Method for improving fracturing transformation effect of horizontal well

Abstract

The invention relates to the technical field of oil and gas resource exploration, in particular to a method for improving the fracturing transformation effect of a horizontal well, which comprises the following steps: S1, selecting a multi-opening segmented multi-cluster fractured horizontal well, and evaluating the opening condition of perforation holes in clusters through a casing phase diagram; s2, determining a phase interval of the unopened eyelets distributed on the casing phase diagram; and S3, according to the phase interval of the unopened eyelets distributed on the casing phase diagram, making countermeasures, wherein the countermeasures comprise the steps of increasing the number of the eyelets and reducing the gravity effect of the propping agent in the horizontal section. According to the method, the gravity effect of the proppant in the horizontal section during migration can be analyzed through the actual monitoring characteristics of the perforation cluster of the horizontal well of the development layer, and the opening rate of the holes in the top of the sleeve is improved through the countermeasures of directional perforation, increase of the number of the perforations in the top of the sleeve and optimization of the bullet type aiming at the phenomenon that the opening rate of the holes in the top of the sleeve is low; and finally, monitoring and evaluating the opening condition of the eyelets until the optimal opening rate is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas resource exploration, and is a method for improving the effect of horizontal well fracturing transformation. Background Art

[0002] In recent years, among the newly discovered oil and gas reserves in my country each year, more than 70% of the oil reserves and more than 90% of the natural gas reserves are low-porosity and low-permeability oil and gas reservoirs, and the proportion is still increasing year by year. Low-permeability oil and gas resources have become the main target of exploration and development in my country. For low-porosity and low-permeability reservoirs, large-scale volume transformation is generally required to obtain commercial oil and gas flows. Large-scale segmented multi-cluster fracturing transformation has become the main technology for increasing production.

[0003] The core of staged, multi-cluster fracturing in horizontal wells is to create a complex fracture network system with a large sweep volume in low-permeability reservoirs, fully reforming the reservoir and allowing oil and gas in the formation to flow into the wellbore. With the advancement of downhole high-definition imaging technology, an increasing number of post-fracturing imaging monitoring wells have been used. When observing perforation erosion, it was found that within the same cluster, perforations at the bottom of the casing (low gravity zone) were severely eroded, while perforations at the top of the casing (high gravity zone) were less eroded or even not eroded at all. This indicates that perforations at the bottom of the casing are prone to sand intrusion, while those at the top are difficult to enter. The main reason is that in the horizontal section, the proppant is affected by gravity and migrates along the bottom of the casing, causing the fractures to extend primarily downward, forming a single fracture morphology and over-reforming. While the formation above the casing is under-reformed, this affects the fracturing effect.

[0004] A journal article titled "Comprehensive Optimization Method for Segmented and Clustered Fractures in Shale Gas Horizontal Wells" disclosed that: based on numerical simulation and fracturing simulation, taking into account the actual fracture morphology and the mutual influence of multiple fracture parameters, a more reasonable clustering optimization method was established according to the stress interference and induced stress distribution characteristics between multiple clusters of fractures.

[0005] The journal article, titled "Optimization of Cluster Spacing in Horizontal Well Fracturing Considering Natural Fractures," disclosed that based on the geological and engineering data of the target block, a cluster spacing optimization method considering natural fractures was established using hydraulic fracturing simulation and numerical simulation analysis. The method simulated the effects of different cluster spacing and different matrix permeabilities on the stimulation effect and regional production degree under the dense cutting process.

[0006] The Chinese patent document with publication number CN111734375A (application number CN202010493899.0), publication date October 2, 2020 (application date December 6, 2020), and titled "Method for determining the opening sequence and opening efficiency of perforation clusters in a fracturing layer" discloses: a method for determining the opening sequence and opening efficiency of perforation clusters in a fracturing layer. It proposes to apply the friction calculation method of each cluster to obtain the hydrodynamic pressure distribution along the wellbore to the fracture under actual on-site displacement conditions. According to the conservation of total construction displacement, considering the mutual coupling between the flow and pressure of each cluster, the balance relationship between the system friction and the pressure in the fracture is used to judge whether each perforation cluster can be effectively opened and the opening sequence.

