A reservoir stimulation method and system based on acid etching technology

Abstract

This invention provides a reservoir stimulation method and system based on acid etching technology. The method identifies the distribution of effective natural fractures in each near-wellbore reservoir to be stimulated, and constructs a three-dimensional geological model of each reservoir by combining the reservoir's structural characteristics and the distribution of caves. Then, it constructs a reservoir fracturing calculation model by combining the rock elasticity parameters obtained during drilling and the corresponding reservoir's geostress distribution model. Based on the calculation results, it optimizes fracturing operation parameters according to fracturing requirements. Based on the fracturing operation parameters, acid is injected according to a set strategy to further form artificial fracture channels based on natural fractures, connecting the distributed fracture-cavity reservoirs, and then flowback is performed to complete the cavity finding process. Using the above-mentioned scheme of this invention, the problems of complex operation and limited fracture opening in existing geological stimulation technologies can be overcome. Based on the idea of ​​"fracturing to find cavities," it utilizes natural fractures and acid-etched fractures to form effective channels connecting caves, maximizing the utilization of wellbore oil and gas reserves.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development and optimization technology, and in particular to a reservoir stimulation method and system based on acid etching technology. Background Technology

[0002] my country has relatively abundant oil and gas resources, and a considerable portion of the exploitable oil and gas is stored in carbonate reservoirs. A prominent feature of carbonate reservoirs is the presence of numerous natural fractures and irregularly distributed caves. Effective exploration and development practices have shown that caves in fracture-vuggy reservoirs are the main storage spaces for oil and gas resources, while natural fractures are the main seepage channels for oil and gas.

[0003] The key to the effective development of fractured-vuggy carbonate reservoirs lies in how to reliably connect the cavities, enabling usable cavities to communicate with the wellbore. Currently, the main technology for connecting cavities is temporary plugging and diversion acid fracturing. For example, patent application number 201710170058.4 provides an integrated method for temporary plugging and diversion and fracture support in fractured carbonate reservoirs. It discloses the steps for fracturing when there are one or more rock layers to be modified. This method targets rock layers with different structures, successively pumping pre-fracturing fluid, a composite temporary wall system within the fracture, and acid with viscosity-changing ability into the formation. It further pumps proppant-carrying fluid and displacement fluid into the formation. During the final pumping, instead of injecting gel fracturing fluid containing the composite temporary wall system at the fracture opening, proppant-carrying fluid is injected, thus completing the temporary plugging and diversion and fracture support of the fractured carbonate reservoir.

[0004] Currently, when the number of karst caves is small, it is possible to connect karst caves by diverting through fractures to target known fractures and karst caves. However, when the number of karst caves is large, not only is the operation complicated, but the lack of operational guidance and complete logical planning makes it difficult to achieve the effect of connecting multiple karst caves at the same time. At the same time, the number of natural fractures that can be opened during the fracturing process through temporary plugging diversion technology is limited, and the utilization rate of natural fractures is low, which leads to the restriction of oil and gas entry channels into the well.

[0005] Given the developmental characteristics of natural fractures and caves in fracture-vuggy carbonate reservoirs, it is necessary to seek a new modification technique that can fully utilize natural fractures and achieve multi-directional communication between multiple caves.

[0006] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] To address the above problems, the present invention provides a reservoir stimulation method based on acid etching technology. In one embodiment, the method includes:

[0008] The geological feature modeling steps include selecting reservoirs within a defined range near the wellbore as reservoirs to be stimulated, identifying the distribution of effective natural fractures in each reservoir to be stimulated, and constructing a three-dimensional geological model of the current reservoir by combining the structural features of the reservoir and the distribution of karst caves.

[0009] The construction planning steps are as follows: based on the constructed three-dimensional geological model, the reservoir fracturing calculation model is constructed by combining the rock elastic mechanical parameters during the drilling process and the corresponding reservoir in-situ stress distribution model, and the fracturing construction parameters are adjusted based on the calculation results with fracturing requirements as the target.

[0010] The fracturing process involves locating cavities and injecting acid according to fracturing parameters to create artificial fracture channels based on natural fractures, thereby connecting fractured-cavity reservoirs distributed within the reservoir.

[0011] The backflow step involves injecting displacement fluid into the artificially formed fracture channels to achieve backflow.

[0012] In an optional embodiment, a fractured-vuggy reservoir within 30m from the center of the wellbore is selected as the reservoir to be modified, and the effective natural fractures of the reservoir to be modified meet the requirement that the fracture density is greater than 1 fracture / m.

