CN101255793B

CN101255793B - Impulse neutron complete spectrum saturability logging instrument variable parameter neutron pulse timing mode

Info

Publication number: CN101255793B
Application number: CN 200810017840
Authority: CN
Inventors: 赵智勇; 张德民; 杨金锁; 宋胜泽; 王庆; 徐建平; 汪永安; 杨联会; 杨连会; 董谦; 石丽云
Original assignee: China Petroleum Dagang Oilfield Test Co Ltd; XI'AN AOHUA ELECTRONIC INSTRUMENT CO Ltd
Current assignee: China Petroleum Dagang Oilfield Test Co., Ltd.; Xi'an Austrian electronic instrument Limited by Share Ltd
Priority date: 2008-03-28
Filing date: 2008-03-28
Publication date: 2013-09-18
Anticipated expiration: 2028-03-28
Also published as: CN101255793A

Abstract

The present invention relates to a neutron pulse timing mode for pulse neutron whole spectrum saturation logging tool, emitting rapid neutron continuously by broad pulse design, and adding the neutron emitting time corresponding, resolves technique problem that great fluctuation error of Sigma parameter in present neutron pulse timing mode cause Sigma detecting well data can't be used, enhances the gate counting rate of monitoring Sigma and reduces the fluctuation error of Sigma parameter, reaches the similar effect near to result by special Sigma measuring apparatus.

Description

Pulsed neutron is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely

Technical field

The present invention relates to a kind of pulsed neutron and compose saturation ratio logging instrument neutron pulse timing mode entirely.

Background technology

The neutron pulse timing mode that its carbon/oxygen log mode of the same quasi-instrument of existing measurement ∑ parameter (the calorimetric neutron-capture cross section ∑ of holding concurrently) adopts all belongs to the preset parameter pattern.Because the parameter in the neutron pulse timing mode that adopts configures in advance, when neutron life-span τ value hour, thermal neutron is decayed very fast, causes the time of one-period back not take full advantage of, and causes a counting rate very low.Although logging speed very low (60 meter per second), the scintillation error of the ∑ parameter that monitors is very big, so that the ∑ well-log information can't be used.

Summary of the invention

The purpose of this invention is to provide a kind of pulsed neutron and compose saturation ratio logging instrument variable element neutron pulse timing mode entirely, it has solved the very big technical problem that causes the ∑ well-log information to use of the scintillation error of ∑ parameter in the background technology.

Technology solution of the present invention is:

1, a kind of pulsed neutron is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely, and its special character is that it comprises following setting:

1] establishing neutron life time log neutron unit cycle time is T, and heat-obtaining neutron-capture cross section ∑ measurement period T b=nT (n＞1) gets neutron pulse large period Ta=mTb, then carbon-to-oxygen ratio measurement period T c=(m-1) nT (m＞1); Neutron tube emission fast neutron in the T time quantum that begins in the Tb cycle, Tc comprises a plurality of Δ t2 minor cycles in the cycle, neutron tube emission fast neutron requires to determine Δ t1 and Δ t2 according to carbon/oxygen log in the Δ t1 time in the Δ t2 minor cycle, and Δ t1 and Δ t2 are fixed value after determining;

2] when the neutron lifetime τ value scope of the capture cross-section ∑ correspondence on the oil drilling stratum of measured stratomere was 50～120 μ s, then neutron life time log neutron unit cycle time was got T; When τ value scope was 95～210 μ s, then T was got in neutron life time log neutron unit cycle time; When τ value scope was 165～365 μ s, then neutron life time log neutron unit cycle time was got

T; When τ value scope was 285～600 μ s, then 3T was got in neutron life time log neutron unit cycle time.

The span of said n and m is: n=7～12, m=7～11.

The preferable value of said n and m is: n=9.5, m=9.

When above-mentioned τ value scope is 95～210 μ s, select T=200 μ s.

The preferable value of above-mentioned Δ t2 and Δ t1 is: Δ t2=100 μ s, described Δ t1=10.5 μ s.

The present invention has following advantage:

1, the present invention proposes a kind of variable element neutron pulse timing mode, overcome the low defective of existing preset parameter mode door counting rate, by adopting the broad pulse design to continue the emission fast neutron, add the relatively-stationary NEUTRON EMISSION time, improved the door counting rate of monitoring ∑ greatly, thereby reduced the scintillation error of ∑ parameter measurement, reached the effect that approaches with special ∑ well-log information.

When 2, stratum neutron lifetime τ value changed, so time quantum T respective change was the corresponding improve of door counting rate in the one-period.

3, the present invention has realized that the average of neutron tube ion gun dutycycle (ratio of namely working) is changeless, can guarantee the neutron tube operate as normal.

4, to measure the effect of carbon-to-oxygen ratio identical with existing instrument in the present invention, and the scintillation error of the ∑ well-log information that is obtained by monitoring is better than existing same quasi-instrument far away, makes the ∑ well-log information can be for normally use of geologic interpretation man.

