Well test curve interpretation method and device for fault-karst reservoirs

Abstract

The present invention provides a method for interpreting well test curves of fault-karst reservoirs, which comprises: obtaining pressure recovery well test data of a target object, performing type analysis on the pressure recovery well test curve, and determining the curve type corresponding to the pressure recovery well test curve; determining the fracture / hole combination model to which the target object belongs through the curve type, and performing parameter adjustment and fitting of key parameters in combination with the pressure recovery well test curve to obtain the key parameters of the target object; performing inversion based on the key parameters combined with the inversion formula to obtain application parameters characterizing reservoir characteristics, so as to interpret the reservoir characteristics of the target object. The present invention performs type analysis on the pressure recovery well test curve, determines the fracture / hole combination model based on the determined type, performs fitting and further inversion according to different fracture / hole combination models, and obtains application parameters characterizing reservoir characteristics. The present invention can effectively understand the characteristics of the well test curves produced by complex fault-karst reservoirs, and provide programmatic guidance for subsequent production and development.

Description

Technical Field

[0001] The invention relates to the technical field of oil production, in particular to a method and a device for interpreting well test curves of fault-karst reservoirs. Background Art

[0002] Carbonate reservoirs belong to the paleokarst fracture-cave type. The reservoirs are deeply buried, the reservoir development is controlled by many factors, the heterogeneity is extremely strong, the spatial distribution of the reservoir is discontinuous, the fractures in the reservoir are the main seepage channels, and the fluid is mainly stored in the caves (Li Yang. Identification and quantitative characterization of Ordovician carbonate cave reservoirs in Tahe Oilfield [J]. Journal of China University of Petroleum (Natural Science Edition), 2012, 36(1): 1-4.). Fractures connect caves, and dissolution further transforms fractures, making it difficult to strictly distinguish between fractures and caves, resulting in a very complex flow pattern of fluids in the fracture-cave system (Hu Xiangyang, Quan Lianshun, Qi Deshan, et al. Cave filling characteristics of fracture-cave carbonate reservoirs in Tahe Oilfield [J]. Special Oil and Gas Reservoirs, 2014, 21(1):18.) This shows that the fracture-cave description method of carbonate reservoirs is very different from that of conventional sandstone reservoirs, and the understanding, transformation measures and development of reservoirs are extremely difficult. No theory and technology recognized by the industry have been formed at home and abroad. As a complex fracture-cave reservoir, fault-karst bodies are even more difficult to explain.

[0003] Well testing analysis technology is an important means to evaluate the dynamics of oil and gas reservoirs, completion efficiency and the effectiveness of measures. It plays an important role in understanding the geological characteristics of oil reservoirs and determining the geological parameters of oil reservoirs (Chen Fangfang, Zhang Fuxiang, Deng Xingliang, et al. Numerical well testing model for fracture-cavity reservoirs with wells drilled outside caves [J]. Science and Technology Review, 2015, 33(9): 46-49.). At present, the classical flow theory is the seepage mechanics theory. The classical seepage theory is a flow equation in the sense of statistical average. There is no distinction between bedrock, fractures and caves in the formation, only the porosity and permeability of the formation in different regions are different (Zhu Yi, Cheng Hanlie, Wang Lianshan, et al. Research on well testing methods for selecting wells for water injection and oil replacement in fracture-cavity carbonate rocks [J]. Oil and Gas Well Testing, 2016, 25(3): 4-6.). Therefore, the use of classical seepage theory to study the flow law of fracture-cavity reservoirs is not suitable for describing the structure of fracture-cavity reservoirs.

[0004] Most of the understanding of fracture-cave reservoirs is based on the research field based on multiple medium assumptions (including dual and triple medium models), and then the understanding of well test curve analysis is obtained (Xiong Y, Xiong W, Cai M, et al. Laboratory experiments of well testing for fracture-cave carbonate gas reservoirs [J]. Petroleum, 2016. Yao Jun, Dai Weihua, Wang Zisheng. Research on well test interpretation method of triple medium reservoir with variable wellbore storage [J]. Journal of Petroleum University (Natural Science Edition), 2004, 28 (1): 46-51.). There are many related analyses of this type of well test curves, but they cannot solve the problem of carbonate rock pressure recovery well test analysis in actual oil fields. For example: a large number of complex curve shapes cannot be associated with parameters related to fractures and caves, especially the storage volume ratio, mobility ratio and interface radius of the two zones in the composite reservoir model are not related to fractures and caves.

