A method for acid fracturing of carbonate reservoir fracture network

Abstract

The invention provides a fracture network acid fracturing method for carbonate rock reservoirs. The method comprises the following steps: a. the step of selecting the fracture network acid fracturing section; b. the step of injecting low-viscosity acid liquid and slick water into the well sequentially at low displacement; c. injecting low-viscosity slick water into the well sequentially at high displacement The steps of water and acid liquid; d, the step of injecting slick water to carry proppant or temporary plugging agent in the well; e, the step of repeating step c and step d one or more times; f, the step of injecting displacement fluid into the well with low displacement step. The method of the invention plays a guiding role in acid fracturing design and construction, reduces construction difficulty and risk, improves construction efficiency, and ensures the effectiveness of acid fracturing construction and the acid fracturing effect of fracture networks.

Description

technical field [0001] The invention relates to the field of oil and gas exploitation, in particular, the invention relates to a fracture network acid fracturing method for carbonate rock reservoirs. Background technique [0002] Carbonate reservoirs generally contain natural fractures and dissolution pores, and the reservoirs are highly heterogeneous. Natural fractures are one of the main storage places for oil and gas. Due to the generally low matrix permeability of carbonate reservoirs in China, the main channels for oil and gas seepage are natural fractures. [0003] Field practice has proved that acid fracturing is an important technical measure for increasing production of carbonate reservoirs. The purpose of conventional acid fracturing is to create long fractures, inject high-viscosity fracturing fluid and acid fluid into the formation sequentially or alternately, press open formation fractures, and reduce acid fluid loss and delay acid rock formation by increasing ...

AI Technical Summary

Problems solved by technology

Acid fracturing for deep and ultra-deep fractured carbonate reservoirs faces many difficulties: ①The matrix is ​​generally dense or low porosity and permeability, how to increase the contribution rate of the matrix to production; How to increase the degree of reconstruction of natural fractures and increase the contact area between fractures and the reservoir matrix; ③Deep burial and high temperature lead to fast acid-rock reaction, and the penetration distance of acid-etched fractures is limited, which cannot effectively communicate with favorable reservoirs far away from the wellbore

[0006] Chinese patent CN103089228 discloses a cross-linked acid-carrying sand acid fracturing method on the ground of argillaceous dolomite. In view of the characteristics of rapid decrease in fracture conductivity of argillaceous dolomite after acid fracturing, acid-etched fractures are filled with cross-linked acid-carrying sand. Methods Using ground cross-linked acid, the wellbore friction is large, the construction pressure is high, and the average sand ratio of cross-linked acid is 11.2%, the sand concentration is low, and the conductivity of acid-etched fractures is insufficient; the viscosity of cross-linked acid is high, Good performance in reducing fluid loss and speed retardation, but not strong in reforming slot network

[0007] Chinese patent CN101353958 discloses a temperature-controlled variable-viscosity acid fracturing method for oil and gas wells, which uses an acid system in which the viscosity of the acid solution increases with temperature. After the acid solution enters the high-temperature formation, the viscosity increases and the acid-rock reaction rate decreases. This method is applied in the conventional acid fracturing process, and it also has the characteristics of weak fracture network reforming ability

[0008] Chinese patent CN103590803 discloses a solid acid-acid fracturing process. First, high-viscosity fracturing fluid is used to create fractures, and then water-insoluble solid acid at room temperature is injected to allow the solid acid to enter artificial fractures. The acid liquid is gradually released through the temperature rise and pressure of the formation, and the deep part of the formation is acid-etched. The solid acid particles injected in this method can continuously release the acid liquid to dissolve the rock formation, but the solid particles are too large to enter the natural fractures. At the same time This method also adopts the conventional acid fracturing process design method, and the fracture network reconstruction ability is poor