Drilling Fluid Technology Suitable for Core Drilling in Deep Salt Beds

With the function of the secondary stress field and the property of salt soluble in water,problems such as formation creeping,salt and calcium contamination often arise while drilling in deep salt beds. Unreasonable drilling parameters can result in low drilling efficiency and serious core washout. In this work,drilling equipment capacity deficiency is solved by combination of oil drilling and core drilling. With the CEC test,XRD test and different kinds of drilling fluid parameter tests,this work optimized the polymer drilling fluid system,unsaturated salt water drilling fluid system and saturated drilling fluid system for drilling in shale formations,salt- bearing strata and salt beds,respectively. Performances of the drilling fluids are stable,easy to transform and adjust. As a result,the borehole washing capability is improved by controlling critical annular velocity,and penetration rate is enhanced by increasing flow rates.