Geologic storage of carbon dioxide and enhanced oil recovery. Ⅰ. Uncertainty quantification employing a streamline based proxy for reservoir flow simulation

摘要

Carbon dioxide (CO_2) is already injected into a limited class of reservoirs for oil recovery purposes; however, the engineering design question for simultaneous oil recovery and storage of anthropogenic CO_2 is significantly different from that of oil recovery alone. Currently, the volumes of CO_2 injected solely for oil recovery are minimized due to the purchase cost of CO_2. If and when CO_2 emissions to the atmosphere are managed, it will be necessary to maximize simultaneously both economic oil recovery and the volumes of CO_2 emplaced in oil reservoirs. This process is coined "cooptimization". This paper proposes a work flow for cooptimization of oil recovery and geologic CO_2 storage. An important component of the work flow is the assessment of uncertainty in predictions of performance. Typical methods for quantifying uncertainty employ exhaustive flow simulation of multiple stochastic realizations of the geologic architecture of a reservoir. Such approaches are computationally intensive and thereby time consuming. An analytic streamline based proxy for full reservoir simulation is proposed and tested. Streamline trajectories represent the three-dimensional velocity field during multiphase flow in porous media and so are useful for quantifying the similarity and differences among various reservoir models. The proxy allows rational selection of a representative subset of equi-probable reservoir models that encompass uncertainty with respect to true reservoir geology. The streamline approach is demonstrated to be thorough and rapid.