Compound saltwater drilling fluid for plugging fractures of coal seam

Abstract

The invention relates to a compound saltwater drilling fluid for plugging fractures of a coal seam, and belongs to the field of petroleum drilling. The compound saltwater drilling fluid is characterized by comprising components in percentage by mass as follows: 6%-8% of calcium carbonate, 4%-6% of emulsified asphalt powder, 10%-12% of barite, 2%-4% of limestone powder, 3%-4% of carboxymethyl starch, 8%-10% of sodium formate, 4%-6% of industrial salt, 2%-4% of potassium chloride, 0.6%-0.8% of polyanionic cellulose and the balance of clear water, wherein emulsified asphalt, calcium carbonate, barite and limestone powder are generally termed as plugging materials. By means of the compound saltwater drilling fluid, the one-time success rate of well completion of an inclined shaft section is increased greatly, the collapse of the coal seam is greatly reduced, the construction period of the inclined shaft section is shortened, and the work efficiency is improved.

Description

technical field [0001] The invention relates to a drilling fluid, in particular to a composite brine drilling fluid for sealing coal seam fissures, and belongs to the field of petroleum drilling. Background technique [0002] During the existing drilling construction of Jingnan horizontal well, coal seam collapses frequently occur in the inclined section. Composite brine drilling fluid system is commonly used. In the past, the content of plugging materials in this system was low, and the coal seam often collapsed during the tripping process after drilling through the coal seam, causing buried drilling tools to fill the well and sidetracking, resulting in huge economic losses. , the main factors leading to coal seam collapse are as follows: [0003] 1. The construction measures and construction parameters are not in place when drilling into the coal seam, which causes great mechanical damage to the coal seam, promotes the further formation of coal seam separation and joints,...

AI Technical Summary

Problems solved by technology

[0003] 1. The construction measures and construction parameters are not in place when drilling into the coal seam, which causes great mechanical damage to the coal seam, promotes the further formation of coal seam separation and joints, and the drilling fluid enters the coal seam cracks to form expansion pressure to induce coal seam collapse

[0004] 2. When drilling into the coal seam, the content of plugging particles in the drilling fluid is less, which cannot fill and seal the coal seam fissures, causing the drilling fluid to enter the coal seam fissures to form expansion pressure. When the liquid column pressure is lower than the expansion pressure, the coal seam is promoted. collapse

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