测井资料评价次生孔隙的方法、原理及实例

结合高邮凹陷地区实际地质情况,在地质、地震及岩芯分析的基础上,对次生孔隙的成因机制从测井角度进行了分析讨论。主要从以下几方面研究1)利用整个井段的声波测井资料可以识别成岩阶段,划分次生孔隙发育的起始层段;2)分析利用声波孔隙度与密度、中子孔隙度差值求取次生孔隙度的适用条件和范围,依条件的不同进行方法的选取;3)利用声波-电阻率幅度差法量化烃源岩中有机质含量,分析有机质经过热解后产生的有机酸对砂体产生的溶蚀作用,判断由此导致的次生孔隙发育请况;4)利用声波时差辨识异常高压层段,分析次生孔隙的发育和保存。以上方法经过实例验证,效果明显。     

Changes in bark properties and hydrology following prescribed fire in Pinus taeda and Quercus montana

In the eastern United States, the use of prescribed fire as a silvicultural technique to manage for desirable upland tree species is increasing in popularity. Bark physical properties such as thickness, density, and porosity have known associations with fire tolerance among species. These physical properties simultaneously influence rainfall interception and canopy storage and thus are of interest across a range of disciplines. Furthermore, while these characteristics are innate to a species, it is unknown whether repeated exposure to fire facilitates physical change in bark structure and whether these changes are consistent among species. To answer these questions, bark samples were collected from mature pine (Pinus taeda L.) and oak (Quercus montana Willd.) trees from sites across the Bankhead National Forest in Alabama, USA under three different burn regimes: 3-year cycle, 9-year cycle, and no fire. Samples were analysed in the laboratory for bulk density, porosity, water storage capacity, and hygroscopicity (the amount of atmospheric water vapour absorbed by bark during non-rainfall conditions). Drying rates of saturated samples under simulated wetting conditions were also assessed. Oak bark had higher bulk density, lower porosity, and dried slower than pine bark. Interestingly, bark from both species had lower bulk density, higher porosity, greater water storage capacity, and dried faster in stands that were burned every 3 years compared to other fire regimes (p < 0.001). In summary, this study demonstrates that prescribed fire regimes in an eastern US forest alter bark structure and thus influence individual tree control on hydrological processes. The increase in bark water storage capacity, coupled with faster bark evaporation times may lead to less water inputs to the forest floor and drier overall conditions. Further investigation of this fire-bark-water feedback loop is necessary to understand the extent of these mechanisms controlling landscape-scale conditions.     

南加蓬次盆L气田盐胶结储层特征分析与识别

西非深水盐下储层是近年来油气勘探的热点,L气田位于南加蓬次盆深水区,储层呈低渗特征,盐胶结作用是储层物性变差的主要原因。由于盐岩密度较低（2.1 g/cm3）,存在盐胶结现象,可造成密度曲线值降低,给孔隙度计算带来偏差。识别储层是否存在盐胶结是该类储层评价的关键,分析发现元素俘获测井可以有效指示盐胶结的存在;在无元素俘获测井时,利用常规测井与核磁测井建立盐胶结识别因子曲线也能定性识别盐胶结的存在。在盐胶结层段声波测井可较准确地计算孔隙度,为下一步测井解释评价奠定了基础。