Abstract
More than 10 000 horizontal wells have been drilled in the Westem Canadian Sedimentary Basin (WCSB) between 1987 and the present. About 5 000 of these wells have been drilled in conventional oil pools on primary production, and about 1000 wells have been drilled in heavy oil bitumen reservoirs. In addition about 3000 wells have been drilled in enhanced oil recovery (EOR} projects (mainly waterfloods, and miscible/immiscible gas/hydrocarbon injection solvent floods), and about 1000 horizontal wells have been drilled in natural gas reservoirs. As expected in each group the initial production rate and cumulative production (5 years) show some variation from the mean/average rates..
In this review we will focus our attention on the performance of horizontal wells drilled in EOR projects and natural gas pools. We have grouped these wells into conventional heavy oil sandstone waterflood projects; Light-medium oil sandstone waterflood projects; carbonate waterflood projects; carbonate "horizontal miscible" solvent floods projects; carbonate "vertical miscible" solvent floods projects; sandstone gas horizontal wells projects; and carbonate gas horizontal wells project. Horizontal wells drilled in conventional oil pools on primary production and heavy oil/bitumen in-situ projects are not included in this review. We have identified representative samples for each group. The median, mean/average, 75th percentile and 25th percentile have been determined for the initial rates, and 5-year cumulative (5-year cum.) production. Production Performance Rate-Time Plots for each group are shown.
We have also provided a short discussion of the performance of each group. In our discussion we have tried to identify wells/pools and formations which are chiefly responsible for the 75th and 25th percentile performance, and have discussed some of the reservoir rock and fluid characteristics which may be responsible for the variation in performance. Brief comments are also made on some drilling or operational techniques employed which may have affected the performance.