A drilling fluid for protecting coalbed methane reservoirs

Abstract

The invention discloses a drilling fluid capable of protecting a coal bed methane reservoir. The drilling fluid comprises the following ingredients in percentage by weight: 100 parts of fresh water, 0.1-0.3 part of pH value modifier, 0.5-10 parts of water-sensitivity inhibitor, and 0.1-1 part of waterproof blocking agent. For the drilling fluid, the density is 1.01-1.08g / cm<3>, the pH value ranges 8 to 10, the expansion rate reduction ratio is greater than or equal to 60%, the contact angle reduction rate is greater than or equal to 50%, the hygroscopic-state recovery rate of the core permeability is greater than or equal to 85%, the dry-state recovery rate is greater than or equal to 95%, the coal powder landberra volume reduction rate is greater than or equal to 15%, clay-free phase does not exist, the damage to the coal bed methane reservoir caused by same-phase invasion can be furthest reduced, the hydration of the clay mineral in coal petrography can be effectively prevented, water blocking is reduced, the coal bed methane can be forced to be desorbed from the surface of the coal petrography, the coal bed methane reservoir can be effectively protected, the stability of the coal bed well wall can be retained, the practicability is strong, and the stronger popularization and application values can be achieved.

Description

technical field [0001] The invention belongs to the technical field of oil and natural gas drilling fluids, in particular to a drilling fluid for protecting coalbed gas reservoirs. Background technique [0002] Coalbed methane is a kind of unconventional natural gas resource that is self-generated and self-storage in the coal seam itself, and its main component is methane. my country's coalbed methane resources are about 36.81 trillion m 3 , is three times that of the United States, and is equivalent to the amount of conventional onshore natural gas resources. In recent years, efforts have been made to explore and develop coalbed methane, but the industrial scale and commercial value have not yet formed, and many technical difficulties have been encountered. Reservoir protection Questions are one of them. Coalbed methane reservoirs are very different from conventional sandstone and carbonate reservoirs. They have high adsorption, low permeability, and are easy to be compre...

AI Technical Summary

Problems solved by technology

[0005] The invention provides a drilling fluid for protecting coalbed methane reservoirs, aiming at solving the serious damage of the current drilling fluid to the coalbed methane reservoirs during the drilling process of the coalbed methane reservoirs, reducing the permeability of the reservoirs, Insufficient desorption of coalbed methane, failure to effectively protect the coalbed methane reservoir and maintain the stability of the coalbed well wall

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