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"Multiple Source Neutron Measurement, Device, System and Use Thereof" in Patent Application Approval Process (USPTO 20150378049)

By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventor Kramer, Hermann (Calgary, CA), filed on February 18, 2014, was made available online on January 7, 2016, according to news reporting originating from

Washington, D.C.
, by VerticalNews correspondents.

This patent application has not been assigned to a company or institution.

The following quote was obtained by the news editors from the background information supplied by the inventors: "Borehole measurement devices may be used to determine formation characteristics surrounding the borehole and are typically used in wellbores drilled for the purpose of extracting natural resources, such as hydrocarbon, from the formations surrounding the borehole. Borehole measurement devices or logging tools may use different types of measurements, for example, a borehole measurement device may use gamma measurements, thermal neutron measurements, resistivity measurements or other types of measurements.

"At present there are a number of physics being employed to perform thru pipe formation evaluation and other wellbore measurements. For neutron based measurements, there are pulsed neutron thermal neutron, pulsed neutron gamma, gamma gamma, neutron thermal neutron, neutron epi-thermal neutron etc. It is noted that naming convention for down hole geophysical devices are based on source-detection physics. For example neutron thermal neutron indicates a neutron source and thermal neutron detection. Most of these systems utilize one source per physics, which will be referred to as single physics measurement. Systems that utilize one source for two physics will be referred to as a dual physics measurement. Of the currently available dual physics systems, there is one that utilizes a combination neutron thermal neutron, neutron epi-thermal neutron which can be considered the closest analogy to the Quad Neutron dual physics measurement. In addition there is a neutron thermal neutron, neutron gamma dual physics measurement device built in

Azerbaijan
.

"The Some shortcomings or disadvantages of using single physics measurements is the lack of corrections available for factors such as borehole rugosity, annular fluid changes, mineralogy, tubulars etc. To compensate for these short comings, dual detectors are used. These devices are commonly referred to as compensated devices. Another solution is to combine multiple single physics measurement devices, including compensated devices, during analysis. An example is neutron thermal neutron and gamma gamma physics, commonly referred to as neutron density measurements. Measuring thru pipe also limits the effectiveness of some of the physics. For example, gamma gamma measurements are limited because the pipe itself shields gamma and therefore there are losses as the gamma photons travel from the source thru the pipe and then again as the photon returns back to the detector. This results in low count rates and increases error in the measurements.

"Neutrons can easily penetrate pipe and therefore is a logical choice for thru pipe measurements. Of the neutron physics based measurements; pulsed neutron devices do not lend themselves to dual physics measurements. The reason is that the length of the pulsed neutron source does not allow for effective measurement spacing for the required detectors. Chemical neutron sources are much smaller and therefore can be used effectively for dual physics based measurements. The neutron epi-thermal measurement is highly sensitive to borehole rugosity and therefore not an ideal choice to determine formation parameters. The measurement industry typically uses a single neutron source measure device to collect this data. A single neutron source device is used to achieve high neutron output. A single high neutron source is used with a generally assumed spheroid geometry for the source field with the center being the source of the neutrons. Device detectors are placed near the source as to be within the field. Typically, devices are designed to have one detector as near to the source as practically possible in an axial configuration. Generally, limitations as to proximity are mechanical in nature. However, the use of a single high output neutron source has limited accuracy with respect to the data collected relating to porosity and clay volume measurements.

"Early commercial neutron logging tools comprised a single neutron source and a single neutron detector. The information derived by these tools was of rather limited value, since it did not separate the effects of formation porosity and formation salinity.

"Several approaches were taken to eliminate or at least to reduce the borehole effect on the porosity reading of a neutron well logging tool. One simple way to achieve this is to design a decentralized tool with the source and detectors pressed against one wall of the borehole.

"A dual neutron emission measure device has also been developed which alternates the source outputs. However, this results in a spheroid field geometry. In addition, the alternating source does not enhance the source field geometry and does not allow for an effective balanced 4 detector measurement system.

