渤海中部沙河街组深埋藏砂岩中优质储层成因

Characteristics and Genesis of Paleogene Deeply-Buried Sandstones Favorable Reservoirs in the Central Bohai Sea Area

渤海古近系湖相沙河街组砂岩储层埋深较深,主要为超过3000米以下的中深层,表现为扇三角洲沉积体系。主要岩石类型为岩屑长石砂岩和长石岩屑砂岩,长石含量较高约占40.39%,石英含量较低,仅占20.39%。成岩作用过程中,压实作用总体体现为较弱,而溶蚀作用占据主要位置。由于长石溶蚀的同时,自生矿物的形成尤其是粘土矿物和自生石英,再加上碳酸盐矿物的充填,导致孔隙度不断地减少。但总体来说,研究区砂岩物性较好,平均孔隙度20.8%,渗透率460.2 mD,能形成好的储层。另一方面,通过扫描电镜、电子显微镜、荧光分析等的观察,了解不同储层孔隙度和渗透率的特征,其目的是了解形成优质储层的原因。

The sandstone reservoir of the Paleogene Lacustrine Shahejie Formation in Bohai is deep in depth, mainly in the middle depth of more than 3000 meters, showing the fan delta depositional system. The main rock types are lithic feldspar sandstone and feldspar lithic sandstone. The high content of feldspar is about 40.39%, and the content of quartz is low, accounting for only 20.39%. In the process of diagenesis, the compaction is generally weak, while the dissolution occupies the main position. Because of the dissolution of feldspar, the formation of authigenic minerals, especially clay minerals and authigenic quartz, plus the filling of carbonate minerals, leads to the continuous decrease of porosity. In general, the sandstone property of the study area is good, and the average porosity is 20.8%, and the permeability is 460.2 mD, which can form good reservoir. On the other hand, through scanning electron microscopy, electron microscopy, fluorescence analysis and other observations, we can understand the characteristics of porosity and permeability of different reservoirs, so as to understand the reasons for forming high-quality reservoirs.