Water-base drilling fluid suitable for low-well-temperature high-layer pressure coefficients

Abstract

The invention discloses water-base drilling fluid suitable for low-well-temperature high-layer pressure coefficients. The water-base drilling fluid is prepared from the following components in parts by weight of clean water, an inhibitor, a fluid loss additive, a plugging agent, a lubricant, a flow pattern adjusting agent, a pH-regulating agent and a weighting agent in the ratio of the clean water to the inhibitor, to the fluid loss additive, to the plugging agent, to the lubricant, to the flow pattern adjusting agent, to the pH-regulating agent and to the weighting agent being 100 to (25-30) to (25-30) to (5-8) to (1-2) to (1-3) to (0.5-1) to (160-200). The water-base drilling fluid is used, so that environmental hazard of oil-base drilling fluid can be avoided, and the water-base drilling fluid has the characteristics of high-efficiency plugging, multi-phased lubrication, composite restraining and weak gel coagulation. The water-base drilling fluid is particularly suitable for shale gas wells and difficult wells to use, wherein the bottom hole temperature of the shale gas wells and the difficult wells is lower than 100 DEG C, the shale gas wells and the difficult wells are easy to hydrate and collapse, and high in formation pressure coefficients, and the density of the drilling fluid of the shale gas wells and the difficult wells achieves 2.0g / cm<3> or above.

Description

technical field [0001] The invention relates to the technical field of oil and gas drilling, in particular to a high-performance water-based drilling fluid suitable for shale gas horizontal wells. Background technique [0002] With the success of large-scale commercial development of shale gas in the United States, my country is also paying more and more attention to the exploitation and utilization of shale gas. From the Sinian to the Middle Triassic, my country has a wide range of developed marine deposits, with a distribution area of ​​more than 200 square kilometers and a cumulative maximum stratum thickness of more than 10Km. According to reliable exploration data, the shale gas in the Lower Cambrian Qiongzhusi Formation in the southern Sichuan Basin alone is 7.14-14.6×10 12 m 3 , which is 1-2 times of the existing conventional natural gas resources in the entire Sichuan Basin. Therefore, the development of shale gas has both broad application prospects and high stra...

AI Technical Summary

Problems solved by technology

[0003] With the continuous development of shale gas exploration and development in Sichuan, during the drilling process of shale sections, the preparation and maintenance cost of conventionally used oil-based drilling fluid is high, the safety risk of use is great, the environmental pollution is serious, and the oil-based drilling cuttings are not easy to handle. As a result, shale gas cannot be developed economically and environmentally friendly. Therefore, the use of a high-performance water-based drilling fluid instead of oil-based drilling fluid is more in line with the requirements of environmental protection and has been vigorously promoted.

But there are also issues with hydrolytic and oxidative stability, low temperature fluidity, and foaming

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