Volume fracturing method for greatly improving filling efficiency of micro-support system through deep shale gas

Abstract

The invention discloses a volume fracturing method for greatly improving the filling efficiency of a micro-support system through deep shale gas. The volume fracturing method comprises (1) deep shalekey parameter evaluation; (2) geotechnical engineering comprehensive sweet point evaluation and section cluster perforation position determination; (3) crack parameter system optimization; (4) fracturing construction parameter optimization; (5) different-viscosity smooth water and smooth water, carbon dioxide foam fracturing fluid and pretreatment acid solution formula optimization; (6) perforation operation; (7) acid pretreatment; (8) supercritical carbon dioxide multi-scale crack construction; (9) low-viscosity smooth water branch crack and micro crack expanding and main crack producing construction; (10) alternative injection through supercritical carbon dioxide and smooth water; (11) smooth water and carbon dioxide foam fracturing fluid small particle size supporting agent injection; and (12) displacement operation. By means of the volume fracturing method, the net pressure of a main crack can be improved to the greatest extent, the width of a multi-scale crack is expanded, the flow guiding capability is improved, and therefore the purpose of improving the deep shale gas fracturing effect and increasing the yield is achieved.

Description

technical field [0001] The invention relates to the technical field of oil drilling, and more specifically relates to a volume fracturing method for deep shale gas that greatly improves the filling efficiency of a micro-support system. Background technique [0002] At present, with the deepening of shale gas exploration and development, a large amount of deep shale gas is more and more urgently placed on the agenda, such as Sinopec's Fuling Phase II, Yongchuan-Weiyuan, Dingshan, Nanchuan block and CNPC In the Changning-Weiyuan block of Changning-Weiyuan block, etc., there are a large number of deep shale gas with a burial depth of more than 3500m or even 4000m. [0003] Compared with medium-shallow shale gas, the increase in burial depth leads to the following geological characteristics and fracturing difficulties: [0004] (1) Wellbore friction increases, injection displacement is limited, and fracture creation ability is weakened; [0005] (2) The minimum horizontal prin...

AI Technical Summary

Problems solved by technology

[0004] (1) Wellbore friction increases, injection displacement is limited, and fracture creation ability is weakened;

[0005] (2) The minimum horizontal principal stress increases, resulting in a decrease in both the fracture pressure and the net fracture pressure, resulting in a decrease in fracture complexity

In addition, the diversion capacity is low and the decline is fast;

[0006] (3) The two-way horizontal stress difference increases, making it difficult to turn the crack;

[0007] (4) With the increase of temperature and pressure, the plasticity of rock is enhanced, resulting in difficulty in the initiation and extension of multi-scale fractures, the difficulty of fracture diversion, and the intensification of proppant embedding, all of which affect the complexity of fractures and the improvement of conductivity

However, high construction pressure is the most direct problem in deep shale fracturing. The above-mentioned technologies such as temporary plugging and diversion and high-viscosity liquid often cause a sudden increase in construction pressure and increase construction risks. At the same time, due to the partial plasticity of deep shale reservoirs, The closure pressure is high, and the fracturing fractures are mainly small-scale. It is still difficult to form a multi-scale fracture system with a single liquid system such as supercritical carbon dioxide. The complexity of fracturing fractures in deep shale and the volume of stimulation are limited, which cannot achieve economic development. value

[0015] The pertinent measures for the geological characteristics of deep shale gas mentioned above are not strong. Therefore, it is necessary to study and propose a new volume fracturing technology suitable for the characteristics of deep shale gas in order to approach the limitations of the above technologies.