Method for identifying natural gas hydrate by using longitudinal and transverse wave velocity increment cross plot

A technology of velocity increment and longitudinal wave velocity, which is applied in seismology, measurement devices, geophysical measurements, etc. in areas covered by water, can solve problems such as elevation identification and low reliability of natural gas hydrate, and achieve Credibility-enhancing effects

Pending Publication Date: 2021-06-11
CHINA UNIV OF GEOSCIENCES (BEIJING)
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The invention solves the problem of low reliability in identifying natural gas hydrate based on the abnormal increase in the velocity of the longitudinal and transverse waves, and clarifies the internal relationship between the increase in the velocity of the longitudinal and transverse waves and the natural gas hydrate, thereby providing strong support for accurate identification of the natural gas hydrate. The technical scheme that the present invention takes is:

Method used

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  • Method for identifying natural gas hydrate by using longitudinal and transverse wave velocity increment cross plot
  • Method for identifying natural gas hydrate by using longitudinal and transverse wave velocity increment cross plot
  • Method for identifying natural gas hydrate by using longitudinal and transverse wave velocity increment cross plot

Examples

Experimental program
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Effect test

Embodiment 1

[0065] The 204 voyage of Ocean Drilling drilled at the 1245E well site of Oregon Hydrate Ridge, and found the existence of gas hydrate. In this example, the P- and S-wave velocity logging data known at the 1245E well location are used to calculate the P- and S-wave velocity of the water-saturated formation at the well location, and the P- and S-wave velocity increment is calculated. The threshold curve is calculated according to the determined formation parameters, and the judgment is made. Whether the formation contains gas hydrate or not is compared with the actual data of the gas hydrate position.

[0066] The method for identifying gas hydrate and estimating the range of gas hydrate saturation by using the intersection diagram of formation compressional and shear wave velocity increments includes the following steps:

[0067] (1) P-wave velocity (V p0 , V s0 ), referred to as the calculated velocity, and the measured velocity of formation compressional and shear waves (V...

Embodiment 2

[0077] The 204 voyage of Ocean Drilling drilled at well position 1247B of the Oregon Hydrate Ridge, and found the existence of gas hydrate. In this example, using the known P-wave velocity logging data at the 1247B well location, the P- and S-wave velocity of the gas-bearing water-saturated formation at this well location is calculated, the P- and S-wave velocity increment is calculated, and the threshold curve is calculated according to the determined formation parameters. , to determine whether the formation contains gas hydrate, and compare it with the actual data of the gas hydrate position.

[0078] The method for identifying gas hydrate and estimating the range of gas hydrate saturation by using the intersection diagram of formation compressional and shear wave velocity increments includes the following steps:

[0079] (1) P-wave velocity (V p0 , V s0 ) and the measured formation P-s wave velocity (V p , V s ) curves are shown in Figure 4(a) and Figure 4(b);

[0080...

Embodiment 3

[0089] The 204 voyage of Ocean Drilling drilled at the 1250F well site of Oregon Hydrate Ridge, and found the existence of gas hydrate. In this example, using the known P-wave velocity logging data at the 1250F well location, the P- and S-wave velocity of the gas-bearing water-saturated formation at the well location is calculated, the P- and S-wave velocity increment is calculated, and the threshold curve is calculated according to the determined formation parameters. , to determine whether the formation contains gas hydrate, and compare it with the actual data of the gas hydrate position.

[0090] The method for identifying gas hydrate and estimating the range of gas hydrate saturation by using the intersection diagram of formation compressional and shear wave velocity increments includes the following steps:

[0091] (1) P-wave velocity (V p0 , V s0 ) and the measured formation P-s wave velocity (V p , V s ) curves are shown in Figure 7(a) and Figure 7(b);

[0092] (2)...

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Abstract

The invention belongs to the technical field of ocean energy exploration, and relates to a method for identifying natural gas hydrate by using a longitudinal and transverse wave velocity increment cross plot. The method comprises the following steps: S1, obtaining actual longitudinal wave velocity Vp and transverse wave velocity Vs; S2, calculating the longitudinal wave velocity Vp0 and the transverse wave velocity Vs0 of the water-saturated stratum; S3, calculating a longitudinal wave velocity increment delta Vp and a transverse wave velocity increment delta Vs; S4, determining a threshold curve; S5, drawing a longitudinal and transverse wave velocity increment cross plot; S6, judging whether a natural gas hydrate stratum is contained or not; S7, determining a porosity theoretical line of the natural gas hydrate; and S8, estimating the saturation range of the natural gas hydrate to be measured according to the porosity theoretical line of the natural gas hydrate. According to the method, the reliability of natural gas hydrate identification is improved, the position of the natural gas hydrate is accurately explored and identified, the dry well rate is reduced, and the drilling cost is saved; and the offshore drilling safety is ensured.

Description

technical field [0001] The invention belongs to the technical field of marine energy exploration, and relates to a method for identifying natural gas hydrates by using the intersection graph of P- and S-wave velocity increments, in particular to a method for qualitatively identifying natural gas hydrates and quantitatively estimating natural gas hydrates by using the intersection graph of P- and S-wave velocity increments Method for saturation range. Background technique [0002] Natural gas hydrate is an ice-like solid compound formed by water molecules and natural gas molecules under certain conditions such as temperature and pressure. It is flammable and has high combustion energy, also known as combustible ice. It is mainly distributed under the deep seabed or under the permafrost. Due to the advantages of wide distribution and huge reserves, natural gas hydrate is regarded as an alternative energy source for fossil fuels in the future, and has attracted widespread atte...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V1/30G01V1/28G01V1/38
CPCG01V1/306G01V1/38G01V1/307G01V1/282
Inventor 刘学伟田冬梅
Owner CHINA UNIV OF GEOSCIENCES (BEIJING)
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