Fracture closing identification method for ultra-deep fault control fracture-vuggy carbonate reservoir

Abstract

The invention provides an ultra-deep fault control fracture-vuggy carbonate reservoir fracture closure recognition method, and relates to the technical field of reservoir engineering, and the method comprises the steps: for a target reservoir, selecting a production data segment for fracture closure recognition, and determining production dynamic data corresponding to the production data segment; based on the production dynamic data, calculating to obtain quasi-substance equilibrium time, a liquid production curve slope of two adjacent effective data points and a liquid production curve intercept so as to calculate to obtain crack closing identification parameters corresponding to each data point in the production data segment; and determining a fracture closed section of the target oil reservoir according to the fracture closed identification parameters. Compared with the traditional physical experiment and numerical simulation means, the method can quickly and conveniently identify the fracture closed section of the ultra-deep fault control fracture-vuggy carbonate reservoir, has the characteristics of short time and quick identification, and is high in operability and convenient to apply on site due to the fact that fracture closing is identified based on actual oil reservoir oil well production dynamic data.

Description

Technical Field

[0001] The invention relates to the technical field of oil reservoir engineering, and in particular to a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs. Background Art

[0002] Ultra-deep fault-controlled fracture-cave carbonate reservoirs are widely developed with fractures and caves. Fractures are oil and gas storage and flow channels, which play a vital role in the development of fracture-cave reservoirs. In the early stage of development, in order to make full use of the elastic energy of the formation, depletion development is often adopted. In the middle stage of development, water injection is often used to increase oil well production and reservoir recovery. In the process of depletion development, as the formation pressure decreases, the fracture opening gradually decreases, and the fracture closure occurs. The closure of the fracture will greatly reduce the conductivity of the fracture system and directly affect the development effect of the reservoir. In the water injection development stage, the conditions for reopening the fractures that were closed in the early stage are more stringent, which is closely related to the mechanical properties of the reservoir rock, fluid pressure and geostress field. In the practice of reservoir development, only some fractures can restore their conductivity through water injection. In addition, when the water injection pressure exceeds the fracture opening pressure during the water injection process, it is easy to cause the fractures to open, extend and expand, resulting in the rapid penetration of the injected water along the fractures, causing the oil well to see water prematurely, which has an adverse effect on development. Therefore, from the perspective of water injection, it is also necessary to prevent the closure of the fractures before water injection. In order to effectively prevent fracture closure and reduce the adverse effects of fracture closure on development, it is necessary to accurately identify fracture closure and establish a fracture closure identification method, which is particularly important for the development of ultra-deep fault-controlled fracture-vuggy carbonate reservoirs.

[0003] At present, physical experiments and numerical simulations are mainly used to identify crack closure. However, physical experiments and numerical simulations have the following problems:

[0004] First, physical experimental research has limitations and cannot represent the true properties of reservoir fractures. Reservoirs have a well-developed fracture network with large differences in fracture width. Usually, multiple groups of fractures are developed, and the fractures are interlaced and cut, and most of them are filled with calcite or sand and mud. The fracture group, orientation, dip, density and height are highly heterogeneous. Therefore, it is impossible to obtain representative fractures that characterize the properties of reservoir fractures at the core scale.

[0005] Second, the numerical simulation method requires multiple parameters such as ground stress, reservoir rock mechanics, and fracture surface as basic parameters, but such parameters are difficult to obtain accurately.

[0006] Third, the results of physical experiments and numerical simulations are usually based on single fractures and small and medium-sized fractures. The research conclusions on fracture closure conditions will bring large errors if directly applied to complex fracture-cavity reservoirs, and have certain limitations in their application in oilfield development practice.

[0007] In view of the problems of the prior art, the present invention provides a method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs. Summary of the invention

[0008] In order to overcome the defects of the prior art, the purpose of the present invention is to propose a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, objectively and accurately evaluate whether fractures have closed during the development of fault-controlled fracture-cavity reservoirs, and provide theoretical support for dynamic analysis of such reservoirs, evaluation of reservoir engineering indicators, and preparation of development plans.

[0009] The present invention provides a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, the method comprising:

[0010] For a target oil reservoir, selecting a production data segment for fracture closure identification, and determining production dynamic data corresponding to the production data segment;

[0011] Based on the production dynamic data, the pseudo material balance time, the slope of the liquid production curve of two adjacent valid data points and the intercept of the liquid production curve are calculated to calculate the fracture closure identification parameters corresponding to each data point in the production data segment;

[0012] The fracture closure section of the target reservoir is determined based on the fracture closure identification parameters.

[0013] According to one embodiment of the present invention, the production dynamic data corresponding to the production data segment is determined by the following steps:

[0014] Determine the data type included in the production dynamic data, wherein the production dynamic data includes: original formation pressure of the reservoir, production date of the oil well, single-day well opening time, daily liquid production, water content, and bottom hole flowing pressure;

[0015] Based on the unstable seepage theory under fixed production conditions, the production data segment for fracture closure identification is selected;

[0016] Abnormal points in the production data segment are eliminated to determine the production dynamic data corresponding to the production data segment.

