- Home
- Conferences
- Conference Proceedings
- Conferences
76th EAGE Conference and Exhibition 2014
- Conference date: June 16-19, 2014
- Location: Amsterdam, Netherlands
- Published: 16 June 2014
1 - 20 of 1028 results
-
-
Integration of Surface Seismic and Well Information to Improve Drilling Success for Onshore Carbonate Caves
SummaryOrdovician carbonate caves have been considered as important reservoirs for a long time and their exploration has rapidly increased in recent years in China ( Yang et al, 2010 ). Accurately locating the target is very critical to improve drilling success for carbonate caves. As carbonate reservoir exploration has moved deeper and deeper (6000–8000 m), wells often either hit the side of the cave or totally miss it. Here we look at the application of a new technology that is particularly suited to cave drilling. It initially builds an accurate baseline earth model; and then, during the process of drilling, it updates the subsurface image in real time by using information acquired while drilling in combination with surface seismic data. In this paper we show how this new technology can be used to help accurately reach deep carbonate caves.
-
-
-
Full Waveform Inversion on the NW Shelf of Australia
Authors C.D. Manuel, G. Hampson, D. Chagalov, D. Bevc, T. Xu, B.J. Lim and D. VighSummaryA workflow for integrating full waveform inversion (FWI) with reflection tomography has been refined using narrow azimuth towed streamer (NATS) 3D seismic data from the North West Shelf (NWS) of Australia.
We show that FWI using relatively short offset NATS data with limited low frequency content can provide a high resolution velocity field if it is combined with reflection tomography in the workflow. Although other techniques exist for building an initial FWI model, reflection tomography was chosen here since a reasonably mature model was accessible from a project being run in parallel. Integration of reflection tomography and associated quality control (QC) practices into the time domain FWI model building sequence was found to be necessary to help the FWI converge to a satisfactory solution when turning ray energy was limited or non-existent. Investigation of typical FWI parameters was also necessary to refine each frequency update.
We also show comparisons of inversions for acoustic and elastic impendace from using FWI and reflection tomography data from this area.
-
-
-
Predicting Multi-scale Deformation and Fluid Flow Patterns in Folds Using 3D Outcrop Models and Mechanical Modelling
Authors K. Bisdom, G. Bertotti and B.D.M. GauthierSummaryNatural fracture patterns in folded carbonates are highly heterogeneous. The present-day fractures are often the result of pre-folding, syn-folding and post-folding related fractures. Furthermore, syn-folding fractures may differ in different domains of the fold. Although there are studies that characterize fracture patterns in outcropping folds, there is still a poor understanding of the relation between large-scale deformation (i.e. folding), and small-scale deformation (i.e. fractures), especially in terms of stresses and process-based predictions of fractures. Our overarching goal is to assess the sensitivity of reservoir-scale flow to different fracture patterns and different fracture properties. Therefore we build multi-scale models of 3D fracture networks in outcropping folds in the foothills of the Tunisian Atlas (central Tunisia). The fracture data is collected from outcrops using efficient methods that collect both fractures and the 3D geometry of the outcrops. We interpret small-scale deformation in terms of stresses and combine this with fold-scale mechanical models to predict the fracture patterns in 3D throughout the fold. The 3D model is used to model fracture fluid flow. This work presents a new approach to outcrop studies, that distinguishes different stages of fracturing and uses stresses to make predictions about fracture patterns in similar structures.
-
-
-
Natural Fracture Characterization in Aptian Carbonates, Araripe Basin, NE Brazil
Authors T.S. Miranda, J.A. Barbosa, J.F.W. Gale, R. Marrett, I. Gomes, V.H.M.L. Neumann, G.C. Matos, O.J. Correia and M.L. AlencarSummaryThis paper addresses fracture characterization in an Aptian laminated limestone, the Crato Formation, cropping out in the Araripe Basin (NE, Brazil) using a scanline technique. This unit has been used as a geological analogue of buried naturally fractured carbonate reservoirs. In recent years, studies of fractured reservoirs have drawn considerable attention due to their significance for oil production and enhanced recovery. The study was based on the use of traditional scanline surveys, and the recording of fracture orientation, morphology, crosscutting relationships, composition, texture of fracture fill, fracture aperture-size distribution (frequency), spatial distribution (coefficient of variation), and strain for each fracture set. The main fractures identified in the Crato Formation were shear- and opening-mode fractures (veins) and with stylolites also present. In this study we focus on opening-mode fractures, which strike in two main directions, NNW-SSW (set 1) and NE-SW (set 2), and are filled by recrystallized calcite. Fractures of set 2 have a wider kinematic aperture and spacing range and are more likely to be clustered than are fractures of set 1 (NE). These results have been used to populate computational models that consider the widespread fracture system in the geomechanical modeling of carbonate reservoirs.
