Chemical and microbial characterization of North Slope viscous oils for MEOR application

Abstract

Viscous oil reservoirs tend to be low-energy, low-gas/oil-ratio systems with high viscosities and are difficult to produce, transport and refine by conventional methods. Some of the commonly considered viscous oil recovery methods include processes such as steam flooding, in-situ combustion and miscible gas injection. The large viscous oil deposits in the ANS cannot be produced entirely by conventional methods like pressure displacement or waterflooding. Other methods such as miscible (gas injection and water alternating gas (WAG) also have limited success. Microbial enhanced oil recovery (MEOR) is one of the techniques for improving the oil recovery for viscous deposits. This method has not yet been applied to the ANS fields. This study includes experimental work to analyze the application of MEOR to the ANS oil fields. A microbial formulation was developed in order to simulate the MEOR. Coreflooding experiments were performed to simulate the improved recovery oil recovery and quantify the incremental oil recovery. Properties like viscosity, density and chemical composition of oil were monitored to propose a mechanism of oil recovery. Terminal restriction fragment length polymorphism (T-RFLP) was performed on the oil samples to qualitatively study the effect of the microbial formulation on a molecular scale.