The Study On High Resolution Sequence Stratigraphy And Remaining Oil Of The Sapu Reservoir In Dense Well Pattern Area Of Sazhong In Daqing Oilfield

Taking the SaPu reservoir in dense well pattern area of Sazhong in Daqing oilfield as the studied area and layer, under the guide of high resolution sequence stratigraphy theories and reservoir sedimentology, utilizing core and logging data, to systematically make division, layer unification and correlation of the high frequency isochronous sequences, the studied area and layer is divided into 1 long-term,5 mid-term and 58 short-term base level cycles, to set up the framework of the high resolution sequence stratigraphy. At the same time, according to the sand body division problem that the differences of the sand body on the near distance adjacent wells is obvious, even to be sudden varies, and that cutting-piling sand bodies are serious so that their divisibility is worst in vertically(the thickest sandstone layer is nearly 20m). Combining depositional setting of the reservoir, and utilizing formation cause analysis of the sand body and identification and combination of the logging microfacies, to systematically study the compound sand body in the dominant layer. To put forward divisional methods, that is "identification of the thick sand belt-statistics of number of the divisible well-standardization of the division location", in order to divide cutting-piling compound sand body, to adopt-'accordance to formation cause-reference to adjacent wells-delimitation'-divisional principle, to objectively and effectively resolve thick sand body division problem and to clear away barrier for layer unification and correlation of the whole studied area, and also to settle sound foundation for the establishment of the high resolution sequence stratigraphy framework and precise identification of the same formation cause single sand body.Under the control of stratigraphy framework of the high frequency and isochronal formation cause, sedimentary microfacies of the studied area are subdivided to 2 facies 3 subfacies 26 microfacies, instead of original four types which are channel sandstone,inner table sandstone,outer table sandstone and pitch out area, especially, according to quantitative characteristics of electric property,porosity and permeability,oiliness, to development condition of the reservoir of studied area, channel(meandering channel,distributary channel and under-water channel) are subdivided typeâ… ,-â…¡andâ…¢channel. On the basis of inner and outer table reservoir, to subdivide overflow and sheetflood sandstone, the former is subdiviede inner table silt-sand,outer table silt-sand,mudsilt-sand,siltmud-sand and interchannel mud. The latter is subdivided sheet main bodyâ… andâ…¡, sheet sandâ… andâ…¡. To establish floodplai,deltaic distributary plain and delta front 2 facies 3 subfaices 26 microfacies logging microfacies models. By means of fine identification and combination of each well and layer, short-term sequences plane sedimentary microfacies of the studied area and layers are drew:Not only clearly reveal formation cause,scale and distribution of sandbody in the short term sequence, but also come up with new standpoints under the condition of dense well pattern, that are "heterrogenetity of the main channel sand body and continuity of the distributary channele sand body", which are (1) abandoned channel sand body is identified in the flood plane and distributary plane; (2) original connected thick sand body, in fact, they are divisible or broadly divisible continuous banding channel sand body; (3) original mound discontinuous sand body, they actually are continuous belt or dentritic under water sand body. Via these new viewpoints, exhaustively reveal formation cause,scale,shape,density,within the same microfacies and between different microfacies energy unit variation and connect relation, at the same time, distinctly reflect channel upgrowth degree,swing direction and amplitude and the change of depositional environment and sub-enviornment.On the basis of vertical depositional evolution of the 58 short term sequences, to propose depositional system evolution patterns of the SaPu reservoir, that are(1) lake shoreline advance and retreat along the source, facies and subfacies boundaries approximately parallel to the lake shoreline; (2) depositional setting sometimes relatively stable, sometimes stride facies and subfacies or region variation; (3) the amplitude of main river system swing is wide, and energy variation is often; (4) lake wave function is unsteady, time of duration also is long or short. On the basis of plane sedimentary fine draw and quantitative statistic analysis of the each short term in the studied area, according to anatomy of dense well pattern in Sazhong, to propose the depositional pattern that is "large shallow delta subfacies subdivision under the control of the channel", including (1) the flood plane "especially big-size,serious cutting-piling,wide banding main channel sand body " depositional pattern; (2) the upper distributary plane "big-size,banding and interruption dividable channelâ… sand body" depositional pattern; (3) the lower distributary plane "mid-size,independent,banding and continuous channel sand body" pattern; (4) deltaic internal front near-shore "mid-small size,continuous belt under water channel-large area mud deposition" pattern; (5) deltaic internal front mid-shore "small size,continuous narrow belt under water channel-channel controlled sheet-sand" depositional pattern;(6) deltaic internal far-shore "narrow-small,continuous dry dentritic under water channel(or channel ends)-channel controlled sheet-sand" pattern; (7) deltaic external front "channel controlled fan-shaped sheet-sand" and (8) deltaic external front "wave controlled sheet-sand" pattern. The pattern further confirm the type and scope of river-deltaic depositional system of SaPu reservoir in the dense well pattern area of Sazhong. It is clear that reservoir development degree and distribution regularity of the SaPu oil layer. It provide reservoir sedimentary guarantee for reservoir space distribution pattern establishment of the whole Sazhong area, identification and forecast of the same formation cause, development adjust and remaining oil development, meanwhile, it is of extremely important guidance significance for reservoir predict of the rim or similar with it, for the remaining oil research.By means of fine reservoir study, to put forward under the condition of dense well pattern, in the high to highest water flooding stage, the dominant factors of the remaining oil of the SaPu reservoir are herogenety in the layer and on the plane. The main types of the remaining oil is narrow and small channel sand body that is uncontrolled in the original well network, abandoned channel blocking and injection-productiion system is inperfeccable so on. The two former are the important points of the revelation under the dense well pattern.414 narrow and small channel sand bodies are indentified in the 45 short term sequences (occupy the total short term sequences of 77.6%).71 abandoned channel sand bodies are indentified in the 13 continental short term sequences in the this study in the dense well pattern condition. Beside also to propose remaining oil development measures.