Five-spot Glass Micromodel Research Articles

Experimental Study of Solvent Flooding to Heavy Oil in Fractured Five-Spot Micro-Models: The Role of Fracture Geometrical Characteristics

Abstract The solvent-based process appears to be an increasingly feasible technology for the extraction of heavy oil reserves. However, there is a lack of fundamental understanding of how fracture geometrical characteristics control the oil recovery efficiency in this type of enhanced oil recovery (EOR) technique. In this work, a series of experiments were performed whereby the pure and mixed hydrocarbon solvents (HCS) displaced heavy oil in fractured five-spot glass micro-models. Successive images of the solvent injection process were recorded. The oil recovery factor, as a function of injected pore volume of solvents, was measured using image analysis of the provided pictures. It has been observed that the oil recovery decreased when the fractures' spacing, discontinuity, overlap, and distribution increased. In contrast, the oil recovery increased when the orientation angle, discontinuity-distribution and the number of fractures increased. Also, it has been found that there is an optimum solvent composition, which maximizes the oil recovery. Finally, some pore-level visualization representing the role of asphaltene precipitation during miscible injection was illustrated using these experiments. This study demonstrates the applicability of the micro-models for the fundamental studying of the solvent-based process in fractured five-spot systems, which are used to investigate the effect of fracture geometrical characteristics and their effect on oil recovery. Introduction Heavy oil and bitumen reserves represent a considerable portion of worldwide energy resources. It is estimated that these reservoirs contain six trillion barrels of oil originally in place (OOIP), which is much more than the total conventional oil reservoirs. Great consumption of light oil reserves and their resulting dramatic decline encourages more interest in exploitation of highly viscous oil and bitumen for future energy demands. For optimum conditions, the primary recovery of these reservoirs would not exceed 10% of the OOIP(1). A variety of thermal methods, including cyclic steam stimulation, in-situ combustion and steam assisted gravity drainage are currently being applied for extraction of these crudes. As far as the reservoir's oil is heated, the main fraction of thermal energy is used up in heating the formation itself. For the reservoirs with a thin pay zone, bottom water zone and/or overlying gas zone, excessive depths, low thermal conductivity of rock matrix, high water saturation, etc., the economical applicability of thermal methods is doubtful. With respect to current available recovery technologies, these reservoirs are categorized as problematic reservoirs(2,3).

Pore-Level Investigation of Heavy Oil Recovery During Water Alternating Solvent Injection Process

This study concerns with the microscopic and macroscopic fluid distribution and flow behavior during water alternating solvent (WAS) injection process to heavy oil using micromodel generated from thin section of a real rock which has rarely attended in the available literature. In this study, a one-quarter five-spot glass micromodel was deployed to examine the effect of flow media topology on microscopic displacements as well as macroscopic efficiency of WAS process. The micromodel was initially saturated with the heavy oil, and then the hydrocarbon solvent and water were injected alternately into it. The observations confirmed that WAS injection scheme is an effective method for the recovery of the significant amount of residual oil. Using solvent as the leading batch in WAS scheme can really improve the oil recovery by increasing the amount of microscopic sweep efficiency in flow paths, where the molecular diffusion in solvent–heavy oil system occurs. Presence of connate water in WAS scheme can improve the recovery efficiency especially at higher water saturations. Heterogeneity of the medium caused the water to be distributed better in the medium, but the amount of residual oil in the flow area is going to be increased. Small precipitates of asphaltene particles due to solvent injection and localized entrapment of the oil due to heterogeneity effects, water blockage, and deadend pores were observed mainly in this process. The results of this study reveals the pore scale events in WAS injection process and will be helpful for developing reliable simulation models.

Fundamental Study of Pore Morphology Effect in Low Tension Polymer Flooding or Polymer–Assisted Dilute Surfactant Flooding

Low Tension Polymer Flooding or Polymer Assisted Dilute Surfactant Flooding is generally deployed as a method to produce additional oil trapped in oil reservoirs after waterflooding. Fundamental study of microscopic mechanisms and pore-level phenomena in Polymer Assisted Dilute Surfactant Flooding needs more investigation. Of particular concern and interest is to probe into and document the effect of pore morphology and structure on microscopic phenomena occurring at pore level. No previous works on the effect of pore morphology in Polymer Assisted Dilute Surfactant Flooding has been reported in the literature. In this study, one-quarter five-spot glass micromodels were deployed to examine the effect of porous media morphology and structure on microscopic mechanisms as well as macroscopic behavior of Polymer Assisted Dilute Surfactant Flooding. Four types of pore morphologies were employed to study this factor. Results show that the pore geometric properties in a porous medium will dictate the degree of displacement front instability, capillary imbalance, viscous fingering, wetting characteristics and its distribution, and finally magnitude of ultimate oil recovery. We also found that the formation of flow scheme is dramatically influenced by the pre-designed injection scheme.