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mesaTrainingManual-new

By Monica Lopez,2014-08-03 16:44
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mesaTrainingManual-new

    MESA Training

This series of exercises will introduce you to many of the

    options that are available in MESA for the design and QC

    of 3D surveys. It is a good idea to refer to the MESA

    user‘s manual for more details about the features

    described in these exercises.

     Program Purpose ................................................... 2 GMG Database Files .............................................. 2 Steps in Survey Design .......................................... 4 Land 3D Seismic Survey Classifications ................. 6 Geometry Examples ............................................... 7 Seismic Data Processing Issues ........................... 13 Information Gathering ........................................... 16 Equations Used in Survey Design ......................... 17 Survey Analysis and QC ....................................... 20 Shooting Techniques Compared ........................... 25 Ex #1: Basic MESA Usage .................................. 29 Ex #2: Line/Brick Layout Options ........................ 42 Ex #3: Unit Template Layout ................................ 51 Ex #4: The Design Guide ..................................... 56 Ex #5: Importing Survey Files .............................. 63 Ex #6: Marine Design .......................................... 68 Ex #7: Using GMG Image .................................... 74 Ex #8: Source and Receiver Editing ..................... 77 Ex #9: Offset and Rectangular Shooting .............. 82 Ex #10: Automatic Template Centering ................ 86 Ex #11: Salvo Shooting ....................................... 91 Ex #12: Label Shooting ........................................ 93 Ex #13: Multi-Survey Capability ........................... 97 Ex #14: Using Advisor ....................................... 103 Ex #15: Attributes and Filtering .......................... 106 Ex #16: Displaying Data..................................... 116 Ex #17 Review of Recent Features ................... 123

Program Purpose

    MESA provides a great deal of flexibility in 3D survey design and analysis, whether the survey is a land, transitional area, ocean bottom cable, or marine design. Imagery, contour information, and cultural features (provided from .dxf files, for example) can be used as backgrounds to aid in the design of the survey. In this way, permit and logistical problems can be anticipated at the planning stage, reducing the time and cost of field acquisition.

    Besides flexibility in design methods, MESA provides flexibility in shooting methods and bin attribute analysis. Additionally, a number of output file formats are supported, including SEGP-1, UKOOA, and SPS, in addition to shooting scripts for Input/Output and ARAM acquisition systems. The completion of a survey design in MESA generates a Green Mountain Geophysics GeoScribe geometry database, thereby completing a major portion of the initial pre-stack processing work while still in the field. These database files are transportable across various hardware platforms, making MESA a practical tool for field and office environments.

GMG Files and the Database

    The following set of files represents what Green Mountain Geophysics refers to as the MESA or GeoScribe database. These files are a combination of ASCII and binary files and combine to hold all of the information needed to define the geometry (and refraction statics) for any 2D or 3D survey. Not all of these files will be found with every database. The *.bin and *.mid files are required only for bin attribute displays and can be deleted before archiving the database, if necessary.

    File Extension Format Description

     *.atr Binary Attribute information for receivers

     *.ats Binary Attribute information for sources

     *.bin Binary Bin information, sizes

     *.bmp Binary Picture for open database preview display

     *.cf1 ASCII Configuration file for the receiver spreadsheet

     *.cf2 ASCII Configuration file for the source spreadsheet

     *.def ASCII Default values for MESA to use with this survey

     *.fbt Binary FFID info and first break picks

     *.hdr ASCII Header information for SPS outputs

    *.idd Binary Image ray attribute information

    *.inr ASCII Instrument information for receivers

     *.ins ASCII Instrument information for sources

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     *.lbs ASCII Label shooting information

    *.mar Binary Marine survey information

    *.mas ASCII Database parameters and status flags

    *.mdd Binary Model attribute information

    *.mdl ASCII Aperture model information

    *.mid Binary Midpoint information, offsets, azimuths

    *.mrl Binary Streamer marine receiver locations

    *.mut ASCII Mute function information

    *.ndd Binary Normal ray attribute information

    *.pat Binary Source/receiver template relationships

    *.rdd Binary Offset ray attribute information

    *.rfi ASCII Filter settings for receivers

    *.rln ASCII Line names for receivers

    *.seq ASCII General shooting sequence description

    *.sfi ASCII Filter settings for sources

    *.sln ASCII Line names for sources

     *.sor Binary Source numbers and coordinates

     *.sta Binary Receiver numbers and coordinates

     *.tpl Binary Source to receiver patch relationship

     *.unt ASCII Configuration of the unit template

     *.xcl ASCII Exclusion zone type, size, and all coordinates

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    Other GMG Files used or created in MESA File Extension Format Description

     *.cfg ASCII Configuration file used to import survey files

     *.csi ASCII Color scale settings

     *.cyr Binary GMG contour file

     *.lyr Binary GMG image file

     *.nop ASCII MESA midpoint exclusion output file

     *.ptn ASCII MESA pattern output file

     *.scr either Input/Output script file

     *.sts ASCII MESA land statistics/cost output file

     *.tdf ASCII Trace data format file used to import SEGY files

     *.vyr Binary GMG vector file

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Steps in Survey Design

Step 1: Building an “idealized” survey

    MESA provides several methods for defining a survey.

