Well test curve interpretation method and device for complex fracture combination reservoir

Abstract

The present invention provides a method for interpreting a well test curve for a complex fracture combination reservoir, which comprises: step one: based on the production data of the target area, determining the application construction method of the target area, performing a pressure recovery well test on the target area, and obtaining a well test curve of the target area; step two: adjusting parameters and curve fitting through a mathematical expression constructed to describe the fracture capacity and morphological characteristics, and obtaining a fitting curve that fits the well test curve; step three: based on the fitting curve, inverting the application parameters that characterize the fracture characteristics, combining with the morphology of the well test curve, and obtaining fracture volume information of a complex fracture combination reservoir including fracturing fractures and reservoir fractures. The present invention can interpret the well test curve of a complex fracture combination reservoir, and can recognize the characteristics of the well test curve generated by a complex fracture-cavity oil reservoir, thereby providing 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 well test curve interpretation method and device for complex fracture combination reservoirs. Background Art

[0002] Fractured reservoirs account for more than 50% of the world's oil and gas reserves and are a key area for future oil and gas development. my country also has a considerable number of fractured reservoirs: such as the fractured buried hill gas reservoirs in North China, the fractured-cave carbonate oil and gas reservoirs in Sichuan, the mudstone fractured gas reservoirs in Shengli Oilfield, the Ordovician fractured-cave stratigraphic lithologic oil and gas reservoirs in the Tarim Basin, and the fractured-cave buried hill gas reservoirs in Dagang, all of which are typical fractured oil and gas reservoirs, and they also occupy an important position in my country's oil and gas production. There are often two difficulties in the transformation of this type of reservoir: ① The drilling and completion working fluid is very easy to cause deep contamination along the natural fractures, especially the near-well contamination is serious, which greatly reduces the flow capacity of the fluid in the fracture system. ② For the natural fractures of the pre-developed reservoir, it is easy to form a fracture network system with multiple fractures under the effects of stress, acid corrosion, etc. during fracturing construction, resulting in a large amount of fracturing fluid loss, which greatly increases the difficulty of construction.

[0003] The biggest difference between fractured reservoirs and conventional porous medium reservoirs is that fractured reservoirs have two pore systems with completely different seepage laws. The pores in the reservoir as a whole are very different and the distribution is discontinuous. In fractured oil and gas reservoirs, previous research results usually regard the matrix system as the main storage space and also participate in seepage (shown as cross-flow in the established model); while the fracture system is the main flow channel. However, the further transformation of fractures by acidification and dissolution makes it difficult to strictly distinguish between large-scale fractures and small-scale caves, resulting in a very complex flow pattern of fluids in the fracture-cavity system (Hu Xiangyang, Quan Lianshun, Qi Deshan, et al. Cave filling characteristics of fracture-cavity carbonate reservoirs in Tahe Oilfield [J]. Special Oil and Gas Reservoirs, 2014, 21(1):18.). Whether it is the naturally developed fractures in the reservoir or the artificial fractures formed by later transformation, the previous models are mostly homogeneous reservoir analytical models based on radial flow, which cannot meet the well testing requirements of fractured oil and gas reservoirs.

[0004] The excellent oil storage space and flow channels of fracture-cavity reservoirs make their production and development mainly based on self-flow. However, the spatial connectivity of the fracture reservoirs corresponding to some well locations is poor, and large-scale fracturing operations are also applied to connect the reservoirs; however, such artificial fractures can be clearly described and controlled in the construction design, but once they communicate with the original natural fractures in the reservoir, the flow channels will be greatly changed, which also brings great troubles to the well testing work. Therefore, it is of great significance to effectively understand the well testing curve characteristics presented by such complex fractures formed by artificial fractures and original formation fractures.

[0005] Therefore, the present invention provides a method and device for interpreting well test curves for complex fracture combination reservoirs. Summary of the invention

[0006] To solve the above problems, the present invention provides a well test curve interpretation method for a complex fracture combination reservoir, the method comprising the following steps:

[0007] Step 1: Based on the production data of the target area, determine the application construction method of the target area, perform a pressure recovery well test on the target area, and obtain the well test curve of the target area;

[0008] Step 2: By constructing a mathematical expression for describing fracture capacity and morphological characteristics, parameter adjustment and curve fitting are performed to obtain a fitting curve that fits the well test curve;

[0009] Step 3: Based on the fitting curve, invert the application parameters characterizing the fracture characteristics, and combine them with the shape of the well test curve to obtain the fracture volume information of the complex fracture combination reservoir including fracturing fractures and reservoir fractures.