[0017] According to an embodiment of the present invention, based on the unstable seepage theory under fixed production conditions, a production data segment that satisfies the following three conditions is selected for fracture closure identification:

[0018] The oil well start-up production time is not less than the preset start-up production time threshold, and the initial production data segment of the well start-up is not selected;

[0019] The water content of the oil well is less than the preset water content;

[0020] The fluctuation of daily liquid production of oil wells does not exceed the preset fluctuation range.

[0021] According to one embodiment of the present invention, abnormal points in the production data segment are removed according to the following criteria:

[0022] The dynamic development data of oil wells whose single-day well opening time during the development process is less than the preset single-day well opening time threshold are eliminated, and the dynamic development data of oil wells whose oil well production layers have changed are eliminated.

[0023] According to an embodiment of the present invention, the fracture closure identification parameter corresponding to each data point in the production data segment is calculated by the following steps:

[0024] The pseudo material balance time is calculated based on the cumulative liquid production and the daily liquid production;

[0025] Based on the pseudo material balance time and the daily liquid production, the slope of the liquid production curve of two adjacent valid data points is calculated;

[0026] Based on the original formation pressure of the reservoir, the bottom hole flowing pressure, the slope of the liquid production curve, and the pseudo material equilibrium time, the intercept of the liquid production curve between two adjacent valid data points is calculated;

[0027] Based on the intercept of the liquid production curve and in combination with the daily liquid production, the fracture closure identification parameter corresponding to each data point in the production data segment is calculated.

[0028] According to one embodiment of the present invention, the pseudo-material equilibrium time is calculated by the following expression:

[0029]

[0030] The slope of the liquid production curve is calculated by the following expression:

[0031]

[0032] Where: t ps is the pseudo material equilibrium time, d; L p is the cumulative fluid production, t; q l is the daily liquid production, t / d; the superscript i is the valid data point number; k is the slope of the liquid production curve between two adjacent valid data points.

[0033] According to one embodiment of the present invention, the intercept of the liquid production curve is calculated by the following expression:

[0034] IC=p i -p wf -k·t ps

[0035] The crack closure identification parameter is calculated by the following expression:

[0036]

[0037] Where, IC is the intercept of the liquid production curve; p i is the original formation pressure of the reservoir; p wf is the bottom hole flowing pressure; k is the slope of the liquid production curve of two adjacent valid data points; t ps is the pseudo-material equilibrium time, d; K c is the crack closure identification parameter; q l is the daily liquid production, t / d.

[0038] According to one embodiment of the present invention, the fracture closure section of the target reservoir is determined by the following steps:

[0039] According to the fracture closure identification parameter corresponding to each data point in the production data segment, a fracture closure identification parameter-time curve is drawn with the fracture closure identification parameter as the ordinate and time as the abscissa;

[0040] The obvious mutation point or segment in the fracture closure identification parameter-time curve is marked as the fracture closure segment of the target reservoir.

[0041] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps as described in any one of the above.

[0042] According to another aspect of the present invention, there is also provided a fracture closure identification device for ultra-deep fault-controlled fracture-cavity carbonate reservoirs, which performs the method described in any one of the above items, and the device comprises:

[0043] A production data segment module, which is used to select a production data segment for fracture closure identification for a target reservoir and determine production dynamic data corresponding to the production data segment;

[0044] A fracture closure identification parameter module, which is used to calculate the pseudo-material balance time, the slope of the liquid production curve of two adjacent valid data points and the intercept of the liquid production curve based on the production dynamic data, so as to calculate the fracture closure identification parameters corresponding to each data point in the production data segment;

[0045] The fracture closure section module is used to determine the fracture closure section of the target reservoir according to the fracture closure identification parameters.

[0046] The present invention provides a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, which has the following advantages over the prior art:

[0047] (1) Compared with traditional physical experiments and numerical simulation methods, the present invention can quickly and conveniently identify the fracture closure section of ultra-deep fault-controlled fracture-cavity carbonate reservoirs, and has the characteristics of short time and rapid identification (taking less than 1 hour). In addition, since the fracture closure is identified based on the actual reservoir oil well production dynamic data, it has strong operability and is convenient for field application.

[0048] (2) Based on the unstable seepage theory, the well dynamic data that is easily obtained during the development of ultra-deep fault-controlled fracture-cavity carbonate reservoirs can be used to quickly calculate the fracture closure identification parameters after simple data processing and calculation, and the fracture closure identification parameter-time curve can be drawn. The fracture closure can be identified from the abnormally low value segment (with obvious mutation points or segments) in the curve.

[0049] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 A flowchart showing the steps of a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs according to an embodiment of the present invention is shown;

[0052] Figure 2 A detailed flow chart of the steps of a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs according to an embodiment of the present invention is shown;

[0053] Figure 3 A schematic diagram of a crack closure identification parameter-time curve according to an embodiment of the present invention is shown;

[0054] Figure 4 A curve diagram of fracture closure identification parameters of Well X versus time according to an embodiment of the present invention is shown.

