Gamma Ray â Spectralog

Gamma Ray – Spectralog

Different gamma ray tools.TheoryHow do’sInterpretation

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Radiation Theory --- Module 1

Objectives:– Characteristic of Gamma Rays (radiation).

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AtomAtoms is smallest piece of an element

that keeps its chemical properties. Most atoms are composed of 3 types of

massive subatomic particles which govern their external properties:–electrons, which have a negative charge; –protons, which have a positive charge;

and –neutrons, which have no charge.

–(I have a problem with the word “massive” when discussing subatomic particles. It would be better if the word was left out)

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Model of the Atom

This image represents the shape of the atomic orbitals. The clouds depict the probability distribution of an electron bound to a Hydrogen nucleus

n=3, l=2, m=0 (This needs to have a better explanation)

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The nucleus

The atomic nucleus is the center of an atom. The nuclei of the atoms are composed of protons and neutrons held

together by the strong nuclear force. The number of protons in the nucleus determines the chemical

properties of the atom and which chemical element it is.The number of protons in an atomic nucleus is called the atomic

number, and determines which element the atom is. The number of neutrons determines the isotope of the element.

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The nucleus

Protons and neutrons have nearly equal masses, and their combined number, the mass number, is approximately equal to the atomic mass of an atom.

Because the electromagnetic force is many orders of magnitude stronger than the gravitational force, the charge on the proton must be equal and opposite to the charge on the electron.

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Elements

Atoms are generally classified by their atomic number, which corresponds to the number of protons in the atom.

The atomic number defines which element the atom is.For example, carbon atoms are those atoms containing 6 protons.

All atoms with the same atomic number share a wide variety of physical properties and exhibit the same chemical behavior.

The various kinds of atoms are listed in the periodic table in order of increasing atomic number.

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Isotopes

The mass number, atomic mass number, or nucleon number of an element is the total number of protons and neutrons in an atom of that element, because each proton or neutron essentially has a mass of 1 amu.

The number of neutrons in an atom has no effect on which element it is.

Each element can have numerous different atoms with the same number of protons and electrons, but varying numbers of neutrons.

Each has the same atomic number but a different mass number. These are called the isotopes of an element.

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Isotopes

The simplest atom is the hydrogen atom, which has atomic number 1 and consists of one proton and one electron.

The hydrogen isotope which also contains 1 neutron is called deuterium or hydrogen-2; the hydrogen isotope with 2 neutrons is called tritium or hydrogen-3.

Hydrogen Deuterium Tritium

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Radiation

Radiation is energy in transit in the form of high speed particles and electromagnetic waves.

They make up our visible light, radio and television waves, ultra violet (UV), and microwaves with a large spectrum of energies.

These examples of electromagnetic waves do not cause ionizations of atoms because they do not carry enough energy to separate molecules or remove electrons from atoms.

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The Electromagnetic Spectrum

The electromagnetic (EM) spectrum is the full range of frequencies

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The Electromagnetic Spectrum

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The interaction of radiation with matter

http://hyperphysics.phy-astr.gsu.edu/hbase/mod3.html






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Radiation

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Quiz

What is an isotope?– An element with different atomic number and same mass.– An element with the same atomic number but different mass.– An element with different mass and atomic number.

Final answer

– An element with the same atomic number but different mass. Comment: in order to do it, the element needs to have the same

number of protons, but different number of neutrons.

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Quiz

What is radiation?-It is an unstable material goes to the stable material, emitting

radiation.-It is a stable material going to the unstable material emitting

radiation.

AnswerIt is an unstable material goes to the stable material, emitting

radiation.Comments: Radiation is energy in transit in the form of high speed

particles and electromagnetic waves.

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Gamma ray Theory – Module 2

Objectives:– Characteristic of Gamma Rays.– Different energy. How we measure it.

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Gamma Radiation

Gamma ray sources have long range ionization. Gamma rays cause little ionization Gamma rays are very penetrative

Physical characteristics No mass No charge. High speed ( 186,000 miles per second)

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Gamma properties

Have long range ionization than β. – It means, more space between you and gamma rays.

Cause a little ionization.– It means, you need a lot of gammas to be dangerous.

Are very penetrative.– It means, its are difficult to stops.

