Abstract
This article describes the main features of an unconventional approach to model a polymer flood in the Kalamkas oilfield. This non-standard simulation method is based on specially performed inter-well tracer tests, step-rate tests, pressure fall-off tests, dedicated field studies, well monitoring, and lab analysis. Our approach excludes permeability reduction as a mechanism to provide more mobility reduction than expected from rheology measurements (resistance factor) and by improving the recovery during post-polymer water flooding (residual resistance factor). Evidence is presented to support this exclusion for real field applications. Additionally, our approach places a significant emphasis on history matching bottomhole pressures. Our effort accounts well for the decreased mobility of the injected polymer solution and increased rock permeability during a polymer flood. In contrast to most other simulation approaches to polymer flooding, our method incorporates open fractures during polymer injection and their impact on injectivity and sweep efficiency. A literature review (lab tests and field cases) and our laboratory and field studies confirm the validity of our approach and its advantages over other modern simulator modeling of polymer flooding. From viscosity measurements of back-produced polymer solutions from injectors and well tests (inter-well tracer tests, pressure fall-off tests, step rate tests), we proved that polymer flooding induces fractures or fracture-like features and consequently, the polymer solution flows through the fracture with increased injectivity proportional to a resistance factor. Also, incorporated are expectations during a brine post-flush and the absence of the residual resistance factor (i.e., equal to 1). Implementation of these concepts brings our model closer to reality for simulating polymer floods.