[0055] In the accompanying drawings, the same reference numerals are used for the same components. In addition, the accompanying drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0057] In 2015, a major breakthrough was made in oil and gas exploration in the Tarim Basin. The target layer was buried at a depth of about 7,400 m, which marked the beginning of the rolling exploration and development of ultra-deep (greater than 6,000 m) ultra-deep fault-controlled fracture-cavity carbonate reservoirs (Jiao Fangzheng. Significance and prospects of the discovery of ultra-deep carbonate fault-karst oil and gas reservoirs in Shunbei, Tarim Basin [J]. Petroleum & Natural Gas Geology, 2018, 39(2): 207-216.). Currently, a production capacity of one million tons of oil per year has been built.

[0058] The ultra-deep fault-controlled fracture-cave carbonate reservoir in the Tarim Basin is a special fracture-cave reservoir with fault-controlled karst characteristics. The deep and large strike-slip fault zone controls the storage, accumulation and enrichment of the Ordovician carbonate rocks. After being subjected to multiple stages of structural compression and tension, the carbonate rocks of the Middle and Lower Ordovician developed a certain scale of fracture zones along the deep fault zone. The development and formation of fracture-cave reservoirs are affected by fault fragmentation and dissolution. Oil and gas mainly migrate vertically and fill into reservoirs along the deep and large faults. The reservoir has obvious vertical characteristics. The reservoirs are well connected with each other (Lu Xinbian, Hu Wenge, Wang Yan, et al. Characteristics and development practice of carbonate fault-karst reservoirs in Tahe area [J]. Petroleum & Natural Gas Geology, 2015, 36(3): 347-355. Lu Xinbian, Yang Min, Wang Yan, et al. Characteristics of "strata-controlled" and "fault-controlled" reservoirs in the northern Tarim Basin - Taking the Ordovician of Tahe Oilfield as an example [J]. Petroleum Experimental Geology, 2018, 40(4): 461-469.).

[0059] Ultra-deep fault-controlled fracture-cave carbonate reservoirs are widely developed with fractures and caves. Fractures are oil and gas storage and flow channels, which play a vital role in the development of fracture-cave reservoirs. In the early stage of development, in order to make full use of the elastic energy of the formation, depletion development is often adopted. In the middle stage of development, water injection is often used to increase oil well production and reservoir recovery. In the process of depletion development, as the formation pressure decreases, the fracture opening gradually decreases, and the fracture closure occurs. The closure of the fracture will greatly reduce the conductivity of the fracture system and directly affect the development effect of the reservoir. In the water injection development stage, the conditions for reopening the fractures that were closed in the early stage are more stringent, which is closely related to the mechanical properties of the reservoir rock, fluid pressure and geostress field. In the practice of reservoir development, only some fractures can restore their conductivity through water injection. In addition, when the water injection pressure exceeds the fracture opening pressure during the water injection process, it is easy to cause the fractures to open, extend and expand, resulting in the rapid penetration of the injected water along the fractures, causing the oil well to see water prematurely, which has an adverse effect on development. Therefore, from the perspective of water injection, it is also necessary to prevent the closure of the fractures before water injection. In order to effectively prevent fracture closure and reduce the adverse effects of fracture closure on development, it is necessary to accurately identify fracture closure and establish a fracture closure identification method, which is particularly important for the development of ultra-deep fault-controlled fracture-vuggy carbonate reservoirs.

[0060] At present, physical experiments and numerical simulations are mainly used to identify crack closure.

[0061] The physical experiment mainly studies the deformation law of the fracture structure and the change of fracture permeability during the fracture closure process. Based on the results of the physical experiment, the changes of indicators reflecting the fracture closure (such as wave velocity, flow rate, permeability, closure pressure, etc.) are analyzed, and the fracture closure conditions are established to identify whether the fracture is closed.

[0062] During the confining pressure loading process, the crack closure is reflected by acoustic waves or flow tests: as the stress gradually increases, the longitudinal and transverse wave velocities first increase slowly, then tend to stabilize, and finally drop sharply. The process of slowly increasing wave velocity corresponds to crack closure, when the wave velocity tends to stabilize, it corresponds to compaction, and when the wave velocity drops sharply, it corresponds to crack expansion or the generation of new cracks.

[0063] The change in flow rate during confining pressure loading reflects the change in the amount of fracture closure: First, the distribution of fracture width is statistically analyzed, and the permeability measurement experiment under reservoir conditions is carried out on fractured rock samples through a high-pressure triaxial test system to measure the permeability of fractured rock samples under different effective stresses (pore pressures). When the effective stress increases to a certain value, the permeability remains basically unchanged. Then, the effective stress is gradually reduced, and the permeability will recover, but the permeability increase curve does not coincide with the corresponding decrease curve. At this time, the effective stress has a hysteresis effect on the permeability. The three processes of rapid permeability decrease, basically unchanged permeability, and permeability recovery reflect the process of fracture closure, reaching the maximum closure, and reopening of the fracture (Zhang Xudong, Xue Chengjin, Zhang Ye. Experimental study on rock mechanical parameters and geostress in the Tuofutai area of ​​Tahe Oilfield and its application. Journal of Petroleum and Natural Gas, 2011.33(6):132-134.).