[0013] Furthermore, in one embodiment, the geological feature modeling step includes:

[0014] Acquire imaging logging data of the reservoir to be identified, and use its fracture distribution characteristics and cavern distribution characteristics to extract auxiliary logging information of effective natural fractures and caverns in the reservoir. The distribution characteristics and auxiliary logging information together constitute the logging information data body of fractures and caverns in the reservoir.

[0015] The auxiliary logging information includes the relevant logging characteristics of natural fractures and caves in sonic logging, density logging, spontaneous potential logging, resistivity logging, and natural gamma logging data.

[0016] In one embodiment, the geological feature modeling step further includes:

[0017] Based on the drilling depth information, the logging data volume of fractures and caverns is loaded into the three-dimensional seismic data volume corresponding to the reservoir to identify the seismic attribute characteristics of each fracture and cavern.

[0018] Based on the seismic attribute characteristics of fractures and karst caves, the coherence volume and ant volume identification and analysis methods are used to track the characteristics of fractures and karst caves around the seismic data of the entire reservoir area, and a three-dimensional geological feature model of fractures and karst caves in the entire area is constructed.

[0019] Specifically, in one embodiment, during the process of tracking and identifying the seismic data volume of the entire region, drilling data is used for verification to optimize and correct the relevant parameters of the identification and analysis method;

[0020] In practical applications, in one embodiment, the three-dimensional geological feature model displays the location, direction, extension length, and inclination information of cracks according to the location distribution pattern of cracks, and displays the depth, height, average diameter, and volume parameters of karst caves according to the location distribution pattern of karst caves.

[0021] Furthermore, in one embodiment, the process of constructing a reservoir fracturing calculation model in the construction planning step, combining the rock elastic mechanical parameters obtained during drilling and the corresponding reservoir in-situ stress distribution model, includes:

[0022] Based on the rock elasticity and mechanical parameter profile established by drilling, a three-dimensional distribution model of the elastic modulus and Poisson's ratio of the matrix rock mass is obtained through generalization processing.

[0023] Export the overall 3D geological model as a node mesh file;

[0024] Input the node mesh file and use geostress calculation software to obtain the geostress distribution of the overall three-dimensional geological model, and establish a geostress distribution model;

[0025] By combining the geostress distribution model and the three-dimensional distribution model of elastic modulus and Poisson's ratio, the fracturing effect corresponding to different construction parameters is simulated, and the correlation statistics are used to form a reservoir fracturing calculation model. By changing the construction parameters, artificial fractures with different distribution characteristics can be obtained through fracturing.

[0026] In a preferred embodiment, the fracturing cavity-finding step includes the following operations:

[0027] Step A1: According to the fracturing construction parameters, inject the set acid solution according to the activation flow rate. The acid solution reacts chemically with the rock minerals in the reservoir to form an artificial fracture network around the well. The artificial fracture network includes acid-etched main fractures and activated and connected natural fractures. The activation flow rate is greater than the reservoir filtration flow rate.

[0028] Step A2: Further inject the set acid solution according to the dissolution rate. The acid solution is filtered out and enters the artificial crack network to dissolve and expand the existing cracks, so that the natural cracks are interconnected to form flow channels in different directions.

[0029] Step A3: Connect the fractured-vuggy reservoirs in different directions within the wellbore reservoir area through numerous interconnected fracture channels around the well.

[0030] Based on the methods described in any one or more of the above embodiments, the present invention also provides a storage medium storing program code that can implement the methods described in any one or more of the above embodiments.

[0031] Based on other aspects of the methods described in any one or more of the above embodiments, the present invention also provides a reservoir stimulation system based on acid etching technology, which performs the methods described in any one or more of the above embodiments.

[0032] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0033] This invention provides a reservoir stimulation method based on acid etching technology. This method identifies the distribution of effective natural fractures in each near-wellbore reservoir to be stimulated, and constructs a three-dimensional geological model of each reservoir by combining the structural characteristics of the reservoir and the distribution of karst caves. The constructed three-dimensional geological model can accurately reflect the distribution, geometric features and geological attribute data of each fracture and karst cave in the reservoir, providing data and structural support for optimizing construction parameters.

[0034] Furthermore, this invention combines the rock elastic mechanical parameters from drilling with the corresponding reservoir in-situ stress distribution model to construct a reservoir fracturing calculation model, and optimizes the fracturing construction parameters based on the calculation results with fracturing requirements as the target. The acid etching fracturing process based on the distribution characteristics of natural fractures is inherently less constrained by in-situ stress. The above scheme can largely overcome the influence of in-situ stress factors on fracturing calculations, while also considering the rock core mechanical characteristics during drilling, effectively minimizing the deviation between the fracturing calculation results and the actual fracturing effect.

