| with those mature oilfields in eastern China being unceasingly explored and developed for years, the exploration and development process becomes more and more difficult, the current situation that high-quality resources can never be replaced, making exploration targets transfer to those concealed oil and gas like complex lithology oil reservoirs and unconventional oil resources, etc. Seeing from the latest resource assessment, Fuyu reservoir and Yangda chengzi reservoir in the northern Songliao Basin are quite rich in lithologic reservoir, as proved geological reserves accumulate to 6.34* 108t, Fuyu reservoir, which is located to the east of Daqing Placanticline, whose proved geological reserves add up to 5.94x108t, accounting for more than 95%. So far, several oilfields like Toutai, Zhaozhou, Songfangtun, Yushulin, Chaoyanggou, Yongle oilfield, the proved reserves of each reached 2× 107t respectively. It is observed that Fuyu reservoir, which is to the east of Daqing Placanticline and in the northern Songliao Basin, will become the coming main battlefield of lithologic reservoir in exploration and development.Fuyu oil layer in the Songliao Basin is one of the main target layer of oil and gas in Daqing Oilfield, rich channel sand body was deposited in the fluvial and delta system, but this type of sand body is quite thin on vertical and unstable on lateral, and the distribution of the sand body is hard to predict, all these problems have constrained the exploration and development in this area. In order to solve this problem, the thesis is aim at thin layer sand body which is developed in the fluvial and delta system in Fuyu oil layer, by using dense drilling well data, high precision 3D seismic data, and multiple slim layer correlation techniques, high-resolution sequence stratigraphic framework has been established in the research area. On the basis of high-resolution sequence stratigraphic framework, integrating multiple pivotal techniques like fine sedimentary microfacies analysis, seismic multi-property analysis, strata slice, frequency division processing and reservoir modeling to study the distribution of thin layer sand body in the fluvial and delta system as well as provide guidance for late exploration and development in the oilfield. The following achievement was obtained by the research:1. By summarizing several proper high-resolution sequence stratigraphic division and correlation techniques to study the fluvial delta system, This thesis high resolution sequence stratigraphic stratum framework is able to launch in Fuyu reservoir to the east of Daqing Placanticline.The results prove that the second set of oil shale on the bottom of Qingl member comes from the maximum flooding surface, which is considered as the first-level key bed of correlation. The contact relationship between the top boundary of Fuyu layer and black oil shale at the bottom of Qingl member is parallel conformity; there is a regional unconformity exposed as a sequence boundary at the interface of Fu I and Fu II formation, and another partly exposed unconformity which is a sequence boundary at the bottom of Fu II and FuIII formation. The low level boundaries of base-level cycles are sequence boundary symbols of partly exposed unconformity. According to the pattern of short-term base-level cycle, there are 2 classes and 6 subclasses are divided:low capacity spatial and asymmetric form(Al, A2), high capacity spatial and asymmetric form(A3), rising half-cycle based and not completely symmetrical short-term cycle sequence(Cl), completely to nearly completely symmetrical short-term cycle sequence(C2), descending half-cycle based and not completely symmetrical short-term cycle sequence(C3). The thesis summarized several proper high-resolution sequence stratigraphic division and correlation techniques to study the fluvial delta system of Fuyu reservoir, including following fluvial sub-layer correlation techniques:constraint and correlation of key boundary, short-term base level cycle correlation, channel cutting and filling correlation, sand body interlayer correlation, fluid property comparison, channel stage correlation when processing elevation comparison, isochronous correlation between channel and flood fan, strata thickness restricted correlation. Based on above-mentioned techniques, high-resolution sequence stratigraphic framework is built on a short-term base-level cycle, thus laying a foundation for the study of sedimentary microfacies in the target area.2. By combining the color of core, sedimentary structure, grain size, core content and special mineral, the detailed sedimentary microfacies are able to study by core observation and description.The study shows that the sediment in the research area mainly consists of fine sandstone, siltstone, mudstone. According to the strength of hydrodynamic condition and the different transporting ways of sediments, the lithofacies in Fuyu oil reservoir is divided into 4 types and subdivided into 24 subclass lithofacies, on the basis of sedimentary cycle features on the vertical,3 types of lithofacies assemblage are concluded. Fuyu oil reservoir mainly developed 3 types of sedimentary facies, which are meandering fluvial facies, shallow delta, shallow lake, in the further study,6 subfacies and 13 microfacies are divided. On the basis of lithofacies assemblage law, sedimentary features of different microfacies are summarized and microfacies plates of logging-core which correspond to 2 facies,3 subfacies and 13 microfacies are established.3. Within the high-resolution sequence stratigraphic framework, the spatial distribution of sedimentary facies of Fuyu oil layer in the study area is analyzed based on the researches on regional provenance, geometrical parameter of different types of sandbody and the palaeogeomorphology. Then on this basis, the depositional models of Fuyu oil layer to the east of Daqing Placanticline at different sedimentary periods are proposed.The results show that the research area is influenced by three water systems, namely Nahe-Yi’an water system, Baiquan-Qinggang water system, Huaide-Chuangchun water system; the geometrical parameter of different sand body shows:the depth of meandering river channel ranges from 2m to 12.5m, the scale of meandering river channel ranges from 300m to 1450m; the depth of distributary channel ranges from 2m to 9.6m, the scale of distributary channel ranges from 200m to 1150m, the depth of underwater distributary channel ranges from 2m to 6.2m, the scale of underwater distributary channel ranges from 200m to 650m. Restricted by the sequence stratigraphic root mean-square attributes of the fourth level, based on the single well and well-tie division and correlation of sedimentary microfacies, using single factor mapping method to compile sedimentary microfacies plane distributive maps of short-term base level cycle unit in the research area, thus establishing three sedimentary models during the critical period in the Fuyu reservoir to the east of Daqing Placanticline.4. The genetic type, sedimentary characteristic and architecture of different type of channel sandbodies in Fuyu oil layer within the study area are studied in detail. By using the key technologies such as seismic multi-attributes analysis, reservoir modeling etc, the spatial distribution of different sandbodies is analyzed.The research shows meandering sand body has coarser granularity, larger bedding and more internal sedimentary cycles compared with sand body developed in distributary channel and underwater distributary channel. The newly formed conclusion in different sand body structure characteristics indicates that the existence of fourth and third interlayer is the main reason for oil-bearing heterogeneity of single sand body in vertical direction. The research also identified three types of interlayers:muddy, calcareous and conglomeratic silty intercalation. Guided by pivotal exploratory and developmental blocks, the thesis extracted different attributes and built geological model to depict planar and spatial distribution.5. With the variation of base level, the scale and physical property of different types of sandbodies are changed regularly. Depending on the distribution of sandbodies, physical property and tentonic characteristics, distributed scope of favorable reservoir is predicted, which will be benefit for the exploration and devopment of the lithologic reservoir.The research shows, during Q3-SSC7-Q4-SSC3 period, sand body developed to its largest scale and the physical property is relatively the best. Taking the fourth lever sequence as a prediction unit to set appraisal standard according to regional characters, for channel:cumulative sand body depth is greater than 7.5m, porosity is greater than 14%, permeability is greater than 1×10-3um2, which is type I; cumulative sand body depth ranges from 5m to 7.5m, porosity is greater than 12%, permeability is greater than 0.5 × 10-3um2, which is type II, thus predicted the favorable sand body area in the reservoir at different stages. |
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