Publications
67 results found
Jacquemyn C, Melnikova Y, Jackson MD, et al., 2016, Geologic modelling using parametric NURBS surfaces
Most reservoir modelling/simulation workflows represent geological heterogeneity on a pillar-grid defined early in the modelling process. However, it is challenging to represent many common geological features using pillar grids: Examples include intersecting faults, recumbent folds, slumps, and non-monotonic injection structures such as salt diapirs. It is also challenging to represent multi-scale features, because the same number of pillars must be present in all layers so there is little flexibility to adjust the areal grid resolution. We present a surface-based geological modelling (SBGM) workflow that uses NURBS (Non-Uniform Rational B-Splines) surfaces to represent geological heterogeneities without reference to a pre-defined grid. The NURBS surfaces represent a broad range of heterogeneity types, including faults, fractures, stratigraphic surfaces across a range of length-scales, and boundaries between different facies or lithologies. The geological model is constructed using the NURBS surfaces and a mesh created only when required for flow simulation or other calculations. The mesh preserves the geometry of the modelled surfaces. NURBS surfaces are an efficient and flexible tool to model complex geometries and are common in many modelling and engineering disciplines; however, they are rarely used in reservoir modelling. Complex surfaces can be created using a small number of control points; modelling with NURBS surfaces is therefore computationally efficient. We report here a variety of new stochastic approaches to create geological NURBS surfaces, including (1) extrusion of spatially variable cross-sections, (2) parametric 3D geometry templates, and (3) perturbation of control points to yield similar results to some pixel-based geostatistical methods. Surface interactions, such as erosion, stacking or conforming, are enforced to ensure geological relationships are preserved and the boundary representation is watertight. We illustrate our NURBS SBGM approach
Jones RR, Pearce MA, Jacquemyn C, et al., 2015, Robust best-fit planes from geospatial data., Geosphere, Vol: 12, Pages: 196-202, ISSN: 1553-040X
Total least squares regression is a reliable and efficient way to analyse the geometry of a best-fit plane through georeferenced data points. The suitability of the input data, and the goodness of fit of the data points to the best-fit plane are considered in terms of their dimensionality, and quantified using two parameters involving the minimum and intermediate eigenvalues from the regression, as well as the spatial precision of the data.
Jacquemyn C, Jackson MD, Hampson GJ, et al., 2015, Geometry, spatial arrangement, and connectivity of grain-dominated, storm-event deposits in outcrop analogue of Late Jurassic Arab‐D reservoir, Saudi Arabia., AAPG ACE
The Late Jurassic Arab-D reservoir, composed of the Arab-D Member of the Arab Formation and upper part of the underlying Jubaila Formation, is highly prolific in several supergiant oil and gas fields in the Middle East. An outcrop analogue of equivalent age in central Saudi Arabia shows depositional facies and stratigraphic architecture that are similar to those inferred in the subsurface. This analogue has been studied using a high-resolution digital outcrop model integrated with measured sections, in order to understand and quantify facies relationships in storm-dominated, shallow-marine carbonates. Outcrops of the lower to middle Arab-D reservoir reveal a succession of interbedded muddy and grainy rocks that occur as a series of thin (0.5–1 m) fining-upward cycles. Cycles typically comprise a coarse-grained grainstone-to-rudstone lower part that contains muddy intraclasts and, locally, stromatoporoid and coral fragments, which fines upward into a wackestone cap. The finer portions of these cycles are bioturbated, and swaley cross-stratification occurs locally in both mud- and grain-dominated beds. Cycles are separated by sharp-to-erosional bases of varying relief, which cause cycle thickness to vary laterally. Locally, 1–3 m thick chaotically bedded conglomeratic intervals containing overturned stromatoporoid and coral clasts up to 1 m in diameter infill scours with steep-to-vertical walls that incise several meters into underlying deposits. The fining-upward cycles are interpreted to result from storm events that locally scoured and reworked sediments. The occurrence of swaley cross-stratification suggests deposition below fair weather wave base but above storm wave base. Larger storm events produced steep-sided scours that were filled by conglomeratic debris transported offshore from shallower water settings. Storm-event deposits vary laterally and vertically in their geometry, spacing and connectivity. Few coarse-grained beds extend across outcrop
Jacquemyn C, Huysmans M, Hunt D, et al., 2015, Multi-scale 3D distribution of fracture- and igneous intrusion- controlled hydrothermal dolomite from digital outcrop model, Latemar platform, Dolomites, northern Italy, AAPG Bulletin, Vol: 99, Pages: 957-984, ISSN: 0149-1423
In recent years, fracture-controlled (hydrothermal) dolomitization in association to igneous activity has gained interest in hydrocarbon exploration. The geometry and distribution of dolomite bodies in this setting are of major importance for these new plays. The Latemar platform presents a spectacularly exposed outcrop analogue for carbonate reservoirs affected by igneous activity and dolomitization.LiDAR scanning and digital outcrop models (DOM) of outcrops offer a great opportunity to derive geometrical information. Only few analysis methods exist to quantitatively assess huge amounts of georeferenced 3D lithology data. This study presents a novel quantitative approach to describe 3D spatial variation of lithology derived from DOMs. This approach is applied to the Latemar platform to determine dolomite body geometry and distribution in relation to crosscutting dikes.A high-resolution photorealistic DOM of the Latemar platform allows description of dolomite occurrences in three dimensions, with high precision on platform-scale. This results in a unique lithology dataset of limestone, dolomite and dike positions. This dataset is analysed by true 3D variography for the geospatial description of dolomite distribution. In most studies, 3D geostatistics is the combination of 2D horizontal and 1D vertical variation. In this study the dolomite occurrences are extensive in 3D and cannot be reduced to a 2D+1D case. Therefore the concept of 2D variogram maps is expanded to a 3D description of lithology variation. 3D anisotropy detection is used to derive principal directions in the occurrence of dolomite. Two small-scale (<200 m) anisotropy directions emerge, one vertical and one subhorizontal, that describe the geometry of the dolomite bodies. These principal directions are perfectly aligned parallel to the average dike orientation. On platform-scale (200-1600 m) a bedding-parallel anisotropy direction indicates stratigraphic control on dolomite occurrences.
