塔中82井区层间岩溶成因探讨

RESEARCH ON INTERLAYER KARSTIFICATION PATTERN IN WELL TZ82 REGION

在对塔中82井区颗粒灰岩段进行储层预测研究过程中发现:颗粒灰岩段与上覆泥质条带段之间的层面存在波形异常,这种波形异常区与叠前地震预测的AVO属性异常区非常吻合。首先基于碳～氧同位素研究结果,推测塔中82井区的成岩作用属于海水成岩及埋藏成岩作用;其次在地层水资料分析基础上,认为在泥质条带段中,丰富的有机质在热演化过程中形成有机质的CO2及有机酸,导致地层水为弱酸～弱碱性。酸性地层水在埋藏成岩作用下,对颗粒灰岩段顶面进行溶蚀作用,导致塔中82井区颗粒灰岩段顶面岩溶顺层分布,可能是该区一种新的储层成因类型,这种新的储层类型在岩芯及薄片观察均可得到相应证明。颗粒灰岩段顶面的层间岩溶模式研究,因其储盖配置关系优越,分布面积广的优势弥补了厚度薄的不足,可以扩大塔中82井区勘探成果。

Reservoir prediction research in grain limestone shows that there are seismic waveform anomaly between grain limestone and overlaying shale strip. The results of Carbon-oxygen isotopic analysis indicate that reservoir in well Tz82 region is under seawater and buried diagenesis condition. In the process of thermal evolution,a great deal of organic matter in shale strip developed into organic matter carbon dioxide and organic acid which resulted in weak acid and alkalescence formation water based on the analysis of formation water data, and acid formation water dissolved the top of grain-stone because of buried diagenesis, which resulted in the layer distribution of karstification in the top of grain limestone in well Tz82 region. This is possibly a new type of reservoir and this type of reservoir can be confirmed by core and rock thin-section analysis. This interlayer karstification pattern on top of grain limestone will bring the new exploration results of well Tz82 region because its wide distribution and the good association of reservoir and sealing though the thickness is thin.