Richard Odom O-GeoSolutions CAARI 2010

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

Predominate Applications: Formation Density Neutron porosity Source: 2Ci CesiumSource: 20Ci AmBe From Ellis

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

Logging background: Neutron- Density plus resistivity

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

Conclusions: Can it be done? Technical There are systems and techniques that could supplant need for radio-isotope logging Regulatory: its 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

Thank You!