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海底天然气渗漏是海洋环境中广泛存在的自然现象,在世界各大洋中都有发现。海底渗漏的气体赋存于浅部地层,可以改变近表层沉积物的物理性质,使其在声学剖面上得以反映。通过对南海东北部陆坡浅地层剖面和地震反射剖面资料进行分析,在浅地层剖面上发现了声空白、声混浊、增强反射层、速度下拉等特征,在地震反射剖面上识别出气娴囱或泥底辟、亮点、速度下拉、增强反射层等特征。似海底反射层(BSR)作为地震剖面上明显的含气层标志,划分了两套含气层。通过浅地层剖面与地震剖面联合解释认为,BSR之下气烟囱/泥底辟的发育导致亮点、速度下拉、增强反射层等声学特征的发生,BSR之上水合物层的存在则可能起到封堵天然气而使其发生侧向运移的作用,气体封堵相对薄弱的位置天然气向上运移形成声空白、声混浊、增强反射层、速度下拉等特征。以声空白代表的天然气聚集带可能成为块状水合物的潜在赋存区。
Submarine natural gas leakage is a widespread natural phenomenon in the marine environment and is found in all oceans of the world. Seabed leaking gases, which occur in shallow formations, can alter the physical properties of near-surface sediments to reflect them in acoustic profiles. Based on the analysis of the data of shallow strata and seismic reflection profile in the continental slope of the northeastern South China Sea, the features of acoustic blankness, acoustic opacity, enhanced reflection layer and velocity pull-down are found in the shallow stratigraphic section, and gas chimney or mud is identified on the seismic reflection profile Diapirs, highlights, speed pull-down, enhanced reflection layer and other features. The Seabed Reflectors (BSR), as distinct gas-bearing markers on seismic profiles, have been divided into two sets of gas-bearing formations. Through the joint interpretation of shallow and seismic profiles, the development of gas chimneys / mud diapirs under BSR results in the occurrence of acoustic features such as bright spots, velocity pull-downs and enhanced reflection layers. The presence of hydrate layers above BSR may play a role in sealing Blocking the role of natural gas to make it happen lateral migration, gas sealing relatively weak position up the formation of natural gas sounder, acoustic opacity, enhanced reflection layer, the rate of pull-down and so on. Natural gas accumulation zones, represented by sonic blank, may be potential occurrences of massive hydrates.