New Cementing Technology Eliminates Remediation, Reduces Risk, and Lowers Well Costs in the Deep Foothills of Western Alberta

摘要

The drilling of deep Foothills wells in western Alberta presents numerous challenges. Intermediate casing in these wells is typically set at 3,200 to 3,400 m TVD, but may be set as deep as 3, 600 m TVD without regulatory exceptions. Regulatory requirements dictate the need for cement at least 100 m above the top of the highest potential productive interval. It is also required that no annular gas is present at surface. To eliminate surface casing vent flows, it has been determined that nuisance gas stringers that are above the regulatory top of the cement requirement must be isolated. This has resulted in a need to bring top of cement back inside of the previous casing. Historically, operators opted to utilize a stage tool in this casing string to achieve a top of cement sufficient to meet regulatory requirements. While this approach has been successful at meeting requirements, remedial cementing has often been required to seal surface casing vent flows. A limitation of this approach is that the stage tool is exposed to periods of contact with the drillstring while the subsequent hole section is being drilled, resulting in wear and potential leaks. Development of a new high performance, low-density cement system has provided the ability to address all of the above issues. Utilization of this cement system allows wells to be cemented in a single stage with the top of cement lifted into the previous casing. This paper describes the new cement system and its application in solving the problems described above. Case histories including evaluations are provided.