[0035] Based on the above strategy, acid fracturing is achieved by first activating artificial fractures with a low flow rate, and then using a higher flow rate to achieve filtration and dissolution. This saves resources while ensuring the highest utilization rate of natural fractures and maximizing the use of well-circumferential oil and gas reserves, which is conducive to the development and optimization of oil and gas extraction work.

[0036] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic flowchart of a reservoir stimulation method based on acid etching technology provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the principle of cavity finding in a reservoir stimulation method based on acid etching technology provided in another embodiment of the present invention;

[0040] Figure 3 This is a diagram showing the distribution of caverns in the target reservoir of the reservoir stimulation method based on acid etching technology provided in this embodiment of the invention.

[0041] Figure 4 This is a schematic diagram of the fracturing calculation model prediction of a reservoir stimulation method based on acid etching technology in one embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram of the reservoir stimulation system based on acid etching technology provided in an embodiment of the present invention. Detailed Implementation

[0043] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. Those skilled in the art will then fully understand how the present invention uses technical means to solve technical problems and achieve technical effects, and will be able to implement the present invention specifically based on the above-described implementation process. It should be noted that, as long as there is no conflict, the various embodiments and features of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0044] Although the flowchart describes the operations as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. A process can terminate when its operation is complete, but it may also have additional steps not included in the diagram. A process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0045] Computer equipment includes user equipment and network equipment. User equipment or clients include, but are not limited to, computers, smartphones, PDAs, etc.; network equipment includes, but is not limited to, a single network server, a server group consisting of multiple network servers, or a cloud based on cloud computing consisting of a large number of computers or network servers. Computer equipment can operate independently to implement this invention, or it can connect to a network and implement this invention through interaction with other computer equipment in the network. The network in which the computer equipment is located includes, but is not limited to, the Internet, wide area network, metropolitan area network, local area network, VPN network, etc.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a” and “an” as used herein are also intended to include the plural. It should also be understood that the terms “comprising” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, without excluding the presence or addition of one or more other features, integers, steps, operations, units, components, and / or combinations thereof.

[0047] my country has relatively abundant oil and gas resources, most of which are stored in carbonate reservoirs. A prominent feature of carbonate reservoirs is the presence of numerous natural fractures and caves. Exploration and development practices have shown that caves are the main storage spaces for oil and gas resources, while natural fractures are the main seepage channels for oil and gas.

[0048] The key to developing fractured-vuggy carbonate reservoirs lies in how to efficiently connect the cavities. Currently, the main technology for connecting cavities is temporary plugging and acid fracturing. Patent application number 201710170058.4 provides an integrated method for the temporary plugging and fracturing of fractured carbonate reservoirs, disclosing the steps for when there are one or more strata to be modified. This method can achieve the integration and synchronization of temporary plugging and fracturing. Patent application number 201710901127.4 discloses a temporary plugging fluid for acid fracturing of carbonate rocks. This fluid includes water, lignocellulose, high-temperature resistant and saturated salt resistant modified starch, superabsorbent resin, sodium dodecyl sulfate, and dodecyltrimethylammonium bromide. The temporary plugging fluid has high pressure resistance, high temperature resistance, and is easy to backflow. Patent application number 201510497011.X discloses a testing device and method for testing the temporary plugging performance of acid fracturing diverting agents. This invention places a Hastelloy cartridge at the front end of the core column to facilitate the bearing of confining pressure and the loading of the temporary plugging diverting agent. It can simulate the process of acid carrying the temporary plugging diverting agent into fractures and avoid the problem of softer temporary plugging diverting agents being compacted under displacement pressure differentials, leading to blockage of the core inlet. Currently, when the number of cavities is small, fracture diversion can be used to connect the cavities. However, when the number of cavities is large, the effect of simultaneous connection of multiple cavities cannot be achieved. Furthermore, the number of natural fractures that can be opened during fracturing using temporary plugging diversion technology is limited, resulting in low utilization of natural fractures and limited oil and gas entry channels into the well.

[0049] Given the developmental characteristics of natural fractures and caves in fracture-vuggy carbonate reservoirs, it is necessary to seek a new stimulation technique that can fully utilize natural fractures to achieve multi-directional communication of multiple caves. Based on this, this invention provides a reservoir stimulation method based on acid etching technology, using a fracture-following cave-finding concept.

[0050] To address the aforementioned issues, this invention provides a reservoir stimulation method and system based on acid etching technology. This solution is based on the concept of "fracturing to find caves," forming a process method that utilizes natural fractures in the reservoir to connect near-wellbore caves. The characteristic of this process is that the extension of artificial fractures is minimally constrained by the direction of geostress. It can achieve communication between the wellbore and multiple cave reservoirs in different directions through a network of interconnected natural fractures and acid-etched main fractures, thereby maximizing the utilization of surrounding oil and gas reserves.