[0064] The experiment revealed that under uniaxial stress conditions, the greater the initial aspect ratio of the crack, the greater the crack closure pressure; when the uniaxial pressure is not perpendicular to the crack surface, the uniaxial pressure needs to be decomposed, and the crack will only close when the angle reaches the critical angle, and the larger the angle, the greater the closure pressure; as the confining pressure increases, the crack opening and permeability gradually decrease; the stronger the ductility of the filling material, the more obvious the crack closure under pressure, and the greater the reduction in permeability (Qiu Hao. Experimental study on crack closure pressure and its influencing factors under uniaxial pressure. Chinese Journal of Rock Mechanics and Engineering, 2015.34(S2):3915-3921.).

[0065] The numerical simulation method mainly uses the finite element method to study the crack closure conditions. The finite element method is to use computers to simulate finely based on the construction of numerical equations and mechanical models. The important links in the simulation research process are the setting of the crack surface and simulation conditions.

[0066] One type of numerical simulation method is to set the fracture as a space between two smooth planes, simplify the reservoir rock into an isotropic ideal elastic body, and the internal fracture consists of two impermeable planes. It is assumed that the reservoir rock is isotropic and uniform, and the direction of the maximum horizontal principal stress is the expansion direction of the internal fracture, and the spatial fracture surface contact problem is simplified to a two-dimensional plane. The crack closure law is studied by simulating the changes in fracture permeability and fracture width under different stress conditions, and based on the crack closure law, it is quantitatively judged whether the fracture is closed.

[0067] Another type of numerical simulation method is to establish a finite element simulation method by considering the development of micro-convex bodies on the fracture surface. Combined with the theory of plastic contact of deformable bodies, a finite element numerical simulation method for a specific fracture in the reservoir rock is established to predict the fracture width and rupture behavior, study the influence of closing pressure on the fracture occurrence and opening, and analyze the critical point of fracture closure on this basis.

[0068] However, at present, physical experiments and numerical simulation methods have the following problems:

[0069] First, physical experimental research has limitations and cannot represent the true properties of reservoir fractures. Reservoirs have a well-developed fracture network with large differences in fracture width. Usually, multiple groups of fractures are developed, and the fractures are interlaced and cut, and most of them are filled with calcite or sand and mud. The fracture group, orientation, dip, density and height are highly heterogeneous. Therefore, it is impossible to obtain representative fractures that characterize the properties of reservoir fractures at the core scale.

[0070] Second, the numerical simulation method requires multiple parameters such as ground stress, reservoir rock mechanics, and fracture surface as basic parameters, but such parameters are difficult to obtain accurately.

[0071] Third, the results of physical experiments and numerical simulations are usually based on single fractures and small and medium-sized fractures. The research conclusions on fracture closure conditions will bring large errors if directly applied to complex fracture-cavity reservoirs, and have certain limitations in their application in oilfield development practice.

[0072] In order to solve the problems of the current prior art, in order to identify whether the fractures of ultra-deep fault-controlled fracture-cavity carbonate reservoirs are closed, the present invention proposes a fracture closure identification method, which collects the original formation pressure, oil well production date, single-day well opening time, daily liquid production, water content, and bottom hole flow pressure, selects the production data segment for evaluation, removes abnormal points, and calculates the pseudo-material balance time, the slope and intercept of the liquid production curve of two adjacent valid data points, and the fracture closure identification parameters in sequence, and identifies the abnormally low value segment (with obvious mutation points or segments) in the fracture closure identification parameter-time curve as the fracture closure segment. The present invention is convenient and highly operable, and has certain guiding significance for identifying whether the fracture is closed.

[0073] Figure 1A flowchart of the steps of a method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to an embodiment of the present invention is shown.

[0074] like Figure 1 As shown, in step S101, for a target oil reservoir, a production data segment for fracture closure identification is selected, and production dynamic data corresponding to the production data segment is determined.

[0075] In one embodiment, in step S101, production dynamic data corresponding to the production data segment is determined through steps S1011-S1013.

[0076] In step S1011, the data types included in the production dynamic data are determined, wherein the production dynamic data include: the original formation pressure p of the reservoir; i , oil well production date, single-day well opening time hour, daily liquid production q1, water content f w , bottom hole pressure p wf The present invention selects actual oil reservoir and oil well production dynamic data to identify fracture closure, has strong operability, and is convenient for on-site application.

[0077] In step S1012, based on the unstable seepage theory under fixed production conditions, a production data segment for fracture closure identification is selected.

[0078] Specifically, in step S1012, based on the unstable seepage theory under fixed production conditions, production data segments that simultaneously meet the following three conditions are selected for fracture closure identification: the oil well production time is not less than the preset production time threshold (for example, 15 days), and the initial production data segment is not selected; the water content of the oil well is less than the preset water content (for example, 5%); the fluctuation of the daily liquid production of the oil well does not exceed the preset fluctuation range (for example, 30%).

[0079] In step S1013, abnormal points in the production data segment are removed to determine the production dynamic data corresponding to the production data segment.

[0080] Specifically, in step S1013, abnormal points in the production data segment are eliminated according to the following standards: the dynamic data of oil well development in which the single-day well opening time during the development process is less than the preset single-day well opening time threshold (for example, 24 hours) is eliminated, and the dynamic data of oil well development in which the oil well production layer changes (for example, the oil well production layer changes due to the back pressure acid) is eliminated.

