Study On Control Elements Of Reservoir Of Chang9 Layer Of Yanchang Formation In Hongjingzi-Luopangyuan Area,Ordos Basin

Intensive research has been made on provenance direction, sedimentary system types, sandbody distribution, reservoir characteristics and hydrocarbon source and others by previous study with certain achievements. However, attention on reservoir characteristic, accumulation mechanism and enrichment regularity was limited, especially on differentiation of reservoir types, accumulation conditions of Chang9 oil set in Hongjingzi-Luopangyuan region. which caused the restriction on highly efficient development. The thorough and systematic studies on the facies and high resolution sequence stratigraphy of Chang9 oil set, including the classification and correlation and sandbody distribution, is of great importance and practical significance for this oil set prospect and development effectiveness. In this paper, the theory of structural geology, sedimentary petrology, sequence stratigraphy and petroleum geology are taken as guidance, with cast thin section, scanning electron microscope, and mercury injection test analysis as mothods. Combined with data of geological logging and oil testing and results of chemical analysis and previous research results by others. comprehensive evaluation and prediction of the characteristics of Chang9 oil set are made. Analysis of the type of Chang9 oil set and the relationship between oil and water based on the top structure of the stratigraphy in Hongjingzi-Luopangyuan area and the accumulative rules and control factors of Chang9 oil set reservoir were also accomplished, with final summarization of the main control factors. The main research progress include:1. Chang9 oil set is a shallow water delta sedimentary system, of which the lake shoreline migrates in a large range and the study area is located in the intersection with multi sources. It is for the first time the continuous, interval, interbed and lens these 4 types of sandbody superimposition are classified in the isochronous stratigraphic framework through high resolution sequence stratigraphy analysis.2. Chang9 oil set isochronous stratigraphic framework and small layer sandbody comparison charts are drawed in Hongjingzi-Luopangyuan area through high resolution sequence stratigraphy research and lithofacies paleogeography mapping method. Based on these results, the charts of sandbody cumulative thickness and sand to the stratigraphy ration contour and the sedimentary facies distribution maps are drawn, and the model of edimentary facies is built.3. On the research of Chang9 sandstone diagenesis, the chlorite, laumonitite, and illite/smectite mixed layer are found to makethe greatest impact on Chang9 reservoir. The single aspect of chlorite rim cementation is mainly developed in the west, and single illite/smectite mixed layer rim cementation is mainly developed in the north and east, while chlorite and illite/smectite mixed layer rim cementation transition zone is found in the remaining parts of the study area. All kinds of clay minerals rim cementation has protective effect on primary intergranular pores, but the existence of illite/smectite rim cements will indirectly affect the oil industry development.4. Through the petrology, geochemistry and other methods, a comprehensive analysis and evaluation of Chang9 oil set were prepared and the comprehensive evaluation maps of Chang9 oil set and Chang 92 and Chang 91 oil section and drawed separately based on detailed analysis of reservoir characteristics.5. The main reservoir types of structural-lithologic and lithologic are separately developed in Hujianshan and Hohgjingzi-Luopangyuan area. Chang7 oil set is the main oil source of Chang9 and the source place is in the zone of Hongjingzi-Xiaojianzi-Luopangyuan. The two main source crude hydrocarbon vertical migrations of Chang9 developed in early and late Cretaceous through the channel of sandbody itself and fractures. The characteristics of the hydrocarbon cumulative model are upper generation & lower accumulation, high pressure driving, sandbody and fractures transportation and multiple and near sources injection. The oil and water distribution difference in the reservoir is clearly vertical6. The hydrocarbon cumulative model of Chang 9 oil set can be described as:the light crude oil provided by Chang7 super high pressure and good quality source rocks were transported through structural fractures and sandbody under the high pressure between the source rocks and the reservoir before the densification of the reservoir. The transportation and accumulation is vertically beaded and near the source. Therefore the main controlling factors of the accumulative model include the distance between the source and destination, pressure difference and transportation channel, which directly impact on the enrichment of hydrocarbon among the reservoir.7. With comprehensive analysis of the depositional system, reservoir characteristics and reservoir accumulative rules, the oil source, channel, pressure difference are thought to be main control factors of Chang 9 oil set hydrocarbon accumulative model. Chang91 oil section reservoir is better than that of Chang 92.