KELLER, W. RAY, C&D Oil & Gas Ltd., Calgary, Alberta, Canada, and LARRY HERD* and FRANCIS LEE, Boyd Exploration Consultants Ltd., Calgary, Alberta, Canada
This is a case study of a lower Cretaceous channel sand oil pool integrating geological subsurface information and 3-D seismic data. This study is timely because several channel sand oil pools have recently been discovered in the area, and 3-D seismic is being used to target prospects, pick wildcat locations, and to pick development well locations. Advanced interpretational aids including 3-D Inversion and 3-D AVO Analysis are applied to attempt to delineate subtle stratigraphic features.
The Cameron Sand oil pool in Sec. 16, 17, and 20 of TWP 40, RGE 10 W4th Meridian in the Choice area of the Provost field, Alberta, is accumulated in several stacked point bar sands and overlying overbank and/or crevasse splay sands. These sands were deposited by a river system whose source was the Canadian Shield to the east northeast in Saskatchewan that meandered westward over an estuary terrain of basal Cretaceous clastic sediments infilled on an irregularly eroded Paleozoic angular unconformity.
The 10-17 discovery well was drilled in November 1969, but the 16-17 BQ confirmation well 320 m northeast of the discovery was not drilled until September 1983. The pool was extended northwest into Sec. 20 in May 1984 and southeast into Sec. 16 in June 1987. In mid-1991 the pool was averaging 1600 bbl/day from 27 wells, one of them the 3-20 horizontal well with 275 m of oil sand open in a slotted liner. There were six additional oil wells capable of 280 bbl/day awaiting completion of battery construction. The 7/1/91 cumulative production was: oil, 1,194,937 bbl; gas, 134,848 mcf; and water, 4,764,689 bbl. The average net oil pay is 25 ft; maximum net oil pay is 44 ft. The pool has approximately 450 productive acres extending 1 3/4 mi wide in an arcuate shape bowed to the southwest tow rd an inferred river cut-bank zone. When the present well infill program is completed, well spacing will be 10 acres per well.
A 3-D seismic program covering most of Sec. 17 and parts of Sec. 16 and 20 was acquired using Vibroseis to help pick additional development well locations and define pool limits. Previous 2-D seismic had been used to map the gross structural characteristics of the pool. These data proved to be unreliable where a Coal Marker reflection above the objective zone was obscured with complex multiple problems and the stacked porous point bar sands were replaced laterally by nonporous, nonproductive acoustically similar sediments.
Some 16 additional well locations were picked using the 3-D seismic integrated with subsurface well data, including a horizontal well. Subsequent drilling results have been mixed with the failures related mostly to unexpected loss of net oil sand pay off the top of the objective section. Efforts are now underway to incorporate seismic inversion of the entire 3-D data volume and AVO analysis of the volume to assist in the descrimination of the full stacked sand section from the nonproductive portion of the channel.
AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)