- Home
- Conferences
- Conference Proceedings
- Conferences
80th EAGE Conference & Exhibition 2018 Workshop Programme
- Conference date: 10 Jun 2018 - 15 Jul 2018
- Location: Copenhagen , Denmark
- ISBN: 978-94-6282-257-3
- Published: 10 June 2018
81 - 99 of 99 results
-
-
Exploration Success Equation
By A.V. MilkovThere are several definitions of petroleum exploration success. Geological (or technical) success is defined as finding oil & gas accumulations. Commercial (or economic) success means finding oil and gas accumulations that result in financial profits. Another, less common definition is finding oil and gas accumulations that, on a portfolio basis, have total resource volumes and create total monetary value as predicted before the drilling. However, exploration companies commonly deliver exploration results that are not consistent with pre-drill predictions. For example, Rudolph and Goulding (2017) studied drilling results from ExxonMobil conventional exploration in 1994-2015 and found that delivered volumes were 27% larger than pre-drill predictions. On the other hand, the study of Lundin’s exploration on the Norwegian Continental Shelf (NCS) in 2011-2015 revealed that the company delivered volumes that were 45% below the expectation from the portfolio of 25 wells (Milkov, 2017).
-
-
-
Overconfidence and optimism in the oil industry: surfacing systematic biases and distortions in probabilistic practice
By G. KeithIn order to hold a meaningful discussion on the accuracy, or otherwise, of our probabilistic assessments, it is necessary to have a meaningful sense of what constitutes an accurate assessment. Pragmatically, this is equivalent to understanding how we can validate probabilistic statements regarding events against their outcomes.
-
-
-
Analogue play statistics for improved pre-drill risking: North Sea case study
By K. MyersThere is evidence that the industry is systematically over-estimating the commercial chance of success (CoCS) and volume especially in high risk plays. The bias in commercial risking and pre-drill volume estimation is not a new phenomenon and persists today. Analogue play statistics can help address potential bias by providing objective calibration and sense-checking of success rates and discovery sizes.
-
-
-
Addressing the causes of uncalibrated predictions & underperformance in oil & gas ventures
Authors M. Bond and P.D. CarragherPersistent biases affect the important work of estimating the range of uncertainty of oil and gas resources and reserves, the chance of success for a wildcat well, and the chance that an unconventional resource project will be successful. These biases result in chronic underperformance in the oil and gas industry as evidenced by predicted volumes that are overoptimistic; uncalibrated success rates, and poor economic results in unconventional projects.
-
-
-
Direct inversion of seismic reflection data
By P.B. HardyThe prominent inversion based methods we use to estimate velocity models of the subsurface using seismic data have practical weaknesses that limit their application.
-
-
-
Focusing conditions: a comparison between different Marchenko imaging strategies
Authors G.A. Meles, C. Reinicke, K. Wapenaar, J. Brackenhoff and J.W. ThorbeckeMarchenko imaging allows retrieving images from single-sided reflection measurements without artefacts due to internal multiples. A key step in Marchenko imaging is the retrieval of the so-called focusing function from the reflection measurements and a background model. The conventional focusing function obeys a point focusing condition, i.e. it focuses inside the medium of interest both in space and in time. Based on this focusing property one can retrieve up- and downgoing Green’s functions that are associated with a virtual point source or receiver inside the medium, which can be used for imaging. Recently, a new focusing function has been introduced that creates a plane wave instead of a point focus. Using the new focusing function one can retrieve medium responses associated to an up- and downgoing plane wave source or receiver inside the medium, enabling imaging based on plane wave sources. We compare Marchenko imaging using the conventional and the new focusing condition.
-
-
-
Wave-Equation Dispersion Inversion of Guided P Waves in a Waveguide of Arbitrary Geometry
Authors J. Li, S. Hanafy and G. SchusterWe present the theory for wave-equation inversion of dispersion curves obtained from guided P waves. The misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves, and the inverted result is a high-resolution estimate of the near-surface P-velocity model. This procedure, denoted as the wave equation dispersion inversion of guided Pwaves (WDG), is valid for near-surface waveguides with irregular layers. It is less prone to the cycle skipping problems of full waveform inversion (FWI) and can sometimes provide velocity models with higher resolution than wave-equation traveltime tomography (WT). The synthetic and field data examples demonstrate that WDG for guided P-waves can accurately reconstruct the P-wave velocity distribution in laterally heterogeneous media.
-
-
-
Understanding multiples in land seismic data
More LessThe limited success of wave equation based methods for multiple removal on land is likely due to a fundamental lack of understanding of the relevant multiple mechanism. Where are the strongest multiples generated? Are multiples mostly surface multiples, generated by reflection at the free surface? Or is it the base of the weathering layer that is the source of significant multiple energy, so that we should talk about interbed multiples instead? What is the relative contribution of interbed multiples to the total multiple energy? What is the role of elastic effects, in particular mode conversions? In this paper, we will discuss an attempt to advance our understanding of the multiple mechanism in a typical Middle East land setting. The basic approach is to combine a variety of techniques providing shallow subsurface information (shallow well logs, modal elastic inversion, elastic full waveform inversion, surface consistent deconvolution filters) to obtain a single consistent and detailed shallow model and to subsequently compare synthetic forward modeled data and actual field data to challenge various multiple mechanism scenarios.
-
-
-
Making acoustic and elastic internal multiple prediction work efficiently and without artifacts
Authors K.A. Innanen, J. Sun and A.S. IversonFor prediction and removal of internal multiples, inverse scattering series methods operate in situations where an accurate velocity model and generator picks are absent or difficult to determine. The technology has produced remarkable results, however, its regular, practical, and value-added use requires algorithms which simultaneously incorporate (1) flexibility, in the sense of domain of computation; (2) non stationarity, in selection of the searchlimiting parameters associated with the method; (3) extension to elastic/multicomponent data; and (4) correct ordering of sub-events in input data preparation, even in the presence of complex wave phenomena such as multiple elastic conversions. In this paper we summarize the development of an integrated set of inverse series prediction algorithms that are designed to address these issues and push forward the practical applicability of this type of technology.
