INTERNAL CHARACTERISTICS AND MAIN INFLUENCING FACTORS OF BURIED HILL FAULTS IN THE SOUTH FAULT ZONE OF ZHU III SUB-BASIN, PEARL RIVER MOUTH BASIN, CHINA

The buried hill with oil and gas shows in research area is controlled by faults, and no large karst caves have been developed. The reservoir is mainly of fracture type, so whether the fracture zones around the faults are developed or not and their distribution ranges are great influenced on the favorable reservoirs.

Our research utilized the Landmark software to make structural interpretation and MOVE software to recover the history of structural evolution. We went through the observation of cores combined with the preference of logging curves (sonic differential time, resistivity, natural gamma, density, etc.) to establish a model of the faults (fault core + fracture zones), then we use the likelihoods and curvature attributes to portray the fault structure. In addition to the qualitative description of the influence of lithology and burial depth on the internal structure by means of coring and logging, we focus on exploring the influence of fault activity (fault distance, fault activity intensity, etc.) on the development of the internal structure.

We obtained the planar and spatial distribution characteristics of strata and faults in the work area, and drew the structural evolution diagrams. The "binary structure" of the basement location faults is generally developed with both fault cores and fracture zones, and the fault cores have structural Breccia developed, and the fracture zones have network fractures developed. The density, acoustic time difference and natural gamma values of the fault core are slightly larger than those of the fracture zone, and the RTC curve of the fault core is flat, and the curve of the fracture zone part of the curve varies drastically. The maximum likelihood attribute and curvature attribute show that the fracture zones in the deep part of the fault are wider than those in the shallow part, and the fracture zones are more developed in the stress-concentrated parts of the fault such as turning, convergence, and bifurcation. The paleodrop and fault activity rate of the Cenozoic are calculated isometrically on the strike, and show that the thicknesses of the fault cores and the fracture zones are positively correlated with the strength of the fault activity.

Acknowledge: The research was supported by special project for the operation of scientific research institutions in Shandong province (2021QNLM020001) .