Richard Odom O-GeoSolutions CAARI 2010. Theme: Security, terrorism and RDDs Stewardship and...
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Transcript of Richard Odom O-GeoSolutions CAARI 2010. Theme: Security, terrorism and RDDs Stewardship and...
CAN ACCELERATOR-BASED RADIATION SOURCES
REPLACE THE CHEMICAL-BASED SOURCES COMMONLY
USED IN GEOPHYSICAL EXPLORATION?
Richard Odom
O-GeoSolutions
CAARI 2010
Theme:
Security, terrorism and RDD’s
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.
WELL LOGGING WITH RADIO-ISOTOPES
Predominate Applications:
Formation Density Neutron porosity
Source: 2Ci Cesium Source: 20Ci AmBeFrom 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 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
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
#4DesirableFeature
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 UncertaintyHole-sizeCement qualityeccentricity
Where’s the value?Moving the rigLowered liabilityOpen-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: it’s a Wild-Card Finding Added Value? Research!!
More radiation per wattImproved ion sourcesImproved targetsHigh voltage efficiencyRugged and Tough solutionsNext generation Algorithms and Models
Thank You!