以铝镁合金为代表的可降解金属材料具有质量轻、强度高、施工完毕后易返排等特点,在油气田开发领域已用于制造射孔枪、封隔器、桥塞以及压裂滑套等井下工具。但在使用过程中存在降解后产生化学反应、残渣堵塞油气通道等问题。为此,对这种现象开展机理研究,实验模拟要点：①根据市场应用情况,优选了基础成分为Mg—8Al—0.7Zn—0.25Mn—1.0Ce的可降解铝镁合金作为实验试样材料。②基于华北油田冀中地区某井试油作业所测得的地层产液成分数据,配置与其成分相近的含CaCl2等盐类的1#复配溶液,同时为了研究Ca2+对于铝镁合金试样的影响,配置了不含CaCl2的2#复配溶液。③为了模拟油气井富含CO2酸性环境,往实验的水溶液中持续注入CO2并保持20×105 Pa左右的分压,使呈弱酸性。④为模拟近地层环境,实验温度为150℃、实验设定的CO2分压为20×105 Pa（25℃）,在高温高压反应釜中分别装满经过充分除氧处理之后的1#、2#复配溶液,将可降解铝镁合金试样以挂片方式放入溶液,在不同的浸入时间后取出,观测试样的质量变化,采用扫描电镜（SEM, Scanning Electron Microscope）对试样表面附着物的形貌及其成分进行分析,从而研究Ca2+对可降解铝镁合金的影响。研究结果表明：①在高温、弱酸环境、矿化度较高的油气井,使用可降解铝镁合金制作的井下工具可能会形成以CaCO3为主、包含MgCO3、Mg(OH)2等的结晶残渣,堵塞油气通道。②对于150℃、富含CO2、弱酸性的近似地层环境,往井筒中添加含Ca2+的盐（如CaCl2）,欲采用这种方式来加速铝镁合金制成的井下工具的降解,反而不利于井下工具的有效降解,可能造成井筒的不洁或者堵塞。
Degradable metal materials represented by aluminum-magnesium alloys show characteristics of light weight, high strength, and easy flowback after utilization. They have been used to manufacture downhole tools such as perforating guns, packers, bridge plugs, and fracturing sleeves for oil and gas development. However, there exists some problems including chemical reaction after degradation and residues blocking oil and gas channels. To solve the problems, the mechanism was investigated by experiment simulation. Firstly, according to the market application, the degradable aluminum-magnesium alloy with Mg-8Al-0.7Zn-0.25Mn-1.0Ce as the basic composition was selected as sample for the experiment. Secondly, based on the measured composition of the formation fluid produced from a well in Jizhong area of Huabei Oilfield, a 1# compound solution containing CaCl2 with the similar composition was prepared. In addition, a 2# compound solution without CaCl2 was prepared to clarify the effect of Ca2+ on the sample. Thirdly, to simulate the CO2-rich acid environment in wells, CO2 was continuously injected into the experimental aqueous solution to make it weakly acidic, with partial pressure of about 20 bar. Lastly, to simulate the formation environment, the experimental temperature was set to 150ºC, and the CO2 partial pressure was set to 20 bar (25ºC). The 1# and 2# solutions were respectively injected into the HT/HP reaction kettle after being fully deoxidized, and then the degradable aluminum-magnesium alloy samples were put into the solutions. After soaking for different times, the samples were taken out to observe the quality changes. The morphology and composition of the attachments on the surface of the samples were analyzed by using Scanning Electron Microscopy (SEM), so as to identify the effect of Ca2+ on the alloy. Results show that (1) in wells with high temperature, weak acid environment and high salinity, downhole tools made of degradable aluminum-magnesium alloys may form crystalline residues mainly composed of CaCO3, as well as MgCO3, Mg(OH)2, etc., which can block the oil and gas channels; and (2) for the approximate formation environment (150ºC, CO2-rich and weak acid), the injection of Ca2+-containing salts (e.g. CaCl2) into wellbore to accelerate the degradation of downhole tools made of aluminum-magnesium alloys is not helpful to the effective degradation, and may cause uncleanness or blockage.
[1] 董明键, 郭先敏, 李子良. 可降解材料在完井工具中的应用及发展趋势[J]. 石油机械, 2015, 43(3): 31-34.
Dong Mingjian, Guo Xianmin & Li Ziliang. Application and future development of degradable materials in completion tools[J]. China Petroleum Machinery, 2015, 43(3): 31-34.
[2] 平恩顺, 王林, 邹鹏, 等. 分段压裂工具用可降解金属材料降解性能研究[J]. 石油化工应用, 2017, 36(2): 133-136.
Ping Enshun, Wang Lin, Zou Peng, et al.Research on degradation performance of degradable metal materials for staged fracturing tool[J]. Petrochemical Industry Application, 2017, 36(2): 133-136.
[3] 刘江浩, 张毅. 高温高压大通径压裂封隔器的研制[J]. 钻采工艺, 2016, 39(3): 77-79.
Liu Jianghao & Zhang Yi. Development of the large drift diameter fracturing packer[J]. Drilling & Production Technology, 2016, 39(3): 77-79.
[4] 张毅, 李景卫, 杨小涛, 等. 新型可降解压裂封隔器胶筒[J]. 油气井测试, 2019, 28(2): 51-55.
Zhang Yi, Li Jingwei, Yang Xiaotao, et al.New degradable fracturing packer rubber[J]. Well Testing, 2019, 28(2): 51-55.
