Abstract

The Bakken Formation is an extremely tight formation with low porosity and permeability. Activity in developing such an unconventional play has increased due to the success of horizontal drilling coupled with multi-stage hydraulic fracturing stimulation. However, due to high capillary trapping the primary recovery factor in the Bakken remains rather low. Therefore, small improvements in productivity of Bakken wells by applying enhanced oil recovery could increase the recoverable oil by billions of barrels. Among several EOR options, CO2 flooding may be effective to increase the recovery factor. In this paper, numerical simulation is used to evaluate the performance of CO2–EOR for the Bakken Formation. There is also a strong interest in coupling reservoir fluid flow with geomechanics to study the stress and deformation of reservoir rock thoroughly. In this work we used coupled code to study the interactions between reservoir flow and geomechanics to model the deformations and stresses in a CO2-EOR process.

1. INTRODUCTION

Gas injection is an effective enhanced oil recovery method in naturally fractured or hydraulically fractured tight formations. Recent studies showed that CO2-EOR could be a viable method to increase recovery in tight shale plays. The Bakken reservoir of Williston Basin is one of such tight plays composed of an upper shale member, a middle member of sandstone and siltstone, and a lower shale member. Activity in developing the Bakken Formation has increased due to the success of horizontal drilling coupled with multistage hydraulic fracturing stimulation [1]. However, maintaining production— which may be acquired by hydraulic fracturing and well stimulation— is quite challenging for this type of wells. Hence, the primary recovery factor in the Bakken Fm remains very low estimated less than 10% of the original oil in place [2- 5].

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