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Gamma – Physical Char.

No mass. – Rays with wavelength small than light.

No charge.– Like a light, sometimes is a ray sometimes is a particle.

Very high speed.– Compare with light.

Ex: Cs 137 decay.

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Interesting

In Gamma rays only– Photo Ionization - < .5 Mev– Compton Scattering - < 1.02 Mev– Pair production - > 1.02 Mev

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Gamma Ray Interaction

Photo Ionization - gamma ray energy < .5 MevA gamma ray strikes an orbital electron. The electron absorbs all of the gamma ray's energy and flies from the atom. This creates two ions: the negative electron, and the positive atom. These two ions can now induce their own secondary ionization which implies the presence of a gamma ray, even though the gamma ray no longer exists.

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Compton Scattering - gamma ray energy < 1.02 MevA gamma ray strikes an electron, however all of the energy of the gamma ray is not absorbed by the electron. The electron flies from the atom and the gamma ray continues on a slightly deflected path.

Gamma Ray Interaction (cont.)

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Gamma Ray Interaction (cont.)

Pair Production - gamma ray energy > 1.02 MevA gamma ray creates a negative electron and a positive electron. The positive electron combines with an electron to form a positroneum with a mean life of 10(-10) seconds. At the end of this short life the two are mutually annihilated and the mass of this binary system is converted into energy and two .51 Mev photons are produced, traveling at 180 to each other.

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Quiz

What are the different interaction with matter?– Ionization, scattering, and isotopes.– Photo ionization, Compton and pair production.– Atom, proton and electron.– Frequency, collisions and damaging.

– Answer – Photo ionization, Compton and pair production.

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Detectors – Module 3

Objectives:– Different energy levels. How are they measured?– Identify different components of the spectrum.

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What do we measure?

It is impossible to directly measure gamma rays. We need something to translate gamma rays to electrical pulses. This is done with detectors. Gamma rays react with elements in the detectors to generate

electrical pulses. Therefore, the number of pulses is directly related to the number

of gamma rays coming from the formation.

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Radiation Detectors

Ionization chambers Proportional Counters Geiger Muller Crystal scintillations

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Radiation Detectors Ionization chambers

– Are the class of radiation detectors in which the radiation produces ionization events in a gas.

– The gas is contained in a chamber equipped with two electrodes which differ in potential by several hundred to a thousand volts.

– Ion pairs formed by the incident radiation travel to the positively and negatively charged electrodes.

– The charge collected (or current) is a measure of the strength of the external radiation source.

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Ionization Chambers

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Ionization Chambers

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Proportional Counter

– Similar to ionization chamber. The operating voltage between the anode (center wire) and cathode (cylinder) is more than 1000 volts.

– Primarily used as epithermal and thermal neutron detectors. – The cylinder is filled with an active gas (He ) pressurized to 10

atmospheres. –When used as a epithermal neutron detector, the cylinder is

encased in a nylon sleeve which acts as a moderator and has a cadmium shield.

– Detection begins with the absorption of neutrons by the atoms of He .

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Proportional CounterAdvantages Fairly rugged and temperatures to 400 F tolerated Signal pulses large enough to be easily counted Pulse strength proportional to the energy level of the radiation particles detected by the

counter.Disadvantage Dead TimeApplication Sidewall Neutron 2404, 2406 Gamma Ray / Neutron 2418, 2435, 2438, 2446 Compensated Neutron

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Geiger Muller

– Similar to proportional counter. – Lower operating voltage (700 volts) causes ion multiplication

anywhere in the tube and not just near the anode. – Gamma ray detection begins in the wall of the tube where the

gamma ray interacts with the platinum coating by means of Compton scattering.

– This results in the emission of electrons into the active volume of the tube.

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Geiger Muller

– A free electron will cause secondary ionization as in interacts with the filling gas which can be neon, argon, or a mixture of the two.

– An avalanche of electrons is produced by ion multiplication. – A single electron can cause the entire tube to discharge. – For this reason, the GM tube cannot differentiate low energy

radiation from high energy radiation, nor can it differentiate the various types of radiation.

– A quenching gas (usually a halogen such as chlorine or bromine), is responsible for preventing continuous discharge.

