珠江口盆地白云凹陷中新统珠江组深水灰岩沉积-成岩作用特征

Deposition and diagenesis of the Miocene deep-water limestones of Zhujiang Formation in Baiyun sag,Pearl River Mouth Basin

深水灰岩中可产有大量油气。珠江口盆地白云凹陷珠江组深水灰岩是深水牵引流（内波、内潮汐等）沉积的非重力流碳酸盐岩，深水灰岩及深水牵引流的研究具有重要地质意义。据钻井岩心观察和铸体薄片、扫描电镜、X衍射等分析，详细研究了珠江组深水灰岩的成岩作用特征。珠江组深水灰岩埋藏成岩作用期间经历的所有明显变化都是破坏性的过程，原生孔隙缩减的主要原因为机械压实、压溶作用和自生矿物充填及胶结作用。珠江组深水灰岩现今埋深2920～3220111，但仅经历了相当于1～1．5km埋深的机械压实、压溶作用，与较早进入超压旋回有关，且后期缺乏构造破裂，最终成为中一高孔、低特低渗孔隙型潜在储层。

The deep-water limestones can yield a large amount of oil and gas. The deep-water limestones of Zhujiang Formation were deposited by deep-water tractive currents （such as internal waves and internal tides） and the researches on the deep-water limestones and tractive currents are of great geological significance. On the basis of investigations on drill cores and impregnated thin section studies, by using the scanning electron microscopy and Xray diffraction, a detailed study of the diagenesis of the deep-water limestones of Zhujiang Formation was conducted. It is suggested that all the significant diagenetic changes that occluded the pores were destructive. The mechanical compaction, pressure solution, filling and cementation of secondary minerals during the burial processes were the major factors causing the loss of the primary porosity. Though the limestones were buried in the depth of 2920 - 3220 m, they had only undergone the mechanical compaction and pressure solution equal to about 1 - 1.5 krn during the burial processes because they got involved into overpressure cycles earlier and lacked later tectonic fracturing, and eventually the potential pore-dominated reservoirs with medium to high Porosity and low to very low permeability were developed.