Impact of Brine Extraction and Well Placement Optimization on Geologic Carbon Storage Capacity Estimation

Abstract:

Capacity of carbon dioxide storage aquifers depends on a variety of factors including geologic properties and operational designs. The injection well numbers, well spacing and location, open versus closed boundary conditions, and injection with or without extraction of brine are of the parameters that impact the capacity of a storage site. Brine extraction from storage formations has been introduced as an effective strategy for enhancing the storage capacity and mitigating the risk of rapid pressure buildup. It is proposed that extracted brine can be disposed within an overlying formation or will be desalinated at surface facilities. Optimal well placement and rate of CO₂ injection/brine extraction control achieving a predefined pressure constraint at the end of a specific period of storage operation. Reservoir simulation study is required to solve the two-phase flow of gas/brine and pressure buildup in the aquifer. Numerical simulation of geological storage using multiple injectors and extractors is costly and time consuming. Instead, analytical simulation can provide the results with a very good accuracy in a fraction of time compared to the numerical simulation. In this study, an analytical solution was implemented for pressure buildup calculation. The analytical model includes the effects of two-phase relative permeability, CO₂ dissolution into reservoir brine and formation of a dry-out zone around the wellbore. Through the optimization algorithm coupled with analytical model, the optimal rates and locations of CO₂ injectors and brine extractors were estimated, while simultaneously satisfying the pressure constraint to avoid fracture pressure in all injectors. The optimized results of analytical model was verified with a numerical simulator for several reservoir conditions, well configurations and operating constraints. The comparison of the results shows that the analytical model is a reliable tool for preliminary capacity estimation of saline aquifers and brine extraction can significantly increase the storage capacity.