Jacquemyn C, El Desouky H, Hunt D, et al., 2014, Dolomitization of the Latemar platform: Fluid flow and dolomite evolution, Marine and Petroleum Geology, Vol: 55, Pages: 43-67, ISSN: 0264-8172
The Anisian-Ladinian Latemar platform, northern Italy, presents a spectacularly exposed outcrop analogue for dolomitized carbonate reservoirs in relation to fracture-controlled igneous intrusions. Although the Latemar is one of the best studied carbonate platforms worldwide, timing and evolution of dolomitization and the link to fractures and dikes have not been explored in detail. Previous dolomite observations are based on a stratigraphically limited portion of the platform. This study extends observations to the complete exposed interval in which dolomite bodies occur, including those within the less accessible Valsorda valley. Numerous parallel mafic dikes crosscut the Latemar platform and border several of its large dolomite bodies (50m wide, 100m high). Within dikes and along dike-carbonate contacts, there are abundant dolomite veins that are geochemically related to surrounding dolomite bodies. Dolomitization is the result of limestone interaction with hydrothermal fluids delivered along these dikes. At dike boundaries, impermeable marble aureoles exist derived from contact metamorphism. The marble aureoles have locally shielded surrounding limestone from dolomitizing fluid. Dolomite occurs only where the 'protective' marble is missing or crosscut by fractures. Based on geometric relationships, we conclude that dikes and their damage zones formed the pathways for the dolomitizing fluids and functioned as boundaries for dolomite bodies.From field observations and petrography, we established a detailed paragenesis. Dolomitization started shortly after dike emplacement. There is an evolution in the Fe content of matrix dolomite and dolomite veins, from highly ferroan dolomite to non-ferroan (saddle) dolomite, alternating with episodes of silica cementation. Non-ferroan calcite precipitation followed dolomitization, possibly indicating concurrent depletion in Mg. This stage likely resulted in further limestone recrystallization rather than dolomitization. Stable
Jacquemyn C, Swennen R, Ronchi P, 2012, Mechanical stratigraphy and (palaeo-) karstification of the Murge area (Apulia, southern Italy), Geological Society, London, Special Publications, Vol: 370, Pages: 169-186, ISSN: 0305-8719
The Cretaceous Apulia Platform, exposed in the Murge area (southern Italy), sufferedintense (palaeo)karstification. This study focuses on the controlling factors of karstification with emphasis on fracturing. Mechanical stratigraphy was used to calculate the fracture density within different sedimentary sequences. Several mechanical units were defined and a characteristic relationship was found between unit thicknesses and fracture density, that is, fracture density increases if layer thickness decreases. In some of the quarries studied, sedimentary cycles are clearly present that are also reflected in the fracture density logs. The degree of karstification within a mechanical unit is proportional to the mean fracture spacing. Based on fracture orientation data extracted from LIDAR scans, different orientation clusters were observed between fractures that are karstified and fractures that are not karstified, post-dating karstification. The clusters of karstified fractures are related to the compression of the southern Apennines. The fractures became dissolution enlarged during the Pleistocene uplift caused by bulging of the Apulia Platform. This main karstification phase occurred prior to Late-Pleistocene deposition and before the formation of orthogonal fracture sets.
Jacquemyn C, Swennen R, Ronchi P, 2009, (Paleo-)Karstification in the Apulia region (Southern Italy): influence of sedimentology, diagenesis and mechanical stratigraphy, 27th IAS Meeting of Sedimentology, Publisher: MEDIMOND S R L, Pages: 141-146
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