川西坳陷侏罗系隐蔽河道精细刻画技术及应用

Fine characterization technique of concealed channel and its application in the Jurassic Formation of western Sichuan Depression

川西坳陷ZJ、XC、SF等气田的侏罗系气藏陆相砂岩储层致密,主要发育于三角洲平原—前缘分流河道中。物性相对较差的(3)类储层与围岩波阻抗叠置严重,往往形成中弱反射特征,地球物理特征隐蔽,精细刻画隐蔽河道分布是重要攻关方向。开展储层岩石物理特征分析及AVO(振幅随偏移距变化特征)道集正演,明确了不同类型储层与AVO类型之间的关系,确立了FN(远或近偏移距)叠加方法,在道集优化处理基础上,优选远或近道优势偏移距叠加,隐蔽河道识别能力明显提升。利用体分频像素成像技术开展隐蔽河道精细刻画,河道成像效果明显改善。技术应用准确落实了隐蔽河道分布,精细刻画出河道的外形及边界,发现多条新河道,并被实钻所证实,拓展了新的勘探开发阵地。

The sandstone reservoirs in the Jurassic formation of gas fields such as ZJ,XC,and SF in western Sichuan Depression are characterized by their tight nature and are primarily situated within delta plain-frontal distributary channels.These reservoirs often pose a unique challenge in terms of geophysical analysis due to the significant impedance contrast between the type③reservoir and the surrounding rock formations.Therefore,the precise characterization of concealed channel distribution is a crucial focus for expanding exploration and development efforts.In this study,the rock physics characteristics of reservoirs and forward modeling of AVO(Amplitude Versus Offset)gathers were conducted to determine the relationship between different reservoir types and AVO responses.Furthermore,a method known as the FN stacking method was developed.By optimizing the processing of gathers and selecting far/near offset stacking,the identification capability of concealed channels was significantly enhanced.This technology accurately reveals the distribution of hidden channels,precisely traces their shape and boundaries,and has successfully discovered new channels that have been confirmed through actual drilling,thus expanding new exploration and development fronts.