CO2驱油中岩石物性的变化规律

CHANGE LAWS OF ROCK PHYSICAL PROPERTIES IN CO2 OIL FLOODING

为了提高低渗透油田采收率，在扶杨油层地质条件下，通过室内实验，研究了注CO2后岩石性质变化规律。结果表明：随着岩石与CO2接触时间增加，岩石渗透率增加、孔隙度增加，平均孔隙半径减小，但岩石中小孔隙和大孔隙体积均增加，小孔隙体积比大孔隙增加得更多。变化原因是由于CO2与水形成碳酸，碳酸分解成H^＋和HCO2^-后，溶解岩石中长石、方解石、硬石膏等矿物，从而改变岩石孔隙结构。

In the conditions of Fuyang oil reservoirs＇geologies, in order to enhance the recovery of low-permeability oilfield; the change laws of the rock properties after CO2 injection are studied with the help of laboratory experiments. The results show that the permeability and porosity increase with the contact time between the rocks and CO2, but the average pore-radius decreases; on the contrary, the volumes of various pores enlarge, and moreover the volume of fine pore increases more than that of macro-pore. The reason of the above is due to the carbonic acid produced by the change between CO2 and water, and then the acid decompose into H^＋ and HCO3^-. The minerals in rocks such as feldspar, calcite, anhydrite and so on are dissolved, so the rock pore structures are changed.