas non-resistance flow or the early stage non-resistance flow of all the production gas wells in the step 301;
FIG. 5 is a graphical representation of the relationship between the early/no-block flow rate for all produced wells for flow cell A1 and the resulting accumulated gas for the producing wells corresponding to each no-block flow rate for example, knowing that the early stage is 165.3X 104m3D, final accumulative gas 165.3 × 0.0249 × 165.3+5.09 ═ 9.2 × 108m3/d。
Step 303, selecting a yield decreasing stage of the target gas well in the later development stage, and predicting final accumulative gas under different decreasing types by using an Arps decreasing model, wherein the decreasing types comprise exponential decreasing, harmonic decreasing and hyperbolic decreasing;
and 304, substituting the test gas unobstructed flow or early unobstructed flow of the target gas well into the correlation relation regression curve (figure 5) of 302 to obtain the final gas production rate corresponding to the unobstructed flow, wherein the descending type closest to the final gas production rate is determined as the descending type of the target gas well, and guiding the production allocation of the target gas well in the later development stage according to the descending rule corresponding to the descending type.
Still taking the flow cell a1 target gas well a as an example, the well enters the later development stage after 21 days 6 months 2015 (the production curve is shown in fig. 6), after the yield is decreased, the yield decreasing section is selected for Arps decreasing analysis, and the final accumulated gas under different decreasing types (index, hyperbolic, harmonious) is predicted, and the result is shown in table 3. Using step 304, the target gas well A is evaluated earlyUnimpeded flow 165.3 x 104m3Substituting/d into the regression relation in FIG. 5 to obtain the final accumulated gas yield of 9.2 × 10 corresponding to the initial unobstructed flow8m3The descending type closest to the initial unobstructed flow is exponential descending, the descending type is determined as the descending type of the target gas well, the reasonable production allocation of different stages is evaluated according to the descending rule, and the current production allocation of the target gas well A is 5.5 multiplied by 104m3/d。
FIG. 6 is a plot of data from a target gas well at the end of development for evaluation of the drawdown.
Table 3 final gas production results table using different decreasing types for evaluation of target gas well a at late stage of development of flow cell a1
| Decreasing type | Predicting the ultimate gas build-up (10)8m3) |
| Index of refraction | 9.3 |
| Double curve | 10.1 |
| Blending | 11.3 |
Compared with the conventional productivity test mode, the evaluation method in the later development stage has the following characteristics:
the later-stage descending evaluation method based on the gas-testing non-resistance flow and the early-stage non-resistance flow evaluation results is established, the continuous evaluation of the early-stage non-resistance flow, the middle-stage non-resistance flow and the final-stage reasonable production allocation is realized under the condition that the same flow unit does not need to be tested, and the seamless connection of the productivity evaluation in the whole production cycle of the gas well is realized. And secondly, the gas is finally accumulated by introducing index constraints representing the initial capacity of the gas well such as the gas testing unobstructed flow and the early unobstructed flow evaluation result, so that the uncertainty of the judgment of the descending evaluation type is solved. Meanwhile, the open flow calculated in the early development stage is added into the open flow under the same flow unit and the gas production chart is accumulated finally, so that the sample points of data are effectively increased, the accuracy of the chart is continuously corrected, and the evaluation precision is improved.
And the produced gas well and the target gas well in the steps are gas wells under the same flow unit.
After the evaluation in the final development stage is finished, the capacity of the low-permeability carbonate reservoir can be managed, and the method specifically comprises the following steps:
at any stage of gas well development, as long as the productivity evaluation result and reasonable production allocation are obtained, the production can be managed according to the low permeability carbonate gas reservoir gas well productivity management method.
And (3) integrating and classifying the low-permeability carbonate gas reservoir gas wells according to the production characteristics (the conditions of wellhead oil pressure, reasonable production allocation and water production of the current gas wells) of the gas wells with different flow units and formulating corresponding management measures, wherein specific pressure and yield classification standards mainly refer to block mining modes and the existing production experience.
Based on the production experience of a hypotonic carbonate salt gas reservoir M gas field, the system pressure is 6.4MPa, the pressure release capacity is 10MPa (the wellhead pressure is greater than the system pressure by about 3.5-4.5 MPa), and the yield of a gas well is greater than 4 multiplied by 104m3Dividing the gas area into high-yield wells, wherein the average stable gas yield of the gas area is more than or equal to 3 years, and the peak shaving wells are mainly preferred in the gas wells for supplying gas for winter peaks;
will have a certain pressure release capacity of 8-10 MPa, 2-4X 104m3Dividing the well into middle and high producing wells (the well head pressure is lower than the high producing well pressure range within 2 MPa-the high producing well pressure range, the gas well yield is 1/2, and the stable gas yield in 3 years before the average gas area to the stable gas yield in 3 years before the average gas area), and keeping the current gas yield production in the production of the well;
will release pressureThe capacity is limited to 6.4-8 MPa (the pressure of a wellhead pressure system is low-value of the pressure of a medium-yield well), and the yield of a gas well is 0.5 multiplied by 104m3D, dividing the low value of the medium-high producing well into medium producing wells, and closely paying attention to the water production early warning and the timely intervention of water drainage and gas production measures in the management of the part of wells;
will be lower than the system pressure (wellhead pressure)<6.4MPa), gas well production less than 0.5 x 104m3And d, dividing the well into low-yield wells, and needing to develop low-yield and low-efficiency well treatment.
