Abstract

The Onshore Central Myanmar Tertiary Basin (CMTB) is an arcuate physiographic and tectonic depression, about 1300 km long and 200 km wide. According to seismic evidence it originated in the Eocene as an array of pull - apart rift segments along the oceanic/cratonic transform zone between the Indian and Southeast Asian lithospheric plates. From the late Eocene to the present, this basin has been influenced by oblique subduction of Indian oceanic crust beneath the Southeast Asian Craton and by dextral slip along an intra cratonic transform fault (Sagaing Fault) that parallels the eastern margin of the basin.

This Tertiary basin is divided into tectonic segments (sub-basins), in which the Cenozoic terrigenous clastic fill is as thick as 10 km. A line of Cenozoic volcanics in the axis of the Central Basin marks the approximate suture between the cratonic eastern substrate and subducting oceanic western substrate. Therefore the Central Basin is interpreted as a forearc-backarc basin pair divided by the Mount Popa Cenozoic volcanics.

Most of the major oil and gas fields are located within the CMTB. The proven reservoirs comprise clastic Oligo-Miocene and lesser Eocene sandstones. Geochemical data indicates the presence of Type II/III kerogens in the Tertiary sequences. The consistent presence of oleanane in many of the oils indicates land plant derived Tertiary source. The majority of oil and gas entrapment is associated with compressive-thrust related anticlines. Present day oil and gas production comes mainly from Oligo-Miocene sandstones.

Gas condensate reservoirs occur throughout the Central Myanmar Basin. All analyzed so far represent fractionated rather than cracked oil. This suggests deeper untested oil potential exists in the region. Eocene reservoirs, proved to be productive in the northern part of the basin, remain to be tested in other parts.

Recent Signing of Performance Compensation and Improved Petroleum Recovery Contracts for some major oilfields and PSC contracts for RSF Blocks by foreign oil companies will encourage further exploration and development efforts for oil and gas in the Central Myanmar Basin.