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Geiger MullerAdvantage Fairly rugged and temperatures of 400 F tolerated Signal pulses quite large and easily counted Sensitive to a wide range of radiation energy. Operating voltage does not affect the response of the tube.Disadvantage Low efficiency when used to detect gamma rays. (Tubes used in bundles) Dead TimeApplication Compensated Densilog Nuclear Flolog Fluid Density PFC Nuclear Orientor

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Geiger Muller

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Scintillation counters

Scintillation counters have been in use since the beginning of the century, making use of the property of certain chemical compounds to emit short light pulses after excitation by the passage of charged particles or by photons of high energy.

It has two parts.– Crystal detector, translate gamma rays to light.– Photomultiplier, translate light in electrical pulse.

Each amplitude is proportional to the energy of the gamma ray.

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Logging tool

Gamma Ray photon enters crystal

Flash of light emitted Light strikes photo cathode

and knocks off electrons Signal amplified in PM tube Resultant voltage “spike”

proportional to Gamma Ray energy Photomultiplier

Crystal

“V”

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Scintillation countersAdvantages High counting efficiency of 50 - 60 % for gamma rays Short length allows for good bed response High speed detection and high count rate capabilities ProportionalityDisadvantages Fragile Temperature sensitiveApplications Gamma Ray, Spectralog 2420 Compensated Neutron Z-Density Dual Scintillator Density PDK, MSI, C/O 735, 736 PFC

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Crystal and Photomultiplier

Crystal detectorPhotomultiplier Magnetic shield

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1329 Digital Spectralog Tool

The 1329XB DSL contains a high resolution 2”x12” Cesium Iodide (CsI) crystal optically coupled to a photo-multiplier tube (PMT).

An advantage of a CsI crystal over other crystal detectors is the severe conditions of shock and vibration it can withstand.

When a gamma ray of specific energy interacts with the crystal it is converted to a light pulse (photon).

The intensity of this light is proportional to the gamma ray's energy and is converted into an electronic pulse and amplified by the PMT of the detector section.

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Spectrum Control–During logging effects of temperature and pressure on the DSL

instrument will cause the tool response to drift slightly. –To combat this the acquired spectrum is monitored constantly by the

Engineer to ensure that the energy peaks remain in the correct spectrum windows. –This is done by adjusting the high voltage input to the tools detector

assembly by manual and automatic gain changes.

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Gamma Ray Log

The basic GR log is a recording of the natural occurring radioactivity of formations.

Some rocks are naturally radioactive by virtue of the scattered unstable elements they contain. – Uranium (U), – Thorium (Th), – Potassium (K)

Those elements continuously emit gamma rays, which are short bursts of high-energy radiation similar to X-rays.

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Quiz

Why have scintillation detector been chosen for the majority of the radioactive tools?

Answer– Because,– The output pulses are proportional to the energy.– Are more efficient than the other kind of detectors.

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Module 4

Objectives:– Differentiate between different GR tools– Be able to define the GR API unit.– Identify different components of the spectrum.– Identify different component of the spectrum (x,y axis)(You are saying the same thing as the previous bullet)

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Gamma Ray Log1. The response of all types of gamma ray tools are

calibrated so as the pulses per second can be read in American Petroleum Institutes (API) Gamma Ray units.

2. An API Gamma Ray Units 1/200 of the response generated By a calibration standard, which is an artificial formation containing precisely known quantities of uranium, thorium, and potassium maintained by the API in Houston.

3. Philosophy is the same as the “master meter” or the or the “feet” concepts.• It is a complete arbitraries measurement. • “Feet”, is the distance that Henry the King has in

his feet.• “Meter” is the same distance than one piece of

material has in one office in Paris.

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Gamma Ray Log Applications

Gamma Ray logs are effective in distinguishing permeable zones – by virtue of the fact that the radioactive elements tend to be

concentrated in the shales, which are impermeable,

– and are much less concentrated in carbonates and sands, which are generally permeable.

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Depth Correlation– Helps the engineer to be on depth with a previously recorded GR

log in the same well, Cased Hole or Open Hole. Well to well in an area. This is possible due to the fact that GR logs are highly repeatable

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Lithology Identification – Care must be taken when using the recorded GR curve to identify

lithology. It indicates shale or not shale

– This is because shale formations contain mostly clay materials. A high GR reading is obtained in a Shale.

