柴达木盆地西部古近纪—新近纪湖相生物礁的发现及意义

在柴达木盆地西部古近纪和新近纪地层中发育了典型的湖相生物礁,可以分为由基质支撑的叠层石礁、凝块礁和骨架支撑的藻礁3大类型,并对每种类型中亚类的特征和建造生物进行了简要介绍。生物礁孔隙度高、渗透性好,是优质储层。孔隙类型丰富多样,主要有骨架孔隙、体腔孔隙、粒内孔隙、溶孔等10种孔隙类型。生物礁的地震响应和测井曲线特征明显,在研究取心井段生物礁地球物理响应特征的基础上可以有效的识别和预测生物礁。综合应用古生物分析、孢粉分析、同位素分析、古地磁分析、地球化学分析和地球物理特征分析等技术手段,并结合生物礁发育的沉积条件和构造背景,初步探讨了生物礁对柴达木盆地古气候、古地理位置、古构造、古水介质、古沉积环境和青藏高原的隆升等方面的研究意义以及对油气勘探方面的意义。

DISCOVERY AND SIGN IFICANCE OF THE NEOGENE AND PALAEOGENE LACUSTRINE REEFS IN THE WESTERN QAIDAM BASIN

In the western Qaidam Basin, lacustrine reefs occur in the Neogene and Palaeogene strata.Three types of reefs are recognized: matrix-supported reefs (stromatolites), thrombolite reefs and skeleton-supported reefs (algal reefs). Their characteristics and reef-building organisms are described. The reefs have complex types of pores, such as skeletal pores, body cavity pores, intraparticle pores, corroded cavities, etc. These are excellent reservoir in the study area. The characteristics of seismic responsibility and logging trace of reefs are obvious, and reefs may be identified and predicted according to their geophysical characteristics of cores. Paleontologic, sporopollen, isotopes, palaeomagnetism, geochemistry and physical geography are synthetically applied to discuss the palaeoclimate, palaeolatitude, palaeotectonics, palaeohydrological conditions, palaeosedimentary environment of the Qaidam Basin and uplift of the Tibetan Plateau. The discovery of lacustrine reefs is of important economic significance for the exploration and development of the Qinghai Oilfield.