Film formation drilling fluid applicable to coal-bed gas well and preparation method thereof

Abstract

The invention discloses a film formation drilling fluid applicable to a coal-bed gas well and a preparation method thereof. The film formation drilling fluid comprises the following components in percentage by mass: 0.1-0.3% of tackifying agent, 2.0-5.0% of film forming agent, 0.1-0.3% of coated flocculant, 0.2-5.0% of blocking agent, 1.0-10.0% of plugging agent, 0.05-0.2% of alkalinity regulator and the balance of water. By adopting the film formation drilling fluid disclosed by the invention, a low-permeability blocking layer can be quickly formed at the coal pore throat so as to prevent the fluid or solid phase from entering the coal bed, effectively prevent and slow down fluid loss and prevent the easily-hydrated substances in the coal cleat and crack from expanding, dispersing and polluting the reservoir stratum.

Description

technical field [0001] The invention relates to a film-forming drilling fluid suitable for coalbed methane wells and a preparation method thereof, which is applicable to coalbed methane wells and formation sections with large voids and high permeability, and also suitable for sandstones with high permeability in reservoir sections Strata work. Background technique [0002] my country's coalbed methane resources are very rich, but the exploration and development of coalbed methane in my country is still in its infancy. With the continuous deepening of coalbed methane development, the problems of coalbed wellbore stability and coalbed reservoir protection during drilling have become increasingly prominent, which seriously restricts the large-scale development and commissioning of coalbed methane. If a downhole complex accident occurs when drilling in coal and rock sections, it will not only delay the progress of the project but also cause significant economic losses. [0003...

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Problems solved by technology

However, the patent still has the following problems: the main component of the film-forming agent in the film-forming drilling fluid is silicate, and the silicate is strongly alkaline (generally, the pH is above 10), and the coal rock in the coalbed methane reservoir section has a strong alkali Sensitivity, if the pH is too high, the permeability of coal and rock will decrease and damage the reservoir; the main mechanism of action of silicate is that its silanol group reacts with calcium and magnesium ions in formation water or clay minerals in fractures to form silanol Calcium and other precipitation, because the coal rock is a low-permeability reservoir, and the coal rock itself is both a reservoir and a reservoir, and the precipitation generated by silicate will seal the reservoir and cause permanent damage to the reservoir

In addition, the existing film-forming drilling fluids are mainly aimed at mud shale formations, and the plugging and film-forming properties of coal rock formations are not strong, mainly because coal rocks are more lipophilic than hydrophilic. The mud cake formed on the rock surface is of poor quality or not strong

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