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莺歌海盆地是南海北部被动大陆边缘上的一个新生代沉积盆地,是一个年轻的、快速沉降的、沉积深厚的海相第三纪盆地,具有异常高温、高压,泥底辟构造非常发育.本文用改进了的趋势线法,利用地震速度谱资料计算地层压力,绘制了全盆地的超压顶面等深度图及各层压力系数变化图.经作图发现,莺歌海盆地的异常超压体系,象一个漂浮在盆地中的高温高压包,盆地中间埋藏浅而厚,盆地边缘加深变薄以至消失.此外,还发现了古超压面,它与现今的超压面是不一致的.并认为古、今超压面之间是古温度和古压力的能量释放带,现在找到的气田都在这个能量释放带范围内,属于超压体系以上的成油体系.这个成油体系以与泥底辟构造相伴生的高温高压包为烃源岩,由于水热增压和新生流体增压,高压包的压力是不断变化的,当压力增高至冲破上覆地层时,烃类呈幕式从高压包中释放出来,并以水相运移为主,由高势向周围低势区运移.能量释放带从纵向上接受高压包中通过泥底辟和“气烟筒”向上运移的油气.横向上,高压包中的油气沿大断层及不整合面向能量释放带中运移,即向盆地边缘断裂构造带及大三角洲砂岩体内运移、聚集.所以,找准能量释放带中的各类圈闭是油气勘探的关键.
Yinggehai Basin is a Cenozoic sedimentary basin on the passive continental margin of the northern South China Sea. It is a young, rapidly subsided, deep-sedimentary marine Tertiary basin. It has abnormally high temperature, high pressure and extremely strong mud diapirism. In this paper, the improved trend line method is used to calculate the formation pressure by using the seismic velocity spectrum data, and the contour map of the overpressure top surface and the pressure coefficient of each layer are plotted in the whole basin.The abnormal overpressure in Yinggehai Basin The system, like a high-temperature and high-pressure pack floating in a basin, is shallow and thick buried in the middle of the basin and deepens and even disappears on the edge of the basin. In addition, paleo-overpressures have been found that are inconsistent with today’s overpressures It is considered that the Paleozoic and overpressured surface is the energy release zone between Paleo-temperature and Paleo-pressure, and the gas fields now found are all within the range of this energy release zone and belong to the oil-forming system above the overpressure system. The high-temperature and high-pressured karst accompanying the diapir structure is the source rock. Due to hydrothermal pressurization and new fluid pressurization, the pressure of the high-pressured pack is constantly changing. When the pressure increases to break through the overburden, high pressure And released mainly by the water phase and migrated from the high potential to the surrounding low potential region.The energy release zone was longitudinally receptive to the uplift of oil and gas in the HPT by mud diapirs and “gas chimney”. Laterally, the oil and gas in the HPT migrate along the fault and unconformity towards the energy release zone, that is, migrate to the marginal fault structure zone and the deltaic sandstone body, so as to identify the various types of energy release zone Traps are the key to oil and gas exploration.