湖相沉积背景下低渗透率断块油藏的综合评价

Formation Evaluation of Low Permeable and Intricate Fault Block Reservoir

柴达木盆地W油田沉积背景和构造变化导致岩性复杂,断裂带发育和断块的封闭性差异造成水性改变;泥晶颗粒、方解石结晶颗粒的存在导致了微孔隙度的发育。测井解释难点主要在挤压带高电阻率水层和油层的区分、断裂带地层水淡化区域油水层电阻率混淆,以及微孔隙发育导致低产层和干层界定困难。以复杂岩性储集层评价为基础,结合油藏构造特征、储层地质特征,分析异常挤压带下测井资料响应特征并针对性开展解释;通过分析断块水性特征变化规律,提出了低渗透率储集层微孔隙度发育层段的测井识别手段,确定评价方法和评价标准。确立了分水性特征、挤压特征相应的测井解释方法,有效划分低产储层。

Special depositional settings and variable geologic structures in W oilfield in Caidam basin lead to complex lithologies;Developed fracture belts and different closures of fault blocks result in changes of formation water;Micrite grains and crystalline calcite particles cause development of micro-porosity.For log interpretation it is hard to distinguish water zone and oil zone with higher resistivity in compressional belts;to get resistivities of the oil/water in the desalination formation water region in the fault zones since the resistivities are confusable or fuzzy;and to determine the lower production bed and dry bed because of micropore development.Based on complex lithology reservoir eveluations and combined with reservoir structure and geology characteristics,analyzed are log responses in the abnormal compressional belts,and hense the purposeful or corresponding log interpretations are made.Through analyzing changes of water in the fault blocks,proposed are log interpretation and evaluation methods and criteria for the developed micro-porosity bed in the lower permeable reservoir.Given are log interpretation methods for formation water salinity changes and compressional feature changes,and the low production reservoir is determined effectively.