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Rock debris removal technology helps safe and rapid drilling of shale gas horizontal wells

With the deepening of the exploration and development of oil and gas fields, the proportion of highly deviated wells, horizontal wells, and ultra-long horizontal wells is increasing, especially in the shale gas blocks in the southwest. To reduce the occupation of cultivated land, reduce the construction cost of the ground platform, and improve the drilling rate of the shale gas target layer, all the wells are horizontal, and the length of the flat section is mostly 1500m or more.

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However, it is difficult for rock cuttings in a horizontal underground shaft to return up, and a large amount of accumulation leads to many problems, such as ample torque during drilling and considerable friction between lifting and lowering,Fast drilling, less sand return, and long circulation time; wiper trip and sticking during tripping out; The borehole is not clean, resulting in sand setting and sticking; The lower drilling tool body and coupling are seriously worn, and all kinds of tools are covered with mud.

In 2020, Anton Oilfield Services Group introduced the new cuttings removal tool developed by Southwest Petroleum University, which innovatively installed 5-10 cuttings removers into the BHA (Bottom hole assembly) in sections. Through the cooperation of each device, the cuttings that were difficult to remove from the bottom of the well were carried out of the well through the migration mode of “strong turbulence + swirl”,which solved many problems caused by cutting accumulation. The technology has been vigorously promoted in Changning shale gas, Zhaotong shale gas, Xinjiang Oilfield, and other blocks in the past two years. It has been applied to more than 150 wells in various horizontal wells. Compared with adjacent wells, the drilling cycle in the flat section is shortened by 5% on average, and the drilling cost is saved by 7%.

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Application case: Changning XX well has a horizontal section of 2000m long and a good inclination of 89°.To avoid two faults and ensure the drilling rate of the oil reservoir, the trajectory of the horizontal section is wavy. The preferred scheme is adopted for this well. Ten rock debris removal tools are put into the well. The first one is about 150m from the bottom of the well, and one is installed every three drill rods behind; The good section used is 2318–4850m, the cumulative footage is 2532m, and the excellent entry time is 520h. Through the cooperation of 10 tools, the sand return is significantly increased, the rock cuttings accumulated on the downhole wall are effectively removed, the tripping friction is reduced by 10-15 tons, and the drilling torque in the horizontal section is reduced by 3-5 kN.m. The ROP is increased by 20%, and the electric logging and running of oil casing are successful at one time.

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The tool adopts a special-shaped spiral edge and a new chip removal channel, which destroys the rock cutting bed on the lower shaft wall through hydraulic turbulence and mechanical removal. At the same time, tool rotation causes severe turbulence of drilling fluid to prevent secondary settlement of rock cuttings. The special-shaped spiral edge can break the upward returning rock cuttings, reducing the erosion and wear of large particle rock cuttings on the drill pipe, and the new chip removal channel can prevent tool mud bags.

The field practice results show that the rock cuttings removal technology has a good application effect and can be widely used in suitable types such as long horizontal sections, irregular trajectory, and difficult sand carrying, to help the safe and rapid drilling of horizontal wells and help customers increase speed and efficiency.