Abstract All of Myanmar’s commercial onshore oil- and gas fields occur in Cenozoic sedimentary rocks in the Central Burma Depression. The state oil company, Myanmar Oil and Gas Enterprise (MOGE), and most observers divide this very large Cenozoic downwarp into at least seven basins (Fig. 4.1), which is the scheme adopted here for descriptive purposes; others prefer to refer to these seven basins as sub-basins. They can be grouped under two main headings: a northern pair of basins (Chindwin and Shwebo-Monywa basins) in which a few discoveries have been made (in the former) but from which there is no commercial production at present; and a southern region which contains all of the currently producing fields. The boundary between southern and northern regions is at about the latitude of Mandalay, c. 22°N (Fig. 4.1), where there is a slight east–­west structural arch which marks the southern boundary of the Chindwin and Shwebo-Monywa basins. An alternative classification is along plate-tectonic lines, the forearc domain comprising the Chindwin, Salin, Pyay and less certainly the Hukawng basins, and the back-arc domain comprising the Shwebo-Monywa, Bago Yoma and Sittaung basins. The drawbacks of this scheme are that: (1) it is not clear into which domain the Hukawng Basin should be placed; and (2) the Ayeyarwady Delta Basin straddles the buried magmatic arc and so is in both the forearc and back-arc domains. Because of the contentious plate-tectonic categorization of the Hukawng Basin and its frontier exploration status, we have chosen to describe it separately (in Chapter 5) from the basins which lie clearly in the Central Burma Depression.

Abstract The Myanmar Ministry of Energy has identified as prospective the three basins discussed here, but they have seen little exploration activity. Arguably the Hukawng Basin is distinct from the others insofar as exploration drilling has been carried out, and a potentially prospective stratigraphic succession has been encountered. Moreover, this basin lies on trend with the petroliferous basins of the Central Myanmar Depression. But it would be hard to argue that it is anything other than a frontier basin, and for that reason it is included here. For various reasons we consider the other basins discussed here to carry higher risk. The Ministry’s onshore map accompanying the details of the 2013 bidding round included two blocks on the western flank of the Shan Plateau in what MOGE calls the Kalaw Basin: Blocks PSC-U and PSC-V. These blocks, which lie NE and east of the capital Naypyidaw (see Chapter 4, Fig. 4.2), were not however included in their list of blocks on offer. It is an area of complex folding (e.g. Garson et al. 1976), much affected by NNW–SSE faults of which some (such as the Panlaung Fault) are considered by Ridd & Watkinson (2013) to have had a history of dextral strike-slip movement during the Late Cretaceous–Palaeogene. The western part of the two blocks (i.e. west of the Panlaung Fault) exposes Palaeozoic sediments of the Slate Belt intruded by granites (Mitchell et al. 2007), and is considered to have no petroleum potential. The eastern part of the blocks is more difficult to assess. Above the ubiquitous Permian–Triassic Plateau Limestone (=Shan Dolomite), Triassic flysch (Shweminbon Formation) passes up into non-marine younger Mesozoic rocks including red beds and coal-bearing intervals.