Abstract:

Observation and analysis of cores and thin sections,combined with cathodeluminescence identification technique,reveal that at least 3 stages of structural fractures were developed in the Middle-Upper Ordovician limestone formation at the platform edge,Tazhong oilfield.Among the fractures,the one formed in Himalaya pe-riod had greatly improved the quality of reservoirs.It is suggested that the numerous tiny to small fissures in cores could enhance permeability and connect larger fractures with matrix pores.The authors present in this paper the model of reservoir formation which emphasizes the controlling roles of fractures to reservoir formation,and regard burial dissolution as the main mechanism of matrix pore growth.They also point out that the future exploration targets in the basin shall be fractures in the favorable sedimentary facies belt.

Key words: cathodeluminescence, phases of fracture, burial dissolution, pattern of reservoir formation, platform edge, Tazhong area