CN117072145A - Method for determining effective thickness of down-the-mine reservoir through well test curve - Google Patents
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Abstract
The application relates to a method for determining the effective thickness of a subsurface reservoir through a well test curve, which comprises the following steps: step A, obtaining output and bottom hole pressure data of a test well in different working systems; b, calculating a bottom hole pressure derivative when the well is closed according to the bottom hole pressure data obtained in the step A, and obtaining a bottom hole pressure derivative curve; determining the thickness of a contributing layer section of a reservoir around a shaft through a production logging technology; d, establishing a buried hill reservoir dual medium spherical flow interpretation model according to the yield obtained in the step A; E. and (3) bringing the thickness of the reservoir contribution layer section around the shaft in the step (C) into the spherical flow interpretation model of the subsurface reservoir dual medium in the step (D), generating a bottom hole pressure derivative graph curve, performing optimization fitting on the bottom hole pressure derivative graph curve and the bottom hole pressure derivative curve in the step (B), and calculating to obtain optimized reservoir parameters and reservoir effective thickness. The method can accurately obtain the actual effective thickness of the large section of the submarine mountain reservoir within the detection radius of the test well.
Description
Technical Field
The application relates to the technical field of oil and gas field exploration and development, in particular to a method for determining the effective thickness of a subsurface reservoir through a well test curve.
Background
The effective thickness of the hydrocarbon reservoir is one of important parameters in the process of calculating the oil and gas geological reserves, and the accuracy of the parameters has great influence on the reliability of the finally calculated oil and gas geological reserves. In the oil and gas field exploration stage, the effective thickness and physical properties of the reservoir are evaluated by technical means such as earthquake, logging and the like, and the reserves of petroleum and natural gas of the reservoir are estimated by using a volumetric method so as to finish the reserve declaration and the formulation of the overall development scheme of the oil and gas field.
However, these current evaluation techniques have certain limitations. First, the evaluation of the earthquake explains that the resolution in the longitudinal direction is low, and the determination of the effective thickness of the reservoir cannot be satisfied. Furthermore, the main scope of application of the well logging and evaluation method is the small area around the well bore, and the effective thickness of the reservoir layer around the test well (the target well to be tested or the oil and gas well) in a large area cannot be determined. Particularly, for exploratory wells and evaluation wells of the subsurface mountain layer, the test well is a large section of open hole well, and has very strong heterogeneity of crack development degree and reservoir physical properties in the longitudinal direction and the radial direction, so that difficulty is brought to interpretation and evaluation of earthquake, logging and well logging, and the effective thickness of the subsurface mountain reservoir is difficult to determine.
In recent years, a production logging technology (PLT, production Logging Test) has been successfully applied to open hole wells, so that the effective production interval of a large-section open hole test well can be judged, but the open hole completion mode of a large-section down-the-hole mountain is easily affected by factors such as long-time soaking of drilling fluid, so that the flow channel of a part of the interval in a near-wellbore zone is blocked, and the PLT is used for judging the effective production interval of the large-section open hole test wellOnly can judge the thickness h of the effective production section of the reservoir around the shaft participating in the flow W The actual effective thickness h of the reservoir cannot be judged; well testing explains that formation coefficient kh is determined by dynamic changes in production and pressure, but permeability k and effective reservoir thickness h cannot be split quantitatively. In 1988, a seepage model between the partial jet thickness of a homogeneous reservoir and the reservoir thickness was established by Joseph and Tang; chen Fangfang and Gu Yonglu establish a seepage model between the partial jet thickness and the reservoir thickness of the dual medium reservoir in 2008, but in these seepage models, the effective thickness h of the whole reservoir can only be used as a known quantity, and only the reservoir thickness value of the reservoir around the well bore participating in the flow is obtained through optimization fitting analysis.
Accordingly, the effective thickness of the reservoir is evaluated by using logging, logging and PLT technical methods, only the attribute of the reservoir near the well bore of the test well can be reflected, and the evaluation interpretation of the earthquake is insufficient due to low resolution in the longitudinal direction; physical property information of the reservoir in a larger range can be obtained by the well test and interpretation technology, but the actual effective thickness value of the reservoir is still difficult to accurately determine.
Disclosure of Invention
The application provides a method for determining the effective thickness of a buried hill reservoir through a well test curve, which is used for accurately obtaining the actual effective thickness of a large section of buried hill reservoir within the detection radius of a test well.
