通过表面溶蚀和内部溶蚀两种实验方式,分别对六种类型碳酸盐岩用0.2,乙酸溶液进行溶蚀实验,对比研究了从表生环境到深埋藏环境下有机酸与不同类型碳酸盐岩的溶蚀作用机制.对比研究表明:(1)在近地表环境下(25℃,1.0MPa),泥灰岩和合生物碎屑泥晶灰岩的溶解速率大于细晶白云岩,前两者约为后者的2～3倍;随着温压的增加,泥灰岩、含生物碎屑泥晶灰岩和细晶白云岩的溶解速率均相应增加,但细晶白云岩的溶解速率增加幅度更大;在深埋藏环境下(180℃,45 MPa到210℃,52.5 MPa),细晶白云岩的溶解速率逐渐与泥灰岩和含生物碎屑泥晶灰岩的溶解速率趋于一致.(2)在60℃,10 MPa时,白云质颗粒灰岩在乙酸溶液中的溶解能力大干粉细晶白云岩和亮晶鲕粒白云岩;随着温压的增加,有机酸溶液对石灰岩与白云岩的溶解能力均相应降低,且石灰岩溶蚀作用下降幅度更大,当温压达到或超过90℃、20 MPa时,粉细晶白云岩和亮晶鲕粒白云岩在乙酸溶液中的溶解能力大于白云质颗粒灰岩.根据实验结果推测:表生和相对浅埋藏的温压条件下,石灰岩的溶解速率和溶解能力大于白云岩,石灰岩的溶蚀作用较白云岩发育;但在深埋藏阶段,由于白云岩的溶解能力大干石灰岩,因此白云岩溶蚀产生的次生孔隙较石灰岩更为发育,这或许是深部的碳酸盐岩储层中多见白云岩储层的重要原因.

In order to study the mechanism of carbonate rocks dissolution in organic acid under the conditions from epigenesist to deep burial digenesis environment, the reactions of acetic acid (initial 0.2,) with six types of carbonate rocks were investigated using two experimental ways of surface dissolution and internal dissolution. The result of surface dissolution indicates that dissolution rates of carbonate rocks increase with increasing the temperature and pressure. In the conditions from epigenesis to middle burial digenesis environment, the dissolution rates of marl and bioclastic wackestone are twice or three times than that of fine crystalline dolostone. In the condition of deep burial environment, the dissolution rates of bioclastic wackestone, marl, and fine crystalline dolostone are basically the same. The result of internal dissolution shows that the dissolving capacity of dolomitic grainstone in acetic acid is greater than that of microcrystalline to fine crystalline dolostone and sparry oolitic dolostone in the conditions at 60 ℃ and 10MPa. The dissolving capacity of dolomitic grainstone, microcrystalline to fine crystalline dolostone and sparry oolitic dolostone increases with increasing temperature and pressure in acetic acid. When the temperature and pressure reach to or exceed 90 ℃ and 20 MPa, the dissolving capacity in acetic acid of microcrystalline to fine crystalline dolostone and sparry oolitic dolostone is greater than that of dolomitic grainstone. Based on the results of experiments, it can be predicated that the dissolution rate and solubility of limestone in organic acid is greater than that of dolostone under the conditions of epigenesist and relatively shallow burial environment, so that the dissolution capacity of limestone must be greater than that of dolostone. Under the deep burial condition, dolostone has greater dissolution capacity and the similar dissolution rate with limestone. This maybe is one of the most important reasons why dolomite reservoirs with secondary porosity are more than limestone reservoirs in relatively deep strata.