"A need therefore exists for a neutron source geophysical measurement device that overcomes one or more of the shortcomings observed in the industry."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "In one embodiment, the invention provides for a multi-neutron source downhole logging tool for collecting data useful in evaluating a characteristic of a formation adjacent a wellbore, the logging tool comprising: a multi-neutron source, each neutron source axially aligned for simultaneous emission of a neutron field into the formation; a short detector for detecting a neutron gamma field and a neutron thermal neutron field; and a long detector for detecting a neutron gamma field and a neutron thermal neutron field.

"In a further embodiment of the logging tool above the neutron sources of the multi-neutron source are sequentially aligned end-to-end for simultaneous emission of a neutron field into the formation.

"In a further embodiment of the logging tool above the neutron sources of the multi-neutron source are arranged to provide a preferential neutron interference field when simultaneous fields are emitted from the sources.

"In a further embodiment of the logging tool above the short detector and the long detector are situated at an optimal distance from the multi-neutron source so that the error associated with the short detector substantially cancels the error associated with the long detector.

"In a further embodiment of the logging tool above the multi-neutron source is a dual-neutron source.

"In a further embodiment of the logging tool above the logging tool further comprises a housing comprising beryllium copper.

"In another embodiment, the invention provides for a method of evaluating a characteristic of a formation adjacent a wellbore comprising: simultaneously emitting neutron fields into the formation from at least two axially aligned neutron sources; obtaining data comprising a long neutron neutron (LNN), short neutron neutron (SNN), long neutron gamma (LNG) and short neutron gamma data (SNG) from the neutron fields emitted into the formation; combining the long data with the short data to reduce error associated with the characteristic to be evaluated.

"In a further embodiment of the method above, the method further comprises the step of: optimizing a spacing of long detectors for detecting LNN and LNG relative to the multi-neutron source and short detectors for detecting SNN and SNG relative to the multi-neutron source to minimize the error associated to the characteristic to be evaluated.

"In a further embodiment of the method above, the step of simultaneously emitting neutron fields into the formation is through a wellbore casing.

"In a further embodiment of the method above, the combining step comprises the cancelation of the error associated to the long data with the error associated to the short data.

"In a further embodiment of the method above, the characteristic is neutron porosity (QTP) and is evaluated according to:

"QTP = A * ln ( SNN * LNG SNG * LNN ) + B ##EQU00001##

"wherein A and B are determined empirically and are influenced by bit size and the amount of high dense material in a volume of investigation.

"In a further embodiment of the method above, the characteristic is neutron clay (QNC) and is evaluated according to:

"QNC = A * ( C ( SNG LNG ) + D * ( SNN LNN ) ) + B ##EQU00002##

"wherein A, B, C and D are empirically determined coefficients.

"In a further embodiment of the method above, A, B, C and D are 0.004, 0, 1.9 and -1.5, respectively.

"In a further embodiment of the method above, the characteristic is neutron liquid (QNL) and is evaluated according to:

"QNL = A * ln ( LNG * SNG LNN * SNN ) + B ##EQU00003##

"wherein A and B are chosen to create the best overlay of QNL to QTP.

"In a further embodiment of the method above, the characteristic is water saturation (Sw) and is evaluated according to:

"Sw = 1 - kf ( QEP - QEL ) QEP ##EQU00004##

"wherein k=fluid factor; f=formation factor; QEP=Quad Effective Porosity (Clay Free); and QEL=Quad Effective Liquid porosity (Clay Free); and wherein QEP and QEL are determined as follows:

"QEP=QTP-QC and QEL=QL-QC

"wherein QTP=Quad Total Porosity; QC=Quad Clay Porosity; and QL=Quad Liquid Porosity; the fluid factor k=1/(MaxPor*QLgain) wherein MaxPor=WaterPor-OilPor; WaterPor is determined as follows:

"WaterPor=(12.73+ {square root over (12.73.sup.2-4*0.0966*(403.04-Waterkppm))})/(2*0.0966) OilPor is determined as follows:

"OilPor=0.1333*oilAPI+71 and QLgain is computed as

"QLgain=QNL A value/32.5.

