潜江凹陷盐湖沉积砂体的预测与研究

潜江凹陷潜江组的岩性主要有砂岩,盐岩和泥岩,岩性复杂难以区分,砂层薄,纵横向变化大,而且渗透性砂岩的波阻抗与盐岩的波阻抗大体相当,储层与非储层波阻抗差异小,在砂体预测上存在困难,但是经细致分析研究后仍发现砂岩、盐岩和泥岩的波阻抗值的有细微差别。从潜江凹陷储层的岩石物理特性出发,采用岩性识别技术、地震储层预测,地质与地震相结合,对潜江凹陷潜江组砂体进行预测研究,明确潜江凹陷潜江组以湖水相对淡化期的滨、浅湖相形成的砂坝及水下分流河道砂坝为主要储层,砂坝由中心向侧缘逐渐减薄为滩砂、席状砂等。潜江凹陷潜江组砂体分布广,多呈朵状展布。沉积相带和构造背景控制了砂体的类型和规模,地震反演方法是预测砂体展布的有效方法。

Forecast and Research of Deposit Sandbody of Salt Lake in Qianjiang Depression

Qianjiang formation in Qianjiang depression consists of sandstone, salt rock and mudstone whose properties are complex. In the formation, sand layer is thin and changes a lot; permeable sandstone almost has the same wave impedance as salt rock and the difference between reservoir and non reservoir is small. All this make sandbody forecast difficult. Starting with reservoir rock physical properties in Qianjiang depression and on the basis of lithology identification technique and seismic reservoir prediction, the author carries out prediction research on Qianjiang forma- sandbody. The research proves that in the formation the reservoir consists mainly of the sand bank of lakeshore -shallow lake phase which formed in the period of relative desalination of lake water and that of underwater distributary channel; the sand bank gets thinner from the center to lateral margin and then becomes beach sandstones and sill-like .sandstones. Qianjiang formation has the widespread sand bodies which distribute mostly in the shape of sand lobe. Seismic inversion is an effective way of forecasting sandbody spread when its type and size are controlled by sedimentary facies belt and structural setting.