--> --> Controlling Effect of Normal Fault Related Folds to Hydrocarbon Migration and Accumulation

2018 AAPG International Conference and Exhibition

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Controlling Effect of Normal Fault Related Folds to Hydrocarbon Migration and Accumulation


Fault-related folds have been studied for a long time since the first case has been found in 1934,but most geologists put their focus on reverse fault-related folds at that time, these folds have large size, high degree of deformation and clear geometry, can be analyzed quantitatively. With the oil and gas exploration going, more scholars found fault-related folds in extensional areas as Gulf of Suez and Rhine graben, break the law which fault-related folds generate in extrusion and shrink tectonic settings only. Many normal fault-related folds have been discovered in rift basins in the northeast of China lately, based on the previous work, we classified these folds into three types according to the formation and growth of related normal faults: fault plane dip variation related folds namely rollover; fault displacement gradient related folds which includes drag folds, reverse drag folds, transverse displacemen gradient folds and propagation folds; compound type folds mainly formatted in the fault segment mode, including planar transform structure, vertical superposition folds and compensatory compression anticline. This plane can easily tell the distinction between different types of folds, especially rollover and reverse drag folds, also propagation folds and drag folds. Normal fault-related folds have shown their importance in hydrocarbon exploration and exploitation through two ways: (1) with the help by high transporting ability of normal faults, these related folds can take the advantage collecting the oil which migrate by faults immediately, being the effective traps where hydrocarbon accumulation, thus can be a reasonable explanation for the phenomena that oil has a banding distribution along main faults; (2) for sub-seismic faults, they always be missed due to the small size and displacement. This article through reverse psychology, setting the source faults in Songliao Basin as a representative case, using the strata deformation around normal faults namely normal fault-related folds to determine the real active stages of source faults, thus solved the problem that oil accumulated near the so-called “non-source faults” successfully.