Solid-free active salt water drilling fluid for coalbed methane (CBM) horizontal wells

Abstract

The invention relates to a solid-free active salt water drilling fluid for coalbed methane (CBM) horizontal wells, belonging to the technical field of CBM drilling and mining. The drilling fluid is characterized by comprising water, a water-based lubricant, an anti-water-blocking agent and soluble salt, wherein the water-based lubricant accounts for 1-3% of water by weight; the anti-water-blocking agent accounts for 0.5-1.0% of water by weight; the soluble salt is used for adjusting the density of the drilling fluid and is determined according to required drilling fluid density; the water-based lubricant is water-based polymeric alcohol or water-soluble polyethylene glycol; the anti-water-blocking agent is an organosilicon surfactant or nonylphenol polyoxyethylene ether; and the soluble salt is industrial sodium chloride, industrial potassium chloride or industrial calcium chloride and is used for adjusting the density of the drilling fluid. The solid-free active salt water drilling fluid can not only furthest protect the coal beds but also effectively stabilize well walls and keep boreholes clean and has the characteristics of solid-free property, low surface tension, strong anti-swelling property and density adjustability.

Description

Technical field: [0001] The invention relates to a solid-phase-free active brine drilling fluid for coalbed methane horizontal wells, belonging to the technical field of coalbed methane drilling and exploitation. Background technique: [0002] Coalbed methane, commonly known as gas, as a new type of unconventional natural gas, has entered a vigorous development stage in my country. The exploitation of coalbed methane can not only provide a new type of clean energy for the country, but also provide 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 ho...

AI Technical Summary

Problems solved by technology

[0004] The practice of coalbed methane drilling has shown that treatment agents such as water-soluble polymers and hydrated clays in drilling fluids can easily cause coal seam pollution

On the other hand, horizontal well drilling has strict requirements on the performance of the drilling fluid. If the performance of the drilling fluid is not good, it will cause excessive friction torque and collapse of the well wall during the drilling process, resulting in serious accidents such as buried drilling tools; Wellbore cleaning and wellbore stability are often inseparable from high-performance drilling fluid treatment agents

At present, although clean water is used as drilling fluid to protect the coal seam well, the collapse of the coal seam in the horizontal section is very serious; although the conventional drilling fluid for oil and gas wells can meet the stability requirements of the horizontal section of the coal seam, the production of coalbed methane is extremely low , or even no output, coal seam pollution is very serious

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