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Third EAGE Borehole Geology Workshop
- Conference date: October 14-17, 2019
- Location: Muscat, Oman
- Published: 14 October 2019
20 results
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“Advanced techniques for image log interpretation in carbonate reservoirs: workflow, geological control factors, dynamic data integration”
Authors G. Buongiovanni, R. Berto, M. Pirrone and G. TrombinSummaryThe approach makes an extensive use of wireline and while drilling electrical borehole image logs and provides a direct and fast recognition of the main geological features at multi-scale level and a secondary porosity quantification.
A further characterization of the facies can be established by means of image processing techniques which are mainly aimed to quantify the different components of secondary porosity. We adopt the Watershed Transform (WT) approach which is based on digital image segmentation processes.
The WT-based algorithm provides a robust quantification of the secondary porosity contributions to total porosity in terms of connected vugs, isolated vugs, fractures and matrix contribution rate. Finally, image log-facies classification and quantitative porosity partition can be integrated with production logging and pressure transient analyses to reconcile the obtained carbonate rock types with the effective fluid flows and the associated dynamic behavior at well scale.
The presented methodology can perform an advanced automatic interpretation of field-scale image log datasets, avoiding time-consuming conventional processes and not efficient standard analyses when the number of wells to be handled is large.
The added value from this data-driven image log analysis is demonstrated through selected case studies coming from wells in carbonate reservoirs with high heterogeneity.
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Borehole Image Logs applied to Sequence Stratigraphy and Geothermal Exploration in Carbonates: an Integrated Workflow(UpperJurassic/Molasse basin).
Authors P. Wolpert and T. AignerSummaryBorehole image interpretation in carbonate reservoirs is very challenging. While fractures, faults and karst can often be recognized very well (especially if filled with conductive drilling mud) internal limestone texture is more challenging to identify. However, in some cases, diagenesis can significantly enhance such features and highlight details of the internal composition of carbonate rocks. This amount of detail allows classifying a total of 13 borehole image facies types for the Upper Jurassic limestone reservoir, which are calibrated with borehole cores and cuttings. The borehole image facies interpretation is now used to quality control seismic facies interpretation and further refine it.
Vertical stacking of borehole image facies, important stratigraphic marker beds and surfaces reveal the sequence stratigraphic architecture and help to delineate genetically linked depositional units. Flow units (especially associated with karstification) are often found at sequence boundaries. Hence, a robust and validated sequence stratigraphic framework forms an essential part of the geothermal exploration strategy.
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Data Integration - Time and Discipline Dependencies
By A. ThorsenSummaryFocus on the matter of scale when placing wells and focusing on production. Typically there is some major focus areas during well placement, hence other are more in the background, although equally important. Points around time and changes to in-situ properties of the rock with production related changes. Use of information acquired at different times, often with years or decades apart, can play a major role in understanding reservoir dynamics.
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Novel Dip Picking Approach using “Expert Dip” in HAHZ Well and Influence on Structural Modelling
Authors S. Das, G. Sultan, V. Vallega and S. BhadraSummaryIn this era of automation, manual dip analysis method is evolving as more and more technology is seeping into geological interpretation. Since advent of image log in horizontal wells, low angle bed boundaries which are near-parallel to wellbore and traceable on borehole images for several tens of feet, can hardly be attributed with dips as conventional approach of mathematical sinusoid fails to well-fit bedding features resulting inaccuracy of dip interpretation. This leads to loss of information and restricted interpretation in terms of bedding dips specially in horizontal or highly deviated sections of image.
Recently, a new approach has been introduced to trace such bed boundaries in horizontal wells. Quality indicators are also available to ensure proper tracing and hence more accurate dip computation. Instead of the conventional sinusoidal algorithm, this technology contours the lithological boundaries and provides true dip and azimuths of these beds at every desirable sampling interval. This case study shows applicability of the methodology and its implementation in image based high resolution structural analysis of high-angle/horizontal (HAHZ) wells. After comparison with conventional results it is evident that this new way of working with HAHZ well images has an edge over conventional dip analysis method.
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Borehole stability applications using high-resolution LWD acoustic caliper images
Authors L. Solberg, J. Titjen and S. MorrisSummaryLogging-while-drilling is an increasingly important mode of data acquisition in inclined wells and has been undergoing a continual evolution in measurement types and increasing resolution. The recent development and upscaling of a LWD acoustic imaging service is the enabling technology that allows high-resolution profiles of borehole shape. Acquisition has been across a range of well inclinations (from vertical to horizontal) and geological environments (sedimentological and structural). We show applications based on borehole shape measurements that include borehole stability while-drilling and time-lapse effects on stability where LWD acquisition allows relogs to be taken after drilling has completed. High-resolution acoustic images available in the LWD environment, allow a closer monitoring of the borehole geometry in the sense that it can provide the means to understand risks related to development of geomechanical features, and being able to make mitigation strategies to obtain or sustain borehole stability during drilling-, wireline- and/or well completion operations.