[0005] How to obtain valuable reservoir information is the basic guarantee for the correct development of fault-karst reservoirs. Therefore, it is necessary to establish a new method to interpret the complex well test curves of fault-karst reservoirs to guide the production and development of fracture-vuggy reservoirs.

[0006] Therefore, the present invention provides a method and device for interpreting well test curves of fault-karst reservoirs. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a method for interpreting well test curves of a fault-karst reservoir, the method comprising the following steps:

[0008] Step 1: Obtain the pressure recovery well test data of the target object, perform type analysis on the pressure recovery well test curve, and determine the curve type corresponding to the pressure recovery well test curve;

[0009] Step 2: Determine the fracture / hole combination model to which the target object belongs through the curve type, and perform key parameter adjustment and fitting in combination with the pressure buildup well test curve to obtain the key parameters of the target object;

[0010] Step three: Based on the key parameters and inversion formulas, inversion is performed to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object.

[0011] According to one embodiment of the present invention, the step one specifically includes the following steps: determining the curve type corresponding to the pressure recovery well test curve by analyzing the distribution characteristics of the pressure points in the pressure recovery well test curve, wherein the curve type includes a smooth type and a fluctuating type.

[0012] According to an embodiment of the present invention, the step 2 specifically includes the following steps:

[0013] Based on the historical well test data, the influence of fractures and caves on the characteristics of pressure recovery well test curves is summarized, and the characteristics of the pressure recovery well test curve when fractures and caves exist alone are determined;

[0014] The pressure drop feature in the pressure recovery well test curve is caused by the cave. When there is a pressure drop funnel feature in the pressure recovery well test curve, it indicates the existence of a cave. The larger the volume of the cave, the larger the pressure drop funnel feature in the pressure recovery well test curve.

[0015] According to an embodiment of the present invention, the step 2 specifically includes the following steps: based on the determined seam / hole combination model of the target object, key parameter adjustment and fitting are performed in combination with mathematical description formulas to obtain the key parameters of the target object.

[0016] According to an embodiment of the present invention, the fracture / hole combination model includes a well-hole model and a well-fracture-hole-fracture-hole model, which correspond to the smooth curve type and the wavy curve type, respectively.

[0017] According to one embodiment of the present invention, the mathematical description of the well-hole model is as follows:

[0018]

[0019] Among them, P wf Indicates the bottom hole pressure, MPa; P v represents cave pressure, MPa; ρ represents crude oil density, kg / m 3 ;v wf Indicates the fluid flow velocity at the junction of the wellbore and the cave, m / s; r v represents the radius of the cave, m; D represents the diameter of the oil pipe, m; v 0 represents the crude oil velocity at the initial moment, m / s; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; t represents time.

[0020] According to one embodiment of the present invention, the mathematical description formula corresponding to the well-fracture-hole-fracture-hole model is as follows:

[0021]

[0022] Among them, P f (x D , t D ) represents the pressure of the fracture-hole system expressed by a dimensionless quantity that varies with the x direction and time in the boundary element method; x DRepresents the dimensionless quantity in the x direction in the boundary element algorithm; t D represents dimensionless time; q D represents dimensionless flow; x′ D represents the derivative of the dimensionless quantity in the x direction in the boundary element algorithm; τ represents the time point definition of the Green's function in free space; y D It represents the dimensionless quantity in the y direction in the boundary element algorithm; M represents the mobility ratio, which is dimensionless; ω represents the storage capacity ratio, %.

[0023] According to one embodiment of the present invention, the key parameters include: original pressure, average pressure, flow coefficient, well storage constant, wellbore skin, mobility ratio, storage volume ratio and flow ratio.

