Reliable Geological Model Research Articles

New constraints from in-situ U-Pb ages and fluid inclusions of calcite cement and structural analysis on multiple stages of strike-slip fault activities in the northern Tarim Basin, NW China

Dating the activity of complex faults and fracture systems is crucial for creating reliable geological models for various tectonics and subsurface engineering applications. This study presents a comprehensive study integrating U–Pb fracture cement dating, trace elements, and fluid inclusion temperature analysis with seismic analysis of faults, fault diagenesis, and burial history studies to better constrain faulting and fracture activities in an intra-cratonic strike-slip fault system in the northern Tarim Basin. Seismic profiles indicate at least three distinct phases of fault activity corresponding to the Middle Ordovician, Permian, and Paleogene periods. Fracture cementation and crosscutting relationships corroborate the identification of three fracturing stages. U–Pb dating of fractured cement has widely detected Middle Ordovician and Early Permian age intervals. Fluid inclusion homogenization temperatures from the fractured cements, ranging across < 50 °C, 70–130 °C, and 150–180 °C, correspond to three episodes of rapid subsidence during the Ordovician, Permian, and Neogene, respectively. These results suggest three phases of fault/fracture reactivation in the Middle Ordovician (prior to 470 Ma), Early Permian (prior to 295 Ma), and Cenozoic. The fault/fracture reactivation in the Ordovician is closely related to the regional tectonic transition from extension to compression, while fault and fracture reactivation in the Early Permian may be related to hydrothermal activity associated with large-scale igneous province and oil emplacement. Fault/fracture activity in the Cenozoic may be related to a reduction in subsidence, gradual reduction of geothermal gradients, and massive oil emplacement. This research underscores the significance of integrating geochemical and subsurface datasets for accurately determining the timing of faulting and fracturing in sedimentary basins.

Quantitative analysis of the numerical simulation uncertainties from geological models in CO2 geological storage: A case study of Shenhua CCS project

The intensifying global climate change has prompted the imperative implementation of CO2 capture and storage (CCS) projects as a mitigation strategy. Ensuring the safety and reliability of these projects requires meticulous validation, including the establishment of geological models and conducting numerical simulations. In CO2 geological storage initiatives, the limitation of well data during the initial stages leads to data deficiency. This scarcity compromises the precision of geological and numerical models, hindering their ability to accurately depict actual subsurface conditions. Meanwhile, parameters related to heterogeneity significantly also impact storage effectiveness and safety. This study addresses these challenges by utilizing the Shenhua CCS demonstration project as a case study. Various heterogeneous parameters are selected, and local and global sensitivity analysis methods are subsequently introduced to determine the ranges and sequences of these parameters in numerical simulations. The simulation results can aid in assessing the influence of various heterogeneous parameters on the CO2 plume and bottom hole pressure. The study establishes the importance ranking of various heterogeneous parameters under different temporal and spatial conditions through sensitivity analysis. The findings reveal the following key points:1. During the small-scale injection period, the CO2 plume is particularly sensitive to variations in net-to-gross and vertical permeable properties.2. During and after larger-scale injections, the net-to-gross significantly impacts plume evolution, while bottom hole pressure is predominantly influenced by variations in vertical permeable properties.3. Both the CO2 plume and well bottom pressure are primarily affected by changes in sand body morphologies, especially at low net-to-gross scenarios.These conclusions assist in prioritizing the collection of critical parameter data in CCS projects, facilitating the establishment of more precise and reliable geological and numerical simulation models. The heightened accuracy and reliability of these models contribute to improving their predictive capabilities, ultimately guiding engineering practices.

Multi-source data integration and multi-scale modeling framework for progressive prediction of complex geological interfaces in tunneling

A reliable geological model plays a fundamental role in the efficiency and safety of mountain tunnel construction. However, regional models based on limited survey data represent macroscopic geological environments but not detailed internal geological characteristics, especially at tunnel portals with complex geological conditions. This paper presents a comprehensive methodological framework for refined modeling of the tunnel surrounding rock and subsequent mechanics analysis, with a particular focus on natural space distortion of hard-soft rock interfaces at tunnel portals. The progressive prediction of geological structures is developed considering multi-source data derived from the tunnel survey and excavation stages. To improve the accuracy of the models, a novel modeling method is proposed to integrate multi-source and multi-scale data based on data extraction and potential field interpolation. Finally, a regional-scale model and an engineering-scale model are built, providing a clear insight into geological phenomena and supporting numerical calculation. In addition, the proposed framework is applied to a case study, the Long-tou mountain tunnel project in Guangzhou, China, where the dominant rock type is granite. The results show that the data integration and modeling methods effectively improve model structure refinement. The improved model's calculation deviation is reduced by about 10% to 20% in the mechanical analysis. This study contributes to revealing the complex geological environment with singular interfaces and promoting the safety and performance of mountain tunneling.