5, the τ scope be provided with suitable overlapping, this overlapping T of preventing value near the line of demarcation frequent change and influence the measurement effect of instrument.

Description of drawings

Fig. 1 is neutron pulse timing mode time relationship schematic diagram of the present invention.

The specific embodiment

Neutron pulse timing mode of the present invention is exactly the temporal mode of neutron tube fast neutron emission.Be a large period with Ta=10Tb, it comprises Tc and two periods of Tb.Do carbon-to-oxygen ratio in the Tc period and measure, in this period arranged many Δ t2 minor cycles (the middle subcycle when being the carbon-to-oxygen ratio measurement), in the Δ t2 minor cycle, only neutron tube is launched fast neutron in the Δ t1 time.In Tb the period, do the thermal-neutron capture cross-section ∑ and measure, only the T in the beginning of Tb launches fast neutron in the time.

Δ t1 and Δ t2 are that the best demand according to carbon/oxygen log designs, in case selected, namely immobilize.For example Δ t2 selects 100 μ s, and Δ t1 selects 10.5 μ s.

The capture cross-section ∑ on oil drilling stratum, in the 7.6C.U. that is everlasting～91C.U. scope, corresponding neutron lifetime τ value is 600 μ s～50 μ s.The τ scope that this is total is divided into four less τ scopes, and they are: 50～120 μ s, 95～210 μ s, 165～365 μ s and 285～600 μ s.T is neutron life time log neutron unit cycle time, corresponding above four τ value scopes, and also to four values should be arranged, they are time quantum T: 115.47 μ s, 200 μ s, 346.41 μ s and 600 μ s.When the τ of measured stratomere value was in certain τ scope, the value of T was namely selected respective value automatically for use.Therefore, T follows the τ value great-jump-forward on tested stratum changing.Neutron period T b=9.5T, therefore, after T changed, Tb also changed.Large period Ta and Tc also and then become naturally.Variable element method that Here it is.

Quantitatively being calculated as follows of door counting rate when the present invention monitors ∑:

The multi-functional current logging instrument of the instrument of the measurement ∑ parameter of selection employing preset parameter, the special survey ∑ parameter of applicant's design and the pulsed neutron of employing pattern of the present invention are composed each one of saturation ratio logging instrument entirely, all measuring 0.1 meter well section, gathering under the condition of accumulative total door counting, door counting with the multi-functional current logging instrument of the special survey ∑ parameter of applicant design is 1, and collection result sees Table 1.As can be seen from Table 1, door counting rate height, the scintillation error of the ∑ that calculates is just little.Therefore, can count the quality that normalized value is estimated each instrument with door.

Can find out that from table 1 1/5～1/20 of the multi-functional current logging instrument of the special survey ∑ parameter that the door counting of preset parameter instrument only designs for the applicant obviously is the bad ∑ of survey.And the door counting of pattern of the present invention, no matter the τ value is big or small, always reach 62～63% of multi-functional current logging instrument, the scintillation error of the ∑ of measuring is near multi-functional current logging instrument.

Table 1

Claims

1. a pulsed neutron is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely, and it is characterized in that: it may further comprise the steps:

1] adopt the broad pulse design to continue the emission fast neutron, add the relatively-stationary NEUTRON EMISSION time: establishing neutron life time log neutron unit cycle time is T, heat-obtaining neutron-capture cross section ∑ measurement period T b=nT(n〉1), get neutron pulse large period Ta=mTb, then carbon-to-oxygen ratio measurement period T c=(m-1) nT(m〉1); Neutron tube emission fast neutron in the T time quantum that begins in the Tb cycle, Tc comprises a plurality of Δ t2 minor cycles in the cycle, neutron tube emission fast neutron requires to determine Δ t1 and Δ t2 according to carbon/oxygen log in the Δ t1 time in the Δ t2 minor cycle, and Δ t1 and Δ t2 are fixed value after determining;

2] when the neutron lifetime τ value scope of the capture cross-section ∑ correspondence on the oil drilling stratum of measured stratomere was 50～120 μ s, then neutron life time log neutron unit cycle time was got When τ value scope was 95～210 μ s, then T was got in neutron life time log neutron unit cycle time; When τ value scope was 165～365 μ s, then neutron life time log neutron unit cycle time was got

When τ value scope was 285～600 μ s, then 3T was got in neutron life time log neutron unit cycle time.

2. pulsed neutron according to claim 1 is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely, it is characterized in that: described n=7～12, m=7～11.

3. pulsed neutron according to claim 2 is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely, it is characterized in that: described n=9.5, m=9.

4. compose saturation ratio logging instrument variable element neutron pulse timing mode entirely according to claim 1 or 2 or 3 described pulsed neutrons, it is characterized in that: when τ value scope is 95～210 μ s, select T=200 μ s.

5. pulsed neutron according to claim 4 is composed saturation ratio logging instrument variable element neutron pulse timing mode entirely, it is characterized in that: described Δ t2=100 μ s, described Δ t1=10.5 μ s.