[0010] According to one embodiment of the present invention, the step 1 specifically includes the following steps:

[0011] Determine characteristic oil and gas wells in the target area;

[0012] Applying segmented or large-scale fracturing technology to the characteristic oil and gas wells to determine the fracture characteristics of the fracturing fractures;

[0013] A pressure recovery well test is performed on the characteristic oil and gas well to obtain the well test curve of the characteristic oil and gas well.

[0014] According to one embodiment of the present invention, the characteristic oil and gas wells include: some marginal wells in the development of fracture-cavity type oil reservoirs and oil and gas wells in which only some fractures are developed in the reservoir.

[0015] According to an embodiment of the present invention, the fracture characteristics include: the length of the hydraulic fracture, the width of the hydraulic fracture and the height of the hydraulic fracture.

[0016] According to an embodiment of the present invention, the step 2 specifically includes the following steps: constructing the mathematical expression for describing the fracture capacity and morphological characteristics, and analyzing to obtain the flow state influencing parameters that affect the flow state.

[0017] According to an embodiment of the present invention, the flow state influencing parameters include fracture volume and comprehensive compressibility coefficient.

[0018] According to one embodiment of the present invention, the mathematical expression used to describe the crack capacity and morphological characteristics is as follows:

[0019]

[0020] Among them, △p represents the pressure difference; q represents the flow rate; V F represents the crack volume; C t represents the comprehensive compression coefficient; t represents time; μ represents fluid viscosity; B represents volume coefficient; K represents permeability; h represents reservoir thickness; A represents flow channel cross-sectional area; C represents the cross-sectional area of ​​the flow channel; A represents the shape factor; γ represents the Euler constant; r w Represents the wellbore radius.

[0021] According to an embodiment of the present invention, the step 2 specifically includes the following steps:

[0022] Calculate basic parameters that characterize fracture flow capacity and extension morphology, the basic parameters including reservoir parameters, fluid parameters and wellbore parameters;

[0023] The basic parameters are adjusted one by one in a preset order, and curve fitting is performed to obtain the fitting curve that fits the well test curve.

[0024] According to one embodiment of the present invention, step three specifically includes the following steps: inverting to obtain the total volume of the cracks in the target area, combining the calculated crack volume of the characteristic oil and gas wells to obtain the crack volume of the reservoir cracks in the target area.

[0025] According to another aspect of the present invention, a well test curve interpretation device for a complex fracture combination reservoir is provided, the device comprising:

[0026] A well testing module, which is used to determine the application construction method of the target area based on the production data of the target area, perform a pressure recovery well test on the target area, and obtain a well testing curve of the target area;

[0027] A fitting module, which is used to adjust parameters and perform curve fitting through a mathematical expression constructed to describe fracture capacity and morphological characteristics, so as to obtain a fitting curve that fits the well test curve;

[0028] The inversion module is used to invert application parameters characterizing fracture characteristics based on the fitting curve, and combine them with the shape of the well test curve to obtain fracture volume information of a complex fracture combination reservoir including hydraulic fractures and reservoir fractures.

[0029] The well test curve interpretation method and device for complex fracture combination reservoirs provided by the present invention can interpret the well test curves of complex fracture combination reservoirs, and can understand the well test curve characteristics produced by complex fracture-cavity oil reservoirs, thereby providing programmatic guidance for subsequent production and development.

[0030] 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

[0031] 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:

[0032] Figure 1 A flow chart of a well test curve interpretation method for a complex fracture combination reservoir according to an embodiment of the present invention is shown;

[0033] Figure 2 A well test graph according to an embodiment of the present invention is shown;

[0034] Figure 3 A fitting curve and a well test curve diagram according to an embodiment of the present invention are shown;

[0035] Figure 4a-4b A fracturing operation diagram according to an embodiment of the present invention is shown; and

[0036] Figure 5 A structural block diagram of a well test curve interpretation device for a complex fracture combination reservoir according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] 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.

[0038] Figure 1 A flow chart of a well test curve interpretation method for a complex fracture combination reservoir according to an embodiment of the present invention is shown.

[0039] like Figure 1 In step S101, based on the production data of the target area, the application construction method of the target area is determined, and a pressure recovery well test is performed on the target area to obtain a well test curve of the target area.

