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Lanteaume, Cyprien (Total) | Massonnat, Gérard (Total) | Samson, Philippe (Total) | Léonide, Philippe (Aix Marseille University CEREGE) | Borgomano, Jean (Aix Marseille University CEREGE) | Rebelle, Michel (Total) | Michel, Julien (Modis) | Danquigny, Charles (Avignon University UMR EMMAH / Total)
Typical carbonate reservoir modelling workflow usually requires the definition of a carbonate facies model. It generally consists of a conceptual model that drives the successive stages of populating reservoir models. Intuitively, the process of defining a facies model helps to understand and master carbonate reservoir heterogeneity at all scales. This convenient approach reduces the obvious complexity of carbonate reservoirs. It also supports many scientific and technical activities from stratigraphic well correlation, sedimentology, petrophysical interpretation, identification of key dynamic features and assessment of uncertainties to be captured in numerical reservoir models. In practice, facies models bridge the gap between natural processes (sedimentology, diagenesis) and rock properties at reservoir scale and deliver the elementary bricks for the numerical reservoir models. However, such conceptual models mostly derive from scattered observation data (few wells with cored intervals) rarely supported by physical measurement. This limitation induces significant uncertainties in the definition of sediment profiles, depending on the scale and the concepts used. All models produced are the result of extrapolations and interpretations, from cores data which do not sample the whole space of sedimentation.
The interdisciplinary ALBION R&D project aims at studying Urgonian carbonate formation from south-east France, known as a famous analogue of Kharaib & Shuaiba Middle East reservoirs (both of Barremian-Aptian age). The quality of the numerous outcrops, the completeness of the available material (e.g. cores, rock samples, thin sections, various and advanced analyses) and the importance of the published bibliography allowed to define a complete and synthetic facies model to be compared with the ones of Kharaib and Shuaiba formations from the United Arab Emirates. The workflow implemented to realize the facies model on the Urgonian and the Kharaib - Shuaiba formations takes place in four stages: 1) Comprehensive synthesis of the literature; 2) Consistency and ranking of the available data; 3) Creation of the table and facies models; 4) Definition of parameters controlling the occurrence of facies association (e.g. bathymetry, energy). This innovative workflow enforces the coherency between the definition of each facies and the facies association populated in the numerical reservoir model. It makes also possible/easier the comparison between different facies models. These new facies models are embedded within a carbonate infrastructure ranging from the carbonate system (carbonate factory) to the facies of deposits. Facies are characterized by physical quantities such as bathymetry and energy (controlling processes). The construction of these two facies models (representing both sides of the Neo Tethys) drives the definition of numerical modeling rules shared by the two sectors. It opens important perspectives to testing process based and geostatistical numerical modeling methods on the Urgonian outcrop to better control stratigraphic architecture, facies organization in carbonate production prior to applying ascertained modeling rules to Middle East subsurface reservoirs.
Abstract The ALBION project applies a new and disruptive methodology of reservoir characterisation to the carbonate Urgonian Formation (South-East France) considered as the very best analogue of Mid Cretaceous reservoirs from Middle East. Thanks to numerous field sections and outcrops descriptions, to tens of wells drilled in the reservoir, to kilometres of cores, to monitoring of groundwater dynamics such as decades of hydraulic observations at pretty much the only natural outlet of a major groundwater reservoir (Fontaine-de-Vaucluse spring) and to a unique underground laboratory (LSBB, about four kilometers in the heart of the reservoir), a multi-scale model is being built for reservoir purpose. Different observation sites with wells whose spacing ranges from 2 to 20 meters contribute to the assessment of together the matrix, the fractures and the karst flow behaviours. Through the building of an observatory in the heart of a reservoir, the ALBION project is delivering advanced concepts and methodologies to apply to industrial projects in Middle East carbonate fields.
Abstract In carbonates, predicting permeability values for gridded reservoir models is very challenging as it involves both the difficult characterization of a very heterogeneous medium, the uncertain extrapolation far from well data, and the up-scaling concern. The quantification of effective permeability for model gridblocks using small scale data from plug measurements or log interpretation is a recurrent concern since the change of support for permeability has proved to be definitively non linear. When a well test interpretation is available, it gives the evolution of the permeability in the vicinity of the wells for a volume much larger than the volumes characterized by cores and logs. In that case, the consistency has to be found between the transient pressure analysis-derived large scale equivalent permeability and the small scale permeability issued from conventional core analysis or log interpretation. It is known that the upscaling can be expressed as some power average of the permeability distribution, and that an analytical formula relates the horizontal permeability in the volume investigated by the well test and the original small-scale permeability distribution in this volume. However, the relation between the upscaling law and the permeability structures is usually documented for a few number of structures, leading to recurrent problems when large scale permeability has to be extrapolated outside the volume explored by the well test. A new formulation of the power averaging coefficient has been proposed, which relates the power averaging coefficient to the geostatistical description of the permeability structures, the direction of the flow, and the volume for which the equivalent permeability is computed. The new methodology has been applied to the Buissonniere field laboratory, a site from the ALBION R&D Project. Thanks to a characterization at an unusual scale, the integration of geological, petrophysical, geophysical and pressure transient data has successfully validated the use of this new formulation.
