| After many years’ exploration and development of Putaohua reservoir in Gulongnanregion of Songliao basin，large areas of oil and gas reserves have been found in the nosestructure subject area, central syncline and slope transition zone of the depression, but thereare many differences among reservoir type, oil and water distribution, key controlling factorsof reservoir forming and the pattern of oil reservoir，it’s in sore need to research into thehidden laws of the system. In this paper, by the guidance of high-resolution sequencestratigraphy, reservoir sedimentology and reservoir dynamics theory, and on the basis of theisochronal stratigraphic framework of Putaohua reservoir, comprehensive analysis ofprovenance of system, sedimentary microfacies, valid source rocks, transporting passage,positive tectonics, excellent reservoirs and reservoir profile, we establish a large concavepartition accumulation mode, which has important significance for guiding oil and gasefficient exploration and development of similar area.Aiming at the shallow water delta reservoir sedimentary characteristics of Putaohua oillayer, firstly, different classes lake flooding surfaces are taken for same period surface, andPutaohua reservoir can be divided into1long-term cycle,2medium-term cycles,12short-term cycles.We established single sand body level isochronous stratigraphic frameworkin the study area. And then put forward a new sequence framework of synsedimentarytectonic uplift in the Putaohua reservoir from north to south gradually thinning. The study ofheavy minerals, formation thickness and fine anatomy of dense well pattern sand ofdevelopment area indicates that the study area is in a shallow water delta sedimentary system,which is collectively controlled by the west provenance and the northern provenance, thedistributary channel sandbody and all kinds of sheet sand accused by river waves are the mainmicrofacies and mouth bar microfacies doesn’t develop well. Three kinds of depositionalmodel were summarized, which are delta front subfacies offshore (river-dominated), centralcoast (river-dominated mainly) and far offshore (river waves-dominated). Reservoir finedissecting showed that there exists areal accumulation characteristics in Putaohua reservoir,Gulongnan region: syncline retention area mainly developed all sections of pure oil and gasand oil/water inversion lump lithologic reservoir; slope transition zone mainly developedmore than a ribbon of fault-lithologic reservoir oil-water system; nose structure area mainlydeveloped lithologic reservoir normal oil-water differentiation of flake. Then oilaccumulating and main control factors in the study area are summarized:1) Effective hydrocarbon source rock control oil and gas enrichment degree and distribution;2) sourceand reservoir overpressure and buoyancy form dynamic of oil and gas migration,3) Oilsource faults and the reservoir sand body form oil and gas vertical and lateral conductingchannel respectively;4) Nose structure uplift, the reverse fault trap and the transformationand condensed faults decided oil accumulation position is tectonic position;5) underwaterdistributary channel and the main sand sheet of shallow water delta sedimentary leading edgeforming high quality reservoirs for oil and gas enrichment. Eventually, oil accumulationmodels for putaohua oil layer partition in Gulongnan region are established:1) accumulationpattern of stranded reservoir type in central syncline;2) accumulation model oflithologic-updip pinchout type in slope zone of transition;3) accumulation model of faulttype in slope at transition zone;4) tectonic accumulation pattern of fault segmentation type innose tectonic uplift zone; under the guidance of the accumulation model, we can predict2types of7favorable target area for oil and gas enrichment, submited5recommended wells,and point out the direction of the increase in oil reserve and production for Gulongnan areaPutaohua reservoir. |
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