摘要:
西永2井中新世发育厚度较大的藻礁白云岩,以此为研究对象,通过岩心薄片、扫描电镜、X衍射分析及岩心CT扫描等研究手段,结合常规储层物性分析方法等,研究了西沙群岛中新世藻礁白云岩储层特征及成岩作用,结果表明:西永2井中新世藻礁白云岩储层发育良好,储集岩主要以粉晶—细晶白云岩为主,晶间溶孔、藻架孔、铸模孔、晶间孔和生物体腔孔为主要的储集空间,孔隙度变化较大,主要集中在8.39%~37.71%;渗透率为(0.17~3 291.9)×10-3 μm2,具有高孔、高渗显著特征。储层在成岩阶段经历了压实作用、胶结作用、白云岩化作用、重结晶作用及多期溶蚀作用。压实作用及胶结作用使得原生孔隙大幅减少,对储层形成具有破坏作用,白云岩化作用、重结晶作用和溶蚀作用改变孔隙结构,进而提高储层的有效孔隙度。研究表明西永2井中新世白云岩处冰期海退阶段,受大气淡水林滤作用影响,而多期溶蚀作用产生了大量的次生孔隙成为现今主要的储集空间。
关键词:
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白云岩
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储层
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成岩作用
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西永2井
Abstract:
A thick algal reef dolostone of Miocene was penetrated by the Well Xiyong-2. Routing work such as thin sections, scanning electron microscopy (sem), X-ray powder diffraction and Computed Tomography (CT) scan are conducted in combination with conventional reservoir property analysis for study of reservoir characteristics and diagenesis. The reservoir rocks are mainly composed of fine crystalline dolomite, and Intergranular dissolved pores, algae frame pores, moldic pores, intergranular pores and biological body cavity pores are observed as the main reservoir space. Porosity changes mainly within 8.39%~37.71%, while permeability changes within 0.17×10-3~3291.9×10-3μm2, and both are quite high. In the well, the types of disgenesis such as compaction, cementation, dolomitization, recrystallization and dissolution are observed. Compaction and cementation are the main factors to reduce the porosity after deposition. Dolomitization, recrystallization and dissolution are the factors to improve the porosity by changing the textures of pores. Research shows that Miocene dolomite in the well Xiyong-2 was formed in the glacial stage by leaching of atmospheric fresh water.
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