Experimental Study On The Mechanism Of CO₂ Huffing And Puffing For Deep Heavy Oil Vertical Well Injection

Our country is rich in heavy oil and asphalt,which account for more than 20%of the national petroleum resources.Sha 3 interva of Shengli Oil Field is a deep heavy oil reservoir of the national four heavy oil production bases.It has several characteristics,such as high viscosity,low porosity,low permeability and deep burial,etc.Generally,regular test for heavy oil is not effective.The results of the experiments taken in the target reservoir are not ideal by existed technologies,namely thermal recovery technology,micro emulsion technology of viscosity reduction and.viscosity agent + auxiliary supercritical CO2 gas injection technology.The target oil reservoir contains lots of vertical oil layers,so it is not suitable to use the horizontal well.Through technology researches,we decide to exploit the target heavy oil reservoir by the way of the vertical injection CO2 stimulation.Therefore,it is significant to study how the stimulation mechanism of deep heavy oil reservoir in vertical wells with CO2 injection can enhance promotion.In this article,the author is first to carry out experiment and research of CO2 injection into formation fluid based on compounding of original formation fluid gas-oil ratio and tests of relationship between heavy oil and temperature,water rate of crude oil,formation fluid group.Researches mainly focus on effect of CO2 injection to formation oil viscosity,dissolved gas-oil ratio and crude oil volume factor.Specialties of reservoir properties have been researched,counted and analyzed.An artificial three-dimensional core has been made according to similarity principle.Moreover,tests on the large artificial three-dimensional core have been carried out in aspects of penetration rate,void ratio,mineral composition,microstructure of reservoir rock and mechanical property so as to prove that the artificial three-dimensional core is in conformity with the natural one.Therefore,the artificial three-dimensional core can replace the natural one in three-dimensional physical simulation experiment.With three-dimensional physical model to start increasing oil simulation experiment of throughput by injecting CO2 into heavy oil vertical well.Study the pressure change,diffusion rule of CO2 of the multiple injection of CO2.Compared with the results of data stimulation to get the diffusion rule of CO2.Two groups of experiments have been carried out to study the effect of injection volume,injection speed and throughput cycle on the increase of oil.Analyze the oil viscosity,produced oil component and combine the experiment with the result of stimulation to figure out the mechanism in throughput increase of oil by injecting CO2 into deep heavy oil.