页岩中粒径与甲烷吸附能力关系的实验研究
Summary
采用等温吸附装置, 重量吸附分析仪, 对不同粒径的页岩的吸附能力进行了测试, 找出了泥页岩的粒度与吸附能力之间的关系。
Abstract
页岩气的吸附量是页岩油气资源评价和靶区选择的关键参数, 也是评价页岩气开采价值的重要标准。目前, 关于颗粒粒度与甲烷吸附的相关性研究具有争议性。本研究采用等温吸附仪 (重量吸附分析仪) 对页岩中不同粒径的吸附能力进行测定, 以确定页岩的粒度与吸附能力之间的关系。Thegravimetric 方法需要较少的参数, 并且在精度和一致性方面比体积法等方法产生更好的结果。重量测量执行四步: 空白测量, 预处理, 浮力测量, 吸附和解吸测量。重力测量被认为是一种比较科学、准确的测定吸附量的方法;然而, 这是耗时的, 需要一个严格的测量技术。磁悬浮平衡 (MSB) 是验证该方法的准确性和一致性的关键。结果表明, 吸附能力和粒度是相关的, 但不是线性相关的, 而被筛入 40-60 和 60-80 网格的粒子中的吸附往往较大。我们建议, 在页岩气压裂中, 与颗粒尺寸相对应的最大吸附量约为250µm (60 目)。
Introduction
页岩是一种粘土岩, 具有薄层的床上用品结构, 可作为页岩气源岩和储层。页岩具有很强的各向异性, 由纳米和微米的孔隙组成, 笔石化石通常被公认为1、2、3。
页岩气是中国南方长江板块的商业开采。页岩气作为一种非常规气体系统, 既用作源岩, 又作为甲烷的储层, 通过生物和/或热量过程4、5, 从页岩中的有机质中获得。储层中的天然气储存有三种形式: 孔隙和裂缝中的自由气体、有机质或无机矿物表面的吸附气体、沥青和水中溶解气体6、7。以往的研究表明, 在页岩地层中, 吸附气体占总气体的 20-85%, 为6。因此, 研究页岩的吸附能力及其控制因素对页岩气资源的勘探开发具有重要意义。
页岩的甲烷吸附能力在温度、压力、湿度、成熟度、矿物组成、有机质和特定表面积1、4、5 等方面得到了广泛的认可. ,6,7;先前的研究证实了温度、压力、湿度和甲烷吸附等外部因素之间的更大和更清晰的相关性。
然而, 研究颗粒粒度和甲烷吸附等内在因素之间的相关性是有争议的。康和纪表明, 同一页岩样品的甲烷吸附量随粒径8、14的减小而增大, 而 Rupple 和张认为颗粒粒度与吸附的相关性有限。根据等温吸附曲线9,10,11。此外, 在无页岩气吸附评价协议标准的情况下, 中国的实验室通常采用煤吸附评价协议评价页岩气的吸附。为了阐明颗粒粒度与吸附的关系, 并研究了一个远景勘探区, 本文从上扬子板块的五菱凹陷厚海洋页岩矿床中获得了页岩样品。采用重量吸附分析仪进行等温吸附 experimentand 得到颗粒尺寸与吸附的关系。
容积和重量法是测定页岩等温吸附的主要方法。容积是容积法的关键参数, 易受温度和压力12、13、14的影响。由于误差分析的不确定性, 用容积法计算吸附量的直接测量中的累积传播导致测量结果中出现较大误差, 导致异常吸附等温线14 ,15。与容积法相比, 重量法要求的参数少, 误差较小: 由于质量守恒, 重力法的重量和质量不受温度和压力12的影响。它被认为是一种比较科学、准确的测量活性炭纤维吸附量的方法。
本实验采用重量吸附分析仪, 其最大试验压力为70兆帕 (700 巴), 温度为150摄氏度。旧仪器产生的温度和压力过低 toaccurately 模拟深部地下地层的温度和压力。使用吸附分析装置的关键是达到磁悬浮平衡, 精确称量样品材料, 精度为10µg。该装置采用循环油浴加热方式, 温度范围可长期控制在0.2 摄氏度以内。旧仪器的精确度很低, 因此误差将大于用较新仪器获得的精度。实验操作用该仪器提供的软件进行。操作系统将定期更新, 以确保分析接近实际的地下条件12。
在重量法中, 采用磁悬浮平衡 (MSB) 测试了在正常温度和压力下, 试样与设备之间没有直接接触的甲烷等温吸附。样品放置在测量池中, 通过非接触悬浮耦合机构12、13, 可以将试样的重量传递到平衡。在平衡, 有一个悬浮磁铁, 由特别设计的控制器控制, 允许自由悬浮在下面的永久磁铁。永磁体将位置传感器和样品容器与联轴器架连接起来。耦合框架的作用是将样品容器耦合或解耦至永磁悬浮杆14、15、16。
我们测量的样品是在贵州省道真仡佬族苗族自治县的长的最大形成的海洋相沉积的黑色富有有机质的页岩, 下志留纪。研究区位于五菱凹陷, 上扬子板块, 毗邻四川盆地西北和雪峰山构造带, 西南17。五菱凹陷是四川盆地与雪峰山构造带之间的构造转移和过渡带, 受浅层深海陆架沉积, 在早期志留系中, 海洋黑页岩被广泛开发;当时的凹陷是由印支运动、燕山运动和喜马拉雅运动等构造事件强烈叠加而成, 形成了多级褶皱、断层和不整合面18。五菱凹陷海相黑色页岩受复杂地质条件的影响, 形成页岩气储量。作为构造传递带, 凹陷是页岩气勘探的一个亮点, 其特点是变形较弱, 页岩气的生成和保存条件较好, 而19圈闭的自然裂缝匹配较好。