Seismic forward modeling for investigating and interpreting thin beds in a carbonate reservoir in SW Iran

High-frequency contents of reflections are essential in the investigation and interpretation of thin-bed reservoirs. These beds can be even more complicated in carbonate rocks, as pore geometries influence final seismic responses. To address these complexities, we propose a seismic forward modeling workflow to investigate several thin-bed reservoirs in a carbonate oilfield with variable pore geometries. The new workflow enhances the existing forward models for the investigation of thin beds by integrating seismic petrophysics, geological model building, and 2D finite-difference elastic modeling. We used seismic petrophysics to ensure the consistency between petrophysical well logs and seismic data using rock physics modeling. Then, we introduced a new high-resolution workflow for velocity modeling to build a reliable geological model. Finally, the 2D finite-difference elastic modeling is employed to generate synthetic traces based on our geological model to obtain seismic responses for the existing thin-bed reservoirs. The forward models used in this study are a powerful tool for investigating thin layers because they enable high-resolution investigation of the given geological model in distinguishing lateral and vertical lithofacies changes. The new velocity modeling workflow, implemented in this research, is more reliable and effective than the conventional velocity property modeling approaches, which resulted in synthetic seismic sections with increased lateral and vertical resolutions and enhanced data from a thin bed. The main features of this workflow are the incorporation of well-log data into geological model building, combining the high-resolution data of horizontal seismic stacking velocity with vertical well logging, and the incorporation of a residual model to improve the seismic stacking velocity. We produced a more coherent section resembling the acquired 3D seismic data by applying the proposed workflow to data from an oil carbonate reservoir in the Fahliyan Formation within the Abadan Plain in SW Iran. It is concluded that the higher frequency synthetic sections from the proposed workflow can assist in resolving the seismic interpretation challenges. By applying the proposed workflow to the current data set, four thin-bed carbonate reservoirs were investigated with corresponding thicknesses of approximately 25, and 17 m at peak frequencies of 60, and 90 Hz, respectively.

Crosshole Ground‐Penetrating Radar in Clay‐Rich Quaternary Deposits: Toward Characterization of High‐Loss Media

AbstractKnowing the centimeter‐to meter‐scale distribution of sand in clayey deposits is important for determining the dominating water flow pathways. Borehole information has a high vertical resolution, on the millimeter‐ to centimeter‐scale, but provides poor lateral coverage. For highly heterogeneous deposits, such as glacial diamicts, this detailed borehole information may not be sufficient for creating reliable geological models. Crosshole ground‐penetrating radar (GPR) can provide information on the decimeter‐ to meter‐scale variation between boreholes, but has mainly been used in sandy environments. In this study, we investigate whether crosshole GPR can provide information on the structural relationship of diamicts and their material properties, such as water content, bulk density, and clay content. To achieve ground truth, we compare the crosshole GPR data with geological information from boreholes and an excavation at the field site. The GPR data was analyzed comprehensively using several radar wave attributes in both time‐ and frequency domain, describing the signal velocity, strength, and shape. We found small variations in signal velocity (between 0.06 and 0.07 m/ns) but large variations in both amplitude and shape (either order of magnitude variation or doubling/tripling of attribute values). We see that the GPR response from wetter and more clayey diamicts have both lower amplitudes and lower centroid frequencies than the response from their drier and sandier counterparts. Lastly, we find that the variation in amplitude and shape attributes is better correlated to the diamicts' material properties than the signal velocity.

X-ray fluorescence (XRF) fingerprinting of Palaeogene deposits in Denmark

In this study, we test if cost-efficient X-ray fluorescence (XRF) analyses can be used to fingerprint Palaeogene clay and marl deposits in Denmark. A total of 67 samples from key sites in Denmark have been analysed. Our preliminary results indicate that it is possible locally within 10–30 km to distinguish between most of the Palaeogene units, but on a regional scale across Denmark, the units are not unique, and this probably reflects variations in clay mineralogy, grain size and calcareous content. Accordingly, we suggest that a comprehensive reference database is now needed if the full potential of the method is to be utilised, and this will ultimately result in more reliable geological models.

