| With the development of unconventional oil and gas reservoirs such as shale gas,the demand for oil-based drilling fluid continues to increase.The cost of base oil accounts for more than 40%of the cost of oil-based drilling fluids,and base oil accounts for nearly70%of the composition of oil-based drilling fluids.During 2019,about 500,000 m~3 of oil-based drilling fluid base oils were consumed with the development of shale gas in Sichuan,Chongqing and Xinjiang regions,the cost was as high as more than$24 billion.Therefore,the cost of oil-based drilling fluid is mainly achieved by controlling the cost of base oil.12 kinds of naphthenic crude oil distillates and light white oils were selected as raw materials to study the influence of base oil properties on drilling fluid performance in this paper.According to the relationship between the viscosity,distillation range and hydrocarbon composition of the base oil and the PV,YP,HTHP and ES of the drilling fluid,the mathematical correlations were established and the suitable datas of properties for the base oil were determined.The results showed that PV,YP and ES of oil-based drilling fluids increase with the increasing of base oil viscosity,and HTHP decreases with the increasing of base oil viscosity.In order to ensure the excellent performance of the oil-based drilling fluid,the properties of the base oil are controlled as follows:IBP>reference,FBP<reference+100°C,reference<υ40<reference+1 mm~2/s,lower content of aromatic hydrocarbons,the reference content of paraffins and naphthenes.On the basis of the above research conclusions,the base oils were selected and the properties were optimized,and three kinds of oil-based drilling fluid base oils were obtained:base oil A,B,C.The performance evaluation results showed that drilling fluid having better compatibility with the existing drilling fluid system and lower cost were produced by the improved process using the three kinds of base oils.Repeated test results showed that the field test requirements can also be met.On the basis of the above research conclusions and evaluation results,the special base oil standard for oil-based drilling fluid was formulated.And the production of base oil was carried out in the industrial unit of lubricating oil high pressure hydrogenation.The DBN-100 drilling fluid was formulated with this base oil and the field evaluation tests were carried out.The application results showed that the drilling fluid exhibited excellent inhibition,rheology,stability and low temperature resistance,which overcame various construction difficulties and ensured the normal drilling operation. |
