Method for fracturing front temporary plugging body of fractured zone shale

Abstract

The invention discloses a method for fracturing a shale front temporary plugging body in a fracture zone, and relates to the field of shale gas fracturing. The method for fracturing the fracture zone shale front temporary plugging body comprises the following steps that a shale fracture development degree judgment model is established, and the natural fracture development degree of a target layer is judged according to the shale fracture development degree judgment model; different displacement wellhead pressure values are calculated according to logging data interpretation and small-pressure test data, and a fracture zone shale body transformation construction pressure judgment standard is established; in the early stage of the fracturing implementation process, a front temporary plugging process is adopted for construction; and displacement, liquid viscosity and in-seam temporary plugging process parameters are adjusted to achieve reservoir transformation. According to the method for fracturing the fracture zone shale front temporary plugging body, provided by the invention, field engineers can be helped to judge the development degree of stratum fractures and evaluate whether fracturing transformation is effective or not, and a systematized front temporary plugging process and a field construction regulation and control means are provided on the basis, so that the transformation effect of the fracture zone shale is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of shale gas fracturing, and in particular to a method for pre-temporary plugging and main fracturing of shale in a broken zone. Background Art

[0002] Hydraulic fracturing is a key technology for achieving large-scale development of unconventional oil and gas resources such as shale oil and gas, tight oil and gas, etc. The effect of large-scale volume fracturing determines the level of shale gas production. Therefore, in order to ensure a higher single well production, the shale reservoir needs to be fully transformed.

[0003] A block in a shale gas field is a normal pressure area as a whole, of which 60% of the area has strong structural deformation, the formation is relatively broken, and some areas belong to large-scale natural fracture areas. At present, for shale gas reservoirs with large-scale fractures, the domestic fracturing transformation measures are mostly "multi-cluster dense cutting combined with mid-way temporary plugging materials to promote fracture diversion" technology, and no targeted measures are taken for the special formation conditions of "large-scale fractures". The adjustment methods adopted on site are mostly "empirical method" and "trial and error method", but the actual construction pressure is much lower than the extension pressure of the non-fracture zone reservoir, showing obvious large-scale fracture induction phenomenon. At the same time, the mid-way temporary plugging technology used has extremely limited effect on fracture plugging, and the second-level construction extension pressure after temporary plugging has not been significantly improved. According to the existing construction and test data, the production of the broken zone wells that have completed the construction has not reached the ideal effect after casing testing.

[0004] There are still several problems in the domestic fracturing transformation of shale gas reservoirs with large-scale fractures in broken zones: First, for shale gas reservoirs with large-scale fractures, during the fracturing site construction, on-site engineers lack a means to quickly judge the degree of formation fracture development; second, for such shale gas reservoirs, there is a lack of a method to evaluate whether the fracturing transformation is effective; third, for shale gas reservoirs with fractures, there is a lack of an efficient large-scale fracture plugging and fracturing transformation technology. Summary of the invention

[0005] The purpose of this application is to provide a method for pre-temporary plugging and main fracturing of shale in the broken zone, which can help on-site engineers determine the degree of formation fracture development and evaluate whether the fracturing transformation is effective, and on this basis provide a systematic pre-temporary plugging process and on-site construction control means, thereby effectively improving the transformation effect of shale in the broken zone.

[0006] This application is implemented as follows:

[0007] The present application provides a method for pre-temporary plugging and main body fracturing of shale in a broken zone, comprising the following steps:

[0008] Establish a shale fracture development degree judgment model, and judge the natural fracture development degree of the target layer based on the shale fracture development degree judgment model;

[0009] Based on the interpretation of logging data and small pressure test data, the wellhead pressure values ​​of different displacements are calculated, and the pressure judgment standard for the reconstruction of the shale body in the broken zone is established;

[0010] In the early stage of fracturing, the pre-temporary plugging technology is used for construction;

[0011] Adjust the displacement, liquid viscosity, and temporary plugging process parameters in the fracture to achieve reservoir transformation.

[0012] In some optional implementation schemes, when establishing a model for determining the degree of shale fracture development, when the liquid efficiency is greater than 30%, it is judged to be a reservoir with relatively developed natural fractures; when the liquid efficiency is between 20% and 30%, it is judged to be a reservoir with developed natural fractures; when the liquid efficiency is between 15% and 20%, it is judged to be a reservoir with excessively developed natural fractures; and when the liquid efficiency is less than 15%, it is judged to be a reservoir with large-scale fracture development.