高压吸附测量是在一个标准化的程序的基础上进行的, 在等温吸附设备协议的指导下, 已在若干出版物10、11中全面阐述。,12,13,14,15,16. 等温吸附实验完成于中国地质科学院页岩油气研究与评价重点实验室。用磁悬浮平衡 (MSB) 进行的重量测量是在四步骤中进行的: 空白测量、预处理、浮力测量和吸附和解吸测量 (图 1,图 2)。
Protocol
Representative Results
Discussion
本实验所用材料见材料表。在去除样品池之前, 必须确认样品池中的温度和压力在常压和常温下;否则, 就会有受伤的危险。如果温度过高, 等待温度下降, 然后 removethe 样品池。如果压力过高或过低, 则手动设置软件的气压, 并使用惰性气体13、14、15。在实验期间不要拆卸样品池。实验完成后, 仪器处于待机状态。耦?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
陈和陶都提供了大量的帮助。这项工作得到了中国主要国家研究发展计划 (2016YFC0600202) 和中国地质调查 (格兰特号) 的财政支持。DD20160183)。我们感谢匿名审阅者提出的建设性意见, 大大改善了这篇论文。
Materials
| XRF D8 DISCOVER X-Ray diffractometer | Brook,Germany | 204458 | For mineralogy X-ray diffraction |
| EBSD three element integration system with spectrum | EDAX,USA | Trident XM4 | For nanoscale imaging (SEM) |
| Mercury injection capillary pressure (MICP) | USA micromeritics Instrument company | AutoPore IV 9520 | For the immersion method to measure macropores(Porosity) |
| Nitrogen gas adsorption at low temperature | USA micromeritics Instrument company | ASAP2460/2020 | For the low pressure nitrogen gas adsorption to measure mesopores and micropores(BET) |
| Finnigan MAT-252 mass spectrometer | ThermoFinnigan,USA | TRQ/Y2008-004 | For C isotope |
| LECO CS-230 analyzer | Research Institute of Petroleum Exploration and Development | 617-100-800 | TOC apparatus |
| 3Y-Leica MPV-SP photometer microphotometric system | Leica,Germany | M090063016 | Ro apparatus |
| Magnetic Suspension Balance Isothermal adsorption analyzer | Rubotherm,Germany | 2015-1974CHN | For methane adsorption tests |
| Sieve(20/40/60/80/100/120mesh) | Sinopharm Chemical Reagent Beijing Co.Ltd | 200*50GB6003.102012 | Used to screen samples |
| Absorbent cotton, hammer, tweezers and acetaldehyde | Sinopharm Chemical Reagent Beijing Co.Ltd | standard | Used to clean materials |
| Residual gas tight grinder | Nantong Huaxing Petroleum Instrument Co., Ltd | TY2013000237 | Sample smasher |
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