The Types of Unconformity Migration Passages and Characteristics of Hydrocarbon Transport

Based on the study of the spatial structural characteristics of unconformity,this paper has recognized two kinds of unconformity migration passages,dual migration passage consisting of two types of highly effective transport passages,and single migration passage. The dual migration passage occurs between conglomerate underlying unconformable surface and overlying half-weathered rock. The pores connected to the bottom conglomerate,fissure system formed by half-weathered structural rock and discharge,and weathered solution pore can be regarded as the major passages for hydrocarbon transport. Petrochemical analysis on these rocks from unconformities suggests that the half-weathered pore-cavity-fissure system is more capable than the pores connected to the bottom conglomerate in oil transport. The result shows that different migration passages characterize oil transport. During the whole history of earth development,structural fracture system and dissolved pores have been major channels for unconformity oil transport. For the uncomformity formed by soft formation,discharge and weathered-fracture system and pores connected to the bottom conglomerate are the main migration passage; when overlying sediments reach to a certain thickness,the pores connected plays major role in oil transport. For the uncomformity formed by hard formation,discharge-weathered fracture system and pores connected to the bottom conglomerate are the main migration passare way.