Optimum Selection Of Drilling Fluid System In At Wellblock, Tahe Oilfield

The stratum of AT well block in Tahe oil field is typical sand and mudstoneinterbedding. It has the property of easy expansion of strong dispersion. The contentof clay mineral in AT well block is high and the water sensitivity is very strong.Borehole instability and other Downhole complicated conditions are frequentlyoccured. So the promotion of research on drilling fluid to seek a system which has theproperty of strong inhibition, anti-collapse drilling and environmental protection isvery necessary.This paper promoted the study of drilling fluid for clastic rocks in AT wellblock.We studied the borehole stability of AT wellblock through five susceptibility test,mineral analysis of the whole rock and scanning electronic microscope. This paperintroduced a new treating agent. of We proceed the performance evaluation anddosage optimization on the main treating agent using the experimental method ofcuttings roller recovery, spectral analysis and testing the expansion and disperse of theshale. Finally, we acquired the optimal formula of cationic emulsion polymer drillingfluid adopting orthogonal experimental design.The main research achievement of this paper is:First, we completed the physicochemical property analysis of clastic rocks in ATwellblock. The results show that the stratum of AT well block in Tahe is typical sandand mudstone interbedding. The content of clay mineral in AT well block is high andthe water sensitivity is very strong. So a drilling fluid system which has the property ofstrong inhibition, anti-collapse drilling is very necessary.Second, we evaluated the performance of the new treating agent, RHTP-1. Thefiltration property of our own new filtrate reducer is very good. Its resistancetemperature can reach200℃.And it is also capable in saturated salt-water drillingfluids.Third, we evaluated the performance of the main treating agents and optimizedthe dosage. The rejection capability of DS-301is very strong and the rejection ofdispersive capacity is better than other anti-collapse agents.Fourth, the optimal formulation is:3%swelling Soil+0.5%DS-301+1%RHTP-1+2.5%RHJ-3+0.7%HPA+0.5%DS-302+1.5%RHJ-1+5%KCl+3%CaCO3。Andthe experimental results show that the system has the property of high temperatureand salt resistance, rejection capability. This system can satisfy the requirement of theclastic rock formation drilling safety construction.