DIP CALCULATOR TO EVENT TRACKER PLUG-IN FOR PETREL 2014 USER MANUAL
DIP CALCULATOR TO EVENT TRACKER PLUG-IN FOR PETREL 2014 USER MANUAL LARSEN AND TOUBRO INFOTECH LTD. 1 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. ABOUT THIS DOCUMENT This document provides instructions for the use of “Dip Calculator To Event Tracker” plug-in for Petrel 2014.1, including operation of the plug-in. COPYRIGHT NOTICES AND DISCLAIMERS “Dip Calculator To Event Tracker” plug-in for petrel is copyright of Larsen & Toubro Infotech Ltd. All rights reserved. © All rights including copyrights and rights of translation, reproduction etc. reserved and vested exclusively with Larsen & Toubro Infotech Ltd. No part of this user documentation may be reproduced, transmitted in any form or by any means or otherwise stored in a retrieval system of any nature without prior written permission of copyright owner. 2 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. TABLE OF CONTENTS 1 Introduction ............................................................................................................................. 4 2 Overview .................................................................................................................................. 4 3 Algorithms ............................................................................................................................... 5 3.1 3.1.1 Inline/Xline Slope Cube ............................................................................................. 5 3.1.2 Azimuth Cube ........................................................................................................... 6 3.2 4 Slope Calculation .............................................................................................................. 5 Event Tracker.................................................................................................................... 6 Tutorial..................................................................................................................................... 7 4.1 Stepwise procedure for “Dip calculator” ......................................................................... 7 4.2 Stepwise procedure for “Event tracker” ........................................................................ 12 4.3 Guidelines ........................................................................................................................ 16 5 Input Tree Structure ............................................................................................................ 17 6 References ............................................................................................................................. 18 7 Help and Support Information .............................................................................................. 19 3 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 1 Introduction In seismic exploration, horizon tracking is one of the most critical techniques in seismic data interpretation and directly affects the capacity and efficiency of the structural interpretation. Because horizon interpretation is extraordinarily time-consuming and laborious, a good horizon tracking technique can greatly improve the efficiency of the structural interpretation, heighten the interpretation accuracy, and enable geological researchers to focus on reservoir prediction rather than horizon interpretation. Because a seismic event generally corresponds to a specific formation or formation group, we can take seismic events as the guide of the horizon tracking, and use the geometric information of seismic events to identify the location and structure of strata on a seismic section. In order to solve the problems of conventional event tracking methods, a new event tracking method – event tracking based on dip calculation techniques is proposed here. Slope/dip can be calculated based on the time shift of the resemblance factor k of the amplitude magnitudes. Then based on a check of the resemblance factor the coordinate points or the location values can be stored and continuous surface points can be connected by interpolating the surface values following the slope values. The main advantage of this approach is to automate the seismic data interpretation. Since the plug-in will be tracking on each sample point which is out of scope for the manual interpretation, the interpretation can be faster, more precise and robust. 2 Overview The “Dip Calculator To Event Tracker” plug-in is developed using Ocean SDK. This plug-in facilitates to track the events in the seismic data using dip calculations. Main features of the plug-in are: Multiple surfaces can be generated and can be used during final geological modelling. Generation of a stack of horizons on a single click is possible. Flexibility to select the area of interest from the cube for horizon generation. Horizons are generated after analyzing each and every sample from the cube, which results in very high level of accuracy and a realistic picture of the strata. 4 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. All possible detail surfaces can generate a precise & accurate geological model which finally goes for the simulation model and becomes a decisive factor for the well location finalization. The surface bundles can contribute highly for the geo-body identification. The “Dip Calculator To Event Tracker” plug-in allows the user to perform the event bundling using two different modules. Dip calculator Event tracker 3 Algorithms 3.1 Slope Calculation The calculation of the dip/slope & azimuth of the seismic events or reflectors is entirely based on the multi trace geostatistical analysis of the coherence. Multi-trace relationships, including cross correlation techniques, has been implemented successfully. The multi-trace semblance estimates measured in milliseconds per meter enables the automatic picking of 3-D seismic horizons. Calculating the semblance of the analytic trace will allow us to obtain robust estimates of coherency even about the zero crossings of seismic reflection events. Our search for an estimate of the apparent dip of the seismic reflector at time ‘t’ is thus reduced to the direct calculation of discrete apparent dip at each sample point. Optimal angular discretization is important to minimize the computational cost, which increases linearly with the number of angles searched. Finally the slope/dip cube contains the maximum dip magnitudes for inline & xline directions which are considered to be the true dip components at each sample point. Following sections will give an overview on the output cubes generated from Dip calculator module. 