--> Effects of Strike-slip Deformation on the Petroleum System West of Thayet, Central Myanmar

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Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential

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Effects of Strike-slip Deformation on the Petroleum System West of Thayet, Central Myanmar

Abstract

Northward movement of the Indian Plate relative to Asia during the Cenozoic created dextral strike-slip deformation affecting the petroleum systems in Central Myanmar. Oligocene transtension and Middle Miocene-Recent transpression played an important role in the maturation of the prolific Eocene-Oligocene source rocks as well as the deformation of the prospective Oligocene-Miocene reservoirs into anticlinal traps in the well-known fields of the region. Thayet is located on the eastern flank of a restraining-bend uplift linking two N-S trending dextral strike-slip faults: one on the western boundary of the Salin Basin and another on the eastern boundary of the Pyay Embayment. Recent subsurface study in the eastern part of the structure revealed a NW-SE trending sinistral-reverse oblique-slip fault running just south of the Thayet Town, after which it is named. Seismic interpretation suggests that the Thayet Fault was initially developed in the Eocene-Early Oligocene as steeply dipping fault segments that merged into a through-going fault in the Late Oligocene-Early Miocene and continued its activity to the Present-day. Initial transpression in the area commenced during the Early to Middle Miocene and created NW-SE trending anticlines that were charged with hydrocarbons during the Middle to Late Miocene. Certain anticlines with northerly trends were developed at restraining bends along the Thayet Fault. Reverse displacement component along the fault also resulted in the uplift of the region to the north where the Eocene-Oligocene source rocks entered the oil window and generated oil with associated gas; south of the fault, most of the same source rocks crossed the gas window thus yielding both liquids and unassociated (thermogenic) gas. Late Miocene-Pliocene regional transpression amplified the NW-SE trending folds in the area and possibly caused upward re-migration of existing Middle Miocene accumulations along young or reactivated faults to shallow pools currently produced by local hand-dug wells.