– Oil reservoirs such as sandstones and limestones basically do not have high radioactivity levels, hence exhibit low GR reading.

– Dolomite and conglomerates (also reservoir rocks) exhibit low to medium GR readings.

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Gamma Ray Log

Figure shows typical Gamma Ray Log responses to different types of formations.

Limestone and anhydrite have the lowest reading, 15-20 API;

dolomites and clean sands have slightly higher values, about 20-30 API.

Shales average about 100 API but can vary from 75 to 150. – A few very radioactive shales

may read 200-300 API.

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The DSL differs from a gamma ray instrument - which records total gamma rays as a function of depth - in that it also measures the discrete energy of each gamma ray detected.

The discrimination of the total gamma ray signal into discrete energy levels or windows, infers the individual amounts of Potassium (K), Uranium (U), and Thorium (Th).

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In formations there are three radioactive elements of interest undergoing continuous radioactive decay.

These elements, Uranium, Thorium, and Potassium each emit characteristic gamma rays of various energy levels.

Potassium has a single distinct energy at 1.46 MeV, with Thorium

and Uranium emitting gamma rays of various energies.

The major distinction being a prominent Thorium energy peak at 2.61 MeV and a predominant Uranium energy peak at 1.76 MeV.

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The Spectralog was first introduced to the oil industry for commercial use by WALS in 1969.The WTS 1329XA Digital Spectralog (DSL) tool is used for: - correlation - lithology identification - determination of clay type and clay content - measuring bed thickness - locating uranium by-product build-up in a cased well - identifying potential fracture zones.

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Curves

GR: Gamma RayGRSL: Gamma Ray SLTHZ: Thorium Raw count RateUZ: Uranium Raw count RateKZ: Potassium Raw count RateK: Potassium (%)U: Uranium (PPM)Th: Thorium (PPM)

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Energy Peaks and Windows–The 1329 DSL acquires a 256 channel spectrum over an energy range of

0.15 to 3.0MeV. –The total count rate for each element is taken over a window which has the

peak energy level at its centre.

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Spectrum Channels and Energy Levels

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What is the spectrum?

What is the political spectrum from the USA?

Parties names

Number of parties

Number of people

A BC

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In our company

Two kind of spectrums.

– Time spectrum, call MCS (multi-channel-scaled).

– Energy spectrum or PHA (pulse-high-analyzer).

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MCS or multi channel scaled

It is based in time decay.

We use it in PDK and RPM tools.

Time channels

Number of pulses Each channels is one gate, it means, how many pulses it counts during each gates

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How the spectrum is making

CPUFPGA

How many pulses are count in certain time frame and are writing in a memory place

CPU read the 256 memory location for the different time

gates

Time spectrum

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PHA or pulse high analyzer

It is based in energy.– It means energy, channels, or volts.– We need to add and A/D converter prior the Spectrum analyzer.

Time

Energy, Channels, Volts

Number of counts

Amplitude, volts

Number of pulses with this amplitude in a time constant period of time

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How the spectrum is making

A/D

Pulse amplitude in 8 bits digital format (256).It is the address for a memory ram.

256 RAM Locations

CPU

CPU read in this memory location what the number is and

add one.

After certain time the CPU read the 256 positions and send it to the surface.

PHA spectrum

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Quiz

What is in the “y” axis?– Counts per seconds.– Channels, energy or amplitude in volts.– Frequency

AnswerChannels, energy or amplitude in volts.

What is in the “x” axis?– Counts per seconds.– Channels, energy or amplitude in volts.– Frequency

Answer Counts per seconds.

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Repeatability

Gamma Ray–Repeatability should be within ± 3 to 5 API units.

Spectralog–Repeatability should be within the following:

K = ± 10% of reading U = ± 7% of reading Th = ± 7% of reading

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Tool Design -- Module 5

Objectives:

• Differentiate between different GR tools.

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1309 Gamma Ray

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1339XA Replacement for the 1309

The Gamma Ray has the following features:– Vacuum Flask insulated Detector Section– Integrated AC and DC Power Supplies– Gamma circuitry that has a synchronous 4-stage counter providing

a full count rate output or outputs divided by 2, 4, or 8.– Solid State self-regulating high voltage circuitry– Rotary and Toggle switches to select signal carrying conductors,

signal types, AC/DC operation, and positive/negative signal polarity.

