蒸发岩发育特征及其对大油气田形成的影响

摘要

Evaporite rocks are widely developed in petroliferous basins around the world and closely relate to the formation and distribu- tion of the global giant oil and gas fields. By study of the relative changes in sea level, the changes in climate condition and the evolution of various basins, the development characteristics of evaporite rocks are analyzed. That is, the formation and distribution of evaporite rocks are commonly controlled by the restricted topographic lows inner basins, the relatively stagnant water bodies and the hot arid climate. Through research of sealing ability, thermal conductivity and incompetence of the rocks, the effects of them on formation of giant oil-gas field are analyzed, integrated with the case studies of giant oil-gas fields in eastern Siberia, Campos and Zagros basins. It is suggested that tight evaporites can be as cap rocks that effectively seal the underlying hydrocarbons; the thermal conductivity can keep the temperature balance, being helpful to complete organic matters＇ transformation; the incompetence may cause it decollement and deformation, which al- lows the overlying reservoirs to have developed fracture systems, greatly improving the quality of reservoirs; the intense deformation could also form salt structures,＇shaping new traps for oil and gas. It is concluded that the development of evaporite rocks restricts or influences the formation and distribution of the global giant oil and gas fields in time and space, and with the deepening of the oil and gas exploration, the large and giant oil-gas fields related with the evaporites will inevitably become the targets for petroleum exploration in the future.%蒸发岩广泛发育于全球各含油气盆地之中，其发育分布特征与世界大油气田的形成和分布有着密切的关系。通过对全球气候条件、海平面相对变化以及各类型盆地进行研究，分析了蒸发岩的发育特征，盆地内部的限制性洼地、相对停滞的水体以及干旱炎热的气候等共同制约着蒸发岩的形成与分布。通过对蒸发岩封盖能力、热导率以及非能干性的研究，结合东西伯利亚、坎波斯以及扎格罗斯等盆地中大油气田实例，分析了蒸发岩层对大油气田形成的影响。蒸发岩的致密性作为盖层有效地封盖了下伏油气，其热导率又有利于保持温度均衡，使得有机质能够更为彻底地转化；蒸发岩的非能干性使其易于发生滑脱变形，导致上覆储集层裂缝系统发育，极大地改善了其储集性能；蒸发岩强烈变形还可以形成盐构造，为油气聚集形成新的圈闭；蒸发岩的发育在时间上和空间上都制约着全球大油气田的形成与分布。随着油气勘探的不断深入，将会发现越来越多的与蒸发岩有关的大油气田。