Abstract
About 4 ×109 bbl heavy oil resource exists in thin (20-40 ft) domestic reservoirs. For this type of reservoir, steamflooding with conventional vertical wells is not economic, and in situ combustion methods are not applied due to operational difficulties. Horizontal well technology offers a potential for improving technical and economic performance of steamflood operations. A reservoir simulation study was conducted to (1) evaluate the viability of applying steamflood operations using horizontal wells in the Charivari Creek, Arkansas, waterflooded heavy oil reservoir and (2) analyze in detail the effects of different pattern configurations, including vertical injectors-vertical producers, horizontal injectors-horizontal producers, horizontal injectors-vertical producers and vertical injectors-horizontal producers, on steamflood performance.
Low permeability was found to have the most negative influence on steamflood performance for vertical injectors and producers. The injected steam raised the pressure and temperature of the reservoir to higher values than those observed in the high-permeability reservoirs, resulting in ineffective displacement and reservoir heating. Among the different configurations tested, the horizontal injectors-horizontal producers with 1,272-ft laterals increased the cumulative oil-steam ratio to 0.2 and decreased the production cost to $12.70/STB. Comparable results obtained for vertical wells are cumulative oil-steam ratio of 0.1 and production costs of $23.50/STB. Inclined wells showed poorer performances than horizontal wells because of nonuniform displacement. Configurations using horizontal injectors-vertical producers were not as effective as vertical injectors-horizontal producers because of fluid flow difficulties created with the high injecti vity of horizontal injectors and the low productivity of vertical producers.