[0024] According to one embodiment of the present invention, the inversion formula is as follows:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] Where V represents the volume of the cave, m 3 ; r v Indicates the radius of the cave, m; h 2 represents the cave height, m; D represents the diameter of the oil pipe, m; Q represents the flow rate or production, m 3 / d; B is the volume coefficient; μ is the fluid viscosity; β is the damping coefficient; ρ is the crude oil density, kg / m 3 ; K represents permeability, md; v 0 Indicates the crude oil velocity at the initial moment, m / s; h 1 represents the wellbore height, m; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; γ represents the Euler constant; Represents reservoir porosity, %; C t Represents the comprehensive compression coefficient; r w represents the wellbore radius; △p represents the pressure difference; q represents the flow rate; V F represents the volume of the fracture system; t represents time; h represents reservoir thickness; A represents flow cross-sectional area, cm 2 ; C A represents the shape factor; P D (L D , t D) represents the dimensionless pressure that varies with distance and time; q v Indicates the cave production, m 3 / d;E i represents the exponential function; L D represents the dimensionless distance from the wellbore to the cave; t D Represents dimensionless time.

[0031] According to another aspect of the present invention, there is also provided a reservoir well test curve interpretation device for a fault-karst body, the device comprising:

[0032] A curve type analysis module, which is used to obtain the pressure recovery well test data of the target object, perform type analysis on the pressure recovery well test curve, and determine the curve type corresponding to the pressure recovery well test curve;

[0033] A fitting module, which is used to determine the fracture / hole combination model to which the target object belongs through the curve type, and to perform key parameter adjustment and fitting in combination with the pressure buildup well test curve to obtain the key parameters of the target object;

[0034] The inversion module is used to perform inversion based on the key parameters combined with the inversion formula to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object.

[0035] The method and device for interpreting well test curves of fault-karst reservoirs provided by the present invention can analyze the type of pressure recovery well test curves, determine the fracture / hole combination model based on the determined type, and then perform fitting and further inversion according to different fracture / hole combination models to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object. The present invention can effectively understand the characteristics of the pressure recovery well test curves generated by complex fault-karst reservoirs, thereby providing programmatic guidance for subsequent production and development.

[0036] 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

[0037] 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:

[0038] Figure 1 A flow chart of a method for interpreting a well test curve of a fault-karst reservoir according to an embodiment of the present invention is shown;

[0039] Figure 2 shows a smooth class curve according to one embodiment of the present invention;

[0040] Figure 3 shows a wave-like curve according to one embodiment of the present invention;

[0041] Figure 4 A diagram showing different characteristics of fractures and caves in a pressure buildup well test curve according to an embodiment of the present invention;

[0042] Figure 5 The fitted pressure buildup well test curve and the actual curve according to one embodiment of the present invention are shown;

[0043] Figure 6 shows a production test graph according to one embodiment of the present invention;

[0044] Figure 7 A schematic diagram showing a similar fault-karst reservoir structure in Shunbei 1-1H area according to an embodiment of the present invention is shown; and

[0045] Figure 8 The structure block diagram of a well test curve interpretation device for a fault-karst reservoir according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0046] 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.

[0047] Figure 1 A flow chart of a method for interpreting well test curves of a fault-karst reservoir according to an embodiment of the present invention is shown.

[0048] like Figure 1 In step S101, the pressure recovery well test data of the target object is obtained, and the type of the pressure recovery well test curve is analyzed to determine the curve type corresponding to the pressure recovery well test curve.

[0049] Specifically, in step S101, the curve type corresponding to the pressure buildup well test curve is determined by analyzing the distribution characteristics of the pressure points in the pressure buildup well test curve, wherein the curve type includes a smooth type and a fluctuating type.

[0050] The characteristics of well test curves in complex fault-karst reservoirs are diverse and no longer present the smooth regular curves of conventional sandstone models. Reasonable preliminary classification based on curve types is the basis for subsequent research. Different from the classification of conventional fracture-cavity well test curves, the classification here is completely based on the curve characteristics of the well test pressure curve itself. The well test pressure curve is a discontinuously measured pressure point. According to the distribution characteristics of the points, it is finally determined that the pressure recovery well test curves of fracture-cavity reservoirs can be divided into two categories: smooth type and fluctuating type (such as Figure 2 and Figure 3 shown).

[0051] Figure 2 A smooth class curve according to one embodiment of the present invention is shown.

[0052] like Figure 2 , the horizontal axis is the dimensionless time, and the vertical axis is the measured and theoretical dimensionless pressure P D ( Figure 2 The above two curves) and the measured and theoretical dimensionless pressure derivative P D '( Figure 2 The two curves below have two concave parts (i.e., pressure drop funnels). When classifying the wave curve and the smooth curve, observe whether the pressure derivative curve is a smooth curve. If it is smooth, it is considered a smooth curve.