3.1.1 Inline/Xline Slope Cube As all the calculations are based on vector object, each analysis will have vector components in two resultant directions. Inline/Xline slope direction in which the inline/xline cube will store the entire inline/xline slope component at respective sample location. It will be able to correlate the each point of coherence on a particular slope path. 5 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 3.1.2 Azimuth Cube Calculation of azimuth cube is also a multi-trace calculation at each sample point. The azimuth cube is ideally composed of tangential azimuth of each sample and stores the dominant directional parameters of the cube. The azimuth cube actually identifies the direction of true slope at each sample point. Usage The slope cube actually contains the information to steer the horizon /reflectors. The main statistical correlation is done based on the slope cube while generating the multiple horizons. All outputs are guided by the slope cubes while generating any surface. The slope cubes itself can be a useful tool to analyze the curvature and shift of events. Dip calculator is intended to use on seismic volumes where the inline range, cross-line range and the time window can be changed by the user as per the requirement. The seismic volumes must be post-stack traces in time domain for this version. However, the performance can considerably enhanced by experimenting with the parameters. 3.2 Event Tracker For tracking the event in the seismic section we utilize the slope cube generated from the Dip calculator module of the plug-in. The coordinates for the horizon created are calculated taking the inline slope cube and cross-line slope cube as reference. Since we are using both inline and cross line slope cube, the coordinates of the intended horizon can be obtained from two different directions. The horizon is created in the inline and cross-line direction. Now a set of iterative processes will undergo to obtain a set of points to create another horizon. In this way multiple horizons are created depending upon the window of analysis taken. The origin of calculation is chosen by the algorithm intelligently at the minimum time within the window specified. Then the surface gets extended to the next sample based on the time correlated vector components of the slope & azimuth. Sample rate of tracking can be predefined and can produce ultimate dense network of horizons by tracking the horizons at unit sample rate or optionally can be tracked a less dense surface network by tracking them at a multi space sample rate. The stack of horizon generation follows the geological rule of succession as the maximum encountered time within the entire stack of horizon is assumed to be deposited first in the succession of events & the minimum is deposited 6 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. last. No derived event is crossing each other in this case so typical precedence of onlap, offlap, toplap is getting followed here. Usage Seismic data interpretation can be automated. Interpretation can be faster & more precise as it will be tracking on each sample point which is out of scope for the manual interpretation. However, the performance can considerably enhanced by experimenting with the parameters. Also the plug-in has the option of providing the level of density for the horizon creation which the user can apply depending upon his choice. 4 Tutorial This section describes how to use “Dip Calculator To Event Tracker” for enhancing the capacity and efficiency of structural interpretation. Note: Users can work on their own dataset or test dataset provided along with this plug-in. 4.1 Stepwise procedure for “Dip calculator” 1. Open petrel 2. Load the petrel project 3. Select Processes pane > Plug-ins > Dip calculator 7 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 1: Petrel process pane Also, User has an option to open Dip Calculator from Petrel ribbon. Select Seismic Interpretation > Interpretation plugins > Dip Calculator Screen 2: Petrel Ribbon mode 8 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 1 2 3 4 Screen 3: Dip Calculator UI Steps to provide parameters: 1. Provide cube using button from input tree. Screen 4: Input cube 2. Select the dip cube range for creating the slope cubes. This range will then define the size of the new slopecube. User can provide range in 3 dimensions i.e. inline, xline and time window range. These ranges are to limit the processing on the specified sub volume. 9 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 3. Provide the value for instantaneous window in millisecond. The instantaneous window size is the most important factor in the tracking of the complex areal geology. The instantaneous window of analysis acts as an operator, and scan through the time length of the data i.e. it will check for the trend within this range. Higher the value of instantaneous window time consumption will be more. Smaller value will give you more precise and accurate output. Note: TNS = Total number of samples within the time range provided by the user If TNS is odd: The Instantaneous window size may vary from 0 to (TNS/2)-1. If TNS is even: The Instantaneous window size may vary from 0 to (TNS-1/2). Depending on the selected time window range, maximum default value for instantaneous window is populated in the textbox. Screen 5: Dip Calculator UI with values 4. After providing all parameters click “Apply” button to start the processing. This will generate the slope cubes in the collection called as “Dip cubes”. “Collection of ‘Dip cubes’ generated successfully” message pops up on successful completion of process. 