Implementation of CO2 Foam EOR Technology -Taking Chemistry Innovation from the Lab to Oil Fields

摘要

CO2 foam EOR technology is being evaluated in mature oil fields for improving CO2 flood volumetric sweep efficiency. Since the residual oil saturation to supercritical CO2 flood is quite low (typically 5%-10% under ideal sweep conditions), an improvement in volumetric sweep can lead to substantial improvements in oil recovery The success of a CO2 foam EOR project depends heavily on the choice of the chemical formulation and the injection strategy implemented in the field In this paper we present our framework for design and implementation of CO2 foam EOR technology in oil fields - including chemical formulation development, laboratory core flood experiments to characterize foam performance and engineering of the chemical injection process in the field, which has demonstrated efficient field implementation while optimizing the use of lab and computational resources and reservoir samples. Key factors for consideration in developing a chemical formulation for CO2 foam EOR process are low adsorption on reservoir rock, sufficient CO2-water foam stability, and efficient transport in CO2 and brine at reservoir conditions. In addition the chemical formulation should have no adverse effects on field operations, the environment, health or safety. A wide gamut of potential chemical formulations are evaluated using a set of well-defined high-throughput screening experiments. Experimental results are then statistically analyzed and ranked via pre-defined figure of merit. To conserve scarce reservoir core plugs, core-flooding experiments are initially conducted on model cores to select the optimal formulation. Data is then collected from additional core-flooding experiments using core plugs from the target reservoir to characterize foaming behavior of the chemical formulation as a function of shear rate, formulation concentration, foam quality and oil saturation following a detailed experimental design. This laboratory data is then used to develop an empirical foam model for use in a reservoir simulator. Reservoir simulation cases are run to develop an optimal strategy for injecting the chemical formulation. The reservoir model is validated with field data and is further used to guide the implementation of the CO2 foam EOR process. This design and implementation framework is illustrated with relevant examples.