Abstract

One of the ways to improve the efficiency of steam injection is to use chemicals as an additive to alter interfacial properties. Historically, this has been tested using surfactants, which are expensive and thermally unstable. Therefore, commercial applications have been highly limited in that area over the past three decades. In conjunction with recent efforts using new generation materials as EOR agents, we performed a screening study to identify the potential chemicals/materials for heavy-oil recovery and to investigate the applicability of selected new generation chemicals as interfacial properties modifiers at steam temperature.

Different experimental methods, including capillary imbibition tests, i.e. contact angle and interfacial tension measurements, were combined to understand the mechanism of alteration surface interplay (wettability and interfacial tension) using different chemical agents. Capillary imbibition tests were conducted to study the potential of these chemicals to alter wettability and rock/chemical interactions on limestone and aged sandstone cores at high temperature. Pendant drop interfacial tension (IFT) and contact angle measurements were performed using a high pressure and high temperature cell under the same -steam- conditions.

Seven different chemical agents including a high pH solution (sodium metaborate), an ionic liquid, a cationic and an anionic surfactant, and nanofluids (aluminum and zirconium oxides) were tested in this study. Indiana limestone samples were saturated and aged in heavy oil with a viscosity of 6,000 cp. Capillary imbibition tests were conducted under high temperature (between 90°C and 180°C) and high pressure (185 psi) conditions using a newly-manufactured visual cell. The production rate and ultimate recovery were used to evaluate the capability of different chemicals changing the interfacial properties and their thermal stability at steam temperature. Contact angles between heavy oil and calcite plates were measured under the same conditions. Finally, the stability of the chemicals was measured through settlement tests at steam temperature conditions as well as TGA (thermal gravimetric analysis). The combination of all these results helped identify the applicability of the selected chemicals under steam conditions for carbonates. Technical and economic limitations for each chemical as well as the way the chemical contributes to recovery (wettability alteration or IFT reduction) were identified.

Investigation of interfacial properties alteration induced by new generation chemicals at high temperature is helpful in the selection and application of efficient and economical chemicals in steam based heavy-oil recovery methods.

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