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78th EAGE Conference and Exhibition 2016
- Conference date: May 30, 2016 - June 2, 2016
- Location: Online
- Published: 30 May 2016
981 - 1000 of 1034 results
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Characterization of Lower Cretaceous Clastic Wedges in the Southwestern Barents Sea Using Seismic Attributes
Authors J. Iqbal and A. EscalonaSummaryDepositional environment and reservoir properties of the Lower Cretaceous clastic wedges in the southwestern Barents Sea are poorly understood due to very few well penetrations as it is not the main target for exploration. In general, few technical discoveries have been made until recently, where two main discoveries in the southern margin of the Loppa High were made bringing back attention to the Lower Cretaceous wedges. In general, these wedges have been previously interpreted as deep marine basin floor fans by some researchers and as shallow marine deposits by others. These interpretations were based on very limited core data, well logs and seismic available from the area. Seismic attributes are very helpful in the absence of core data which is the key to interpret depositional environments. The main objective of this study is to define seismic facies that can be correlated with geological facies and reservoir properties by looking at 2D and 3D seismic surveys and various seismic attributes. Preliminary observations of the seismic data give indications of transitional environments (e.g. deltaic, strand plain) to deep marine environments for the wedges which confirm both previous interpretations. The seismic facies can be correlated with previously interpreted depositional environments, thus reservoir properties.
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Early Cretaceous Basin Margin Development in the SW Barents Sea, Norway
Authors D. Marin and A. EscalonaSummaryWe analyzed an extensive data set of 2D and 3D seismic and well data from the SW Barents Sea, which allowed us to classify the basin margin geometry during the Early Cretaceous. An erosional margin transformed into a progradational margin was identified in areas affected by a Late Jurassic-Early Cretaceous rift event. Long-lived canyons feeding fans were recognized in those types of margin. Furthermore, a progradational margin was interpreted, where large incisions were not recognized, but thin bottomsets interpreted as submarine fans were identified. Additionally, a transition between delta/shoreline scale clinoforms to shelf-slope scale clinoforms was described. Those results have implications for the understanding of the distribution of coarse-grain sediments and for the paleogeography.
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Combining Supervised and Unsupervised Method with Expert Knowledge for Seismic Facies Analysis in SeisAnfis Software
Authors S.H. Hadiloo and H. Hashemi ShahdaniSummarySeismic facies analysis is a technique to map spatial changes of lithology based on some characteristics or attributes extracted from seismic data. There are two supervised and unsupervised schemes for classifying seismic facies. Each of these two methods has some advantages and disadvantages for this purpose. Combining these methods along with adding expert knowledge can produce better result. In this study we introduce a software, called as SiesAnfis, that combines Adaptive neuro-fuzzy inference system, unsupervised clustering method, and expert knowledge to obtain seismic facies. Application of the software on a real seismic data set acquired over a south Iran oil field shows more accurate result compared to supervised ANFIS algorithm.
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Development of Plug-in for Eigen-structure Based Coherence and its Application of 2-D and 3-D Seismic Data
By A. DasSummaryCoherence measure applied in 2-D and 3-D seismic data has been used popularly for structural and stratigraphic mapping to delineate structural and stratigraphic discontinuities like faults, pinch-outs, unconformities etc. The 3 major algorithms to find coherency are based on cross-correlation, semblance and Eigenvalue decomposition of data co-variance matrix respectively. The present paper gives the workflow to calculate coherence by using concept of Eigenvalues. Subsequently, this algorithm is tested on a small seismic data set to check the applicability of the algorithm. Further, the algorithm is integrated within an interpretation software as a plug-in to be used for commercial and academic purposes. Finally, the plug-in is tested on real data and a comparative analysis is done between the obtained result and result from already existing semblance attribute.
