Study On Anti-collapse Drilling Fluid Technique For BZ13-1 Oilfield

With the development of oil exploration, the scale of offshore oil development willexpand. Bozhong 13-1 oilfield is located in Bohai Bay Basin, complex downhole troubleslike borehole collapse, well kick, trip sticking, drill pipe sticking, bit balling and mud ballblocking pipe were encountered during the early drilling process which severly influenced thedrilling speed and benefit. In order to achieve annual oil and gas output of 30 million tenthousand tons project in Bohai oilfield of CNOOC by 2010, Bozhong 13-1 oilfield beganlarge-scale drilling in 2009. The geological conditions of Bozhong 13-1 oilfield iscomplicated with narrow saftety-density window. There were different degrees of boreholeinstability, lost circulation and other troules in previous three exploration well drilling, andthe lost time accounted for 21.56% of total drilling time. This not only caused huge economiclosses, but also seriously delayed the process of oilfield construction. To ensure successfuldevelopment of the oilfield, it's necessary to synthetically research and analysis the formationcharacteristics of Bozhong 13-1 oilfield, probe the mechanism of wellbore instability andfurther optimize anti-collapse drilling fluid system.In view of complex conditions like wellbore instability, sticking and lost circulation inMinghua Zhen formation, Shahe Jie formation and Dongying formation of Bozhong 13-1oilfield, wellbore instability mechanism was researched through XRD, shale swelling test,shale rolling and dispersion test, CEC, surface area test and specific water amount test. Basedon integrated analysis the specific anti-collapse techniques were proposed and the maininhibitive mechanism of drilling fluid was researched. High perofrmance anti-collapsedrilling fluid system was developed by experiments and achieved good field test results. Thiscan make an important reference for drilling fluid anti-collapse technology in other oilfieldslike Bohai Bay.