Optimizing Laboratory cEOR Flooding Evaluations to Assess Initial Oil Saturation and Mobility Ratio

Abstract

We evaluate the polymer, surfactant and alkaline flooding performance in porous media by using an in-house innovative experimental setup. This, to reach an optimum experimental evaluation in an attempt to avoid repeated experimental failures reported in the literature. The workflow presented help us to understand the recorded data with high reliability and accuracy. Moreover, allow working at high temperatures and high salinities in order to mimic reservoir conditions. The evaluation undertaken in this paper comprises four main steps: 1) Fluids preparation and optimization, beginning with an extensive rheological evaluation to define the optimum concentration/composition of the fluids. 2) Calibration of pressure sensors and pumps, and detailed determination of the system's dead volume. 3) Routine core analysis was performed, which included measuring porosity, permeability and pore volume. 4) Spontaneous imbibition experiments, secondary and tertiary mode cEOR flooding experiments. The core flooding experiments were performed at a constant flow rate of 0.15ml/min (equivalent to the field conditions of 1ft/day), then followed by a bump rate after Sor is reached. The constructed setup proved to be beneficial on reducing the experimental failures by showing data reproducibility and precision. Small diameter tubings of 1/16″ minimized the dead volumes and core face differential pressure measurement allowed high accuracy at any injection rate. At elevated temperatures (50°C) polymer flooding in secondary mode showed 2% higher recovery compared to tertiary mode. Similar difference was observed at the ambient temperature. For the conditions evaluated in this work, HPAM polymer showed higher recoveries than those of Bio-polymer at higher temperatures. However, lower recoveries from HPAM were observed at lower temperatures. In terms of surfactant flooding experiments the observed performance is significantly better in secondary compared to tertiary mode, as well as facing significant production of emulsion from suboptimal surfactant solutions. Thoroughly examining these differences in recoveries, two key factors were considered to be of critical interest: initial oil saturation and mobility ratio. Moreover, CT scan imaging allowed assessing capillary end effects during oil saturation. A detailed comparison between dry and saturated core images was performed to insure no capillary end effects existed. Finally, a developed mathematical simulation model permitted to quality check the work and create a benchmark for further evaluations. The workflow presented in this paper helps to close the gaps often discussed in the literature with regards to flooding experimental failures at core plug scale. Thus, it can help fellow researchers to optimize their workflow and enhance the final results to aid in fluid evaluation and assessing the optimum cEOR process.

A Critical Review of Alkaline Flooding: Mechanism, Hybrid Flooding Methods, Laboratory Work, Pilot Projects, and Field Applications

“…Conversely, bond numbers are used in such systems where viscous or gravity forces are dominant. When the capillary number of different EOR flooding methods are compared with water flooding, they are found to be greater in the CEOR method than in the water flooding method [19,20]. When the capillary number can be increased, for example, from 10 −6 (conventional waterflood) to 10 −4 (CEOR) or more, the residual oil saturation decreases.…”

On the Role of Polymer Viscoelasticity in Enhanced Oil Recovery: Extensive Laboratory Data and Review

“…Another major difference that can be seen in this setup is the pressurizing cylinder which is necessary in core flooding applications. An elastomer sleeve is put around the core plug, put in the Hassler cell and pressurized manually by adjusting the cylinder outside the cell [ 93 , 94 , 95 ]. By applying pressure around the sleeve, it is ensured that no injected fluid bypasses the core and, hence, distort, the measurement.…”