[0051] The following describes the detailed flow of the method according to an embodiment of the present invention with reference to the accompanying drawings, the steps of which can be executed in a computer system containing, for example, a set of computer-executable instructions. Although the logical order of the steps is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0052] Example 1

[0053] Figure 1 This diagram illustrates a flow chart of the reservoir stimulation method based on acid etching technology provided in Embodiment 1 of the present invention. Figure 1 As can be seen, the method includes the following steps.

[0054] Geological feature modeling step S110: Select the reservoir within the defined range near the well as the reservoir to be stimulated, identify the distribution of effective natural fractures in each reservoir to be stimulated, and construct a three-dimensional geological model of the current reservoir in combination with the structural features of the reservoir and the distribution of karst caves.

[0055] Construction planning step S120: Based on the constructed three-dimensional geological model, combined with the rock elastic mechanical parameters during the drilling process and the corresponding reservoir in-situ stress distribution model, construct the reservoir fracturing calculation model, and adjust the fracturing construction parameters based on the calculation results and fracturing requirements.

[0056] Step S130 of fracturing and finding cavities: Inject acid according to the fracturing construction parameters to further form artificial fracture channels based on natural fractures, so as to connect the fractured-cavity reservoirs distributed in the reservoir.

[0057] In the backflow step S140, displacement fluid is injected based on the formed artificial crack channel to achieve backflow.

[0058] The logic employed in the above embodiments can fully utilize natural fractures to achieve multi-directional communication between multiple karst caves. Specifically, in practical applications, the distribution and characteristic data of natural fractures and karst caves in the strata are determined through the above geological feature modeling steps. Typically, geological modeling software can be used to implement modeling according to the set logic. In a preferred embodiment, a fractured-cavity reservoir within a range of 0–30 m from the center of the wellbore is selected as the reservoir to be modified, and the effective natural fractures in the reservoir to be modified satisfy a fracture density greater than 1 fracture / m.

[0059] Specifically, before performing modeling, data such as sonic logging, density logging, imaging logging, spontaneous potential logging, resistivity logging, and natural gamma logging can be collected in the study area;

[0060] Furthermore, Figure 2 The diagram illustrates the principle of cavity-finding in the reservoir stimulation method based on acid etching technology provided in this embodiment of the invention. Figure 2As shown, in one embodiment, the geological feature modeling step includes:

[0061] Acquire imaging logging data of the reservoir to be identified, and use its fracture distribution characteristics and cavern distribution characteristics to extract auxiliary logging information of effective natural fractures and caverns in the reservoir. The distribution characteristics and auxiliary logging information together constitute the logging information data body of fractures and caverns in the reservoir.

[0062] The auxiliary logging information includes the relevant logging characteristics of natural fractures and caves in sonic logging, density logging, spontaneous potential logging, resistivity logging, and natural gamma logging data.

[0063] In the above embodiments, imaging logging can directly obtain the distribution characteristics of typical fractures and cavities, extract other logging data corresponding to fractures and cavities, and extend their application to other layers and well locations throughout the region to establish a distribution characteristic model of fractures and cavities in drilling.

[0064] Considering that the seismic properties of fractures and cavities within a reservoir can significantly influence the effectiveness of fracture fracturing and connectivity, the researchers of this invention utilize geological modeling software to load drilling and logging data into a three-dimensional seismic data volume. Based on the depths of fractures and cavities identified in the drilling, the seismic property characteristics corresponding to the fractures and cavities in the seismic data volume are determined and used as key parameters for identification and comparison across the entire work area using the software. Therefore, in one embodiment, the geological feature modeling step further includes:

[0065] Based on the drilling depth information, the logging data volume of fractures and caverns is loaded into the three-dimensional seismic data volume corresponding to the reservoir to identify the seismic attribute characteristics of each fracture and cavern.

[0066] Based on the seismic attribute characteristics of fractures and karst caves, the coherence volume and ant volume identification and analysis methods are used to track the characteristics of fractures and karst caves around the seismic data of the entire reservoir area, and a three-dimensional geological feature model of fractures and karst caves in the entire area is constructed.

[0067] In practical applications, based on the coherence volume and ant volume identification and analysis technology, combined with the parameter characteristics of cracks and karst caves obtained in the second step, the seismic data volume of the entire region is tracked and identified, and the identification parameters are modified using drilling data. On this basis, a three-dimensional geological model of cracks and karst caves in the entire region is established.

[0068] The three-dimensional geological feature model displays the location, direction, extension length, and inclination of cracks according to their location distribution patterns, and displays the depth, height, average diameter, and volume parameters of karst caves according to their location distribution patterns.

