Wellbore stability of cationic emulsified asphalt
With water-based drilling fluids, wellbore instability problems are often encountered. Because shale contains water-sensitive clay minerals, hydration expansion of shale due to intrusion of water causes the wellbore to shrink or expand, eventually resulting in the wellbore collapse. It is said there are many additives to stabilize the well wall. One of the asphalt blocking agent due to lower cost, better application effect, has been the most commonly used type of drilling fluid anti-collapse agent. With the development of the micro-mechanism of muddy shale / drilling fluid interaction and the research of chemical-mechanical coupling borehole wall stability and the establishment of muddy shale semipermeable membrane theory, the development and application of high performance asphaltic drilling fluid stabilizer Application more and more attention. In recent years there have been reports of cationic emulsified asphalt. The degradation rate of shale of cationic emulsified asphalt DHJ developed by North China Petroleum Administration Drilling Technology Research Institute is more than 40%, the rate of decrease of adhesion coefficient is more than 60% and the stability of emulsion is over 90 days.
The effects of different components in the cationic emulsified asphalt formulation on the stability, hydration and dispersion properties, and the inhibition of expansion of shale were evaluated through laboratory experiments. The synergistic effects and their synergistic effects were also evaluated. The effects of cationic emulsified asphalt and Other asphalt drilling fluid anti-collapsible agent comprehensive performance, studied cationic emulsified asphalt DHJ wall stability mechanism, obtained its different from the role of ordinary asphalt sealing agent.
① cationic material modified emulsified asphalt synergistic effect. Due to the strong adsorption of cationic materials and clay minerals in the emulsified bitumen particles, the positively charged bitumen particles can replace the adsorption of water on the clay mineral surface and firmly deposit on the surface of clay minerals to form a hydrophobic film, which can retard water Molecules penetrate into clay minerals. The positively charged bitumen particles are adsorbed on the surface of the clay cement after they enter the pores of the formation, the micro-cracks or the clay layer, and the cationic cations on the clay surface are pushed out to reduce the cation activity on the clay surface, thus weakening the penetration of the clay Hydration.
② Emulsified asphalt nonionic surfactant - Polyether molecules have many ether linkages, these ether bonds compete with the water molecules adsorbed on the clay surface, the polymer molecules can be well adsorbed on the shale. During the drilling process, the asphalt emulsified particles enter the shale pores, micro-cracks or adsorbed on the surface of the shale. Due to the adsorption effect of the shale on the asphalt emulsifier, the asphalt emulsion breaking coagulates to form a film. This asphalt film toughness Large, good water barrier, not water erosion, can effectively hinder the free water penetration to the shaft wall. Cationic emulsified asphalt is a new kind of anti-collapse agent for bituminous drilling fluid. It highlights the comprehensiveness, diversity and synergy of anti-collapse effect. Therefore, it is clear that the wellbore stability mechanism can provide theory for its application basis.
Shaoxing Shangyu Simo Research institute of organic Chemistry
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