A mud cake cleaning fluid for oil-based drilling fluid in shale gas development

Abstract

The invention relates to a shale gas development oil-base drilling fluid mud cake cleaning solution and belongs to the technical field of petroleum drilling engineering chemical agents. The shale gas development oil-base drilling fluid mud cake cleaning solution is characterized by comprising the following components in percentage by weight: 10 percent to 30 percent of a cleaning agent, 0 percent to 60 percent of a weighting agent and the balance of water, wherein the cleaning agent consists of nonionic surfactants and mutual solvents; the weight ratio of the nonionic surfactants to the mutual solvents is 1:9 to 9:1; the nonionic surfactants are polyoxyethylene ether, polyoxyethylene aliphatic ester, polypropylene oxide aliphatic ester and the like; the mutual solvents are methyl alcohol, ethanol, isopropanol and the like; the weighting agent is superfine iron ore powder and has density of 4.90 to 5.20 g / cm<3>. The cleaning solution disclosed by the invention has low viscosity, can form turbulence displacement, can effectively clear away oil-base slurry and mud cakes attached on a well wall and change the water wetting condition of the well wall, and has the characteristics that the density adjustable range is wide, the cleaning effect is good, and the shale gas development oil-base drilling fluid mud cake cleaning solution is beneficial to improving well cementing quality.

Description

Technical field: [0001] The invention relates to an oil-based drilling fluid mud cake cleaning fluid for shale gas development, and belongs to the technical field of chemical agents for petroleum drilling engineering. Background technique: [0002] In the process of shale gas development, oil-based drilling fluid technology and staged fracturing technology are commonly used; staged fracturing technology puts forward high requirements on cementing quality, while oil-based drilling fluid and cementing slurry are incompatible, and the cementing quality is not easy to control. [0003] In the cementing construction, if the cementing slurry is in direct contact with the oil-based drilling fluid, the cementing slurry will be polluted by the oil-based drilling fluid and produce viscous flocculation substances. After cementing slurry is polluted by drilling fluid, its fluidity decreases, and its viscosity and dynamic shear force increase, especially the increase of dynamic shear fo...

AI Technical Summary

Problems solved by technology

[0004] For the wellbore drilled with oil-based drilling fluid, a layer of dense oil-based drilling fluid mud cake will be formed on the well wall. If the mud cake is not completely removed, it will lead to poor cementation between the cement slurry and the well wall, which will affect the cementing. Quality, or even cementing failure, leading to problems such as oil and gas water channeling

However, under some special drilling conditions, a very high density is required to balance the formation pressure, which causes a contradiction between the viscosity and density of the cleaning fluid. The cleaning fluid needs turbulent flushing to achieve the purpose of cleaning. Achieving lower viscosities under conditions will be very difficult

Images