--> Abstract: The Usefulness of Light Hydrocarbons in Classifying Oman Oils, by Mohamed R. Al Ghammari and Paul N. Taylor; #90105 (2010)

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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

The Usefulness of Light Hydrocarbons in Classifying Oman Oils

Mohamed R. Al Ghammari1; Paul N. Taylor1

(1) Exploration, PDO, Muscat, Oman.

In order to improve the understanding of the origin of light oils, which have low biomarker concentrations, Petroleum Development Oman (PDO) developed a new classification tool based on the distribution of light hydrocarbons (LHC). This tool proved useful for identifying mixing patterns between light oil/condensate and normal medium and low gravity oils. The database for this study consists of 71 non-biodegraded normal oil/condensate samples from various oil families and sub-oil families of Oman. All oils/condensates were first classified using C15+ compositions. Various plots and parameters based on light hydrocarbons composition (LHC) were collected from literature and used in this study. It is found that the published LHC parameters are very useful tools in classifying Oman oils (e.g. Schaefer parameters, Halpern correlation parameters). In addition to the published parameters, Principal Component Analysis was performed on these samples using the C7 composition (22DMP through to Toluene). Two useful parameters were successfully extracted from the statistical evaluation that can distinguish between various oil families. These are Total DMCPs/n-C7 and (22DMP+24DMP+11DMCP)/ECP.

Most of the LHC parameters were able to distinguish between four oil families; Huqf, Athel, Q and Mesozoic (Natih+Tuwaiq) oil families. Each oil family is characterised by a unique LHC distribution. Huqf oils are generally characterised by higher paraffins and lower cycloalkanes than the rest of the oil families. Q oils are characterised by higher branched alkanes than the rest of the oil families. Mesozoic oils (Natih+Tuwaiq) are characterised by higher cycloalkanes than Huqf and Q oils. Apparently, most of the Natih oils have Tuwaiq input and no single oil sample has been found for pure Natih oil. Therefore, most of the plots cluster them together. However, one parameter 22DMP+24DMP+11DMCP/ECP was found to be able to tentatively distinguish between the two oils, Tuwaiq pure oils and Natih/Tuwaiq mixed oils. Both Natih and Tuwaiq oils are characterised by higher cycloalkanes than Huqf and Q oils. Only one sample of apparently pure Silurian ‘Safiq’ oil was available for C7 composition. The composition of this oil was different from the published characteristics of Silurian oils elsewhere in Arabia. We are not able to determine whether our single oil sample is representative for Silurian oils in Oman.