The Western Canadian Sedimentary Basin (WCSB) is dominantly a gas-bearing basin, particularly in the western and northern regions. With the major fluctuations in gas prices over the past year, it has become increasingly difficult to determine the economic viability of exploring for and developing natural gas reserves within the basin. Each geographic area within the WCSB has its own economic criteria from the relatively inexpensive low reserve, low deliverability shallow gas of southeastern Alberta to the high reserve, high deliverability of Western Alberta and Northeastern British Columbia. To compare which plays are economically more attractive, a detailed analysis must be done to statistically compare the risk factors, the ultimate reserves and deliverability for each gas-bearing horizon. In addition a full cycle economic model must be constructed in order to determine the future economic viability of each play. To predict how future wells will perform, the statistical database must be based on the most recent drilling; however, success, reserves and deliverability trends through time must also be investigated.
The current model subdivides the WCSB into thirteen geographic areas and related gas-bearing horizons. Statistical success rates, ultimate reserves and deliverabilities for current gas wells have been determined for each gas-bearing interval through time. Data from the last five years is then utilized to predict the risked and unrisked reserve and deliverability distribution for future wells within each geographic area. An economic model using land, seismic, capital and operating costs compares gas plays, prospects and acquisition opportunities across the WCSB.
The full cycle economic viability for all productive natural gas formations ("gas plays" ) in the Western Canadian Sedimentary Basin ("WCSB" ) can be determined using publicly available geological, land, and production data. This paper represents a summary of the processes utilized in a larger regional study performed by the consulting firm Ashton Jenkins Mann (AJM) in 2001. The regional study utilized various parameters for the gas plays resulting from an unbiased statistical analysis of all wells drilled during the past five years within the WCSB. Results were reported for both risked (Exploration and Development) and unrisked (Development) cases.
The area investigated in the regional study includes all productive natural gas formations in Western Saskatchewan, Alberta and Northeastern British Columbia. The basin was subdivided into thirteen (13) geographic areas (Figure 1). The geology and production characteristics vary significantly over such large areas, thus within each area a series of "Stratigraphic Intervals" were defined to group similar geologic formations together, based on chronological age, lithology and production characteristics (Figure 2).
For each stratigraphic interval in each geographic area the following techniques and financial parameters were summarized to determine the economic viability of each productive interval within the WCSB:
Success factors
Reserves per well
Initial production per well
Capital expense per well
F &D costs
Lifting costs
Breakeven gas prices
Breakeven reserves
Gas price sensitivity curves
The determination of ultimate reserves, initial production rates, and decline rates on a per well basis was undertaken using AJM's proprietary RAPID (Reserves and Production Information Database) software.