The application relates to a method for determining the effective thickness of a reservoir of a down-the-mine through a well test curve, which comprises the following steps:
A. acquiring output and bottom hole pressure data of a test well in different working systems;
B. c, calculating a bottom hole pressure derivative when closing the well according to the bottom hole pressure data obtained in the step A, and obtaining a bottom hole pressure derivative curve;
C. determination of wellbore surrounding reservoir contribution interval thickness h by production logging techniques W ；
D. B, establishing a buried hill reservoir dual medium spherical flow interpretation model according to the yield obtained in the step A;
E. contributing layer section thickness h of reservoir around the shaft in step C W D, carrying out generation in the buried hill reservoir dual-medium spherical flow interpretation modelAnd (3) carrying out optimization fitting on the bottom pressure derivative graph curve and the bottom pressure derivative curve in the step (B), and calculating to obtain optimized reservoir parameters and reservoir effective thickness.
According to the well test method, the distribution range of a reservoir fluid system is determined through the underground fluid pressure change and recovery process, and information such as reservoir permeability and productivity is determined. In general, data is obtained by logging techniques, which are used to guide the next well test. Logging refers to measuring physical parameters of formations around a borehole, such as acoustic waves, resistivity, neutron density, natural gamma ray intensity and the like, by various downhole instruments, and realizing lithology recognition, reservoir partitioning, determination of hydrocarbon and water layers and evaluation of reservoir parameters by logging technical interpretation.
The application judges whether the large section of the down-the-hole test well has spherical flow characteristics by using a well test curve method, interprets the production layer contribution section around the shaft by combining the production logging technology, and obtains the actual effective thickness of the whole reservoir by the optimized fitting analysis of the well test curve (namely, the bottom pressure derivative curve) and the model curve (namely, the bottom pressure derivative plate curve).
In the prior art, the technologies of earthquake, logging, core analysis and the like all belong to static evaluation methods, and the technology reflects stratum properties of a borehole or the vicinity thereof. The application is based on the well test dynamic test, can well represent the actual characteristics of the reservoir under the dynamic condition, reflects the effective thickness of the reservoir in the larger detection range of the test well and the periphery thereof, and provides guidance for the exploration of the reservoir declaration and the formulation of the overall development scheme.
Further, the test well in the step A is an oil well or a gas well, and the yield comprises one or more of liquid yield, oil yield, water yield and gas yield.
Furthermore, the working system in the step A refers to two working states of a test well realized according to the sequence of firstly opening the well for production and then closing the well; the open-well production is a process of realizing one or more production changes by changing the size of a choke.
A specific calculation method is that the calculating of the bottom hole pressure derivative in the well closing process in the step B comprises the following steps: and D, calculating to obtain a bottom hole pressure derivative changing with time according to the bottom hole pressure data obtained in the step A:
wherein p is wD ' is the derivative of the bottom hole pressure,to be at time node t k Time bottom hole pressure derivative, dp wD To differentiate bottom hole pressure, p wD Is the bottom hole pressure, d is p wD T is the shut-in time, L is half the length of the smooth window, k+L is the rightmost data point position of the window, and k-L is the leftmost data point position of the window.
Further, determining the thickness h of the contribution layer section of the reservoir around the shaft through the production logging technology in the step C W The production logging technology is used for testing and explaining the interval of the test well participating in fluid flow in the open-hole production state in the step A, thereby obtaining the thickness h of the contribution interval of the reservoir around the well shaft W 。
Specifically, the production logging technology test is that parameter variables related to the depth of the open hole interval of the submarine mountain are tested and obtained through an instrument, and the method comprises the following steps: magnetic positioning, natural gamma ray intensity, water holdup, turbine speed, density, temperature and pressure; the magnetic positioning and natural gamma ray intensity are used for assisting the depth correction of other parameter variables, the density and the water holding rate are used for identifying the fluid holding rate of each phase in the mixed phase fluid, the temperature and the pressure are used for setting high-pressure physical parameters of the fluid, and the turbine rotating speed is used for calculating the apparent flow rate of the fluid in the well.
Interpretation by production logging techniques refers to obtaining the production profile of a large section of subsurface reservoirs and the thickness h of the reservoir contribution interval around the wellbore by production logging techniques W 。
Further, in step D, a dual medium spherical flow of the down-the-hill reservoir is establishedWhen the model is interpreted, according to the obtained production of the test well, the dependent variables and independent variables for establishing the buried hill reservoir dual medium spherical flow interpretation model are obtained, wherein the dependent variables comprise the bottom hole pressure p wD The independent variables include production, reservoir parameters, and time t, which is the production of the last open well prior to shut-in.
And D, determining the buried hill reservoir dual-medium spherical flow interpretation model in the step D according to the type of the oil and gas reservoir, the inner boundary condition and the outer boundary condition. For the situation that micro cracks exist in a submarine mountain reservoir for comparison development, a characteristic curve of the submarine mountain reservoir dual-medium spherical flow interpretation model shows the characteristics of a dual-medium model; for the open hole production of the large section of the submarine mountain, and the situation that part of the layer sections do not participate in the flow exists, the characteristic curve of the submarine mountain reservoir dual-medium spherical flow interpretation model shows the characteristic of spherical flow.
Further, step E, when performing optimization fit, adds the wellbore surrounding reservoir contribution interval thickness h to step C W And (3) bringing the initial value of the reservoir parameter and the initial value of the reservoir effective thickness into the spherical flow interpretation model of the dual medium of the subsurface reservoir in the step (D), generating a corresponding bottom hole pressure derivative graph plate curve by adjusting different values of the reservoir parameter and the reservoir effective thickness, and carrying out optimization fitting calculation on the bottom hole pressure derivative graph plate curve and the bottom hole pressure derivative curve in the step (B) to obtain the optimized reservoir parameter and the reservoir effective thickness. And the initial values of the reservoir parameters and the initial values of the effective thickness of the reservoir are obtained by the interpretation result of the logging technology.
Specifically, the optimization fitting is achieved through a nonlinear regression algorithm.
The beneficial effects of the application include:
1. whether the test well has spherical flow characteristics or not can be judged through the well test curve characteristics of the measured data, and whether the large-section submarine test has the condition that the reservoir sections around the well shaft do not participate in the flow or not is determined.
2. And generating an interpretation chart (a bottom hole pressure derivative chart curve) through a buried hill reservoir dual medium spherical flow interpretation model, and obtaining the quantitative relation between the thickness of a reservoir contribution section around the shaft and the effective thickness of the reservoir through optimal fitting with measured data.
3. And the thickness of the reservoir contribution interval around the shaft is interpreted by combining the production logging technology, so that quantitative interpretation of the effective thickness of the reservoir in the effective radial test range of the test well is realized.
4. Based on the well test dynamic test, the actual characteristics of the reservoir under the dynamic condition can be well represented, the effective thickness of the reservoir in the larger detection range of the test well and the periphery of the test well is reflected, and guidance is provided for the establishment of the exploration of the reserve declaration and the overall development scheme.
Drawings
FIG. 1 is a flow chart of a method of determining the effective thickness of a down-the-hill reservoir by a well test curve in accordance with the present application.
FIG. 2 is a schematic diagram of a dual medium spherical flow model of a subsurface reservoir in accordance with the present application.
FIG. 3 is a graph of model pressure and model pressure derivative for a dual medium spherical flow model for a subsurface reservoir in accordance with the present application.
FIG. 4 is production and bottom hole pressure data for a well in the field.
Fig. 5 is a graph of a test of the bottom hole pressure at a shut-in stage of an oil well in the field.
Fig. 6 is a diagram for explaining the result of the production logging technique at the production stage of opening a certain oil well on site.
FIG. 7 is a plot of an analysis of an optimization fit of a well in the field.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present application.
As shown in fig. 1, the method for determining the effective thickness of the down-the-hill reservoir by using the well test curve comprises the following steps:
A. acquiring output and bottom hole pressure data of a test well in different working systems;
B. c, calculating a bottom hole pressure derivative when closing the well according to the bottom hole pressure data obtained in the step A, and obtaining a bottom hole pressure derivative curve;
C. determination of wellbore surrounding reservoir contribution interval thickness h by production logging techniques W ；
D. B, establishing a buried hill reservoir dual medium spherical flow interpretation model according to the yield obtained in the step A;
E. contributing layer section thickness h of reservoir around the shaft in step C W And D, carrying out optimization fitting on the bottom hole pressure derivative graph curve and the bottom hole pressure derivative curve in the step B, and calculating to obtain optimized reservoir parameters and reservoir effective thickness.