[0069] In the process of tracking and identifying seismic data volumes across the entire region, drilling data can be used for verification, optimization, and correction of relevant parameters in the identification and analysis methods.

[0070] Furthermore, the established three-dimensional geological model needs to be extracted, and fracturing software should be used to optimize the construction parameters. Once the geological model is established, a three-dimensional spatial distribution model of fractures and karst caves can be obtained, including the location, orientation, extension length, and dip of fractures, as well as key parameters such as the depth, height, average diameter, and volume of karst caves.

[0071] Furthermore, the planning of fracturing construction parameters is achieved through the following approach: (1) By combining attribute analysis with the rock elastic mechanical parameter profile established by drilling, a three-dimensional distribution model of the elastic modulus and Poisson's ratio of the matrix rock mass is obtained through generalization.

[0072] (2) Export the geological model (including stratigraphic interfaces, faults, fractures and caves) as a whole as a node mesh file;

[0073] (3) Using geostress calculation software, input the node mesh file, establish a three-dimensional calculation model, compare it with the actual geological model, and optimize the unreasonable areas in the local area.

[0074] (4) Using geostress software, calculate the geostress distribution of the three-dimensional geological body and establish a geostress distribution model;

[0075] (5) Based on this, a fracturing construction model can be constructed to obtain the distribution of the main fractures after fracturing, the condition of the natural fractures connected after fracturing, and the modified volume after fracturing. By changing the construction parameters, the fracture distribution characteristics under different conditions can be obtained. Based on this, the construction parameters can be optimized to obtain the best fracturing and natural fracture connection effect.

[0076] In one specific embodiment, the process of constructing a reservoir fracturing calculation model in the construction planning step, combining the rock elastic mechanical parameters obtained during drilling and the corresponding reservoir stress distribution model, includes:

[0077] Based on the rock elasticity and mechanical parameter profile established by drilling, a three-dimensional distribution model of the elastic modulus and Poisson's ratio of the matrix rock mass is obtained through generalization processing.

[0078] Export the overall 3D geological model as a node mesh file;

[0079] Input the node mesh file and use geostress calculation software to obtain the geostress distribution of the overall three-dimensional geological model, and establish a geostress distribution model;

[0080] By combining the geostress distribution model and the three-dimensional distribution model of elastic modulus and Poisson's ratio, the fracturing effect corresponding to different construction parameters is simulated, and the correlation statistics are used to form a reservoir fracturing calculation model. By changing the construction parameters, artificial fractures with different distribution characteristics can be obtained through fracturing.

[0081] After determining the fracturing operation parameters, acid is injected according to the designed strategy through the fracturing cavity finding step. Based on the natural fractures, artificial fracture channels are further formed to connect the fractured-vuggy reservoirs distributed in the reservoir.

[0082] In a preferred embodiment, the fracturing cavity-finding step includes the following operations:

[0083] Step A1: According to the fracturing construction parameters, inject the set acid solution according to the activation flow rate. The acid solution reacts chemically with the rock minerals of the reservoir to form acid-etched wormholes, thereby forming an artificial fracture network around the well. The artificial fracture network includes acid-etched main fractures and activated and connected natural fractures. The activation flow rate is greater than the reservoir filtration flow rate.

[0084] Step A2: Further inject the set acid solution according to the dissolution rate. The acid solution is filtered out and enters the artificial crack network to dissolve and expand the existing cracks. The existing wormholes are connected and opened to allow the natural cracks to be interconnected and form flow channels in different directions.

[0085] Step A3: Connect the fractured-vuggy reservoirs in different directions within the wellbore reservoir area through numerous interconnected fracture channels around the well.

[0086] In step A1 above, acid is injected at a lower set displacement to allow the acid to react chemically with the rocks and minerals in the near-wellbore area, forming artificial fractures around the well. These artificial fractures include, but are not limited to, the main acid fractures and activated interconnected natural fractures.

[0087] Furthermore, in step A2, acid is injected at a set flow rate higher than the activation flow rate. The acid is filtered out and enters the natural fractures, dissolving, expanding, and activating the natural fractures. A large number of activated natural fractures are interconnected and form flow channels around the fractures in different directions around the well.

[0088] Then, by utilizing numerous interconnected fracture channels around the well, the flow path is completed by connecting fractured reservoirs in different directions near the wellbore. Finally, displacement fluid is introduced to achieve backflow.

