Optimization of SAGD in conductive fractured reservoir

Abstract

Steam Assisted Gravity Drainage is a successful process that has been applied to extract heavy oil and bitumen mostly in Canada. Conductive fractures as reservoir heterogeneity are spaced a few meters from each other and differ from network fractures. There are a few studies investigating the impact of such fractures on SAGD performance. This work is a numerical study examining the relative location and configuration of wells to conductive fractures as an attempt to optimize SAGD process in three types of conductive fractures including horizontal, vertical and oriented fractures. While vertical fractures located above the well pair enhance the oil recovery rate at early time, those located far from the well pair do not affect the process performance. Consequently, to optimize the process, the wells should be applied beneath the vertical fracture. For the vertical conductive fractures locating at bottom of the reservoir, higher well spacing results in more desirable performance if the wells are drilled at the place of the fracture. Sensitivity analysis of injector-producer well spacing illustrated that for horizontal fractures locating around 5 m from the reservoir base, the injector should be drilled above the fracture to enhance the process performance much more than the case of having the injection well below the fracture. Also it is showed that the well pair should be located in a manner that oriented fractures with positive slope place at right hand side and near the wells. Moreover, Off-setting the wells in the fracture direction resulted in enhanced behavior of the process. In low permeability tar sands, hydraulic fracturing can mimic vertical conductive fractures which improve steam chamber expansion, hence resulting in better performance. This study suggests some screening criteria for the well placement design to enhance the oil recovery in conductive fractured reservoirs.