海底天然气水合物资源量计算及环境效应评估  

CALCULATION OF POTENTIAL VOLUME OF GAS HYDRATE AND ITS ENVIRONMENTAL EFFECTS

作　　者：葛倩[1] 王家生[1] 向华[1] 甘华阳[1] 胡高伟[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074

出　　处：《海洋地质与第四纪地质》2004年第4期127-133,共7页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金资助项目 ( 4 0 2 72 0 5 2 ) ;教育部地质学理科"基地班"基金 ;国家自然科学重点基金资助项目 ( 4 0 2 3 2 0 2 5 ) ;教育部回国人员科研启动基金 ;国家海洋局海底科学重点实验室开放基金 ( 2 0 0 2 3 )

摘　　要：计算天然气水合物的资源量是比较复杂的 ,利用垂直大陆边缘横断面面积来计算水合物资源量的方法 ,能较好地反映外界条件变化所导致的水合物资源量在时间上的变化趋势。呈透镜状的水合物横断面面积主要与以下 6个参数有关 :水的活度、大陆坡深度、大陆架转折端的深度、大陆坡坡度、底部水温以及地热梯度。其中 ,前 3个参数中任何一个减小或者后 3个参数中任何一个增大都会导致横断面面积的减小。运用VisualBasic 6 0编程 ,以布莱克海岭地质背景为例 ,根据横断面面积、充填率和孔隙度计算全球海底水合物资源量约为 3 97× 10 5km3 ,与其他学者的计算结果相当。进而推算出LPTM约有 0 38× 10 5km3 的水合物被溶解并释放到海洋和大气圈中 ,导致当时沉积的碳酸盐岩和有机物的平均δ13 C下降 - 2 5‰的重大地质事件。这种水合物资源量计算方法 ,对分析地史时期类似重大转折时期评估天然气水合物对全球环境的影响 。To calculate the potential volume of oceanic gas hydrate is relatively a complex job. Here, we give a method by calculating the lens-shaped area perpendicular to a given continental margin to calculate the potential volume of gas hydrate, which could most likely reflect the variations of potential volume whenever the external conditions change in the time domain. The lens-shaped area varies mainly with the following six basic parameters: water activity (a_(w)), slope depth (Z_(slb)), sea level relative to the shelf break (z_(0)), slope gradient (Z), bottom water temperature (T_(b)) and geothermal gradient (G). The potential area would decrease with decreasing of a_(w), Z_(slb), z_(0) and increasing of Z, T_(b), and G. According to study results from the area, amount of gas hydrate in pore space and porosity in Blake Ridge, a Visual Basic 6.0 program here is proposed to calculate the potential volume of gas hydrate in the world to be about 3.97×10^(5) km^3 totally, which is agreeable with calculations using other methods. Moreover, it was inferred that about (0.38)×10^(5) of km^3 gas hydrate at LPTM (Latest Paleocene Thermal Maximum) was dissolved and released into the ocean or atmosphere, which could have most probably resulted in the sharp δ^(13)C excursion by -2.5‰ in carbonate globally. So, it is reasonably believed that the proposed method would be much helpful to evaluate the geological environment effect in the history of earth.

关 键 词：天然气水合物 海底 资源量计算 海岭 地质事件 大陆边缘 大气圈 面积 重大 垂直 

分 类 号：P618[天文地球—矿床学] G633[天文地球—地质学]