Changes in Geophysical Technology on Deepwater Exploration in Eastern Offshore Vietnam
Authors: Tan Mai Thanh , Minh Nguyen Hong , Ha Mai Thanh 
Published: October 2008

The eastern deepwater (&gt;200m) extensions of the basins in Vietnam's marine have not been intensively explored. This paper presents the geological characteristics of the deepwater eastern offshore Vietnam and the challenges in geophysical technology to study them.

The petroleum systems and geological structure of the deepwater areas are very complicated and different from those in shallow water areas (complex structural and stratigraphy traps, carbonate and sandstone reservoirs with high temperature and pressure, etc.)

With the complicated geological and technical conditions of the deepwater areas, it is necessary to enhance the effect of the geophysical processing for oil and gas. To solve these problems, many of the latest technologies have been applied such as pre-stack depth migration, geostastical modeling, seismic attribute analysis, coherency, 3D visualizationtechnology, etc.

Many of the technologies are still undergoing development but we can expect them to be more developed and reliable within the next few years. For example, HTHP logging while drilling, non-conventional in deepwater areas will be more focused on discovering new oil and gas fields and increasing production.

Geological characteristics of Eastern Offshore Vietnam

The geological formation and evolution in Eastern Offshore Vietnam are closely related to the processes of expansion and collision between Eurasian, Pacific and Indo-Australian plates. We can distingunish the Sunda marginal sea, the continental structure of the Indochinese peninsula, the islands of the Philippines-South China, Indonesia, and the structure of the marginal East Sea of Vietnam. Southeast Asiais considered to be not only a zone adjoining the Asian-European and Australian continents, but also a zone separating the Pacific and Indian Oceans. It is a micro-plate linking the Australian plate in the east and the Indian plate in the west. All the three together form the Gondwana plate. Structurally, the Cainozoic basins in Southeast Asia formed and evolved on a heterogeneous Tertiary fundament. The main features of the tectonic plan are created by the Alpi folding phase. The transforming process of the structural plan of Southeast Asia led to a complex combination of the microplates of Burma - Thailand, Kontum - Borneo and Ocean - East Sea. During the transitional process, the borders between these zones are moved strongly, and they are characterized by active magmatism.

The Tertiary depressions in Southeast Asia are filled with sediments of the Eocene, Oligocene and Quaternary ages, with a great thickness (5,000 - 10,000m), and differ in sedimentation characteristics. The Thailand, Malaysia and West Natura depressions are mainly composed of terrigenous sediments, accumulated in the neritic continental conditions, the Sarawak, Sabak and North Western Palawan depressions are chiefly composed of terrigenous sediments and carbonate generated in the conditions of shallow and deep seas.

The Cainozoic sedimentary basins in Vietnam's marine were formed under the influence of tectonic activities of various origins. The relative movements of the micro-places in the Cainozoic basins in the Southeast Asia region played an important role in their formation.