关键词: 二氧化碳, 注入率, 数值模拟, 咸水含水层

Abstract: CO2 storage in deep saline aquifers is considered to be an imperative practical mean for reducing greenhouse gas emissions. Injectivity is one of key factors for determining the feasibility for storage of CO2 in a brine field. Research into the injection rate variation rules and the measures to improve is of great value. Many saline aquifers have relatively low permeability which limits the injection rate of CO2 to the aquifers. In this paper, numerical simulation studies of carbon dioxide storage in brine-saturated reservoirs have been conducted to investigate the approaches for enhancing injectivity through changing the fluid salinity in aquifer, using horizontal well or longer injection screen, and introducing hydraulic fracturing for storage aquifer improvement. Changing fluid salinity can be implemented through injecting a slug of fresh water prior to commencement of CO2 injection. Setup of the models is loosely based on the hydrogeological conditions in Ordos basin. Modeling results indicate that these approaches can effectively improve the injectivity. Use of horizontal well and hydraulic fracturing shows obvious injectivity enhancement. The effect of changing salinity could be more significant when the initial salinity of aquifer is high. The findings may provide helpful hints to the CO2 geologic sequestration in saline aquifer in Ordos basin or similar areas.

Key words: CO2, injectivity, numerical simulation, saline aquifer