Core-to-Log Depth Matching: Porosity & Permeability QC with Statistical Validation

Find the bulk core-to-log depth shift by cross-correlation, check porosity before and after the shift with bias, RMSE, max error and R², and QC power-law and Winland permeability transforms against core.

Petrophysicists and core analysts integrating core measurements with wireline log data for accurate reservoir characterisation and permeability prediction.

Finds the bulk depth shift by cross-correlating core porosity against the log porosity curve (correlation scanned from −10 to +10 ft in 0.5 ft steps, peak refined with a parabolic fit), applies it, and compares the core-log porosity match before and after the shift (bias, RMSE, max error, R²). Per-sample tie-point shifts are shown alongside, with a constant vs variable shift classification. A separate core plug set QC's power-law and Winland R35 permeability transforms against core k and picks the better model by log10 RMSE.

• Instructions & Legend • Core Depth Data — core and log depths, core phi and log phi for up to 10 depth-matching samples, plus the log porosity curve • Depth Shift Analysis — tie-point shift statistics, cross-correlation scan with r-vs-shift chart, recommended bulk shift • Porosity QC — core phi vs log phi at the corrected depth and before the shift, match quality, 1:1 crossplot and delta phi bar chart • Summary — shift statistics, cross-correlation shift, match count, generated narrative • Bias & RMSE Analysis — bias, RMSE, max error and R² for porosity before and after the shift, and for log10 k • Permeability QC — core k vs power-law and Winland R35 k, percent error per sample, RMSE, bias, R², best model • Phi-k Core Crossplot — core phi and core k for the 15-sample permeability set, RQI quality, power-law trend overlay

• Cross-correlation: CORREL scan ±10 ft at 0.5 ft, parabolic peak refinement; type over the shift to impose your own • Tie-point shifts: constant shift indicated when std dev < 0.5 ft • Porosity QC: ΔPhi = core phi − log phi per sample; match quality from |ΔPhi| • Permeability QC: k = a × phi^b (a, b inputs) and Winland R35 solved for k; quality flag (Excellent/Good/Fair/Poor); best model by lowest log10 RMSE • Phi-k crossplot: RQI = 0.0314·√(k/φ) quality class per sample

• Excel 2016+ compatible • 1,100+ formulas across 8 tabs • Sample data: 10 depth-matching slots (9 filled) and a 15-sample permeability set (8010–8150 ft) • MDT professional color scheme

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