Study On CO₂ Phase Behavior Of Heavy Oil Reservoirs Under The Third Part Of Shahejie Formation In Block X

Globally,the reserves of heavy-oil resources are enormous.In china,the reserves of heavy oil and bitumen resources occupied 20%of the domestic total petroleum reserves proportion.Thermal techniques were commonly applied for the heavy oil and bitumen recovery in domestic and overseas,but these stimulations are only suitable for the reservoir which presents a premium geophysical property.In contrast,when the reservoir presents a low porosity,low permeability and deep burial condition,applying thermal techniques cannot obtain a higher productivity index.Various existing in-situ technologies such as micro-emulsion technology for reducing viscosity and viscosity reducer assisted with supercritical CO2 injection technology were applied in purpose reservoirs,but the performances are not satisfied.Through investigation,for the purpose reservoir decided to use CO2 huff-n-huff well stimulation.Therefore,there is a great significance to study the phase behaviors of the injection CO2 under the reservoir condition.This paper,firstly dispensed the model original formation fluid according to the in-situ gas oil ratio(GOR),and obtained some basic parameters via PVT experiments such as bubble point pressure etc.,then figured out the components of the fluid,which are based on the composition of single degassing and deoiling.Conducted the multiphase expansion experiment after injecting CO2 to the model original formation fluid,and analyzed the parameter trends such as GOR,viscosity,density,volumetric factor,expansion coefficient,and bubble point pressure for different CO2 injection proportion.Furthermore,fluid properties and multiphase expansion experiments were analyzed for the heavy oil reservoir X region shahejie ?-early formation by using phase simulation software.At the same time,figured out the phase equations of the realistic formation fluid states,which can provide some primary parameters for the further CO2 injection numerical simulation test.Via pressure-decay method,testing the CO2 diffusion factors for degassed crude oil and live crude oil,plus,CO2 diffusion factors under different viscosity condition of crude oil.Finally,the impacts of diffusion factor related to crude oil properties were investigated,and established the CO2-oil system turbulence diffusion mathematical model as well.