Integrated Characterization of UAE Outcrops: From Rocks to Fluid Flow Simulation

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper describes a systematic and logical workflow for characterizing a UAE outcrop of the Upper Thamama reservoir.This integrated workflow uses sequence stratigraphy, geologic modeling, and fluid flow simulation and was used as a tool for training early-career UAE geoscientists and engineers. Although the primary focus of the paper is on the mechanics of geologic modeling with principles applicable to UAE fields, the integrated workflow covers the entire spectrum from rock characterization all the way to flow simulation.Outcrop analogs are a valuable source of data for reservoir characterization. They are particularly useful for visualizing interwell variability because subsurface wellbores represent discrete widely spaced data. In other words, outcrops provide the continuous, large-scale coverage of a seismic line and provide the fine-scale resolution of core measurements. Modeling input parameters such as lateral and vertical continuity (variogram range), object dimensions (aspect ratios), detailed reservoir architecture (layering), facies relationships, and the nature and extent of diagenetic features can be observed and measured.To better understand reservoir properties of the Upper Thamama producing zones in Abu Dhabi, a geologic model was developed from descriptions of time-equivalent, analogous outcrops in the Emirate of Ras Al-Khaimah. Parasequences, maximum flooding surfaces, sequence boundaries and lithofacies were described in four measured sections. Porosity measurements derived from logs, core porosity, and core permeability data from an Abu Dhabi oil field were applied to similar lithofacies observed in outcrop. These subsurface data were used in the outcrop 3D model to more precisely reflect subsurface reservoir behavior because outcrops in the UAE experienced a significantly different burial history relative to the subsurface reservoirs. 1For the stratigraphic interval studied in outcrop (i.e., Upper and Lower Kharaib Formation), four composite reservoir facies (three permeable and one "dense") adequately described the flow behavior. These reservoir facies were modeled using Petrel 2 software and were scaled up into a simulation model using ExxonMobil's next generation reservoir simulator, EM power .™ ,3 Multiple scenarios, including various injection patterns, scaleup methods, and locations of thin, highpermeability streaks, were investigated. Results mimicked known behavior in analogous producing fields and the process of going from rock data to simulation provided a useful training tool for reservoir characterization methods and techniques.

High-Resolution Sequence Stratigraphy of the Kharaib Formation (Lower Cretaceous, U.A.E.)

“…Outcrops of the Kharaib formation at Wadi Rahabah are of seismic scale and thus provide field-scale cross-sections that help to refine sequence stratigraphic and facies models, and aid to the understanding of reservoir geometry distribution, and reservoir continuity in the subsurface 28 . Outcrops are particularly useful for "filling the holes" common in subsurface well data sets used as input to geologic models.…”

“…They occur systematically in specific systems tracts of the third-order composite sequences 4,5,28 . The depositional environments do not occur randomly in time and space.…”

Inter-Well Scale Sedimentological Heterogeneities And Facies Architecture Of Upper Jurassic Carbonate Reservoir And Anhydrite Seals: Lessons Learned Using Outcrop Analogues

“…For example, modern sabkhas along mainland coastal regions are very complex (Kinsman & Park 1976), and meter-scale evaporites and carbonates sequences, with contrasting petrophysical properties, frequently occur together and show lateral facies inter-fingering (Alsharhan & Kendall 2003). Small-scale quantitative data on geobodies dimensions in carbonate analogues are rare (Aigner et al, 2007), although recent constraints starts to emerge for the Jurassic of Morocco Christ et al, 2011), from Spain (Alnazghah et al, 2013), the Permian and Triassic of Oman and the United Arab Emirates (Zeller et al, 2011;Ahmadzamri et al, 2014, Hönig andJohn, 2015) and from Cretaceous outcrops in Oman (Immenhauser et al, 2004;Vaughan et al, 2004;Sattler et al, 2005;Grélaud et al, 2006;2010;Rameil et al 2010;Adams et al, 2011;John, 2013, Sena et al, 2014). The geometric data obtained in these previous outcrop studies can be contradictory, sometimes showing a 'layer-cake' type architecture where pinch out and facies heterogeneities are rare (e.g.…”