Formation mechanism and development model of the Lower Paleozoic buried hill reservoirs in the Jiyang Depression
The Lower Paleozoic buried hill is key target for the exploration of oil and gas in depth in the Jiyang Depression,however,the reservoir is characterized with strong heterogeneity and hardly effective prediction.Based on observations of drilling cores and their thin sections,and logging data of drilling holes,combined with data of water-rock experiments,we have analyzed development characteristics of the reservoir,clarified the mechanism how to make the reserve of oil and gas in the reservoir be increased,and established the development model of the reservoir.The research shows that the Lower Paleozoic buried hill reservoirs in the Jiyang Depression are characterized with dominent secondary pores including dissolution pores,holes and cracks which were controlled by lithology,cracks,atmospheric fresh water,hydrothermal fluid and organic acid fluid.There are two sets of reservoir systems including the weathering crust and the internal ones distributed vertically.These two reservoir systems are separated by densely impermeable layers.Due to the reworking of relatively developed limestone in the weathering crust reservoir system by the leaching of multi-stage atmospheric freshwaters through the communicated structural cracks and fissures,the karst-fracture-cavity reservoir was formed in the weathering crust.The relatively developed dolomite of the internal reservoir system is more susceptibly ruptured and fractured by the structural movement.In the case of structural crack communication,the dissolution of cracked dolomite by organic acid fluid resulted in the formation of fracture-pore type reservoir in the internal system.These two reservoir systems could be also reworked by the dissolution of the Yanshanian hydrothermal fluid along the structural cracks.Therefore,the rock type is the basis of dissolution,the structural crack is the bridge of fluid,and the effective matching of fluid dissolution with structural cracks is the key factor to the high quality reservoir formation.The research results have important reference significance for the reservoir prediction and oil and gas exploration in the carbonate buried hills in the study area and other areas with similar structural background in the North China platform.
万方数据
维普
