--> Rock-Typing: An Integrated Reservoir Characterization Tool for Tight Najmah Sargelu Formation in Dharif Abduliyah Oil Field, West Kuwait
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Rock-Typing: An Integrated Reservoir Characterization Tool for Tight Najmah Sargelu Formation in Dharif Abduliyah Oil Field, West Kuwait

Abstract

Middle Jurassic tight fractured Najmah-Sargelu Formation is spread across whole Kuwait. It is often vertically and laterally heterogeneous because of depositional variability and diagenetic alteration through space and time. Understanding the distribution of hydrocarbons in relation with porosity / permeability heterogeneities is thus of major importance in effective field development and production. Rock-typing is then an essential step in Carbonate reservoir characterization and geological model building for reservoir simulation and predicting fluid flows through time in order to support development scenarios. A static rock-type is defined as “a rock unit characterized by similar depositional and diagenetic processes resulting in a typical and unique ø-K relationship and capillary pressure curve at given wettability”. This paper establishes a deterministic rock-type scheme in Najmah-Sargelu reservoir and presents a methodology to distribute these rock types vertically and laterally in the 3D geological model. In the present study, a total of 27 wells were analyzed. The rock-types are based on core observation of the main sedimentary facies, dynamic properties measured in special and conventional core analyses and logs. This approach reconciles sedimentology, petrophysics and dynamic characteristics of rocks. This also allows identifying the rock-types in non-cored intervals. During the electrofacies analysis, both non-supervised and supervised approaches were carried out successively, the first one to characterize electrofacies on reference cored wells, and the second one to propagate this signature to other wells once the comparison with lithofacies is positive. Once the electrofacies were interpreted and propagated, they were tied to available petrophysical information, in order to build the rock-types. A rock-type can gather several electrofacies if their dynamic behavior is similar; conversely, electrofacies must be refined if it appears that their group points have no consistent petrophysical characteristics. In this study, Najmah and Sargelu formations were treated separately due to strong impact of bitumen in the formation which reduces the weight of other facies and a total of 10 rock-types (5 in Najmah and 5 in Sargelu) have been defined. These rock-type results have been exported and are available for use in stratigraphy and static geological modelling of the reservoir (3D geological model).