Study On The Characteristics Of Ordovician Palaeokarst Reservoir Of Qianmiqiao Buried Hill In Huanghua Depression

The paleokarst reservoirs of Qianmiqiao buried hill in Huanghua depression have the characteristics of strong heterogeneity that it is hard to make a prediction of favorable exploration area. In order to meet the needs of the next exploration work, this paper makes a systematic study of Ordovician karst reservoir evolution, property characteristics, macro and micro apertue structure characteristics by the experimental analysis of a large number of on-site cores observations, the identification of conventional cast thin, cathodoluminescence, electron microprobe combined with the data of logging, seismic interpretation. And this paper points out favorable exploration areas in the region based on the detailed criteria for the classification of the type of reservoir. As a summary, it mainly makes the following conclusions.1. The formation and evolution The Qianmiqiao buried hill karst holes are divided into three stages. That is respectively karst development stage, karstification stage and the Karst adjustment stage. The reservoir space is mainly composed of apertues, holes and fractures. There are few primary porosity, most of them are dissolution pores and cracks.2. There are significant differences between Qianmiqiao Ordovician carbonate reservoir’s Matrix porosity and permeability. Cracks have a significant role in the improvement of reservoir permeability but the occurrence of cracks has a big influence on permeability.3. For Qianmiqiao buried hill of Ordovician carbonate reservoir regard porosity and caverns as the main reservoir space. and more developmental characteristics of various types of cracks on different levels that we can divide the level of study area reservoir into four categories.4. The degree of reservoir development in the study area is mainly affected by degree of dolomite development, karst palaeogeomorphology in morphology, degree of fracture development and some other factors. The forward geomorphic units of paleokarst are the development belt of effective reservoir. Crack and associated corrosion holes are the main factors to the high porosity and permeability characteristics of Qianmiqiao Ordovician weathering crust carbonate reservoirs. 5. The development of Qianmiqiao Ordovician weathered crust karst reservoir mainly focuses on the Fengfeng formation, the1Segment of Majiagou formation and the Upper2Segment of Majiagou formation. But the development depth changes greatly. The degree of development of karst reservoir holes and the lateral changes in the physical properties have a obvious nature of divison. According to the above analysis, two favorable exploration areas are divided by us:Banshen7-Qian18-18-Banshen703wells area and Banshen4well area.