Formulation And Optimization Of Ultra-high Temperature And High Density Drilling Fluid System

With the further exploitation and utilization of oil and gas resources,more and more drilling operations are carried out in strata with high temperature and pressure.In oil and gas resources producing regions such as Tarim Basin,Junggar Basin and Sichuan Basin,a large number of oil and gas resources are stored in strata with high temperature and pressure.These strata also have a high formation pressure factor.The bottom temperature is about 200℃and the formation pressure coefficient reach1.50～2.30.Drilling operation in strata with a low formation pressure factor tends to be easy.On the other hand,strata have a high formation pressure factor make it necessary to have the density of the drilling fluid increased to 2.0g/cm~3or higher to balance the pressure.In deep wells,temperature becomes an important factor affecting the quality of drilling fluid.In these drilling operations above,the drilling fluid system itself needs to be improved and has a high density.The contradiction among rheological property,settlement stability and filtration property of drilling fluid is prominent.As a result of these factors,drilling operation encountered problems such as excessive hole enlargement rate,pipe-sticking,and leakage in Permian strata and Ordovician strata.Based on these reasons above,this paper pointed out the factors affecting the performance of drilling fluid and analyzed the mechanism of action,and focused on the influence of temperature on filtration property and sedimentation stability of drilling fluid.The influence of temperature on bentonite and agents was also studyed.The morphology of barite in high density drilling fluid,the effects of the particle size gradation and the composition of the weighting material on the rheological and filtration properties of the drilling fluid were also elaborated.By testing the performance of the agent,the required additives were selected.Key additives and other additives(inhibitors,plugging agents,lubricants,etc.)were chosen.The combination of key additives and other additives was determined.The optimal dose of the additive was determined for the drilling fluid at a specific density.Finally,filtrate reducer PFL-L,high temperature resistant stabilizer SMGWW and other additives were selected out.An ultra-high temperature and high density water-based drilling fluid system with temperature resistance up to 200℃was constructed.The density of the drilling fluid system can be 2.20g/cm~3,2.30g/cm~3or2.40g/cm~3and the corresponding formula of the system was determined.The requirements for synergistic control of sedimentation stability,rheology and HTHP filtration loss were met.