Design And Research Of Water-based Drilling Fluid In Keshen 901 Well

The formation of Keshen field is complex, the drilling fluid will lose original performance easily under the high temperature during the process of deep drilling boreholes. Which lead to downhole complexity and lengthen well construction period. Meanwhile, the exploration and development of deep oil and gas in Keshen field is reinforced in the recent years, the current drilling fluid can hardly meet the need of deep well drilling, so the water based drilling fluid system which is applicable to Keshen901 well is studied.With the higher the well is, the higher formation temperature and formation pressure is, the influenced factors and control mechanism of sedimentation stability, rheological property and filtration property of high density water base drilling fluids was investigated. It also analyses theoretically the influence of high temperature on clays, drilling additives and drilling systems. On this basis, excellent compatibility of drilling fluid additives was optimized, such as temperature fluid agent CMC-LV, anti-collapse inhibitor of KCL and NaCl, anti-collapse filtration SY-A01 and lubricant LU99, through the composition of the fluid loss agent by using CMC-LV?SMP-IIIand SPNH, the optimum dosage was confirmed. The additives of reasonable added volume and water base drilling liquid was established through indoor experiment, in consideration of abnormally high pressure, the investigate of aggravated performance of water base drilling liquid demonstrated that can be increased to 2.1g/cm3 successfully, and the rheological properties drilling fluid can meet site construction requirements. In addition, the optimal drilling fluid was evaluated from the aspects of rheology, filtration, fouling resistance, high temperature stability, high pressure stability and lubricity, and the water base drilling fluid for Keshen901 well was determined.Field results show that development of drilling fluid system has sufficient stability against temperature, resistance to high temperature 180 ?, and strong inhibition and keep the borehole stable; As a result of good sedimentation stability on drilling fluid, sticking did not happen in the process of drilling; being good rheological properties, drilling fluid easy to control and meet the requirements of construction site.