    1. Direct layout and shooting Using the source and receiver layout dialogs, you can create

    orthogonal (brick or straight line), zig-zag, slash, button patch, and radial surveys. The

    surveys are created by specifying information such as inline and crossline spacings, bearings,

    and survey size. Several shooting options are then available to define the source-receiver

    template relationship.

    2. Unit Template You can create a unit template, a group of sources which are fired into a

    common receiver template, in the Unit Template window in MESA. This unit template is then

    repeated throughout the design area to simultaneously define and shoot the survey. The unit

    template is good for creating brick, orthogonal, button or swath surveys.

    3. Importing ASCII files ASCII files containing coordinates and source or receiver numbers

    can be imported directly into MESA. Examples of these files are UKOOA, SEG-P1, and SPS.

    If ASCII relational files or ASCII or binary shooting scripts are also available, they can be

    imported, as well.

Step 2: Creating a “real world” survey

    Once the initial design parameters have been set for the survey, aerial and satellite imagery, scanned topographic maps, contour displays, and/or files containing cultural information (.dxf files, for example) can be used to modify the design to take into account physical and cultural obstacles.

    Exclusion zones which exclude sources, receivers, and/or midpoint information can be defined as circular, linear, or polygonal zones. These zones can be defined graphically, by manually entering coordinates, or by importing coordinates from an ASCII file. Once the exclusion zones

    have been defined, the survey can be designed around them.

    Editing functions allow the user to selectively deactivate sources and receivers as well as relocate them in groups or individually using the mouse or keyboard. The 'redesign a line' function allows the source or receiver lines to be re-drawn maintaining the inline group interval and thus preserving the stack response - extra receivers may then be required to fill the gap. A snap to grid function may also be used to ensure that source and receiver moves maintain the group interval. Thus, the survey is as close as possible to the real world conditions before any equipment is deployed, minimizing the time in the field for equipment and crew.

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Step 3: Updating with surveyed coordinates

    The theoretical survey design can easily be updated with actual coordinates from the survey crew on a shot by shot, swath by swath, or daily basis through the ASCII file import option. The new coordinate information may be provided as absolute values or shifts from the original position. Analysis of the ongoing acquisition, via the bin attribute displays, allows for the repositioning and/or addition of sources and receivers in order to compensate for any deficiencies which may have appeared in the desired fold, offset, or azimuth distributions because of conditions in the field.

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    Land 3-D Seismic Survey Classifications

    Jim Musser, Director GMG Energy Services

    Type Applicable Areas Advantages Disadvantages In-Line Swath Open Terrain Narrow azimuth data can be Poor cross line statics, high

    processed and analyzed like 2-D SRC and RCV line density,

    seismic very sensitive to obstructions Orthogonal All Terrains Wide azimuth, good for 3-D DMO, Must use 3-D algorithms,

    can solve cross line statics, cannot use simple 2D F-K

    industry standard, economic algorithms

    operations

    Brick Open Terrain Like orthogonal, plus improves Discontinuous source lines

    near offset and overall offset are difficult in jungle and in

    distributions some other terrains Slant All Terrains Improves overall offset coverage, Surveying and line clearing

    better offsets for AVO on source lines are longer

    due to diagonal line

    orientation

    Button Patch Open Terrains, Allows sparser source points, Complex to plan

    Farm Land, Arctic, efficient use of large channel

    Desert systems

    Variable Line All Terrains Modification of orthogonal, brick, or Complex to plan Spacing slant design with similar

    advantages to each, plus

    guarantees surface consistency

    Asymmetric Spread All Terrains Modification to orthogonal, brick, or Same as for orthogonal,

    slant design with similar brick, and slant designs

    advantages to each, plus longer

    offset with less recording

    equipment

    Random All Terrains Surface consistent, minimizes Complex to plan and operate

    acquisition footprint

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Geometry Examples

    Any of the following geometries can be built in MESA by using the unit template option or by directly placing the sources and receivers before shooting. For each geometry, there is a view of the Unit Template window followed by a view of the Design window, as well as the main points for and against each survey type.

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Inline Swath shooting - Marine like

Pros: Simplest geometry for DFSV type recording systems.

    Cons: Poor azimuth distribution, poor coupling, high fold.

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Orthogonal or straight line shooting

Pros: Very simple geometry to lay out in the field.

    Cons: Comparatively expensive and yields largest Xmin. Requires good access for

     sources and receivers.

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