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Fracture Characterization Based on Coherence and Bidimensional Empirical Mode Decomposition
Authors J.W. Zhang and H.D. HuangSummaryFracture is significant in fractured reservoirs. It’s crucial to estimate the fracture features in fractured reservoir exploration. The coherence method that measures the similarity degrees between multichannel data could depict the fractures via the seismic signal variation anomalies. As a distinctive time-frequency analysis method, EMD has a good adaptivity and time-frequency resolution. We propose a novel method combining coherence with BEMD to reveal different scale of fractures. Firstly, the seismic coherence data is obtained via the 3rd generation coherence method. Then the data is decomposed into different frequency band data with the BEMD method. According to the application for the real seismic data from a typical fractured reservoir, it is effectively proved that the method we propose is feasible to reveal different scale of the fractures.
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Investigation of Gas Flow in Shale Gas Reservoirs in the Transition Regime
Authors C. Christou and K. DadzieSummaryShale and tight gas reservoirs consist of porous structure with diameter of pores in the range of some mm to μm. In these scales, pores diameter become comparable to the gas mean free path. Flow in such structures fail often in the transition and slip flow regime. Standard continuum fluid method such as the Navier-Stokes-Fourrier set of equations fails to describe flows of these regimes. Kinetic theory such as the Boltzmann equation must be adopted. Here, we present a Direct Simulation Monte Carlo study of a 3D porous structure in an unlimited parallel simulation and we describe the gas properties. The three-dimensional geometry was obtained using a microcomputed –tomography (micro CT) scanner with a resolution in the scale of some μm. We present results at different Knudsen numbers and compare them with other continuum methods. In addition the method is also examined in convectional gas reservoirs and compared with unconventional one. Our findings demonstrate that significant differences appear in gas properties depending on the method that it’s been used and the Knudsen number. In lower Knudsen number the methods show similarities, while in transition and slip flow regime different results between Navier-Stokes-Fourrier and Direct Simulation Monte Carlo have been gained
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An Innovative Approach to Predict Behavior of Shale Plays by Combining Geomechanical and Capacitance-Resistance Models
More LessSummaryWith depleting conventional oil reservoirs, shale oil holds great potential in meeting the global future energy demand. Modelling these unconventional reservoirs require an accurate characterization and representation of the reservoir, while accounting for the formation anisotropy of the formation. This paper presents an integrated approach involving a Capacitance-Resistance (CR) model along with the geomechanical model for the shale oil reservoir based on field characteristics. After calibrating successfully with core measurement data from the published literature, the model is tested against data for other shale oil fields. The proposed CR Model could be programmed to determine any physical parameter using certain behavioural quantities. The required algorithm was developed for the model utilizing professional programming software. The basic principle here was the conversion of standardized physical parameters into digitally processed outputs. Finally, the CR model was then run in predictions in order to optimize the reservoir management strategy. Thus, an integrated reservoir modeling approach based solely on historical production data is presented for shale oil reservoirs. This would surely help reduce the human effort and time involved in reservoir simulation for fields involving large number of wells.
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Polymer Enhanced Gas Production from Methane Hydrate Reservoir
Authors M. Agrawal, G. Bhargava and J. SangwaiSummaryQuest for “Green Energy” has accelerated the exploration activities around the world. Unconventional resources are treated as potential energy source of the century, gas hydrate having a large amount of methane trapped in form of hydrates are widely available in Arctic region and Oceanic sediments. Efforts are required to understand the potential of these unconventional resource and ways of exploiting it in an economical way and with limited footprint.
Makogon (1981), showed the capability of chemical enhancers by increase in gas production at the Messoyakha field. Sloan (1992) has also suggested the use of enhancers (inhibitors) in gas production.
Our work will deal with series of experiments to determine the effect of polymer (Polyethylene Glycol, PEG) at varying molecular weight and constant mass fraction to study the effect of inhibition on gas hydrate. Through this it has been observed that the lower molecular weight of PEG (Polyethylene Glycol) will show larger inhibition than PEG of higher molecular weight (PEG 200 > PEG 400 > PEG 600). Also that polymer flooding into hydrate reservoir increases the decomposition rate over the pressure drive mechanism.
