地下孔隙率和渗透率在空间和时间上的变化及影响因素

Spatio-temporal Variation of Subsurface Porosity and Permeability and Its Influential Factors

地下岩石孔隙率和渗透率在空间和时间上的变化受众多因素控制 ,总的说来 ,包括沉积与成岩两个最为主要的因素。沉积盆地的性质和沉积环境控制了沉积物的组成、岩石的结构和原生孔隙。沉积作用所经历的时间相对较短而进程较快 ;成岩作用所经历的时间相对较长而进程较慢。从对孔隙率和渗透率的控制作用来说 ,成岩作用的研究难度相对较大。近年来 ,一些传统的形成地下岩石次生孔隙的机制受到挑战 ,这些传统机制中最为主要的是有机酸对铝硅酸溶解形成次生孔隙 ,但这会造成介质pH值的升高 ,碳酸盐矿物和高岭石的沉淀。地下岩石中碳酸水溶解产生的次生孔隙也是有限的。新的机制如大气淡水的溶解作用 ,深部冷却地下水的溶解作用 ,硅酸盐的水解都得到了人们的普遍接受 ,这对于次生孔隙成因的解释及地下岩石孔隙率和渗透率的预测十分重要。对于碳酸盐岩来说 ,与不整合面附近的古喀斯特有关的油气藏得到了更多的关注。深埋藏过程中碳酸盐岩成岩作用的研究中 。

Spatio temporal variation of subsurface porosity and permeability is controlled by various factors during sedimentation and diagenesis. The depositional environments and the types of sediment basin control the original composition before burial, texture and porosity of sediments. The sedimentary factors to control the porosity and permeability are mainly sedimentary facies,stratigraphy sequences and so on.The process of sedimentation was much shorter than the diagenesis, and relatively easy to study. Recently, some traditional mechanism of secondary porosity formation for subsurface sediment is challenged by new theories. The formation of secondary porosity from the aluminium silicate solution by organic acid is the most important mechanism. However, it will result in the increase of pH value, precipitation of carbonate and kaolinite. The dissolution by carbonic water to form the secondary porosity in subsurface is also limited. New mechanism such as dissolution of sediment by the meteoric water, by the deep cooling formation water proves effective, and hydrolysis of the silicates is also accepted universally. In addition, the precipitation and material sources of some diagenetic authigenic minerals related to the secondary porosity also have new mode. These are several essentials to understand the formation of secondary porosity and estimate the porosity and the permeability of the reservoir. For the carbonate rocks, the oil/gas reservoir related to the paleo carst nearby the unconformity have got more attention. During the deep burial diagenesis, the temperature and pressure control the difference of the habit of dissolution and precipitation for different carbonate minerals, leading to the difference of porosity and permeability distribution in subsurface carbonate rocks, which is very important for prediction of carbonate reservoir.