Scleroglucan Polymer Injectivity Test Results in the Adena Oilfield

Abstract

Reservoirs with harsh environments are now being routinely evaluated for applications of chemical EOR. High temperatures and high salinity water are proving to be hurdles chemical manufacturers must overcome. Scleroglucan is a biopolymer with robust viscosifying power, excellent stability under high temperature, high salinity, and resistance to shear. An injectivity test was conducted in the high temperature (180 °F) Adena oilfield to evaluate the injectivity of scleroglucan polymer. Field injectivity test results are compared to those from the laboratory. Polymer parameters evaluated include polymer viscosity, polymer shear, resistance factor, and residual resistance factor. The unique feature of this injectivity test is the bottom-hole pressure data that allowed for direct field measurement of resistance factor and the evaluation of multiple fall off tests. Pressure transient analysis (PTA) allowed for (1) skin to be measured before and after polymer injection to evaluate sand face plugging, and (2) permeability measurements that were used for direct field measurement of residual resistance factor. Conclusions from the injectivity test in the Adena field are: Scleroglucan was successfully injected into a harsh reservoir environment. PTA data provided a field based direct measurement of resistance factor (RF) and residual resistance factor (RRF).PTA fall off test indicated no sand face plugging, in that a constant skin was observed at the well before and after the polymer injectivity test.RRF was measured at the sand face via FBHP and several feet into the reservoir via PTA. Sandface RRF was 1.3, indicating a 25% reduction in permeability, while PTA based permeability (larger radius of investigation) was reduced by 50%, the equivalent of a RRF of 2.Skin for the two fall off tests, before and after polymer injection, show the polymer did not plug nor exacerbate the pre-existing formation damage. The first field injection of EOR–grade scleroglucan was successful. The use of BHP data and fall off testing allowed for field-based values of resistance factor and residual resistance factor to be measured. Typically, these parameters are laboratory derived values and uncertainty exists when scaling up the process. The use of pressure transient analysis in polymer injectivity tests offers an economical option for field evaluation of polymer based EOR technologies.