CN108333637B - Method for improving accuracy of determining element content by element logging technology - Google Patents

Method for improving accuracy of determining element content by element logging technology Download PDF

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CN108333637B
CN108333637B CN201711338259.7A CN201711338259A CN108333637B CN 108333637 B CN108333637 B CN 108333637B CN 201711338259 A CN201711338259 A CN 201711338259A CN 108333637 B CN108333637 B CN 108333637B
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CN108333637A (en
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刘军涛
刘树才
张锋
李福生
苗彬
杨传乐
张泉滢
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Lanzhou University
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    • G01MEASURING; TESTING
    • G01VGEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/04Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
    • G01V5/08Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
    • G01V5/10Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
    • G01V5/101Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources and detecting the secondary Y-rays produced in the surrounding layers of the bore hole

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Abstract

The invention discloses a method for improving accuracy of determining element content by an element logging technology, and particularly relates to the technical field of oil and gas logging. The method solves the problem that when the element content is determined by the existing element logging technology, a fixed set of element standard spectrum is utilized, and the accuracy of the element content is influenced. The method specifically comprises the following steps: building a calibration tank of the element logging instrument; constructing a numerical calculation model by using a numerical simulation method; improving a numerical simulation program to obtain a numerical calculation program capable of recording the reaction type, position and time of the reaction between neutrons and formation elements and the energy of released gamma rays; measuring in a calibration tank by using an element logging instrument, and performing benchmark verification on a numerical calculation program by using measured energy spectrum data; establishing a plurality of element standard spectrum libraries under different logging conditions for actually measured data processing; and calculating fitting errors of different standard spectrums by adopting a loop iteration method, selecting a set of standard spectrums with the minimum fitting errors, and calculating skeleton elements.