[0053] Figure 3 A wave-like curve according to one embodiment of the present invention is shown.

[0054] like Figure 3 , the horizontal axis is the dimensionless time, and the vertical axis is the measured and theoretical dimensionless pressure P D ( Figure 3 The above two curves) and the measured and theoretical dimensionless pressure derivative P D '( Figure 3 The two curves below have two concave curves). When classifying the wave curve and the smooth curve, observe whether the pressure derivative curve has two obvious sharp features. If so, it indicates that the pressure derivative fluctuates greatly, so it is classified as a wave curve.

[0055] like Figure 1 In step S102, the fracture / hole combination model to which the target object belongs is determined by the curve type, and key parameters are adjusted and fitted in combination with the pressure buildup test curve to obtain the key parameters of the target object.

[0056] Specifically, the purpose of key parameter adjustment and fitting is to obtain a curve that is close to the actual curve.

[0057] Furthermore, in step S102, the following steps are specifically included:

[0058] S1021. Based on the historical well test data, summarize the influence of fractures and caves on the characteristics of the pressure recovery well test curve, and determine the characteristics of the pressure recovery well test curve when fractures and caves exist alone.

[0059] S1022. The pressure drop feature in the pressure recovery well test curve is caused by the cave. When there is a pressure drop funnel feature in the pressure recovery well test curve, it indicates the existence of a cave. The larger the cave volume, the larger the pressure drop funnel feature in the pressure recovery well test curve.

[0060] Figure 4 A diagram showing different characteristics of fractures and caves in a pressure buildup well test curve according to an embodiment of the present invention.

[0061] like Figure 4 , the horizontal axis is dimensionless time, Figure 4 The curve in the upper middle is the pressure curve, and the curve in the lower middle is the pressure derivative curve. If the pressure derivative curve exists, Figure 4 The obvious and smooth "depression" feature shown indicates that this is a cave.

[0062] like Figure 4 As shown in the figure, in the fracture-vuggy reservoir combination, the fractures serve as the connecting channels of the caves, and their influence on the pressure curve characteristics can be ignored.

[0063] In addition, step S102 also includes: based on the determined seam / hole combination model of the target object, key parameter adjustment and fitting are performed in combination with mathematical description formulas to obtain key parameters of the target object.

[0064] According to the understanding described in step S1022, the influence of the fracture is ignored, and only its connectivity is considered, which is mainly divided into two characteristic models: well-hole model and well-fracture-hole-fracture-hole. Specifically, the fracture / hole combination model includes the well-hole model and the well-fracture-hole-fracture-hole model, which correspond to the smooth curve type and the wave curve type respectively.

[0065] Specifically, the mathematical description of the well-hole model is as follows:

[0066]

[0067] Among them, P wf Indicates the bottom hole pressure, MPa; P v represents cave pressure, MPa; ρ represents crude oil density, kg / m 3 ;v wf Indicates the fluid flow velocity at the junction of the wellbore and the cave, m / s; r v represents the radius of the cave, m; D represents the diameter of the oil pipe, m; v 0represents the crude oil velocity at the initial moment, m / s; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; t represents time.

[0068] Specifically, the mathematical description of the well-fracture-hole-fracture-hole model is as follows:

[0069]

[0070] Among them, P f (x D , t D ) represents the pressure of the fracture-hole system expressed by a dimensionless quantity that varies with the x direction and time in the boundary element method; x D Represents the dimensionless quantity in the x direction in the boundary element algorithm; t D represents dimensionless time; q D represents dimensionless flow; x′ D represents the derivative of the dimensionless quantity in the x direction in the boundary element algorithm; τ represents the time point definition of the Green's function in free space; y D It represents the dimensionless quantity in the y direction in the boundary element algorithm; M represents the mobility ratio, which is dimensionless; ω represents the storage capacity ratio, %.

[0071] Specifically, the key parameters include: original pressure, average pressure, flow coefficient, well storage constant, wellbore skin, mobility ratio, storage volume ratio and flow ratio.

[0072] Figure 5 The fitted pressure buildup test curve and the actual curve according to one embodiment of the present invention are shown.

