A well logging method utilizing a direct current controllable neutron source to calculate a stratum density

A technology of formation density and neutron source, applied in geophysical measurement, measurement device, specific gravity measurement, etc., can solve the problems of complex timing control, radioactive danger, lack of theoretical support, etc., to reduce radioactive hazards, improve stability, simplify Effects of instrument design and data processing procedures

Inactive Publication Date: 2014-01-15
CHINA UNIV OF PETROLEUM (EAST CHINA)
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Problems solved by technology

The gamma-gamma density logging method uses a radioactive chemical source, which poses a potential radioactive hazard to the construction personnel and the surrounding environment; while the measurement results of the method using the dual source distance non-elastic gamma count ratio are affected by the hydrogen content index of the formation, the instrument A pulsed neutron source must be used, the timing control is more complicated, and most of the methods for correcting the formation hydrogen content index are empirical formulas, lacking theoretical support

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  • A well logging method utilizing a direct current controllable neutron source to calculate a stratum density
  • A well logging method utilizing a direct current controllable neutron source to calculate a stratum density
  • A well logging method utilizing a direct current controllable neutron source to calculate a stratum density

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specific Embodiment approach

[0026] A logging method for calculating formation density using a direct current controllable neutron source. Using the controllable neutron source and multi-detector system, adopting the neutron source DC working mode, recording the total neutron count and gamma energy spectrum at different positions, and calculating the formation density information. The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0027] figure 1 For the present invention design instrument detector relative position and structural profile diagram, wherein neutron tube 3 is a D-D neutron tube, direct current mode of operation; Gamma detector 5,8,11 adopts NaI crystal detector, and detector crystal length is average The source distance (the distance from the center of the gamma detector crystal to the deuterium target of the neutron tube) is 285~385mm, 675~865mm and 1000~1200mm respectively, and the ultra-far gamma detector 11 is used as a recor...

Embodiment 1

[0036] Embodiment 1: Utilize the Monte Carlo method to establish a numerical calculation model, according to figure 1The designed structure and the establishment of the numerical model parameters of the instrument are as follows: the thickness of the shield is 80mm, the length of the near-gamma detector NaI crystal is 50mm, and the source distance is 365mm; the length of the near-neutron He-3 detector is 130mm, and the inflation pressure is 1.0Mpa. The source distance is 455mm; the length of the far neutron He-3 detector is 130mm, the inflation pressure is 1.0Mpa, and the source distance is 745mm; the length of the far gamma detector NaI crystal is 100mm, and the source distance is 865mm; The length is 100mm, and the source distance is 1100mm. The neutron source is a D-D neutron tube with an energy of 2.5 MeV. The instrument sticks to the well wall for measurement. The borehole diameter is 200mm, and the borehole is filled with fresh water. The stratum structure is a cylind...

Embodiment 2

[0039] Embodiment 2: The instrument and borehole model are the same as in Embodiment 1. The stratum structure remains unchanged, and the stratum composition is set to strata with different lithologies and porosities. The R value of the response of the instrument in the stratum is simulated and calculated, and substituted into the calibration well obtained in Embodiment 1. R value response relational formula, calculated to obtain the apparent density ρ of the formation measured by the instrument a , the measured formation apparent density ρ a The relationship with the true density ρ of the formation is shown in image 3 . Depend on image 3 It can be seen that the measured apparent density ρ a It is basically consistent with the true density ρ of the formation, indicating that the method proposed by the present invention can be used to calculate the density of the formation.

[0040] Below in conjunction with accompanying drawing, be described with regard to basic principle...

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Abstract

The invention relates to a well logging method utilizing a direct current controllable neutron source to calculate a stratum density. A D-D direct current neutron source and a multi-detector measurement system comprising two neutron detectors and three gamma detectors are utilized to record a total count number of neutrons in different positions and a gamma energy spectrum, and a stratum density is calculated. The calculation of the stratum density through the utilization of the direct current controllable neutron source is realized without pulse sequential control. The design of the apparatuses and data processing processes are simplified. The stability of the apparatuses is improved, and a new means is provided for the obtaining of stratum density information in a well logging process.

Description

technical field [0001] The invention relates to the technical field of oil and gas well logging systems, in particular to a logging method for calculating formation density by using a direct current controllable neutron source. Background technique [0002] The conventional density logging method is gamma-gamma density logging, which uses a gamma source and a gamma detector to record the counts of the gamma rays generated by the gamma source entering the detector after Compton scattering in the formation. Get the formation density parameter. Recently, a logging method using secondary gamma generated by a neutron source to measure formation density has appeared at home and abroad. Most of its principles use a 14.3 MeV D-T pulsed neutron source and two gamma detectors to record the two source distances respectively. The total counts of non-elastic gamma and captured gamma are calculated using the captured gamma count ratio of the two source distances to correct the effect of ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V5/10G01N9/24
Inventor 王新光
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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