Research On High-efficiency Development Model Of Offshore Long-span Thin Interbed Reservoir

Located in the central and southern Bohai Bay,P Oilfield belongs to a long-span thin interbedded lithologic-structural oil reservoir,which characterized by shallow burial and high reserve abundance.Under the condition of general combined injection-separate production and development mode of main strata in the early stage,a series of complicated problems have emerged in oilfield development,mainly showing the main contradiction of "low recovery percent of reserves corresponds to high water content,high remaining recoverable reserves".For this kind of thin interbedded oil fields with multiple oil groups,large span of oil-bearing sections,strong heterogeneity and great difficulty in vertical equilibrium utilization,layer series reorganization is an important means to reduce interlayer interference and improve oil recovery ratio in the middle and later stages of oil field development.Starting from various geological data,laboratory test data and production data of the oilfield,we conducted research on the high-efficient development mode of the oilfield by using reservoir engineering methods and numerical simulation technology,and have obtained corresponding research results in the paper:(1)The reservoir cores drilled were tested by laboratory phase permeability experiemt,and the characteristics of oil-water multiphase percolation in the reservoir were studied.Next,the influences of oil-water multiphase percolation and effective reservoir longitudinal highly dispersive(permeability difference,crude oil viscosity difference and reservoir thickness difference)on efficient development of the oilfield were analyzed.At last,the difficulties of efficient development of the oilfield were determined.(2)Using the non-piston displacement theory of oil-water two-phase in seepage mechanics,we studied the seepage dynamics of oil-water two-phase in single-layer water flooding process.According to the approach method on stream tube,we conducted isochronous superposition to the horizontal and vertical multi-flow tube water flooding dynamics,and obtained the total production dynamic characteristics of production wells during multi-layer commingled production.We also studied the influence of multi-layer vertical heterogeneity on the balanced development of oil fields.(3)Based on the strong heterogeneity of thin interbedded reservoirs,we established a numerical simulation heterogeneous model with actual geological characteristics,analyzed the utilization situation of vertical oil groups during commingled production,and cleared that the main factors affecting interlayer interference in balanced development of oil fields are"permeability and crude oil viscosity".We quantitatively studied the interlayer interference coefficient using typical well production data,high pressure of fluid physical property data and field layered productivity test data measured in the laboratory,etc.(4)Taking the North Block 1 of P Oilfield as the target block,we carried out a systematic evaluation study on the current development mode and the effectiveness of well pattern,and determined the necessity of layered development from the perspective of vertical balanced utilization.We introduced and established a comprehensive evaluation mathematical model of economic boundary and lower thickness limit,and determined the adjustment boundary of the layer series of reservoir development.We designed and optimized the layered division and reorganization scheme with the North Block 1 as a typical block.(5)According to the actual production data of the North Block 1 of P Oilfield,we studied technical countermeasures to improve the development effect by using reservoir engineering methods and numerical simulation,and conducted supporting research and put forward technical policy indicators such as well pattern and well type,pressure maintenance level of formation,oil production rate,injection-production ratio,etc.