A High Performance Constant Rheology Oil Based Drilling Fluid for Ultra Deep Water Drilling in Lingshui Block
Low temperature,borehole wall instability,narrow safe drilling window as well as difficulty in cleaning borehole in ultra-deep water drilling impose tough requirements on the properties of drilling fluids.In dealing with these difficulties,a new emulsifier KMUL with both emulsification and flow pattern control effects has been developed based on molecular design of emulsifiers.Use KMUL as the major additive,a high performance constant rheology oil-based drilling fluid has been developed for use in ultra-deep water drilling in the Lingshui block in the west of the South China Sea.Laboratory evaluation of this drilling fluid shows that it has good constant rheology characteristics.The rheology of this drilling fluid is stable at temperatures between 2℃and 150℃and at pressures between 0 MPa and 56 MPa.The drilling fluid has strong ability to resist contamination;when cuttings and sea water content in the drilling fluid reaches 15%,the properties of the drilling fluid are still comparatively stable.In core test,the permeability recovery of cores flooded with this drilling fluid is at least 92%,indicating that it has good reservoir protection capability.The drilling fluid has low biotoxicity and is environmentally friendly.The use of this drilling fluid on the well LS-C drilled in ultra-deep waters shows that the rheology of the drilling fluid and the electric stability of the drilling fluid in different well depths are all stable,the ECD of the drilling fluid is all the way maintained at low level.The well was drilled smoothly,the borehole drilled was a gauge hole,and no downhole troubles have ever been encountered during drilling.It is concluded that the high performance constant rheology oil-based drilling fluid has satisfied the requirements of drilling the ultra-deep water Lingshui block.
Ultra-deep water drillingEmulsifierOil-based drilling fluidConstant rheologyECD control
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