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当假设地层为各向同性时,在砂、泥岩层序中具有的各向地震异性特征则会产生构造成像问题。在委内瑞拉东部的Santa Rosa气田共获得了三个高分辨率井间地震剖面,需要成像的目的层岩性为砂岩,厚度在5~50ft之间,其沉积背景是1800ft厚的三角洲,渐新世的河流相砂岩沉积与上覆的大套泥岩沉积呈不整合接触关系,大量的泥岩与砂岩交互沉积的结果导致岩性存在各向异性。原始的层析反演表明有很强的各向异性特征,这可以由井上的声波测井信息反映出来,纵、横向的速度差异在上覆泥岩沉积中可达16%~23%,而在下伏砂岩沉积中,纵、横向速度差异还不到5%。
When the formation is assumed to be isotropic, the anisotropy of anisotropy in the sand and mudstone sequences creates a tectonic imaging problem. Three high-resolution crosswell seismic profiles have been acquired in the Santa Rosa gas field in eastern Venezuela. The target lithography to be imaged is sandstone with a thickness of 5 to 50 ft and a sedimentary background of 1800 ft thick deltaic, Oligocene Of the fluvial sandstone deposits are in an unconformity contact with the overlying large set of mudstone deposits. The large amount of mudstone and sandstone interaction results in the anisotropy of lithology. The original tomographic inversion shows strong anisotropy, which can be reflected by the acoustic logging information in the well. The difference in vertical and horizontal velocities can reach 16% -23% in the overlying mudstone deposition. V sandstone deposition, vertical and horizontal velocity difference of less than 5%.