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Richard Odom O- GeoSolutions CAARI 2010

Richard Odom O- GeoSolutions CAARI 2010. Can accelerator-based radiation sources replace the chemical-based sources commonly used in geophysical exploration?. Theme:.

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Richard Odom O- GeoSolutions CAARI 2010

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  1. Richard Odom O-GeoSolutions CAARI 2010 Can accelerator-based radiation sources replace the chemical-based sources commonly used in geophysical exploration?

  2. Theme: Radiation-based measurements are an important tool in oilfield development, but it would be desirable to use accelerators rather than Radio-isotope sources. • Security, terrorism and RDD’s • Stewardship and liability • Personnel Safety and Exposure

  3. Predominate Applications: Formation Density Neutron porosity Well Logging with Radio-isotopes Source: 2Ci Cesium Source: 20Ci AmBe From Ellis

  4. Logging background: N-D synergy Water-filled limestone Water-filled sandstone Water-filled Shale Gas-filled sandstone

  5. Logging background: Neutron-Density plus resistivity Log Analyst’s Triple-Combo

  6. Neutron Generator (enabled) Measurements • Thermal Neutron Lifetime (Sigma) • Inelastic gamma spectroscopy for Carbon and Oxygen • Prompt-neutron logging for U235 • Cased-hole pulsed-neutron density

  7. Accelerator Time line • 1960’s Lab development of neutron generators • 1970’s commercialization Pulsed-neutron • 1980’s commercialization of neutron-induced spectroscopy systems (Carbon/Oxygen) • 1980’s development and field trials of LINAC density tool by Schlumberger • 1990’s accelerator-based Neutron Porosity • 1990’s Cased-hole pulsed-neutron density • 1990’s development of LWD pulsed-neutron density

  8. So what will it take to replace the radio-isotope sources? • Equivalent measurements within environment and economic constraints • Existing Neutron-Density are simple systems! • Existing analysis paradigms have deep roots • Neutron porosity is easier than density • Impetus • Value added • Regulatory

  9. Marketing Study of LWD features #4 Desirable Feature A New Integrated LWD Platform Brings Next-Generation Formation Evaluation Services, Weller et al. SPWLA 2005

  10. Value added • Neutron generator replaces AmBe source for neutron porosity. • Neutron generator and gamma detectors for pulsed-neutron density • But, in the end, focused density image was needed. The Cesium source is still used for imaging and density.

  11. Example: Cased-hole PN density Gamma Rays are Compton scattered in transit to a long-spaced detector Gamma Rays are created from inelastic scattering proximal to the neutron generator

  12. Two formations with same density, but different Hydrogen content Detector Target Improvements in a through-casing pulsed-neutron density log, Odom et al. 2001, SPE 71742

  13. Inverse methods Deterministic model for two gamma detectors and a fast-neutron detector 2-Group diffusion theory model

  14. Inverse methods Empirical Methods Outputs: Density Porosity Neutron Porosity Inputs: Pulsed-neutron measurements

  15. Value-added: Deeper penetration allows density measurement in cased-wellbores • Typical correlation: ~3 p.u. • Cased-hole Uncertainty • Hole-size • Cement quality • eccentricity • Where’s the value? • Moving the rig • Lowered liability • Open-hole accuracy

  16. So what will it take to replace the radio-isotope sources? • Equivalent measurements within environment and economic constraints • Existing Neutron-Density are simple systems! • Existing analysis paradigms have deep roots • Neutron porosity is easier than density • Impetus • Value added • Regulatory

  17. Constraints: Power Consumption • Optimal: 15 watts • Useable: 30 watts • Borderline: 100 watts • No Bueno: >200 watts These systems operate on very long extension cords or batteries

  18. Constraints: Size • Optimal: 1.75-inch O.D., 15-foot length • Useable: 2.75-inch O.D., 20-foot length • Borderline: 4-inch O.D., 25-foot length • No Bueno: >5-inch O.D., >30-foot length Constrained by wellbore size and use in logging stack

  19. Constraints: Operating Temperature • Optimal: 175 C • Useable: 150 C • Borderline: 125 C • No Bueno: < 100 C Wells are Hot!

  20. Constraints: MTBF or servicing • Optimal: 2000 operating hours • Useable: 500 operating hours • Borderline: 200 operating hours • No Bueno: <100 operating hours Ask BP, Failure is not an option

  21. Constraints: Sample Time • Optimal: 4 seconds • Useable: 8 seconds • Borderline: 16 seconds • No Bueno: < 20 seconds Time is Money!

  22. Constraints: System Cost • Optimal: $150K • Useable: $200K • Borderline: $250K • No Bueno: >$300K Typical cost Neutron-Density with sources: $150K

  23. Conclusions: Can it be done? • Technical • There are systems and techniques that could supplant need for radio-isotope logging • Regulatory: it’s a Wild-Card • Finding Added Value? Research!! • More radiation per watt • Improved ion sources • Improved targets • High voltage efficiency • Rugged and Tough solutions • Next generation Algorithms and Models

  24. Thank You!

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