| Gaoyou sag in Subei basin is aterrestrial rift-subsidence lacustrine basin formed form Late Cretaceous Period to Paleocene. Majiazui districts, with the consistent evolution characteristics of the whole depression, lays on the west part of Gaoyou sag, but has a much more complicated tectonic evolution process caused by the two bid controlling faults. With the development of sequence stratigraphy、the constant improving interpretation technology and processing technology of three-dimesional seismic. Scrolling development work more elaboration. In order to further deepen regional awareness、intensify rolling development improve the reserves producing degree, on the basis of make full use of existing information in hand, Including well logging, core and cuttings、 sheets、outcrop etc, in combination with the practical situation of production, researching the basic characteristics of reservoir. Exploratory recognized the sedimentary characteristics、the types of pore throat, reservoir parameter distribution, reservoir heterogeneity, etc. of Dainan group various sand section in Majiazui area. The final analysis of log interpretation results of a preliminary classification of reservoir evaluation, predict favorable area, providing a basis for further geological and oil and gas is development and exploration.In the study area, Dainan group of reservoir sand body for the northern provenance of sand bodies of fan delta front、turbidite sand bodies and the southern provenance sedimentary underwater alluvial fan sand bodies. Sand body horizontal extension not exceeding 300 m, the thickness of the thinner, and the area of the single sand body is very small. The sand body in the study area has the obvious features of "a thin three low", namely single sand body is thin, low percentage of sandstone, sand drilling rate, sand body connectivity rate.During the Dainan formation sedimentary periods, developed nearshore subaqueous fan、fan delta and lacustrine depositional system of three major depositional system in the study area;Among them, nearshore subaqueous fan is mainly developed in Dainan group one sedimentary period, fan delta mainly developed in Dainan group two sedimentary period. The nearshore subaqueous fan delta sand body, which in Shallow water, the under the action of external force along the slope sliding and handling, The formation of turbidite sand bodies. More for lenticular distribution, development in Dainan group two sedimentary period. Underwater distributary channel has the characteristics of migration swing;Thick sand body development zone is located in the common influence on both sides of the source area. The underwater distributary channel is the main microfacies types forming favorable reservoir in the fan delta front.Sediments in the study area mostly in lithic feldspar fine sandstone, visible fine sandstone;Detrital component is given priority to with quartz, Debris and feldspar secondly;Among them, debris is given priority to with volcanic rock and carbonate rock, mudstone, quartzite, siliceous rocks and granite, schist. The sand sandstone structure in the study area is Mainly for fine silt. The major diameter range distribution in range of 0.004 mm to 0.20 mm. The major sandstone particles roundness is subangular, secondly, for garden-subangular, eparation of medium deviation, give priority to with point, line contact relationship, cementation type is given priority to with pore type cementation, a small amount of basal-pore type cementation;Rock structure is generally characterized by compositional maturity and structural maturity general characteristics.Dainan group in the study area reservoir rock reservoir diagenesis phenomenon is very complicated, compaction, cementation, metasomatism and dissolution are very obvious. Among them, compaction and cementation make primary pore reservoir damage, as the destructive diagenesis;And dissolution make such as feldspar and other soluble clastic and carbonate cement dissolution, resulting in a large number of secondary dissolution pores, for constructive diagenesis.Dainan group buried depth in the study area is less than 3500 m, according to the reservoir particles contact relationship, the types of pore structure evolution and authigenic clay mineral evolution were studied, Using "clastic diagenetic stage division*(SY-T5477-2003,China national petroleum corporation (2003)) indicators of diagenetic stage division and determine, mostly major diagenetic stage mainly for rock phase (A、B), into rock phase (A、B).Dainan group reservoir rocks in the study area development primary pore and secondary pore, the primary pore is mainly the residual intergranular pore, secondary pore include intergranular dissolved pore, intragranular dissolved pore and mould pore and micro cracks, reservoir performance characteristics for the medium and low porosity, low permeability, physical plane features are:overall in the northeast and southeast direction porosity distribution, porosity and permeability distribution mainly in the northeast and southeast direction, trends are similar. Permeability core sample in the studied area of correlation analysis, Dainan group section of every sand formation permeability and porosity show significant positive correlation, that the change of permeability is mainly controlled by porosity development degree, the better porosity, permeability, the better, showing the characteristics of the pore type reservoir. According to the porosity, permeability map can be seen in the study area Dainan a set of the average porosity of sandstone reservoir, the average permeability than two segments of high Dainan group, showed a trend of obvious good reservoir physical property, reservoir property better distribution area is basically in conformity with the sand thickness high value zone. Dainan group in the study area the sand layer section of plane, interlayer and sand body in all with strong heterogeneity.Based on reservoir rock types, sedimentary facies, diagenesis, diagenetic facies, physical distribution, sand thickness, lithology, debris size, pore characteristics of the study area Dainan group two section conducted a comprehensive evaluation of the reservoir, the reservoir study area reservoir layer is divided into I class、Ⅱ class、Ⅲclass and Ⅳ class reservoirs. I class and II class reservoirs are mainly developed in the main fan delta underwater distributary channel sand bodies, porosity and permeability conditions were better, Ⅲ class reservoir developed in nearshore subaqueous fan fan side, front fan delta, porosity and permeability conditions are poor, IVclass reservoir development in the delta front mainly, hore and shallow lake, reservoir as invalid.Based on the study of each section of the reservoir characteristics in the study area, combining static and dynamic data of that area, Dainan group in the Majiazui area to predict the advantageous area of the sand layer. Among them, E2d12section forecasts the favorable six blocks, are mainly distributed in northeast in the study area M31 block and southeast of M33 block; E2d11 section predicted favorable six blocks, are mainly distributed in northeast M31 block, in the study area in the southeastern city of M33 block and southwest M35 block; E2d25 section predicted favorable seven blocks, has a wide distribution range, central and eastern no favorable blocks in the study area; E2d24 section predicted favorable seven blocks, similar to the early stage of the distribution area; E2d23 section predicted four blocks, are mainly distributed in the west of the study area and northeast; E2d22 section prediction for three blocks, mainly distributed in the study area in the northeast and the south;E2d21section prediction for two blocks, mainly distributed in southern M33 blocks in the study area.On this basis, combined with the actual test oil and oil production data, predict favorable exploration blocks, can be used as a favorable target for further exploration of the area. |
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