[0081] Compared with traditional physical experiments and numerical simulation methods, the present invention can quickly and conveniently identify the closed sections of fractures in ultra-deep fault-controlled fracture-cavity carbonate reservoirs. It has the characteristics of short time and rapid identification (taking less than 1 hour). Moreover, since it identifies fracture closure based on the actual oil reservoir and oil well production dynamic data, it has strong operability and is convenient for on-site application.

[0082] like Figure 1 As shown, in step S102, based on the production dynamic data, the pseudo material balance time, the slope of the liquid production curve of two adjacent valid data points and the intercept of the liquid production curve are calculated to calculate the fracture closure identification parameters corresponding to each data point in the production data segment.

[0083] In one embodiment, in step S102, the fracture closure identification parameters corresponding to each data point in the production data segment are calculated through steps S1021-S1024.

[0084] In step S1021, the pseudo material balance time is calculated based on the cumulative liquid production and the daily liquid production.

[0085] Specifically, in step S1021, the pseudo material balance time is calculated by the following expression (1):

[0086]

[0087] Among them, t ps is the pseudo material equilibrium time, d; L p is the cumulative fluid production, t; q l is the daily liquid production, t / d.

[0088] In step S1022, based on the pseudo material balance time and combined with the daily liquid production, the slope of the liquid production curve between two adjacent valid data points is calculated.

[0089] Specifically, in step S1022, the slope of the liquid production curve is calculated by the following expression (2):

[0090]

[0091] Among them, the subscript i is the valid data point number; k is the slope of the liquid production curve between two adjacent valid data points.

[0092] In step S1023, based on the original formation pressure of the reservoir, the bottom hole flowing pressure, the slope of the liquid production curve, and the pseudo material balance time, the intercept of the liquid production curve between two adjacent valid data points is calculated.

[0093] Specifically, in step S1023, the intercept of the liquid production curve is calculated by the following expression (3):

[0094] IC=p i -p wf -k·t ps (3)

[0095] Where, IC is the intercept of the liquid production curve; p i is the original formation pressure of the reservoir; pwf is the bottom hole flowing pressure; k is the slope of the liquid production curve of two adjacent valid data points; t ps is the pseudo material equilibrium time, d.

[0096] In step S1024, based on the intercept of the liquid production curve and in combination with the daily liquid production, the fracture closure identification parameters corresponding to each data point in the production data segment are calculated.

[0097] Specifically, in step S1024, the crack closure identification parameter is calculated by the following expression (4):

[0098]

[0099] Among them, K c is the crack closure identification parameter; q l is the daily liquid production, t / d.

[0100] like Figure 1 As shown, in step S103, the fracture closure section of the target reservoir is determined according to the fracture closure identification parameters.

[0101] In one embodiment, in step S103, the fracture closure section of the target reservoir is determined through steps S1031-S1032.

[0102] In step S1031, based on the fracture closure identification parameters corresponding to each data point in the production data segment, a fracture closure identification parameter-time curve is drawn with the fracture closure identification parameter as the ordinate and time as the abscissa. Specifically, in step S1031, a fracture closure identification parameter-time curve is drawn with the fracture closure identification parameter as the ordinate and time as the abscissa. Figure 3 Crack closure identification parameter-time curve shown.

[0103] In step S1032, the obvious mutation point or segment in the fracture closure identification parameter-time curve is marked as the fracture closure segment of the target reservoir. Specifically, in step S1032, the abnormally low value segment (there is an obvious mutation point or segment) in the fracture closure identification parameter-time curve is identified as the fracture closure segment.

[0104] The present invention is based on the unstable seepage theory and utilizes the oil well dynamic data that is easily obtained during the development of ultra-deep fault-controlled fracture-cavity carbonate reservoirs. After simple data processing and calculation, the fracture closure identification parameters can be quickly calculated, and the fracture closure identification parameter-time curve can be drawn. The fracture closure can be identified from the abnormally low value segment (with obvious mutation points or segments) in the curve.

[0105] Figure 2 A detailed flow chart of the steps of a method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to another embodiment of the present invention is shown.

[0106] like Figure 2 As shown, in step S201, data is collected. Specifically, the original formation pressure p of the reservoir is collected. i , real-time collection of oil well production date, single-day well opening time hour, daily liquid production q1, water content f w , bottom hole pressure p wf data.

[0107] like Figure 2 As shown, in step S202, the production data segment is selected. Specifically, the production data segment is selected based on the unstable seepage theory under fixed production conditions.

[0108] like Figure 2 As shown, in step S203, the well opening time is long (the well opening production time is not less than 15 days), the water content is low (the water content is less than 5%) and the production is stable (the daily liquid production fluctuation does not exceed 30%). Specifically, it is determined whether the following three conditions are met at the same time: the oil well opening production time is not less than 15 days, and the initial production data segment of the well opening cannot be selected for evaluation; the water content of the oil well is less than 5%; the oil well liquid production is relatively stable, that is, the daily liquid production fluctuation does not exceed 30%. If the judgment result of step S203 is no, then return to step S202, if the judgment result of step S203 is yes, then enter step S204.

[0109] like Figure 2 As shown, in step S204, abnormal points are removed. Specifically, two types of abnormal points are removed, including: removing the dynamic data of oil well development in which the well is opened for less than 24 hours per day during the development process; removing the dynamic data of oil well development in which the production layer has changed due to acid reflow and other factors.

