CO_2 STORAGE CAPACITY PREDICTIONS FOR WEYBURN CO_2-EOR PROJECT

摘要

Carbon dioxide (CO_2) is being injected into the Weyburn oilfield in southeastern Saskatchewan, one of the largest medium gravity crude oil fields in Canada, for the purpose of enhanced oil recovery (EOR) by EnCana Corporation, while at the same time this site is being studied for the feasibility of geological storage of CO_2, a greenhouse gas (GHG). This study, which is part of the "IEA Weyburn CO_2 Monitoring and Storage Project", describes the predictions of the CO_2 storage capacity in the entire seventy-five CO_2-EOR patterns in the Weyburn field using reservoir model as a tool. Due to the large-scale of the seventy-five-pattern simulation and the limitations of the computer capability, a coarser simulation approach that captures the overall injection, production and fluid distributions within each single pattern but not the details for each individual well, is used. The justification to use this coarser simulation approach is based on a methodology developed in the IEA project that started with very detailed fine-grid single-pattern simulations and ended with the coarse-grid seventy-five-pattern simulation. The capability of the reservoir model to simulate the CO_2-EOR process is first validated based on three very detailed simulations by matching of pre-CO_2 and up-to-date post-CO_2 field production history in three selected single patterns in the nineteen-pattern Phase 1A area and followed by predictions for the CO_2 distribution and storage performance at the end of the EOR. The fine-grid single-pattern simulations are then upscale to coarse-grid simulations of the same patterns. The goal of the upscaling is to reproduce the important features of the finer description using a coarser description and determine the upscaling pseudo-functions for patterns with different CO_2 injection strategies. The three coarse-grid single-pattern simulations are used as building blocks to carry out simulations of the entire seventy-five patterns as the same grid resolution is applied.