Deep Conditional Generative Adversarial Network Combined With Data‐Space Inversion for Estimation of High‐Dimensional Uncertain Geological Parameters

AbstractInverse modeling can provide a reliable geological model for subsurface flow numerical simulation, which is a challenging issue that requires calibration of the uncertain parameters of the geological model to establish an acceptable match between simulation data and observation data. The general inverse modeling method needs to iteratively adjust the uncertain parameters, which is a difficult and time‐consuming high‐dimensional sampling problem. To address this problem, we propose a deep‐learning‐based inverse modeling method called pix2pixGAN‐DSI. In this method, the deep‐learning‐based image‐to‐image generative adversarial network (pix2pixGAN) is constructed to directly predict the posterior parameter fields from the posterior dynamic responses obtained by the data‐space inversion (DSI) method. This inverse modeling method does not need to iteratively adjust the uncertain parameters, which improves computational efficiency. The effectiveness of the proposed method is verified through a Gaussian model case and two non‐Gaussian channelized model cases. Through the analysis of posterior realizations, matching and forecast of production data, and uncertainty quantification, the results show that the proposed method can obtain reasonable estimates without iteration and parameterization.

Definition of the geological structure of deposits of Tyumen suite based on the results of tectonic-sedimentary analysis of the eastern part of the Krasnoleninsky arch of Western Siberia

We present in this article results of an analysis of materials of a complex of geological and geophysical studies, including a description of the core data, facies' characteristics, tectonic features of the evolution of the territory, field development geophysical data. The initial materials for the research were the drilling data and the results of seismic surveys, as well as publications of geologists and geophysicists dealing with the problem of finding ways to increase the efficiency of the development of hard-to-recover reserves of Tyumen suite. The research area is confined to the eastern slope of the Krasnoleninsky arch of Western Siberia, within which several oil fields of various sizes have been identified that are now being actively development.Based on the work carried out on the group of layers of Tyumen suite, areas of distribution of lithofacies of fine-medium-grained and multi-grained sandstones within the forecast area of development of channels and cones of deltas and facies of channel valleys were identified, taking into account the structural factor and isopach maps. The transverse dimensions of the boundaries of the development of riverbed valleys with a very complex configuration range from 0.5 to 2.5 km. The predicted effective sandstone thicknesses of individual strata in areas with improved filtration and capacitive properties reach 12-14 m.The analysis of the geological structure of the deposits of Tyumen suite will serve as an information basis for creating the molds of reliable geological model, based on which, with the help of digital modeling, an assessment of the prospects for further work on the object under study and the search for the necessary methods for its development will be

Improving predictions of solute transport in a laboratory sandbox aquifer through high-resolution characterization with hydraulic tomography

Hydraulic tomography (HT) has been developed over the last two decades to image subsurface heterogeneity at high resolution that is critically important to robust solute transport predictions. In this study, HT based on two concepts (i.e., geological zonation and geostatistical inversion models) was utilized to characterize the K distribution of a laboratory sandbox aquifer at different parameter resolutions. We compared the estimated K fields for predicting independent pumping tests and solute transport using the classical advection–dispersion equation (ADE). The impact of using geological zonation models of varying accuracy for HT analyses was investigated. Results revealed that, when being calibrated to datasets from multiple pumping tests, geological zonation models that faithfully represented the true stratigraphy predicted groundwater flow satisfactorily. The deterministic K field of the calibrated reliable geological zonation models satisfactorily reproduced the preferential migration path of the observed tracer plume, and the breakthrough curves (BTCs) at sampling ports. With further resolving the inter- and intra-layer heterogeneity, the reconstructed K fields by HT better predicted both migrating plumes and BTCs for two conservative tracer tests. The estimated dispersivity values for ADE only resulted in slight improvements in the fitting between observed and simulated solute tracer data. It also demonstrated the need of integrating reliable geological information into the geostatistical inversion approach to reproduce geological structures in K fields. Our study suggested the proper consideration of geological zonation between boreholes during field implementation of HT to yield improved solute transport results.

