Introducing a novel enhanced oil recovery technology

In this paper we present a novel Chemical EOR technique in which dimethyl ether (DME), a widely-used industrial compound is utilised as a miscible solvent in conjunction with conventional waterflooding. The end effect of the solvent's application is an increase in oil recovery significantly greater than that typically achieved by waterflood alone.

The method of application is straightforward, taking advantage of DME's solubility in both water and hydrocarbons: water is used as a carrier for DME during injection and upon contact with reservoir fluids, DME preferentially partitions into the hydrocarbon phase thereby swelling and mobilising the oil phase. This is followed by a DME-free water chase to recover the remaining mobile oil and DME. Residual oil saturation after sweep is reduced, significantly below that typically achieved by waterflood alone. Furthermore, the DME can be extracted from the produced wellstream fluids by distillation and/or absorption processes, and re-used for injection.

The DME Enhanced Waterflooding (DEW) technique takes advantage of the unique solubility properties of dimethyl ether to improve oil mobility and reduce residual oil saturations. Significant research into the pressure-volume-temperature (PVT) behaviour of DME and DME/crude oil mixtures has been carried out in recent years; in particular the partitioning behaviour of the solvent and mixing rules for the various mass transfer properties affecting mobility. The PVT-driven behaviour and the overall displacement efficiency of the DEW technique have been observed in core flood experiments using both carbonate and clastic core plugs.

The DEW technique can be deployed in reservoirs with different geologies, fluid properties and conditions (pressure, temperature and salinity), making its application envelope much larger than that of any of the currently available EOR technologies.