黔东三都-丹寨地区寒武系斜坡相碳酸盐岩的储集性

贵州省东部三都、丹寨地区中上寒武统富藻碳酸盐岩是典型的斜坡沉积, 其在沉积后漫长的地质历史时期内，经受了诸多成岩环境的改造，发生了极大的成岩变化，最大的成岩变化为咸水云化，其他的成岩作用有压实作用、重结晶作用、压溶作用、有机溶解作用、埋藏云化作用、胶结作用及硅化作用等。成岩作用不仅使岩石（或沉积物）的矿物成分、结构组分、构造等发生程度不同的变化，更重要的是使原岩的储集性能发生很大的变化，即对原生孔隙或堵塞、或残留、或扩大，而且还可产生一系列的成岩孔缝（次生孔缝），这些次生孔、缝对岩石储集性的良化，尤其是对碳酸盐岩是至关重要的。由于斜坡沉积埋藏速度快，较快进入埋藏成岩环境，所以深溶作用（有机溶解作用）是该地区最主要的成孔成岩作用，所不同的是：丹寨剖面该种作用较强，而且孔内大部分灌入沥青，充分说明其是聚集期孔隙；而三都剖面这种孔隙相对较少。总之，这些富藻的斜坡相碳酸盐岩经过埋藏溶解作用而形成与沥青伴生的各种溶孔，从而使岩层具有较好的含油气性。

Reservoir Capacity of Cambrian Carbonate of Foreslope Facies in Danzhai and Sandu, Eastern Guizhou

Algae-rich carbonate of Cambrian is typical sediment of foreslope facies in Sandu and Danzhai, eastern Guizhou province. After sediment, it experiences many changes of diagenetic environment, and takes place much diagenetic altercation, among which the biggest is salt water dolomilization, and then is compaction, recrystallization, pressure solution, organic dissolution, burial dolomilization, cementation and silicification. Diagenesis not only can change mineral composition, fabric component, and texture, etc., but more important it can change the reservoir capability greatly, that is, it can build up, or reduce, or enlarge original pores, and even form a series of diagenetic crack. Those secondary pores and cracks are important to improve reservoir capability, especially for carbonate.Deep dissolution is the important diagenesis for forming pores because of its fast buried rate and good preservation of organic matter. The difference is that deep dissolution is strong and fills large amount of bitumen in the section of Danzhai, which shows they are pores when the oil and gas assembled; but pores are comparatively less in the section of Sandu.To sum up, the algae-rich carbonate of foreslope facies can form all kinds of bitumen -associated dissolved pores after experiencing burial dissolution, so it can have good capability of bearing oil and gas.