碳酸盐岩酸化压裂CO2量的计算

酸化压裂过程中，酸液沿裂缝壁面岩石流动反应，生成大量CO2。这些CO2部分溶解在残酸溶液中，部分游离于裂缝内，气相物质的存在对酸液流动反应过程具有重要影响、CO2的临界温度为31．05℃，临界压力为7．37MPa，在储层条件下游离CO2一般处于超临界状态。根据质量守恒原理与相平衡原理，文中总结了酸化压裂过程中CO2生成量、溶解量以及超临界游离CO2体积的计算方法，并进行了实例分析。计算结果表明，酸一岩反应生成的CO2数量巨大，其中小部分溶解在残酸溶液中，绝大部分以超临界状态游离在裂缝中，需考虑其对酸液流动反应和裂缝延伸的影响。

Calculation of carbon dioxide volume in acid fracturing of carbonate rock

In the process of acid fracturing, acid will reaet with the rock while flowing along the fracture, as a result, a large amount of CO, will be formed. Some of the CO, will dissolve in the residual acid solution and some of the CO, will still dissociate in the fracture. The critical temperature of CO2 is 31.05 ℃ and the critical pressure of CO2 is 7.37 MPa. In generally, the free CO2, in the reservoir is always in the condition of supercritical state. According to the principle of mass conservation and phase equilibrium, this paper sums up the methods calculating the volume of the generated CO,, the dissolved CO2, and the free CO2 in the process of acidizing and fracturing, and anlyzes the examples. The calculating results show that most of the CO, generated from acid-rock reaction dissociated in the fiacture in the form of free gas which has significant influence on acid flow reaction, while only a little of the generated CO2 dissolved in the residual acid solution. The volume of the supercritical-state CO2 influences fracture extension and acid flow reaction.