[5] Zhang Y, Liu JH, Shi XL, et al.Preparation and properties of degradable metal materials for oil and gas wells[J]. Science Discovery, 2020, 8(2): 37-42.
[6] 管宝儒. 生物可降解镁基非晶合金的制备及电化学性能研究[D]. 南京: 南京理工大学, 2017.
Guan Baoru.Preparation and electrochemical properties of biodegradable Mg-based amorphous alloys[D]. Nanjing: Nanjing University of Science and Technology, 2017.
[7] 姜涛. Al基可降解合金的制备及性能研究[D]. 西安: 陕西科技大学, 2016.
Jiang Tao.Research on the preparation and properties of degradable Al alloy[D]. Xi’an: Shaanxi University of Science & Technology, 2016.
[8] 张毅, 于丽敏, 任勇强, 等. 一种新型可降解压裂封隔器坐封球[J]. 油气井测试, 2018, 27(2): 53-58.
Zhang Yi, Yu Limin, Ren Yongqiang, et al.A new type of degradable setting ball for fracturing packers[J]. Well Testing, 2018, 27(2): 53-58.
[9] Aviles I, Marya M, Hernandez TR, et al. Application and benefits of degradable technology in open-hole fracturing[C]//SPE Annual Technical Conference and Exhibition, 30 September-2 October2013, New Orleans, Louisiana, USA. DOI: 10.2118/166528-MS.
[10] Salinas BJ, Xu ZY, Agrawal G, et al. Controlled electrolytic metallics-An interventionless nanostructured platform[C]//SPE International Oilfield Nanotechnology Conference and Exhibition, 12-14 June2012, Noordwijk, The Netherlands. DOI: 10.2118/153428-MS.
[11] Zhao BW, Zhao ZW, Bao LD, et al.Preparation and properties of PVAL/modified starch composite foaming materials[J]. Engineering Plastics Application, 2017, 45(10): 103-107.
[12] 王林, 张世林, 平恩顺, 等. 分段压裂用可降解桥塞研制及其性能评价[J]. 科学技术与工程, 2017, 17(24): 228-232.
Wang Lin, Zhang Shilin, Ping Enshun, et al.Development and performance evaluation of the degradable bridge plug for staged fracturing[J]. Science Technology and Engineering, 2017, 17(24): 228-232.
[13] 张毅, 卫国, 李军, 等. 可降解铝镁合金卡瓦基座的分析[J]. 机械制造, 2021, 59(6): 30-34.
Zhang Yi, Wei Guo, Li Jun, et al.Analysis of degradable aluminum-magnesium alloy slip base[J]. Machinery, 2021, 59(6): 30-34.
[14] 刘辉, 尹强, 喻成刚, 等. 页岩气水平井可溶性桥塞室内测试及现场试验[J]. 天然气勘探与开发, 2018, 41(2): 74-77.
Liu Hui, Yin Qiang, Yu Chenggang, et al.Lab and field tests of dissolvable bridge plug technology in shale-gas horizontal wells[J]. Natural Gas Exploration and Development, 2018, 41(2): 74-77.
[15] 王维刚, 朱君. 可取桥塞卡瓦锚爪的力学分析[J]. 石油机械, 2008, 36(11): 16-19.
Wang Weigang & Zhu Jun. Mechanics analysis of the slip fluke in retrievable bridge plug[J]. China Petroleum Machinery, 2008, 36(11): 16-19.
[16] 魏辽, 马兰荣, 朱敏涛, 等. 大通径桥塞压裂用可溶解球研制及性能评价[J]. 石油钻探技术, 2016, 44(1): 90-94.
Wei Liao, Ma Lanrong, Zhu Mintao, et al.Development and performance evaluation of dissolvable balls for large borehole bridge plug fracturing[J]. Petroleum Drilling Techniques, 2016, 44(1): 90-94.
[17] 周后俊, 程智远, 王海霞, 等. 新型压裂滑套水力喷射器的研制及应用[J]. 石油矿场机械, 2017, 46(1): 45-47.
Zhou Houjun, Cheng Zhiyuan, Wang Haixia, et al.Development and application of the new fracturing sliding sleeve hydraulic jet[J]. Oil Field Equipment, 2017, 46(1): 45-47.
[18] 袁广银, 章晓波, 牛佳林, 等. 新型可降解生物医用镁合金JDBM的研究进展[J]. 中国有色金属学报, 2011, 21(10): 2476-2488.
Yuan Guangyin, Zhang Xiaobo, Niu Jialin, et al.Research progress of new type of degradable biomedical magnesium alloys JDBM[J]. The Chinese Journal of Nonferrous Metals, 2011, 21(10): 2476-2488.
[19] 赵效锋, 管志川, 张晗, 等. 压裂过程中射孔段水泥环力学响应规律[J]. 断块油气田, 2017, 24(5): 695-699.
Zhao Xiaofeng, Guan Zhichuan, Zhang Han, et al.Mechanical response of perforated cement sheath through hydraulic fracturing[J]. Fault-Block Oil & Gas Field, 2017, 24(5): 695-699.
[20] 魏耀武, 李楠, 刘春桃. 铝镁合金对Al2O3-SiC-Al复合材料组成的影响[J]. 武汉科技大学学报, 2008, 31(3): 277-279.
Wei Yaowu, Li Nan & Liu Chuntao. Effect of AL-Mg alloy on the composition of Al2O3-SiC-Al composite[J]. Journal of Wuhan University of Science and Technology, 2008, 31(3): 277-279.