[0007] Currently, fracturing simulation software is primarily used to optimize segmented and clustered design, combined with geological conditions. Cluster activation is determined through engineering parameter calculations, but limited research has been conducted on evaluating the activation of individual perforations within a cluster. Downhole high-definition imaging revealed that gravity effects are severe during proppant migration within horizontal sections, making it difficult to inject sand into the perforations at the top of the casing, resulting in poor reservoir stimulation. There is an urgent need to develop a method to improve the effectiveness of horizontal well fracturing, ensuring uniform activation of all perforations within a cluster and enhancing reservoir stimulation. Summary of the Invention

[0008] The present invention provides a method for improving the fracturing effect of horizontal wells, which overcomes the shortcomings of the above-mentioned existing technologies. It can effectively solve the problems that the existing judgment of cluster opening status relies on fracturing software and mathematical model simulation, which has low accuracy and the gravity effect of horizontal section proppant has a great influence on the fracturing effect.

[0009] The technical solution of the present invention is achieved through the following measures: A method for improving the effect of horizontal well fracturing transformation, comprising the following steps: S1, select multiple staged and multi-cluster fractured horizontal wells and evaluate the opening of the perforations within the clusters through the casing phase diagram; S2, determining the phase interval of the unopened holes distributed on the casing phase diagram; S3, formulating countermeasures based on the phase intervals of the unopened holes distributed on the casing phase diagram, the countermeasures including increasing the number of holes and reducing the gravity effect of the proppant in the horizontal section; S4, perform fracturing operations on the new well according to the response measures and re-evaluate the opening status of each cluster of holes; S5: If the improvement effect of the opening rate of the holes in the cluster is less than the set value, repeat step S4 until the holes in the cluster are evenly opened.

[0010] The following are further optimizations and / or improvements to the above technical solutions: In both the above steps S1 and S4, the opening status of the perforations in the cluster is evaluated by using the casing phase image obtained by the downhole imaging instrument.

[0011] The above step S2 is: respectively counting the phases of the open holes and the unopened holes on the casing phase diagram, and then determining the phase intervals of the unopened holes distributed on the casing phase diagram.

[0012] In the above step S3, for the phase area that is difficult to open, ultra-deep penetrating perforating bullets are used to increase the number of holes.

[0013] The gravity effect of the proppant in the horizontal section is reduced by increasing the concentration of the sand-carrying fluid and / or increasing the displacement.

[0014] In the above step S5, the response measures in step S4 are repeated with gradually increasing intensity.

[0015] The present invention uses the actual monitoring characteristics of a perforation cluster in a development zone's horizontal well to analyze the gravity effect of proppant migration within the horizontal section. To address the low perforation rate at the top of the casing, the invention uses directional perforation to increase the number of perforations at the top of the casing and optimize the perforation shape to improve the perforation rate at the top of the casing. Finally, the perforation opening is monitored and evaluated until the optimal opening rate is achieved. This solves the current problem of low simulation accuracy based on fracturing software and mathematical models, and the significant impact of the gravity effect of proppant in the horizontal section on the fracturing effect. It effectively improves the uniformity of perforation opening and achieves the goal of fully transforming the formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attachment Figure 1 This is a casing phase diagram of the first embodiment of the present invention.

[0017] Attachment Figure 2 This is a casing phase diagram of the best embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions.

[0019] The present invention will be further described below in conjunction with the embodiments and accompanying drawings: Example 1: As shown in the attached Figure 1 As shown, the method for improving the horizontal well fracturing effect includes the following steps: S1, select multiple staged and multi-cluster fractured horizontal wells and evaluate the opening of the perforations within the clusters through the casing phase diagram; S2, determining the phase interval of the unopened holes distributed on the casing phase diagram; S3, formulating countermeasures based on the phase intervals of the unopened holes distributed on the casing phase diagram, the countermeasures including increasing the number of holes and reducing the gravity effect of the proppant in the horizontal section; S4, perform fracturing operations on the new well according to the response measures and re-evaluate the opening status of each cluster of holes; S5: If the improvement effect of the opening rate of the holes in the cluster is less than the set value, repeat step S4 until the holes in the cluster are evenly opened.