[0013] In some optional implementation schemes, when the wellhead pressure values ​​at different displacements are calculated based on the interpretation of logging data and small pressure test data, the bottom hole fracture pressure and the minimum horizontal principal stress are calculated, and the total friction resistance and liquid column pressure are calculated by small pressure testing based on the friction resistance along the path, borehole friction resistance, and bending friction resistance at different displacements, and the bottom hole fracture pressure and the minimum horizontal principal stress are converted into wellhead pressure values ​​at different displacements.

[0014] In some optional implementation schemes, when establishing a judgment standard for construction pressure of shale body reconstruction in the broken zone, in the formation fracture stage and when the wellhead construction pressure is greater than the fracture pressure converted to the wellhead, it is regarded as effective fracture of the rock body; in the post-formation fracture stage and when the wellhead pump pressure during construction is greater than the minimum horizontal principal stress converted to the wellhead, it is regarded as the extension of the cracks in the rock body; when the wellhead pump pressure for effective fracture of the rock body and the extension of the cracks in the rock body is lower than the calculated value, the wellhead pump pressure is increased.

[0015] In some optional implementation schemes, when the degree of natural fracture development in the target layer is a large-scale fracture development reservoir, the flow-limiting perforating technology is used to evenly open each cluster of holes, so that each cluster has 6 holes, each section does not exceed 45 holes, and the distance between the clusters is 15-25m.

[0016] In some optional implementation schemes, the pre-temporary plugging process is used in the early stage of the fracturing process to perform construction, including the following steps:

[0017] S1. After acid reduction, increase the discharge volume to 7-8m 3 / min, observe the pressure. If there is a sand adding pressure window, pump in 70 / 140 mesh proppant sand-carrying fluid for 40-60m 3, establish a channel between the wellbore and the natural fracture;

[0018] S2, reduce the displacement to 2-4m 3 / min, add temporary plugging agent 150-250Kg, increase the displacement to 7-8m 3 Continue pumping for 40-60 m / min 3 After the sand-carrying fluid, the displacement is reduced to 2-4m 3 / min, second addition of temporary plugging agent 150-250Kg;

[0019] S3, 6-9m 3 / min displacement, glue introduction 100-150m 3 ;

[0020] S4. After the pressure rises and stabilizes, increase the displacement to the target displacement;

[0021] S5, construction liquid volume reaches 800-1000m 3 When the number of temporary plugging knots is 50-60% of the number of holes, a secondary temporary plugging is performed;

[0022] S6. Carry out the second stage of sand fracturing and stop the pump when the sand and liquid volumes reach the designed values.

[0023] In some optional implementation schemes, the displacement is adjusted so that the construction pressure is higher than the minimum horizontal principal stress converted to the wellhead.

[0024] In some optional implementation schemes, when adjusting the temporary plugging process parameters in the fracture, if the pressure rises quickly and the sand adding pressure window is small when the temporary plugging agent is added to increase the displacement in step S1, the displacement can be increased to 12-14m 3 / min for processing.

[0025] In some optional embodiments, in the non-loose well section, the temporary plugging agent of 150-250 kg in step S2 can be replaced by adding 100-150 m 3 A combination of glue and 70 / 140 mesh proppant with 5-7% of the glue mass.

[0026] The beneficial effects of the present application are as follows: the method for pre-temporary plugging and main body fracturing of shale in the broken zone provided by the present application comprises the following steps: establishing a shale fracture development degree judgment model, and judging the degree of natural fracture development of the target layer according to the shale fracture development degree judgment model; calculating wellhead pressure values ​​of different displacements according to the interpretation of logging data and small pressure test data, and establishing a pressure judgment standard for the construction of the main body transformation of shale in the broken zone; adopting the pre-temporary plugging process for construction in the early stage of the fracturing implementation process; adjusting the displacement, liquid viscosity, and temporary plugging process parameters in the fracture to achieve reservoir transformation. The method for pre-temporary plugging and main body fracturing of shale in the broken zone provided by the present application can help field engineers judge the degree of formation fracture development and evaluate whether the fracturing transformation is effective, and on this basis, provide a systematic pre-temporary plugging process and on-site construction control means, thereby effectively improving the transformation effect of shale in the broken zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic flow chart of a method for pre-temporary plugging and main fracturing of shale in a broken zone provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] The features and performance of the method for pre-temporary plugging and bulk fracturing of shale in a broken zone of the present application are further described in detail below in conjunction with the embodiments.

