Abstract

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 16 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.

During the period January 1999 to December 2004, 44,224 gas wells (that can be declined) have been put on production. These wells have found in excess of 17.2 TCF of gas reserves with an average reserve per well of 0.39 BCF. The geographic area where the most gas wells were drilled and put on production was in Southern Alberta with 20,344 wells. Southern Alberta also showed the lowest average reserves per well, of wells that can be currently declined, of 0.11 BCF while the BC Foothills showed the highest reserves per well of 7.8 BCF.

Introduction

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 series of larger regional studies performed by the consulting firm AJM Petroleum Consultants (AJM) from 2001 to the present. The regional studies utilized various parameters for the gas plays resulting from an unbiased statistical analysis of all wells drilled during the most recent five-year period within the WCSB. Results were reported for both risked (Exploration and Development) and unrisked (Development) cases.

The area investigated in the regional studies includes all productive natural gas formations in Western Saskatchewan, Alberta, and Northeastern British Columbia. The basin was subdivided into 16 geographic areas (Figure 1).

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