A degradable polymer drilling fluid

Abstract

The invention relates to a degradable polymer drilling fluid, and belongs to the technical field of coal bed gas drilling well horizontal well exploitation application. The degradable polymer drilling fluid is characterized in that the degradable polymer drilling fluid comprises water, a degradable densifier, a water-based lubricant, a water blocking resistant agent and an alkalinity adjusting agent, wherein the weight percentages of the degradable densifier, the water-based lubricant, the water blocking resistant agent and the alkalinity adjusting agent respectively account for 1-1.5%, 1-3%, 0.5-1.0% and 0.1-0.2% of the weight of water. The degradable polymer drilling fluid can be used for drilling coal bed gas horizontal wells, can effectively stabilize the coal bed well wall and improve the cuttings carrying capability, and also has the characteristics of degradability, furthest protection of the coal bed, strong coal bed well wall stabilizing capability, good nicking carrying and lubrication capabilities, and good economic benefit.

Description

Technical field: [0001] The invention relates to a degradable polymer drilling fluid, belonging to the technical field of coalbed methane drilling and horizontal well mining application. Background technique: [0002] Coalbed methane, commonly known as gas, as a new type of unconventional natural gas has entered a stage of vigorous development in my country. The mining of coalbed methane not only provides a new type of clean energy for the country, but also provides a strong guarantee for the safe mining of coal mines. Compared with coalbed methane in other countries, my country's coalbed methane has the characteristics of low output. From the perspective of investment return, it is determined that my country's coalbed methane mining must adopt a low-cost strategy; the main investment cost of coalbed methane mining is drilling costs. , including drilling fluid costs. In order to increase the production of coalbed methane, the proportion of coalbed methane mining using horiz...

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Problems solved by technology

[0004] The existing coalbed methane drilling practice has shown that the treatment agents such as water-soluble polymers and hydrated clay in the drilling fluid can easily cause coal seam pollution; on the other hand, the performance requirements of the drilling fluid for horizontal well drilling are relatively strict and If the performance of the drilling fluid is not good, the frictional torque will be too large during the drilling process, which will easily cause vicious accidents such as well wall collapse and buried drilling tools; and wellbore cleaning and wellbore stability are often inseparable. Develop high-performance drilling fluid treatment agent

[0005] At present, the drilling fluid systems for coalbed methane horizontal wells mainly include clear water drilling fluid, active brine drilling fluid, microfoam drilling fluid and conventional polymer drilling fluid; among them, clear water and active brine drilling fluid have solid-free, clay-free and polymer-free treatments. However, the coal seam borehole wall stability and debris-carrying ability are insufficient; although the microbubble drilling fluid and conventional polymer drilling fluid have strong ability to stabilize the coal seam borehole wall, they seriously pollute the coal seam. The production of coalbed methane is low, or even no production

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