The application judges whether the large section of the down-the-hole test well has spherical flow characteristics by using a well test curve method, interprets the production layer contribution section around the shaft by combining the production logging technology, and obtains the actual effective thickness of the whole reservoir by the optimized fitting analysis of the well test curve (namely, the bottom pressure derivative curve) and the model curve (namely, the bottom pressure derivative plate curve).
In the prior art, the technologies of earthquake, logging, core analysis and the like all belong to static evaluation methods, and the technology reflects stratum properties of a borehole or the vicinity thereof. The application is based on the well test dynamic test, can well represent the actual characteristics of the reservoir under the dynamic condition, reflects the effective thickness of the reservoir in the larger detection range of the test well and the periphery thereof, and provides guidance for the exploration of the reservoir declaration and the formulation of the overall development scheme.
In step a, the test well is an oil or gas well, and the production includes one or more of liquid production, oil production, water production, and gas production. The working system refers to two working states of a test well realized according to the sequence of firstly opening the well for production and then closing the well; the open-well production is a process of realizing one or more production changes by changing the size of a choke. Various data acquisition methods for testing wells may be implemented with reference to the "oil field well test specification SY/T6172-2022" and the "gas well test specification SY/T5440-2019".
And B, calculating the bottom hole pressure derivative during well closing, wherein the bottom hole pressure derivative which changes along with time is calculated according to the bottom hole pressure data acquired in the step A:
wherein p is wD ' is the derivative of the bottom hole pressure,to be at time node t k Time bottom hole pressure derivative, dp wD To differentiate bottom hole pressure, p wD Is the bottom hole pressure, d is p wD T is the shut-in time, L is the smooth window length, k+L is the rightmost data point position of the window, and k-L is the leftmost data point position of the window.
Determining the thickness h of a reservoir contribution layer section around a shaft through a production logging technology in step C W The production logging technology is used for testing and explaining the interval of the test well participating in fluid flow in the open-hole production state in the step A, thereby obtaining the thickness h of the contribution interval of the reservoir around the well shaft W 。
The production logging technology test is that seven parameter variables related to the depth of a subsurface open hole interval are tested and obtained through an instrument, and the production logging technology test comprises the following steps: magnetic positioning, natural gamma ray intensity, water holdup, turbine speed, density, temperature and pressure; the magnetic positioning and natural gamma ray intensity are used for assisting the depth correction of other parameter variables, the density and the water holding rate are used for identifying the fluid holding rate of each phase in the mixed phase fluid, the temperature and the pressure are used for setting high-pressure physical parameters of the fluid, and the turbine rotating speed is used for calculating the apparent flow rate of the fluid in the well.
Interpretation by production logging techniques refers to obtaining the production profile of a large section of subsurface reservoirs and the thickness h of the reservoir contribution interval around the wellbore by production logging techniques W . For example, relevant parameters obtained by production logging technology test are input into corresponding interpretation software to be interpreted, so that the production profile of the large-section subsurface reservoir and the thickness h of the reservoir contribution interval around the well shaft are obtained W 。
The method for testing and explaining the production profile of the large-section submarine mountain reservoir can refer to the 1 st part of injection, production profile logging data processing and explaining standard: "vertical well SY/T5783.1-2012" and part 2: "inclined shaft SY/T5783.2-2016" is implemented.
And D, determining the spherical flow interpretation model of the dual medium of the subsurface reservoir in the step D according to the oil and gas reservoir type, the inner boundary condition and the outer boundary condition when the spherical flow interpretation model of the dual medium of the subsurface reservoir is established.
The reservoir type comprises one of a homogeneous oil or gas reservoir, a dual medium oil or gas reservoir, a double-seepage oil or gas reservoir and a compound oil or gas reservoir, and belongs to the dual medium oil or gas reservoir for the reservoir type of the subsurface mountain reservoir.
The internal boundary condition comprises one of a vertical well, an inclined well, a horizontal well, a partial jet, a limited diversion fracture and an infinite diversion fracture.
The outer boundary condition includes one of an infinite boundary, a circular closed boundary, a circular constant pressure boundary, one or two or three impermeable boundaries, one or two or three constant pressure boundaries.
From the obtained production of the test well, obtaining the dependent variables and independent variables for establishing a buried hill reservoir dual medium spherical flow interpretation model, wherein the dependent variables comprise bottom hole pressure p wD The independent variables include production, reservoir parameters, and time t, which is the production of the last open well prior to shut-in.
