The internal structure of Liaozhong No.1 strike slip fault and its control on hydrocarbon accumulation: a case study of Jinzhou A Structure

The discovery of Jinzhou A Structure (JAS) in the Liaodong Bay, NE China, marks a breakthrough of oil-gas exploration in less-developed area of accommodated fault in the Liaozhong No.1 strike-slip fault (No.1 SSF) zone. To determine the main controlling factors of hydrocarbon accumulation in the JAS, based on drilling, logging, and seismic data, the No.1 SSF and its internal structure were anatomized in the JAS, and its controlling effect on hydrocarbon accumulation was clarified. Results show that first, the amplitude and P-wave velocity changed obviously near No.1 SSF. The range of these changes showed that the internal structure and the scale of the No.1 SSF increased from shallow to deep. Secondly, the internal structure of the No.1 SSF was revealed by using multi-well lateral comparison in bulk density (as in ZDEN), neutron porosity (as in CNCF), and delta compression time (as in DT) data, and by using dipole acoustic reflection imaging technology. Approaching to the No.1 SSF, the ZDEN data decreased first and then increased, while the CNCF and DT data showed the opposite trend, indicating the transition from surrounding rock to fault fracture zone and then to the fault core. Thirdly, the JAS in the No.1 SSF developed a dual structure composed of fault fracture zone and fault core. The fracture zone has good porosity and permeability, which is a favorable channel for vertical migration of oil and gas, while the fault core has poor porosity and permeability, which is conducive to lateral sealing of oil and gas.