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A Simulation Study for Optimum Production Strategy in Small Size Tight Gas Reservoirs
More LessSummaryTight gas reservoirs represent a significant portion of natural gas reservoirs worldwide. Particularly, production at economical rates from tight gas reservoirs is very challenging due to the very low intrinsic permeability. Resource triangle describes how different is to explore and produce from unconventional reservoirs as compared to conventional reservoirs. As moving downward in resource triangle, unconventional reservoirs become larger and difficult to exploit, there is a need for more advanced technology to explore them.Specifically, the tight gas reservoirs generally do not allow flow gas to surface at commercial rates, unless the well is efficiently completed and stimulated using advanced technologies. With the advent of modern reservoir simulators, the studies involving reservoir models are gaining importance, providing better understanding of production behaviour of tight gas reservoirs.
The prime aim of this paper is to consider the application of hydraulic fracturing and horizontal drilling in small size tight gas reservoir by taking into account the effect of well completion and well type. comparative study of different cases shows that for small size tight gas reservoir, horizontal well with multi-stage perforations is enough to produce this reservoir economically. There is no need to do multistage hydraulic fracturing for small reservoirs.
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The Impact of Broadband Wavelets on Thin Bed Reservoir Characterisation
Authors E. Zabihi Naeini, M. Sams and K. WatersSummaryBroadband re-processed seismic data from the NW Shelf of Australia were inverted using a standard approach to wavelet estimation. The inversion method applied was a facies-based deterministic inversion where the low-frequency model is a product of the inversion process itself, constrained by input trends, the resultant facies distribution and the match to the seismic. The results identified the presence of a gas reservoir that had recently been confirmed through drilling. The reservoir is thin, with up to 15 ms of maximum thickness. The bandwidth of the seismic data is approximately 5–70 Hz and the well data used to extract the wavelet was only 400 ms long. As such there was little control on the lowest frequencies of the wavelet. Wavelets were then estimated using a variety of new techniques that attempt to address the limitations of short well-log segments and low frequency seismic. The revised inversion produced similar results but showed greater continuity and an extension of the reservoir at one flank. These differences could be traced back to the low frequency component of the inversion results and suggest that subtle variations in the low frequency component of wavelets can have an impact on seismic reservoir characterisation of thin beds.
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Different Methods of QC the Low Frequency Content of Broadband Data for Reservoir Characterisation
More LessSummaryBroadband seismic data becomes more common in the industry and acknowledged to improve the quality of reservoir characterization. Seismic inversion is widespread to support quantitative interpretation and its results are used within different areas from exploration to development. Extended seismic bandwidth allows reducing or even neglecting the dependence for seismic inversion results from well-driven low frequency model. More so, it’s very important to assess the quality of such low frequency content prior any reservoir characterization workflows applied.
In the current study it is suggested to discuss the different approaches to do a quality control of the low frequency content of broadband seismic data and associated velocity volume.
The discussed tools to perform both qualitative and quantitative QCs are: (1) visualization of seismic sections filtered with different high cut filters; (2) comparison of Intercept-Gradient crossplots for conventional and broadband seismic data, e.g. how it affects S/N ratio, stability of Gradient estimation; (3) comparison of different seismic data-driven low frequency trends to well observations and low frequency (low-pass filtered) seismic content; (4) comparison of bandpass filtered versus broadband seismic inversion results, e.g. sections, slices, inverted curves at well locations, blind well tests; how it affects resolution, continuity and matches to well data/observations?
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A state-of-the-art MEMs-based 3C Seismic Landstreamer for Various Near-surface Applications
Authors A. Malehmir, B. Brodic, M. Dehghannejad, C. Juhlin and E. LundbergSummaryWithin a large academia-industry consortium we have developed a unique state-of-the-art consisting of 100-3C MEMs-based sensors seismic landstreamer for various near surface applications and particularly for urban underground infrastructure planning projects. The streamer has been tested and evaluated in several places against plant-type geophones and the same type MEMs sensors but planted and for the planning of several major tunnelling projects inside and outside Sweden. When compared to plant-type geophones in a highly electrical noisy environment, the streamer sensors illustrated their potentials in being uncontaminated and superior to its predecessor geophone-based streamers. Being GPS-time stamped and sampled, it allows the streamer data to be merged with wireless data operating in a passive mode further overcoming some of the challenges encountered in complex urban and geological environments. Here, we present the streamer and its characteristics and examples of data and results obtained from it. In particular, we present results from a survey comprising of 25 profiles of about 7.5 km long in total and a surface-tunnel experiment where the streamer data were crucial to recognize mode-converted signals from fracture systems intersected in the tunnel.
