Indoor evaluation method for nano-plugging agent for shale gas water-based drilling fluid

Abstract

The invention discloses an indoor evaluation method for a nano-plugging agent for shale gas water-based drilling fluid. The indoor evaluation method comprises the following steps that (1) a ultra-lowpermeability stratum 'simulation core' is prepared, and the nano-plugging agent permeability reduction rate is determined; (2) particle size analysis is conducted on the nano-plugging agent; and (3) micro morphology is analyzed, specifically, firstly, the ultra-low permeability 'simulation core' (the permeability reaches 10<-4>mD) with nano and micron scale apertures is prepared successfully, thenthe permeability reduction rate of the 'simulation core' after the nano-plugging agent is added is obtained through determination of high temperature and high pressure filtration loss, the plugging performance of the nano-plugging agent is investigated, whether the size fraction magnitude of the nano-plugging agent is matched with the size of the micron and nano scale apertures or not is analyzedthrough a laser particle analyzer, finally, the micro morphology of a filter cake and filter liquor before and after the nano-plugging agent is added is observed through an environmental scanning electron microscope, the dispersion stability of the nano-plugging agent in a system is verified, and the plugging mechanism of the nano-plugging agent is further studied.

Description

technical field [0001] The invention belongs to the technical field of oil and gas well engineering, and in particular relates to an indoor evaluation method of a nano-blocking agent for shale gas water-based drilling fluid. Background technique [0002] With the increasing demand for shale gas mining, under the pressure of environmental protection and the requirements of mining costs, it has become an inevitable development trend for water-based drilling fluids to replace oil-based drilling fluids. Shale gas formations are ultra-low permeability formations (permeability as low as 10 - 4 mD), rich in nano-micron pores and fractures, easy to hydrate, especially in the process of horizontal well drilling, the filtrate of water-based drilling fluid seeping into the formation can easily cause well wall instability such as well wall collapse. Therefore, in the development of water-based drilling fluid for shale gas exploitation, it is necessary to have materials that can effect...

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Problems solved by technology

[0003] However, at present, there is no effective evaluation method for the application of nano-sealing agents in shale water-based drilling fluids in the laboratory, and it is impossible to effectively evaluate the plugging performance of different nano-materials, which greatly limits the realization of nano-sealing agents. In the application of water-based drilling fluids, especially in shale water-based drilling fluids, the establishment of an indoor evaluation method for shale water-based drilling fluid nano-sealing agents is the key. Therefore, it is proposed to establish an effective and rapid analysis of nano-sealing agents. The indoor evaluation method of plugging performance is based on the evaluation method of plugging performance of water-based drilling fluid. The low-permeability "simulated core" is obtained through the preparation of base slurry and the method of high temperature and high pressure filtration, and then the nano plugging The plugging effect can be directly obtained by measuring the permeability before and after adding the nano-blocking agent, and the plugging performance of the nano-blocking agent can be comprehensively analyzed and evaluated by combining particle size analysis and surface analysis. This evaluation method is simple and has good repeatability. , can directly and effectively reflect the plugging effect of nano plugging agents on low permeability formations, and is the basis for evaluating the application of nano plugging agents in shale gas water-based drilling fluids, and further promotes the practical application of nano plugging agents, Realize the transition from oil-based to water-based drilling fluids in shale gas production

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