"In another embodiment, the invention provides a method of determining the relative bulk density of a formation adjacent a wellbore through the wellbore casing comprising: simultaneously emitting neutron fields into the formation from at least two axially aligned neutron sources; obtaining long neutron neutron (LNN) field readings and long neutron gamma (LNG) field readings; converting the LNN and LNG for porosity to provide LNNpor and LNGpor respectively; and determining the relative bulk density by subtracting the LNGpor from LNNpor, wherein LNNpor and LNGpor represent the porosity converted counts.

"In another embodiment, the invention provides a method of determining the nuclear caliper of a formation adjacent a wellbore through the wellbore casing comprising: simultaneously emitting a neutron field into the formation from at least two axially aligned neutron sources; obtaining long neutron neutron (LNN) field readings and short neutron neutron (SNN) field readings; converting the LNN and SNN for porosity to provide LNNpor and SNNpor respectively; and determining the nuclear caliper by subtracting the LNNpor from SNNpor, wherein SNNpor and LNNpor represent the porosity converted counts.

"In another embodiment, the invention provides a method of determining the chemical effect of a formation adjacent a wellbore through the wellbore casing comprising: simultaneously emitting a neutron field into the formation from at least two axially aligned neutron sources; obtaining long neutron gamma (LNG) field readings and short neutron neutron (SNN) field readings; converting the LNG and SNN for porosity to provide LNNpor and LNGpor respectively; and determining the chemical effect by subtracting the LNGpor from SNNpor, wherein SNNpor and LNGpor represent the porosity converted single detector counts.

"In another embodiment, the invention provides a system for evaluating a characteristic of a formation adjacent a wellbore comprising: a logging tool for downhole use collecting data for evaluating a characteristic of a formation adjacent a wellbore, the logging tool comprising: a multi-neutron source, each neutron source axially aligned for simultaneous emission of a respective neutron field into the formation; short detectors for detecting a neutron gamma field and a neutron thermal neutron field; and long detectors for detecting a neutron gamma field and a neutron thermal neutron field; and a computer for combining the long data with the short data to reduce error associated to the characteristic to be evaluated.

BRIEF DESCRIPTION OF THE DRAWINGS

"Embodiments are described herein with references to the appended drawings, in which:

"FIG. 1 is a diagram of a single source neutron logging tool for carrying out neutron detection in a wellbore, optionally thru a casing, of formation characteristics adjacent or nearly adjacent the wellbore;

"FIG. 2 is a diagram of a drilling system for taking neutron measurements using a single neutron source;

"FIG. 3 is a diagram of an example of a single neutron source logging tool having both long and short detectors capable of taking measurements thru a wellbore casing;

"FIG. 4 depicts a further example of a single source logging tool having both long and short detectors capable of taking measurements thru a wellbore casing;

"FIG. 5 is an illustrative diagram of two individual neutron source fields;

"FIG. 6 is an illustrative diagram of two overlapping neutron source fields wherein the interference of the overlapping neutron source fields is shown with a line indicating the supporting interference;

"FIG. 7 is a diagram showing gamma field measurements taken wherein two neutron sources axially centered inside a tank with source activity spaced approximately 2'' apart with a line indicating the supporting interference;

"FIG. 8 is a diagram showing thermal neutron field plot taken wherein two neutron sources axially centered inside a tank with source activity spaced approximately 2'' apart with a line indicating the supporting interference; and

"FIG. 9 is an image of a dual-neutron emission device used to carry out some of the experimental data collection.

"FIG. 10 is a graph showing test data illustrating the slopes of the natural log of the fields of both neutron thermal neutron and neutron gamma;

"FIG. 11 is a graph illustrating the relationship on QTP gain (A) vs. various casing weights in characterizing quad neutron porosity;

"FIG. 12 is a graph showing test data illustrating the effect of varying water salinity to 32 API oil in characterizing quad neutron liquid;

"FIG. 13 is a plot showing the natural log of the detector counts against detector spacing."

URL and more information on this patent application, see: Kramer, Hermann. Multiple Source Neutron Measurement, Device, System and Use Thereof. Filed February 18, 2014 and posted January 7, 2016. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4481&p=90&f=G&l=50&d=PG01&S1=20151231.PD.&OS=PD/20151231&RS=PD/20151231

Keywords for this news article include: Patents.

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