Well Log Data Processing Prepared By: SHOAIB AAMIR FAHIM
Well log Processing.Integrated interpretation of any geological model requirescautious grounding and judicious use of petrophysical logs andother well-derived data.The main purpose of well log processing is to prepare the welldata for interpretation.Processing steps varies according to Company/Client andavailability/Quality of data.
Well Log Data Processing Steps Data Check. Depth Shifting. Removal of End Effects. SP baseline shift. Rescaling. Patching Block editing. Splicing /Construct composite curve. Value Edit Tabular Edit. Fill Gaps. Data Quality check. Final Report.
Data CheckReview how many Logs and its digital are provided by client.If digital is missing then these logs/curves need to be digitize.Read header information.Data Loading Load digital data in provided software for processing.Depth Shifting Depth shifting enables to shift curve data relative to a reference curve (GR or Deep Resistivity e.g. LLD, LN). The measurements from each tool are aligned to a common depth. Two ways to depth shift curve data. 1.Bulk Depth Shift. 2.Multiple tie line Depth Shift.
1. Bulk Depth Shift. Single shift to an off-depth curve and graphically tie it to your reference curve. This single shift is applied to all curve depths.2. Multiple Tie Line Depth Shifting. Multiple points on an off-depth curve and graphically tie them to points on your reference curve. Stretch or compress a portion of an off-depth curve using this method.
Removal of End Effect.The curve response other then the response of lithology.Such as response of curve in casing or tool response at the startand at the end of logging.End effect Curve before end Curve After end effect removal effect removal
Baseline Shifting.Baseline shift is primarily designed for correcting SP curve drift.Removal of SP baseline drift aids the automatic computation ofwater resistivity and shale volume over long depth interval.-ve SP.When ions of NaCl moves from formation water to mud filtratesthen generated SP called –ve SP.+ve SP.When ions of NaCl moves from mud filtrates to formation waterthen generated SP called +ve SP.
RescalingRescale allows for correction of improper calibration and missedscale changes of digitized logs.It also allows for convertion of linear scale to logarithmic scale (andvise versa). SP curve before SP curve After Rescaling Rescaling
Patching curves.Patching curves allows you to interactively digitize points on thescreen using Mouse Button 1.Patch curves use to remove unwanted data points, such asnoise spikes, and to reshape curves.Editing of sonic for cycle skipping and density for any boreholewashout.
Block EditingBlock editing enables to “square” or visually average curve intervals.It is typically used to block sonic and density logs for generatingsynthetic seismograms and determining acoustic impedence.
Splicing or Construct compositeSplicing curves merges segments together at one time.This is useful for merging curves from different logging runs into asingle composite curve.
Value EditingValue editing enables you to change the value at a data point on theselected curves by typing a new value.
Tabular EditingTabular editing provides a graphical interface for digitally changingindividual curve value at selected depth.This is useful when only a limited number of values need adjusting.
Fill Gaps.Fill Gap is used to replace nulls with values interpolatedbetween valid data points.
Data Quality Check.QC job perform To ensure the quality of processing.QC person check the processed data thoroughly beforedelivering to client.If there is any flaw in processed data then need to bereprocessed.Final ReportAfter the data quality assurance, write the final report.Final report express or define all processing steps, curvedetails & comments regarding data.