A high-efficiency well-flushing fluid for well-flushing in low-permeability sandstone reservoirs

Abstract

The invention provides an efficient flushing fluid for well flushing of a low-permeability sandstone oil reservoir. The efficient flushing fluid is prepared from 0.1%-1.0% of a water block preventing agent, 0.5%-3.0% of an anti-swelling agent, 5.0%-10.0% of a cosolvent and the balance of water. By means of the efficient flushing fluid, the wetness of the low-permeability sandstone oil reservoir can be changed from strong water wetness into weak water wetness, and the capillary self-priming capability of reservoir stratum is eliminated; the efficient flushing fluid has ultralow oil-water interfacial tension and strong anti-emulsification capability, and water block and Jamin damage can be effectively reduced; the efficient flushing fluid has excellent clay expansion preventing performance, can effectively reduce water-sensitivity damage and protects the hydrocarbon reservoir to the greatest extent.

Description

technical field [0001] The invention relates to a well-flushing fluid, in particular to a well-flushing fluid suitable for reservoir protection of low-permeability sandstone reservoirs. Background technique [0002] Well flushing is one of the common maintenance measures for oil wells, but low-permeability reservoirs generally have the characteristics of low formation pressure and strong reservoir sensitivity. When conventional well flushing fluid is used for well flushing operations, the flushing fluid can easily enter the reservoir , cause water lock, emulsification, water sensitivity and other damage to the reservoir, and a large number of laboratory experiments show that the damage caused by the well flushing fluid intruding into the formation is mainly water lock, but also hydration expansion and oil-water emulsification. Once these reservoir damages are formed, it is difficult to remove them, which makes it difficult or takes a long recovery period for the production o...

AI Technical Summary

Problems solved by technology

However, there are still two problems in the following aspects: ①The well flushing fluid system generally has insufficient interfacial tension reduction, poor anti-emulsion ability, and poor effect of inhibiting hydration swelling, etc., which are difficult to meet the needs of low-permeability reservoir protection; ②Well flushing fluid system In order to eliminate the damage of drilling fluid to gas layers, there are few well flushing fluid systems for oil well flushing and conventional operations, and relatively few studies on rock wettability

Although the oil layer protection accelerator can make the anti-swelling rate reach more than 92%, and the surfactant can also greatly reduce the oil-water interfacial tension and capillary resistance, it cannot change the wettability of the rock from strong hydrophilic to weak hydrophilic. Eliminate reservoir self-priming capillary forces