Abstract: 3-D Seismic as a Development Tool: A Case Study from Provost, Alberta

Beth Rose, Bill Cameron, David Mackie

An east-west trending Cretaceous paleovalley system can be mapped along a length of 130 km in East-Central Alberta. This valley is four to five km in width and contains up to 30 m of reservoir quality sandstone and interbedded shale. Along the length of the system, 16 economic pools cumulatively contain 137,000 × 10³ cu m of oil in middle to lower Mannville sands, making exploration for these targets extremely attractive.

In July, 1991, evaluation of 2-D seismic coverage resulted in the drilling of an exploratory well which encountered 8 m of medium gravity oil pay in the Lower Cretaceous, at a depth of approximately 950 m. Further evaluation of the 2-D data indicated that the anomaly extended over four km in length. Land was acquired, and a second exploratory well was drilled. Based on the results of the second well, a 19-sq km 3-D survey was acquired in November 1991.

Initial interpretation of the data was based primarily on drape on a coal marker overlying the producing zone. A character change between reservoir and non-reservoir facies was noted, as well as a slight structural high on a reflector near the top of the sand. The completed interpretation showed a boomerang shaped feature 4 to 5 km in length and 0.5 to 1 km in width. Based on the 3-D survey, an 8 well delineation drilling program was proposed, the results of which proved that a continuous pool existed over the length of the anomaly. A development drilling program of 80 wells, employing four hectare spacing and pad drilling technology, was completed within seven months.

As the drilling program progressed, the interpretation of the seismic program was continually reviewed. When well results failed to correspond with our interpretation, we were able to modify the interpretation and continue drilling without interruption.

As of October, 1993, approximately 193 wells, including 165 oil wells, have been drilled into the pool in five major phases of drilling. The reservoir sandstones are interpreted as a point-bar deposit, and are characterized by excellent porosity (30%) and permeability (1-5 darcies).

The use of 3-D seismic technology has aided in the efficient and timely development of this pool. Better imaging of our drilling target allowed the advance planning of the large number of wells, minimizing changes to the drilling program once it was underway. but giving us the flexibility to quickly evaluate drilling plans when necessary. This case study is a clear example of how 3-D seismic can reduce the costs, risks and time associated with a major development program, and improve the overall net present value of the project.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994