High-Angle Gyro-While-Drilling Technology Delivers An Economical Solution To Accurate Wellbore Placement And Collision Avoidance In High-Density Multilateral Pad Drilling In The Canadian Oil Sands

Abstract

Cenovus Energy initiated an aggressive infill drilling program early in 2011 in its Pelican Lake polymer/water flood project in northeast Alberta. By mid-year, the company had drilled 52 injection and producing wells, and drilling is scheduled to continue at the same pace through year-end.

Pelican Lake employs a two-phase drilling program from 18-well pads: batch-drilling the intermediate hole sections to approximately 425m MD at 70° of inclination; using follow-up rigs to drill the horizontal sections of over 2,000m in the Wabiskaw formation. Wellbore collisions in the intermediate phase and landing the wells accurately prior to horizontal drilling are critical concerns. Highly accurate gyroscopic surveying techniques are required throughout the project considering the close well spacing and congestion of existing wells.

Early in 2011, the company tested a new gyro-while-drilling (GWD) system, capable of accurate performance up to 70° of inclination versus the 20° to 40° of previous models. If successful, the higher operational range would facilitate collision avoidance and accurate well placement in one operation with real-time data, potentially enhancing both the economics and the feasibility of the drilling program.

Since accurate well placement was so critical—some well passes would be as close as 4 meters—the company developed a plan to evaluate the new tool: first, by surveying previously surveyed wells and comparing the results; and, second, by running back-up gyro surveys on wireline during drilling. GWD performance exceeded expectations, both in the initial tests and in the drilling operations—to the extent that the back-up surveys were eliminated, with the GWD data accepted as the definitive wellbore survey.

This paper will provide the results of the initial tests and analyze GWD performance during drilling with statistics compiled from 36 wells. The savings from eliminating the back-up surveys will be presented along with other benefits and observations.

Introduction

Cenovus began development of its wholly-owned Pelican Lake heavy oil field in 1997, located approximately 300 km north of Edmonton, Alberta in the Greater Pelican Region.

Drilling targets the Cretaceous Wabiskaw formation, which consists of unconsolidated sand layers at a depth of approximately 400m and with a total thickness of 6-7m (Figure 1). After years of successful water-flood operations, in 2006 the company initiated a polymer-injection program to increase declining production. These and other enhancement techniques in this technology-driven resource have produced overall field production rates as high as 30,000 bpd.

By 2010 production had declined to 23,000 bpd, with further declines to 21,000 bpd in early 2011 as anticipated. As a result, the company has initiated an aggressive multi-year infill drilling program to expand the polymer-injection throughout the field—with an expectation to more than double production to 55,000 bpd by 2017.