Abstract

In this paper, gas pressure cycling (GPC) and solvent-assisted gas pressure cycling (SA-GPC) were developed as two new and effective enhanced oil recovery (EOR) processes. Eight coreflood tests were conducted by using a 2-D rectangular sandpacked physical model with a one or two-well configuration. More specifically, two cyclic solvent injection (CSI), three GPC, and three SA-GPC tests were conducted after the primary production, whose pressure was declined in steps from Pi = 3.0 MPa to Pf = 0.2 MPa. It was found that the CSI tests had poor performances because of the known CSI technical shortcomings and an additional technical issue of solvent trapping found in this study. Quick heavy oil viscosity regainment resulted in the solvent-trapping zone. In contrast, C3H8-GPC test at a pressure depletion step size of ∆PEOR = 0.5 MPa and C3H8-SA-CO2-GPC test at ∆PEOR = 1.0 MPa had the highest total heavy oil recovery factors (RFs) of 41.9% and 36.6% of the original oil-in-place (OOIP) among the two respective series of GPC and SA-GPC tests. The better performances of these two tests than C3H8- or CO2-CSI test were attributed to the effective displacement of the foamy oil toward the producer in the two-well configuration. Thus the back-and-forth movements of the foamy oil in CSI test in the one-well configuration were eliminated in these GPC and SA-GPC tests. Furthermore, C3H8-GPC test outperformed C3H8-SA-CO2-GPC test in terms of the heavy oil RF and cumulative gas-oil ratio (cGOR) because of the formation of stronger foamy-oil flow and the absence of CO2, which reduced the solubility of C3H8 in the heavy oil in the latter test. In summary, different solvent-based EOR processes were ranked based on the heavy oil RFs as follows: C3H8-GPC > C3H8-SA-CO2-GPC > CO2-GPC > C3H8-CSI > CO2-CSI.

Highlights

  • The world’s heavy oil and oil sand resources are estimated to be approximately 5.6 trillion barrels [1,2]

  • The experimental results show that C3 H8 -cyclic solvent injection (CSI) outperformed

  • A total of eight sandpacked coreflood tests were performed in the laboratory by using a 2-D physical model to study the production performances of two new different solvent-based enhanced oil recovery (EOR) processes and their abilities to restore foamy oil and enhance the heavy oil recovery

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Summary

Introduction

The world’s heavy oil and oil sand resources are estimated to be approximately 5.6 trillion barrels [1,2]. Western Canada accounts for more than 70% of the world’s in-place oil sands [2,3]. It has been reported that the western Canadian sedimentary basin has a total proven oil sand reserves of about 162.3 billion barrels with majority of the accumulations located in Alberta [4]. 17.7 billion barrels of the heavy oil reserves are in Saskatchewan [3]. The western Canadian heavy oil/oil sand resources and associated gas are accumulated in the shallow Lower Cretaceous fluvio-deltaic unconsolidated sands at depths of less than 3000 ft. Other additional reserves are accumulated in the Devonian and Energies 2020, 13, 5047; doi:10.3390/en13195047 www.mdpi.com/journal/energies

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