[0040] Specifically, the purpose of determining the application construction method of the target area based on the production data of the target area is: to analyze the possible problems of the oil wells according to the production data, such as whether there is water production and the speed of energy decline, so as to select the corresponding technology to monitor the oil and gas wells, such as well logging, well testing, etc.

[0041] Furthermore, step S101 specifically includes the following steps:

[0042] S1011. Determine characteristic oil and gas wells in the target area.

[0043] Generally speaking, characteristic oil and gas wells include: some marginal wells in the development of fracture-cavity type oil reservoirs and oil and gas wells in which only some fractures are developed in the reservoir.

[0044] S1012. Apply segmented or large-scale fracturing technology to characteristic oil and gas wells to determine the fracture characteristics of the fracturing fractures.

[0045] Generally speaking, fracture characteristics include: the length of the fracture, the width of the fracture, and the height of the fracture.

[0046] S1013. Perform pressure recovery well testing on characteristic oil and gas wells in the target area to obtain well testing curves of the characteristic oil and gas wells.

[0047] like Figure 2 As shown, Figure 2 The horizontal axis is the dimensionless time, and the vertical axis is the dimensionless pressure curve and the dimensionless pressure derivative curve (the upper curve is the pressure curve, and the lower curve is the pressure derivative curve). Figure 2 In the figure, the pressure curve is rising continuously, indicating that the formation pressure is gradually recovering, and the pressure derivative curve represents the rate of change of the pressure curve over time.

[0048] Specifically, characteristic oil and gas wells have poor formation supply or poor fluid flow capacity, resulting in production rates below 10-20m 3 / d (Conventional oil and gas well production is usually 70m 3 / d or more). In order to improve its low production characteristics, segmented or large-scale fracturing technology is used to determine the fracture characteristics of fracturing, that is, the length, width and height of the artificially created fracturing fractures, and pressure recovery well test methods are used to obtain the well test curves of characteristic oil and gas wells.

[0049] like Figure 1 In step S102, the parameters are adjusted and the curve is fitted by using the mathematical expression constructed to describe the fracture capacity and morphological characteristics, so as to obtain a fitting curve that fits the well test curve.

[0050] Figure 3 The relationship between the actual curve and the fitting curve is shown, with the horizontal axis being time (hr) and the vertical axis being pressure (MPa). Figure 3 As shown in the figure, the fitted pressure curve and the fitted pressure derivative curve have a good coincidence rate with the actual pressure curve and the actual pressure derivative curve. It is believed that the fitting accuracy is relatively high, and the fracture volume parameter can be obtained by the fitting curve.

[0051] Furthermore, step S102 specifically includes the following steps: constructing the mathematical expression for describing the fracture capacity and morphological characteristics, and analyzing to obtain the flow state influencing parameters that affect the flow state.

[0052] Specifically, the flow influencing parameters include fracture volume and comprehensive compressibility.

[0053] Specifically, the mathematical expressions used to describe the crack capacity and morphological characteristics are as follows:

[0054]

[0055] Among them, △p represents the pressure difference; q represents the flow rate; V F represents the crack volume; C t represents the comprehensive compression coefficient; t represents time; μ represents fluid viscosity; B represents volume coefficient; K represents permeability; h represents reservoir thickness; A represents flow channel cross-sectional area; C represents the cross-sectional area of ​​the flow channel; A represents the shape factor; γ represents the Euler constant; r w Represents the wellbore radius.

[0056] Furthermore, step S102 also includes the following steps:

[0057] S1021. Calculate basic parameters that characterize fracture flow capacity and extension morphology. The basic parameters include reservoir parameters, fluid parameters, and wellbore parameters.

[0058] Specifically, the basic parameters include: pressure difference △p, flow rate q, volume V of the fracture system F , comprehensive compression coefficient C t , time t, fluid viscosity μ, volume coefficient B, permeability K, reservoir thickness h, flow channel cross-sectional area A, shape factor C A , Euler constant γ, wellbore radius r w .

[0059] S1022. Adjust basic parameters one by one according to a preset sequence and perform curve fitting to obtain a fitting curve that fits the well test curve.

[0060] Specifically, the mathematical expression used to describe the fracture capacity and morphological characteristics involves multiple basic parameters. When adjusting the parameters one by one, they need to be input in advance, and the corresponding well testing mode, such as the well-hole model or the well-fracture-hole model, is selected. Then, the shape of the curve is gradually adjusted so that the fitting pressure curve and the actual pressure curve, and the fitting pressure derivative curve and the actual pressure derivative curve coincide within the allowable error range. The results of parameters such as fracture volume and permeability can be obtained.

