Research on Characterization Technology and Field Test of Biological Nano-oil Displacement in Offshore Medium- and Low-Permeability Reservoirs

Abstract

At present, the water displacement recovery in some medium-and low-permeability reservoirs that cannot be injected and produced in offshore oil fields because of small pores and complex structures is less than 18%. This amount is far lower than 25− 40%, which is obtained after water displacement and chemical displacement in medium-and high-permeability reservoirs. Given the current situation of water injection in offshore medium-and low-permeability reservoirs, a new green and environmentally friendly nano-oil displacement technology must be urgently developed to improve the sweep coefficient and oil displacement efficiency of injected water. In this study, the experimental laboratory investigation of a biological nano-oil displacement system suitable for medium-and low-permeability reservoirs is performed. The oil displacement effects, such as changing interfacial tension, viscosity reduction, and oil flushing ability, are also evaluated. The partial differential mathematical model of multicomponent isothermal multiphase seepage is deduced, the mechanism of biological nano-oil displacement technology is finely characterized, and a set of numerical simulation optimization charts of the biological nano-oil displacement process parameters is established. Results show that the biological nano-oil displacement system has adsorption characteristics in porous media, effective miscibility with crude oil, and a minimum contact angle reaching 14.3°. Its interfacial tension can be reduced to the 10 −3 level, the viscosity reduction efficiency can reach more than 90%, and the oil washing efficiency can reach more than 70%. Compared with the conventional water and chemical displacement systems, the displacement system in this study has a good oil rock flushing effect and improves oil recovery by 15%. When the injection−production ratio is comprehensively considered, the recommended injection cycle is 6000 ppm. The field test of the biological nano-oil displacement system has been completed, with a validity period of 1 year and a cumulative oil increase of 1.2 × 10 4 m 3 , which is still effective. This study provides environmentally friendly solutions for the new chemical displacement of offshore medium-and low-permeability reservoirs. The established process parameter optimization chart has important guiding relevance for the optimization of technical schemes and improvement of the oil increase effect in chemical displacement.

Sodium fatty alcohol polyoxyethylene ether carboxylate/cationic surfactant binary system for high‐salt oil reservoir

“…The oil washing efficiency of both AECM–CTAB (5:5) and AECM–CPyCl (5:5) reached over 70%, while the highest washing efficiency was 74.68% for AECM–CTAB (5:5); the lowest oil washing efficiency was only 52.16%. However, the early water‐injection recovery of the conventional reservoir was 29.14%, and the recovery of polymer flooding was 44.21%, while for some low‐ and medium‐permeability reservoirs, the water flooding recovery was even less than 18% (Feng et al, 2022). In this paper, these binary composite systems improved the recovery by at least 45.54% and 30.47% based on the water flooding and polymer flooding, respectively (Gu et al, 2017).…”

Laboratory Experiment and Application Evaluation of a Bio-Nano-depressurization and Injection-Increasing Composite System in Medium–Low Permeability Offshore Reservoirs

“…After being injected into the water injection well, it drives away the pore hydration film around the bottom of the well to increase the pore seepage area and form a hydrophobic film of nano-thickness, resulting in water phase slip to reduce the seepage resistance, − thereby reducing the injection pressure of the water injection well. It has achieved very good results in the field pilot experiment in Bohai Oilfield. − …”

Synthesis and Enhanced Oil Recovery Potential of the Bio-Nano-Oil Displacement System

“…NPs can easily pass through the porous medium without reducing the formation permeability. Therefore, bio-nanoparticles can play a wide-ranging role and improve the macroscopic sweep efficiency and enhance the recovery rate . In this paper, transmission electron microscopy (TEM), particle size analysis, and ζ-potential analysis were used to characterize the stable dispersion of the bio-nano-oil displacement agent system at different nano concentrations.…”

“…Therefore, bio-nanoparticles can play a wide-ranging role and improve the macroscopic sweep efficiency and enhance the recovery rate. 29 In this paper, transmission electron microscopy (TEM), particle size analysis, and ζ-potential analysis were used to characterize the stable dispersion of the bio-nano-oil displacement agent system at different nano concentrations. The oil–water interface performance of the bio-nano-oil displacement system was evaluated by interfacial tension measurement and contact angle measurement.…”