[0073] like Figure 5 , the horizontal axis is the dimensionless time, and the vertical axis is the measured and theoretical dimensionless pressure P D ( Figure 5 The above two curves) and the measured and theoretical dimensionless pressure derivative P D '( Figure 5 The two curves below have two concave curves).

[0074] like Figure 1 In step S103, inversion is performed based on the key parameters combined with the inversion formula to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object.

[0075] Specifically, the inversion formula is as follows:

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] Where V represents the volume of the cave, m 3 ; r v Indicates the radius of the cave, m; h 2 represents the cave height, m; D represents the diameter of the oil pipe, m; Q represents the flow rate or production, m 3 / d; B is the volume coefficient; μ is the fluid viscosity; β is the damping coefficient; ρ is the crude oil density, kg / m 3 ; K represents permeability, md; v 0 Indicates the crude oil velocity at the initial moment, m / s; h 1 represents the wellbore height, m; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; γ represents the Euler constant; Represents reservoir porosity, %; C t Represents the comprehensive compression coefficient; r w represents the wellbore radius; △p represents the pressure difference; q represents the flow rate; V F represents the volume of the fracture system; t represents time; h represents reservoir thickness; A represents flow cross-sectional area, cm 2 ; C A represents the shape factor; P D (L D , t D ) represents the dimensionless pressure that varies with distance and time; q v Indicates the cave production, m 3 / d;E i represents the exponential function; L D represents the dimensionless distance from the wellbore to the cave; t D represents dimensionless time, t c represents the material balance time; p i represents the original formation pressure; p wf Indicates the bottom hole flowing pressure; N p Indicates cumulative production.

[0082] Through the inversion formula, three application parameters that characterize reservoir characteristics can be inverted under the conditions of known other parameters, including original pressure, average pressure, flow coefficient, well storage constant, wellbore skin, mobility ratio, storage volume ratio, and flow ratio: ① cavity volume V, ② fracture volume V F ③ Hole distance L D , in order to infer where the caves are located in the reservoir and how big the caves are.

[0083] L D It represents the dimensionless distance from the wellbore to the cave. Through the continuous fitting of other parameters of the model, it is equivalent to the parameters in the above expression (except L D All of them are known, only L D is unknown, so the hole distance can be obtained by solving.

[0084] Specifically, the application parameters characterizing reservoir characteristics may include: cave volume, fracture volume, and cave distance.

[0085] Aiming at the complex pressure recovery well test curve characteristics generated in the well testing process due to the unique fracture-cavity combination of fracture-cavity oil reservoirs, the present invention can effectively understand the pressure recovery well test curve characteristics generated by complex fault-karst oil reservoirs, thereby providing programmatic guidance for subsequent production and development.

[0086] In one embodiment, the target area is determined to be Shunbei 1-1H, as shown in Table 1, which shows basic parameters of the target area.

[0087] Table 1 Basic parameters of the target area

[0088]

[0089]

[0090] 1) The actual records are as follows:

[0091] June 16, 2016:

[0092] 12:10 8mm-12mm-open drainage spray is used, and the oil pressure is 12.12-0.75MPa;

[0093] 15:30 Replace the 12mm oil nozzle, oil pressure 0.75-0.8MPa, sleeve pressure 16.83-16.87;

[0094] At 15:32, the gas entering the separator at the tank mouth was ignited successfully, and the flame length was 0.5-1m.

[0095] Afterwards, the well was opened and self-flowing with a 12mm-8mm-5mm nozzle. The oil pressure was stable at 31.3MPa. When the nozzle was 5mm, the hourly liquid production was 7.0m 3 / h, hourly oil production 6.8m 3 / h, daily gas production 48000m 3 / d, before the well was shut down at 12:00 on June 23, the accumulated liquid volume was 1270.5m 3 , total oil volume 978.12m 3 , accumulated gas 32.11×104m 3 The estimated production pressure difference of 5mm is 8.4MPa.

[0096] Among them, the conclusion of the oil test is the oil layer.

[0097] In July 2016, a wire breakage accident occurred during interference well test monitoring, resulting in the failure of the pressure measurement operation. The wire was subsequently removed from the wellbore.

