Low-pressure sandstone reservoir gas well temporary blocking workover fluid and preparation method thereof

Abstract

The invention relates to the technical field of oil and gas field down-hole operation, and specifically relates to a low-pressure sandstone reservoir gas well temporary blocking workover fluid and a preparation method thereof. The workover fluid is composed of the following components, according to percentages in the wellbore volume: 10-20% of an alcohol-based temporary blocking workover fluid, 0.5-1% of an oil-based spacer fluid, and 79-89.5% of a high-efficiency clay stabilizing agent. The alcohol-based temporary blocking workover fluid is composed of the materials of, by mass, 0.5-1% of a water-absorbent polymer, 1-2% of temporary blocking fiber, 0.5-1% of a fiber dispersing agent, 45-50% of water, and balance of alcohol. The high-efficiency clay stabilizing agent is composed of the materials of, by mass, 0.6-1% of a clay stabilizing agent and 99-99.4% of water. With the workover fluid provided by the invention, effective temporary blocking can be realized upon a porous sandstone reservoir; and the harm of the workover fluid upon stratum can be reduced. The workover fluid also has the characteristic of good salt tolerance. With the workover fluid, hydrate blockage is not formed. The workover fluid is safe and environment-friendly, and is convenient for construction.

Description

technical field [0001] The invention belongs to the technical field of downhole operation in oil and gas fields. Specifically, it relates to a temporary plugging and workover fluid for gas wells in low-pressure sandstone reservoirs and a preparation method thereof, which is mainly used for temporarily plugging and killing porous sandstones during well workover, so as to reduce the damage of the workover fluid to formations. Background technique [0002] For porous low-pressure sandstone gas reservoirs, the permeability is low, and such gas wells need to be stimulated by fracturing to achieve industrial productivity. During the workover operation, the workover fluid will enter the deep part of the reservoir along the fracture surface, so improper selection of workover fluid will cause damage to the water lock of the reservoir around the fracture. In the development and workover process of low-pressure gas fields at home and abroad, clay-free water-based workover fluids are g...

AI Technical Summary

Problems solved by technology

The disadvantage is that the workover operation time is long, and the contact time between the formation and the fluid is long, especially for low-porosity and low-permeability gas reservoirs, the degree of water lock damage will still be serious

The workover fluid with solid phase and no clay phase temporary plugging type adds soluble temporary plugging materials to the workover fluid, which can quickly form temporary plugging on the surface of the hole or fracture, and control the leakage of the workover fluid. The disadvantage is that it is suitable for low permeability Improper treatment of the gas layer and the plugging solution can easily cause damage to the reservoir, and at the same time, the solid phase particles will crystallize, dissolve, and recrystallize due to temperature changes, making the temporary plugging effect unsatisfactory

However, the killing fluid still has the following disadvantages: (1) A certain amount of free water will be generated under the pressure, which will cause damage to the formation; (2) It is prone to hydrolysis when encountering divalent cations, and cannot form effective temporary plugging; (3) In winter During construction, it is easy to generate hydrate, which will cause ice blockage in the wellbore or pipeline, and affect normal operation