[0089] Taking a fractured-vuggy carbonate reservoir with well-developed near-wellbore fractured-vuggy reservoirs as an example, the reservoir properties are good, with porosity greater than 10% and permeability greater than 1 mD; the vuggy radius is greater than 0.5 m, and there is no connecting channel between the vuggy and the wellbore. In a specific embodiment, the target reservoir is the Ordovician 5965.54-6074.83m interval, with lithology of light gray, gray micritic limestone, micritic sandstone, and sandstone micritic limestone. Well logging interpretation shows two 24m sections of Class II reservoir and two 21m sections of Class III reservoir. Seismic interpretation data shows that the reservoir interval in this well exhibits obvious beaded reflection characteristics, indicating the development of fractured-vuggy reservoirs, such as... Figure 3 As shown.

[0090] The reservoir to be modified is selected from fractured-vuggy reservoirs within 30m of the wellbore center in the near-wellbore zone; furthermore, the fractured-vuggy reservoirs in the near-wellbore zone have well-developed natural fractures with a natural fracture density greater than 1 fracture / m.

[0091] Furthermore, the near-wellbore fractured-cavity reservoirs described herein are characterized by the coexistence of fractures and cavities, with poor connectivity.

[0092] Furthermore, the acid solution is an acid solution suitable for acidification of carbonate rocks, including but not limited to gelling acid;

[0093] Furthermore, when setting the dissolution discharge rate, the discharge rate is generally 0.5 to 1 m when the dissolution distance is 0 to 15 m around the well. 3 When the dissolution distance is 15-30 meters around the well, the discharge rate is generally 1-3 m³ / min. 3 / min, based on the overall control principle of on-site construction feedback, is a discharge rate slightly greater than the corresponding formation filtration rate;

[0094] The activation displacement is usually selected as a low displacement, which in practical applications can be a displacement that is less than the formation's ultimate liquid absorption rate.

[0095] Furthermore, the injected liquid flows along the fractures, following the distribution pattern of the reservoir's original natural fractures, to form an interconnected fracture network. The injected liquid includes, but is not limited to, acid.

[0096] Furthermore, the aforementioned "cavity finding" refers to connecting caves through an interconnected network of cracks formed by activated natural fissures and acid-etched main fissures.

[0097] Furthermore, the aforementioned "fracturing" refers to the process and means of acidizing, while "cavitation" refers to the result of acidizing. The purpose is to achieve the connection between the karst cave and the wellbore through fracturing and cavitation.

[0098] The target reservoir is stimulated using a fracture-cavity search technique for acid treatment. The fracture-cavity search path is as follows: Figure 4 As shown, the implementation procedure is as follows:

[0099] (1) Inject 30m of acid solution 3 The injection displacement is 1.0–2.0 m³. 3 / min, to displace the kill fluid in the wellbore;

[0100] (2) Inject 400m of acid solution 3 The injection displacement is 1.0–5.0 m³. 3 / min, forming acid-etched fracture channels within the reservoir;

[0101] (3) Inject 60m of slippery water 3 The injection displacement is 1.0–5.0 m³. 3 / min, pushing the acid in the wellbore into the formation;

[0102] (4) The construction of the seam-hole connection is completed.

[0103] The acid solution formula for the acidification process of finding cracks and holes is: 0.8% DJ-09A gelling agent + 2.0% DJ-04 high temperature corrosion inhibitor + 1.0% DJ-02 drainage aid + 1.0% DJ-07 iron ion stabilizer + 1.0% DJ-10 demulsifier.

[0104] For the foregoing method embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0105] It should be noted that in other embodiments of the present invention, the method can also be combined with one or more of the above embodiments to obtain a new reservoir stimulation method based on acid etching technology, so as to achieve geological stimulation of the reservoir in the required well area.

[0106] It should be noted that, based on the methods in any one or more embodiments of the present invention described above, the present invention also provides a storage medium storing program code capable of implementing the methods as described in any one or more embodiments. When executed by an operating system, this code can implement the reservoir modification method based on acid etching technology as described above.

[0107] Example 2

[0108] The methods described in detail in the above-disclosed embodiments of the present invention can be implemented using various forms of devices or systems. Therefore, based on other aspects of the methods described in any one or more of the above embodiments, the present invention also provides a reservoir stimulation system based on acid etching technology, which is used to execute the reservoir stimulation method based on acid etching technology described in any one or more of the above embodiments. Specific embodiments are given below for detailed description.

[0109] Specifically, Figure 5 The diagram shows a schematic representation of a reservoir stimulation system based on acid etching technology provided in an embodiment of the present invention. Figure 5 As shown, the system includes:

[0110] The geological feature modeling module 51 is configured to select reservoirs within a set range near the well as reservoirs to be stimulated, identify the distribution of effective natural fractures in each reservoir to be stimulated, and construct a three-dimensional geological model of the current reservoir by combining the structural features of the reservoir and the distribution of karst caves.