Description

Method for improving accuracy of determining element content by element logging technology
Technical Field
The invention relates to the technical field of oil and gas logging, in particular to a method for improving the accuracy of determining element content by an element logging technology.
Background
The element well logging technique is characterized by that it utilizes the action of neutron source to produce neutron, utilizes the inelastic scattering and radiation capture action of neutron and stratum material to collect gamma energy spectrum data produced by said action so as to define the content of stratum skeleton elementA well logging method. Currently, the main element logging instruments mainly include an ECS of schrenki, a GEM of harebilton, a FleX of beckhaus, a Lith Scanner of schrenki, an FEM of a medium oil well logging company, a PNST of a daqing oil field testing service company, and the like. The element logging instrument is used for measuring underground, non-elastic and capture gamma energy spectrums are collected, the measured energy spectrums are processed by utilizing a standard gamma energy spectrum library of elements, and then the yield and the content of the stratum skeleton elements are calculated. A standard gamma energy spectrum library of the formation elements is established by a calibration tank or a numerical simulation method. Srenberg, Beckhols, Medium oil logging corporation by construction of the composition SiO2、CaCO3And a scale barrel for S and other substances obtains a standard energy spectrum library of Si, Ca and other elements. A stratum model of the stratum composition oxide corresponding to the element can be established through a numerical simulation method, and a set of element standard gamma spectrum library for actually measured data processing is established.
However, during logging, the logging conditions at different depth points may change, such as formation porosity, density, borehole size, drilling fluid type, etc. When the logging conditions change, the spatial flux distribution of neutrons generated by the neutron source changes. Therefore, the generating position of the inelastically scattered and captured gamma rays can be changed, and the path of the gamma rays reaching the detector is influenced. The shape of the standard gamma spectrum of a single element can be affected. If a fixed set of standard gamma spectrum libraries of elements are used, the measured gamma spectra are processed, which can affect the accuracy of the determination of the element content.
US patents with patent numbers US7366615(04/2008), US5471057(11/1995), US20110218735(09/2011), chinese patents with patent numbers CN103696765(11/2013), CN102084271(06/2009), CN102518431(06/2012), CN104329075(09/2014), CN105182422(09/2015), CN 105629319A.
Zhenghua et al PNST-E pulse neutron stratum element well logging technique research, well logging technique 2015, volume 39 (phase 4)
Yuan-Chao et al. Gamma-spectrum based element well log development and technological prospects 2014 geophysical evolution 2014, 29 (4 th)
Liu war et al, shale gas blanket pulsed neutron element logging monte carlo research, well logging techniques 2015, volume 39 (volume 5).
Liu military billows, etc. pulse neutron element logging instrument MC benchmark experiment and instrument standard spectrum simulation [ C ]// Chinese nuclear science and technology progress report 2013.
The above patents or documents describe the existing methods for obtaining some element standard spectra and determining element content, wherein, bushy, liu military billows and the like describe a method for establishing a fixed set of stratum element standard spectra; in the aspect of element content determination, a fixed set of element standard spectrums are utilized, but when logging conditions are changed, such as different borehole sizes, different types of drilling mud and the like, the shapes of the element standard spectrums are changed. The accuracy of the element content calculation is affected by processing and measuring the energy spectrum data by using a fixed set of element standard spectra.
Aiming at the defects of the existing element logging for determining the element content, the invention introduces a method for improving the accuracy of determining the element content by an element logging technology by establishing a plurality of sets of element standard gamma energy spectrum libraries under different stratum conditions and utilizing a method of cyclic iterative computation.
Disclosure of Invention
Aiming at the defects, the invention provides a method for improving the accuracy of determining the content of elements by an element logging technology by establishing a plurality of sets of element standard gamma energy spectrum libraries under different stratum conditions and utilizing a method of cyclic iterative computation.
The invention specifically adopts the following technical scheme:
a method for improving accuracy of element content determination by an element logging technology specifically comprises the following steps:
a. building a scale tank of the element logging instrument, wherein the middle of the scale tank is in an annular shape, and filling materials consisting of known elements are added into the scale tank;
b. adopting an element logging instrument, a filling material and a scale tank to construct a numerical calculation model, wherein the filling material is filled into the scale tank, and the element logging instrument is inserted into the filling material;
c. improving a numerical simulation program, and obtaining a numerical calculation program for recording the reaction type, the position and the time of the reaction of the neutrons and the formation elements and the energy of the generated inelastic scattering and radiation capture gamma rays;
d. measuring in a calibration tank by using an element logging instrument, and performing benchmark verification on a numerical calculation program by using energy spectrum data obtained by measurement;
e. establishing stratum models with different porosities, borehole sizes, drilling mud types or oil-gas-containing properties, wherein frameworks are corresponding oxides of different elements respectively, and acquiring a plurality of sets of standard element gamma energy spectrum libraries under different logging conditions for storage and then using the gamma energy spectrum libraries for actual measurement data processing;
f. and processing the actually measured energy spectrum data of the element logging instrument by respectively utilizing a plurality of different sets of standard element gamma energy spectrum libraries by adopting a cyclic iteration method, calculating the fitting error of each iterative calculation, selecting one set of standard element gamma energy spectrum library with the minimum fitting error, calculating to obtain the yield of each element of the stratum, and finally calculating to obtain the content of the skeleton element.
Preferably, the element logging instrument comprises a shell and a ground control system, wherein a neutron source, a neutron shielding body, a gamma crystal detector, a photomultiplier, an underground control and acquisition circuit and the ground control system are sequentially connected in the shell from bottom to top.
Preferably, the standard element gamma spectrum library comprises Si, Ca, S, Fe, S, Ti, Gd, Cl, H, K and Al.
Preferably, the scale pot is horizontal, the radius of the outer ring is more than 80cm, and the radius of the inner ring is 10 cm.
Preferably, the numerical calculation program can calculate the element standard spectrum under different logging conditions.
The invention has the following beneficial effects:
by the method, the influence of the shape change of the element standard spectrum on the element content calculation under different logging conditions is overcome, and the accuracy of determining the element content by the element logging technology is improved.
Drawings
FIG. 1 is a schematic flow chart of a method for improving the accuracy of elemental content determination by elemental logging techniques;
FIG. 2 is a schematic diagram of a typical formation element logging tool configuration;
FIG. 3 is a schematic structural diagram of an element logging instrument test calibration device;
FIG. 4 is a comparison of standard spectra of Si element under different logging conditions.
Wherein, 1 is neutron source, 2 is the neutron shield body, 3 is gamma crystal detector, 4 is photomultiplier, 5 is control and acquisition circuit in the pit, 6 is ground control system, 7 is the scale jar.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings:
as shown in fig. 1 to 3, a method for improving accuracy of determining element content by an element logging technology specifically includes:
the framework and the filling material are of a composition structure of a simulated stratum, the stratum simulated by the framework is richer, and the stratum simulated by the filling material is relatively simple.
a. A scale tank of the element logging instrument is built, wherein the middle of the scale tank is in an annular shape, a filling material consisting of known elements is added into the scale tank, the filling material can be quartz sand, the composition of the quartz sand is 99% of quartz, and the feldspar content is 1%.
b. Establishing a numerical calculation model by adopting parameters of the element logging instrument, a filling material and a scale tank 7, wherein the filling material is filled in the scale tank, the filling material can be the quartz sand, and the element logging instrument is inserted into the filling material;
the element logging instrument comprises a shell and a ground control system, wherein a neutron source 1, a neutron shielding body 2, a gamma crystal detector 3, a photomultiplier tube 4, an underground control and acquisition circuit 5 and the ground control system 6 are sequentially connected in the shell from bottom to top.
c. Improving a numerical simulation program to obtain a numerical calculation program capable of recording the reaction type, position and time when neutrons act with stratum elements and generating energy of inelastic scattering and radiation capture gamma rays;
d. measuring in a calibration tank by using an element logging instrument, and performing benchmark verification on a numerical calculation program by using energy spectrum data obtained by measurement;
e. establishing stratum models with different porosities, borehole sizes, drilling mud types or oil-gas-containing properties (the porosity of the stratum models can be respectively 0%, 5%, 10%, 15%, 20%, 30% and 40%), wherein skeletons of the stratum models are respectively corresponding oxides of different elements, and establishing stratum models with borehole radii of 6cm, 8cm, 10cm, 12cm and 16 cm; establishing a stratum model with drilling fluid respectively being fresh water and barite slurry (water, barite and bentonite); finally, a plurality of sets of standard element gamma energy spectrum libraries (the standard element gamma energy spectrum libraries comprise Si, Ca, S, Fe, S, Ti, Gd, Cl, H, K and Al) under different logging conditions are obtained and stored for actually measured data processing; as shown in fig. 4, the standard spectrum of Si element is obtained under the condition that the borehole fluid is fresh water and barite slurry, respectively, and it can be seen that different logging conditions have an influence on the shape of the standard spectrum of element.
f. And processing the actually measured energy spectrum data of the element logging instrument by respectively utilizing a plurality of different sets of standard element gamma energy spectrum libraries by adopting a cyclic iteration method, calculating the fitting error of each iterative calculation, selecting one set of standard element gamma energy spectrum library with the minimum fitting error, calculating to obtain the yield of each element of the stratum, and finally calculating to obtain the content of the skeleton element.
The formation skeleton is processed into SiO by using the invention and the existing element well logging processing method (based on a set of fixed element standard spectrum and an oxide model to carry out element content conversion)2、Al2O3And MgO and FeO, when the drilling mud is fresh water mud and barite mud respectively, the stratum instrument measures the obtained capture gamma energy spectrum data, and the content of the stratum framework element is calculated. In the process of calculating the element content, the existing element content determining method and the method of the invention are respectively adopted, and the ratio of the element content calculation result and the actual value of the two is shown in table 1.
TABLE 1
Figure BDA0001507817880000041
As can be seen from Table 1, the calculation accuracy of the element content is affected by processing the energy spectrum data measured by the element logging instrument under different logging conditions by the existing method. The accuracy of calculating the content of the stratum skeleton element by using the method is improved.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.

