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

Abstract

Spontaneous imbibition has emerged as a crucial mechanism for enhancing oil recovery in tight oil reservoirs. However, most of the existing spontaneous imbibition experiments have been static in nature. The dynamic effects of fluid flow, fluid type, displacement pressure, and fractures on the imbibition oil recovery have not been adequately addressed in previous studies. To fill this gap in knowledge and gain a comprehensive understanding of the mechanisms underlying surfactant-aided dynamic spontaneous imbibition, we conducted a series of experiments on tight cores extracted from the Chang 8 formation in the Ordos Basin in Northwest China. The experiments comprised static imbibition, dynamic imbibition, and water flooding displacement, and the impacts of fractures, temperature, type of imbibition fluid, and flow rate on imbibition recovery were analyzed. The results of the experiments showed that fractures have a significant impact on the imbibition oil recovery rate, with the ultimate recovery factor of the fractured core ranging from 16 to 29%, which is higher than that of the matrix core. Dynamic imbibition, on average, resulted in a recovery of 16%, which was higher than that with static imbibition. The use of surfactant solutions enhanced the oil recovery of cores, particularly in dynamic imbibition processes. This was attributed to the acceleration of emulsification between surfactants and crude oil, which led to an increased imbibition rate and oil recovery factor. Displacement was found to be an effective method for recovering the oil not produced through imbibition. The total oil recovery factors of the core samples after imbibition and displacement are in the ranges of 25% and 61%. This study is aimed at investigating the underlying mechanisms of various imbibition processes and examining the influence of various factors on the efficiency of spontaneous imbibition, with the ultimate goal of recovery enhancement in tight oil reservoirs.

Surfactant-Enhanced Assisted Spontaneous Imbibition for Enhancing Oil Recovery in Tight Oil Reservoirs: Experimental Investigation of Surfactant Types, Concentrations, and Temperature Impact

“…Spontaneous imbibition, as a crucial process for enhancing oil recovery in shale and tight formations, has gradually gained recognition. Imbibition is a prevalent phenomenon across various natural sciences, referring to the process wherein a wetting liquid, driven by capillary forces, displaces a non-wetting phase as it enters a porous media [1][2][3][4]. Imbibition can be classified into co-current imbibition and counter-current imbibition based on the flow direction of the wetting and non-wetting phases [5,6].…”

“…Adding an appropriate amount of surfactant can significantly reduce the IFT between oil and water [19]. Surfactants can also change the wettability of the rock surface [3], and emulsified crude oil forms such as O/W or W/O emulsions. To date, the various surfactants studied include anionic surfactants [20][21][22][23][24], cationic surfactants [25], nonionic surfactants [26][27][28][29], and zwitterionic surfactants [30][31][32][33].…”

“…Drawing on extensive research in the literature [3,14,36,37], three surfactants, including sodium dodecylbenzene sulfonate (SDBS), cocamidopropyl betaine (CAB), and C12-14 fatty alcohol glycoside (APG), were selected for experimentation. Among them, SDBS is a commonly used anionic surfactant, CAB is a zwitterionic surfactant, and APG is a kind of non-ionic surfactant.…”