[0061] like Figure 1In step S103, based on the fitting curve, application parameters characterizing the fracture characteristics are inverted and combined with the shape of the well test curve to obtain fracture volume information of a complex fracture combination reservoir including hydraulic fractures and reservoir fractures.

[0062] Furthermore, step S103 specifically includes the following steps: inverting to obtain the total volume of the fractures in the target area, combining the calculated fracture volume of the characteristic oil and gas wells, to obtain the fracture volume of the reservoir fractures in the target area.

[0063] Specifically, the complex fracture combination reservoir referred to in the present invention includes hydraulic fractures and reservoir fractures. Hydraulic fractures refer to artificial hydraulic fractures created after segmentation or large-scale fracturing technology is applied to characteristic oil and gas wells. After the total volume of fractures in the target area is obtained by inversion, the fracture volume of the characteristic oil and gas wells calculated is subtracted to obtain the fracture volume of the reservoir fractures.

[0064] In the fracture-cavity oil reservoir after large-scale fracturing and acidizing, the fracturing fractures connect the original large fractures in the reservoir, forming a complex fracture reservoir combination structure, which causes the well test curve generated during the well test to change seriously, making it difficult to effectively remove the blockage. The present invention effectively recognizes the well test curve characteristics of such complex fractures formed by the combination of fracturing fractures and original formation fractures, thereby providing programmatic guidance for subsequent production and development.

[0065] In one embodiment, Shunbei area is taken as the target area, and SHB2 well is taken as an example to interpret the well test curves of the complex fracture combination reservoir.

[0066] Well SHB2 is located at 207°39′46.7″ southwest of Well Shunbei 1, with a horizontal distance of 7.54km; and at 89°57′26.1″ northeast of Well Shunbei 1-1, with a horizontal distance of 2.68km.

[0067] The well was opened for testing on October 7, 2016, with a total output of 7.86m 3 , cumulative oil output 0.948m 3 , liquid density 1.01g / m 3 , crude oil density 0.788g / m 3 , trace gas.

[0068] There was no liquid or gas after 10:30 on October 9. The conclusion of the oil test was: oil was seen and the liquid supply was insufficient.

[0069] On October 18, fiber temporary plugging and acid fracturing were carried out twice on the SHB2 well, with a total injection volume of 2870m 3 , add temporary plugging fiber 950Kg, fiber particles 50Kg, maximum pressure 130.7MPa, maximum construction displacement 6.5m 3 / min, the temporary plugging and segmented acid fracturing was a complete success.

[0070] After 1261.2t of flowback, oil was observed at 17:00 on October 21, and the water content gradually decreased, with the oil specific gravity of 0.8265. Before shut-in (11.1), the liquid production was 24.3t / d, the water content was 70.74%, and the daily gas production was 2280m 3 / d, gas-oil ratio 321m 3 / m 3 ; Cumulative liquid production 2372.7m 3 , flowback rate 82.7%, stage oil production 113m 3 , gas production 6.1×104m 3 Well test curve Figure 2 shown.

[0071] Analysis of the early temporary plugging acid fracturing wells showed that the temporary plugging pressure was above 7MPa, and most wells were successfully plugged. The temporary plugging pressure of SHB2 well was 9.9MPa, and the temporary plugging effect was good. Figure 4a and Figure 4b .

[0072] Apply the mathematical expressions used to describe the fracture capacity and morphological characteristics, combined with the actual data of the mine, see Table 1, adjust the parameters one by one for fitting, and obtain Figure 3 The fitting curve is shown.

[0073] Table 1 Actual data of the mine

[0074]

[0075]

[0076] The total volume of the fracture determined by inversion calculation is 21×10 4 m 3 , compared with the artificial cracks 3×10 4 m 3 (fracturing cracks), the volume of the reservoir fracture is 18×10 4 m 3 .

[0077] Figure 5 A structural block diagram of a well test curve interpretation device for a complex fracture combination reservoir according to an embodiment of the present invention is shown.

[0078] like Figure 5 As shown, the interpretation device 500 includes a well testing module 501 , a fitting module 502 and an inversion module 503 .

[0079] The well testing module 501 is used to determine the application construction method of the target area based on the production data of the target area, perform a pressure recovery well testing on the target area, and obtain a well testing curve of the target area.

[0080] The fitting module 502 is used to adjust parameters and perform curve fitting through a mathematical expression constructed to describe fracture capacity and morphological characteristics, so as to obtain a fitting curve that fits the well test curve.