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Particle Shape Analysis for Conglomerate Reservoir Using Borehole Resistivity Images
Authors A. Aviantara, S. Yang, W. Huang, C. Chen, I. Le Nir, J. Yuan, S. Li, H. Delius and K. PokhriyalSummaryWe develop this advanced analysis tool to get more precise results include the long axis length, area, sphericity and roundness. Moreover, the large/flatten patch can be used as paleocurrent analysis from the azimuth of long axis.
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Advances in Borehole Geology Interpretation using the new Dual Imager LWD Tool for Oil-Base Mud
Authors G. Barbacini, C. Shrivastava, R. Berto, T.A. Bianco, F. Colombo, M. Miraglia, A. Riva and V. Wibowo KrissetiawatiSummaryBorehole imaging while drilling in oil-base mud (OBM) has been a challenge for a long time and the interpretation of borehole geology on these well has been more problematic compared with the wells drilled with water-base mud. Whereas wireline logging benefited of a new OBM generation tools with very high definition, released on the market in the last years, the logging while drilling (LWD) lacked the same kind of offer. The new dual physics LWD tool for OBM described in this work is focused on adding high resolution imaging measurements in the global marker offer. The tool provides detailed geological information from electromagnetic images and gives a geomechanical investigation of the near borehole by means of ultrasonic measurements.
During the last two years, Eni has acquired this type of data in four wells from vertical to sub-horizontal trajectory. The quality was quite encouraging, permitting to have a better characterization of geological settings, including bedding and fractures and obtaining some geomechanical important information. The evolution through the several acquisitions has demonstrated the capability to deliver data from only recorded mode to real time. At the moment, the acquired image data appear to be treated and improved using special post-processing.
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Borehole image structural modelling and synthetic dip modelling in 3D
Authors L. Bourke and O. SalafonovSummaryBorehole images are studied with open hole log, core and regional knowledge to refine models. This is upscaled, to delineate reservoir geometry and to optimise well placement for reservoir development and production optimisation.
We developed software-based workflows to improve the efficiency of structural well zonation by simultaneously working with depth based structural plots together with enhanced vector and stereo plots which can be directly edited into reports with minimal editing.
These structural zones are then further subdivided into structural elements (fault drag, fold limbs etc.). These structural elements are a discriminated Structural Dip set, that effectively upscales the detailed Manual Dip Set, to a Structural Dip Set.
A geometric model is then selected in our Structural Interpretation Advisor which extends a model from the well path, by Bezier surfaces. A Synthetic Dipset is then generated from the layer surface intersections with the well path and overlaid on the Structural Dip Set.
The synthetic and Structural dips is iterated to achieve a better fit of synthetics to dips, by manipulating the model in the X, Y and Z, tilt, plunge, throw etc.
This approach adds confidence in conventional dip interpretation by allowing 2D, 3D and map visualization of complex structure.
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Analysis of subseismic-scale folds in complex tectonosedimentary settings: A case study from the Austrian Molasse Basin
Authors M. Habermueller, G. Wiesmayr and B. GrasemannSummaryThis case study from the Austrian Molasse Basin shows the results of an exploration well that targeted a deep marine axial channel belt in the foreland of the North Alpine Thrust Wedge. Borehole image logs were analysed complementary to 3D seismic data, revealing the complex internal architecture at the margin of the channel belt.
Extensive folding was detected in the borehole, that was not expected from seismic analysis. Due to the close vicinity to the Alpine fold-and-thrust belt, the origin of these folds was ambiguous and related either to tectonic processes or soft-sediment deformation. Detailed geometric investigations revealed the presence of slump folds that were clearly distinguished from alpine tectonic fold trends. A full characterization of slump geometries was performed and discussed in the context of basin evolution and channel architecture.
Fold hinges show significant scatter, suggesting a fairly high complexity of fold geometries, such as higher order folds or refolds. Coherent slump folds were separated from folds with higher complexity and used for subsequent paleoslope analysis. The results show that slumping was not related to gravity flows along the axial channel, but was rather triggered by tectonic movements from the south slope of the Molasse Basin.
