页岩气楔状模型储层的地震响应特征

Seismic Response Characteristics of Shale Gas Wedge Model Reservoir

中国南方古生界页岩气储层分布面积广,碳质含量高,但是储层保存条件较差,受构造运动影响较大。为此设计了5种不同楔形模型研究其地震响应特征——地震子波主频对波场特征的影响;页岩体速度对波场特征的影响;页岩体顶、底界面坡度变化对波场特征的影响;地层夹角对波场特征的影响;顶底界面岩性组合对波场特征的影响。研究表明:地震子波主频增加,分辨能力提高;页岩体速度与围岩差异变大,反射同相轴振幅增强;楔状页岩体顶、底界面坡度变大,横向分辨率增大;对于梯变型页岩体,在厚度为四分之一波长处,相消干涉,反射能量最弱,振幅达到极小值。

The Paleozoic shale gas reservoirs in southern China cover a vast area. Their carbon content is high, but preserving condition rather poor because of tectonic movements. By this, different wedge models designed to study their seismic response characteristics, in- cluding impacts from wavelet dominant frequency, wave velocity in shale mass, gradient variation of shale mass top and bottom interfac- es, strata included angle and rock association at top and bottom interfaces to wave field features. The result has shown that wavelet dom- inant frequency increasing, resolution improving; velocity difference in shale mass and country rock increasing, amplitude of reflection phase axis strengthening; gradient of wedgy shale mass top and bottom interfaces increasing, transverse resolution improving; to wedgy shale mass, when thickness is one quarter wavelength, destructive interference, reflected energy weakest, amplitude minimum.