[0031] like Figure 1 As shown, the embodiment of the present application provides a method for pre-temporary plugging and main body fracturing of shale in a broken zone, comprising the following steps:

[0032] Step 1: Establish a shale fracture development degree judgment model, and judge the degree of natural fracture development of the target layer according to the shale fracture development degree judgment model; wherein, the shale fracture development degree judgment model is: when the liquid efficiency is greater than 30%, it is judged as a reservoir with relatively developed natural fractures; when the liquid efficiency is 20%-30%, it is judged as a reservoir with developed natural fractures; when the liquid efficiency is 15%-20%, it is judged as a reservoir with excessive development of natural fractures; when the liquid efficiency is less than 15%, it is judged as a reservoir with large-scale fracture development.

[0033] Step 2: Calculate the wellhead pressure values ​​of different displacements based on the interpretation of logging data and small pressure test data, and establish the judgment standard for the construction pressure of the shale body transformation in the broken zone; Among them, when establishing the judgment standard for the construction pressure of the shale body transformation in the broken zone, in the formation fracture stage and when the wellhead construction pressure is greater than the fracture pressure converted to the wellhead, it is regarded as an effective fracture of the rock body; in the post-formation fracture stage and when the wellhead pump pressure during the construction process is greater than the minimum horizontal principal stress converted to the wellhead, it is regarded as the extension of the crack in the rock body; when the wellhead pump pressure of the effective fracture of the rock body and the extension of the crack in the rock body is lower than the calculated value, increase the wellhead pump pressure. At the same time, when the degree of natural fracture development in the target layer is a large-scale fracture development reservoir, the flow-limiting perforating technology is used to open each cluster hole evenly, so that each cluster has 6 holes, each section does not exceed 45 holes, and the interval between the sections is 20m.

[0034] Step 3: In the early stage of fracturing, the pre-temporary plugging process is used for construction, and the construction includes the following steps:

[0035] S1. After acid reduction, increase the discharge volume to 8m 3 / min, observe the pressure. If there is a sand adding pressure window, pump in 70 / 140 mesh proppant sand-carrying fluid for 50m 3 , establish a channel between the wellbore and the natural fracture;

[0036] S2, reduce the displacement to 4m 3 / min, add 200Kg of temporary plugging agent, increase the displacement to 8m 3 Continue pumping for 50m / min 3 After the sand-carrying liquid, the displacement is reduced to 3m 3 / min, and add temporary plugging agent 200Kg for the second time;

[0037] S3, 8m 3 / min displacement, 150m3 of glue liquid introduced 3 , reduce filtration loss and promote initial extension of cracks;

[0038] S4. After the pressure rises and stabilizes, increase the displacement to the target displacement;

[0039] S5, construction liquid volume reaches 1000m 3When the number of temporary plugging knots is 50% of the number of holes, a secondary temporary plugging is performed;

[0040] S6. Carry out the second stage of sand fracturing and stop the pump when the sand and liquid volumes reach the designed values.

[0041] Step 4: Adjust the displacement, liquid viscosity, and temporary plugging process parameters in the fracture to achieve reservoir transformation. Among them, when adjusting the displacement, make the construction pressure higher than the minimum horizontal principal stress converted to the wellhead. When adjusting the liquid viscosity, the curve shape and trend should be combined, and the dynamic variable viscosity process should be adopted according to the requirements of fracture creation and sand carrying to meet the construction needs of different stages; when adjusting the temporary plugging process parameters in the fracture, in step S1, if the pressure rises quickly and the sand adding pressure window is small when the temporary plugging agent is added to increase the displacement (the pressure rise exceeds the conventional pressure by 20% and the sand adding pressure window is less than 20% of the conventional sand adding pressure window), the displacement can be increased to 14m after acid drop. 3 / min for treatment; in the non-lost well section, the addition of 200Kg of temporary plugging agent in step S2 can be replaced by adding 150m 3 A combination of glue and 70 / 140 mesh proppant with 5% glue mass.

[0042] The method for pre-temporary plugging and fracturing of shale in the broken zone provided in the embodiment of the present application creatively proposes a fracturing transformation method for shale in the broken zone by pre-temporary plugging of natural fractures in the early stage of the fracturing implementation process to transform the rock body, thereby facilitating on-site engineers to judge the degree of development of formation fractures and evaluate whether the fracturing transformation is effective. On this basis, a systematic pre-temporary plugging process and supporting technologies and on-site construction control means are provided, which has the advantages of reliable principle, good operability and high accuracy, and can effectively improve the transformation effect of shale in the broken zone.