Based on the production experience of M gas field of hypotonic carbonate salt gas reservoir, the system pressure is 6.4MPa, 169 gas wells in a certain block, which are related to 4 flow units, are classified, and the gas well has pressure release capacity (well head pressure)>10MPa), gas well production greater than 4X 104m3Dividing the gas well into high-producing wells, wherein 9 high-producing wells are provided in total, and the peak shaving wells are mainly preferred in the part of gas wells for supplying gas for winter peaks; the gas well has a certain pressure relief capacity (the pressure of a well head is 8-10 MPa), and the yield of the gas well is 2-4 multiplied by 104m3Dividing the well into middle and high yield wells, wherein the total number of the wells is 27, and the wells keep the current gas production rate on production; the pressure release capacity is limited (the pressure at the well head is 6.4 to 8MPa), and the yield of the gas well is 0.5 to 2 multiplied by 104m3Dividing the well into medium producing wells with 76 ports in total, and closely paying attention to the water production early warning and timely intervention of drainage and gas production measures in the management of the part of wells; will be lower than the system pressure (wellhead pressure)<6.4MPa), gas well production less than 0.5 x 104m3And d, dividing the low-yield well into 57 wells in total, and performing low-yield and low-efficiency well treatment, wherein specific measures are shown in a table 3.
TABLE 3M gas field low-yield well dynamic and static characteristics and treatment measures
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.
Claims (10)
1. A method for evaluating the productivity of a gas well of a low-permeability carbonate gas reservoir is characterized by comprising the following steps of,
the method comprises the following steps:
selecting a low-permeability carbonate gas reservoir gas well as a target gas well;
performing flow cell division on a gas field or a block where the target gas well is located based on a flow cell division method, and determining a flow cell where the target gas well is located;
dividing different production stages of the target gas well, including early development stage, middle development stage and final development stage;
obtaining production test data for evaluating the productivity of the target gas well at different production stages;
and respectively evaluating the productivity of the target gas well at different production stages according to the flow unit and the production test data.
2. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 1,
dividing different production stages of the target gas well, and acquiring production test data of the target gas well in different production stages, wherein the early development stage refers to a time period from 0 day of development to x days of development, and the daily gas production is greater than 0, and the production test data for evaluating the capacity of the target gas well in the early development stage comprises the following steps:
the average daily gas production for the target gas well x days prior to development, and the wellhead oil pressure for the development day x.
3. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 2,
and respectively evaluating the capacity of the target gas well at different production stages according to the flow unit and the production test data, wherein the method for evaluating the capacity at the early development stage comprises the following steps:
step 101, acquiring production data of all gas wells with gas test and production of a flow unit where a target gas well is located, wherein the production data comprises gas test unobstructed flow, average daily gas production of a production gas well x days before the early development stage and wellhead oil pressure of the development x day, and the average daily gas production of the production gas well corresponding to each gas test unobstructed flow;
102, regression is carried out by utilizing a multiple linear equation to obtain the correlation among the unobstructed flow of the test gas, the average daily gas production and the wellhead oil pressure on the development day x, and the following formula is obtained:
in the formula:
qAOFthe gas test unobstructed flow of the gas well which has the gas test and is put into production in the flow unit of the target gas well is 104m3/d；
qgxThe average daily gas production of the gas well which is subjected to gas test and put into production in the previous x days of the early development stage is 104m3/d；
pOil xThe gas well has a gas test in a flow unit where the target gas well is located, and the gas well after production develops wellhead oil pressure of x day in the early development stage, wherein the pressure is MPa;
β1is a constant term, β2～β5Is a regression coefficient;
103, acquiring the average daily gas production rate q of the target gas well x days before the early development stagegxAnd wellhead oil pressure p on day xOil xSubstituting the formula (1) into the formula (1), and calculating the early unobstructed flow of the similar gas testing unobstructed flow of the target gas well;
and 104, establishing a regression curve of the gas test unobstructed flow of all the gas wells with the gas test and the production time of more than n years in the flow unit where the target gas well is located and the average daily gas production of the previous n years of the production gas well corresponding to each gas test unobstructed flow, and determining the production allocation of the target gas well in the early development stage according to the regression curve, wherein n is a positive integer.
4. The method for evaluating the productivity of the gas well of the hypotonic carbonate gas reservoir according to claim 3, wherein the production test data of the target gas well in different production stages are obtained by dividing different production stages of the target gas well, wherein the middle development stage refers to a development period from x +1 day to a period from the time when the oil pressure at the wellhead is reduced to the output pressure at the wellhead, and the production test data for evaluating the productivity of the target gas well in the middle development stage comprises the following steps:
the formation pressure, the deviation factor and the gas viscosity of the produced gas well of the flow unit where the target gas well is located, and the bottom hole flow pressure of the target gas well.
5. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 4,
and respectively evaluating the capacity of the target gas well at different production stages according to the flow unit and the production test data, wherein the capacity evaluation method at the middle development stage comprises the following steps:
step 201, determining coefficients A and B of a binomial capacity equation of a target gas well in the early development stage;
step 202, establishing a correlation relation regression curve of the product of the gas well stratum pressure-gas viscosity and the deviation factor of the produced gas well in the flowing unit of the target gas well at different testing time, obtaining the current stratum pressure of the target gas well and substituting the current stratum pressure into the correlation relation regression curve to obtain the product of the gas viscosity and the deviation factor of the target gas well under the current stratum pressure;
step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd Bm；
Step 204, obtaining the unobstructed flow of the target gas well under the current formation pressure;
step 205, substituting the unobstructed flow of the target gas well under the current formation pressure into the regression curve established in the step 104 to determine the production allocation of the target gas well in the development middle period;
the current formation pressure at each of the above steps is referred to as the current formation pressure of the target gas well during development.
6. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 5,
in step 201, determining the values of the coefficients a and B for developing the early-stage gas well binomial energy production equation is specifically performed according to the following formulas:
in the formula:
pRis the original formation pressure of the target gas well, MPa;
qAOF early stageIs the open flow rate of the target gas well at an early stage of development, 104m3/d；
PwfxThe bottom hole flowing pressure of the target gas well on the x day of the early development is MPa;
qgxis the average daily gas production of the target gas well x days prior to the early stage of development, 104m3/d。
7. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 6,
step 203, correcting and developing the coefficient A value and the coefficient B value of the early gas well binomial productivity equation by the product of the gas viscosity of the target gas well under the current formation pressure and the deviation factor, wherein the corrected values are AmAnd BmThe method comprises the following steps:
Am＝AZmμgm/Zμg (4)
Bm＝BZmμgm/Zμg (5)
in the formula:
a is the coefficient A value of the developed early gas well binomial productivity equation found according to equation (2) in step 201;
b is the coefficient B value of the developed early gas well binomial productivity equation found according to equation (3) in step 201;
Zμgis the product of the deviation factor of the target gas well at the original formation pressure and the gas viscosity;
Zmμgmis the product of the deviation factor and the gas viscosity for the target gas well at the current formation pressure.
8. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 7,
in step 204, the unobstructed flow of the target gas well under the current formation pressure is obtained, which is specifically as follows:
in the formula:
pRmis the current formation pressure of the target gas well;
qmiddle stage of AOFIs the current unobstructed flow rate of the target gas well.
9. The method for evaluating the productivity of the gas well of the hypotonic carbonate gas reservoir according to claim 3, wherein the different production stages of the target gas well are divided, and production test data of the target gas well in the different production stages are obtained, wherein the final development stage refers to a time period from the wellhead oil pressure being lower than the wellhead output pressure until the gas well is scrapped, and the production test data for evaluating the productivity of the target gas well in the final development stage comprise:
and the gas testing non-resistance flow or early-stage non-resistance flow of all the produced gas wells under the same flow unit and the final accumulated gas of the produced gas wells corresponding to the gas testing non-resistance flow.
10. The method of evaluating the productivity of a hypotonic carbonate gas reservoir gas well of claim 9,
and respectively evaluating the capacity of the target gas well in different production stages according to the flow unit and the production test data, wherein the capacity evaluation method in the later development stage comprises the following steps:
step 301, obtaining the gas testing non-resistance flow or the early non-resistance flow of all produced gas wells under the same flow unit and the final accumulated gas production result of the produced gas wells corresponding to the gas testing non-resistance flow, wherein the gas testing non-resistance flow refers to the non-resistance flow obtained by the gas testing and the early non-resistance flow refers to the early non-resistance flow calculated by using the development early productivity evaluation method when the gas testing is not available;
step 302, establishing a correlation relation regression curve of the final accumulated gas of the production gas wells corresponding to the gas testing non-resistance flow or the early non-resistance flow of all the production gas wells in the step 301 and the gas testing non-resistance flow;
step 303, selecting a yield decreasing stage of the target gas well in the later development stage, and predicting final accumulative gas under different decreasing types by using an Arps decreasing model, wherein the decreasing types comprise exponential decreasing, harmonic decreasing and hyperbolic decreasing;
and 304, substituting the gas test non-resistance flow or the early-stage non-resistance flow of the target gas well into the correlation relation regression curve in the step 302 to obtain the final accumulated gas yield under the corresponding non-resistance flow, wherein the descending type closest to the final accumulated gas yield is determined as the descending type of the target gas well, and guiding the production allocation of the target gas well in the later development stage according to the descending rule corresponding to the descending type.
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