隐蔽油气藏研究的难点和前沿

The difficulties and frontiers of subtle oil/gas reservoir research

隐蔽油气藏已成为中国油气勘探的主要领域之一。随着勘探程度的提高,隐蔽油气藏勘探向复杂条件拓展,深层隐蔽油气藏发育与保存、不整合面结构与隐蔽油气藏分布、调整改造型隐蔽油气藏形成和保存机理成为隐蔽油气藏勘探和成藏机理研究的难点和前沿。深部存在活跃源岩和具有较高孔隙度和渗透率的储层是深层隐蔽油气藏成藏的基础。超压环境生烃作用动力学的研究进展提高了预测深层源岩生烃潜力的能力,已知的深层高孔隙度储层保存机理可成为预测深部储层孔渗条件的基础。不整合面结构特别是古土壤层的厚度及封闭能力、古土壤层之下半风化岩层的厚度及渗透率是研究与不整合面有关的隐蔽油气藏的关键。由于多期构造叠加、多期生烃和多期成藏,叠合盆地很多隐蔽油气藏经历了不同程度的调整改造,形成有成因联系的一系列调整改造型隐蔽油气藏,研究晚期构造与早期构造的叠加方式是预测调整改造型隐蔽油气藏的基础。准噶尔盆地中部,隐蔽油气藏同时具有埋藏深、不整合面结构复杂、多期成藏多期调整改造的特点,是建立复杂隐蔽油气藏成藏与勘探理论的天然实验室。

Subtle oil/gas reservoirs have become one of the main exploration targets in China. As petroleum exploration goes into a more mature stage, the search for subtle oil/gas reservoirs expands into areas with more complicated conditions. The accumulation and preservation of petroleum in deeply buried subtle traps, the structure of the unconformities in relation to subtle oil/gas reservoir distribution, the reasons for the loss of petroleum in the former subtle traps , and for the preservation of adjusted subtle oil/gas reservoirs have become the difficulties of petroleum exploration and the frontiers for scientific research. The existence of active source rocks and reservoir rocks with relatively high porosity and permeability in the deep part of basins is fundamental for petroleum accumulation in deeply buried subtle traps. Advances made in recent years on the kinetics of hydrocarbon generation in ovcrpressured environments will improve our ability to predict the maturity and hydrocarbon potential of deeply buried, overpressured source rocks. Several mechanisms causing abnormally high porosity in deeply buried sandstones may become the basis and principle for predrilling assessment of the quality of the reservoirs. The structure of unconformities, especially the thickness and the sealing ability of paleosoil layers, and the thickness and permeability of semi-weathered rocks below the palm-soil layers are keys to the study of subtle oil/gas reservoirs associated with unconformities. In superimposed basins, the formerly accumulated subtle reservoirs usually have undergone adjustments owing to the effects of multiple-stage tectonic movements. The adjustments of former subtle reservoirs could lead to the occurrence of a series of genetically related oil layers with complicated oil/water or gas/water contacts. The stacking pattern of different tectonic movements is very important for predicting adjusted subtle oil/gas reservoirs. In the center part of the Junggar Basin, for example, the subtle oil/gas reservoirs have all the above attributes： having been deeply buried; having complicated unconformities; and having undergone tectonic adjustments. Therefore, the central part of the Junggar Basin may become a ＂natural lab＂ for research on complicated subtle oil/gas reservoirs.