-
-
-
Controls on Failure Mode in Fractured Chalk, and Its Influence on Fracture Geometry
Authors M. Welch, R.K. Davies and R.J. KnipeSummaryThe mode of failure can exert a major control on the geometry of fractures in chalk: Mode 1 dilatant fractures are typically vertical, short, bed-bound but very closely spaced (20–50cm apart), whereas Mode 2 shear fractures are much longer, cut across bed boundaries, and form inclined conjugate sets, but are more widely spaced (1–3m apart). At Flamborough Head, northeast England, we see Mode 2 shear fractures formed in the lower Welton Chalk Formation but Mode 1 dilatant fractures in the overlying Burnham Chalk Formation. This will have a big impact on fluid flow through the two units: the Burnham chalk will have a high horizontal permeability but a low vertical permeability, whereas in the Welton Chalk horizontal permeability will be lower but vertical permeability higher. We use simple mechanical models to show that the failure mode in chalk is dependent on the depth of burial, mechanical properties, fluid pressure and mechanism of fracturing.
-
-
-
Understanding the Interplay of Fractures, Stresses & Facies in Unconventional Reservoirs - Case Study from Chad Granites
Authors D. Lirong, C. Shrivastava, D. Chuanshu, W. Jingchun, N. Hammond, C. Anoliefo, D. Lei and M. SiddickSummaryThis work presents a a case study from Bongor basin, Chad which utilizes the geological evolution approach to effectively characterize unconventional granitic reservoir based on the interpretation performed with borehole images and open hole logs. Interplay of fractures and facies and the impact of the prevalent stress regime have been deciphered from the study wells with the help of borehole images and petrophysical logs. Three main distinct facies were interpreted; Unweathered, Leached and Fractured (Normal and Intensely Fractured sub-facies) granites respectively. Within the leached granite, there exist fault breccia and major faults with two dominant strike orientations; NE-SW and NW-SE. This resulted to the development of secondary porosity within these reservoir zones. The observed granite basement facies, particularly the fractured and leached granites developed good secondary porosity due to differential leaching and fracturing.
The placement of subsequent wells in the preferred leached and fractured reservoir facies bearing fractures that possess the same orientation as the maximum stress depends on several determinants, one of which is the location of the proposed well with respect to the prevalent stress regime attributed to tectonic forces from the Central African Shear Zone arising from the West and Central African Rift system.
-
-
-
Structural Development of the Dutch Central Graben - New Ideas from Recent 3D Seismic
Authors E.A. Rosendaal, N. Kaymakci, D. Wijker and B.M. SchrootSummaryA regional study on the northern Dutch Central Graben (DCG) and Step Graben (SG) based on, amongst others, very recent regional 3D seismic data has resulted in new ideas on the structural development of the area.
It is postulated that main rifting of the DCG occurred during Middle to Late Triassic. The Late Jurassic extensional phases and the Early Cretaceous inversion phases affected the NS orientated DCG and SG in a different way than the NW-SE orientated basins. Under the NE-SW Late Jurassic extension, the NS bounding faults were not reactivated but WNW-ESE extensional faults developed creating a graben stepping down to the north. Furthermore, it seems that the Early Cretaceous inversion also did not reactivate the NS bounding faults but manifests itself only in a broad basin uplift with minor transpressional features.
Based on this regional work, we expect to improve our understanding of the timing of events, erosion amounts and paleogeography. We foresee future basin modeling to obtain further insights into the hydrocarbon maturation history. The observed WNW-ESE fault trends in the DCG could have tectonically controlled Late Jurassic to Early Cretaceous sedimentation and local accommodation space along the fault escarpments may create interesting opportunities for hydrocarbon exploration.
