Experimental Investigation of Produced Gas Re-Injection in a Tight Danish North Sea Oil Reservoir

Most of the Danish oil and gas is produced from Upper Cretaceous reservoirs, located in the North Sea. The rock is mainly composed of chalk with some clay minerals as an impurity. Chalk is commonly considered tight, although it typically has high porosity but low permeability. However, to adjust the increasing demand for hydrocarbons, there is increasing interest in extraction of petroleum from less favorable reservoirs like the tight, high porosity, low permeability, fractured, mixed sediment formations in the Lower Cretaceous. Lower Cretaceous oil reservoirs in the Danish part of the North Sea, are generally deep, with high porous but too tight rock in terms of permeability, which makes the applicability of any EOR method and any reservoir development plan challenging. It seems that the only feasible EOR method could be gas injection, and one of the targeted gases for injection could be associate produced gas which has good compatibility with the reservoir fluids. To date, research on investigating drive mechanisms, relative permeability measurements under different production mechanisms and the feasibility of gas injection are conducting. Therefore, this research aims to evaluate the potential of produced gas re-injection on incremental oil recovery in a Lower Cretaceous oil reservoir.