Developing a Layered Heterogeneous Precambrian Reservoir by Polymer Flooding

Abstract

Enhanced oil recovery through injection of a solution of water and polymer is becoming a mature chemical flooding technique. In general, reservoirs with mature water-flooding projects offer an excellent opportunity for extension with polymer injection as uncertainties associated with reservoir connectivity and injection potential are already substantially reduced. For our particular reservoir an additional fortunate circumstance includes an ongoing polymer injection project in an adjacent reservoir which enables easy field testing given the local operational challenges and circumstances. This paper presents ongoing work related to improving ultimate oil recovery from an active water flood project by polymer injection where a polymer flooding pilot is already ongoing. The work includes studies to extend the existing polymer injection facilities of a nearby polymer project to this rather different, in geologic terms, Precambrian reservoir with much lower permeability, oil saturations and significantly more layered reservoir architecture. Geological and petrophysical workflows together with dynamic modeling history matching iterations resulted in reducing subsurface uncertainties such as the distribution of permeability and initial oil saturation. Reservoir compartment connectivity and sweep efficiency are constrained by matching pressure and injection, as well as, production data from 180 wells. Polymer injection feasibility is proven through: dynamic modeling, laboratory experiments, ongoing polymer injection pilot and adapting learning’s from the ongoing adjacent polymer project. The study reveals that a polymer injection project is economically feasible under a range of subsurface and costs scenarios.