Abstract:

Abstract: Nanpu Sag has well developed faults, yet the relationship between the faults and abundant oil and gas is not clear in the study area. The paper studied the basic characteristics of faults through seismic interpretations of structures and statistical analysis of the fault distribution. On this basis and combing with the conditions of trap, reservoir and hydrocarbon migration, the paper researched the controlling effects of the faults on the oil and gas accumulation in Nanpu Sag. The results indicate that the majority of the faults trending NEE or NE in the Nanpu Sag, showing structural styles such as “flat and ramp style”, “listric style” and “domino style” and so on in the section. The faults within the Nanpu Sag can be classified into three orders, with the firstand secondorder faults being developed in the Paleogene. The first order faults control the formation of the sag and are characterized by the earliest development, long duration and strong intensity. The secondorder faults control the local structures, and were developed later than the firstorder faults. The thirdorder faults are mostly secondary faults formed since the Neogene with weak intensity. Unique petroleum geological conditions occur in the study area due to the control of faults of different orders. The controlling effects of the fault system on hydrocarbon accumulation are represented in three aspects, that is, the occurrence of faults benefits for the formation of various types of traps, the fractures caused by faults enlarge the reservoir space for oil and gas accumulation, the diversity of sealing ability of faults prompts hydrocarbons to migrate from the deep to shallow reservoirs where they accumulate.