-
-
-
Structural Framework Derived from Surface Satellite Data Integrated with Subsurface Gravity-seismic Imagery, SE Kenya
Authors D. Necea, M. Oehlers and N. JohnsonSummaryThis study reveals that surface satellite-derived structural results integrated with subsurface gravity and seismic imagery provides explorers a reliable assessment of the structural framework when searching for natural resources in new ventures, such as the Lamu Embayment, Kenya. This data integration shows that some of the surface faults extend at depth through the sedimentary covers as illustrated by the gravity contrasts and seismic interpretation. The NNW-SSE-trending and ENE-dipping normal faults are major basin bounding faults to N-S-oriented half-grabens and NNW-SSE-oriented Tana rifting zone, respectively. These bounding faults are probably Precambrian basement structures that were reactivated during subsequent tectonic events, e.g. Pliocene-Quaternary in the east. This age is inferred from NNW-SSE normal and ENE-WSW and WNW-ESE to NW-SE strike-slip faults, and fluvial networks affecting and incising, respectively, the Miocene-Quaternary deposits. The faults can delineate potential structural traps, e.g. uplifted footwalls of normal faults, roll-over anticline, which may be good traps for hydrocarbon accumulations. Present-day extension direction along the Kenyan coast is inferred as E-W in the south and ENE-WSW in the north. Analysis and conclusions of this study form part of the early stage of the area evaluation and need to be integrated with other datasets (FTG, seismic and more fieldwork).
-
-
-
Geometry and Forming Mechanism of Synsedimentary Structures in Northern Melut Sub-Basin, South Sudan
More LessSummaryThe Melut Basin is a rift basin elongated in NW-SE direction located in south Sudan. Under the influence of Intracratonic extensional forces that resulted from the opening of the Atlantic, and associated left-lateral strike-slip, a series of synsedimentary structures are developed in Melut Basin. On the basis of different features of structure development continuous, late deformation and drive mechanism, there are mainly three types of synsedimentary structures developed, i.e. inherited structures, fault-related structures and differential compaction-related structures, respectively. Inherited structures are inherited from paleo-uplift and reformed by later-stage faulting. Fault-related structures form as a result of displacement decreases with distance from the fault surface caused by low dip angle listric fault. The origins for the listric fault include listric basin-bounding fault caused by adjacent titled block and strike-slip fault involved into shale formation. The main two types of differential compaction-related structures are caused by intense differential compaction within intervals of sandy conglomerate of alluvial fan and the original sediments are inclined to collapse into depression during sedimentary compaction, respectively. The synsedimentary fault and its assemble pattern controlled the distribution of sedimentary facies, the synsedimentary structures has great influence for the generation, migration, accumulation and preservation of oil and gas.
-
-
-
Subtle Prospects Identification and Hydrocarbon Accumulation Model in Slope Zone, Rift Basin - A Case in Melut Basin
More LessSummaryTaking 3D seismic survey in Melut Basin for an example, we study the types and hydrocarbon accumulation model of subtle prospects in the slope zone controlled by palaeohigh in passive rift basin. Based on palaeogeomorpholgy restoration and sedimentary facies study, the subtle prospects contain the types of stratigraphic overlap and lithologic pinch-out in the zone, which mainly develop in the strong rift phase. The stratigraphic overlapping boundary can be identified by seismic attributes of Number of Zero Crossings, and the slump fans can be identified by seismic attributes associated with amplitude energy.
-
-
-
Seismic Calibration of Distributed Acoustic Sensors (DAS) in a Joint Borehole-surface Experiment
Authors F. Poletto, A. Clarke, A. Schleifer, D. Finfer and P. CoruboloSummaryDistributed acoustic sensors (DAS) are an emerging fibre optic-based technology enabling seismic investigations with innovative configurations by massive receiver arrays in boreholes and at the surface. Advantages of DAS technology include lower equipment costs and reduced installation complexity, especially in boreholes, with respect to equivalent applications using conventional seismic sensors. We present results of a joint borehole-surface calibration experiment. The main targets of this study were the analysis of S/N and of the directional responses for recorded wavefields. Borehole signals were acquired by DAS and compared with signals acquired by permanent 3C geophones installed outside the casing of the instrumented well at maximum depth of about 200 m. Multi-offset vertical seismic profiles were acquired by a surface seismic vibrator source with two different azimuths. At the surface, settings of buried and near-surface sensors was prepared in a cross of trenches using DAS cables along with single and multicomponent geophones at corresponding positions. Using the surface installation, a reciprocal seismic line was acquired by maximum offset of approximately one kilometer for the vibrator source. The analysis shows the correspondences in the seismic wavefields acquired by the different methods, compares the physical quantities, and confirms the quality of the DAS signals.
-
-
-
Seismic Data Analysis Using Digital Music Technology - Applications in Hydrocarbon Exploration
Authors P. Dell’Aversana, G. Gabbriellini and A. AmendolaSummaryWe introduce a novel approach for geophysical data processing, interpretation and integration. It is based on ideas and methods imported into the geosciences from the domain of sound analysis and digital music production. The presentation is divided in two main parts. First we introduce the theoretical and technical background. Starting from the already known concept of ‘sonification’ we derive other inedited ideas and methods. We explain how these are complementary and not substitutive of the methods currently used for geophysical data processing, imaging, and interpretation. In the second part, real applications of integrated imaging and sounding analysis addressed to hydrocarbon exploration are discussed.
