Anti-Sloughing Drilling Dluids Technology For Jiangcang Coal Exploration In Qinghai Province

Jiangcang coal field locates at Xining northwest 310km. The stratum is Jurassic coal measures, and the lithology is metamorphic bind with sandstone. It was characterized by complex geological structure, lots of fractures and folds under the influence of Himalayan tectogenesis, Specially for the hard brittle shales with a quantities of micro-fractures in this area, serious problems such as borehole instability, and pipe sticking occurred frequently during the borehole drilling. The former used water base drilling fluid had weaknesses especially the bad inhibitive ability which induced the bigger enlargement ratio of hole-diameter, abnormal borehole and also influenced the logging. Through the study of this thesis it is hoped that the reason for the borehole instability of Jiangcang mine can be found out, and excogitate a kind of anti-sloughing drilling fluids that can be well used in this area.In this thesis, it firstly analyzed the shales of Jiangcang mine in Qinghai Province and researched on the reasons for the borehole instability from the chemical aspect; Secondly, it excogitated a kind of anti-sloughing drilling fluids that can be well used in this area. This study will be good for the drawing up of borehole stability measures during borehole drilling for Jiangcang mine in Qinghai Province.The physical and chemical characteristics of shales in the formations which were liable to collapse were studied. I used the drill core which was got during the borehole drilling in Jiangcang mine to research on the technology of borehole stability, including composition analysis of clay mineral, dispersion test and so on. On the basis of the former research, the mechanism for borehole physical chemistry instability and pipe sticking were analyzed, and also the competent drilling fluids technology were putted forward, viz. enhancing the sealing and inhibitive ability. After finished the study of physical and chemical characteristics of shales, it researched on the configuration and performance of anti-sloughing drilling fluids.The research of anti-sloughing drilling fluids configuration included the selection and analysis of inhibitive agent, thinning agent, anti-sloughing agent, filtration control agent and plugging agent; The performance tests of drilling fluids included density, rheological and filtration control properties, viscosity, inhibitive character, anti-contamination property and lubricity; On the basis of optimized inhibitive agent, thinning agent, anti-sloughing agent, filtration control agent and plugging agent, excogitated a kind of anti-sloughing drilling fluids, and it was practice used in Jiangcang mine.A lot of laboratory results and on site practice showed that this kind anti-sloughing drilling fluids exhibited favorable rheological and filtration control properties, as well as inhibitive character, anti-contamination property, and can effectively seal the micro-fractures and fracture zones in the formations, and the on-site maintenance is convenient.