A proposal for reservoir geostatistical modeling and uncertainty analysis of the Curimã Field, Mundaú Sub-Basin, Ceará Basin, Brazil

Geological modeling represents one of the most important phases in reservoir characterization, in terms of workload, uncertainties and impact on final results. Modeling of oil reservoirs consists of the construction of the structural, stratigraphic, and petrophysical models; the calculation of the volume of oil in place; and the analysis of uncertainties. This study integrates reservoir data obtained from a variety of disciplines (geophysics, petrophysics, sedimentology, geology, and engineering), with the purpose to build a reliable geological reservoir model. To better represent the reservoir heterogeneities and integrate geological concepts and observations, geostatistical principles were applied to geological modeling. Therefore, the main objective of this study is to characterize the geometry and petrophysical properties of the Curimã Field, a deltaic reservoir in the Paracuru Formation of the Mundaú sub-Basin (Ceará Basin), using advanced geostatistics in order to evaluate the uncertainties of the reservoir volume. The integration of reliable data using geostatistical techniques to simulate reservoir properties provided a reliable geological model that matches, in terms of original volume in place, with that published by the Brazilian National Agency of Oil, Natural Gas and Biofuels (ANP). In addition, the sensitivity and uncertainty analysis of the variables used to build the geological model allowed to rank them according to their impact on the volume calculation - thus, from greatest to the lowest impact: i) the porosity cutoff for the NTG calculation; ii) the mean porosity value for sandstones; iii) the depth of water-oil contact. The final results were based on the analysis of 500 simulation runs and generated pessimistic and optimistic probabilistic scenarios (P10, P50, and P90) of the volume in place. These results will aid a detailed dynamic assessment of the exploitation potential of the Curimã Field.

Using geostatistics to generate a geological model of a sandstone petroleum reservoir in southern California

A variogram-based two-point geostatistical approach was applied to generate a geological model of a petroleum reservoir. The geology consists of a sandstone formation with uniformly inclined rock strata of equal dip angle structurally trapped by surrounding faults. Data exploration of electrical well logs using univariate/bivariate statistical tests and data transformation tools demonstrated the data to be statistically suitable for ordinary kriging and sequential Gaussian simulation. Three directions were defined as part of the variogram and the data were interpolated resulting in a 3D subsurface representation. Validation included performing a leave-one-out cross-validation for each well and statistical comparison of multiple realizations generated from a computed stochastic model. The results display a reliable geological model which indicate a direct causation of the continuity trends from the bedding attitude of the regional fault trap.

Detalied magnetotelluric study of the northern part of Subandean fold belt, Bolivia

A detailed magnetotelluric survey was carried out in the northern part of Subandean fold belt, Bolivia, with the main goal of better understanding of the geological structure of the sedimentary basin and petroleum system in the study area. An improvement of magnetotelluric technology was developed aimed at better imaging of resistivity structures in fold belt. A new static shift correction procedure and a new multistage unconstrained and constrained 2D inversion workflow was suggested and successfully implemented. In addition, the original 3D inversion approach was developed and its efficiency for fold belt geological settings was shown.Advances in magnetotelluric technology made it possible to obtain new geological information about the structure of the sedimentary cover in the study area. Two resistivity structural levels differing in resistivity were outlined. The boundary between levels corresponds to the top of the Carboniferous-Devonian formations, which is one the principle detachments in the northern part of Subandean fold belt. The topography of the top of the lower structural level does not correlate with structures in the upper structural level and with structures outlined by surface geology in most of the survey area. A large numbers of fault zones are outlined in the upper structural level, narrow anticlines are characterized by complicated structure (palm-tree structures).Magnetotellurics gives the most reliable position of the buried axes of anticlinal disharmonic folds, which opens up the possibility of constructing more reliable geological models using joint inversion of magnetotelluric data together with other geophysical data, first of all seismic data. Application of magnetotellurics in fold basins as complimentary to 2D seismic geophysical technology gives possibility to increase reliability of geological interpretation.