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Integration of latest oil-base mud borehole images with lower resolution tools, Thunder Horse North field, GOM
Authors C. Vahle, B. Ruehlicke, Z. Veselovsky and B. HansenSummaryRecent borehole imaging technology significantly improved the resolution within oil-base mud environments. The integration of such high-resolution borehole images (BHI) with data from vintage tools as well as core and seismic allows for an advanced interpretation of structural dip and depositional environment, being valuable particularly in challenging areas such as the Mississippi Canyon, Gulf of Mexico. The latest BHI data is used to verify previous hypotheses for the interpretation of the structural dip within the Thunder Horse field. The Thunder Horse reservoir interval is characterized by mass transport deposits, where the majority of mud-prone beds represent slump units and slide blocks of variable orientation. Therefore these mudstones cannot be used as paleo-horizontal indicator. Conversely, intercalated turbiditic sands with parallel layering are sought as reference for paleo-horizontal. As a consequence, the halokinetic tilting near the Thunder Horse North salt wall is analyzed from stereographic projections of these sand units instead. After restoring the pre-halokinetic bedding dip a S to SSE directed sediment transport is interpreted for these Middle Miocene reservoirs, hence excluding a salt barrier or deflection of the turbiditic currents.
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Using core photos as image logs: An example from a fractured reservoir in Algeria
Authors J. Paludan, M.S. Abrouche, Y. Oulad Hedda, B. Hichour and H. TalebSummaryCore photographs provide the highest resolution continuous record of geological information from a borehole. The value of integrating this detailed information with borehole images (and other logs) is well known to borehole geologists. If the core photos are in the form of full circumferential scans they can be converted into a continuous oriented image, which may be analysed in a manner similar to a conventional image log. We discuss the benefits and limitations of the technique and present a case study, where core images formed the basis of a field-wide fracture study. We demonstrate how core photos, in combination with image logs, can be used to define various types of fractures and relate these to the known geological history, including burial history, tectonic and thermal events. This information is key to identifying potential hydraulically conductive fractures and exploiting these in future field development.
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Efficient Application of Advanced Mud-logging in Unconventional Reservoirs: A Cost-effective Methodology from Borehole Geology to Fracture-Stimulation
Authors J. Peano, P. Delgado and C. ShrivastavaSummaryThe unconventional reservoirs need efficient stimulation, and often advanced well-log data are required to meet that objective with characterization of best reservoir quality and completion quality intervals. However, often the operational and economical constraints later in the development phase could mean minimal access to high-tier measurements. The borehole geology data collected in form of mud-gas and cutting could often play a very important role in such cases, where advanced analysis of this data could provide cost-effective and efficient answers towards identification of best intervals for hydro-fracturing.
In the study well, advanced mud-logging information was used for the selection and design of hydraulic fractures leading to cost-effective approach for “factory mode” unconventional wells for mineralogy, TOC data and geochemical data acquisition as complementary source of information for geo-steering in horizontal drains. The earlier studies of the cuttings and gas against the fracture-stages identified from well-logs in previous well, integrated with the production data provided the confidence of using the cuttings-based methodology to deploy in the study-well where well-logs could not be acquired due to operational constraints.
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Geological Data Integration in Automation Processes
By A. ThorsenSummarySeveral areas need improvement to ensure the inclusion of image logs and geology implementation into the automation pathway. this paper is looking into a few points of interest when it comes to the usge and understanding of geological data in an automated setting.
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Isotope Logging: A Case Study of Integration with Borehole Geology
Authors A. Di Daniel, D. Strąpoć, C. Shrivastava and C. MurlidharSummaryIsotope logging has been used regularly as advanced mud-logging services; however, it has not been often integrated with other while-drilling data, such as borehole images to characterize the sub-surface. Real-time δ13C1 Isotope logging service has been used as a formation evaluation tool and its capability of providing stable and high-resolution data under difficult conditions on an offshore drilling site becomes more important for realtime decision making while integrating with logging-while-drilling (LWD) data.
This case study comes from the Sabah Basin, located on the North western continental margin of offshore Malaysia. The hydrocarbon reservoirs in the Sabah Basin are predominantly siliciclastic. This basin is subdivided into provinces that are characterized by distinct structural styles and sedimentation histories. Seismic investigation of study-area showed that’s it is complexly faulted and the compartmentalization is perceived as a recovery risk, including suspected sub-seismic fault population.
Real-time δ13C-C1 Isotope logging service proved to be a cost-effective qualitative tool to understand the sub-seismic faulting of the reservoir. Integrating this data with borehole images confirmed various degrees of subsurface compartmentalization and provided verification and increased interpretation confidence.
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Image Logs Worth Hundred Applications: Industry’s First Innovative High-Resolution Dual-Imager Logging-while-Drilling Technology Overcomes Barriers of Oil-base-Mud
Authors C. Shrivastava, C. Maeso and V. WibowoSummaryAn innovative LWD dual-physics imager has been recently deployed, providing much-needed high resolution measurements for the ever-growing applications through various stages of an oilfield; thereby finally providing borehole images in OBM while drilling worthy of hundred applications with real-time capabilities.
