含油气盆地深层与中浅层油气成藏条件和特征差异性比较

含油气盆地埋深超过4 500 m的地层领域称之为深层。全球范围内,已在深层和超深层(>6 000 m)发现油气藏1 477个,油气储量分别占总储量的40% 和49%,目前中国塔里木盆地深层每年发现的油气储量约占总发现储量的90% 以上。随着世界对油气资源需求量增大,深层油气勘探的速度正在加快,挑战也在不断增多,研究深层油气成藏条件、油气藏地质特征和分布特征与中浅层油气藏的差异对于揭示和阐明深层油气成藏机制和分布规律具有重要现实意义。研究表明,深层油气成藏条件在生、储、盖、运、圈、保6个方面均与中浅层有较大差异,不能基于中浅层油气地质条件研究建立的标准和方法判别和评价深层油气地质条件和油气勘探前景;深层油气藏在圈闭类型、储层特征、流体相态、温压环境等方面也与中浅层油气藏存在较大差异,不能套用中浅层油气成藏模式与勘探经验指导深层油气藏预测与勘探;深层油气藏在不同类型盆地、不同年代地层和不同埋深条件下的分布发育具有自身特点,确定勘探方向和钻探目标不能完全套用中浅层已有的认识,需要结合实际地质条件具体考虑。

Comparison of otherness on hydrocarbon accumulation conditions and characteristics between deep and middle-shallow in petroliferous basins

Deep strata is defined as the stratigraphic field with buried depth greater than 4 500 m in hydrocarbon basins. All around the world, a total of 1 477 hydrocarbon reservoirs have been discovered in deep and ultra-deep strata (with buried depth greater than 6 000 m), of which hydrocarbon reserves account for 40% and 49% of the total respectively. At present, annual hydrocarbon reserves discovered in deep Tarim Basin, China account for more than 90% of the total discovery. With the increasing demand for oil and gas resources in the world, the deep hydrocarbon exploration is sped up, thus leading to more challenges. Therefore, the research on the differences in hydrocarbon accumulation conditions, geological and distribution characteristics of hydrocarbon reservoirs between deep and mid-shallow reservoirs has important practical significance to reveal and clarify the deep hydrocarbon accumulation mechanism and distribution laws. Research results have indicated that six great differences exist in deep hydrocarbon accumulation conditions involving source rocks, reservoir, cap rocks, migration, trap and preservation from mid-shallow strata. Thus, the criteria and methods established based on researches on the geological conditions of mid-shallow hydrocarbon cannot be used to judge and evaluate the geological conditions of deep hydrocarbon and its exploration prospect. Moreover, great differences also exist in trap type, reservoir characteristics, fluid phase state, temperature and pressure environment and other aspects between deep and mid-shallow hydrocarbon reservoirs. As a result, the mid-shallow hydrocarbon accumulation mode and exploration experience could not be applied to guide the prediction and exploration of deep hydrocarbon reservoirs. In addition, deep hydrocarbon reservoirs have their own characteristics of distribution and development in different types of basins, different ages of formation and different burial depth conditions. Thus, the existing understanding of mid-shallow reservoirs cannot be completely applied to determine exploration direction and drilling target, and it is required to make a decision based on the actual geological conditions.