Successful drilling technology must satisfy three key factors: increase production, help replace reserves, and reduce costs. Two technologies capable of this are liner drilling and managed pressure drilling. No company has exploited these complementary technologies in one project, until now. In an industry first effort, Shell tested both to improve access to, production from, and reduce cost in a proven, depleted, south Texas gas field.

It is difficult to predict the depletion level in the reservoir sands of the McAllen-Pharr field due to the complex geology and complicated production history. While trying to reach deeper reservoir targets, large differentials between the hydrostatic pressure and depleted sand formations resulted in excessive drilling costs due to lost circulation, differential sticking, and unplanned sidetracks.

Shell turned to underbalanced casing and liner drilling technology for a solution. However, unlike Shell’s other south Texas fields, the quality of the reservoir rock in McAllen-Pharr is such that the wells will flow when underbalanced, such as during a connection. During liner drilling on previous wells in the field, Shell personnel had to manually manage backpressure through the rig’s well control equipment for prolonged periods of time, which confirmed the need for pressure management technology.

Shell selected an automated Managed Pressure Drilling system and tested its ability to eliminate losses and stuck pipe in three wells in the McAllen-Pharr field, drilled both with liner and conventional pipe. A firm commitment was made to test and evaluate these complementary technologies in an aggressive and challenging drilling program.

The results of this drilling improvement initiative produced an optimum solution for an area that for many years has been plagued by high drilling costs. It also led to the development of a new, more mobile, automated pressure control system, optimized for land, with reduced rig up time, smaller footprint, and reduced manpower.