Method for identifying natural gas hydrate by using incremental ratio between wave impedance of longitudinal and traverse waves

A wave impedance, longitudinal and shear wave technology, applied in the field of geological exploration, can solve the problems such as not very reliable, increased formation compression and shear wave velocity, etc., to achieve the effect of improving exploration accuracy, improving reliability and saving drilling costs
CN101644781BActive Publication Date: 2011-08-17刘学伟 +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
刘学伟
Publication Date
2011-08-17

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Abstract

The present invention discloses a method for identifying natural gas hydrate (NGH) by using the incremental ratio between the wave impedance of longitudinal and traverse waves. The method comprises the following steps: (1) inverting the longitudinal wave impedance ZP=VP rho of strata and the transverse wave impedance ZS=VS rho of strata by using seismic data; (2) obtaining the longitudinal wave impedance ZP0 and the transverse wave impedance ZS0 of water-saturated strata; (3) obtaining the longitudinal wave impedance increments delta ZP=ZP-ZP0 and the transverse wave impedance increments delta ZS= ZS-ZS0; (4) obtaining the incremental ratio Ratio of the wave impedance of longitudinal and traverse waves; (5) inverting the porosity of strata; (6) determining the threshold value of the incremental ratio of the wave impedance of longitudinal and traverse waves according to the porosity; (7) judging whether the incremental ratio Ratio of the wave impedance of longitudinal and traverse waves is higher than the threshold value, if so, indicating that the strata contain the NGH; and (8) drawing the bisect where the incremental ratio of the wave impedance of longitudinal and traverse waves is higher than that of the threshold value, wherein the bisect can reflect the distribution range of underground NGH. The method of the invention improves the reliability of the identification results of NGH, greatly improves the exploration precision of NGH and reduces the dry-well rate.
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Description

technical field

[0001] The invention belongs to the field of geological exploration, and discloses a method for identifying natural gas hydrates by utilizing the ratio of compressional and transverse wave impedance increments. Background technique

[0002] Natural gas hydrate is an alternative energy source for oil and coal, and has attracted much attention from governments and academia, as well as industry. Gas hydrates mainly occur in the deep seabed and below the permafrost. Hydrate is a white solid substance produced by the chemical reaction of methane gas and water under low temperature and high pressure conditions. Hydrate occurs in the sandstone pore space. The main technologies for detecting hydrates are: seismic exploration technology, drilling technology, geochemical detection technology, seabed camera and sampling technology. Among them, seismic exploration is the most effective technique for detecting hydrates. At present, seismic exploration technology mainl...

Claims

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