Development of empirical correlation for DME-partitioning between brine and crudes for enhanced waterflooding applications

Abstract

Dimethyl ether (DME) is considered to be a potential EOR agent for enhanced waterflooding. Due to first contact miscibility in hydrocarbons and partial solubility in water/brine, it partitions preferentially into the hydrocarbon phase upon contact when DME-brine solution is injected into the reservoir. As a result, the residual oil swells and its viscosity is reduced. The amount of swelling and viscosity-reduction depend on the extent of DME partitioning and its availability. Therefore, the estimation of the DME-partitioning coefficient (KDME) is crucial to evaluate and understand the performance of DME-enhanced waterflooding (DEW) at reservoir or lab/pilot-scale. In general, this coefficient is a function of several factors including the compositional characteristics of the oil, reservoir pressure-temperature conditions and the salinity of the formation brine. In this study, we perform extensive analysis on the sensitivity of KDME with respect to these factors using Peng-Robinson (PR78) EOS with Huron-Vidal (HV) mixing rules that we calibrated with experimental data. We also discuss the predictive capability of EOS models used in literature to characterize phase behavior of DME-brine-oil mixture. Finally, using all the information available, we develop an empirical correlation to estimate KDME in brine and hydrocarbons that can be utilized for future screening studies in which none or very limited PVT measurements with DME are available.