Interpretation of 3D seismic data from the compression domain of Niger Delta

related seismic attribute extraction and BSR numerical modelling are carried out in this paper to study the seismic characteristics of the present and paleo-bottom simulating reflections (BSRs)

and the controlling factors of BSR vertical migration.In the study area

the present and paleo-BSRs

representing present previous and locations of the base of gas hydrate stability zones (GHSZ)

are scattered and mainly located in areas with well-developed fluid pathways including folding faults

gas chimneys

and diapire structures.This indicates that fluid migration conditions control the occurrence of BSR.Compared with the present BSR

the paleo-BSRs are of weaker amplitude

and distributed in much more limited areas.The amplitude of the paleo-BSRs is interpreted to represent petrophysical interfaces caused by diagenesis driven by previous gas hydrate.The depth of the present BSR deepens as the seabed water depth increases

but the thickness of GHSZ is relatively stable

about 425 m.The upward resetting of the BSR is a result jointly contributed by various factors in the geological history.The toe-thrust belt of the Niger delta is characterized by intense tectonic activities

high sedimentary rate

and well developed fluid migration pathways

including fault and diapire

for heat flows from deep to shallow.Besides

the underlying oceanic and transitional crusts allow higher heat flows

and marine mudstones have higher heat sealing capacity.All these are driving the upward resetting of the BSR.In addition

higher gas hydrate saturation formations in the study area feature higher amplitude anomalies on the present

upper BSR with positive polarity

mainly on top of anticlines and gas chimneys

indicating the effective control of fluid migration pathways on gas hydrate accumulation.The occurrence of free gas zones (FGZs) underlying the present BSR is limited

and only thin FGZs occurred in fold belts with well-developed fluid migration pathways.