Abstract

In this paper, an oil recovery process has been studied by injecting sodium metasilicate (Na2SiO3·9H2O) solution to form blocking gel with CO2 in larger permeability flow passes. The Na2SiO3·9H2O solution is an alkali to reduce interfacial tension (IFT) reduction. The two functions of reducing IFT and blocking channeling thief passes formed by Na2SiO3·9H2O solution and CO2 gas were investigated. The experiments were carried out to characterize and evaluate the gel system based on gelation time, gel strength, and gel stability through the effecting factors such as Na2SiO3·9H2O concentration, pressure, temperature, salt (NaCl), and divalent ion (Ca2+). The blocking performance of gel was also investigated using gas permeability test using Berea sandstone saturated Na2SiO3·9H2O solution. Furthermore, the numerical simulations on the effectiveness of blocking gel on oil production were carried out using with 2D heterogeneous reservoir model by CMG-STARS. The simulation results showed that cumulative oil production was increased 73% of the residual oil by blocking water channel thief zone by gel formation compared with that of water flooding.

Introduction

Oil is a fundamental energy source and also an important chemical raw material. 95% of world-wide oil production is used to provide energy purpose. However the oil resources are being depleted rapidly. In addition to increase the oil production replying the growing global demands of fossil fuel, some oil recovery operation and technique have been developed from primary, secondary and tertiary process to enhance the oil recovery. Tertiary recovery is the most important method used to remove the residual oil trapping the pore space in reservoir which cannot be produced by primary and secondary process.

The water breakthrough has been a main problem during the enhanced oil recovery (EOR) process in the heterogeneous reservoir consisting of fracture or a short-cut layer with much higher permeability than other layers has a problem resulting in low oil recovery ratio.

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