-
-
-
A single-sided representation for the homogeneous Green's function, accounting for all multiples
Authors K. Wapenaar, J. Brackenhoff, J. Thorbecke, J. van der Neut and E. SlobThe homogeneous Green's function, i.e., the superposition of the causal Green's function and its time reversal, is traditionally represented by a closed boundary integral. This integral representation finds applications in holographic imaging, seismic interferometry and time-reversal acoustics. In principle these methods account for all multiples, but only when the medium is accessible from all sides. Here we discuss a single-sided representation of the homogeneous Green's function, which also accounts for all multiples, but which can be used when the medium is accessible from one side only. We indicate the application of this representation for seismic imaging, accounting for internal multiple scattering.
-
-
-
Applications of the Marchenko method in the data domain
Authors J.A. Brakenhoff, M. Stating and L. ZhangThe Marchenko method has been proven on synthetic data, but there are few quality field data examples. We show that by slightly adjusting the Marchenko method the multiples in an image with a complex salt overburden can be greatly reduced. We also show that on a field dataset the homogeneous Green's function in the subsurface can be retrieved, consisting of a direct field as well as several orders of multiples.
-
-
-
An overview of Marchenko-based redatuming: past, present, (and future)
By M. RavasiMarchenko-based redatuming methods aim to produce full-waveform propagators from single-sided reflection data and an estimate of the subsurface velocity model. In this talk, I will first review various alternative approaches proposed in the literature and discuss how they differ from each other and from the original formulation of Wapenaar et al (2014). Using a common notation throughout, the key novelty of each method will be highlighted as well as their strengths and limitations with respect to application to field data. Finally, I will discuss the way forward, both in terms of implementation details (e.g., 3D) and theoretical advances (e.g., active role of multiples), that are the topics of current research in the community and can be seen as key enablers for a more widespread use of the Marchenko equation in geophysical applications.
-
-
-
Towards the prediction of internal multiples from thin layering by Marchenko
Authors R.F. Hegge, G.A. Meles and C.P.A. WapenaarThe presence of internal multiples in our data due to strong reflectors could inhibit or complicate the correct (quantitative) interpretation in particular when, after imaging, they cross reflectors or areas of interest. Commonly used internal multiple prediction and subtraction workflows deal with these kind of situations reasonably well. Unfortunately, situations exist whereby internal multiples are not ‘simply’ crossing events. For instance, a package of thin layers can produce a ‘cloud’ of internal multiples, which completely obscures deeper primaries as observed in a dataset acquired at or near the Arabian Peninsula. So far, all available workflows fail to handle this particular case. Note that when just the subtraction is not feasible, the separate imaging of the predicted internal multiples could still be of benefit to the interpretation process. With this case in mind, a collaboration project was initiated to evaluate Marchenko based internal multiple prediction for thin layering using a series of datasets from synthetic models in, mostly, blind tests. This abstract presents the first observations from the initial results.
-
-
-
Least-Squares Full Wavefield Migration
Authors S. Lu, F. Liu and N. CheminguiConventional seismic processing uses only primary reflections for imaging, and treats high-order reflected events (multiples) as noise. Separated Wavefield IMaging (SWIM) uses the downgoing pressure wavefield to exploit the extended illumination provided by surface-multiple energy, effectively converting all receivers into virtual sources. We present a Least-Squares inversion solution for depth migration of the full reflected wavefield that includes both primary and high-order reflected energy. Standard migration of primaries and SWIM are complementary and can augment the overall imaging results when they are combined correctly. Whilst full-wavefield migration (FWM) is able to jointly image both primary and high-order reflected energy, it cannot easily balance the contribution of each component, and also involves crosstalk due to the natural blending scheme. The Least-Squares full wavefield migration (LS-FWM) described here directly computes the earth’s reflection image in an iterative manner, thereby avoiding crosstalk noise. Successful applications to both synthetic and field data examples demonstrate that LS-FWM greatly improves the imaging illumination and resolution compared to conventional migration.
-
-
-
Non-Gaussian Linear Inversion of Reflection Seismic Data
Authors P.S. Christiansen, T.M. Hansen and H.J. HansenThe method of seismic inversion aims to estimate subsurface properties from seismic data, thereby providing us with a model of the earth. Often model parameters are assumed to be Gaussian distributed because it makes the inverse problem more tractable as it can be solved analytically by least-squares based algorithms (Buland and Omre, 2003).
-
-
-
Integrating Gradient Information with Probabilistic Traveltime Tomography Using the Hamiltonian Monte Carlo Algorithm
Authors A. Zunino and K. MosegaardSeismic traveltime tomography is a popular methodology used to infer the velocity structure of the subsurface (Cerveny, 2001; Nolet, 2008) which has been used across all the scales from near surface imaging to global seismology. In near surface seismology inversion for traveltime is employed to construct velocity models used for further processing of seismic data and crucial to correctly assess deep structures. Formally, the relationship between velocity and traveltime can be described by the eikonal equation (Nolet, 2008), a nonlinear partial differential equation describing the arrival time for a given velocity model as a function of position. Solving numerically the eikonal equation (Vidale, 1988; Podvin and Lecomte, 1991; Rawlinson and Sambridge, 2004) for a given source, provides the traveltime at all grid nodes at once, hence saving a substantial amount of computational time compared to the traditional ray-tracing approach.
-