[0110] like Figure 2 As shown, in step S205, the daily well opening time is 24 hours and the oil well has not been subjected to acid pressure reversal, etc., which may cause changes in the production layer. Specifically, if the judgment result of step S205 is no, then return to step S204, and if the judgment result of step S205 is yes, then enter step S206.

[0111] like Figure 2 As shown, in step S206, the pseudo material balance time is calculated. Specifically, the pseudo material balance time of oil well production is calculated using formula (1).

[0112] like Figure 2 As shown, in step S207, the slope of the liquid production curve is calculated. Specifically, the slope of the liquid production curve of two adjacent valid data points of the oil well is calculated using formula (2).

[0113] like Figure 2As shown, in step S208, the intercept of the production curve is calculated. Specifically, the intercept of the production curve of two adjacent valid data points of the oil well is calculated using formula (3).

[0114] like Figure 2 As shown, in step S209, the fracture closure identification parameters are calculated. Specifically, according to the unstable seepage theory:

[0115]

[0116] in, q o is the daily oil production, t / d; μ o is the formation crude oil viscosity, mPa·s; h is the reservoir thickness, m; r e is the supply radius, m; r w is the wellbore radius, m; φ is the porosity; C t is the comprehensive compression coefficient of the formation, MPa -1 .

[0117] The apparent permeability of the reservoir can be obtained as:

[0118] When the water content of the oil well is less than 5%, the daily liquid production is q l Can be approximately equivalent to daily oil production q o ,Right now:

[0119]

[0120] To this end, in step S209, formula (4) may be used to calculate the crack closure identification parameter.

[0121] like Figure 2 As shown, in step S210, the abnormal segment is a crack closure segment. Specifically, the crack closure identification parameter corresponding to each data point in the selected data segment is calculated, and a crack closure identification parameter-time curve is drawn, and the abnormally low value segment (with obvious mutation points or segments) in the curve is identified as a crack closure segment.

[0122] In summary, if Figure 2As shown, first, data collection and selection of production data segments are performed. When the selected production data segment contains a segment with a short well opening time or a water content higher than 5% or unstable production, the production segment data selection step S202 is re-implemented until the selected production data segment simultaneously satisfies the conditions of a long production time, a water content lower than 5% and a stable production, then the abnormal point removal step S204 is implemented; when the selected production data segment contains production data points with a daily production time of less than 24 hours or production data points where the oil well has undergone acid return pressure treatment and caused changes in the production layer, the abnormal point removal step S204 is re-implemented until all daily production data in the production segment meet the conditions that the daily well opening time is 24 hours and the oil well has not undergone acid return pressure treatment and caused changes in the production layer; secondly, the pseudo-material equilibrium time, the slope and intercept of the liquid production curve of two adjacent valid data points are calculated in turn based on the unstable seepage theory; finally, the fracture closure identification parameters are calculated and the fracture closure segment is identified. As shown Figure 3 As shown, the crack closure identification parameters (K c )-time curve. When an abnormally low value segment appears in the curve (there is an obvious mutation point or segment), it can be identified as crack closure.

[0123] The method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs provided by the present invention can also be used in conjunction with a computer-readable storage medium, on which a computer program is stored, and the computer program is executed to run the method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs.

[0124] A computer program can run computer instructions, which include computer program code. The computer program code may be in source code form, object code form, executable file, or some intermediate form.

[0125] Computer-readable storage media may include: any entity or device that can carry computer program code, recording media, USB flash drives, mobile hard disks, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0126] It should be noted that the content contained in computer-readable storage media can be appropriately increased or decreased based on the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, based on legislation and patent practices, computer-readable storage media do not include electrical carrier signals and telecommunications signals.

[0127] According to another aspect of the present invention, there is also provided a device for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, which performs a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs. The device comprises: a production data segment module, a fracture closure identification parameter module, and a fracture closure segment module.

[0128] The production data segment module is used to select the production data segment for fracture closure identification for the target reservoir and determine the production dynamic data corresponding to the production data segment.

[0129] The fracture closure identification parameter module is used to calculate the pseudo-material balance time, the slope of the liquid production curve of two adjacent valid data points, and the intercept of the liquid production curve based on production dynamic data, so as to calculate the fracture closure identification parameters corresponding to each data point in the production data segment.

[0130] The fracture closure section module is used to determine the fracture closure section of the target reservoir based on the fracture closure identification parameters.

[0131] In one embodiment, an ultra-deep fault-controlled fracture-cavity carbonate reservoir Well X is used as an example for illustration. The well has been in production for more than 6 years since it was put into production in September 2015 until June 2022.

[0132] According to step S201: collect the original formation pressure p of the reservoir where the well is located: i , oil well production date, single-day well opening time hour, daily liquid production q l , moisture content f w , bottom hole pressure p wf , where the original reservoir formation pressure p i =87.5MPa.

[0133] According to step S202: select the production data segment for evaluation. From September 30, 2020 to November 26, 2020, the liquid production of Well X was stable between 77-82.2 t / d, relatively stable, water-free, and met the condition of long oil well production time. The production data segment of Well X selected for evaluation is shown in Table 1.