Abstract In carbonates, the geological facies is a key driver for populating reservoir models with petrophysical properties. Conventionnal core analysis mainly contributes to establish relationships between facies, petrophysics and geophysics. However, populating gridblocks reservoir models with petrophysics requires parsimonious facies classifications and effective relationships at larger scales that field studies rarely investigate. Studying outcrop analogues helps filling the gap between lab measurements and effective upscaled properties of models, and considerably improves the modelling workflows. The ALBION R&D project developed an innovative framework for multi-physics and multi-scales characterization of Barremian-Aptian carbonates from south-eastern France. These outcropping rudist-rich limestones constitute an analogue of Middle-East reservoirs. Petrophysical and geophysical properties were measured on plugs from cores and outcrops but also at larger scales thanks to original experiments on cores, in and between boreholes. Indeed the analogue includes several experimental areas, where hydraulic tests in sealed wells sections and tomographies between very close boreholes allowed investigating petrophysical and geophysical rock properties at intermediate decimetric to decametric scales. Thanks to the resulting database, this paper aims quantifying the variability of multi-physics data (e.g. porosity, permeability, and P-wave velocity) at different scales in regards of an updated and unified facies classification. The latter is only based on sedimentary origin and fabrics. Other available properties affecting petrophysics are used to cluster facies associations in sub-classes. Consequently the facies classification does not allow discriminating the distributions of porosity, permeability, nor p-wave velocity. For the rudist facies, that is the most sampled, texture subclasses do not help this work. Reversely, the place of sampling, that is likely a proxy of diagenesis and age, cluster the petrophysical distributions. The results remind us that a proper facies definition should consider both sedimentary origin, fabrics, texture, diagenesis and tectonics. They also point out the relative importance of each characteristics in regards of the scale of interest and the difficulty to infer upscaled relationships between rock properties from CCAL because the representative elementary volume of carbonates is usually higher than the plug and even the core volumes.
Abstract This paper explores some of the most innovative building blocks of the 3D modeling workflow used in carbonate reservoirs to deal with their natural complexity. Based on real published cases, different methodologies are presented. Stratigraphic forward modeling can capture specific carbonate geometries, i.e. clinoforms, rudistid build-ups, incisions, tidal channels of Shuaiba and Mishrif platforms, and help predicting subtle traps. The role of 3D seismic, specifically through stochastic impedance inversion is highlighted to detect depositional heterogeneities in the Mishrif. Another Mishrif example shows porosity prediction from post-stack impedance inversion and feedback loops between synthetic versus original seismic data and between synthetic seismic versus the reservoir model. Recent breakthrough is achieved with a 4D seismic pilot acquired over a carbonate field with a long producing history. 2G&R interpretation (including fluid and dynamic constraints) integrates 4D in-house warping processing. Then the paper focuses on the tracking of dolomitic bodies, such as in the Khuff or the Arab formations. It is first based on the identification of their origin at wells, by petrography, geochemistry and sedimentology. Dolomitic bodies are then propagated in 3D with the constraint of seismic data. Probability cubes of dolostones versus limestones are derived from classification of multi-realization stochastic impedance inversion. These cubes are directly compatible with the geomodel grid. The spatial and petrophysical distribution of the early to late dolomitic overprints can be simulated with process-based and object-based methods. This paper ends with a comprehensive 2G&R integration capturing heterogeneities which impact the development plan. The complex faulted Cretaceous reservoir taken as example has large matrix permeability contrasts linked to facies and diagenesis and is baffled by continuous dense zones and tar mats. To avoid any time-consuming numerical upscaling between geological and simulation grids, the same grid was built for the two models allowing quick feedback iterations during the history matching and further model updates. Thanks to high performance (HPC) computing technology, new simulation opportunity opens the floor to Giga cell dynamic models at very fine resolution. These HPC based simulations are well adapted to the Middle East giant carbonate fields.