Introducing a Novel Enhanced Oil Recovery Technology

Abstract

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.

Dimethyl Ether Enhanced Oil Recovery in Fractured Reservoirs and Aspects of Phase Behavior

“…The DME EOR technique has shown a very efficient performance in increasing the oil recovery from carbonate and sandstone rocks in laboratory tests. ,,, The oil recovery mechanisms in this technique are believed to be phase-behavior driven, and thus, the significant oil recovery observed in the laboratory is independent of the rock type or properties. ,, Coreflood data have also shown that DME EOR is efficient in both secondary and tertiary mode. , While DME is a relatively expensive compound, the DME EOR procedure can be economically feasible in some circumstances. , It should be noted that the DME slug size is an important parameter in feasibility studies, which should be determined for each specific field. , Moreover, since DME does not form a new phase in the reservoir and is present in the oleic and aqueous phase, the injected solvent can be recycled from the produced fluids and reused. , DME preferentially partitions into the oleic phase, and therefore, most of the injected DME is recovered with the produced oil. The remaining DME in the reservoir can also be efficiently recovered with a chase waterflood. , The reported coreflooding experiments on chalk declare no adverse effect of the EOR agent on the rock integrity, which is a determining factor when improvements of oil recovery in chalk formations are discussed.…”

“…A recently proposed solvent for the mutually soluble solvent-based EOR technique is dimethyl ether (DME). DME, the simplest ether, is a colorless gas at atmospheric conditions, which liquifies at moderate pressures and ambient temperature. − It is a nontoxic compound, environmentally benign, , and partially soluble in water, which then exhibits first-contact miscibility with the oleic phase. The combination of these favorable properties has recently attracted the attention of the oil industry.…”

“…Pure DME is well-characterized in the literature. − However, to fully investigate the potential of the DME EOR technique, the phase behavior of the DME–brine–oil system in realistic reservoir conditions must be investigated. In the light of DME utilization in oil recovery processes, both the solubility of DME in a synthetic brine and the impact of DME on the density and viscosity of a crude oil have been measured. , The DME partition coefficient was also measured for a couple of specific brine–oil systems, and the data were used to calibrate and tune the equations of states. ,,− The published data have been utilized in the development of the phase behavior model and in the history matching of the laboratory coreflood experiments. , The experimental results and the developed phase behavior models have been used to model the DME EOR process at the field scale ,,,, and to perform economic studies. …”

“…First, there is no swelling factor reported for the DME–brine–oil system. Since oil swelling is one of the major oil recovery mechanisms for DME EOR, ,, obtaining swelling data is essential in predicting and comparing the performance of DME EOR to other available solvents. Second, there is no investigation into the suitability of the DME EOR technique for fractured reservoirs.…”

Compositional modeling and simulation of dimethyl ether (DME)-enhanced waterflood to investigate oil mobility improvement

“…In recent years, DME has been considered as a solvent for EOR. In particular, Shell has studied and developed this process (Chernetsky et al 2015;Groot et al 2016;Parsons et al 2016). DME is often compared to LPG due to their similar physical properties; however, the solubility of DME in water is almost 1000-fold greater than that of propane (Parsons et al 2016).…”