Experiment and Simulation of Indigenous Microbial Enhanced Oil Recovery (IMEOR)
Authors: Yao Chuanjin , Lei Guanglun , Ma Jiye , Wu Chuan , Li Wenzhong 
Published: March 2015

Abstract
Under the laboratory simulation of HTHP reservoir (65?, 11MPa), the indigenous microorganisms in Z3 Block of Sinopec Shengli Oilfield were activated selectively; the total number of bacteria, the surface tension of aqueous solution, the change of oil viscosity and the consumption of activating nutrient during activating were tested. Then, the physical simulation experiments of indigenous microbial flooding were performed. According to the main mechanism of IMEOR, the mathematical model reflecting the metabolism, growth and reproduction of indigenous microorganisms, the migration of component and the change of fluid properties was established. Using the orthogonal design method, the program optimization and economic evaluation involving three parameters of activating nutrient concentration, air injection quantity and injection PV were carried on. Then according to the actual situation of oilfield, the optimal program was proposed and the numerical simulation of Z3 Block was performed. The lab results show that taking the corn syrup powder (carbon source, best concentration 0.3%) and (NH4)2HPO4 (nitrogen and phosphorus source, best concentration 0.3%) as the main activating nutrient, the microorganisms can be activated successfully. Under the condition of optimal activating nutrient concentration, the total number of bacteria is above 2×108 cell/mL after 12 days; the surface tension of bacterial liquid reduces only a little; the oil viscosity reduces by 15% and the corn syrup powder concentration reduces from 0.3% to 0.05% about 15 days. Core flooding experiments indicate that the indigenous microorganisms can enhance oil recovery about 8.5% after water flooding. The program optimization results show that the optimal program is that the concentration of activating nutrient is 0.7%, the liquid-gas ratio of air injection is 1:12 and the injection PV is 0.3PV. According to the actual and optimization results, the optimal program suitable for oilfield is as follows: the total nutrient injecting slug is 0.3PV (6 years) with in each cycle (20 days), injecting the activating nutrient for 1 day and the rest 19 days, injecting water and air. The forecasting enhanced oil recovery is 5.97%, increasing oil 16.84×104t.

Introduction
At present, many oilfields in the world have entered the high water-cut time, facing the problems of quick production decline, big difficulty of stable production and low recovery. Therefore, how to enhance oil recovery further becomes a question urgently to be solved currently. As a new tertiary recovery technology, compared with other technologies, MEOR (microbial enhanced oil recovery) especially IMEOR (indigenous microbial enhanced oil recovery) has many advantages. It can adjust to the reservoir better, its cost is lower with simple equipment and construction and it does not pollute the environment and damage the reservoir and thus, it has a good application prospect (Cheng et al., 2006). Now, large-scale application of this technology has been reported in Russia, Russia, Norway and so on and obtained better effect (Awan et al., 2006). In China, it has been applied in Oilfields of Daqing, Shengli, Dagang, Xinjiang and so on, and achieved significant effect of water decreasing and oil increasing (Cheng et al., 2005; Chen et al., 2006; Zhang et al., 2008). However, the MEOR mechanism and numerical simulation software need to be performed further.