CN111305803A - A shale gas horizontal well cut-off fracturing method - Google Patents

Abstract

The invention provides a shale gas horizontal well cut-off fracturing method. In a shale gas development block, a horizontal well is selected, and the position of each fracturing section is determined, starting from the toe end, at least every three fracturing Sections are divided into one group, starting from the toe end, the first fracturing is performed on the last fracturing section of the first group, and after the first fracturing is completed, starting from the toe end, complete the rest of the first group in sequence. Fracturing of each fracturing section. This fracturing method can slow down the accumulation of in-situ stress, thereby slowing down the extrusion deformation of the formation on the casing; at the same time, the interference between fractures will increase, forming a wider complex fracture network and reducing the possibility of stress reversal near the wellbore , increasing the complexity of the far-field fracture network, easy operation, and no need to run special downhole tools.

Description

A shale gas horizontal well cut-off fracturing method

technical field

The invention relates to the field of oil and natural gas development, in particular to a fracturing method for shale gas horizontal wells.

Background technique

During the implementation of multi-stage fracturing in horizontal wells, a large amount of sand-carrying fracturing fluid is pumped into the reservoir, and the reservoir is "broken" step by step, in order to form a complex fracture network and greatly improve the overall permeability of the reservoir, so as to achieve Industrial exploitation of shale gas. However, in the recent fracturing process, the casing deformation problem has occurred in domestic and foreign blocks and is becoming more and more prominent, especially in the domestic Sichuan area, which has reached an average of more than 40%. During the fracturing process, the in-situ stress field changes sharply, especially the fracturing method from the toe end to the heel end causes the non-uniform in-situ stress generated by the crack expansion to accumulate step by step, which is very likely to cause damage and deformation in the latter half of the horizontal section of the casing. , the subsequent bridge plug cannot be run, which seriously affects the subsequent fracturing construction and greatly reduces the effect of fracturing.

SUMMARY OF THE INVENTION

In view of the above-mentioned problem that a large number of casing damages occur during the fracturing process of horizontal wells in shale gas reservoirs, the present invention proposes a truncation fracturing method for shale gas reservoirs that can alleviate casing deformation. This method can effectively In order to effectively complete the fracturing construction of the shale gas reservoir, the following are the technical solutions provided by the present invention:

A shale gas horizontal well cut-off fracturing method. In a shale gas development block, a horizontal well is selected, and the following steps are performed:

(a) determine the location of each fracturing segment;

(b) Starting from the toe end, at least every 3 fracturing sections are grouped into a group, and the groups are sorted and numbered, so that the horizontal section of the horizontal well consists of relatively independent groups;

(c) first fracturing the last fracturing section of the first group;

(d) After the first fracturing is completed, start from the position near the toe end, and complete the fracturing of the remaining fracturing sections in the first group in sequence;

(e) Steps (c) and (d) are repeated until the fracturing of the remaining groups of the horizontal well is completed.

More preferably, starting from the toe end, each relatively independent group of the horizontal section of the horizontal well is composed of 5 of the fracturing sections.

The shale gas reservoir truncated fracturing method adopted in the present invention can release the in-situ stress in a section, slow down the accumulation of in-situ stress, thereby slow down the extrusion deformation of the stratum on the casing, and at the same time the interference between the fractures will increase, forming a wider range of complex fracture networks, and the reservoir stimulation volume will be larger; reducing the possibility of stress reversal near the wellbore, increasing the complexity of the far-field fracture network; easy to operate, without the need to run special downhole tools.

Description of drawings

The following drawings are only for further understanding of the embodiments of the present invention, and do not constitute any limitation to the protection scope of the present invention.

Fig. 1 is a schematic diagram of the fracturing sequence of the preferred embodiment of the present invention

Figure 2 shows the in-situ stress distribution after fracturing.

