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本文对盖岩问题的地质方面进行了世界规模的调查研究,目的是为了在勘探冒险中评价封盖与保存的风险提供指南。最常见的盖岩是通常厚数十米到数百米的页岩和蒸发岩。区域性封盖层往往由蒸发的萨勃哈环境以及海侵、海退页岩构成的。为了适当地判定保存风险,必须把盖岩置于一个随时间演化的油气集聚的框架中。重要的参数是烃类通过盖岩的扩散速度以及作为地质力学变形强度函数的裂隙发育情况。当封盖失效和出现扩散而使烃类损失时,一个活跃的生烃—运移系统提供的烃类补给可以补偿这一损失。大油田和大气田可作为估计页岩/蒸发岩比以及封盖层深度的标准。地表油气苗则可提供封闭条件失效的程度。由于盖岩问题尚处于研究初期,许多不肯定因素影响了有关封盖和保存风险半定量论述的可靠性。
This paper examines the geological aspects of the cap rock issue on a worldwide scale with the aim of providing guidance on how to evaluate the risk of cap closure and preservation in exploration ventures. The most common cap rocks are shales and evaporites, usually tens to hundreds of meters thick. Regional capstorms often consist of evaporated Saboha environment and transgressive, descending shales. In order to properly determine the risk of preservation, it is necessary to place the cap rocks in a framework of hydrocarbon accumulation that evolved over time. Important parameters are the hydrocarbon diffusion rate through the cap rock and the fracture development as a function of geomechanical deformation strength. Hydrocarbon recharge provided by an active hydrocarbon-migration system can compensate for this loss when the cap fails and diffusion occurs causing hydrocarbon losses. Large fields and gas fields can be used as a yardstick for estimating shale / evaporite ratios and capping depth. Surface oil and gas seedlings can provide the level of closure failure. Since the problem of cap rock is still in its infancy, many uncertainties affect the reliability of semi-quantitative expositions of capping and conservation risks.