Implementing Steam Assisted Gravity Drainage Through Combination of Vertical and Horizontal Wells in a Super-heavy Crude Reservoir with Top-Water

Abstract Guantao formation in Du84 block, Liaohe oilfield is a typical massive block extra-heavy oil pool with top-water. The oil viscosity is very high and the formation thickness is great. Bitumen shell with 3~4m thickness exist between the top-water layer and oil column. If the bitumen is dissolved when heating in the steam injection recovery process, the top-water will flow down. Moreover, the field production showed that conventional steam stimulation recovery with vertical well is poor. New methods and technologies have to be researched and tested to improve the oil recovery, decrease operation cost and enhances economic efficiency. Numerical simulation results showed that the reservoir can be developed efficiently by implementing Steam Assisted Gravity Drainage (SAGD) process using existing vertical well and horizontal wells to be drilled following steam stimulation. To avoiding top water going down, the new well completion methods have to apply, and the upper portion of the formation in the steam injector shouldn't be perforated. If the viscosity of the bitumen shell is greater than 500×104mPa.s, the 20m thickness of upper portion shouldn't be perforated to inhibit the top-water effectively. If the viscosity of the bitumen shell is 50~200×l04mPa.s, the thickness of upper portion not perforated should be more than 30m to inhibit the top-water effectively. At the same time, the results also showed that the heat communication between the wells is an important factor to control the top-water. The SAGD process can be implemented only when heat communication is established by steam stimulation in order to inhibit the top-water.