Surfactant Huff n Puff Field Trials in Eagle Ford Shale – A Treatment Design Comparative Analysis

Abstract

Abstract This investigation focuses on contrasting surfactant huff ‘n’ puff (HnP) treatments in two Eagle Ford Shale wells, specifically examining the influence of a polylactic acid (PLA) diverter used in the second. This work demonstrates surfactants as an effective enhanced oil recovery (EOR) strategy and highlights how the treatment design can impact the recovery outcome. This work presents an in-depth field analysis with supporting laboratory experiments and statistical modeling to evaluate the surfactant's performance in both wells. Laboratory tests assessed surfactant efficacy in altering wettability and facilitating spontaneous imbibition in the presence of the PLA diverter and with different Eagle Ford samples. Post-stimulation monitoring of produced water for total dissolved solids (TDS) and surfactant concentration demonstrates the extent of treatment dispersion to the formation. A statistical model established performance expectations in the absence of surfactant treatment as a basis for evaluating the effectiveness and uncertainty of EOR uplifts. Both field trials demonstrated significant improvements to oil recovery, uplifting oil rates from two to five times the production rates before treatment. 95% of the injected surfactant remained adsorbed within the reservoir leading to improvements persisting with a continued recovery uplift extending beyond two years and incremental recoveries ranging from 2,200 to 4,000 barrels of oil. The implementation of a polylactic acid (PLA) diverter in the second trial succeeded in dispersing the treatment throughout high and low-conductivity fractures. This tailored approach led to a more moderate but sustained incremental oil recovery, highlighting the diverter's strategic impact for future stimulation designs. Additional laboratory results underscored that local variations in Eagle Ford reservoir characteristics and the altered fluid dynamics introduced by the PLA diverter did not substantially impact surfactant performance. Crucially, this research elucidates the PLA diverter's impact on surfactant HnP treatment outcomes, expanding on design strategies for EOR in unconventional reservoirs. Despite limited improvements with diverter for this specific treatment, these findings indicate potential benefits of controlled diversion for larger treatments and higher producing wells. This contribution is pivotal for refining EOR methodologies, and optimizing surfactant treatments for effective and efficient recovery strategies tailored to the unique challenges of unconventional reservoirs.