Experimental Investigation of Brine Hardness and Its Induced Chemistry during Heavy Crude Recovery through CO2 Injection

摘要

In a typical oil reservoir, untapped crude co-exists with water (connate water or brine) whose chemical composition depends on the formation in which it trapped. Although CO2-EOR has been lately regarded as viable recovery technique for heavy crudes, its applicability on the field scale lies in understandings of various phenomena among which induced chemistry. In this research, we proposed to evaluate the extent to which brine salinity and hardness as well as an induced chemistry inherent to CO2 injection alter heavy oil recovery. Conducted at a laboratory scale, CO2was selected as a displacing agent to be injected in an analysis cell of a PVT apparatus within which reservoir physical conditions were reproduced. A heavy crude (API 11.5o) and three brine solutions chemically different were selected as displaced fluids. CO2 showed a high solubility, which increased with the pressure, comparatively to methane in both pure component hexadecane and heavy crude with a bubble point –pressure at 7.8 MPa. Salinity, taken alone, was found not to alter gas solubility, however the build-up in Ca2+ and Mg2+ within connate water impacted invariably GOR.