Dimethyl Ether Enhanced Waterflood (DEW) is a novel and promising solvent-based EOR technology developed by Shell. Dimethyl Ether (DME) is a widely-used industrial chemical which is applied as a water soluble solvent for EOR applications to enhance a conventional waterflood. Once the DME-brine solution is injected into the reservoir and comes in contact with the oil, the DME molecules partition into the oil phase which leads to oil swelling and mobilization of residual oil. Moreover the partitioning of the DME into the oil phase decreases the oil viscosity and improves its mobility. The combination of these effects results in both a significantly higher ultimate oil recovery compared to the conventional waterflood as well as accelerated oil production at lower energy footprint compared to thermal technologies. As the solvent is water soluble, it can be very effectively back-recovered from the reservoir by re-dissolving the trapped DME in the DME-free chase water slug. The solvent is recovered from the produced oil and water streams at surface and re-used. The main objectives of this paper are to present the first experimental results, explain the physical mechanisms of this novel concept and demonstrate the extra oil recovery. Additionally, modeling workflows used to interpret the experiments and predict the benefits of field EOR application are illustrated.To gain an insight into physical mechanisms behind the DEW, develop modeling workflows and de-risk the technology, an extensive experimental program was set up to investigate both the fluid-fluid and rock-fluid interactions. Phase behavior of DME/brine and DME/crude mixtures has been carried out, with a focus on the partitioning of the solvent between brine and crude. Mixing rules for properties affecting the phase mobilities have been determined. In parallel, a number of coreflood experiments were conducted on both carbonate and clastic cores of varying permeability to investigate the dynamic DME/crude behavior and DME/rock interaction. PVT experiments were used to build phase equilibrium models. Based on these PVT models, the coreflood experimental data was matched and interpreted using numerical simulation.Coreflood experiments confirmed the phase behavior-driven character of the DEW technology. A good match between the experimental and simulated oil recovery was obtained in most cases. This shows that PVT models, generated using measured basic data, are in a good agreement with the dynamic coreflood experiments.
Di-methyl-ether (DME) is a solvent with clear potential for EOR through its novel use in DME enhanced water flooding (DEW). Fundamentally, this phase behaviour driven EOR process is based on an immiscible displacement of the oil phase by the water phase, enhanced by DME mass transfer between the two phases. Modelling such a process is far from trivial and requires a tailored modelling approach.In previous work (Chernetsky, et al., 2015) a dynamic model for DEW was successfully employed to history match core-flood experiments. This paper builds on this work by analyzing the driving mechanisms and sensitivities at different stages of the DEW process and describing the process of efficient upscaling of the model to field scale.The first part of this paper presents the basic modelling workflow for DEW for light to medium oils and typical concentration and saturation profiles and ternary diagrams. The objective is to determine the main driving mechanisms and their impact on the incremental oil recovery and DME utilization. The second part of the paper focusses on the upscaling of the DEW model to field scale. In particular, sensitivities to reservoir heterogeneity, relative permeability data and grid size are discussed through examples of sector and field models.The one-dimensional sensitivity studies provide valuable insight into the efficiency and dependencies of the fundamental recovery mechanism. The sensitivities focus on incremental oil recovery and DME efficiency and cover design parameters relevant to the DEW process, such as DME slug size and brine salinity, oil properties, remaining oil saturation and parameters used in simulation studies, such as grid size.Results for field scale modelling give guidance on how the DEW models can be effectively upscaled and what sensitivities can be expected at reservoir scale, and show the value of the model in supporting decision making and implementation of DEW in the field. Recommendations for field scale modelling are given, based on sensitivity analyses for various DEW scenarios. Computational techniques, such as adaptive gridding and parallel computing, are proposed to overcome limitations due to grid size sensitivity.
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.
This paper extends the subject of the ASP fullfield (re-) development and optimization discussed in the paper SPE-174680-MS to an ASP pilot in the same field using more detailed ASP simulation studies with a finer geological model. The study was targeted to investigate the roles of various static (e.g., geology), dynamic (e.g., fluid properties), ASP process (e.g., chemical adsorption) and numerical (e.g., grid size) parameters on the ASP performance prediction. The paper focusses on three key subjects: firstly, understanding the ASP pilot performance under different realizations. Thereafter, we identify the key aspects of an ASP flood and break the problem statement into elements that are further investigated with the help of customized scenarios. We will share the results with regards to key sub-surface design elements for an ASP pilot, particularly highlighting what works and what does not, and how to improve the pilot response for a field with high degree of vertical heterogeneity.
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