Presentation

1. Presentation • PfEFFER Basis • Review and Demonstration of PfEFFER v. 2.0/Pro • Examples

2. PfEFFER Version 2/Pro Developers: Geoff Bohling, John Doveton, Willard Guy, W. Lynn Watney, and Saibal Bhattacharya in collaboration with 14 companies, U.S. Department of Energy, BDM-Oklahoma, Inc., and Kansas Technology Enterprise Corporation Release date of Version 2.0/Pro: February, 1998 Runs under Excel 97, Excel 2000, PfEFFER 2.0 add-ins and examples require 2 MB of disk space.

3. Programming platform • Add-ins for Excel 97 and Excel 2000 • PfEFFER.xla for PfEFFER 2.0 • Gridsim.xla, utmexl97.xla, and XsecExc97.xla for PfEFFER Pro • Developed in Visual Basic for Excel • Runs under Windows 95, 98, NT, & 2000 • Utilities are included to convert PfEFFER 1.1 (Excel 5.0) files to 2.0/Pro (Excel 97)

4. Goals of PfEFFER • Characterize subtle reservoir properties important to hydrocarbon pore volume and fluid flow; • Differentiate bypassed, commingled oil and gas reservoirs; • Integrate geological and engineering information; • Provide practical, accessible tools for log analysis.

5. Applications • Gauge reservoir productivity; • Discern communicating volumes of the reservoir; • Integrate with geologic models including deposition, diagenesis, and structure.

6. Practical, user-friendly log analysis using PfEFFER • Cost-effective, accessible well log analysis • spreadsheet based • graphically oriented • interactive, linked: easy “what-if” analysis • open ended with other Windows applications • Meeting ground for geologists & engineers

7. Old logs can be analyzed with PfEFFER * Minimum log data required by the spreadsheet-based software is aporosity and resistivity log. * Old logs are well suited to this analysis once they are digitized or simply typed into the spreadsheet.

8. Modules in PfEFFER 2.0 • Reading and organizing information from LAS digital files • Hough transform for simultaneous solution of Archie equation constants and formation water resistivity • Log (depth) display • Calculation of porosity with option for shale correction and secondary porosity • "Super Pickett" crossplot annotated with lines of water saturation, bulk volume water, and permeability

9. Modules in PfEFFER 2.0 (Continued) • Shaly sand models for Sw calculation (alternatives to Archie equation) • Moveable oil plots and calculations • Pay-flag cutoffs (and pay column with incremental hydrocarbon feet) • Lithology solution • Capillary-pressure analysis (mapping on Pickett crossplot) • Zonation by depth • Mapping

10. Modules in PfEFFER Pro • Color-image cross section generation • Latitude-longitude to UTM conversion • Bridging software to build input file for a reservoir simulator • tracking grid cells and well locations • gridding of reservoir parameters • preparing reservoir data to export to simulator

11. The Archie Equation • Sw = [ (a / Fm)*(Rw / Rt) ](1/n) • Sw: water saturation • F: porosity • Rw: formation water resistivity • Rt: observed bulk resistivity • a: a constant (often taken to be 1) • m: cementation factor (varies around 2) • n: saturation exponent (generally 2)

12. Importing LAS files • Log ASCII Standard • Canadian Well Logging Society • Easy exchange (floppy disk) • Read/modify with standard word processor • OpenLAS Add-In • Displays available logs, depth range • Reads selected information into Excel • Creates a well workbook with unit worksheets • Units are named depth intervals (user-specified)

14. PfEFFER Worksheet Layout • Home area with computed parameters • Computations (links) keyed on RT, PHI (resistivity, porosity) via Archie equation • “whole-unit” parameters in column B • Attribute columns for auxiliary information • used for color-coding points on Pickett Plot • available for log vs. depth plots • Input logs, additional computations to right

15. PfEFFER Spreadsheet

16. Columns in the home area • PARAMETERS (column B) • well info, model parameters, summary values • ZN, DEPTH, THK: • zone label, depth, thickness • RT, PHI: • Bulk resistivity, porosity (fractional!) • Derived from input logs on right

17. Columns in the home area • RWA, RO, MA: • Apparent formation water resistivity, water-saturated resistivity, and cementation exponent • SW: Water saturation • BVW: Bulk volume water (SW*PHI) • VSH: Shale proportion • computed from input logs using Vsh button

18. Columns in the home area • Pay: Incremental thickness of oil • set to zero if PHI, SW, BVW, or VSH outside user-specified cut-offs • THK*PHI*(1-SW) otherwise • Flow: Zonation

19. The PfEFFER Toolbar

20. The PfEFFER Toolbar -Shale Fraction and Porosity • Home area calculations • Vsh: Computes values in VSH column • Phi: Computes values in PHI column • based on neutron, density, sonic porosity or combination • option to correct phi for Vsh