For the condition that micro cracks exist in the submarine mountain reservoir for comparative development, the submarine mountain reservoir is double-mediumThe characteristic curve of the spherical flow interpretation model shows the characteristics of the dual medium model; for the open hole production of the large section of the submarine mountain, and the situation that part of the layer sections do not participate in the flow exists, the characteristic curve of the submarine mountain reservoir dual-medium spherical flow interpretation model shows the characteristic of spherical flow. FIG. 2 shows a schematic diagram of a buried hill reservoir dual medium spherical flow interpretation model, where h is the effective reservoir thickness, h W Contributing layer section thickness to reservoir around a shaft, wherein H is the thickness of the whole buried hill reservoir test section, Z a Contributing to the height of the top surface of the interval to the top surface of the effective thickness interval of the reservoir around the shaft, Z b The height from the bottom surface of the contributing layer section to the top surface of the effective thickness section of the reservoir for the reservoir around the well bore, arrows 1, 2, 3 are schematic flow lines of oil (or gas) in the reservoir, arrow 1 represents the radial flow characteristics of the contributing layer section of the reservoir around the well bore; arrow 2 represents a spherical flow feature; arrow 3 represents the radial flow characteristics of the reservoir effective thickness section. FIG. 3 is a graph of characteristics of a well test curve (i.e., bottom hole pressure derivative graph curve) of a down-the-hole reservoir dual medium spherical flow interpretation model, wherein the graph is shown as a pressure characteristic curve at the upper part and a pressure derivative characteristic curve at the lower part in FIG. 3.
Wherein, the buried hill reservoir dual medium spherical flow interpretation model is specific to the bottom hole pressure p wD The method is solved in Laplace space, and comprises the following steps:
wherein:
L D ＝h w /h (5)；
wherein:representing a solution of bottom hole pressure in Laplace space; />The solution of bottom hole pressure in Laplace space when the skin coefficient and dimensionless well storage coefficient are not considered; u is a laplace variable; s is the skin coefficient; c (C) D Is a dimensionless well Chu Jishu; h is a D Is dimensionless reservoir thickness; z D Is a dimensionless longitudinal distance; z aD And z bD The dimensionless distance between the top surface and the bottom surface of the reservoir contribution layer section around the shaft and the top surface of the reservoir effective thickness section is respectively calculated; k (K) 0 (x)、K 1 (x) The functions are zero-order and first-order virtual volume Bessel functions respectively; lambda (lambda) m A cross flow coefficient for the matrix to generate quasi-steady cross flow to the crack; omega m An elastic reservoir ratio that is a matrix; omega f An elastic reservoir ratio that is a fracture system; l (L) D Contributing to the reservoir surrounding the wellbore a proportion of the reservoir effective thickness to the interval thickness; h is a w Contributing interval thickness to the reservoir surrounding the wellbore; h is the effective thickness of the reservoir.
Obtained by Stehfest numerical inversionSolution of bottom hole pressure in real space p wD Deriving the bottom-hole pressure can obtain the pressure derivative p of the bottom-hole pressure wD ′。
The method for establishing and solving the buried hill reservoir dual-medium spherical flow interpretation model refers to the modern well test interpretation method (oil industry press) of Liao Xinwei and the dual-medium partially jet seepage model and well test template curve (Daqing petroleum geology and development) of Chen Fangfang.
E, when optimization fitting is carried out, obtaining an initial value of a reservoir parameter and an initial value of an effective reservoir thickness according to a result interpreted by a logging technology, and then contributing the reservoir section thickness h around the shaft in the step C W And (D) bringing the initial values of reservoir parameters and the initial values of reservoir effective thickness into the buried hill reservoir dual-medium spherical flow interpretation model in the step (D) through adjustmentAnd B, integrating different values of the reservoir parameters and the reservoir effective thickness, generating a corresponding bottom-hole pressure derivative graph curve, and carrying out optimization fitting calculation on the bottom-hole pressure derivative graph curve and the bottom-hole pressure derivative curve in the step B to obtain the optimized reservoir parameters and the reservoir effective thickness.