10 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 6: Dip Calculator UI on “Apply” click Screen 7: Dip Calculator result 5. “OK” button have the same functionality as “Apply” but it closes the window after processing. 11 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 4.2 Stepwise procedure for “Event tracker” 1. Select Processes pane > Plug-ins > Event tracker Screen 8: Petrel process pane Also, User has an option to open Event Tracker from Petrel ribbon. Select Seismic Interpretations > Interpretation plugins > Event Tracker Screen 9: Petrel Ribbon mode 12 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Steps to provide parameters: 1 2 3 4 5 Screen 10: Event Tracker UI 1. Provide slope cube, inline slope cube and xline slope cube, generated as an output from Dip calculator. Note: Only slope cube, inline slope cube and xline slope cube should be allowed to provide as an input for Slopecube, inline Slopecube and xline Slopecube respectively. 13 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 11: Slope cubes for input in “Event tracker” 2. Select the horizon window range. User can provide range in three dimensions i.e. inline, xline and time window. These ranges are to limit the processing on the specified sub volume. 3. Provide the level of density for the horizon created. It defines the time difference between the horizons. Denser the option lesser will be the time difference between horizons. Denser horizon tracking can help the interpreters to see more geology through slicing the data. It also can guide well correlations and improve the chances of finding stratigraphic traps. There are 3 level of density, i. Low: If user chooses the Low density at the time of horizon creation then plug-in will create horizon at every x interval where x= (60/Sample Interval). ii. Moderate: If user chooses the Moderate density at the time of horizon creation than plug-in will create horizon at every x interval where x= (40/Sample Interval). iii. High: If user chooses the High density at the time of horizon creation than plug-in will create horizon at every x interval where x= (20/Sample Interval). 4. User has an option to provide existing interpretation folder as an input to place plug-in generated horizons in it, if not provided the horizons will be placed under plug-in generated interpretation folder named as “Event tracker”. 14 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 12: Event Tracker with values 5. After providing all parameters click “Apply” button to start the processing. This will generate the stack of horizons under the location if provided by user else under the “Event tracker” interpretation folder generated by plug-in. On successful completion of process “Horizons created successfully” message pops up. Screen 13: Event tracker on ‘Apply’ click 15 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 14: Event tracker result 6. “OK” button have the same functionality as “Apply” but it closes the window after processing. 4.3 Guidelines As mentioned before, the generation of slope cube is based on the concept of multi trace slope calculations. The tool generates the precise event tracking based on the slope and azimuth values extracted from the original seismic traces. Since the generation of slope involves complex algorithmic calculations, a fair amount of time will be consumed to generate slope cube, azimuth cube from the input seismic cube. This tool gives excellent results while implemented with broad understanding of the local geological variation and guided and segmented by the interpreter. Note: The log file for petrel needs to be flushed regularly for consistent performance. 16 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 5 Input Tree Structure Dip calculator plug-in generates slope cubes in a collection named as ‘Dip cubes’. The naming convention followed for cube names are <cube name>_SubCube, <cube name>_SlopeCube, <cube name>_AzimuthCube, <cube name> _Inline_SlopeCube and <cube name> _Xline_SlopeCube respectively. Screen 15: Dip calculator result Event tracker plug-in generates stack of horizons in a collection provided by user, if not than it will be placed in a collection “Event tracker” created by the plug-in. Naming convention followed for the horizon is <survey name>_<cube name>_Horizon_<millisecond>ms. 17 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. Screen 16: Event tracker result 6 References Meldahl, P., Heggland, R., de Groot, P., Bril, P. , 2000, Semi-automated detection of seismic objects by directive attributes and neural networks, method and applications : EAGE 62nd Conference and Technical Exhibition — Glasgow, Scotland. Finn, C. J., 1986, Estimation of three dimensional dip and curvature from reflection seismic data: M.S. thesis, University ofTexas at Austin. Dalley, R. M., E. E.A. Gevers, G. M. Stampli, D. J. Davies, C. N. Gastaldi, P. R. Ruijetnberg, and G. J. D. Vermeer, 1989, Dip and azimuth displays for 3D seismic interpretation: First Break, 7, 86–95. Bednar, J. B., 1998, Least-squares dip and coherency attributes: The Leading Edge, 17, 775–776. A dip-spreading method for horizon tracking based on plane-wave destruction technique Chen Maoshan*, Zhan Shifan, Wan Zhonghong, Xu Shaobo and Shao Yongmei, BGP, CNPC Link: http://geophysics.ut.ac.ir/DBS/up/35/conf-406.pdf http://faculty.kfupm.edu.sa/ES/ashuhail/Graduate/GEOP501/Ch4/2006/Bahorich-1995.pdf http://geology.ou.edu/aaspi/publications/2006/marfurt_GPHY2006.pdf http://www.cseg.ca/publications/recorder/2001/09sep/sep01-seismic-attributes.pdf 18 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved. 7 Help and Support Information “Dip Calculator To Event Tracker” plug-in is provided by © L&T Infotech. For support information contact Larsen and Toubro Infotech Ltd. e- mail: [email protected] 19 © 2014 Larsen & Toubro Infotech Ltd. All rights reserved.
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