碳酸盐岩酸化压裂CO2量的计算

Calculation of carbon dioxide volume in acid fracturing of carbonate rock

侯博恒 施松杉

西南石油大学油气藏地质及开发工程国家重点实验室，四川 成都 610500 中国石化江苏油田分公司试采一厂，江苏 扬州 225000

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China No. 1 Oil Production Testing Plant, Jiangsu Oilfield Company, SINOPEC, Yangzhou 225000, China

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7.37 MPa，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?鄄岩反应生成的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。

In the process of acid fracturing, acid will react with the rock while flowing along the fracture, as a result, a large amount of CO2 will be formed. Some of the CO2 will dissolve in the residual acid solution and some of the CO2 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 CO2， 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 CO2 generated from acid-rock reaction dissociated in the fracture 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.

10.6056/DKYT201305027