Abstract

Conventional open-hole and cased-hole logs, such as the Continuous Carbon/Oxygen (C/O) log, have been used to evaluate steam displacement and sweep efficiency of aheavy oil recovery project in the McMurray Formation, located in Northeastern Alberta, Canada. Results of this reservoir evaluation and steam drive monitoring are presented based on the study of five field wells. This heavy oil recovery project is unique because the reservoir is produced by means of a horizontal well system in which [he heated oil drains by means of gravity segregation.

Introduction

The MAISP (Mine Assisted In-Situ Pilot) Project was a joint venture by Petro-Canada, Esso Resources, Cities Service Canada, Husky I and Gulf with Petro-Canada acting as operator. The pilot was located approximately 50 kilometers north of Fort McMurray, Alberta at Syncrude in Canada's Lower Base Camp along the Athabasca River on the Northern corner of Suncor's Oil Sands Lease 86.

The initial objective of the pilot was the drilling and completing of three horizontal wells from the underlying limestone up into the lower McMurray Formation which lies uncomfortably on top. This was accomplished by digging a 20 meter deep pit into the limestone at the base of a hill. From there the wells, which were eight meters apart, were drilled and completed to a depth of 310 meters into the race or the hill. (see Fig. 1) Six vertical observation wellswere then drilled at the top of the hill back from the face in a pattern as shown in Figure 2. The wells were numbered 0–1 to 0–6, and they were drilled vertically to a depth or 85 meters which put them about 20 meters into the limestone. The wells were used as temperature monitoring wells.

Because of the very low gravity of the oil, 7 ° – 9 ° API, steam was used to heat the reservoir to produce the bitumen from the bottom 15 meters of the lower McMurray Formation. The pilot ran for approximately 16 months and steam injection was shut down in March 1981.

In April 1981, eight post steam boreholes were drilled on top of the hill back from the face in a pattern as shown in Figure 2. The wells (B-1 through B-9) were drilled specifically for the purpose of evaluating the reservoir after steaming. B-5 was nor drilled due to surface location problems. All the boreholes had temperature logs run 24 hours after drilling. Two of the boreholes, B-1 and B-4, were logged with a Compensated Neutron/Density combination and were cored. In five of the eight wells, the continuous Carbon/Oxygen log was run. The wells were B-1, B-4, B-6, B-7 and B-B.

RESERVOIR DESCRIPTION

The McMurray Formation of Lower Cretaceous age is a member of the Mannville Group. The McMurray consists mainly of fine to coarse sand with silt and shale interbedding. It lies unconformally on the Deyonian and is overlain by the Clearwater shales. The McMurray oil sands have a great aerial extent (see Fig. 3) and contain vast quantities of bitumen (as much as 900 billion barrels).

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