[0020] The present invention uses the actual monitoring characteristics of a perforation cluster in a development zone's horizontal well to analyze the gravity effect of proppant migration within the horizontal section. To address the low perforation rate at the top of the casing, the invention uses directional perforation to increase the number of perforations at the top of the casing and optimize the perforation shape to improve the perforation rate at the top of the casing. Finally, the perforation opening is monitored and evaluated until the optimal opening rate is achieved. This solves the current problem of low simulation accuracy based on fracturing software and mathematical models, and the significant impact of the gravity effect of proppant in the horizontal section on the fracturing effect. It effectively improves the uniformity of perforation opening and achieves the goal of fully transforming the formation.

[0021] The above-mentioned method for improving the effect of horizontal well fracturing can be further optimized and / or improved according to actual needs: Example 2: As an optimization of the above example, in both steps S1 and S4, the perforation status of the cluster is evaluated using a casing phase image acquired by a downhole imager. As required, the downhole imager is implemented using a conventional downhole television. This allows for real-time, clear color image monitoring results in both dry and clean borehole conditions, providing a reliable, intuitive, and authentic basis for perforation status within the cluster.

[0022] Example 3: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, step S2 is: respectively count the phases of the open holes and the unopened holes on the casing phase diagram, and then determine the phase interval of the unopened holes on the casing phase diagram. Figure 1 ), the phases of the opened holes and the closed holes are counted respectively, and the phase interval where the closed holes are mainly distributed is determined.

[0023] Example 4: As an optimization of the above example, in step S3, ultra-deep-penetrating perforating bullets are used to increase the number of perforations in phase areas that are difficult to open. The gravity effect of the proppant in the horizontal section is reduced by increasing the sand-carrying fluid concentration and / or increasing the displacement. Directed perforation is performed to adjust the perforating gun phase. Ultra-deep-penetrating perforating bullets are preferably used in phase areas that are difficult to open, i.e., the restricted areas where unopened perforations are concentrated. The countermeasure of increasing the number of perforations is optimized. The countermeasure of reducing the gravity effect of the proppant in the horizontal section is achieved by increasing the sand-carrying fluid concentration and increasing the displacement.

[0024] Example 5: As an optimization of the above-mentioned example, in step S5, the intensity of the countermeasures in step S4 is gradually increased. The intensity of the countermeasures is gradually increased, which means increasing the number of holes or / and increasing the concentration of the sand-carrying fluid or / and increasing the displacement. The present invention can use the actual monitoring characteristics of the perforated holes in a development layer horizontal well to address the problem of uneven hole opening rates in different phases within a cluster. Through directional perforation, the number of holes in the difficult-to-open phase area is optimized, the concentration of the sand-carrying fluid is optimized, and the displacement is increased. The optimized measures are used for construction of new wells, and the opening of the holes is monitored until the optimal opening rate is reached. This solves the current problem of low simulation accuracy relying on fracturing software and mathematical models, and the great influence of the gravity effect of the horizontal section proppant on the fracturing effect. By monitoring and evaluating the improvement of countermeasures, and then monitoring and improving, the uniform opening of holes in the same cluster is effectively improved, and the purpose of fully transforming the formation is achieved.

[0025] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the requirements of different situations.

[0026] The process of the best embodiment of the present invention is: In the first step, four staged, multi-cluster fractured horizontal wells were selected for the shale oil development zone (perforation cluster in this area: 8 holes / meter, deep-penetrating perforating bullets, 60° phase angle). The perforation status of each cluster was evaluated using downhole imaging monitoring results (casing phase map).

[0027] The second step is to use the casing phase diagram (attached Figure 2 ), the phases of the opened holes and the unopened holes were counted respectively. The main distribution phase range of the unopened holes was from 240° to 120° clockwise. The gravity effect of the proppant seriously affected the opening of the holes.

