Modeling Hydrocarbon Generation, Migration and Entrapment in Northern Oman

Reid, Stephen A.¹, Badar H. Al Barwani², William M. Fitchen³ (1) Occidental of Oman, Inc, Houston, TX (2) Occidental of Oman, Inc, Muscat, Oman (3) Occidental Mukhaizna LLC, Muscat, Oman

Ongoing basin modeling studies in Blocks 9 and 27 in northern Oman support previous interpretations of oil derived from three principal source rock intervals: Precambrian-Cambrian Huqf, Jurassic Tuwaiq and Cretaceous Natih. To model the maturation, migration and entrapment of hydrocarbons from the source intervals, a regional 3D basin model was built. The 3D geocellular structural model incorporates about 350 wells with seismic horizons from ten 3D seismic surveys and several thousand kilometers of 2D data. Geochemical analyses of over 100 crude oil samples are used to help define source intervals, hydrocarbon migration paths and entrapment timing. The study area includes the Lekhwair Arch, the Suneinah Foredeep, and the northern Fahud Salt basin.

Modeling results indicate that the Huqf oil present in the Lower Cretaceous Shuaiba reservoirs was possibly generated before the end of the Paleozoic, but did not migrate into the Shuaiba until middle Tertiary. Huqf oil likely was generated in local basins, and migrated vertically along faults during tectonic events. Tuwaiq oil was generated in a downdip location along the east or north edge of the model area, and migrated into the Shuaiba following a middle Cenozoic tectonic event. Natih oil was generated in a downdip area located in the Suneinah Foredeep, and migrated along bedding into updip Natih reservoirs beginning in the Miocene. Modeling indicates gas was derived from the cracking of residual Huqf oil in deeper, breached traps, or migrated laterally from the Jurassic source area.