INTERPOLATION. Stitch_Prep and Stitch modules

Transcription

1 Interpolation

2 INTERPOLATION Stitch_Prep and Stitch modules

3 Claritas pre-stack N Dimensional Interpolation The Claritas N Dimensional interpolation algorithm is controlled by two seperate modules. Module 1 : STITCH_PREP : Reads the Seismic data as a single or multiple datasets and creates a map file defining which trace from a dataset will be used to populate any given offset bin within a CDP. The module provides users with multi-tier preferential binning options to optimally select traces based on users requirements. Module 2 : STITCH : Performs the actual INTERPOLATION, using the map file created by the STITCH_PREP module the required traces are read in and for CDP Bins within offset plane where no trace is available a new trace is interpolated from surrounding traces. The module also has the capability to bin centre all input traces if the user requires. Bin centring is performed by means of an partial NMO correction and update of the OFFSET/SOURCE_X/SOURCE_Y/REC_X/REC_Y headers and removal of partial NMO. Bin centering of the data will often provide for improved migration results due to better cancellation of migration smiles and therefore less noise.

4 Module 1 : STITCH_PREP. PARAMETERS DESCRIPTION OUTPUT Name of the map file created by STITCH_PREP module. Defines the traces to be used in the interpolation process. AREALNAME Optional AREAL output QC file (This option not fully implimented as yet) LISTFILE Optional file containing list of input datasets. INPUTFILE Input dataset. GEOMFILE Geometry database or 3DGRID file. NMOFILE NMO velocity file. STARTOFFSET Minimum offset value for offset Bin ENDOFFSET Maximum offset value for offset Bin (Startoffset/Endoffset parameters should be used when processing data one offset plane at a time) OFFSETS Defines FIRST/LAST and Offset increment when processing all offsets in a single flow. USE_ABSOFF Instructs dataflow to ignore the sign of the offset when set to YES. RANGE Distance from Bin Centre within which t traces will be selected for binning. STARTINL/ Defines First/Last Inline and STEPINL/ENDINL the increment between inlines. STARTX/STEPX Defines First/Last Crossline and the /ENDX increment between crosslines.

5 Module 1 : STITCH_PREP- Part 2. PARAMETERS DESCRIPTION ORDER_NUM User defined hierarchy for trace selection (1,2,3,4,5) based on trace headers, two are pre-defined Distance Distance to bin centre Azimuth Trace azimuth 0=Ignored 1=Traces selected first based on the results of Distance/Azimuth/header that is defined as prioriity 1. 2=Second priority, is used if more than one trace can be selected based on the Priority 1 selection method 3= Third priority etc etc. DIST_RES Defines the precision used to select traces. 0=Full precision 1=Centimetre 10=Decimetre 100=Metre etc. AZIMUTH Angle in degrees used as basis for comparison. AZIM_RES Level of precision used for Azimuth selection USE_ABSAZI Yes uses absolute azimuth.. KEYNAME* Trace header name. Allows user selection of traces i.e. based on sailline type (Prime/Infill/Reshoot) for instance. ORDER_UP* Defines if high or low value in trace header should take preference for trace selection..

6 PARAMETERS DESCRIPTION INPUT Name of the map file created by STITCH_PREP module. OUTPUTFILE Name of the Output dataset. V5_OUTPUT No=HDF5 output Yes= CSEGY. DIRECTION Direction of interpolation (Inline/Crossline). BIN_CENTRE Yes=all traces are Bin centred. No=Only interpolated traces are bin centred MPI_COMMAND Defines the MPI command to run the process. TOTAL_PROCS No of CPU s to utilise. INTERPWIDTH Defines the width of the correlation envelope in metres. Should be large enough to calculate the correlation, but small enough that curvature can be resolved. INTERPLEN Length of the correlation envelope in ms, should be equal to the approx length of the wavelet.. ITERMAXOUT Maximum no of feature extraction iterations. OUT_THRESH Threshold for terminating interpolation. ITERMAXIN Max number of iterations inner feature extractions. IN_THRESH Threshold for treminating the inner feature extraction loop.. STITCH Module

7 STITCH and STITCH_PREP Modules STITCH_PREP and STITCH form part of the IMAGE suite of standalone cluster enabled modules. STITCH_PREP is run in single cpu mode and can read either CSEGY or HDF5 input datasets. The STITCH module may only be run on a system on which MPICH2 is installed and a suitable cluster environment is configured. STITCH deplots an N Dimensional interpolation algorithm capable of interpolating five dimensional data, but is run along 2 Dimensional slices through the data volume. STITCH uses two interpolation schemes. For small gaps in an otherwise complete data area we utilise a method based on the greedy Radon transform, for areas where larger gaps or where the data has many gaps STITCH uses a method in which an estimation process is embedded within an iterative greedy Radon process to provide an optimal interpolation solution. STITCH switches between the two methods internally and is designed to optimise the quality of the interpolation and computation time.

8 Hawke Bay 3D XL pre Interpolation

9 Hawke Bay 3D XL post Interpolation

10 480m offset plane, 900ms timeslice