[0043] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A method for temporary plugging and fracturing of shale in a broken zone, characterized in that: The following steps are involved: Establishing a shale fracture development degree judgment model, and judging the natural fracture development degree of the target layer according to the shale fracture development degree judgment model; Based on the interpretation of logging data and small pressure test data, the wellhead pressure values ​​of different displacements are calculated, and the pressure judgment standard for the reconstruction of the shale body in the broken zone is established; In the early stage of fracturing, the pre-temporary plugging technology is used for construction; Adjust the displacement, liquid viscosity, and temporary plugging process parameters in the fracture to achieve reservoir transformation.

2. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 1 is characterized in that: When establishing a model for judging the degree of shale fracture development, when the liquid efficiency is greater than 30%, it is judged as a reservoir with relatively developed natural fractures; when the liquid efficiency is 20%-30%, it is judged as a reservoir with developed natural fractures; when the liquid efficiency is 15%-20%, it is judged as a reservoir with excessively developed natural fractures; and when the liquid efficiency is less than 15%, it is judged as a reservoir with large-scale fracture development.

3. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 1 is characterized in that: When the wellhead pressure values ​​of different displacements are calculated based on the interpretation of logging data and small pressure test data, the bottom hole fracture pressure and the minimum horizontal principal stress are calculated. The friction resistance along the path, the borehole friction resistance and the bending friction resistance at different displacements are obtained through small pressure tests to calculate the total friction resistance and the liquid column pressure. The bottom hole fracture pressure and the minimum horizontal principal stress are converted into wellhead pressure values ​​of different displacements.

4. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 1 is characterized in that: When establishing the judgment standard for the construction pressure of shale body reconstruction in the broken zone, in the formation fracture stage and when the wellhead construction pressure is greater than the fracture pressure converted to the wellhead, the rock body is regarded as effectively fractured; in the post-formation fracture stage and when the wellhead pump pressure during the construction process is greater than the minimum horizontal principal stress converted to the wellhead, the crack is regarded as extending in the rock body; when the wellhead pump pressure for effectively fractured rock body and extension of cracks in the rock body is lower than the calculated value, the wellhead pump pressure is increased.

5. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 2 is characterized in that: When the degree of natural fracture development in the target layer is a large-scale fracture development reservoir, the current-limiting perforation technology is used to evenly open each cluster of holes, so that there are 6 holes in each cluster, no more than 45 holes in each section, and the distance between the clusters is 15-25m.

6. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 1, characterized in that: During the fracturing process, the pre-temporary plugging process is used in the early stage to carry out the construction, which includes the following steps: S1. After acid reduction, increase the discharge volume to 7-8m 3 / min, observe the pressure. If there is a sand adding pressure window, pump in 70 / 140 mesh proppant sand-carrying fluid for 40-60m 3 , establish a channel between the wellbore and the natural fracture; S2, reduce the displacement to 2-4m 3 / min, add temporary plugging agent 150-250Kg, increase the displacement to 7-8m 3 Continue pumping for 40-60 m / min 3 After the sand-carrying fluid, the displacement is reduced to 2-4m 3 / min, second addition of temporary plugging agent 150-250Kg; S3, 6-9m 3 / min displacement, glue introduction 100-150m 3 ; S4. After the pressure rises and stabilizes, increase the displacement to the target displacement; S5, construction liquid volume reaches 800-1000m 3 When the number of temporary plugging knots is 50-60% of the number of holes, a secondary temporary plugging is performed; S6. Carry out the second stage of sand fracturing and stop the pump when the sand and liquid volumes reach the designed values.

7. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 1, characterized in that: When adjusting the displacement, make the construction pressure higher than the minimum horizontal principal stress converted to the wellhead.

8. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 6, characterized in that: When adjusting the temporary plugging process parameters in the seam, if the pressure rises quickly and the sand adding pressure window is small when the temporary plugging agent is added to increase the displacement in step S1, the displacement can be increased to 12-14m after the acid drop. 3 / min for processing.

9. The method for pre-temporary plugging and main body fracturing of shale in a broken zone according to claim 6, characterized in that: In the non-loose well section, the temporary plugging agent of 150-250 kg in step S2 can be replaced by 100-150 m 3 A combination of glue and 70 / 140 mesh proppant with 5-7% of the glue mass.

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