The Use of Cyclic Injection of Xanthan Solution in order to Increase the Oil Recovery Factor from Heterogeneous Terrigenous Reservoirs

Abstract

As oil reserves are depleted during the development of an oil deposit in an elastic-water-pressure mode, the water cut of the fluid gradually increases, reducing the efficiency of waterflooding and maintaining reservoir pressure by the system of injection wells. The rheological characteristics of the saturating fluid and the structure of the reservoir affect the likelihood of premature watering of production wells. To increase oil production and level the displacement front, various polymer systems, both synthetic and biological, are used to promote additional oil production from previously untapped reservoir zones. There are technologies for both constant injection of a working agent with a polymer, and a slug of a polymer solution of a certain concentration with subsequent injection of water. The purpose of this work is to assess the effect of injection of xanthan solution on the oil displacement efficiency with subsequent injection of formation water. An experimental (laboratory) study was carried out on alternating injection of xanthan and formation water solutions to increase filtration resistance in flooded filtration channels. Inhomogeneous terrigenous core samples with different fracturing and filtration-capacitive properties were selected as a physical model for carrying out the experiments. The main results of the laboratory study are the dependence of the oil recovery factor and water cut on the injected volume of formation water. It is noted that the key factor in reducing the displacement efficiency after injection of a polymer slug is the loss of polymer molecules both after adsorption on the rock and during further filtration of formation water through diffusion. As a result of the experimental study, it was revealed that changing the filtration rate can have a beneficial effect on the involvement of oilsaturated rock in the displacement process due to the sealing of watered areas when the injection pressure changes.