Petroleum Systems Analysis and Exploration Direction of Martaban Basin in Andaman Sea
Martaban Basin located in Andaman Sea, is a typical back-arc strike slip and extension basin. The tectonic evolution of Martaban Basin is closely related with the oblique convergence of the Indian beneath the Myanmar plates. Five structural provinces are evident in the basin. From west to east they are: volcanic arc uplift belt, west slope belt, center depression belt, east slope belt and mergui terrace. Its depocenter is controlled by the Mergui and Sagaing strike-slip faults and the mainly sources are from the Irrawaddy River in the north and Salween River in the northeast respectively.
From the analysis of characteristics of petroleum geology, the Martaban Basin comprises shallow biogenic system and deep thermogenic petroleum system. The Pliocene-Pleistocene delta front sandstones interbedded with shales are the main plays of shallow biogas. Many shallow biogenic gas reservoirs have recently been discovered in Miocene-Pleistocene strata in basin, mainly Methane with δ13C values to be less than -60‰. Most of them occurred within or adjacent to the depocenter filled with approximately 5000 m thickness of Neocene sediments. The reservoirs are superposed with each other in vertical. The seismic data of biogenic gas sections in Basin displays reflection characteristics such as blanking, enhanced reflection patterns, bright spots, flat spots, reverse polarity and increase in amplitude with the offset, which are easy to identified. The trap types are mainly faulted blocks, and faults are the favorable migration pathways. The biogas distribution is charged by biogas source rocks, sedimentary facies zone and lateral sealing of faults. The Middle Miocene hemipelagic shales overlie the Oligocene-Lower Miocene reef limestones and shallow marine sandstones, which comprise the main plays of deep thermogenic gas. There are several gas discoveries in the volcanic arc uplift belt and the east slope belt. The trap types are mainly faulted-anticlines, reef traps and structural-stratigraphic combined traps, and the favorable migration pathways are faults and unconformities. There are different key control factors of controlling thermogenic gas accumulation in each structure province.
Future exploration should typically direct at faulted blocks and horst in the center area of basin for the shallow biogas, and the western volcanic uplifts, central inherited uplifts and structural terraces in eastern ramp region for the thermogenic gas respectively.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California