– Logging speed has been increased up to 150 ft/min

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1339XA

EQUIPMENT SPECIFICATION SHEETReplacement for the Atlas 1309 Series

BAKER ATLAS P/N........................................F130978000 1339XA GAMMA RAY

Temperature......................................................................400°F (204°C) for 1 hr.............................................................................................300°F (149°C) for 8 hrs

Maximum Pressure...............................................................................20,000 PSI

Length ..................................................................................... 67.4 in. (171.1 cm)

Weight ........................................................................................... 110 lbs (50 kg)Detector Type............................. (Scintillation) 1.88 in. diameter by 12 in. long

Power (cable head).................................................................180 V AC @ 15 mA................................................................................................. 150 V DC @ 40 mA

Max. Logging Speed..............................................................................150 ft/minCable Type............................................................DC Supply: Single Conductor............................................................................... AC Supply: Multi. Conductor

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1339XA

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1339XA

GENERAL INFORMATION– This 1339XA is also referred to as the 3 3/8 O.D. Gamma Ray

and it is an improved replacement for the 1309XA 3-5/8 O.D. Gamma Ray tools.

– The Baker Atlas part number assigned is (p/n) F130978000 1339XA GAMMA RAY

– This asset has been assigned the series number 1339XA Gamma Ray Tool. (Baker Atlas#)

– The parts for Titan have the kit p/n 10086702 KIT, Titan Gamma Ray Tool.

– The tool is 3 3/8 diameter and is 62 inches from shoulder to shoulder (Top Sub to Bottom Sub).

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The DSL differs from a gamma ray instrument - which records total gamma rays as a function of depth - in that it also measures the discrete energy of each gamma ray detected.

The discrimination of the total gamma ray signal into discrete energy levels or windows, infers the individual amounts of potassium(K)uranium(U)thorium(Th)

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1329 Digital Spectralog

Energy Peaks and WindowsThe 1329 DSL acquires a 256 channel spectrum over an energy range

of 0.04 to 3.5MeV. The total count rate for each element is taken over a window which has the peak energy level at its centre.

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1329 Specifications

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1329 Specifications

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Subsets and acquisition Software

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Data Transmission

Subset #0: SL spectrum subset sent uphole and processed at surface. M5 telemetry.

Subset #1:SL total counts summed downhole and sent to surface as GR. M2 telemetry.

Subset #15: SL internal flask temperature (W08F). M2 telemetry.

Subsets #1 and #15 are grouped together as one ACT by default in every OCT.

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Sample RatesData is typically acquired at 4 samples/foot (13.12 samples/meter),

which is a finer resolution than the vertical bed resolution of the instrument.

Other sample rates are available as defined by the ACT’s available within the OCT being used, these are normally 2/ft or 8/ft.

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Quiz

The 1329 spectralog send the spectrum by:– Mode 2– Mode 5– Mode 7

AnswerMode 5

The 1329 spectralog send GR by:– Mode 2– Mode 5– Mode 7

AnswerMode 2

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Calibration issues

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Objectives

Identify GR calibrator and sources characteristics. Be able to position it on each GR tool.

Be able to follow BA Rad source handling procedures, relevant to the GR tools.

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CALIBRATION THEORYThere are two calibration routines available for the DSL:1. GR: Calibration of total counts acquired in GR API units.2. SL-II: Calibration of spectrum data using Spectralog II processing.

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Calibration Theory

Calibration Requires a Standard Secondary Standards must be made for field use

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GR S2K Calibrator Position on 1329.

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Source Characteristic and rad procedures link.

http://insource/hse2/atlas/level_3/atlasglobal3.pdf

http://insource/hse2/atlas/level_3/atlasglobal3.pdf

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Quiz

What is the GR calibrator source material?– Cs– Cd– Ra

Answer– Ra

What is the activity of the GR calibrator source?– 2.5 Ci– 2.5 mCi– 2.5 µCi

Answer2.5 µCi

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1329 Digital Spectralog – normal presentations

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Quality control

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Gamma Ray â Spectralog