Intelligent blocking water-based drilling fluid

Abstract

The invention relates to intelligent blocking water-based drilling fluid. The intelligent blocking water-based drilling fluid comprises, by weight, 100 parts of seawater or fresh water, 1 part to 5 parts of sodium bentonite, 0.2 part to 1 part of pH regulating agent, 0.5 part to 2 parts of fluid loss agent, 0.1 part to 0.6 part of flow pattern regulating agent, 5 parts to 25 parts of water activity regulating agent, 1 part to 4 parts of blocking agent, 1 part to 4 parts of blocking anti-collapse agent, 1 part to 3 parts of shale inhibiting agent and 0.2 part to 1 part of shale encapsulating agent. The intelligent blocking water-based drilling fluid can flow into a stratum along with filter liquor and can be intelligently matched with cracks and holes in shape when encountering stratum water to fill space and be cemented with stratum matrixes, a compact and firm integral structure can be formed, the porosity and the permeability can be reduced, and further invading of the filter liquor can be prevented; meanwhile, the strength of the stratum can be improved, and the stratum stability losing problem can be solved; in addition, compared with oil-based drilling fluid, the intelligent blocking water-based drilling fluid is more environmentally friendly and lower in cost.

Description

technical field [0001] The application belongs to the technical field of drilling fluid for petroleum development, and relates to an intelligent plugging water-based drilling fluid capable of stabilizing mud shale well walls. Background technique [0002] Wellbore stability is closely related to drilling fluid filtrate invasion or loss. It is generally believed that large losses are difficult to plug while small losses are easy to plug. Therefore, little attention is paid to small drilling fluid losses during development operations. However, the fact is quite the opposite. The smaller the leakage, the more difficult it is to control, such as the flood control levee collapsed in an ant nest. The pore size of mud shale is usually several hundred nanometers to several microns, and the permeability is Nadarcy level (K=10 -21 ~10 -9 D), usually saturated by formation water, incompressible, so a very small amount of intrusion can also greatly change its stress balance state, mak...

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Problems solved by technology

[0003] In China, technical measures such as strong suppression, strong plugging, and film-forming plugging are mainly used to deal with shale well wall instability. The essence of which is to emphasize external sealing, but the ability to penetrate deep into the shale is limited or even powerless, that is, it is difficult to pass through the shale. Change the properties of the matrix formation itself (permeability, strength), to delay or prevent the filtrate from invading into the formation, and achieve the purpose of long-term stable performance of the formation

[0004] In addition, oil-based drilling fluids are commonly used at home and abroad to solve the problem of shale wellbore stability, but the preparation cost of oil-based drilling fluids is high, and the risk of environmental pollution is high. With the increasing emphasis on environmental protection in various countries, its application is becoming more and more restricted. Therefore, it is the main direction to vigorously develop water-based drilling fluids whose performance is close to oil-based

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