A Study Of Emulsion Stability Mechanism Of Oil Based Drilling Fluid

Petroleum is an important resource and high grade fuel, drilling fluids is closely related to drilling engineering. Water-in-oil drilling fluids is a fluids with strong inhibition to stabilize the borehole wall and inhibit the shale, especially suitable for complex water sensitive formation conditions, has good lubricity, extremely salt-resistant and cuttings-resistant. This characteristics of the drilling mud can be recycled and in-site maintenance is simple, and now it has become an important means of drilling high temperature deep wells, highly deviated directional wells, horizontal wells, a variety of trouble wells and reservoir protection.Water-in-oil invert emulsion drilling fluid is an unstable thermodynamics system, a variety of treatment agent in the system plays the varying degrees of impact on the water-in-oil emulsion stability, by its properties is a topic that needs further study. In this paper, this has done some research.The emulsifier is a key factor to determine the emulsion stability. The properties of the emulsifier create the emulsion type, the correct choice of the emulsifier is the key to the stability of the emulsion system. The main role of the emulsifier is to reduce the interfacial tension,to form adsorption film surrounding with the internal phase droplets, to prevent the droplets coalescence and oil-water separation. The higher of oil-water interfacial film intensity, the more stable the emulsion. This paper examines the relationship between emulsion stability and the external phase of the required HLB value, the compound emulsifier how to affact the oil-water interfacial film, the use of a centrifuge such as demulsification means, with the microscopic state of the optical microscope observe the emulsion droplet. In addition to the conventional electrical stability evaluation methods, including the emulsification efficiency and water-separation rate in the evaluation of emulsion stability. As the emulsion base fluid component, internal and external phase viscosity value raise, more solid phase increased will influence the system oil-water ratio, the trend of emulsion become more stable.Due to friction, the dispersed droplets take charge, the increase of the concentration of inorganic ions helps to reduce the charge density of the interfacial film, the compression of electrostatic double layer thickness, ionic valence and hydrated ionic radius in connection with emulsion breaking. With optical microscopy and scanning electron microscopy and other analytical tools for structural characterization of three type organic clays, the steric configuration of organic clay in external phase and a combination with the dispersed droplets also play a key role in the stability of the emulsion. The wetting agent can change the wetting contact angle of the solid surface, the ideal condition for the solid phase is oil-water neutral wettability, the state of the emulsion show more stability. Fluid loss control agent granula form asphaltenes membrane covering the oil-water interfacial film to increase film thickness and toughness.In addition, the structure and electrical property of high density weighting material in the system,and circulation temperature of mud also impact the stability of the water-in-oil emulsion. drilling fluidAt this stage, understanding of the mechanism of the treatment agent role in the water-in-oil emulsion system is not enough, this paper has used some experimental methods to better understand the mechanism of water-in-oil emulsion drilling fluid treatment agent, can be helpful to maintain the performance of the emulsion drilling fluid system during in-site drilling, and environmental protection.