[0081] The inversion module 503 is used to invert application parameters characterizing fracture characteristics based on the fitting curve, and combine it with the shape of the well test curve to obtain fracture volume information of a complex fracture combination reservoir including hydraulic fractures and reservoir fractures.

[0082] In summary, the well test curve interpretation method and device for complex fracture combination reservoirs provided by the present invention can interpret the well test curves of complex fracture combination reservoirs, and can understand the characteristics of the well test curves produced by complex fracture-cavity oil reservoirs, thereby providing programmatic guidance for subsequent production and development.

[0083] 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.

[0084] 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.

[0085] 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 well test curve interpretation method for complex fracture combination reservoirs, characterized in that: The method comprises the following steps: Step 1: Based on the production data of the target area, determine the application construction method of the target area, perform a pressure recovery well test on the target area, and obtain the well test curve of the target area; Step 2: By constructing a mathematical expression for describing fracture capacity and morphological characteristics, parameter adjustment and curve fitting are performed to obtain a fitting curve that fits the well test curve; Step 3: Based on the fitting curve, invert the application parameters characterizing the fracture characteristics, and combine them with the shape of the well test curve to obtain the fracture volume information of the complex fracture combination reservoir including fracturing fractures and reservoir fractures; The mathematical expressions used to describe the fracture capacity and morphological characteristics are as follows: Among them, △p represents the pressure difference; q represents the flow rate; V F represents the crack volume; C t represents the comprehensive compression coefficient; t represents time; μ represents fluid viscosity; B represents volume coefficient; K represents permeability; h represents reservoir thickness; A represents flow channel cross-sectional area; C represents the cross-sectional area of ​​the flow channel; A represents the shape factor; γ represents the Euler constant; r w Represents the radius of the wellbore; The step 2 specifically includes the following steps: calculating basic parameters characterizing the flow capacity and extension morphology of the fracture, the basic parameters including reservoir parameters, fluid parameters and wellbore parameters; adjusting the basic parameters one by one in a preset order, performing curve fitting, so as to obtain the fitting curve that fits the well test curve; The fitting curve is obtained by the following steps: the mathematical expression for describing the fracture capacity and morphological characteristics involves a plurality of basic parameters, and the basic parameters are adjusted one by one so that the fitting pressure curve and the actual pressure curve, and the fitting pressure derivative curve and the actual pressure derivative curve coincide within an allowable error range, thereby obtaining the fitting curve; The step three specifically includes the following steps: inverting to obtain the total volume of the cracks in the target area, combining the calculated crack volume of the characteristic oil and gas wells to obtain the crack volume of the reservoir cracks in the target area.

2. The method according to claim 1, characterized in that The step 1 specifically includes the following steps: determining the characteristic oil and gas wells in the target area; Applying segmented or large-scale fracturing technology to the characteristic oil and gas wells to determine the fracture characteristics of the fracturing fractures; A pressure recovery well test is performed on the characteristic oil and gas well to obtain the well test curve of the characteristic oil and gas well.

3. The method according to claim 2, characterized in that The characteristic oil and gas wells include: some marginal wells in the development of fracture-cavity type oil reservoirs and oil and gas wells in which only some fractures are developed in the reservoir.

4. The method according to claim 2, characterized in that The fracture characteristics include: the length of the hydraulic fracture, the width of the hydraulic fracture and the height of the hydraulic fracture.

5. The method according to claim 1, characterized in that The step 2 specifically includes the following steps: constructing the mathematical expression for describing the fracture capacity and morphological characteristics, and analyzing and obtaining the flow state influencing parameters that affect the flow state.

6. The method according to claim 5, characterized in that The flow state influencing parameters include fracture volume and comprehensive compressibility coefficient.

7. A well test curve interpretation device for complex fracture combination reservoirs, characterized in that: The method according to any one of claims 1 to 6 is performed, wherein the device comprises: A well testing module, which is used to determine the application construction method of the target area based on the production data of the target area, perform a pressure recovery well test on the target area, and obtain a well testing curve of the target area; A fitting module, which is used to adjust parameters and perform curve fitting through a mathematical expression constructed to describe fracture capacity and morphological characteristics, so as to obtain a fitting curve that fits the well test curve; The inversion module is used to invert application parameters characterizing fracture characteristics based on the fitting curve, and combine them with the shape of the well test curve to obtain fracture volume information of a complex fracture combination reservoir including hydraulic fractures and reservoir fractures.

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