Controlled Pressure Drilling and Downhole Isolation Valve Technologies for Enhancing Coal Seam Gas Drilling and Completion Operations in Australia

摘要

The use of controlled pressure drilling (CPD) techniques in tandem with downhole isolation valve (DIV) technologies to improve drilling and completion operations for coal seam gas (CSG) in Australia has yet to be maximized, especially for wells that are drilled into dewatered coal formations where reservoir pressures are below sub-hydrostatic levels and cannot be drilled conventionally as circulation losses would result. Advancements in rotating control devices (RCD) and CPD technologies where backpressure is exerted on the annulus of the well during drilling in order to control the bottomhole pressure while drilling with air, mist or foam fluid systems have increased their potential to enhance the drilling process. The utilization of a DIV to keep the well underbalanced during tripping and when the completion assembly is ran minimizes the pressure spikes that the inherently unstable coal formation sees and helps ensure that the completion is ran to the ideal depth and maximum production is realized. Together, CPD and DIV solutions can improve the economics of CSG wells in Australia. Case studies of previous deployments involving a tandem application of these technologies and their impact will also be discussed.