Experimental Mechanism for Enhancing Oil Recovery by Spontaneous Imbibition with Surfactants in a Tight Sandstone Oil Reservoir

Abstract

This study aims to investigate the mechanism behind surfactant enhanced oil recovery under reservoir conditions through experiments on spontaneous imbibition with surfactants. The tight sandstone samples are characterized using cast thin section (CTS), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR) to determine their clay mineral composition, pore size distribution, and fluid distribution. Spontaneous imbibition experiments are then conducted using formation water and surfactant solutions as imbibition liquids, with three different types of surfactantsdodecylbenzene sulfonate (DBS), sodium dodecyl sulfate (SDS), and ammonium bromideat two different concentrations, each to examine the effect of surfactant type. Additionally, the interfacial tension (IFT) between crude oil and different imbibition solutions is measured, and the contact angles of an oil droplet on the core surface in air, formation water, distilled water, and surfactant solution are determined. Finally, the effects of IFT, rock wettability, formation water salinity, and core permeability on final oil recovery by spontaneous imbibition are analyzed. The results indicate that surfactant-assisted spontaneous imbibition primarily operates through IFT reduction, wettability alteration, and emulsification of crude oil. However, ultralow IFT may lead to low ultimate oil recovery. To increase the ultimate oil recovery of spontaneous imbibition, reducing the salinity of the surfactant solution and creating microfractures can be effective strategies.

Experimental Study of Surfactant-Aided Dynamic Spontaneous Imbibition in Tight Oil Reservoirs: The Effect of Fluid Flow, Displacement Pressure, Temperature, and Fracture

“…Both core 4 and core 6 used the deionized water as an imbibition liquid, but 0.2% SDBS is added in the deionized water for core 4. Deionized water has the ability of emulsification and wettability alteration . The IFT between deionized water and crude oil is 16.62 mN/m and is greater than that of the deionized water with 0.2% SDBS and crude oil (2.90 mN/m).…”

“…In previous research endeavors, an extensive investigation into the mechanistic aspects of various surfactants was conducted. It was ascertained that the reduction of surfactant solution salinity and the promotion of microfracture formation represent effective strategies for enhancing recovery rates . Consequently, in this study, we exclusively employed varying concentrations of sodium dodecyl benzenesulfonate (SDBS) as the chosen surfactant-assisted oil recovery strategy.…”

“…Simultaneously, the effects of factors such as fracture distribution, temperature, displacement pressure, and surfactants on the imbibition process are currently the focal points of research. − In fact, numerous scholars have conducted extensive research on various influencing factors through laboratory experiments, mathematical models, and numerical simulations . For instance, Wang and Yue proposed a comprehensive mathematical model that integrates various aspects of fracture distribution in imbibition processes within tight rock formations, encompassing parameters such as fractal dimension, the number of fractures, fracture size, and their influence on the imbibition mechanisms.…”

Quantitative Analysis of Crude Oil Mobilization in Microscopic Pores during the Spontaneous Imbibition of CO2-Enhanced Fracturing Fluids in Shale Oil Reservoirs

“…Shi et al highlighted the superior imbibition rate of water phases over oil phases using organic shale samples from the Horn River Basin. Zhu et al argued that the combined effects of capillary force, low initial water saturation, and osmotic pressure drive the imbibition of fracturing fluids in shale formations. ,− …”

Study on the Evolution Law and Mechanism of Fracture Imbibition in Loaded Coal Based on Micro-CT

“…At present, many scholars have studied the imbibition process of shale, fractured gas reservoir, and sandstone through laboratory tests, − but there are few studies on coal imbibition. Yue et al − used the traditional slice method, water-sensitive indicator method, and resistivity method to study the evolution behavior of water absorption volume and water absorption height of coal with water absorption time in the process of self-absorption.…”