[0134] Table 1 The production data segments of Well X selected for evaluation

[0135]

[0136]

[0137] According to step S204: remove the production data points with a single-day well opening time of less than 24 hours in the production data of Well X. The single-day production time in the selected data segment of the well is 24 hours, so there is no need to remove the abnormal points with insufficient production time. Well X has not yet carried out development measures such as acid fracturing to change the production layer, so there is no need to remove the development dynamic data after the production layer is changed.

[0138] According to step S206: calculate the pseudo material balance time of production of well X, as shown in Table 2.

[0139] Table 2 Calculation results of pseudo material balance time for well X

[0140] date Pseudo-material balance time date Pseudo-material balance time 2020 / 9 / 30 1 2020 / 10 / 29 30.61917098 2020 / 10 / 1 2.00125 2020 / 10 / 30 31.65888457 2020 / 10 / 2 3.00125 2020 / 10 / 31 32.7 2020 / 10 / 3 4.005006258 2020 / 11 / 1 33.28076923 2020 / 10 / 4 5.010025063 2020 / 11 / 2 33.85949367 2020 / 10 / 5 6.016311167 2020 / 11 / 3 34.68891688 2020 / 10 / 6 7.023869347 2020 / 11 / 4 34.96177559 2020 / 10 / 7 8.032704403 2020 / 11 / 5 35.53593179 2020 / 10 / 8 9.042821159 2020 / 11 / 6 36.57926829 2020 / 10 / 9 10.05422446 2020 / 11 / 7 37.49026764 2020 / 10 / 10 11.06691919 2020 / 11 / 8 38.53593179 2020 / 10 / 11 12.08091024 2020 / 11 / 9 39.63003663 2020 / 10 / 12 13.09620253 2020 / 11 / 10 40.67848411 2020 / 10 / 13 14.09620253 2020 / 11 / 11 41.72827417 2020 / 10 / 14 15.11406844 2020 / 11 / 12 42.77941176 2020 / 10 / 15 16.11406844 2020 / 11 / 13 43.88452088 2020 / 10 / 16 17.15501906 2020 / 11 / 14 44.93849938 2020 / 10 / 17 18.17684478 2020 / 11 / 15 46.04932182 2020 / 10 / 18 19.2 2020 / 11 / 16 47.1631644 2020 / 10 / 19 20.24904215 2020 / 11 / 17 48.22153465 2020 / 10 / 20 21.24904215 2020 / 11 / 18 49.82581454 2020 / 10 / 21 22.27621483 2020 / 11 / 19 50.95100503 2020 / 10 / 22 23.27621483 2020 / 11 / 20 51.69625 2020 / 10 / 23 24.33589744 2020 / 11 / 21 52.76095119 2020 / 10 / 24 25.36713736 2020 / 11 / 22 53.82706767 2020 / 10 / 25 26.39974293 2020 / 11 / 23 54.82706767 2020 / 10 / 26 27.43371943 2020 / 11 / 24 56.03396226 2020 / 10 / 27 28.46907216 2020 / 11 / 25 57.17528373 2020 / 10 / 28 29.54263566 2020 / 11 / 26 58.39240506

[0141] According to step S207: the slope of the liquid production curve of two adjacent valid data points is calculated, as shown in Table 3.

[0142] Table 3 Calculation results of the slope of the liquid production curve of two adjacent valid data points in Well X

[0143]

[0144]

[0145] According to step S208: the intercepts of the liquid production curves of two adjacent valid data points are calculated, as shown in Table 4.

[0146] Table 4 Calculation results of intercepts of production curves of two adjacent valid data points of Well X

[0147]

[0148]

[0149] According to step S209: the fracture closure identification parameters of Well X are calculated, as shown in Table 5.

[0150] Table 5 Calculation results of fracture closure identification parameters in Well X

[0151]

[0152] According to step S210: draw the X-well fracture closure identification parameter-time curve, such as Figure 4 Among them, from November 2, 2020 to November 5, 2020, the curve belongs to the abnormally low value section (there is an obvious mutation point) and is identified as the crack closure section.

[0153] In summary, the present invention provides a method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, which has the following advantages over the prior art:

[0154] (1) Compared with traditional physical experiments and numerical simulation methods, the present invention can quickly and conveniently identify the fracture closure section of ultra-deep fault-controlled fracture-cavity carbonate reservoirs, and has the characteristics of short time and rapid identification (taking less than 1 hour). In addition, since the fracture closure is identified based on the actual reservoir oil well production dynamic data, it has strong operability and is convenient for field application.

[0155] (2) Based on the unstable seepage theory, the well dynamic data that is easily obtained during the development of ultra-deep fault-controlled fracture-cavity carbonate reservoirs can be used to quickly calculate the fracture closure identification parameters after simple data processing and calculation, and the fracture closure identification parameter-time curve can be drawn. The fracture closure can be identified from the abnormally low value segment (with obvious mutation points or segments) in the curve.

