Compositional Modeling of Northern Kuwait Jurassic Hydrocarbons for GOR and API Prediction

Awatif F. Al-Khamiss¹*, Frederic Monnier², and Pierre Y. Chenet^2
1KOC
²Beicip-Franlab, France
*[email protected]

The prediction of fluid properties in reservoirs prior to drilling is important for new prospective areas in order to reduce exploration risk and to estimate petroleum resources. Compositional modelling studies involving Temim 2-D and 3-D software have been carried-out with the objective to predict hydrocarbon composition and properties, and to quantify resources of various reservoirs within the Jurassic succession of northern Kuwait.

The Temis 3-D block of northern Kuwait was derived from a previous block developed for a regional study and updated with new structural maps covering a large area including Bahrah, Dhabi, Sabiriyah, Umm-Niqa, Raudhatain and NW Raudhatain. 2-D models were constructed for calibrating the Najmah source kinetics against API gravity and GOR (gas/oil ratio) and oil chemical composition on known accumulations. Temis 2-D was then used to predict hydrocarbon fluid properties potentially accumulated in Jurassic reservoirs under supercritical PVT (pressure-volume-temperature) conditions. In-place resource estimates were derived from map-based Temis 3-D. In the Cretaceous reservoirs the oil’s API gravity ranges between 30° and 34° and the GOR is relatively low. In contrast the oil in the Upper Jurassic (Najmah, Sargelu and Marrat) reservoirs has an API gravity greater than 45° and high GOR (greater than 5,000 standard cubic ft/barrel). These differences are explained by a model in which the early generated Najmah-sourced oil migrated into the Cretaceous reservoirs through the faulted Gotnia Salt. More mature oil, expelled later from the Najmah source rock, remained trapped in the Upper Jurassic, where it underwent secondary cracking affecting mainly the aromatic and nitrogen, sulfur and oxygen fractions. The Najmah and Sargelu reservoirs rapidly reached hydrocarbon saturation due to their relatively low-storage capacity. The surplus of hydrocarbons spilled downward into the Marrat Reservoir, particularly the Middle Marrat, and occasionally down to the Lower Marrat.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain