- Home
- Conferences
- Conference Proceedings
- Conferences
EAGE 2020 Annual Conference & Exhibition Online
- Conference date: December 8-11, 2020
- Location: Online
- Published: 08 December 2020
41 - 60 of 368 results
-
-
A P-Cable Time-Lapse Seismic Repeatability Study in the Gulf of Mexico
More LessSummaryThe term “P-Cable” refers to a high-resolution marine streamer acquisition system that uses short densely-spaced streamers to provide 3D seismic data with higher temporal and spatial resolution than conventional marine streamer acquisition. It is a containerized system that can be deployed at short notice and relatively low cost, making it attractive for time-lapse seismic surveying. Its small dimensions enable accurate repetition of source and receiver locations and provide greater flexibility and safety in obstructed areas. Two pairs of time-lapse (4D) repeatability test lines were acquired in the Gulf of Mexico in 2014, and these were processed in 2019. The data presented many challenges including strong cable noise and variable streamer depths. Nevertheless the results exhibited low NRMS difference values and low residual energy on 4D difference seismic sections. This demonstrates that the acquisition system can provide high-quality time-lapse seismic data in areas where the reservoir can be adequately imaged by short-offset, low-fold, small-source seismic data. Recent upgrades to the system mitigate many of the problems encountered and should provide further improved time-lapse seismic data. Several hydrocarbon fields are currently monitored using this method.
-
-
-
Influence of Label Conditions on the Effect of Deep Learning Inversion
More LessSummaryLabel and algorithm are two main factors that influence the effect of deep learning inversion (DLI). Most present researches focus on optimizing algorithms, and pay less attention to how the labels affect the inversion effect, which results in that the application effects of the same algorithm varying with the application regions. This article highlights the importance of label conditions on the effect of DLI. The comparison of inversion results performed with 4 different label sets indicates an ideal DL inversion requires a large number of high-quality and large-diversity labels.1) Label quality is the most important factor, for it directly determines the correctness of inversion results. 2) The increase in both quantity and diversity of the labels is very effective for improving the inversion result, and the diversity is relatively more critical. 3) The better the label structure matches the geological pattern, the better the inversion results are. The research demonstrates that forward modeling based on well interpolation model is an effective method for label augmentation. In order to take full advantage of deep learning, we should integrate it with classic geophysical methods and make them complement each other.
-
-
-
Fast Elastic Wavefield Reconstruction in a Local Region by Modifying Any Modelling Code
Authors L.E. Jaimes-Osorio, A. Malcolm and P. ZheglovaSummaryThe finite-difference (FD) method is a key tool in geophysics, where it is used to model seismic wave propagations. Often, the region of interest is reduced to small areas. Thus, many methods have been developed to manipulate the source wavefield efficiently to reconstruct the synthetic wavefield locally. However, there are few implementations in the elastic domain, where it is specifically shown how the injection and reconstruction of wavefields should be done. In this study, we show the implementation of multiple point sources method to reconstruct elastic wavefields inside an elastic local domain using a finite difference method. We demonstrate the capability of the elastic wavefield reconstruction using the SEAM East-West 2D elastic model.
-
-
-
1D Laplace-Fourier Acoustic FWI for Near-Surface Characterization and Initial Velocity Model Building
Authors A. Kontakis, D. Rovetta, D. Colombo, E. Sandoval-Curiel, P.V. Petrov and G.A. NewmanSummaryAccurate characterization of the near-surface velocity model is often a prerequisite for effective migration. Refraction tomography may fail to produce a satisfactory velocity model in the presence of velocity inversions and requires accurate traveltime picking. Full waveform inversion (FWI) can overcome these issues, but often requires a good initial model or the presence of sub-5Hz frequencies in the recorded data, and its 3D implementations can be computationally costly. To address these challenges, we propose a 1D version of Laplace-Fourier acoustic FWI, building on the relative insensitivity of Laplace-Fourier methods to the quality of the initial model. The proposed method approximates locally the 3D medium by an effective 1.5D medium and inverts independently for local 1D velocity profiles, that can be upscaled to a full 3D velocity volume. The independence of the 1D inversions and the cylindrical symmetry exhibited by 1.5D forward modelling can be taken advantage of to produce an efficient, highly parallelizable implementation. The feasibility of the method is studied using a synthetic example, with encouraging results.
-
-
-
Fully Automatic Picking of Surface Wave Dispersion Curves through Density-Based Spatial Clustering
Authors D. Rovetta, A. Kontakis and D. ColomboSummaryRayleigh surface wave inversion can be used to characterize the near surface, which is a major task in desert environments due to the high complexity of the shallow geology. The inversion results depend on the accuracy of the dispersion curves extracted from the seismic measurements. This extraction is commonly obtained through manual picking which is time consuming, highly subjective and not feasible for modern large seismic surveys. In this work we introduce a novel and fully automatic method built on a density-based spatial clustering algorithm to pick surface wave dispersion curves in the frequency-phase velocity spectrum of the seismic gathers. The method was successfully tested on the SEAM Arid model synthetic dataset. The dispersion curves, extracted automatically using the proposed approach, accurately match the theoretical ones and produce results in very good agreement with the ground truth when inverted for the shear-wave velocity distribution. The presented method is currently under test with field data.
-
-
-
Research and Application of Prediction Method for Sweet Spots of Shale Gas Using Geophysical Data
Authors W. Xiujiao, C. Sheng, H. Pei, W. Nai, Y. Yadi, D. Chunmeng, H. Zijiao, W. Xing and L. XuanSummaryAs one of the most important procedures in shale gas exploration and development, sweet spots prediction is the preferred method for acquiring and maintaining high productivity and effective production of shale gas.
In this study, firstly, based on well log interpretation and rock physics analysis, the quantitative relationships between the elastic parameters and the evaluation parameters such as density and TOC, were established. Then, the planar distribution of some key reservoir parameters including TOC, high-quality reservoir thickness, brittleness and formation pressure were predicted through prestack inversion of all gathers. Finally, with the fuzzy comprehensive evaluation method, an evaluation scheme was proposed and the spatial distribution of sweet spots in the block was assessed. Based on this scheme and the regional distribution of sweet spots predicted by the seismic data, the Z block was divided into three classes. Class I and Class II as the sweet spots are mainly distributed in the east of the block, which are suggested to give priority to the development. This study can provide important guidance for the factory development of the block.
-
-
-
The Effective Elastic Properties for Transversely Isotropic Rocks with Randomly Orienting Inclined Penny-Shaped Cracks
More LessSummaryCracks have significant influences on the elastic properties of reservoir rocks, and the effects of crack properties (e.g., crack density, crack aspect ratio and crack orientation) on the elastic properties of rocks have always been the focus of petrophysics and seismic exploration. However, key to the accurate characterization of fractured reservoir is the development of rock physics models that better simulate real fractured reservoirs. Current models are not applicable to rocks with randomly orienting inclined cracks even though such conditions are frequently encountered in the Earth. We derive the theoretical models and simulate the elastic properties of fractured rocks with transversely isotropic background permeated by 3D inclined cracks and randomly orienting cracks, to demonstrate how the elastic properties of fractured rocks are affected by the properties of randomly orienting inclined cracks. The observed petrophysical models and the correlated crack properties and elastic properties have both theoretical and practical implications for insights into the effects of randomly orienting cracks on the fractured rocks and for inverting the crack properties of the fractured reservoirs. This will pave the way for the successful prediction of the elastic properties for rocks with TI background permeated by randomly orienting cracks.
-
-
-
Velocity Model Building Using Elastic Waveform Inversion on Multi-Component OBN Data in the Gulf of Mexico
Authors C. Perez Solano, R. Plessix, K. Bao, C. Perkins and M. KiehnSummaryIn presence of large elastic parameter variations, acoustic waveform inversion creates artefacts because the approach overfits the data with an inaccurate physical model. An elastic formulation is required to correctly account for the finite-frequency effects and notably the scattering that occurs inside the first Fresnel zone. Over the years, nodal acquisition has become more popular. In the waveform inversion context, it provides low-frequency, long-offset, and full-azimuth data that are very relevant to recover the low-to-mid wavenumber information of the earth parameters. Moreover, with offshore nodal acquisition, not only the pressure field is recorded but also the three particle-displacement or velocity fields. The noise does not have the same effects on the different recording component due to its directionality. Using a nodal acquisition for the Gulf of Mexico, we present the elastic inversion results obtained with the hydrophone and vertical geophone components. We discuss the relevance of considering the vertical geophone component in velocity model building.
-
-
-
Assessment and Application of Present-Day In-Situ Stress Field Within Deeply Buried Tight Reservoir of Tarim Basin
More LessSummaryConstructing a suitable method to better understand the present-day in-situ stress field within deeply buried tight sandstone reservoir under complex geological conditions is extremely important in the Tarim Basin. In this study, one-dimensional (1D) geomechanical modeling and three-dimensional (3D) heterogeneous stress field simulation were carried out, and the well trajectory optimization were analyzed. Taking the KS 10 gas reservoir of KS gas field in the Kelasu structural belt as an example, the results show that the in-situ stress magnitudes within deeply buried tight sandstone reservoir in the Kelasu structural belt are generally high. The relationship of horizontal maximum (SH), minimum (Sh) principal stress, and vertical stress (SV) is SH>SV>Sh, showing a dominant the strike-slip faulting stress regime. The direction of the SH is generally N-S-trending. The research on the heterogeneous rock mechanical parameters is expected to improve the accuracy of present-day in-situ stress prediction in deeply buried tight reservoirs. The result of present-day in-situ stresses provide a reasonable reference for well trajectory optimization to reduce complex accidents and avoid potential engineering risks, helping increase the oil and gas production and improve the drilling speed.
-
-
-
Automatic Fracture-Vug Extraction from Imaging Logging Based on Incomplete Path Opening Operation and Cluster of Sinusoid
More LessSummaryIn this study we provide a systematic workflow of fracture-vug extraction and reconstruction for electric well logging image preprocessing for the purpose of accurate quantitative assessment of fractures and vugs reservoirs. It includes first step of identification of fractures and their edges by incomplete path morphologic scheme, and the second step of pattern recognition of the electric well logging images through a correlation with a family of sinusoidal functions prepared for the picking up of fracture parameters for high dip fractures and the Hough transformation for low dip fractures. Then the statistical step has been applied to parameters extraction for the reservoir description. With the suitable combination of parameters can we derive complete fractures and vugs that may have admissible missing pixels by the incomplete path opening operation. The cluster of sinusoid can make up for the deficiency of Hough transform in the extraction of high dip angle fractures and incomplete fractures, and overcome the weak robustness of Hough transform to noise.
-
-
-
Obtaining Sub-Metre Vertical and Spatial Resolution from Seismic Data - the Clair Experience
Authors D. Davies, C. Allinson and M. HigsonSummaryIn 2019, BP acquired a site survey over the proposed Clair South Platform location with the aim of achieving sub 1m vertical and spatial resolution over a 1km x 1 km area. The need for such resolution was to optimally image the very shallow sub-surface such that piling issues during installation were minimised via the avoidance of boulders and shallow glacial features. In this paper we discuss the 2D field trial in 2018 including several lessons learned that were then applied to the full 3D survey in 2019. The final outcome was a high resolution image over the area that matched our resolution ambitions and exceeded our expectations in terms of abundance of features imaged, particular our view of soil conditions, which allowed us to have confidence in moving the proposed location and by doing so, we have significantly reduced engineering risk.
-
-
-
Automating Velocity Model Building Using Monte Carlo Simulations - A West African Case Study
More LessSummaryBuilding velocity models for depth imaging can be time-consuming and regularly requires manual intervention. The workflows tend to be ‘stop-go’ chained processes. An approach using pseudo-randomness can be used to build a velocity model, mitigating some of the inefficiency challenges associated with traditional velocity model building. Monte Carlo simulations use random sampling to resolve problems where the solution may be insufficiently defined. Using a Monte Carlo approach for velocity model building firstly requires an understanding of how the data quality impacts the model, prior to creating a population of models to invert. A statistical analysis loop of the inverted population of models, followed by numerous repeated cycles, enables a level of automation in velocity model building. The protracted chained approach of classical model building can be replaced by parallelized compute intensive methods to achieve an accurate velocity model in a reduced timeframe. In this abstract we demonstrate the benefits for both quality and time, of weight of statistics and automation when using a Monte Carlo simulation for velocity model building.
-
-
-
ML-Misfit: Learning a Robust Misfit Function for Full-Waveform Inversion Using Machine Learning
Authors B. Sun and T. AlkhalifahSummaryMost of the available advanced misfit functions for full waveform inversion (FWI) are hand-crafted, and the performance of those misfit functions is data-dependent. Thus, we propose to learn a misfit function for FWI, entitled ML-misfit, based on machine learning. Inspired by the optimal transport of the matching filter misfit, we design a neural network (NN) architecture for the misfit function in a form similar to comparing the mean and variance for two distributions. To guarantee the resulting learned misfit is a metric, we accommodate the symmetry of the misfit with respect to its input and a Hinge loss regularization term in a meta-loss function to satisfy the triangle inequality rule. In the framework of meta-learning, we train the network by running FWI to invert for randomly generated velocity models and update the parameters of the NN by minimizing the meta-loss, which is defined as accumulated difference between the true and inverted models. We first illustrate the basic principle of the ML-misfit for learning a convex misfit function for travel-time shifted signals. Further, we train the NN on 2D horizontally layered models, and we demonstrate the effectiveness and robustness of the learned ML-misfit by applying it to the well-known Marmousi model.
-
-
-
Comparative Analysis of Attenuation Compensation Based on Time-Frequency Transform
More LessSummarySeismic waves are affected by wavefront diffusion and medium absorption during propagation, resulting in high-frequency energy attenuation and phase distortion, which will seriously reduce the resolution of seismic data. With the improvement of high-resolution processing requirements for seismic data, it is very important to obtain high-quality seismic profile by compensation processing. Seismic data are non-stationary signals, neither the spectral analysis nor the simple waveform analysis can accurately describe the time variant characteristics of the seismic waves. In order to better describe the time-frequency characteristics of the seismic signal, the time-frequency analysis method is used to process the seismic signal. Therefore, the compensation of seismic signal in time-frequency domain is considered. Geophysicists implement attenuation compensation based on Gabor transform and continuous wavelet transform(CWT), respectively. We generalize and implement the attenuation compensation method based on Generalized S transform(GST). Subsequently, we analyse the accuracy of three kinds of time-frequency domain compensation by numerical simulation. It is concluded from the error analysis that the compensation based on GST has higher accuracy. The real data shows that the resolution are significantly improved and the fine structure of seismic section is highlighted. It greatly improves the accuracy of the compensation processing of the real data.
-
-
-
Modelling of Air Flows in Pneumatic Seismic Sources
Authors B. Kuvshinov, S. Chelminski and S. RonenSummaryAir flows in a low-frequency pneumatic marine source are simulated. The modeling results agree with test data.
While the proposed approach is relatively simple, it is an improvement on conventional state of the art sources modelling methods.
It adequately captures the underlying physics and may be helpful to predict the behaviour of pneumatic marine sources and to facilitate their design.