21. The PfEFFER Toolbar - Calculation of Porosity

22. The PfEFFER Toolbar -Depth Plots of Logs

23. The PfEFFER Toolbar- Pickett Plot • Pickett Plot generation and annotation • Generates Pickett Plot • Adds water saturation contours • Adds BVW contours • Adds permeability contours • Colors points according to attribute • Adds capillary pressure contours

24. The Annotated Pickett Plot • Log-log resistivity-porosity crossplot • based on transformed Archie equation • log Rt = log(a Rw) - n log Sw- m log F • reveals porosity-water saturation patterns • Color-coding of third attribute • depth, gamma ray, photoelectric factor, . . . • Contours of reservoir parameters • water saturation, bulk volume water, permeability, capillary pressure

25. Contours on the Pickett Plot • SW, BVW: from Archie equation • Permeability (Wylie and Rose, 1950) • log k = log P + Q log F - R log Sw i • P, Q, R: Set in Parameters column • Timur (1968) constants (sandstone) default • Assumes irreducible saturation (Sw i) • Capillary pressure • from user-specified pressure-saturation curves

26. “Super Pickett” Plot

27. The PfEFFER Toolbar • Other plots and analyses • Plots of logs vs. depth • Rhomaa-Umma computations, plot • Composition plot (based on RU results) • Moveable oil computations, plot • Pay-flag cutoffs • Capillary-pressure analysis • Zonation by depth

28. The Moveable Oil Plot • Sxo = [ (a / Fm)*(Rmf / Rxo) ](1/n) • Rmf: Resistivity of mud filtrate • Rxo: Microresistivity • presumably bulk resistivity of flushed zone • Sxo: Saturation of total moveable fluid • assumes filtrate has displaced everything moveable • BVF = Sxo*F • Bulk volume (moveable) fluid • Volume moveable oil = BVF - BVW

30. An Example Moveable Oil Plot

31. Capillary Pressure

32. Capillary Pressure Contours • BVW: empirical expression of • pore throat distribution • capillary pressure • hydrocarbon column • Plot Sw vs. phi on Pickett crossplot at constant Cp (height above FWL) • Convergence of Cp contours at higher pressures where BVW changes only gradually • Assume similar pore type for connected points

33. Color Coding of Pay Cut-offs • Zone considered pay if • PHI > PHICUT • SW < SWCUT • VSH < VSHCUT • BVW < BVWCUT • Dynamic coloring of pay zones • PHI, SW, VSH, BVW values outside cut-offs also flagged • Toggle with “Colors” button

34. Color Coding of Pay Cut-offs Color Button

35. Compositional Analysis -The Rhomaa-Umaa Plot • Rhomaa: Apparent matrix density • from bulk density and porosity • Umaa: Apparent matrix photoelectric absorption coefficient • from bulk photoelectric factor (PEF), density, and porosity • Crossplot is good indicator of mineralogy • can be annotated with key minerals

36. An Example Rhomaa-Umaa Plot

37. The Composition Plot • Derived from Rhomaa-Umaa results • Keyed to three end-member minerals on Rhomaa-Umaa plot • Alternative composition systems possible • Plot linked to worksheet data • updates automatically if end-member definitions changed

39. An Example Composition Plot

40. The PfEFFER Mapping Module • Compiles PARAMETER information from a number of wells into a mapping workbook • linked to underlying well workbooks • Unit worksheets from different well workbooks matched by name • Posts well locations with labels • Interpolates parameter values to regular grid • Creates shaded contour or 3D surface representations of grids

41. Posting of Well Locations

42. A Contour Map - an Excel Chart

43. 3-D Maps - an Excel Chart

44. Expanded log analysis in PfEFFER 2.0 Shaly Sand Models for Sw Calculation -- Sw model menu permit selection of Archie water saturation model (the default) and two shaly sand models, the Simandoux model and the dual-water model. Hough Transform -- The Hough transform is used for simultaneous solution of Archie equation constants and formation water resistivity. Secondary Porosity -- Secondary porosity is calculated as the difference between the total porosity (from density or neutron porosity) minus sonic porosity.

45. Shaly Sandstone Model Sw Model = Archie Sw Model = Simandoux

46. Correcting Rt and Phi for Shale Effects • Corrected values provide improved correspondence to pore size, geometries, fluid saturations, capillary pressures, and hydrocarbon column • Evaluate models in combination, and determine which is best

47. Hough Transform --for solution of Archie equation constants and formation water resistivity

48. Secondary Porosity

49. Other New features in PfEFFER 2.0 Zonation by Depth-constrained Cluster Analysis - Depth-constrained multivariate cluster analysis can be employed to segment the entire spreadsheet into subintervals based on user-specified set of logs. A hierarchical cluster (Ward's method) is used to produce subintervals that are as homogeneous as possible and distinct as possible from each other, in terms of their log characteristics. Option is useful in evaluating flow units and can be used as a blocking function. Forward Modeling -- Module implements equations developed by Pittman to predict values of rx, capillary pressure, and hydrocarbon column height for a range of water saturation values based on specific values of permeability and porosity.