This paper describes the development of operating strategies and production performance predictions for horizontal wells drilled from a tunnel as well as surface deviated horizontal wells in combination with vertical wells. Scientific Software Intercomp's Steam and Therm model were used for the studies. The reservoir considered in this investigation had characteristics similar to the Athabasca McMurray formation. Steamdrive was used as the primary recovery process.
Three configurations were studied. The first configuration involved two 150 m long horizontal wells spaced 60 m apart. Computer model studies led to the development of an effective operating strategy with an oil production capability of about 22 m3/d and an SOR of 5.5. Predicted oil recovery was 58% of the original oil-in-place in a seven year operation. The second configuration studied involved a horizontal well (300 m long) and a vertical well in communication with it. With steam continuously injected into the horizontal well, the vertical well produced at a rate of approximately 12.5 m3d of oil at an SOR of 8.6 for about 6 years. The third configuration had a horizontal well with two vertical wells in combination with it to create a heated plane aver the horizontal well. In this case, Butler's concept of a steam chamber and gravity drainage was modelled. The horizontal well was 400 m long with two vertical wells located over it, equidistant from its two ends. The modelling study showed that continuous steam injection into the vertical wells resulted in horizontal well oil production capability (after initial stimulation) of about 50 m3/d with an SOR of 8. The well life was calculated to be 7.5 years.
In 1978 Petro-Canada, as operator for a five party group including Esso Resources Canada Ltd., Husky Oil Ltd., Canada Cities Service (now Canadian Occidental Ltd.) and Gulf Canada Ltd. initiated the MAISP Project at an outcrop near Fort McMurray. Three horizontal wells were drilled and completed in the oil sands. The purpose of this surface demonstration was to investigate the feasibility of horizontal well drilling and completion to increase confidence in proceeding to an underground test and to obtain data for the design of an underground test. This test project demonstrated that long horizontal wells could be successfully drilled, completed and operated. Though the production was a secondary objective of the project, the production results were also encouraging. During production, two modes of steam operation were tested, hot finger stimulalion and steamdrive. After about a month of operation in the hot finger mode, interwell communication was achieved between two wells spaced 8 m apart. The pilot was abandoned after one and one half years of operation(1)). Because of the success or the pilot, computer simulation and design studies were carried out in-house to further explore the potential of horizontal well processes for recovering oil from the Athabasca oil sands deposits.
This paper deals with a study of three configurations of horizontal and/or vertical wells.