Research Of The Water-base Drilling Fluids With High Density And Temperature Resisting And Salt Tolerance

Queerqueke formation in Shun Nan block has a serious falling collapse and aproblem of bore-hole stability and the geothermal gradient is high,during the drilling the salty water intrudes into the drilling fluid,there is an anomalous pressure in the well.This paper does the research for the anti-temperature and salt-resistant and high-density drilling fluid in Shun Nan block.Do the lithology analysis of the Queerqueke formation by the X diffraction method and scanning electron microscopy,and do the determination of the physical and chemical properties for the rock,they show that the mineral content varies with the depth of the well and the collapse of the well is mostly weakly dilute.Intergranular development,microfracture development is the main reason leading to the instability of mudstone formation.The drilling fluid should has strong inhibition and salt tolerance.Most of wells in Shun Nan block are deep.Deep well drilling has a higher demand for the performance of drilling fluids.Due to the presence of geothermal gradients,the high temperature performance has become the basic performance of deep well drilling fluids.With the increase in drilling depth,formation pressure is increasing,which requires drilling fluids to have a high density to balance formation pressure.The common treatment agent of drilling fluid is screened by single factor optimization experiment and the drilling fluid system was established by orthogonal test,finally set up a water-based drilling fluid system with composite cost and few agents,the temperature resisting of the system is 190?,the density is 1.9g/cm3,and the salt resistance of the drilling fluid is 20%.The drilling fluid composition:2.5%attapulgite+0.25%Na CO3+0.55%Na OH+2.0%DS-302+1.8%RHPT-2+4%SMC+6%SPNH+0.8%HPA+1%JM-2+3%RHJ-3+20%Na Cl+barite.The comprehensive evaluation results show that the drilling fluid system has good anti-high temperature performance,and it has good rheological property and filtration properties at high temperature,the drilling fluid system has excellent lubricity,anti-collapse andblocking ability,strong resistance to salt and calcium to meet the needs of drilling in Shun Nan deep well drilling.