CO₂ Injection For Enhanced Oil Recovery In Tight Oil Reservoirs （CMG）

There are basically four different techniques to enhance oil recovery and extract30-60%of the stock,rather than the 20-40%recoverable with conventional methods.First of all,it’s possible to inject gases（natural gas,nitrogen,CO₂）into the well to extend the pressure and,sometimes,reduce the viscosity of the hydrocarbons.The injected gases remain trapped within the well.this system can therefore combine increased oil recovery and geological storage of CO₂.Chemical solutions of diluent or surfactant may also be wont to reduce surface tensions and capillary pressure in oil wells.The injection of selected microorganisms could be a means of reducing the length of the carbon chains while generating in place surfactants and CO₂which reduce the viscosity of the oil.Finally,the injection of steam reduces the viscosity and vaporizes a fraction of the oil.The process to understand the CO₂injection into a reservoir is an important step CO₂injection was investigated in the Bakken reservoir,which is rich in tight oil.Also,it is significant to investigate about the potential of applying Enhanced Oil Recovery methods to increase the oil recovery there.As we know,it is a subject which is not understood properly in unconventional reservoirs such as the Bakken.For that,a compositional simulator called CMG GEM will be used.Although,the fluid model is built by using CMG Winprop,the components are distributed into 7,with their different compositional data for the Peng-Robinson EOS in the Bakken formation.It is used to determine the PVT properties,also know the Minimum Miscibility Pressure.Then after,the result is saving with GEM EOS Model,and will be imported to CMG GEM for the reservoir model.For the case,we set up the reservoir with 4 effective hydraulic fractures,after that,the Huff-n-Puff process.The total production of the well is 30 years.However,the investigation of different parameters such as:fracture width,half-length,injection pressure,injection rate,length of soaking period is listed by the sensitivity analysis.After all,a lower permeability,longer fracture half-length,and more heterogeneity are much favorable for the CO₂Huff-n-Puff process.