[0156] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0157] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0158] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0159] Certain terms are used throughout this application document to indicate specific system components. As those skilled in the art will recognize, different names can usually be used to indicate the same components, so this application document is not intended to distinguish those components that are only different in name but not in function. In this application document, the terms "comprise", "include" and "have" are used in an open form, and therefore should be interpreted as meaning "including but not limited to...". In addition, the terms "substantially", "substantially" or "approximately" that may be used in this article relate to the tolerances of the corresponding terms accepted by the industry. The term "coupling" as may be used in this article includes direct coupling and indirect coupling via other components, elements, circuits, or modules, wherein for indirect coupling, the components, elements, circuits, or modules between them do not change the information of the signal but can adjust its current level, voltage level, and / or power level. Inferred coupling (for example, one of the elements is coupled to another element by inference) includes direct and indirect coupling between two elements in the same way as "coupling".

[0160] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0161] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0162] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs, characterized in that: The method comprises: For a target oil reservoir, selecting a production data segment for fracture closure identification, and determining production dynamic data corresponding to the production data segment; Based on the production dynamic data, the pseudo material balance time, the slope of the liquid production curve of two adjacent valid data points and the intercept of the liquid production curve are calculated to calculate the fracture closure identification parameters corresponding to each data point in the production data segment; The fracture closure section of the target reservoir is determined based on the fracture closure identification parameters.

2. A method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs according to claim 1, characterized in that: The production dynamic data corresponding to the production data segment is determined by the following steps: Determine the data type included in the production dynamic data, wherein the production dynamic data includes: original formation pressure of the reservoir, production date of the oil well, single-day well opening time, daily liquid production, water content, and bottom hole flowing pressure; Based on the unstable seepage theory under fixed production conditions, the production data segment for fracture closure identification is selected; Abnormal points in the production data segment are eliminated to determine the production dynamic data corresponding to the production data segment.

3. A method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs according to claim 2, characterized in that: Based on the unstable seepage theory under fixed production conditions, production data segments that simultaneously meet the following three conditions are selected for fracture closure identification: The oil well start-up production time is not less than the preset start-up production time threshold, and the initial production data segment of the well start-up is not selected; The water content of the oil well is less than the preset water content; The fluctuation of daily liquid production of oil wells does not exceed the preset fluctuation range.

4. A method for identifying fracture closure in ultra-deep fault-controlled fracture-cavity carbonate reservoirs according to claim 2 or 3, characterized in that: The outliers in the production data segment are removed by the following criteria: The dynamic development data of oil wells whose single-day well opening time during the development process is less than the preset single-day well opening time threshold are eliminated, and the dynamic development data of oil wells whose oil well production layers have changed are eliminated.

5. A method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to any one of claims 1 to 4, characterized in that: The crack closure identification parameters corresponding to each data point in the production data segment are calculated by the following steps: The pseudo material balance time is calculated based on the cumulative liquid production and the daily liquid production; Based on the pseudo material balance time and the daily liquid production, the slope of the liquid production curve of two adjacent valid data points is calculated; Based on the original formation pressure of the reservoir, the bottom hole flowing pressure, the slope of the liquid production curve, and the pseudo material equilibrium time, the intercept of the liquid production curve between two adjacent valid data points is calculated; Based on the intercept of the liquid production curve and in combination with the daily liquid production, the fracture closure identification parameter corresponding to each data point in the production data segment is calculated.

6. A method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to claim 5, characterized in that: The pseudo-material equilibrium time is calculated by the following expression: The slope of the liquid production curve is calculated by the following expression: Where: t ps is the pseudo material equilibrium time, d; L p is the cumulative fluid production, t; q l is the daily liquid production, t / d; the superscript i is the valid data point number; k is the slope of the liquid production curve between two adjacent valid data points.

7. A method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to claim 5 or 6, characterized in that: The intercept of the liquid production curve is calculated by the following expression: IC=p i -p wf -k·t ps The crack closure identification parameter is calculated by the following expression: Where, IC is the intercept of the liquid production curve; p i is the original formation pressure of the reservoir; p wf is the bottom hole flowing pressure; k is the slope of the liquid production curve of two adjacent valid data points; t ps is the pseudo-material equilibrium time, d; K c is the crack closure identification parameter; q l is the daily liquid production, t / d.

8. A method for identifying fracture closure in ultra-deep fault-controlled fracture-vuggy carbonate reservoirs according to any one of claims 1 to 7, characterized in that: The fracture closure section of the target reservoir is determined by the following steps: According to the fracture closure identification parameter corresponding to each data point in the production data segment, a fracture closure identification parameter-time curve is drawn with the fracture closure identification parameter as the ordinate and time as the abscissa; The obvious mutation point or segment in the fracture closure identification parameter-time curve is marked as the fracture closure segment of the target reservoir.

9. A storage medium, characterized in that: It contains a series of instructions for executing the method steps as claimed in any one of claims 1 to 8.

10. A fracture closure identification device for ultra-deep fault-controlled fracture-cavity carbonate reservoirs, characterized in that: The method according to any one of claims 1 to 8 is performed, wherein the device comprises: A production data segment module, which is used to select a production data segment for fracture closure identification for a target reservoir and determine production dynamic data corresponding to the production data segment; A fracture closure identification parameter module, which is used to calculate the pseudo-material balance time, the slope of the liquid production curve of two adjacent valid data points and the intercept of the liquid production curve based on the production dynamic data, so as to calculate the fracture closure identification parameters corresponding to each data point in the production data segment; The fracture closure section module is used to determine the fracture closure section of the target reservoir according to the fracture closure identification parameters.

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