【摘要】 麻坑作为海底冷泉流体活动的标志,普遍分布于莺歌海盆地中央坳陷区和莺东斜坡带。莺歌海盆地单个麻坑面积5×8—24×26m2,坑深一般在0.5—6.7m之间,形状为圆形或椭圆形,个别为长条状,最大的面积达300×580m2,坑深为117m。麻坑的形成与泥底辟多期次活动和气藏中天然气等流体的向上运移和喷发有关。麻坑发育区常伴有泥火山形成。地震剖面上有古麻坑(被掩埋的麻坑)的发育,表明历史时期曾发生过冷泉流体的喷发。在同一渗漏通道内由同一泥底辟形成的2次麻坑表明历史时期发生了2次间歇性的泥底辟上侵活动。依据莺歌海盆地麻坑深度,估计向上渗漏导致麻坑形成的深部气藏中的游离气层厚约16—94m。更多还原

【Abstract】 Pockmarks,as a sign of gas and fluid seepage on the seafloor,are widely distributed around the center depression and Yingdong Slope area of the Yinggehai Basin.The area of a single pockmark may range from 24×26 to 5×8 m2,its depth may be between 0.5 and 6.7 m,and its shape is approximately circular or elliptical,with a few of them being long strips.The largest one is 300×580 m2,and its depth is 117 m.The pockmark formation correlates with the multiple-stage activity of mud diapirs and the upward migration and eruption of free gases and fluids from the gas reservoir.The pockmarks are usually accompanied with the formation of mud volcano.Paleo-pockmarks(the buried pockmarks) have been discovered along seismic profiles,which indicates that the free gas and the fluid eruption took place in a historical period.The two times of pockmark activity in an identical seepage channel show that the upward intrusion of mud diapir took place intermittently.According to the depth of pockmarks,it is estimated that a 16-to 94-m-thick free gas layer upward venting in the deep gas reservoir is needed to form a 0.5-to 6.7-m-deep pockmark in the Yinggehai Basin.更多还原