Well Log Data Well Log Data ProcessingProcessing

Prepared By:

SHOAIB AAMIR FAHIM

Well log Processing.

Integrated interpretation of any geological model requires cautious grounding and judicious use of petrophysical logs and other well-derived data.

The main purpose of well log processing is to prepare the well data for interpretation.

Processing steps varies according to Company/Client and availability/Quality of data.

Well Log Data Processing StepsWell Log Data Processing Steps Data Check.Data Check. Depth Shifting.Depth Shifting. Removal of End Effects.Removal of End Effects. SP baseline shift.SP baseline shift. Rescaling.Rescaling. PatchingPatching Block editing.Block editing. Splicing /Construct composite curve.Splicing /Construct composite curve. Value EditValue Edit Tabular Edit.Tabular Edit. Fill Gaps.Fill Gaps. Data Quality check.Data Quality check. Final ReportFinal Report..

Data Check

Review 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.

Bulk depth shifting procedure.

Multiple Tie Line Depth Shifting Procedure.

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 start and at the end of logging.

End effect

Curve before end effect removal

Curve After end effect removal

Baseline Shifting.Baseline shift is primarily designed for correcting SP curve drift.

Removal of SP baseline drift aids the automatic computation of water resistivity and shale volume over long depth interval.

-ve SP.

When ions of NaCl moves from formation water to mud filtrates then generated SP called –ve SP.

+ve SP.

When ions of NaCl moves from mud filtrates to formation water then generated SP called +ve SP.

GR

SP

SN

LN

-ve SP Deflection

+ve SP Deflection

Baseline shift Procedure(-ve & +ve SP)

SP baseline Shift for –ve SP

SP baseline Shift for +ve SP

SP curve before baseline shift

SP curve After baseline shift

Baseline

+ve SP

-ve SP

RescalingRescale allows for correction of improper calibration and missed scale changes of digitized logs.

It also allows for convertion of linear scale to logarithmic scale (and vise versa).

SP curve before Rescaling

SP curve After Rescaling

Patching curves.Patching curves.

Patching curves allows you to interactively digitize points on the Patching curves allows you to interactively digitize points on the screen using Mouse Button 1.screen using Mouse Button 1.

Patch curves use to remove unwanted data points, such as Patch curves use to remove unwanted data points, such as noise spikes, and to reshape curves.noise spikes, and to reshape curves.

Editing of sonic for cycle skipping and density for any borehole Editing of sonic for cycle skipping and density for any borehole washout.washout.

Patching Curve Procedure.

Block EditingBlock EditingBlock editing enables to “square” or visually average curve intervals.Block editing enables to “square” or visually average curve intervals.

It is typically used to block sonic and density logs for generating It is typically used to block sonic and density logs for generating synthetic seismograms and determining acoustic impedence.synthetic seismograms and determining acoustic impedence.

Splicing or Construct compositeSplicing or Construct compositeSplicing curves merges segments together at one time.

This is useful for merging curves from different logging runs into a single composite curve.

Value Editing

Value editing enables you to change the value at a data point on the selected curves by typing a new value.

Tabular Editing

Tabular editing provides a graphical interface for digitally changing individual curve value at selected depth.

This is useful when only a limited number of values need adjusting.

Tabular editing procedure.

Fill Gaps.Fill Gap is used to replace nulls with values interpolated between valid data points.

Data Quality Check.Data Quality Check.

QC job performQC job perform To ensure the quality of processing.To ensure the quality of processing.

QC person check the processed data thoroughly before QC person check the processed data thoroughly before delivering to client.delivering to client.

If there is any flaw in processed data then need to be If there is any flaw in processed data then need to be reprocessed.reprocessed.

Final ReportFinal Report

After the data quality assurance, write the final report.After the data quality assurance, write the final report.

Final report express or define all processing steps, curve Final report express or define all processing steps, curve details & comments regarding data.details & comments regarding data.

Thank YouThank You