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9C seismic data acquisition for near-surface applications: recording, waveform reciprocity and 4C rotation
Authors C. Schmelzbach, D. Sollberger, S.A. Greenhalgh, H. Horstmeyer, H. Maurer and J.O.A. RobertssonSummaryMulticomponent seismic data allow the study of shear (S) waves, which is of great interest to characterize, for example, anisotropy. We present a 9C seismic data analysis workflow that involves the acquisition of multicomponent seismic data using a sledgehammer striking a prismatic wedge as vectorial seismic source and 3C receivers. Inclined impacts on the two opposing sides of the wedge are rotated into a vertically-and horizontally-directed source. Advantages of this source are the simultaneous recording of horizontally-and vertically-directed sources with uniform coupling. Re-orienting the wedge allows acquiring data with orthogonally-oriented horizontally-directed sources. A 4C rotation of the two source and two receiver horizontal components allows then determining, for example, the apparent arrival direction of two orthogonally-polarized direct S-waves, which may differ from the source-receiver direction. While applied here to find the arrival direction of the direct S-wave, our workflow can also be used to study anisotropy through analysis of S-wave splitting.
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Unconventional low-impact methods to obtain near surface S-wave velocities
Authors F. Martini, J.T. Doherty, R. Davi, B. Cullen and J. MonganSummaryA poor characterization of the near surface in most land seismic surveys is a major limitation for imaging deeper reservoirs, especially in areas of complex overburden. This classical topic has been a research subject for decades, and several methods have been proposed to solve this problem in a cost-effective way. There are many different techniques we conventionally use to explore these velocities such as LVL and Uphole surveys. However such methodologies can be costly, time consuming and may have a significant environmental footprint. In this work, we show results from two different unconventional methods to provide near surface S wave velocity information while reducing the costs and the environmental impact more conventional methods might incur. We tested both the use of i) Vibroseis Attribute data (VAPS data) and ii) passive recording of ambient noise, to retrieve shallow S-wave velocities. Results were benchmarked against the traditional methods with great success.
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A Multi-scale Approach to Acoustic Full Waveform Inversion in 2D
Authors A. Akhriev, S. Moore and S. ZhukSummaryFull waveform inversion presents a number of algorithmic and computational challenges. Besides the bottlenecks associated with storage, communication and processing of large-scale system matrices, the key problem is that numerous local minima of the objective function make it hard to find a good solution even in the 2D case.
We tackle this problem with multi-scale simulation, where the novelty of our approach follows from multi-scaling coupled with dimensionality reduction. Compared to the traditional methodology based on regularization (which keeps problem dimensionality the same), the approach presented in this study is computationally more efficient yet less prone to local minimum. In this paper, we propose a solution to the inversion problem in 2D. The key issue in solving the inversion problem is how to avoid local minima in a reasonable time, given the often limited computational power. Multi-scaling appears to be the right way to tackle curse of dimensionality and numerous local minima. Our approach demonstrates novelty both in terms of algorithm design and parallel distributed implementation.
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VSP Monitoring for CO2 Migration Tracking in Fractured Rock Massifs
Authors M. Humphries, J.A. Marin Vidal and J.C. de DiosSummaryThe suitability of the geological formations for use as a CO2 storage site must be determined through detailed characterization and assessment of the potential storage complex and surrounding area. At Hontomin in Northern Spain, this is a deep saline aquifer in a carbonated and fractured rock mass. It is necessary to check continuously the carbon dioxide displacement around the injection well, to analyse the potential migration pathways and build the dynamic model in a fractured media. The VSP technique, improved with permanent devices located inside the wells, could be the solution for the objective described. Geophone and DAS VSPs are compared and comparisons are also made between the recorded data and images from the four source positions used in the DAS VSP campaign. The imaged DAS VSPs are promising.
