Low-viscosity mixed fracturing fluid, its application and oil and gas reservoir stimulation method

Abstract

The invention relates to low-viscosity mixed fracturing fluid, application of the fracturing fluid and an oil and gas reservoir transformation method. The mixed fracturing fluid is formed by adding acids and active agents into fracturing fluid without adding any cross-linking agent. The mixed fracturing fluid is low in viscosity, low in friction and high in sand-carrying capacity. When being applied to the oil and gas reservoir transformation process, the mixed fracturing fluid can serve as fracturing fluid and can also serve as acid liquor, so that two reservoir transformation methods, such as fracturing (sand fracturing) and acidizing can be simultaneously performed. The reservoir is pressed to open, the opened reservoir fracture wall surface (a filtration zone) is subjected to acid etching, a part with wide fracture is filled and supported with the sand carried by the mixed fracturing fluid, while sand cannot enter a part with narrow fracture or some small branch fractures. However, the acid in the mixed fracturing fluid can enter the fracture to perform acid etching and cleaning. Therefore, the fracture part without sand support also has a certain flow conductivity. In addition to the reservoir oil displacement function of the active agents, the reservoir transformation effect is greatly improved.

Description

technical field [0001] The invention relates to an acid-added mixed fracturing fluid and its application, especially the low-viscosity non-crosslinked fracturing fluid mixed with acid (or acid and active agent), which has the functions of sand-adding fracturing, acidizing and oil displacement. Three functions. The present invention also relates to a method for improving reservoirs in oil and gas fields, especially a new method for improving reservoirs in which acidification, sanding and fracturing and oil displacement are combined and can be carried out simultaneously during the reconstruction of clastic rock reservoirs. method. Background technique [0002] At present, the reconstruction process of clastic rock reservoirs is sand fracturing, which plays an important role in the reservoir stimulation of oil and gas field development. , the fracturing fluid is injected into the oil layer under high pressure, so that the pressure in the wellbore gradually increases, thereby ...

AI Technical Summary

Problems solved by technology

However, the high-viscosity cross-linked fracturing fluid (jelly) commonly used in the fracturing process can damage the fracture wall (residual gel plugging), and oil and gas flow out of the fracture wall from the reservoir into the fracture and then flow into the wellbore, so It is important to improve the seepage capacity of the fracture wall

In addition, the fractures opened by the existing sand fracturing method are wedge-shaped, and the far end of the fracture is too narrow, and the sand may not get in. Some small branch cracks on the edge of the main fracture may also cause sand to enter because of their narrowness. If not, there is also the problem of the sand-carrying performance of the fracturing fluid at high temperature in the formation (the problem of "sand plugging" may occur), which makes it difficult for the proppant (sand) to support the fracture to meet expectations, which in turn will affect the conductivity of the fracture. As a result, the final transformation of the reservoir is difficult to achieve the expected effect

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