The Reservoir Evaluation Of The Chang-2 Member Of The Yanchang Formation In Yujiaping-wangjiawan Area Of Zichang Oilfield

Yujiaping-Wangjiawan area of Zichang oilfield is located in Zichang county of shanxi province. Its tectonic location is the Shanbei slope of the east Ordos Basin. The Chang-2 member of the Yanchang formation is the main producing oil layer. According to the principles of cycle correlation and graded control, subtle indications of natural gamma log curve the Chang-2 member of the Yanchang formation is subdivided into chang-21-1, chang-21-2, chang-21-3 and chang-22 types based on the age equivalence. Based on the stratigraphic correlation, the tectonic-stratigraphic framework of whole area is established. The general structural framework of Chang-21 of Wangjiawan area is a west dipping monocline, and there exists some nose arch and some minor peaks.According to regional deposition backgrounds, plane sand-body distribution, the lithology, electrical property, and log curve, it shows that the facies of the Chang-2 reservoir belongs to the delta plain sedimentary system. Based on the maps of flat sedimentary microfacies distribution and sedimentary facies, the types and characteristics of subfacies are analyzed further for sub-oil-bearing beds of Chang-2 reservoir, chang-21-1, chang-21-2, chang-21-3 and chang-22.Based on all the research of flakes, core and sample tests it shows that the reservoir sandstone of Chang-2 reservoir in Wangjiawan mainly is feldspar sandstone, besides bit lithic feldspar sandstone. And its pore types is mainly the intergranular pore, then the dissolution pore. Chang-2 reservoir in the area is of the poor reservoir properties with low porosity and low or extra-low permeability. By the analysis of characteristics lithology, physical, seepage, Chang-2 reservoir is evaluated that primary is type II and III, secondly for I and IV.The logging interpretation mathematical model is established for reservoir parameters. And based on that, the secondary digital processing is conducted on logging data, and the reservoir parameters of non-coring wells are quantitatively determined. The reservoir parameters determination provides the data for reservoir geological modeling.According to the analysis test data of coring well, with the combination of practical production, Chang-2 reservoir in the area is divided into 4 flow units, A, B, C, and D. Among these, flow unit C is a reservoir with poor quantity, however it is the main flow unit type.