[0111] Construction planning module 53 is configured to construct a reservoir fracturing calculation model based on the constructed three-dimensional geological model, combined with the rock elastic mechanical parameters during the drilling process and the corresponding reservoir in-situ stress distribution model, and adjust the fracturing construction parameters based on the calculation results and fracturing requirements.

[0112] The fracturing cavity finding module 55 is configured to inject acid according to the fracturing operation parameters to further form artificial fracture channels based on natural fractures, so as to connect the fractured-cavity reservoirs distributed in the reservoir.

[0113] The backflow module 57 is configured to inject displacement fluid based on the formed artificial crack channels to achieve backflow.

[0114] Furthermore, in one embodiment, a fractured-vuggy reservoir within 30m of the wellbore center is selected as the reservoir to be modified, and the effective natural fractures of the reservoir to be modified satisfy a fracture density greater than 1 fracture / m.

[0115] In a preferred embodiment, the geological feature modeling module performs the following operations:

[0116] Acquire imaging logging data of the reservoir to be identified, and use its fracture distribution characteristics and cavern distribution characteristics to extract auxiliary logging information of effective natural fractures and caverns in the reservoir. The distribution characteristics and auxiliary logging information together constitute the logging information data body of fractures and caverns in the reservoir.

[0117] The auxiliary logging information includes the relevant logging characteristics of natural fractures and caves in sonic logging, density logging, spontaneous potential logging, resistivity logging, and natural gamma logging data.

[0118] Furthermore, in one embodiment, the geological feature modeling module also performs the following operations:

[0119] Based on the drilling depth information, the logging data volume of fractures and caverns is loaded into the three-dimensional seismic data volume corresponding to the reservoir to identify the seismic attribute characteristics of each fracture and cavern.

[0120] Based on the seismic attribute characteristics of fractures and karst caves, the coherence volume and ant volume identification and analysis methods are used to track the characteristics of fractures and karst caves around the seismic data of the entire reservoir area, and a three-dimensional geological feature model of fractures and karst caves in the entire area is constructed.

[0121] Specifically, in one optional embodiment, the geological feature modeling module uses drilling data for verification and optimization of relevant parameters of the identification and analysis method during the process of tracking and identifying the seismic data volume around the whole area;

[0122] In one embodiment, the constructed three-dimensional geological feature model displays the location, direction, extension length, and dip information of cracks according to the location distribution pattern of cracks, and displays the depth, height, average diameter, and volume parameters of karst caves according to the location distribution pattern of karst caves.

[0123] Furthermore, the process of constructing a reservoir fracturing calculation model in the construction planning step, combining the rock elastic mechanical parameters obtained during drilling and the corresponding reservoir stress distribution model, includes:

[0124] Based on the rock elasticity and mechanical parameter profile established by drilling, a three-dimensional distribution model of the elastic modulus and Poisson's ratio of the matrix rock mass is obtained through generalization processing.

[0125] Export the overall 3D geological model as a node mesh file;

[0126] Input the node mesh file and use geostress calculation software to obtain the geostress distribution of the overall three-dimensional geological model, and establish a geostress distribution model;

[0127] By combining the geostress distribution model and the three-dimensional distribution model of elastic modulus and Poisson's ratio, the fracturing effect corresponding to different construction parameters is simulated, and the correlation statistics are used to form a reservoir fracturing calculation model. By changing the construction parameters, artificial fractures with different distribution characteristics can be obtained through fracturing.

[0128] In a preferred embodiment, the fracturing cavity-finding module performs the following operations:

[0129] Step A1: According to the fracturing construction parameters, inject the set acid solution according to the activation flow rate. The acid solution reacts chemically with the rock minerals in the reservoir to form an artificial fracture network around the well. The artificial fracture network includes acid-etched main fractures and activated and connected natural fractures. The activation flow rate is greater than the reservoir filtration flow rate.

[0130] Step A2: Further inject the set acid solution according to the dissolution rate. The acid solution is filtered out and enters the artificial crack network to dissolve and expand the existing cracks, so that the natural cracks are interconnected to form flow channels in different directions.

[0131] Step A3: Connect the fractured-vuggy reservoirs in different directions within the wellbore reservoir area through numerous interconnected fracture channels around the well.

[0132] In the reservoir stimulation system based on acid etching technology provided in this embodiment of the invention, each module or unit structure can operate independently or in combination according to actual analysis and dissolution requirements to achieve the corresponding technical effects.