[0098] Subsequently, three static pressure and static temperature tests were carried out on August 8, October 30, and November 12. The actual static pressure was 151.41℃ / 82.86M Pa / 7100m, which was converted to 159.80℃ / 85.29M Pa / 7569.47m after being converted to the middle depth of the reservoir. The pressure coefficient was calculated to be 1.154 and the static temperature gradient was 2.11℃ / 100m.

[0099] On November 16, the well was opened for system testing. The oil pressure before opening the well was 37.27MPa. Figure 6 A tubing test production diagram is shown. Figure 6 From top to bottom in the figure are the oil pressure curve, nozzle curve, casing pressure curve, daily gas production curve, hourly liquid production curve and hourly oil production curve.

[0100] The curve characteristics obtained through pressure recovery test are mainly as follows: Figure 2 The smooth class curve shown.

[0101] 2) By analyzing the influence of fractures and caves on the characteristics of pressure recovery curve, the pressure reduction characteristics in the recovery pressure well test curve are caused by caves, not fractures; the larger and more caves there are, the deeper and larger the "pressure drop funnel", such as Figure 4 As shown in the figure, in the fracture-vuggy reservoir combination, the fractures serve as the connecting channels of the caves, and their influence on the pressure curve characteristics can be ignored.

[0102] 3) Based on step 2), the fracture / hole related combination model is determined to be a well-hole model, and the corresponding mathematical description formula is used for calculation.

[0103] 4) Perform key parameter adjustment and fitting to obtain a curve that is close to the actual curve, see Figure 5 ;

[0104] 5) Based on the approximate curve obtained in step 4), combined with the correlation coefficient actually obtained in the mine, the inversion formula is further used to invert the application parameters that can characterize the reservoir characteristics, as shown in Table 2.

[0105] The three application parameters characterizing the reservoir characteristics were calculated through Table 2, which are: ① The cave volume is 51202.05m 3 ,②The crack volume is 1.718×10 6 m 3 , the distance between the third hole is 148.908m. Based on this type of data, the reservoir characteristics can be determined and a schematic diagram of the reservoir characteristics can be drawn. Figure 7 The pressure derivative curve has two concave areas, which indicates that there are two caves.

[0106] Table 2 Application parameters obtained from the mine

[0107]

[0108]

[0109] Figure 8 The structure block diagram of a well test curve interpretation device for a fault-karst reservoir according to an embodiment of the present invention is shown.

[0110] like Figure 8 As shown, the device 800 includes a curve type analysis module 801 , a fitting module 802 and an inversion module 803 .

[0111] The curve type analysis module 801 is used to obtain the pressure recovery well test data of the target object, perform type analysis on the pressure recovery well test curve, and determine the curve type corresponding to the pressure recovery well test curve.

[0112] The fitting module 802 is used to determine the fracture / hole combination model to which the target object belongs through the curve type, and to perform key parameter adjustment and fitting in combination with the pressure buildup well test curve to obtain the key parameters of the target object.

[0113] The inversion module 803 is used to perform inversion based on key parameters combined with inversion formulas to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object.

[0114] In summary, the method and device for interpreting well test curves of fault-karst reservoirs provided by the present invention can analyze the type of pressure recovery well test curves, determine the fracture / hole combination model based on the determined type, and then fit and further invert according to different fracture / hole combination models to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object. The present invention can effectively understand the characteristics of the pressure recovery well test curves produced by complex fault-karst reservoirs, thereby providing programmatic guidance for subsequent production and development.

[0115] 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.

[0116] 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.

[0117] 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 interpreting well test curves of fault-karst reservoirs, characterized in that: The method comprises the following steps: Step 1: Obtain the pressure recovery well test data of the target object, perform type analysis on the pressure recovery well test curve, and determine the curve type corresponding to the pressure recovery well test curve; Step 2: Determine the fracture / hole combination model to which the target object belongs through the curve type, and perform key parameter adjustment and fitting in combination with the pressure buildup well test curve to obtain the key parameters of the target object; Step 3: Based on the key parameters and the inversion formula, inversion is performed to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object, wherein the application parameters include the cave volume V, the volume of the fracture system V F , dimensionless distance L from the wellbore to the cave D ; The inversion formula is as follows: Where V represents the volume of the cave, m 3 ; r v represents the radius of the cave, m; h2 represents the height of the cave, m; D represents the diameter of the oil pipe, m; Q represents the flow rate or production, m 3 / d; B is the volume coefficient; μ is the fluid viscosity; β is the damping coefficient; ρ is the crude oil density, kg / m 3 ; K represents permeability, md; v0 represents the crude oil velocity at the initial moment, m / s; h1 represents the wellbore height, m; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; γ represents the Euler constant; Represents reservoir porosity, %; C t Represents the comprehensive compression coefficient; r w represents the wellbore radius; △p represents the pressure difference; q represents the flow rate; V F represents the volume of the fracture system; t represents time; h represents reservoir thickness; A represents flow cross-sectional area, cm 2 ; C A represents the shape factor; P D (L D , t D ) represents the dimensionless pressure that varies with distance and time; q v Indicates the cave production, m 3 / d;E i represents the exponential function; L D represents the dimensionless distance from the wellbore to the cave; t D Represents dimensionless time.

