Source Rock Potentials and Hydrocarbon Discoveries in Salin Sub-Basin, Myanmar
Salin sub-basin called Central Myanmar Basin, located in the Central Myanmar Tertiary Basin Complex, is one of the most petroliferous basins in onshore Myanmar. It covers an area of approximately 9453 sq. mile. Tertiary sediments were mainly deposited in this basin. Sediments thickness is approximately over 55,000 ft. The south central part of the basin is the deepest one with steep flanks. The northern half of the basin is substantially shallower than the southern half because of regional, episodic, uplift in the north. The basin is defined by a regional north-south trending syncline with many normal, reverse and thrust faults on both flanks. Upper Eocene to Middle Miocene sandstones are major producing reservoirs associated with compressive, thrust-related anticlinal combination traps. The structural /combination traps were formed by the first phase deformation in Early Miocene followed by the second deformation during the Pliocene to Recent. Geological and geochemical analyses, including pyrolysis, vitrinite reflectance determination, gas chromatography (GC), gas chromatography – mass spectrometry (GC-MS), and carbon isotope ratio of the samples, were carried out in order to characterize the source rock potentials and depositional environments of the strata. Based on the current analysis data, the Salin Sub-Basin is dominated by fluvial-deltaic / Humic-terrestrial origin as major sources. It is noted as generally moderate to very good hydrocarbon generation potential in Eocene shales and moderate to good hydrocarbon generation potential in Lower Oligocene shales. The 1D models were constructed on different locations in the basin. The modeling results indicate significant differences in timing of hydrocarbon generation from formation to formation throughout the basin from north to south. The modeling results of pseudo wells in the northern part indicate that the Upper Cretaceous Kabaw shales and Lower Eocene Laungshe shales might have passed main phase of hydrocarbon generation throughout Eocene and Oligocene respectively. Middle Eocene Tabyin shales began to enter main phase of hydrocarbon generation in Middle Pliocene and are still in main hydrocarbon generation phase at present. Large volumes of hydrocarbons generated from Kabaw and Laungshe shales are likely to have been expelled prior to the formation of traps (Early Miocene & Late Pliocene). Within the basin, oil bearing strata are progressively younger from north to south, Eocene - Oligocene strata in the north and Oligocene - Miocene strata in the south. The hydrocarbons generated from Salin syncline throughout successive times were migrated into structurally high and uplifted fault blocks laterally or vertically along the fault conduits all over the first line of structures, namely Letpando, Thargyitaung, Sabe, Ayadaw, Yenangyat, Chauk, Yanangyaung, Mann and Htaukshabin where commercial oil and gas have been discovered.
AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018