| The Ou 31 well block is located in the eastern depression, southeast of the central uplift belt of liaohe basin, the exploitation series of the stratus are the above of Sha3 and the middle of Sha3. The fractures in the study area are well-developed, and the tectonic framework is alternate with concave and convex, and it can divided into four convexes, six concaves and 10 second level units. With the deepening of the development, the increasingly prominent contradiction stand out between the layers. Frequently appears the phenomenon that the water injection gets no oil and the oil extraction with no water injection, and these phenomenons take abnormal big challenges to the oil field exploration and production. And the main problems are about understanding the unclear phased sand body size and the no clear advantage of facies plane distribution rules. Therefore, on the basis of early fine stratigraphic correlation, the research of sedimentary microfacies of the above of Sha3 in Ou 31 well block, undoubtedly which will provide important reference basis for the later adjustment of development program.The paper makes full use of the present study fields of the existing seismic and logging data, through seismic attribute analysis, the study find out the advantage distributions of sand mudstone facies and provide evidences for the provenance analysis; Through the log facies analysis, the paper makes the microfacies identification chart on the basis of log facies, and establishes a microfacies identification standard. Then on this basis, the paper using the idea of point-line-face research. Finally carry out the scope of all kinds of sedimentary microfacies spatial distribution.Before conducting the sedimentary microfacies in the study area, it is an important basic work to demarcate the fine stratigraphic correlation framework of the calibration, through the stratigraphic framework constraints in the earlier stage the paper determined the top and bottom boundaries, and then uses the well-to-seismic calibration method to complete the time-depth conversion, finally, implement the macroscopic distribution range in the bottom of Sha3.From the bottom of Sha3 the layers are the Ⅳ oil formation and the III oil formation. On the seismic section, it is also available to complete the fine tracking and comparison of the layers. But the local contrast results are a bit poor, the study need to take advantages of dense well pattern, and basing on the seismic trace horizon background, the study combining with the recognition and pick up of marker bed in the log profile, can complete stratigraphic isochronous correlation and fine set, and establishing isochronous stratigraphic correlation of complete lattice to build a research foundation for the subsequent detailed study of sedimentary microfacies.The research shows, coal seam in the target intervals and the mudstone section in the bottom of the oil formation, could be served as good marker beds of the whole district. With sequence stratigraphy theory, the thesis achieves the partition and comparison of stratigraphic units in the whole district. And it shows, the III and IV oil lines in OU 31 district in the lower third sub-member of the Shahejie Formation can be divided into 5 stratigraphic units top to bottom, including 2 sandstone groups in ES3 III oils line:S331 and S332; 3 sandstones groups in ES3 IV oils line:S341、S342、S343. By dividing and comparing stratigraphic sequence, the thesis makes use of drilling datas of 80 wells combined with previous research results, and it shows the studied provenance supply direction lies in the central bulge belt in the northwest, orientates NW direction. The sandy ground analysis results of many wells further supports reasonability of the inference of the above provenance direction. The further results shows, there mainly develops delta front subfacies in the third super-member of the Shahejie Formation, Among them the connectivity of the IV oil fan body is better than the III oil group, and bigger in a single fan body scale. The fan bodies scale in different oil group of subdivision stratigraphic unit are apparently controlled by the rise and fall of the lake level, with smaller fan body sacle in the rise, and the opposite in the fall. In addition, the quantity of the provenance supply is also an important governing factor, while the rise and fall of tectonic movement is relatively unconspicuous. Except the above factors, the studied zone is also affected by the underwater vulcanian eruption in the earlier stage, because the low uplift caused by the eruption decreases accommodation, and it is natural barrier to the accumulation of the fan delta front sand body, thus limiting the underwater distribution scope of the fan delta front. The comprehensive analysis results shows, there mainly develops fan dalta-lacustrine facies deposition in the third super-member of the Shahejie Formation. With a gradual rise in the lake level from the bottom up, there mainly develops microfacies such as distributary channel, estuary dam, overbank sand, sheet sand, lacustrine-marsh, bendway bog and so on. The third super-member of the Shahejie Formation can be subdivided into 5 stratigraphic units, and there are some relevance and succession on the sedimentary characteristics in each period. In the S343 depositional stage, the water is shallow, with relatively development in the riverway sand and estuary dam, relatively developed in shore-shallow lacustrine sand, and there is a trend of partly distributing together. Among them the sand body in the estuary dam is concentrated distributed in the fan delta front, close to water; while the sand body in the beach-bar scattered as strip-shaped along the lake shoreline; In the S343-S342 depositional stage, the base level begins to rise gradually, the deposition water is deepening slowly, provenance regresses to the land, with decrease in the size of fan delta front subfacies, and it shows a trend of retrogradation in the sedimentary section; In the S342-S341 depositional stage, the base level decline gradually, and it leads a constant decrease in the accommodation, with a smallest lake area among all the depositional stages in the III, Ⅳ oil group of the third super-member of the Shahejie Formation; In the S341-S332 depositional stage, there is a rise in the base level and increase in the lake area, with a dramatical decrease in the depositional size of fan delta front subfacies, so the estuary dam is relatively lack of development; In the S332-S331 depositional stage, there is a constant rise in the base level and its accommodation is further enlarged, and the he lake area reaches the biggest among the depositional stage. After synthesizing the above analysis results, the thesis reaches a conclusion that the lengthways stratum accumulation type of the sandstone stratigraphic unit in the study zone varies regularly, that is regression-progradation-regression-progradation, but it shows retrogradation as a whole. |
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