Detailed ways

Below in conjunction with embodiment and accompanying drawing, the purpose of the present invention, technical scheme and technical effect are further described completely and in detail:

As shown in Figure 1, a shale gas horizontal well cut-off fracturing method is to select a horizontal well 1 in the shale gas development block, and implement the following steps: (a), determine the fracturing on the horizontal well 1 (b) From the toe end, at least every 3 fracturing sections 2 are divided into a group 3, and the group 3 is sorted and numbered, as shown in Figure 1, I, II, III, thus, Horizontal well 1 consists of relatively independent groups 3; (c), starting from the toe end, perform the first fracturing on the last fracturing section 2 (Fig. A) of the first group 3 (Fig. I); (d) After the first fracturing is completed, start from the position near the toe end and complete the remaining fracturing sections 2 in the first group 3 in the order shown in Figure 1 (Figures B, C, D, E, etc.) fracturing; (e), repeat steps (c) and (d) until the fracturing of the remaining groups 3 of horizontal well 1 (illustration II, III, etc.) is completed.

Since the design of parameters such as the spacing between the two clusters in the fracturing section is usually designed reasonably by the fracturing design unit in combination with the field conditions, this patent does not limit the spacing between the two clusters in the fracturing section.

FIG. 1 shows a more preferred embodiment of the present invention. Starting from the toe end, each relatively independent group 3 of the horizontal section of the horizontal well 1 is composed of five fracturing sections 2 respectively. Among them, the serial numbers A to E in the group 3 represent the fracturing sequence.

As shown in Figure 1, a shale gas reservoir fracturing method is selected. In a certain shale gas development block, a horizontal section of a horizontal well 1 is selected, and it is expected to implement 20-level fracturing, and the following steps are implemented: (a) Determine the position of each fracturing section 2 on the horizontal well 1; (b), starting from the toe end, 5 fracturing sections 2 are divided into a group 3, and the group 3 is sorted and numbered, as shown in Figure 1 Middle I, II, III, (Note: the fourth group is not shown) Therefore, the horizontal well 1 consists of 4 relatively independent groups 3; (c) Starting from the toe end, the first group 3 (shown in the figure) The first fracturing is performed in the last fracturing section 2 (Fig. A) of I); (d), after the first fracturing is completed, start from the near toe end, and follow the sequence B~ E to complete the fracturing of the remaining 4 fracturing sections 2 (B, C, D, E) in the first group 3 in sequence; (e), repeat steps (c) and (d) until the horizontal well 1 is completed Fracturing for each of the remaining groups 3 (shown II, III, and fourth group (not shown)).

Figure 2 shows the in-situ stress distribution after fracturing. Since the stress value around the wellbore increases during the fracture propagation process, the Mises stress value acting on the casing increases greatly. It can be seen from Fig. 2 that during the conventional fracturing process from the toe end to the heel end, the in-situ stress is continuously increasing; while the fracturing sequence provided by the technical solution of the present invention is carried out, in the second fracturing After the fracture, the in-situ stress near the wellbore in the later section hardly increases, and the final stress increase value is also small, so that the stress acting on the casing is also small, reducing the risk of casing deformation and failure. It can be seen that when fracturing is performed according to the fracturing sequence provided by the technical solution of the present invention, the continuous accumulation of in-situ stress during the fracturing process can be effectively prevented, which is beneficial to protect the integrity of the casing in the subsequent fracturing section and ensure the smooth operation of the subsequent fracturing. conduct.

The above is only a description of the specific implementation of the embodiments of the present invention, and any modifications, equivalent replacements, etc. made by those of ordinary skill in the technical field based on the technical solutions of the present invention and the accompanying drawings belong to the protection scope of the present invention.

Claims (2)

1. A shale gas horizontal well cut-off fracturing method, in a shale gas development block, selects a horizontal well, and implements the following steps: (a) determine the location of each fracturing segment; (b) Starting from the toe end, at least every 3 fracturing sections are grouped into a group, and the groups are sorted and numbered, so that the horizontal section of the horizontal well consists of relatively independent groups; (c) first fracturing the last fracturing section of the first group; (d) After the first fracturing is completed, start from the position near the toe end, and complete the fracturing of the remaining fracturing sections in the first group in sequence; (e) Steps (c) and (d) are repeated until the fracturing of the remaining groups of the horizontal well is completed. 2. A shale gas horizontal well cut-off fracturing method according to claim 1, characterized in that: starting from the toe end, each relatively independent group of the horizontal section of the horizontal well consists of five Fracturing section composition.

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