[0133] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0134] The phrase "an embodiment" in the specification means that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0135] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A reservoir stimulation method based on acid etching technology, characterized in that, The method includes: Geological feature modeling steps: Select reservoirs within a defined range near the wellbore as reservoirs to be stimulated, identify the distribution of effective natural fractures in each reservoir to be stimulated, and construct a three-dimensional geological model of the current reservoir by combining the structural characteristics of the reservoir and the distribution of karst caves; Select fractured-vuggy reservoirs within 30m from the center of the wellbore as reservoirs to be stimulated, and ensure that the effective natural fractures in the reservoirs to be stimulated meet the requirement of a fracture density greater than 1 fracture / m. Construction planning steps: Based on the constructed three-dimensional geological model, combined with the rock elastic mechanical parameters during the drilling process and the corresponding reservoir in-situ stress distribution model, a reservoir fracturing calculation model is constructed, and the fracturing construction parameters are adjusted based on the calculation results and fracturing requirements. Fracturing cavity finding steps: According to the fracturing construction parameters, acid is injected to further form artificial fracture channels based on natural fractures, so as to connect the fractured-vuggy reservoirs distributed in the reservoir. The backflow step involves injecting displacement fluid into the artificially created fracture channels to achieve backflow. The geological feature modeling step includes: Based on the drilling depth information, the logging data volume of fractures and karst caves is loaded into the three-dimensional seismic data volume corresponding to the reservoir. The seismic attribute characteristics corresponding to each fracture and karst cave are identified. Based on the fracture and karst cave depths identified by drilling, the seismic attribute characteristics corresponding to fractures and karst caves in the seismic data volume are determined. Based on the seismic attribute characteristics of fractures and karst caves, the coherence volume and ant volume identification and analysis methods are used to track the characteristics of fractures and karst caves around the seismic data of the entire reservoir area, and a three-dimensional geological feature model of fractures and karst caves in the entire area is constructed. The fracturing cavity finding step includes: Step A1: Based on the fracturing operation parameters, inject the set acid solution according to the activation flow rate. The acid solution reacts chemically with the rock minerals in the reservoir to form an artificial fracture network around the well. The artificial fracture network includes acid-etched main fractures and activated and connected natural fractures. The activation flow rate is greater than the reservoir filtration flow rate. Step A2: Further inject the set acid solution according to the dissolution rate. The acid solution is filtered out and enters the artificial crack network to dissolve and expand the existing cracks, so that the natural cracks are interconnected to form flow channels in different directions. Step A3: Connect fractured-vuggy reservoirs in different directions within the wellbore reservoir area through numerous interconnected fracture channels around the well.

2. The method as described in claim 1, characterized in that, The geological feature modeling step includes: Acquire imaging logging data of the reservoir to be identified, and use its fracture distribution characteristics and cavern distribution characteristics to extract auxiliary logging information of effective natural fractures and caverns in the reservoir. The distribution characteristics and auxiliary logging information together constitute the logging information data body of fractures and caverns in the reservoir. The auxiliary logging information includes the relevant logging characteristics of natural fractures and caves in sonic logging, density logging, spontaneous potential logging, resistivity logging, and natural gamma logging data.

3. The method as described in claim 1, characterized in that, During the process of tracking and identifying the seismic data volume across the entire region, drilling data was used for verification, and the relevant parameters of the identification and analysis methods were optimized and corrected.

4. The method as described in claim 1, characterized in that, The three-dimensional geological feature model displays the location, direction, extension length, and inclination of cracks according to their location distribution patterns, and displays the depth, height, average diameter, and volume parameters of karst caves according to their location distribution patterns.

5. The method as described in claim 1, characterized in that, In the aforementioned construction planning steps, the process of constructing a reservoir fracturing calculation model by combining the rock elastic mechanical parameters obtained during drilling and the corresponding reservoir stress distribution model includes: Based on the rock elasticity and mechanical parameter profile established by drilling, a three-dimensional distribution model of the elastic modulus and Poisson's ratio of the matrix rock mass is obtained through generalization processing. Export the overall 3D geological model as a node mesh file; Input the node mesh file and use geostress calculation software to obtain the geostress distribution of the overall three-dimensional geological model, and establish a geostress distribution model; By combining the geostress distribution model and the three-dimensional distribution model of elastic modulus and Poisson's ratio, the fracturing effect corresponding to different construction parameters is simulated, and the correlation statistics are used to form a reservoir fracturing calculation model. By changing the construction parameters, artificial fractures with different distribution characteristics can be obtained through fracturing.

6. A storage medium, characterized in that, The storage medium stores program code capable of implementing the method as described in any one of claims 1 to 5.

7. A reservoir stimulation system based on acid etching technology, characterized in that, The system performs the method as described in any one of claims 1 to 5.

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