Reservoir Prediction And Hydrocarbon Accumulation Model Of Putaohua Oil Layer In Both Flanks Of Aobaota Structure

With the increasingly deepening of exploration practice and gradually improving of petroleum geology theory,at present,subtle reservoir has replaced structural reservoirs,and become the focus of mid-shallow layer exploration in the northern SongLiao basin.Due to the hidden nature of subtle reservoir itself and the complexity of accumulation process,subtle reservoir are widespread different problems such as small scale sandbodies,complex distribution of oil-water,and the indistinct cognition of accumulation process,result in the lower discovery rate of resources and poor producing effect of proved reserves.Improving the thin reservoir prediction accuracy,systematically carry out the research of accumulation conditions and main control factors,especially the control of fault,sandbodies and their combination on the distribution of oil-water is the key to improve exploration effect in this kind of reservoir.Taking Putaohua reservoir in both wings of Aobaota structural of Daqing placanticline in Songliao basin as the research object,using the detailed seismic,logging,coring,oil testing and analysis data in this area,on the basis of fine prediction of thin sandbodies distribution using well and seismic,and fault characteristics and its evolution analysis,this study analyses the oil-water distribution and main controlling factors of subtle reservoir in the area,systematic analyses the accumulation conditions of the subtle reservoir with four aspects of source,reservoir,migration and conservation,expecially dissect the controlling effect of fault and sand body on hydrocarbon accumulation,then summarize favorable oil and gas accumulation model of subtle reservoir in the area,and preferably select the increase storage potential block in the next step.This study not only provides a theoretical basis for the effect use of Putaohua reservoir in both wings of Aobaota structural,but also further enriches the theory of hydrocarbon accumulation of subtle reservoir in the slope zone.According to the delta front sandbodies characteristics of small scale,poor lateral continuity and difficulty the distribution prediction,using union method of "Seismic attributes,seismic inversion and sedimentary microfacies" to finely portray thin sandbodies distribution step by step.Take the ability to distinguish different scale of sandbodies as the discriminant standard optimizing seismic attributes,with which sandbodies spatial distribution of oil layer group was qualitatively analyzed;By using the method of high frequency and lower frequency curve reconstruction to improve the ability of curve to recognize lithology and oil content.On the basis of sparse pulse impedance inversion,step by step to archieve random inversion of gamma,porosity and resistivity,and then the spatial distribution of sandbodies and the net pay is quantitative analysized;On the basis of the sedimentary background and sedimentary facies types,establishing the well logging facies model,dissectting the distribution patterns of different types of microfacies in dense well spaceing area,as the guide,using the group of seismic attribute and reservoir prediction to lead the trend,sedimentary microfacies map in loose pattern area of the two wings is established,and then fine description of spatial distribution of different types of sandbodies in two wings.Research shows that the sandbodies thickness of Putaohua reservoir in this area become thinner from North to South,it belongs to the deposition of the shallow-water delta front subfacies,it goes through the vertical deposition process of "quick regression-stability-slowly transgressive";In North,the transitional environment between inside and outside the delta front,the main sandbodies types are intermittent trip and long strip of distributary channel sandbodies,and long strip of "channel-controlling" sheet sand,the distribution directions of sandbodies are mostly north-south and north-north-west;In South,the environment between of delta outer front subfacies and lacustrine facies,the main type is sheet shaped sheet sand and potato shaped far sand dam.In view of this situation of complex oil-water distribution and unclear reservoir type,with the method of vertical and horizontal oil reservoir profile analysis and fine anatomy of the typical oil reservoir,the main controlling factors of oil-water distribution and reservoir types distribution characteristics are researched with the awareness of fault and sandbodies.The oil-water distribution between north and south is different obviously,in North,controlled by both structure and lithology,the oil-water distribution among the fault block are different in apparent,partly affected by the poor vertical and lateral continuity of sandbodies,single sandbody becomes an independent oil-water system,the vertical superimposed sandbodies cause the phenomenon of "water high-oil low" in the plane and vertical "water upper-oil lower" in the northern wings,fault block and fault lithology are the major types of reservoir;In South,mainly controlled by lithology,the pure water-bearing zone doesn't develop,the scale and physical properties of the reservoir significant effects for oiliness,the lithology and fault lithology are the major types of reservoir.Using the theory of hydrocarbon accumulation,combinating with predecessors relatively research results about Putaohua reservoir accumulation,the study synthetically analyses the accumulation conditions of the subtle oil and gas reservoir,and summarizes favorable accumulation pattern.Putaohua oil reservoir in two wings of Aobaota structural belongs to accumulation model of“upper reservoirs and lower source rocks,oil vertical migration along the faults,and oil accumulation in fault-screened and sandstone wedge out traps",? the K2qn1 oil source rock in both depression and both wings of Aobaota structural provide adequate sources of oil and gas for Putaohua reservoir in the area;?Faults active in inversion period are the main oil-migrating faults,which provides vertical channels for primary migration of oil and gas;In the favorable induction of inherited palaeohigh,oil and gas migrate along the transport way composed of faults and sandbodies to the central anticline belt together,transportation systems can be divided into three kinds:the same trend faults zone-lithology,consequent faults-lithology and reverse faults-lithology;?Oil and gas are accumulated in the traps of fault-lithology,lithology,fault block and micro-structural trap which shaped by interaction cutting of fault and lithology or lithologic pinch out.Based on the spatial combination between fault and sand body,five kinds of favorable oil accumulation models fit to both wings.They are the model of oil-migrating fault in the downward direction and sandstone wedge out trap in the upward direction,the model of inversed fault screened in the upward direction and sandstone lap out in both sides,the model of oil accumulation in higher fault blocks and positive structure,the model of fault-lithology besides the same trend faults,the accumulation model of lithology in low amplitude nose-like structure.On the basis of analyzing accumulation characteristics and distribution of all kinds of model,with the research of structure,sedimentation and oil-water distribution,the division of favorable accumulation area and optimization for increasing reserves potential block are established,which provides theoretical guidance for next step exploration and development in two wings of A obaota structure.