Applications of Geophysical Logs to Coal Mining—Some Illustrative Examples

Geophysical logs can be used not only for qualitative interpretation such as strata correlation but also for geotechnical assessment through quantitative data analysis. In an emerging digital mining age, such a use of geophysical logs helps to establish reliable geological and geotechnical models, which reduces safety and financial risks due to geological and geotechnical uncertainty for new and existing coal mining projects. This paper presents some examples of geological and geotechnical characterizations from geophysical logs at various coal mines in Australia and India. The applications include rock strength and coal quality estimations, automated lithological/geotechnical interpretation and geophysical strata rating, all based on geophysical logs. These derived parameters could provide input to modelling, control, even ‘digital twin’ generation in a form of geological and geotechnical models as part of the future digital mining. The outcomes can be visualized in 3D space and used for identifying the key geotechnical strata units that are responsible for caving behaviors during longwall mining. This could assist site geologists and planning and production engineers predict and manage mining conditions on an ongoing basis. Both conventional logs such as density, natural gamma and sonic and less common logging data, such as full waveform sonic, televiewer and SIROLOG spectrometric natural gamma logging data are examined for their potential applications. The geotechnical strata classification and rock strengths predicted from the geophysical logs match the laboratory tests, drill core geotechnical strata classification, core photos and the mining condition/behavior observed. These illustrate the usefulness and effectiveness of using geophysical logs for geological and geotechnical characterizations.

Geophysical Techniques for Monitoring Settlement Phenomena Occurring in Reinforced Concrete Buildings

Geophysical investigations could provide a valid tool for the identification of possible causes of settlement phenomena that affect civil buildings. They provide a non-invasive method of obtaining high-resolution information about the subsoil, saving time and money. However, uncertainties related to the accurate interpretation of the acquired data could potentially reduce the value of these methods. For this reason, the integration of non-invasive tests with direct measurements to support geophysical data interpretation is strongly recommended. This is a fundamental step in the process of defining a sufficiently reliable geological model to explain the cause of failure. Among the various geophysical techniques, electrical resistivity tomography and ground penetrating radar offer significant advantages for monitoring the status of the conservation of civil engineering structures and infrastructures. This paper presents the most recent and beneficial advances of the use of electric and electromagnetic geophysical methods in the field of civil engineering, with particular attention to their applications for monitoring subsidence and settlement phenomena. Finally, the possibilities of the joint use of resistivity and electromagnetic methods for studying the causes of the structural decay that affects two precast buildings are monitored and discussed. The results demonstrate the capability of combining non-destructive geophysical techniques with direct data, for evaluating the safety of building constructions and solving geotechnical problems.

Site-specific probabilistic seismic hazard analysis for the western area of Naples, Italy

Probabilistic seismic hazard analysis (PSHA) encompasses quantitative estimation of seismic hazard at a site by considering all plausible earthquake scenarios. The outcome of a PSHA is often reported as the mean rate of exceeding a specific ground motion intensity measure at a given site. This study attempts to perform PSHA for the western area of the city Naples (southern Italy) by employing the most advanced methods and new databases; namely, DISS3.2 (Database of Individual Seismogenic Sources) and CPTI15 (Parametric Catalogue of Italian Earthquakes). Seismogenic models include individual seismogenic structures/faults liable to generating major earthquakes with magnitude greater than 5.5, and background areal source model to evaluate the effect of earthquakes with magnitude less than 5.5. The PSHA is built up based on the long-term earthquake recurrence on seismogenic tectonic faults and the spatial distribution of historical earthquakes. Site amplification is considered based on seismic microzonation maps derived for the western area of Naples. The microzonation maps delineate expected levels of ground motion amplification based on reliable geological and geotechnical subsoil models. Hazard maps are derived for a number of return periods for ground-shaking in terms of peak ground acceleration and 5%-damped pseudo-spectral acceleration at a range of periods that are representative of the existing construction within the area. Detailed comparisons of the PSHA results with Italian national hazard maps and the code-based design spectra emphasize the importance of performing site-specific PSHA with explicit consideration of site effects.

Research on appropriate borehole density for establishing reliable geological model based on quantitative uncertainty analysis

Geological structure is an important factor to explore the underground geological conditions for hydrogeological purpose. Borehole density has great influence on the accuracy and application of geological model. In this paper, Transition Probability Geostatistical Software (T-PROGS) has been used to simulate the four facies distribution of West Liao River Plain. And a quantitative uncertainty model of entropy method is introduced. For getting a reliable geological model with as few as the boreholes, two parts have been given. One is the vertical lithologic variability analysis, and the other is the model correct rate and uncertainty analysis. In geological modeling, the borehole data is too sparse to characterize the lateral heterogeneity, so the actual profiles are added. At last, many equal probability realizations of the geological model using 350 boreholes are built. Depending on the model calibration, uncertainty analysis and simulated profile comparison, the geological models are reliable. Thus, for the simple and single stratigraphy study area without complex fault structures and graben structures of several thousands to tens of thousands of square kilometer scale, establishing a reliable geological structure model requires one borehole at least within an average area of 120.81 km2. It is of great significance for decision maker to save manpower and material resources. And we present a workflow to build a 3D Markov chain using boreholes and actual profiles and develop a reliable geological model.

