Du Juan, Guo Guixian, Liu Pingli, Xiong Gang, Chen Pengfei, Liu JinMing, Chen Xiang
State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China.
Research Institute of Natural Gas Technology, PetroChina Southwest Oil & Gasfield Company, Chengdu, Sichuan 610213, China.
ACS Omega. 2022 Mar 21;7(14):12066-12075. doi: 10.1021/acsomega.2c00259. eCollection 2022 Apr 12.
As an important part of the acid fracturing process of carbonate reservoir, the performance of acid fracturing working fluid directly affects the stimulation effect of oil wells. In this paper, formaldehyde (agent A) and ammonium chloride (agent B) were used as the matrix. Several aldehydes with different volume ratios were prepared. The acid ratio with the highest acid yield was selected by the sodium hydroxide titration experiment. The results show that when the volume ratio of agent A to agent B is 1:1.3, the acid production capacity is the strongest. The pH values at several time points in the process of acid reaction were measured by a pen pH meter. The relationship curve between acid production capacity and time was obtained. The acid production capacity increased with time. It tends to be stable after a certain time. The experiment of acid rock reaction kinetics shows that the reaction rate between acid and rock decreases with the extension of time. The reaction time can reach 6 h. The reaction rate of autogenic acid under different temperatures and concentrations ranges from 6.61 × 10 to 9.49 × 10 mol/(s·cm) within 6 h. Therefore, it indicates that the reaction time between autogenic acid and carbonate rock is long and the reaction rate is low. It is beneficial to improve the acid treatment effect of the carbonate reservoir. The conductivity experiments show that at different temperatures, with the increase of sealing pressure, the etching ability of autogenic acid decreases. The etching effect is better at 338 K. After etching, the permeability and conductivity of the rock slab of 5 MPa closure pressure are 227 D and 72.62 D·cm, respectively. To sum up, this autogenic acid is an effective working fluid in the acid fracturing process of the carbonate reservoir. It can obviously reduce the reaction rate of acid rock and has certain conductivity.
作为碳酸盐岩储层酸压裂过程的重要组成部分，酸压裂工作液的性能直接影响油井的增产效果。本文以甲醛（A剂）和氯化铵（B剂）为基体，配制了几种不同体积比的醛类，通过氢氧化钠滴定实验筛选出产酸量最高的酸比。结果表明，当A剂与B剂的体积比为1:1.3时，产酸能力最强。用便携式pH计测定了酸反应过程中几个时间点的pH值，得到了产酸量与时间的关系曲线。产酸量随时间增加，在一定时间后趋于稳定。酸岩反应动力学实验表明，酸与岩石的反应速率随时间延长而降低，反应时间可达6h，自生酸在不同温度和浓度下6h内的反应速率范围为6.61×10至9.49×10mol/(s·cm)。因此，表明自生酸与碳酸盐岩的反应时间长且反应速率低，有利于提高碳酸盐岩储层的酸处理效果。导流能力实验表明，在不同温度下，随着闭合压力的增加，自生酸的刻蚀能力降低，在338K时刻蚀效果较好。5MPa闭合压力下岩板刻蚀后的渗透率和导流能力分别为227D和72.62D·cm。综上所述，这种自生酸是碳酸盐岩储层酸压裂过程中的一种有效工作液，能明显降低酸岩反应速率，且具有一定的导流能力。
