Research On Reservoir Characteristics Of The Chang2₁Formation In The Second District Of Zhangqu, Jingan Oilfield

The second district of Zhangqu area is one of the important oil producing area in Jingan oilfield of Ordos Basin,and chang21of Yanchang formation, Triassic is the main oil-bearing formation in the field. After flooding development has made over a period of more than ten years, the original geological understandings of the region have been unable to meet the needs of the present stage of development. Therefore, it is necessary to have a study on the reservoir characteristics and oil controlling factors of chang21of the district comprehensive and thorough, which will supply geological basis for later and further development and deployment and adjustment strategy.Based on the basis theoretical knowledge of sequence stratigraphy, sedimentology, reservoir geology, according the tectonic and sedimentary characteristics of Chang21oil formation in the second district of Zhangqu area, using a variety of analytical methods, the reservoir characteristics are studied deeply, the paper summed up the distribution rules of high quality reservoir, made analysis of oil control factors, pointed out the direction for the further development and deployment.Under the big background of West monoclinic dumping in Ordos Basin, The Chang21reservoir has5-7nose structures. Delta plain sedimentary system develops mainly the distributary channel, interchannel, mouth bar and natural levee microfacies; Rock type is mainly feldspathic sandstone; Pore type are mainly intergranular pore and feldspar dissolved hole, reservoir physical property is better in different layers relatively, as in low porosity, low and extra low permeability reservoir.Parameters related to Chang21oil-bearing reservoir selected and made clustering analysis, the reservoir can be divided into three categories, main hydrocarbon accumulation in class Ⅰ, class Ⅱ reservoirs; Because of thin sand body, poor physical property, less oil and gas charged, class Ⅲ reservoir is difficult to form large-scale oil and gas accumulation. Class Ⅰ and class Ⅱ is mainly occupied chang213-1, chang213-2reservoir in study area, as the main producing layer, they have developed distributary channel microfacies, sand bodies, with better properties. Meanwhile, class Ⅲ occupied chang211and chang212reservoir, it has thin sand body, poor physical property. Combining all test data and analysis result, got that oil bearing is mainly controlled by the structure, deposition, diagenesis. With reservoir characteristics and oil and gas controlling factors in the area, the further rolling extension direction have been made, and provides a reliable basis for the next step exploration and development.