Chemical EOR Efficiency for Ultra-Low Permeable Shale Deposits

Abstract

The purpose of the article is the search and development of water-soluble chemicals for the successful drainage and impregnation of low-permeable shale oil formations. The main problem for shale oil deposits is ultra-low water permeability. We are dealing with the cores of the Bazhenov formation, which have permeability of 10 mkD, nano-porous matrix with natural cracks. In the paper we have collected and examined the mechanisms that prevent water from penetrating into core samples with low permeability, and suggest chemicals that can help overcome this problem. Complexes of different surfactants, polysurfactants, nanoparticles with modified surface were investigated. Wettability, interfacial tension measurements, adsorption, micelles formation and phase behavior experiments were held in order to select the most effective chemical agent. A "funnel" of experimental search was performed and two best surfactants and composition of surfactant with nanoparticles was figured out. Then, for the first time, displacement experiments were carried out through the consolidated core samples of the Bazhenov formation, and the displacement efficiency of 53% was obtained. Due to the fact that the injection pressure turned out to be very high, and there were also problems associated with the adsorption of surfactants. The further steps to improve the experimental study were discussed.