Application Of CO₂ Flooding Technology To The EOR Of Oil Reservoir With Low Permibility

Along with the oilfield development, water injection development in NM low permeability oilfield of Liaohe oilfield company become difficult, which is the constraint of effective produce reserves. As the characteristics of the low critical pressure, low viscosity, easy compression, et al, the injection capability of CO2 is significantly higher than water, and its flow resistance is small, the effective displacement system is more easily to establish. Therefore, based on the displacement mechanism of CO2, by conducting CO2 injection test, the displacement effect of CO2 is evaluated, the technique of oil displacement by CO2 injection is developed, giving a support to the oil field development which is difficult to use water injection.N1 block of NM oilfield is chosen as the test field of CO2 displacement in this article, on the basis of geological structure and development situation in this area were analyzed detailed, the lab research work were focused as follows:1. According to the characteristics of CO2 displacement, on the conditions of the simulated oil reservoir, expansion test, slime tube test and long core displacement test are carried out, by introducing the concept of miscible coefficient, the mechanism of CO2 displacement is further enriched, and the feasibility of the technology is approved in the N1 test block.2. The reservoir inversion is predicted by JASON software, and on the basis of well-seismic interpretation result, the geological model is established, the fault, structure, porosity, permeability, oil saturation, five models is completed. By the simulation of main reservoir, geological reserves is 284.4×10t, compared with the volumetric method, the relative error is 2.14%, the initial calculate reservoir pressure is 15.37MPa, compared with the measured value, the relative error is 2.50%. By the simulation of Block and single well dynamic index with the model, the results proves that the model is basically conform to the actual, and the it can be used to the plan optimization and development index prediction.3. By the fitting of single flash PVT experiment, the fitting value and experimental value of saturation pressure were compared, the relative error is 3.08%, single flash oil and gas ratio, formation oil density, degassed oil density, and other parameters are satisfied the requirement of numerical simulation. As the results of expand experimental by gas injection shows, the fitting results of viscosity, expansion coefficient are good, which can fulfill the requirements. By the data fitting of preliminary experimental for N1 block, the phase state characteristics of actual formation fluid, as well as the critical parameters which can support the numerical simulation were obtained.4. According to the classification principles of layer group, four layers of K1jf11, K1jf13, K1jf21, K1jf22 were determined as the objective test layer for gas injection, through comprehensive analysis of stratum fracture, injection pressure of CO2, degree of sand control, strength of injection-production, and many other factors, The five point well pattern was finally determined.5. According to drilling data of dense well pattern, combined with well location in N1 test block, data of small layers, results of sedimentary facies, and et al, considering the heterogeneity distribution and the well point information, using Petrel software to establish the three-dimensional geological model, by numerical simulation of the reservoir, injection-production parameters were optimized, including injection-production capacity, injection-production system, time and manner of gas injection and production, which laid a solid foundation for the effective development of low permeable reservoirs.