-
-
-
Benefit of Ultra-long Offset Data for Subsalt Imaging in Deep Water Gulf of Mexico
More LessSummaryIn the deep water Gulf of Mexico, wide azimuth (WAZ) data and the evolution of advanced imaging tools, such as TTI reverse time migration (RTM), have significantly improved the quality of subsalt imaging. By combining WAZ data with existing narrow azimuth data, imaging resolution is further improved.
However, subsalt imaging still remains difficult in areas with complex salt geometries, such as steeply dipping salt flanks and subsalt three-way closures. Full azimuth and long-offset acquisition is the latest acquisition technology to address subsalt imaging challenges. We analyze the impact of ultra-long offsets (up to 18 km) with 2D elastic modelling. Ultra-long offsets provide the ability to image steeply dipping subsalt events and undershoot complex salt geometry. With ultra-long offset field data extracted from a full azimuth survey, we also demonstrate that ultra-long offsets provide extra illumination power, helping image dipping subsalt events and improve the continuity of subsalt events in areas with complex salt geometry. Moreover, ultra-long offsets provide greater incident angle coverage in RTM 3D angle gathers, potentially aiding subsalt velocity updates.
-
-
-
Optimal Survey Design for Big Data
Authors D. Coles, M. Prange and H. DjikpesseSummaryIndustrial geoscience is entering the age of ‘big data’, in which the data volumes routinely acquired for analysis are so large that they can no longer be processed by traditional workflows. How can we store and mine this deluge of information?
In this article, we focus on model-oriented design and analysis (MODA) -- the theory and practice of designing experiments to maximize the information expected in data observations. MODA is appealing because it is an optimization method, which offers confidence in the expected results, and because it can be applied before or after data acquisition, to either forecast the most informative data to acquire or to optimally select data from existing datasets. MODA reduces costs by increasing efficiency in either scenario, whether through data acquisition or data processing.
However, MODA is itself challenged by the computational demands of big data, and researchers are seeking ways to reduce its computational cost. One novel possibility is dimension reduction – especially if it is parallelizable. We develop a dimension reduction workflow for guided Bayesian survey design – a linearized MODA technique – that greatly reduces the computing cost of optimal survey design, and we demonstrate its utility on a real, industrial-scale marine seismic design problem.
-
-
-
Energy Efficient Technologies of Hydrocarbon Resources Development
Authors M. Kotenev and A. KotenevSummarySubstantial deterioration of oil and gas reserves base is noted in many petroleum regions of the world. Improving the energy efficiency of resource extraction processes at any stage of the development of oil and gas fields is a priority. It is important to tactically and strategically plan all oil recovery technologies as early as at the initial geological study of the field. At different stages of field investigation a variety of techniques are being used for oil extraction modelling: physical, mathematical, geological-statistical. Special attention is given to the use of constantly operating geological and technological models for exploration and development control. Two example pilot projects for the Ural foredeep reef carbonate deposits in Russia and for the Mishrif formation at Zubair field in Southern Iraq justify prospectivity of comprehensive technology development of hydrocarbon exploration and production and have real life value. Suggested technical and technological solutions as use of existing facilities for gas injection, resuscitation of old wells, application of modern improved oil recovery techniques are aimed to reduce capital costs, create adequate development system which will allow to increase oil recovery on the depleted oil fields, increase work efficiency of gas distribution system during seasonal peaks of gas consumption.
-
-
-
Logging While Drilling Via Autonomous Sonde
Authors A. Kepic, C.J. Dupuis, G. Stewart, B. Wilkinson, A. Greenwood and A. PodolskaSummaryWe present a method of geophysical logging while tripping drill rods to produce logs similar to wireline logs. The process is autinmous in that it does not require any significant changes by the driller and does not requie any modifications to the drill rig. Using starting depth, rod length, and sensors on the sonde a geophysical log can be created when the drill rods are retreived upon hole completion. Thus, thi smethodology is very suitable for slimhole and diamond drilling methods that do not case teh completed hole. Such holes often collapse and are too expensive to log via wireline logging.
