Drilling fluid development of ultra-thick coal seam and its application in Yining-1 well

Elastic mudstone and carbonaceous mudstone Xishanyao formation and Badaowan formation are interbedded with multiple sets of thick coal seam,with poor cementation,developed micro-fractures and easy to be shattered and collapsed characteristics.In order to solve the problems,the polysulfonate drilling fluid system of the temperature resistance,strong sealing inhibition against the collapse has been developed.Field application indicates this drilling fluid system is of strong temperature-to-resistance inhibition,with good effect of lubrication collapse prevention,stable performance,and low filtration capacity under high temperature and high pressure.It can effectively control the detrital mudstone swell reducing and mud making and coal and carbonaceous mudstone collapse,smoothly drilled through the distribution between 3 194~4 540 m178 m thick coal seam and 26 carbonaceous mudstone layer.In the process of drilling,the hole is of stability,running smoothly and without severe drill stuck phenomenon,and the electronic logging is successful for the first time.