[0028] The third step is to select a well to be fractured in the development area, where the phase range of the most difficult-to-open holes is 240° to 120° clockwise. Three countermeasures are formulated: The first type: directional perforation in 1-10 fracturing stages, with a 60° phase angle spiral perforation pattern, using ultra-deep penetrating perforating bullets at 300°-0°-60°, and deep-penetrating perforating bullets at 120°-180°-240°; The second type: directional perforating in the 11-20 fracturing stage, with a 60° phase angle spiral perforation pattern. Ultra-deep-penetrating perforating bullets are used at 300°-0°-60°, with the number of bullets per meter doubled compared to the previous method. Deep-penetrating perforating bullets are used at 120°-180°-240°, with the number of bullets per meter remaining unchanged. The third type: 21-30 fracturing section. When designing fracturing, the concentration of sand-carrying fluid is increased by 10% and the pumping displacement is increased by 10%.

[0029] In the fourth step, the fracturing well is treated by adopting the countermeasures in the third step. After fracturing, the downhole imaging instrument is used to monitor the results and evaluate the opening status of the holes in each cluster within the section: In segments 1-10, the uniform opening of the holes in the six phases within the cluster is increased by 30%; In segments 11-20, the uniform opening of the holes in the six phases within the cluster increases by 35%; In the 21-30 section, the uniform opening of the holes in the six phases within the cluster increases by 32%.

[0030] In the fifth step, the uniform opening rate of the holes in the cluster needs to be further improved, and the countermeasures in the third step need to be optimized: ultra-deep penetration perforating bullets are used for 300°-0°-60°; deep penetration perforating bullets are used for 120°-180°-240°, and the sand-carrying fluid concentration is designed to be increased by 10%, and the pumping displacement is increased by 10%.

[0031] The optimized plan was implemented and monitored and evaluated. The uniform opening degree of the perforations in the six phases within the cluster increased by 50%, achieving the goal. Subsequent wells to be fractured will be implemented according to the optimized plan.

[0032] The present invention has been applied and verified in multiple blocks, enabling each hole in the cluster to be opened evenly, thereby improving the utilization rate of the reservoir and increasing production.

Claims

1. A method for improving the effect of horizontal well fracturing, characterized in that The steps are as follows: S1, select multiple staged and multi-cluster fractured horizontal wells and evaluate the opening of the perforations within the clusters through the casing phase diagram; S2, determining the phase interval of the unopened holes distributed on the casing phase diagram; S3, formulating countermeasures based on the phase intervals of the unopened holes distributed on the casing phase diagram, the countermeasures including increasing the number of holes and reducing the gravity effect of the proppant in the horizontal section; S4, perform fracturing operations on the new well according to the response measures and re-evaluate the opening status of each cluster of holes; S5: If the improvement effect of the opening rate of the holes in the cluster is less than the set value, repeat step S4 until the holes in the cluster are evenly opened.

2. The method for improving the horizontal well fracturing effect according to claim 1, characterized in that ,In both steps S1 and S4, the opening conditions of the ,perforations in the cluster are evaluated by the casing phase image ,obtained by the downhole imager.

3. The method for improving the horizontal well fracturing effect according to claim 1 or 2, characterized in that: Step S2 is: respectively counting the phases of the open holes and the unopened holes on the casing phase diagram, and then determining the phase intervals of the unopened holes distributed on the casing phase diagram.

4. The method for improving the effect of horizontal well fracturing according to claim 1 or 2, characterized in that: In step S3, for the phase area that is difficult to open, ultra-deep penetrating perforating bullets are used to increase the number of holes; or / and, the gravity effect of the proppant in the horizontal section is reduced by increasing the concentration of the sand-carrying fluid or / and increasing the displacement.

5. The method for improving the effect of horizontal well fracturing according to claim 3, characterized in that: In step S3, for the phase area that is difficult to open, ultra-deep penetrating perforating bullets are used to increase the number of holes; or / and, the gravity effect of the proppant in the horizontal section is reduced by increasing the concentration of the sand-carrying fluid or / and increasing the displacement.

6. The method for improving the effect of horizontal well fracturing according to claim 1, 2 or 5, characterized in that: In step S5, the response measures in step S4 are repeated with gradually increasing intensity.

7. The method for improving the effect of horizontal well fracturing according to claim 3, characterized in that: In step S5, the response measures in step S4 are repeated with gradually increasing intensity.

8. The method for improving the effect of horizontal well fracturing according to claim 4, characterized in that: In step S5, the response measures in step S4 are repeated with gradually increasing intensity.

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