Sandstone Distribution Pattern And The Prediction And Evaluation Of Subtle Oil Reservoirs In Meandering Channel Of Slope Belts

The Ordos basin is a polycyclic cratonic basin with stable settlement and composite depression, which has become an important energy base in China because of its rich oil & gas resources. Ningtiaoliang-qiaogouwang areas is located in Jingbian County, Shanxi Province, which is belong to middle-north of the slope of Shanbei, Ordos basin. Because the study area has a very special geological conditions of oil and gas, the exploration and development of oil and gas resources in the study area is very significant to the development of Changqing Oilfield.The main layer of this dissertation is Jurassic Yan'an Formation, including yan-8 oil reservior and yan-9 oil reservior. On the basis of a large number of well logging, mud logging and core analysis data, we have divided Yan-8 oil reservior into yan-81, yan-82, yan-83, and divided yan-9 oil reservior into yan-91, yan-92+3 by the principle of cycle comparison and hierarchical control.Based on the accurate stratigraphic correlation, the yan-8 and yan-9 oil reservior of the study area is meandering river which can be divided into channel microfacies, flood plain microfacies and crevasse channel microfacies by studying the regional data, the sedimentary cycle and the bore log feature. There are multi channels in Ningtiaoliang-Qiaogouwan area, and the main distribution direction is northeast-southwest. The thickness of banded Channel sandstone is 4m-20m, and the direction is the same as that of the channels. While the continuity of sandstone is good in the vertical and relatively poor in horizon. The porosity of the channel sandstone is good, and its permeability is high, too. Therefore, channel deposits are the main reservoir.The results of analysis material show that the yan-8 and yan-9 oil reservoir are mainly structural hydrocarbon reservoir and lithologic-structural hydrocarbon reservoir. Based on the detailed study of the distribution of sand bodies, combined with the structure, well logging, log interpretation, well test and production information, finally, there are many prospective targets in addition to an area outside the proven have been found:There are 6Ⅰclass targets with 67.346km2 of oil area and 2048×104t of geologic reserve,7Ⅱclass targets with 106km2 of oil area and 4290×104t of geologic reserve and 21Ⅲclass targets with 296.52km2 of oil area and 9614×104t of geologic reserve. These optimization of exploration targets have provided important geologic basis for further exploration and development and deployment.