Claims (4)

1. A method for improving accuracy of element content determination by an element logging technology is characterized by specifically comprising the following steps:
a. building a scale tank of the element logging instrument, wherein the middle of the scale tank is in an annular shape, and filling materials consisting of known elements are added into the scale tank;
b. adopting parameters of an element logging instrument, a filling material and a scale tank to construct a numerical calculation model, wherein the filling material is filled into the scale tank, and the element logging instrument is inserted into the filling material;
c. improving a numerical simulation program to obtain a numerical calculation program capable of recording the reaction type, position and time when neutrons act with stratum elements and generating energy of inelastic scattering and radiation capture gamma rays; the numerical calculation program can calculate and obtain element standard spectrums under different logging conditions;
d. measuring in a calibration tank by using an element logging instrument, and performing benchmark verification on a numerical calculation program by using energy spectrum data obtained by measurement;
e. establishing stratum models with different porosities, borehole sizes, drilling mud types or oil-gas-containing properties, wherein frameworks are corresponding oxides of different elements respectively, and acquiring a plurality of sets of standard element gamma energy spectrum libraries under different logging conditions for storage and then using the gamma energy spectrum libraries for actual measurement data processing;
f. and processing the actually measured energy spectrum data of the element logging instrument by respectively utilizing a plurality of different sets of standard element gamma energy spectrum libraries by adopting a cyclic iteration method, calculating the fitting error of each iterative calculation, selecting one set of standard element gamma energy spectrum library with the minimum fitting error, calculating to obtain the yield of each element of the stratum, and finally calculating to obtain the content of the skeleton element.
2. The method of claim 1, wherein the element logging tool comprises a housing and a surface control system, and the neutron source, the neutron shield, the gamma-ray detector, the photomultiplier, the downhole control and acquisition circuit and the surface control system are sequentially connected to the housing from bottom to top.
3. The method of claim 1 or 2, wherein the standard element gamma spectrum library comprises Si, Ca, S, Fe, S, Ti, Gd, Cl, H, K, and Al.
4. The method of claim 1, wherein the graduated cylinder is horizontal, the outer ring has a radius greater than 80cm, and the inner ring has a radius of 10 cm.
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