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Production Logging - A Fiber Optics Way
Authors E. Lee, L. Yang, C. Mascagnini, A. Kshirsagar, K. Gohari, H. Jutila, A. Chattopadhyay and A. GryaznovSummaryFiber optics has shown value as surveillance tool when installed as part of the completion, enabling engineers to optimize artificial lift, production strategy, field development, etc. However the value of the fiber optics for logging application has yet to be fully realized.
The authors will go through several applications where fiber optics provide a greater insight compared to the various production logging suites.
The three applications of using fiber optics as a production logging tool revolves around production and injection profile, diagnoses of the well conditions upstream of the completion, and stimulation treatment.
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Understanding the Value of What We Measure
Authors A. Kshirsagar, A. Chattopadhyay, C. Mascagnini, K. Gohari, H. Jutila and A. GryaznovSummaryInwell measurement of rates and ratios do not allow operators to proactively control flow into the well. For intelligent fields there is a growing need for tools that enable engineers to ‘see’ further into the reservoir in order to adjust and/or change the flow control strategy as required. From a reservoir management perspective the most value can be achieved when implementing intelligent flow control systems coupled with surveillance tools. Hence, this study presents a way of defining a fit for purpose surveillance strategy that can be coupled with active flow control systems that facilitates the optimisation of the recovery efficiency.
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Restoration and Validation of an Autochthonous Salt Dome - Lessons from the Butch Discovery, Offshore Norway
Authors H. Anderson, A. Hetland Olsen, E. Macaulay and P. McCaffreySummaryKinematic restoration has been widely used to assess the validity of geological interpretations and constrain the timing and nature of structural development. The techniques attempt to transform a 2D section and/or 3D geological model from one deformational state to another while conserving bed length, area or volume. This approach has proven particularly effective for unraveling the development of salt provinces, where the deformation associated with salt-related movement can add significant structural complexity.
Traditional restoration involves a combination of backstripping, restoration of horizons to a regional level and removal of across-fault offsets. Salt, which often masks deformation on seismic reflection surveys, cannot be restored directly using these techniques and is, therefore, assumed to flow out of the model as the overlying sedimentary basins develop. In this paper the principals behind forward modelling and restoring a salt diapir are detailed and evaluated with respect to the development of an active salt dome adjacent to the Butch Discovery, offshore Norway (Centrica (operator, 40%), Suncor Energy (30%), Faroe Petroleum (15%), and Tullow Oil (15%)). The presented results consider the impact and significance of different kinematic unfolding algorithms and the importance of out-of-plane movement when working in two and three dimensions.
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Evaporites in a Rift Setting – The Alpine Halite-mudrock-polyhalite Tectonite (Haselgebirge Fm., Eastern Alps, Austria)
Authors C. Leitner, S. Wiesmaier, M.H. Köster, H.A. Gilg and F. NeubauerSummaryThe salt of the late Permian Haselgebirge Fm. exposes large proportions of mudrock. The mud was trapped in a basin without a connection to the open sea. The mudrock comprises earthquake structures. An enrichment of magnesium minerals (mainly magnesite and chlorite) and “deep water” anhydrite point to a residual brine basin. Pre-saturation happened in the surroundings represented by the gypsum/anhydrite deposits of the Haselgebirge Fm. The basin itself was probably narrow (tens to fifties of kilometers), but elongated (>1000 km). Igneous rocks with an intermediate chemistry are in sedimentological contact with the salt. A late syn-thinning stage is assumed for the deposition of the Haselgebirge Fm., due to low diapiric activity and the paleogeographic arrangement of the salt rocks in the context of the Northern Calcareous Alps. Heating was probably enhanced by the overlapping processes of orogenic collapse of the Variscan mountain belt and the formation of a rift. The first occurrence of polyhalite [K2Ca2Mg(SO4) 4.2H2O], which represents a mineralogic peak of the diagenetic history coincides with the final opening of the Meliata Ocean.
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