Study On Neogene Hydrocarbon Migration System In Chepaizi Area

Guided by the theory of petroleum migration and geophysics, Neogene oil migration system was systematically studied using seismic data, mud logging, logging data and sedimentary research in Chepaizi.The Shawan group is divided into six sets of skeleton sandbody according to the combination of sandbody and the caprock. In order to study the framework of skeleton sandbody and its impact on the transportion effectiveness more accurately, the concepts of lateral connectivity rate and vertical connectivity rate are presented innovatively. Combining with sand distribution, lithology, porosity, permeability and connectivity, the migration system effectiveness evaluation is carried out . The Sandbodies in Sha1 Member is good in eastern and southern passage, and the northern passage is bad. The Sandbodies in Sha2 Member is good in eastern passage, The north and south are poor, The Sandbodies in Sha3 Member between the well of Pai 602 and Pai 22 is good.According to lithology and logging features the structure of unconformity are identied and there develop three types, including overlap, truncation and parallel unconformity in this Region. The log response features of typical and atypical structure are identified, Moreover, lithology distribution and thickness of unconformity are studied systematically in order to evaluate the effectiveness of unconformity passage system. The effective range of bottom unconformity in Shawan group concentrated in the Midwest and the lower part is in the east. The effective range of Taxihe bottom unconformity in the upper part located in the eastern and south-west, the lower effective range concentration between Pai11 well and Pai21 well.The study area developed many low-level normal faults in Himalayan, Those faults have small throws and extend shortly, most of which control the reservoirs. Vertical seal of these faults is poor, lateral seal is poor in Sha1 Member, however, fault sealing is good in Sha1 and Sha2 Member.Combination of Skeleton sand, unconformity and fault and the transportion effectiveness determines oil and gas migration pathway. Based on the analysis of hydrocarbon controlling factors, Shawan hydrocarbon migration patterns are identified combined with local tectonic setting.