Multi-scale modeling of shale laminas and fracture networks in the Yanchang formation, Southern Ordos Basin, China

Outcrops and core observations show that sandy and tuffaceous laminas and natural fractures are well developed in the continental shale gas reservoir. This study reports the distribution of laminas and natural fracture networks at different scales, in cases of outcrops, wells and cores from Yanchang Formation, southern Ordos Basin. Firstly, based on two-dimensional fracture field investigations, a 3-D joint network model of the study area was built using the Monte Carlo simulation method. Then the laminations were identified from macroscopic scales to microscopic scales with multiple probe techniques. Statistical analysis of multi-scale layer thickness suggested that the average thickness of layers at multiple scales showed a fractal feature, and that the layer thickness at each scale followed with an exponential probability distribution, whose exponential coefficient was −3.38, −1.91, −1.65, −1.21, corresponding to meter scale, decimeter scale, centimeter scale and millimeter scale respectively. The fitting curves indicated that the majority of laminas at each scale were relatively thin, and the thicker the layer, the less the number of layers contained in shale. Finally, the lamination models were constructed and superposed over the joint network model to generate 3-D geological structure models at various scales. The models were validated by reproducing fracture and lamina parameters fairly close to those obtained from realistic geological bodies in the study area. The findings of this work could provide a more reliable geological model for the numerical simulation and physical model test of hydraulic fracturing in shale gas reservoir.

Seismic depth imaging of sequence boundaries beneath the New Jersey shelf

Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model.

3D geological modelling of the Renard 2 kimberlite pipe, Québec, Canada: from exploration to extraction

The Renard 2 kimberlite pipe is one of nine diamondiferous kimberlite pipes that form a cluster in the south-eastern portion of the Superior Province, Quebec, Canada and is presently being extracted at the Renard Mine. It is interpreted as a diatreme-zone kimberlite consisting of two Kimberley-type pyroclastic units and related country rock breccias, all cross-cut by coherent kimberlite dykes and irregular intrusives. Renard 2 has been the subject of numerous diamond drilling campaigns since its discovery in 2001. The first two geological models modelled kimberlite and country rock breccia units separately. A change in modelling philosophy in 2009, which incorporated the emplacement envelope and history, modelled the entire intrusive event and projected the pipe shape to depth allowing for more targeted deep drilling where kimberlite had not yet been discovered. This targeted 2009 drilling resulted in a > 400% increase in the volume of the Indicated Resource. Modelling only the kimberlite units resulted in a significant underestimation of the pipe shape. Current open pit and underground mapping of the pipe shape corresponds well to the final 2015 geological model and contact changes observed are within the expected level of confidence for an Indicated Resource. This study demonstrates that a sound understanding of the geological emplacement is key to developing a reliable 3D geological and resource model that can be used for targeted delineation drilling, feasibility studies and during the initial stages of mining.

Using sequence stratigraphic approaches in a highly tectonic area: Case study – Nubia (A) sandstone in southwestern Gulf of Suez, Egypt

West Esh El Mallaha area is located west of the Hurghada shoreline. It pertains to the southwestern province of the Gulf of Suez. Nubia (A) sandstone is one of the prolific reservoirs in the western side along the Gulf of Suez area. To enhance further oil production and to develop this reservoir, it is important to gain a clear understanding of the reservoir in terms of its depositional origin. In west Esh El Mallaha area, the understanding of the depositional setting of Nubia (A) is relatively hard due to the limited number of cores.A comprehensive workflow which integrates all geological datasets (electrical logs pattern, the high resolution biostratigraphic analysis, and previous studies) which has been performed for the Nubia (A), enables to recognize different patterns of electrical logs, which are used to define the sequence stratigraphy and systems tracts for Nubia (A). The Lower Nubia (A) is characterized by fining-upward profile and well-developed coarsening-straight profile interpreted as a braided – fluvial facies (lowstand system tract). On the other hand, the upper Nubia (A) is characterized by fining-upward, coarsening-upward, and bell profile interpreted as meandering fluvial to fluvio-dominated delta (transgressive system tract).This study is an approach to build a reliable geological model, and give wide view to evaluate and develop the reservoir in the drilled areas and predict sand distribution in the undrilled areas despite the limited number of cores.