A Research On Sidewall Invasion Depth Of Drilling Fluid

During drilling process, drilling fluids generally penetrate into the sidewall for a certain depth under positive differential pressure. Invasion of drilling fluids not only pollutes the reservoir, decreases the production, but also affects logging responses in various degrees, which results in multiple logging interpretation and even wrong analysis. Controlling sidewall invasion depth of drilling fluids is an important measure to protect the reservoir in perforated completion. With shield and temporary bridging technology as the core, a series of innovative drilling fluid technologies are supposed to control the sidewall invasion depth of drilling mud effectively. Measuring the sidewall invasion depth of drilling fluid can prove the practical positive result of drilling technology and improve reservoir protection technology objectively.There are many technologies to measure the sidewall invasion depth of drilling fluids. But the oil company is facing the pressure to decrease the drilling investment. A lot of conventional logging services have been reduced or totally cancelled. This article mainly elaborates the research to seek a low-cost, simple and convenient technology to measure the sidewall invasion depth of drilling fluid.When drilling fluid penetrates into the porous formation, a fluid interface is formed. The edge of this interface is comparatively clear after the formation is drilled. At this time, between the invaded zone and the non-invaded zone, a reflection interface is formed to reflect the high frequency electromagnetic wave. In the non-magnetic media, electric conductivity and electric constant of fluid-bear rocks are decided by quantity and electric conductivity of water in pore space. So primary parameters of rock physical property that affect electromagnetic wave travel are electric conductivity of drilling fluids, electric conductivity of formation water and water saturation.