The optimization fit is achieved by a nonlinear regression algorithm, wherein the objective function is defined as follows:
wherein: phi (x) is an objective function to be optimized; p is p wD1 ′(t k ) At t k The pressure derivative corresponding to the moment, i.e. the one obtained by equation (1) of step Bp wD2 ′(x,h,t k ) At t k D, the time-of-day down-the-hill reservoir dual-medium spherical flow interpretation model passes through the formula (2) of the step D, and pressure derivative obtained after Stehfest numerical inversion is carried out, wherein x represents reservoir parameters, and h represents reservoir effective thickness; n is the number of test pressure data points; sigma (sigma) k Standard deviation measured for the kth point.
The variables to be optimized in the objective function are a reservoir parameter x and a reservoir effective thickness h.
The optimization fitting process is described with reference to John P.Spivey, method of interpretation of practical well tests (oil industry Press)
The effective thickness H of the reservoir obtained after the optimization fitting is smaller than the thickness H of the whole buried hill reservoir test section.
The application is further described in connection with the following test data for a well:
the method for determining the effective thickness of the reservoir of the down-the-mine through the well test curve comprises the following steps:
A. the method is characterized in that an oil well of the subsurface reservoir is tested in an open hole well completion mode, the test well section is 2113 m-2608 m, and the overall thickness of the test section is 495m. In the production stage of well opening, 3 working systems are tested by adjusting a choke, and the ground metering yield is 167 square/day, 159 square/day and 330 square/day respectively; and closing the well after the last working system test is finished, and performing a pressure recovery test. A storage manometer on the test string obtains bottom hole pressure variation data during the test. The production and bottom hole pressure changes over time are shown in figure 4.
B. And calculating the derivative of the bottom hole pressure data in the well closing stage according to the corresponding relation between the measured output data and time. In the pressure derivative well test curve shown in FIG. 5, the duration of the shut-in phase is 12hr, and the spherical flow characteristics with a very pronounced-1/2 slope appear at the 0.01 hr-0.1 hr position on the log well test curve.
C. During open-hole testing, after running a tool of production logging technology, the contributing intervals of the reservoir around the full interval wellbore are measured, as shown in fig. 6. Production logging interpretation showed that the thickness of the major contributing interval was 96.6m, with a relative production rate of 100%
D. Establishing a buried hill reservoir dual medium spherical flow interpretation model (hereinafter referred to as model) with a shaft radius of 0.108m, a porosity of 6.47%, a volume coefficient of 1.62, a fluid viscosity of 0.175cp under stratum conditions and an oil compression coefficient of 0.0028MPa -1 The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the section of the well (reservoir contributing section around the wellbore) partially participating in the flow in the model was 96.6m as explained in step C. Depending on the reservoir parameters and the effective reservoir thickness, a plurality of template curves of pressure derivatives (model pressure derivatives in fig. 3), i.e., a plurality of well test curves as shown in fig. 3, may be generated.
E. And (3) carrying out optimization fitting analysis on the template curve (i.e. fig. 3) of the pressure derivative (model pressure derivative in fig. 3) and the data of the measured pressure derivative (i.e. fig. 5) in the step (B) based on the objective function in the formula (6), so as to obtain the optimal reservoir parameter and the reservoir effective thickness value. The best fit analysis curve is shown in fig. 7. The overall relation is that the curve of the first figure 3 is generated according to the initial value of the reservoir parameter and the initial value of the effective thickness of the reservoir; by continuously adjusting the reservoir parameter x and the reservoir effective thickness h, generating a plurality of curves of figure 3, and fitting the figures 3 and 5 until the figure 7 state with the best fitting degree is reached, the obtained parameter is the optimal reservoir effective thickness h required by the application. In fig. 7, the model pressure curve is overlapped with the test pressure curve at the upper part, and the model pressure derivative curve is overlapped with the test pressure derivative curve at the lower part. Reservoir parameters include detection radius, permeability, skin coefficient, well storage coefficient, energy storage ratio, and fluid channeling coefficient, etc. The detection radius of the well test is 210m and the thickness h is 162m through optimization fit analysis. Namely, the average effective thickness of the reservoir layer is 162m in the radius range of 210m by taking the well as the center of a circle. The effective thickness of the reservoir in the detection range is obtained through well test curve interpretation, and guidance is provided for reservoir reserve calculation and development scheme formulation.
The above examples merely illustrate specific embodiments of the application, which are described in more detail and are not to be construed as limiting the scope of the application. It should be noted that, for those skilled in the art, it is possible to make related modifications and improvements without departing from the technical idea of the application, which fall within the protection scope of the application.
