Multi-factor Coupling Analysis on Property Preservation Process of Deep Buried Favorable Reservoir in Hinterland of Junggar Basin

Key words: 
• hinterland of Junggar Basin /
• Sangonghe Formation /
• deep buried reservoir /
• property preservation process /
• multi-factor analysis

Abstract: Although buried in depth between 3 800~4 600 m, reservoirs of Sangonghe Formation in Mosuowan area have a relatively favorable physical properties, and become one of the key formations in hydrocarbon discoveries in hinterland of Junggar Basin. Thus, for later oil-gas exploration and development, it is of great significance to make clear multi-factor relationships and genetic mechanism of favorable reservoirs which are deeply buried. Through microscopic thin section, scanning electron microscope analysis, physical property analysis, X-ray diffraction of clay mineral, and well drilling- logging data, together with burial history, tectonic evolution, and based on single factors analysis of reservoir property preservation, present paper carries out a detailed multi- factor coupling analysis and discussion in property preservation process of deep buried clastic reservoir of Sangonghe Formation. The results demonstrate that favorable depositional conditions, strata overpressure, changes of diagenetic fluid properties and paleogeotemperature, these four factors respectively make the reservoir properties effectively preserved. Furthermore, the process of property preservation process can be divided into 5 stages, and during different evolution period, the main controlling factor of property preservation is different. During the slow shallow burial period, the main controlling factor were shallow depth and the beginning of strata overpressure; early to mid stage of first quick deep burial period the main factor was strata overpressure; mid to late stage of first quick deep burial and early to mid stage of slow deep burial period the main factor changed from strata overpressure to consolidation of cements; mid to late stage of slow deep burial period the main factor were low geothermal gradient and the dissolution of organic acid; while the second quick deep burial period to nowadays, the main factor are strata overpressure and decrease of geothermal gradient, and finally an oil-gas accumulation and comprehensive diagenetic evolution model of Sanggonghe Formation is proposed.