The Structure Interpretation And Reservoir Prediction Of Sabei Transition Area

Sabei transition area is situated in northeast of Saertu arch structure of Daqing oilfieldand structural surface is tend to be higher in the southwest and lower in the northeast. The oillayer, Sertu and Putaohua, belong to the same hydrodynamic system and faults are lessdeveloped in this area. As reservoir depth increases, oil layers in Portuguese I group, II group,Sa III group and II group turn into oil-water layers gradually with decreases in sandstone andeffective thickness. This block is put into development in1989, using slash injection wellpattern with edge wells as production wells. Now the block is entered into ultra-high water cutdevelopment stage, difficulty in potential tapping and reserve replacement increases gradually.At the same time, years of water flooding development has caused changes in oil-waterdistribution of outer edges of the fourth belt in transition area, thus the existing geologicalunderstanding is not competent for oilfield development.The research is based on the tectonic background of Sabei development area, usingcomprehensive analysis and rational utilization of geological data, well logging data andseismic profile to establish a set of credible reservoir seismic-geology horizon model, carryout stratigraphic division; proceed fine interpretation on region structure and micro-structureusing seismic attributes and ant tracking technology; analyze the influences of micro-structureand small faults on oil-water distribution; based on sequence division and interfacecharacteristics, carry out researches on sedimentary microfacies and sand body geometry anddistribution through sublayer-microfacies contrast profiles under the dense well patterncontrol; block out sand body distribution range in plane by using formation sections andseismic attributes analysis technology in accordance with the sequence of " singlewell-section-plane "; take fine interpretation of sand body, including contact relation andconnectivity status by using dense well pattern logging data. Based on above study, reservoirformation conditions and oil-water distribution in transition zones of Sabei development areais analyzed and the achievements can provide technical basis for later oilfield developmentand adjustment.Main achievements of the research:1. Established high-precision isochronous correlation framework of study area andidentified9tectonic interfaces of the fifth-order sequence of Saling reservoir under therestraints of regional flooding surface, third-sequence surface, system domain surface,fourth-order and fifth-order sequence surfaces. 2. Carried out fine construction through well-seismic correlation, generalized interfacestructure map of fourth-order and fifth-order sequence, revealed structure and micro-structurecharacteristics of study area. Recognized the study area is located in the wing of transitionzone, which bended from north to east. The transition zone is a layer of steep belt with aconfiguration of micro-nosing structure protruding to northeast.3. Proceed small faults tracking and revealed their distribution characteristics by usingvarious attributes and ant algorithm. These small fractures are less developed, mostly innorth-west direction and difficult to identify in conventional methods. These faults can formsmall faulted anticline, which has certain effects on reservoir formation.4. Identified river delta system and turbidite system, divided sedimentary microfaciessuch as distributary channel, underwater distributary channel, mouth bar, frontal sheet sanddam, dam, distal crevasse channel and crevasse delta, turbidite channels, mat form turbiditefan flower (superimposed fan), revealed sedimentary facies distribution in plane and evolutionin each layer. With the application of seismic attributes and inversion, turbidite sedimentaryfacies and sand body distribution system has been studied, carried out in-depth study andprediction on development mode and distribution rules of turbidite reservoir in transition area,and described distribution characteristics of sedimentary microfacies and sand body in theturbidite system.5. Clarified oil-water interfaces distribution through study on reservoir conditions andprofitable facies, and predicted potential structural-stratigraphic trap distribution. It isconsidered that sandstone up dip pitchout and sandstone reservoirs are developed in thetransition area.