2. The method according to claim 1, characterized in that The step one specifically includes the following steps: determining the curve type corresponding to the pressure recovery well test curve by analyzing the distribution characteristics of the pressure points in the pressure recovery well test curve, wherein the curve type includes a smooth type and a fluctuating type.

3. The method according to claim 1, characterized in that The step 2 specifically includes the following steps: Based on the historical well test data, the influence of fractures and caves on the characteristics of pressure recovery well test curves is summarized, and the characteristics of the pressure recovery well test curve when fractures and caves exist alone are determined; The pressure drop feature in the pressure recovery well test curve is caused by the cave. When there is a pressure drop funnel feature in the pressure recovery well test curve, it indicates the existence of a cave. The larger the volume of the cave, the larger the pressure drop funnel feature in the pressure recovery well test curve.

4. The method according to claim 2, characterized in that The step 2 specifically includes the following steps: based on the determined seam / hole combination model of the target object, key parameter adjustment and fitting are performed in combination with mathematical description formulas to obtain the key parameters of the target object.

5. The method according to claim 4, characterized in that The fracture / hole combination model includes a well-hole model and a well-fracture-hole-fracture-hole model, which correspond to the smooth curve type and the wave curve type respectively.

6. The method according to claim 5, characterized in that The mathematical description of the well-hole model is as follows: Among them, P wf Indicates the bottom hole pressure, MPa; P v represents cave pressure, MPa; ρ represents crude oil density, kg / m 3 ;v wf Indicates the fluid flow velocity at the junction of the wellbore and the cave, m / s; r v represents the radius of the cave, m; D represents the diameter of the oil pipe, m; v0 represents the crude oil velocity at the initial moment, m / s; C represents the wave velocity of the pipeline and fluid system, m / s; C v represents the cave storage constant; t represents time.

7. The method according to claim 5, characterized in that The mathematical description of the well-fracture-hole-fracture-hole model is as follows: Among them, P f (x D , t D ) represents the pressure of the fracture-hole system expressed by a dimensionless quantity that varies with the x direction and time in the boundary element method; x D Represents the dimensionless quantity in the x direction in the boundary element algorithm; t D represents dimensionless time; q D represents dimensionless flow; x′ D represents the derivative of the dimensionless quantity in the x direction in the boundary element algorithm; τ represents the time point definition of the Green's function in free space; y D It represents the dimensionless quantity in the y direction in the boundary element algorithm; M represents the mobility ratio, dimensionless; ω represents the storage capacity ratio, %.

8. The method according to any one of claims 1 to 7, characterized in that The key parameters include: original pressure, average pressure, flow coefficient, well storage constant, wellbore skin, mobility ratio, storage volume ratio and flow ratio.

9. A well test curve interpretation device for fault-karst reservoirs, characterized in that: Execute the method according to any one of claims 1 to 8, wherein the device comprises: A curve type analysis module, which is used to obtain the pressure recovery well test data of the target object, perform type analysis on the pressure recovery well test curve, and determine the curve type corresponding to the pressure recovery well test curve; A fitting module, which is used to determine the fracture / hole combination model to which the target object belongs through the curve type, and to perform key parameter adjustment and fitting in combination with the pressure buildup well test curve to obtain the key parameters of the target object; The inversion module is used to perform inversion based on the key parameters combined with the inversion formula to obtain application parameters that characterize reservoir characteristics, so as to interpret the reservoir characteristics of the target object.

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