The Seismic Attribute Analysis For Gas Hydrates

The seabed is rich in natural gas hydrate which has great prospects for energydevelopment. Seismic exploration is an important means of the detection of gashydrates, many of the characteristics of the seismic data can be used to identify thesubmarine gas hydrates, especially plays an important role in identifying BottomSimulating Reflector (BSR). The seismic attribute is an important way to attainreservoir parameters which refers to the special measure on the geometry, kinematics,dynamics and statistical properties derived from seismic data. In recent years, seismicattribute plays an important role in reservoir description, seismic structureinterpretation. The main content of this paper is how the seismic attribute can beapplied to the identification of gas hydrates.Pre-stack seismic data contains a wealth of geological information, and thereforecan be used to extract seismic attribute profiles. The instantaneous attributes canprovide more concise and more intuitive earthquake information by decomposing thestacked seismic data and producing instantaneous amplitude, instantaneous frequencyand instantaneous phase profile. Intercept attribute and instantaneous amplitude issensitive to the BSR, fluid factor attribute and instantaneous frequency is sensitive tothe free gas, AVO angle gathers section can provide how amplitude change by offset.So we can take advantage of these properties to identify gas hydrate.In this paper, the marks of gas hydrates in seismic profile were summarized, andthen a forward model was designed for the study; The seismic data from the EastChina Sea was processed; The pre-stack seismic data for AVO was attained by trueamplitude recovery, velocity analysis, multiple removal techniques, and then thepossibility of the existence of the gas hydrate was estimated. Instantaneous attributeanalysis was used to the stack data, providing evidence for the presence of gas hydrate. Polarity information, speed information is also important in identifying of gas hydrate.In order to identify the BSR on the seismic section and analysis the presence of gashydrates, we should consider all the information of seismic data.Refraction can be used for identification of gas hydrates is the innovation of thispaper. A forward model was used to prove this view.However, multiples have a lot of similarities with the BSR, and can be easilymistaken for the BSR, then will draw the wrong conclusions based on these false BSR.So it is important to identify the true BSR from the false. In this paper, multiples andbubble effect are separated from BSR based on the seismic characteristics. Thereforeincreasing the accuracy of marine seismic exploration, and provide technical supportto find more gas hydrates.