Full-bore images can be acquired simultaneously; apparent resistivity images from electromagnetic measurements, and acoustic amplitude & transit time images from ultrasonic measurements. The resistivity images provide rich information related to sedimentation style, highlighting the sedimentary structures, textural variation and diaenetic imprints; while the ultrasonic images are more sensitive to fractures and drilling induced features, such as induced fractures and break-out. This innovation LWD tool combines the complementing nature of the high-resolution ultrasonic and electromagnetic image technology without introducing complexity to the drilling bottom-hole assembly in a 15-ft sub.
However, many sub-seismic structures (fractures/ faults) are found to be better imaged on apparent resistivity images quite often due to the contrasting features across them. And, a few times even the ultrasonic images could show thin-beds if enough contrast is seen due to cementation along some beds. Therefore, the need of the dual imager is established to image different features for comprehensive geological interpretation, wellbore stability related features and further petrophysical applications
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A New Prospective in Geological Data Acquisition for Well Placement Operations
More LessSummaryThe latest technologies and innovations in while drilling technologies relevantly reduce geological uncertainties in Geosteering operations. The Ultra Deep Directional E.M. technology, sensitive to resistivity contrasts up to tens of meters around the drill string, is a significant step change in the oil industry because it represents the missing puzzle piece between borehole data and seismic data. The application of this technology goes beyond traditional real-time well placement with important implications in updating 3D geological models. Multidisciplinary integrated teams of experts from operating and service companies are collaborating more frequently on shared interpretation workflows, improving the effectiveness of data exchange capacity. The final outcome is a geological picture coherent with stratigraphycal, petrophysical and structural real time observations, reducing at the minimum the associated uncertainty and optimizing an efficient drain placing.
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Integration Borehole Image and WEB AVO inversion for fracture prediction in deep reservoirs
Authors A. Pascarella, P. Van der Vegt, C. Leo, M. Zhang, P. Doulgeris and P. HaffingerSummaryDeep and tight reservoirs are an important target for both Oil and Gas and Geothermal Industries. Fractures have a key role for producing from such reservoirs and therefore fracture identification is essential.In this talk we analyse the potential correlation between BHI fracture characterization results and elastic properties as output by wave-equation based AVO (WEB-AVO) inversion. WEB-AVO inversion is unique in the sense that it directly inverts for compressibility and shear compliance (inverses of bulk and shear moduli). While those parameters are already successfully used for exploration and production of hydrocarbons as well as for underground storage of CO2, here we will test their usefulness in the context of geothermal exploration.
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Carbonate Reservoir Rock Typing and Mapping from the Horizontal Well High Resolution Logging While Drilling Images
Authors S. Yang and R.H. Al LawatiaSummaryTo better provide rock typing in carbonate reservoir more efficient, we propose a solution for the rock typing from Log While Drilling (LWD) high resolution images. The porosity in carbonate is controlled by the secondary porosity and can be computed from borehole images with integration with traditional total porosity measurement; and pores connectedness is a good indicator for the formation permeability. The fracture evaluation is another key element for reservoir permeability computation; and we can identify, classify and compute fracture parameters from borehole image confidently.
Based on the secondary porosity and fracture evaluation result, we can classify the reservoir rock typing with Heterogenous Rock Analysis (HRA) clustering by integrating the principle components analysis (PCA) and K-means clustering algorithm. And then the reservoir mapping can be achieved by combining the structure and rock typing.
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The integration of core and borehole image log data using core goniometry
Authors J. Prosser and L. BourkeSummaryCore goniometry is an established technique. However, the explosion of borehole imaging that occurred in the 1990’s onwards corresponded somewhat with a decline in the acquisition of cores by operating companies. Borehole images were acquired over much longer intervals than cores, and provided cost effective high resolution oriented data-sets. However, an increasing shift to drilling wells with non-conductive mud systems over the last decade has countered this to a degree, and there appears to be increased or renewed interest in using cores to undertake core goniometry to derive high resolution oriented datasets. This has in part been driven by the limitations common in some earlier generations of imaging tools developed for use in non-conductive borehole environments. In such cases, core goniometry can provide very significant increases in data density compared to borehole images, enabling highly detailed sedimentological and structural interpretation. 10-fold increases in dip data density are possible. The paper will summarize some of the techniques that can be used for core goniometry, demonstrating the orientation principle using Task Fronterra’s attitude software, and outlining the types of “core versus log” data density variations, together with benefits and limitations that may be encountered.
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