Thermo-electric-chemical synergy strategies for ultra-heavy oil recovery: field evidence from Chunhui Oilfield

Abstract
With the depletion of conventional resources, the development of ultra-heavy oil has become strategically vital. The Chunhui Oilfield in Xinjiang represents a typical shallow, thin-layer reservoir with million-centipoise viscosity, posing significant recovery challenges. This study systematically analyzes production data from multi-cycle thermal operations, incorporating the field application of electrical heating as an auxiliary energy source to enhance thermal efficiency—300 kW medium-frequency wellbore electric heating devices were deployed in 2 typical test wells (P1, P3) during the 3rd huff and puff cycle, with heating sections covering the oil layer to wellbore bottom (180–350 m) and real-time monitoring of energy consumption, temperature field evolution and production performance. We investigate the evolution of the subsurface temperature field under combined thermal-electrical stimulation and its controlling mechanisms on production performance. The concept of “thermo-electric coupling” is proposed and quantified, by introducing the comprehensive energy efficiency coefficient = (cyclic oil production × crude oil calorific value) / (steam thermal input + electrical heating energy consumption) to characterize the synergistic effect of steam and electrical heating, clarifying the impact of key parameters such as energy input intensity (steam/electrical) and cycle timing on overall energy utilization.

Field data reveal a critical production-temperature response inflection point at 70–75 °C, which is objectively identified and verified by the piecewise linear regression method with F test (
P
 < 0.01) based on 126 groups of valid production data from 3 wells, indicating a shift in crude flow from a viscosity-dominated to a mobility-dominated regime. Furthermore, this study explores the synergistic mechanisms of viscosity reducers during low-temperature phases and proposes an integrated thermal-electrical-chemical collaborative development strategy, and quantitatively evaluates its economic benefits and energy efficiency performance based on field cost and production data. This approach emphasizes “thermal recovery (steam/electrical) as the foundation, chemical enhancement as a supplement, and relayed production modes.”

The findings provide theoretical and practical guidance for the efficient development of similar ultra-heavy oil reservoirs, particularly in optimizing energy integration and power-assisted recovery processes. Distinguished from existing studies that only focus on steam parameter adjustment for cyclic steam stimulation optimization, this study pioneers the combination of wellbore electrical heating with steam huff and puff to form a thermo-electric coupling auxiliary mode, and fills the research gap of integrating chemical viscosity reduction with thermo-electric assistance in the low-temperature stage of shallow ultra-heavy oil reservoirs. These insights are also expected to inform enhanced recovery strategies in other challenging reservoirs.