Study On Characteristics Of Sedimentary Facies And Reservoir At Jurassic Xishanyao Formation Of Mid Block-3 In Junggar Basin

Located adjacent to Shihezi City, Xinjiang, with its geographical structure attached to west part of Changji depression, Mid Block-3 in Junggar Basin is a new block in an old Oil Basin. Tests at strata of Xishanyao Formation of Well Yong 1 show oil output is72.07m³/d and gas 10562m³/d, which indicates great potential of exploration at the block.Since the exploration and development of Mid Block-3 remains its early stage, only 6 of the 9 wells reach the Xishanyao Formation confined to area of Well Yong 1. Thus, the study mainly concerns Characteristics of Sedimentary Facies and Reservoir of Well Yong 1 and involves some analysis of other unknown parts.The definition of Sedimentary Facies by Mr. JiangZaixing, etc. was adopted in this papers that Sedimentary Facies is supposed to contain features of Structure, Climate, Nature and Geography as well as physical and chemical characteristics of sediment media. Based on the results of renowned experts, a large number of materials of structures of the block and evolution of sediments were researched, and especially, with the research on petrology, the trend draft of Grain Size was designed as well. Further research was made on the evolution process of palaeohigh at Che-Mo, which is believed to directly control the sediment source of the block and influence the sediment environment and furthermore the diagenesis of sediment period, pore evolution of the reservoir and accumulation.The Point-Line-Face approach, i.e. from the analysis of single well to compare of a well tie and finally to the macro study the Characteristics of Sedimentary Facies and Reservoir, was employed when the research on Sedimentary Facies was made. When the analysis starts with the single well, materials of well logging and core were carefully and comprehensively applied. First, on the section of core and logging, characteristics of Sediment, facies sequence sediment, high frequency sequence cycle were studied with great care so as to build rock-electricity pattern and then on the section of logging. The results show lacustrine facies and braid delta facies were developed in the formation, respectively including lake shore, lake swamp, shallow lake subfacies and braided delta-front subfacies, and subaqueous distributary channel of the delta-front subfacies is thought to be the best facies belt to develop reservoir sand body.During the analysis of mentioned facise, High Resolution Sequence Stratigraphy was taken into consideration to basically build the equitime sediment frame of the formation. From the bottom, four Fourth-order sequence (middle time) sediment cycles, namely, MSC1,MSC2,MSC3 and MSC4, the structure and climate change of the latter two are most obvious. And in this frame, the complete study on sedimentary facise and reservoir's macro distribution characteristics was made.Then, analysis was done on thin sections and physical property and also on the influence of rock formation on the further reservoir characteristics, meanwhile made was the exploration of association of the cause of formation of secondary pore, distribution features with reservoir physical property in order to illustrate the micro characteristics of reservoirs. The results indicate primary pores dominate in the reservoir pores, and however the secondary ones are critical too for they account for 30% of the total pores. And intergranular dissolved expanded pores take the majority among the pores.The practical exploration and development of the field, as well as the result of the oil and gas tests were studied when classifying the reservoir into three ranks and four categories, i.e. I, II₁, II₂ and III. And, finally, research was made backward to the sections of the loggings, e.g. the analysis of response properties of various productive reservoirs in well loggings and the analysis of corresponding relation between productive reservoirs and Sedimentary facies and high frequency sequence cycle. The results show the most productive reservoir is Yong 1 * II₁.Eventually, evaluation and prediction of the productive development belt were made and the Well Yong 1 ,as well as Well Yong 3 of Sand Bed 2 is supposed to be the best distribution area of productive reservoir.In addition, in the papers, three suspending problems due to disputes and ambiguous illustration were explained. First, at the lower part of the Xishanyao Formation, as coal measures of hydrocarbon source rock, the isochroneity of classification of sequence; according to the analysis of the papers, interfaces of the coal measures can be used as the equitime interfaces of the four sequences. Second, at the upper part of the Xishanyao Formation, the formation mode of thick mudstone as cover rock; this is well elaborated by quoting mode enlarged lacustrine. Finally, the interface between Sand Bed 2 and Sand Bed 3; in the papers, it was posed that flooding surface of MSC3 can be taken as the interfaces.