-
-
-
An Innovative Approach to Select Core Point in Challenging Environment Using the GWD&trade - (Gas While Drilling) Methodology
Authors A. Zaidi, C. Carugo, R. Pietrogiovanna and M. AliSummaryCore point selection plays vital role to ensure that cores are cut in best part of reservoir to fulfill objectives requested during well planning. Different methodologies are applied to select coring point. Depending on geological environment, these approaches reflect criticalities as rig time, offset of LWD tools, absence of markers etc. Here an innovative approach based on analysis of mud gas shows using GWD™ methodology is described. This methodology consists in computation of several ratios of hydrocarbon mixture (C1 to C5) continuously extracted from mud and monitored at rig site. A successful case history from a well recently drilled in Bhit field, Pakistan is presented. In this case, absence of drilling parameter changes and specific GR marker into thick shale sequence above reservoir does not allow proper identification of coring point. Gas data from two reference wells were analyzed and distinctive gas ratio trends between shale sequence and coring target were established, both qualitatively and quantitatively. After application of QC criteria, same trends were recognized in new well and coring point was selected even before scratching level of interest. Further confidence of quantitative aspects of methodology can lead to refine coring point selection, significantly saving rig time and costs.
-
-
-
Multi-component 3D Seismic - A Successful Fracture Characterization in Algeria-Processing Challenges in Noisy Environment
Authors V. Belz, M. Donati, J.L. Piazza, S. Baillon, D. Marin, A. Rollet, H. Toubiana, J. Castro, C. Gordillo, A. Bouheouira, T. Belhouchet, A. Belbachir and M. RahalSummaryMulti-component recording in land environments usually suffers from high contamination by surface waves, together with low-frequency content. This, combined with severe problems of receiver statics and shear-wave splitting, can make the processing so challenging that the PS data provide a disappointing final result compared to PP data. However, it doesn’t need to be so: in this paper we show that a high level of noise in the raw gathers, doesn’t prevent us from obtaining final images as good as (if not better than) the more conventional PP datasets, provided that the processing sequence is carefully tailored to address this issue. We describe the main steps of the PP and PS-wave processing sequences, with a special emphasis on noise removal, and a PS-wave azimuthal anisotropy study at deep targets made possible by the cleaned-up and signal preserved pre-stack gathers.
-
-
-
Multi-component 3D Seismic - A Successful Fracture Characterization in Algeria-Interpretation of Faults and Fractures
Authors J.L. Piazza, M. Donati, F.D. Martin, J. Castro, C. Gordillo, A. Bouheouira, T. Belhouchet, A. Müller, E. Ramia, S. Baillon, D. Marin and V. BelzSummaryThis paper describes the structural interpretation and the anisotropy analysis performed to characterize the fracture network using 3D-3C seismic data acquired as part of a 67km2 pilot survey in the Tin Fouyé Tabankort-West field located in the Illizi Basin in the Algerian Sahara. The target horizon corresponds to the Ordovician reservoirs composed of low porosity gas bearing sandstones located at a depth of approximately 1950 m below surface.
Well data show that the well performance is mainly controlled by the reservoir facies but faults and fractures are also thought to play a role in the gas production.
Based on a well controlled 3D-3C acquisition and a careful processing sequence of the PP and PS waves, this multi-component survey is proved to provide a better resolution of subtle faults and lineaments than the conventional 3D data seismic set available in the area even though the noise level remains slightly higher. Furthermore, the PS wave processing shows the evidence of shear wave splitting which is compensated to obtain an optimum radial component stack.
The PS wave anisotropy, found to be consistent with the faults and lineaments interpreted on the PP seismic data set and with the FMI information in the wells, is interpreted in terms of fractures.
The promising results of this 3D Multi-component seismic pilot provide an encouraging basis for wider 3D-3C acquisitions in areas where faults and fractures play an important role in the hydrocarbon production.
-
-
-
3D-PS Converted Waves – Solving 3D-imaging Challenges under Gas Clouds - Offshore Malaysia
SummaryIn offshore peninsular Malaysia there are strings of major hydrocarbon bearing fields which are affected by shallow gas clouds. This poses a major problem in imaging using the P-wave data from conventional streamer or OBC 2C surveys which suffer from frequency dependent attenuation, multipathing, scattering, internal multiples, velocity inversions and mode conversions due to the gas charged sediments. 2D–4C data is proven to be useful in areas affected by shallow gas where 2D-PS-wave imaging provides clearer image as compared to 2D-P-wave imaging. Imaging of 3D-PS-converted-wave data presents its own unique challenges which discourage companies from processing the converted wave component of 3D–4C-OBC data. Through this case study we showcase three processes which have brought about significant improvements in the 3D PS-wave time-imaging and outline the results of 3D-PS-PSDM depth-migration, rendering the data to be highly useful for interpretation and inversion work inside the gas cloud affected area.
-