Reservoir Characteristics And Classified Evaluation Research Of Yanchang Chang2 Formation In Northwest Area Of Zhiluo Oilfield

Zhiluo Oilfield located in the structural unit in middle of Northern Shaanxi Slope, Ordos Basin. The early exploration and development indicated the poor physical property of the reservoir of Yanchang Formation in this area and the distribution of oil and gas controlled by the factors of sedimentary facies, diagenesis, reservoir properties and so on. In response to this situation, the thesis is guided by sedimentary petrology, reservoir geology, petroleum geology, geophysical well logging and other related theory, combined with Multi-statistical analysis, relied on the current advanced experimental testing methods, used the information of geological outcrops, drilling, logging, adopted the macroscopic and microscopic research methods, we conducted a detailed study on the reservoir characteristics and classified evaluation of Yanchang Chang2 formation in Zhiluo Oilfield.Comprehensive studies suggested that regional tectonic is relatively flat, there are some low nose-shaped bulge, the formation thickness are more steady and changed little. Provenance is mainly from the North East region, each period the river have NE-SW trending features, Chang2 developed delta front sediments, the sand of Chang2 developed well. Chang21, Chang22 sand developed very well. Chang 23 in the study are mainly argillaceous distributary Bay. Chang2 reservoir sandstones are mainly lithic feldspathic sandstone and feldspathic sandstone, the detrital compositions are mainly of quartz, feldspar, debris, mica and so on, the content of interstitial material component is relatively high, most of cements are chlorite film. Sandstone compositional maturity is relatively low, structure maturity reached medium, sorting is better, mainly for the round subangular. The sandstone clastic particles are mainly point-line contact, cementation type is major of pore cementation. Reservoirs mostly develop residual intergranular pore, corrosion intergranular pore and intragranular dissolved pore. The average porosity of Chang2 is 12.57%, the average permeability of Chang2 is 2.50×10-3μm2. This time we applied Q factor analysis and cluster analysis of multivariate statistical method for reservoir classification and evaluation, compared with the previous qualitative method of reservoir evaluation, the quantitative reservoir evaluation method based on objective data, effectively avoid the interference of subjective factors, each evaluation factor attached to weight coefficient, comprehensive factor score formula(the reservoir evaluation model) is given at the same time, and has a good applicability in the study area. The reservoir is divided into three categories: Ⅰ(good reservoir), Ⅱ(medium reservoir), Ⅲ( invalid reservoir). From the reservoir classification of Chang2 we can see, the Ⅰ、Ⅲ reservoirs developed less in the study area and only developed in some individual regions, the Ⅱ reservoirs distributed broadly in the area.