Film formation blocking agent for shale gas formation drilling fluid and preparation method thereof

Abstract

The invention discloses a film formation blocking agent for shale gas formation drilling fluid and a preparation method thereof. The film formation blocking agent for shale gas formation drilling fluid is prepared from the following ingredients in parts by weight: 20 to 50 parts of styrene, 3 to 20 parts of acrylic acid, 5 to 30 parts of butyl acrylate, 2 to 10 parts of cationic monomers, 1 to 10parts of emulsifying agents and 1 to 5 parts of 2,2,4-Trimethyl-1,3-pentanediol 1-Monoisobutyrate under the effect of initiating agents; then, the pH is regulated; white emulsion with blue light is obtained. The film formation blocking agent for shale gas formation drilling fluid has broad spectrum; nanoscale microporous seams can be blocked; the effective blocking on micron grade seams through the film formation effect can be realized; a large number of cationic groups are contained and can be adsorbed on a clay crystal layer, so that the well wall and rock debris adsorption and coating effects can be achieved; a film is formed at the surface, so that the microporous seams are blocked; the water and the drilling fluid are effectively prevented from penetrating inside the formation and therock debris; the well wall collapse is prevented; the well wall stability is stabilized; the influence on viscous shearing force is little; the deformable performance is realized; good blocking and filtrate loss reduction effects are achieved.

Description

technical field [0001] The invention relates to the field of shale gas formation drilling engineering, in particular to a film-forming plugging agent for drilling fluid and a preparation method thereof. Background technique [0002] Micro-pores / micro-fractures, bedding, joints and interlayers are well developed in shale formations; the bedding surface has low cementation strength and is rich in bio-fossils, and the drilling fluid filtrate easily invades the formation along micro-fractures / beddings; the invasion of filtrate makes micro-fractures Spread, dilate, and form a suture network. At the same time, the intrusion of filtrate will generate strong hydration stress, weaken the strength of formation rock, further deteriorate its structural integrity, and cause the wellbore to become unstable. During on-site construction, it is usually necessary to add an appropriate plugging agent to the drilling fluid according to the characteristics of the pores and fractures of the form...

AI Technical Summary

Problems solved by technology

At present, the size of conventional plugging agents (such as bituminous plugging agents, emulsified paraffin, etc.) is too large for this type of micro-cracks, and cannot achieve a good plugging effect, while nano-blocking agents can only effectively plug them. Part of the nano-scale micropores whose size can match cannot be effectively blocked for micron-scale micropores

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