Abstract:

As the passageway of hydrocarbon migration, the pathway system is very important for hydrocarbon accumulation. In terms of the research
of fault and its activity, depositional system and unconformity in Weibei Sag,we put forward that there are three kinds of pathway system factors including sand body, fault and unconformity surface. They formed fault-unconformity pathway system and fault-unconformity-sand body pathway system. Weibei Sag has two hydrocarbon source areas which are located at the northern depression belt and eastern Zaohu faultednose belt. The eastern Zaohu faulted-nose belt developed lots of complex fracture structure, but the northern depression belt developed little faults. Weibei Sag developed six unconformity surfaces,among which Ng/Es₄ or Ng/ Ek₁ and lower Ek₂/Ek₃ are regional unconformity surfaces. For these reasons, different regions developed different pathway system in Weibei Sag. Based on the analysis of reservoirs in Weibei Sag and the characteristics of pathway system, we concluded the controlling of different passage system on hydrocarbon migration and accumulation. We find that sand body pathway system may control the forming of lithologic pinchout reservoirs and sand lens reservoirs, fault pathway system
may control the forming of unconformity-fault reservoirs, fault-block reservoirs and structurallithologic reservoirs, fault-unconformitypathway system may control the forming of fault-block reservoirs, lithologic reservoirs and fault-lithologic reservoirs, and fault-unconformity-sand body pathway system may control the forming of lithologic pinchout reservoirs, unconformity reservoirs, fault-block reservoirs and fault-lithologic
reservoirs. The study result is favorable for reservoir exploration and prediction in Weibei Sag.

Key words:  sedimentaryfeatures , distribution rule , Lower Cambrian , LongwangmiaoFormation , central Sichuan Basin