Morphology and Significance of Seafloor Depression in the West of South China Sea

In this paper we describe two seafloor depression features, one is pockmark the other is collapse structure, discovered in the west of South China Sea. The pockmarks are the manifestation of fluid escape at the seabed and the collapse structures are the products of seabed failure caused by tectonic activity (diapir, volcano, fault and so on). Generally pockmarks may exceed tens to hundreds of meters with elongate or circular shape in plane and U-, V-shape in cross-section. The most important feature is that you can find fluid migration pathway (gas chimney or fault) under the bottom. Collapse structures can reach thousands of meters in diameter with circular fault boundaries. The cross-section shape is irregular.

Pockmarks and collapse structures both have important geological significance for offshore oil & gas exploration and development. Pockmarks may indicate the hydrocarbon play or gas hydrate directly. On the other hand pockmarks and collapse structures may present a potential hazard for drilling and pipeline laying.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California