oa Structural Evolution of the Hawasina Window (Oman Mts) and its Relation to Hydrocarbon Generation

Extensive field studies in the Hawasina Window region<br>of the Oman Mountains led to the recognition of<br>four major structural processes, linked with: (1) intraoceanic<br>obduction; (2) emplacement of ophiolites onto<br>the Arabian continental margin; (3) unroofing of the<br>subthrust margin; and (4) Tertiary folding and extension.<br>The first Cenomanian process is not relevant to the<br>formation of hydrocarbons in the Arabian margin. The<br>second Turonian process led to the formation of out-ofsequence<br>nappes and ductile extension. It provided tectonic<br>burial of the margin. An omnipresent NE-vergent<br>syn-cleavage folding is also associated to emplacement.<br>The shortly following tectonic unroofing rafted ophiolite<br>blocks away from the window areas. Break-up of the<br>nappes is suggested along a pre-existing strike-slip fault<br>system. Isostatic compensation led to uplift and folding<br>of the nappe succession. Finally the Tertiary Period was<br>characterised by across-strike normal faulting and numerous<br>steps of folding, ramp-thrusting and transpression.<br>This process uplifted potential reservoir sections in<br>Late Tertiary times. The play concept proposes classical<br>Natih source rocks and reservoirs in the autochtchon.<br>Since original porosity is reduced due to tectonic loading,<br>fracture porosities in the limestones and Upper<br>Permian-Triassic dolomites are considered viable in the<br>reservoir rocks. Seals are formed by shaly sections of the<br>autochtchon (Salil, Nahr Umr and Muti formations) and<br>of a regional evaporitic detachment at the base of the<br>Hawasina Nappes. The major upwarp of autochtchon<br>and three local antiforms in the Hawasina Window form<br>the potential trap(s). Vitrinite reflectance and clay mineralogy<br>both reflect anchimetamorphic conditions for the<br>Hawasina Nappes. Thermal conditions probably did not<br>exceed late-stage, gas maturity levels. The main burial is estimated to have lasted for 10 million years. Therefore<br>the Hawasina Window area is considered gas-prone.<br>Both MOL Hungarian Oil & Gas Plc and Hawasina LLC<br>Oman Branch wish to thank the Exploration Directorate<br>of Ministry of Oil & Gas of the Sultanate of Oman for the<br>continuous support to the work.