-
-
-
Impact of Stress Regime on Shale’s Brittleness: Implications for Determining Suitable Hydraulic Fracturing Intervals
Authors P.P. Mandal, R. Rezaee and J. SaroutSummaryCost-effective hydrocarbon production from unconventional reservoirs relies on multi-stage hydraulic fracturing operations. Suitable shale intervals are usually identified on the basis of: (i) organic-richness; and (ii) mechanical brittleness to promote the creation of a multidirectional fracture network, and therefore a larger stimulated reservoir volume. The in-situ stress state notoriously governs shale deformation and fracturing processes at depth. In the Goldwyer shale formation (Canning Basin, Western Australia), existing well logs from the Theia-1 well are used to build a 1-D mechanical earth model through a brittleness analysis and direct validation with existing laboratory triaxial rock mechanics tests. A progressive transition with depth from a strike-slip (shallower intervals) to a hybrid faulting regime (deeper intervals) is inferred in the Goldwyer formation. The changing stress regime correlates with the estimated variation in dynamic elastic brittleness with depth. This analysis suggests a power law relationship between static Young’s modulus and deformational brittleness (B3). This power law function is then used to create a continuous brittleness profile along the well, across the entire Goldwyer formation interval. Based on this study, the G-III unit (1500m to 1590m in the Theia-1 well) of the Goldwyer formation is the most prospective for hydraulic fracturing operations.
-
-
-
Improving Field Development Efficiency Based on Integrated Asset Modelling Approach
By E. PadinSummaryThe successful implementation of Integrated Asset Modelling approach enabled to increase field development efficiency in solving long-term planning tasks and optimizing operational production processes is shown in this paper. Recommendations for Integrated Asset Models (IAMs) conceptual design depending on the stage of field lifecycle and modelling purposes are given. Based on the Company experience practical suggestions for IAMs creating and matching processes are proposed. The examples of real projects are presented where IAMs application allowed achieving economic efficiency.
-
-
-
Focused and Continuous Ultra-Light Seismic Monitoring: A Gas Storage Example
Authors E. Morgan, M. Garden, A. Egreteau, Y. Boubaker, K. Gestin and J.L. MariSummaryCommon appraisal methods for oil and gas reservoir often begin with 3D seismic and exploration wells. These technologies provide spatial recognition along with focused stratigraphy and subsurface resources content. Even though models and simulations predicts a reservoir dynamic, measuring this key component in time complements spatial technologies while providing relevant information regarding field optimization. Further intents to go towards continuous monitoring have demonstrated the capability for seismic to detect reliable short-term calendar 4D effects that would be missed by conventional 4D seismic. These techniques have proven efficiency yet remain expensive; this paper presents a new light seismic asset monitoring solution.
An ultra-light continuous monitoring method has been developed to focus on a specific “spot” location defined by reservoir engineer studies. To illuminate a given spot, a seismic spread, composed of one receiver and one source position, is defined by analysis of existing 3D seismic data. This procedure allows for a very high temporal density monitoring tool targeted at a specific reservoir location and is economically attractive.
This production case study gives further understanding about an active gas storage dynamic showing encouraging results for such a light asset monitoring tool and paves the way for focused and continuous seismic monitoring.
-
-
-
A Revitalized Broadband Processing Workflow for Over-Under Data: A Case Study from Offshore South Africa
Authors M. Matta, S. Joyce, A. Anantan, B. Msezane, P. Dekker and M. MmemaSummaryIn recent years, a key focus of discussion in the seismic industry has been acquisition and processing of broadband seismic, which is widely defined as seismic that has a high signal to noise ratio across a very broad band of frequencies. With ongoing developments in the technology available in the industry to deliver broadband seismic, recently there has been a shift in the industry from acquisition-based solutions to signal-processing based solutions. Significant advancements in signal processing have enabled reprocessing of data that was already acquired with particular broadband acquisition techniques. Herein we present a case study that illustrates the additional value that can be leveraged through reprocessing of existing over-under broadband data to obtain new geological insights and de-risk future hydrocarbon potential assessments.
-
-
-
Exact and Approximate Reflection Coefficients for a Vertically Fractured Layer
More LessSummaryWe consider the orthorhombic (ORT) model to characterize the vertically fractured medium and analyse the plane wave reflection coefficients for the ORT layer embedded into the ORT space. We decompose the exact reflection coefficients into a series expansion wherein the successive series terms correspond to different orders of intrabed multiples. Under the weak-contrast assumption, we derive the first-order reflection coefficient approximations for the ORT layer. The approximations are tested numerically and can give insights into the reflection responses.
-