Claims (10)
1. The method for determining the effective thickness of the down-the-mine reservoir through the well test curve is characterized by comprising the following steps of: the method comprises the following steps:
A. acquiring output and bottom hole pressure data of a test well in different working systems;
B. c, calculating a bottom hole pressure derivative when closing the well according to the bottom hole pressure data obtained in the step A, and obtaining a bottom hole pressure derivative curve;
C. determination of wellbore surrounding reservoir contribution interval thickness h by production logging techniques W ；
D. B, establishing a buried hill reservoir dual medium spherical flow interpretation model according to the yield obtained in the step A;
E. contributing layer section thickness h of reservoir around the shaft in step C W And D, generating a bottom hole pressure derivative graph curve in the spherical flow interpretation model of the double medium of the down-the-hole reservoir stratum, and feeding the bottom hole pressure derivative graph curve and the bottom hole pressure derivative graph of the step BAnd performing optimization fitting, and calculating to obtain optimized reservoir parameters and reservoir effective thickness.
2. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: the test well in the step A is an oil well or a gas well, and the production comprises one or more of liquid production, oil production, water production and gas production.
3. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: the working system in the step A refers to two working states of a test well realized according to the sequence of firstly opening the well for production and then closing the well; the open-well production is a process of realizing one or more production changes by changing the size of a choke.
4. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: the calculating the bottom hole pressure derivative when closing the well in the step B comprises the following steps: and D, calculating to obtain a bottom hole pressure derivative changing with time according to the bottom hole pressure data obtained in the step A:
wherein p is wD ' is the derivative of the bottom hole pressure,to be at time node t k Time bottom hole pressure derivative, dp wD To differentiate bottom hole pressure, p wD Is the bottom hole pressure, d is p wD T is the shut-in time, L is half the length of the smooth window, k+L is the rightmost data point position of the window, and k-L is the leftmost data point position of the window.
5. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: step (a)Determining the thickness h of a reservoir contribution layer section around a shaft through production logging technology W The production logging technology is used for testing and explaining the interval of the test well participating in fluid flow in the open-hole production state in the step A, thereby obtaining the thickness h of the contribution interval of the reservoir around the well shaft W 。
6. The method for determining the effective thickness of a down-the-hill reservoir by well test curves according to claim 5, wherein: the production logging technology test is that parameter variables related to the depth of a subsurface open hole interval are tested and obtained through an instrument, and the method comprises the following steps: magnetic positioning, natural gamma ray intensity, water holdup, turbine speed, density, temperature and pressure;
interpretation by production logging techniques refers to obtaining the production profile of a large section of subsurface reservoirs and the thickness h of the reservoir contribution interval around the wellbore by production logging techniques W 。
7. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: in the step D, when the buried-hill reservoir dual-medium spherical flow interpretation model is established, according to the obtained production of the test well, obtaining the dependent variables and independent variables for establishing the buried-hill reservoir dual-medium spherical flow interpretation model, wherein the dependent variables comprise the bottom hole pressure p wD The independent variables include production, reservoir parameters, and time t, which is the production of the last open well prior to shut-in.
8. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 1, wherein: for the situation that micro cracks exist in the submarine mountain reservoir for comparison development, the characteristic curve of the submarine mountain reservoir dual-medium spherical flow interpretation model in the step D shows the characteristics of the dual-medium model; for the open hole production of the large section of the submarine mountain, and the situation that part of the layer sections do not participate in the flow exists, the characteristic curve of the submarine mountain reservoir dual-medium spherical flow interpretation model shows the characteristic of spherical flow.
9. As claimed inThe method for determining the effective thickness of the down-the-hill reservoir through the well test curve is characterized by comprising the following steps: step E, when optimization fitting is performed, contributing layer section thickness h of reservoir around the shaft in step C W And (3) bringing the initial value of the reservoir parameter and the initial value of the reservoir effective thickness into the spherical flow interpretation model of the dual medium of the subsurface reservoir in the step (D), generating a corresponding bottom hole pressure derivative graph plate curve by adjusting different values of the reservoir parameter and the reservoir effective thickness, and carrying out optimization fitting calculation on the bottom hole pressure derivative graph plate curve and the bottom hole pressure derivative curve in the step (B) to obtain the optimized reservoir parameter and the reservoir effective thickness.
10. The method for determining the effective thickness of a down-the-hill reservoir by well test curves as claimed in claim 9, wherein: the optimal fit is achieved by a nonlinear regression algorithm.
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