Year: 2025
Type: article
Abstract: This article addresses the critical issue of low ultimate oil recovery in the development of highviscosity and heavy oil fields in Kazakhstan. The application of conventional waterflooding techniques at reservoirs such as Karazhanbas is often inefficient. The study substantiates the necessity of transitioning to chemical enhanced oil recovery (EOR) methods, which have been proven globally to increase the oil recovery factor (ORF). The research objective was a comparative evaluation of the efficiency of combined chemical EOR techniques -specifically, alkaline-surfactant (AS) and alkaline-surfactant-polymer (ASP) flooding - under high-viscosity oil conditions. The investigation was conducted using the Karazhanbas field as a case study. The target crude is characterized by a density of 0.935–0.945 g/cm³ and an insitu viscosity of 460-550 mPa·s at 30°C. Laboratory coreflood experiments were performed on reconstituted sandpack models, simulating reservoir rock, using a standard coreflood apparatus (UIK-S(2) setup). Tested formulations included alkalis (KOH, NaOH, NaHCO3), surfactants (sodium dodecyl sulfate, sodium dodecylbenzenesulfonate), and a polymer (partially hydrolyzed polyacrylamide, HPAM). The experimental results confirmed the potential for a substantial increase in the oil displacement efficiency through chemical injection. Following conventional waterflooding, which achieved a displacement coefficient in the range of 0.40-0.45, the injection of optimized chemical slugs provided an incremental recovery of 0.24 to 0.44 of the original oil in place. The most effective formulation was a three-component ASP system comprising 0.1 wt% NaOH, 0.023 wt% sodium dodecylbenzenesulfonate, and 0.05 wt% HPAM, delivering an incremental displacement coefficient of up to 0.437. The underlying mechanism is attributed to a synergistic effect: the alkali reacts with naphthenic acids in the crude to generate in-situ surfactants; the synthetic surfactant further reduces the oil-water interfacial tension to ultra-low values; and the polymer increases the aqueous phase viscosity, thereby improving mobility control, stabilizing the displacement front, and enhancing macroscopic sweep efficiency. The conducted research confirms the high potential of combined chemical EOR methods for improving the recovery of high-viscosity oils in Kazakhstan. This approach enables the production from poorly swept zones and can significantly increase the ultimate recovery factor in mature fields with challenging geological and physical properties.
Source: Neft i gaz
Language: English
Subfield: Fuel Technology
Field: Energy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W7124896835