Study On Sand Bodies Distribution Of Shan1Section And He8Section Of Upper Paleozoic In The South Of Sulige Area

Upper Paleozoic of Ordos Basin are rich in natural gas resources, while Sulige gas field has been one of the largest natural gas-rich regions. Currently the main gas-bearing blocks are located in the Yikezhaomeng Wushenqi, Etuokeqi Etuokeqianqi of Inner Mongolia Autonomous Region and in Dingbian territory, Yulin region of Shaanxi Province. Region surface is mainly desert and marsh, with the ground altitude arranges from1250to1350meters. Sulige gas field is located in the south of Yimeng uplift, north of Yan’an-Gaoqiao, east of Tianhuan depression, and west of Iraq Shaanxi slope, belongs to the northwest part of Iraq Shaanxi slope in Ordos Basin in regional tectonic position. gas source rocks of Upper Paleozoic are the paralic coal rocks and mudstones from the lower part of Carboniferous-Permian. The delta plain (front) distributary channel sands, delta front estuarine sands, marine and coastal sands and tidal channel sands are favorible reservoirs, which developed between and above the gas source rocks. The floodplain lacustrine mudstones are the ideal regional seal of the Upper Paleozoic gas reservoir in the upper part of Permian.The formation of Sulige gas field is mainly controlled by the distribution of river and delta sands of the Upper Paleozoic and regional tectonic setting of the basin. Sulige gas developed large sandstone lithologic traps. The main gas reservoir is the8th Member of Lower Xiashihezi formation and the1st member of Shanxi formation in Permian, the rock types are mainly coarse-grained quartz sandstones in the delta plain distributary channel microfacies sediments. Although we have achieved some results on keleton sand bodies distribution of Shan1section and He8section of Upper Paleozoic in the south of Sulige area, but there are still some problems, including fine stratigraphic division is not enough, and the resulting of sublayer deposition microfacies division, skeletal sand body distribution, etc., affect the screening of the block-rich region. In recent years, areas of exploration and development work had been carried out of Sulige area, therefore, we also have to face a more complex object, and integrated previous research results, the main problems that currently exist in the south of Sulige area are:1, stratigraphic division is not enough fine,layer characteristics are less obvious signs, skeletal sand body distribution law is not clear;2, sedimentary facies and sedimentary system and not systematic. For the sedimentary facies of Shan1section and He8section, there are two main points, one view is that it belongs braided river delta deposition, another view is meandering river delta deposit. But in the end zone is the kind of sedimentary facies type, or both types of sedimentary facies exist, is still unknown;3, the distribution law macroeconomic development framework sand, microscopic characteristics and influencing factors. The overall thickness of Shan1section and He8section changes, the distribution of sand bodies in the lateral skeleton is more complex, extended distance is less clear, large differences in the longitudinal direction lithology, degree of understanding of the relationship between sand bodies are not high. Therefore, it is necessary to figure out the formation, sedimentary facies, distribution law macroeconomic development framework sand, microscopic characteristics and controlling factors such as research of of Shan1section and He8section of Sulige area, oil and gas exploration for the next deployment, the author reserves of oil and gas reserve provide a more adequate basis.Based on geological data of hundreds of oil and gas wells, a systematic comparative study of stratigraphic division of Carboniferous and Permian are carried out with the international popular division plan. In this paper the lithostratigraphic division plan are used. Benxi Formation, Taiyuan Formation of Permian, Shanxi, Shihezi Formation and Shiqianfeng Formation were developed from bottom to top in Upper Paleozoic strata in Sulige gas. The total thickness of sedimentary rocks are about700m, and the main gas-bearing section is located in the1st member of Shanxi formation to the8th member of Xiashihezi formation, both of which were developed continually with the thickness of about90-100m and burial depth of about3200m-3500m. The thin layer division are based on sedimentary cycles and three thin layers are divided in the1st member of Shanxi formation and four thin layers are divided in the8th member of Xiashihezi formation.In the extensive collection, digestion and application of the Changqing Oilfield, and other universities and research units of exploration over the years based on the results, drilling cores through microscopic observation and study of rock thin, the study of layers of sedimentary environments and sedimentary microfacies be the focus of analysis types and distribution; combine a variety of analytical tests and other information based on the study of sedimentary facies and reservoir, air conditions and favorable exploration drilling results preferred zone. After a year of research has made major progress and results are as follows:1, through a detailed study of the study area, more than140exploration wells and development wells, the use of large amounts of log data and combine identification layer,we have Carried out a detailed classification and correlation of Shan1section and He8section.The thin layer division are based on sedimentary cycles and three thin layers are divided in the1st member of Shanxi formation and four thin layers are divided in the8th member of Xiashihezi formation. And compilation of stratigraphic correlation diagram, to ascertain the distribution of strata in the study area characterized by obvious signs layer, more stable stratigraphic thickness.2,the sand of Shan1section and He8section is near the north-south trending, from north to south thinner. Showed a contiguous channel sand distribution from Shan1section to He8section the sand southward advanced overall. The skeletal sand of Shan1section have been divided into6sets and the skeletal sand of He8section have been divided into4sets.And the skeletal sand of Shan1section presented banded distribution,and the skeletal sand of He8section presented braided distribution; thickness of the sand bodies of Shan1section are thin than the sand bodies of He8section.3, compared to non-skeletal sand and small layer overriding sand,skeleton sand have a feature of higher quartz content and more coarse-grained. Skeleton sand bodies have been divided into four kinds, there are batture overriding sedimentary,batture and river course overriding sedimentary, river course overriding sedimentary,single batture sedimentary. Non-skeletal sand bodies have been divided into three kinds, there are single river sedimentary, single batture sedimentary,combined river sedimentary.4, Through the study found that this work area belonged to the low porosity and low permeability, high porosity higher plan well and permeability distribution of basic values correspond well, mainly distribute in the eastern part of the study area. The porosity and permeability of Shan1section presented banded distribution, the porosity and permeability of He8section presented braided distribution; the porosity and permeability of Shan1section are better than He8section.5, Provenance,ancient landforms,sedimentary facies and hydrodynamic impact on the skeleton and reservoir properties of sand cloth exhibition in varying degrees.