Study On Development Scheme Design Of CY Oilfield

As a typical ultra low permeability oilfield,CY oilfield is characterized by many oil-bearing layers,long oil-bearing sections,complex fracture structures,great lithologic changes,poor reservoir physical properties,insufficient natural energy,and difficult water flooding development.Scientific and reasonable deployment of development plan is of great significance to guide efficient development of oil fields.Taking the main oil-bearing strata of CY oilfield as the research object,the complex structure is carefully combed through the combination of well and earthquake,and the relationship between fault assemblages is implemented.Carry out regional stratigraphic analysis and fine stratigraphic,oil group and small layer correlation division,to determine the connection relationship;carry out sedimentary study,characterize reservoir distribution,and determine the development area of sand body;Deepen the oil test and production test analysis,combined with reservoir engineering methods,carry out natural energy evaluation,and analyze the feasibility of gas injection development;to carry out development technology policy research on reasonable development strata,well pattern and well spacing,development mode,single well productivity,pressure maintenance level,injection parameters and so on.Under the guidance of the above research,the pilot test area scheme is designed and the development effect is predicted.Geological research shows that CY oilfield has complex geological conditions,high dip angle,developed fault system and low reservoir permeability.By comparing the effect of similar developed reservoirs,calculating the characteristic parameters of CO₂ flooding and predicting the effect of numerical simulation,it is considered that the development of CY Oilfield by CO₂ injection is feasible.According to the optimization analysis,the pilot test area can be divided into three sets of development strata,including 0-I oil formation,II-IV oil formation and V-VI oil formation.The well pattern is top row staggered gas injection development well pattern with injection production well spacing of 250 m.The optimization of CO₂ injection parameters shows that when the total injection rate is 0.5 HCPV and the daily gas injection rate of single well is 1.4×10⁴ m³·d^-1.When the injection production ratio is maintained at 1.0 and the injection pressure of the injection well is less than or equal to 37MPa,a better development effect can be obtained.Under the guidance of the above development principles,a total of 11 injection production wells are designed in the pilot test area,including 7 new wells,4 old wells,7 production wells and 4 injection wells;It is predicted by numerical simulation that after the implementation of pilot test area scheme,the daily oil production of single well can reach 10 t·d^-1 in the initial stage,and the annual production capacity can be maintained at 2.1×10⁴ t in the first four years,the final recovery rate of CO₂ flooding is expected to reach 45.3%.