Production and recovery chemistry for low-level hydrogen sulfide containing natural gas

低硫化氢天然气的生产与回收化学技术****加拿大页岩气储量丰富，分布在7个省。目前已知至少有两个加拿大页岩区含酸，硫化氢含量高达500ppm。在运输到市场之前，出于毒性/环境原因，H2S必须降至4ppm以下，CO2必须降至2%以下以保持热量含量。H2S含量低于2%的生产液不适合常规的H2S氧化来回收商业单质硫；因此，加拿大生产商需要采用替代化学工艺来达到4ppm的目标。整体研究的重点是通过了解这些低水平H2S来源和探索替代氧化工艺来解决这一需求。具体的研究目标旨在(i)扩展热页岩储层酸化的动力学模型，（ii）评估致密相CO2中的高压催化作用，以及（iii）探索联苯和二苯基醚共晶混合物中的工业硫化学。****(i)热页岩储层酸化动力学建模****我们之前已经证明，非微生物储层酸化可以通过压裂液添加剂（如十二烷基硫酸钠）的降解发生。我们最近的工作主要集中在天然硫化物（H2S或金属硫化物）的快速氧化，在有限的时间内产生储层中的单质硫。这种单质硫可以氧化其他碳氢化合物或液压油添加剂，热生成H2S。该领域的研究将继续侧重于凝胶压裂添加剂（与滑溜水添加剂相比）。这项研究将帮助生产商确定H2S何时会出现在流体中，以及在一口井的生命周期内预计会产生多少H2S。****(ii)致密相CO2高压催化****管理低水平H2S生产的来源是困难的，因为(a)低水平H2S生产不能支持传统克劳斯热反应器中的火焰，(b)替代低水平选择很少产生商业质量的硫。H2S在压力下的催化直接氧化可以完成，而无需昂贵的纯CO2再压缩，并提供两个增值产品；即CO2和S8。高压多相催化研究正在应用于确定该工艺的操作条件。****(iii)联苯和二苯基醚共熔混合物中的硫化学（Dowtherm®a）***在一些硫回收过程中使用PEG等碳氢化合物溶剂；但是，由于与单质硫发生反应，不能使用较高的温度。对于替代溶剂，我们正在探索在Dowtherm®a中开展常见的工业硫化学物质***这三个研究领域的进展有助于新兴低碳能源的安全和可持续发展。* * * * * * * *

PRODUCTION AND RECOVERY CHEMISTRY FOR LOW-LEVEL H2S CONTAINING NATURAL GAS****Canada has significant shale gas reserves which span 7 provinces. At least two Canadian shale plays are known to be sour and can contain up to 500 ppm H2S. Before transportation to market the H2S must be reduced to less than 4 ppm for toxicity/environmental reasons and CO2 is reduced to less than 2% to maintain caloric content. Production fluids with less than 2% H2S are not suitable for conventional oxidation of H2S to recover commercial elemental sulfur; therefore, alternative chemical processes are required by Canadian producers to achieve the 4 ppm target. The overall research is focused on addressing this need by understanding these low-level H2S sources and exploring alternative oxidation processes. Specific research goals are aimed at (i) expanding kinetic models for souring of hot shale reservoirs, (ii) evaluating high-pressure catalysis in dense phase CO2, and (iii) exploring industrial sulfur chemistry in a eutectic mixture of biphenyl and diphenyl ether.****(i) Kinetic modelling for souring of hot shale reservoirs****We have previously demonstrated that non-microbial reservoir souring can occur through the degradation of fracture fluid additives (e.g., sodium dodecylsulfate). Our more recent work has focused on the rapid oxidation of native sulfides (H2S or metal sulfides) to produce elemental sulfur in the reservoir over a finite time. This elemental sulfur can then oxidize other hydrocarbons or hydraulic fluid additives to thermally generate H2S. Studies will continue in this area by focussing on gel fracture additives (versus slick water additives). This research will help producers identify when H2S will appear in the fluids and how much can be expected over the lifetime of a well.****(ii) High-pressure catalysis in dense phase CO2****Managing sources of low-level H2S production is difficult, because (a) low H2S production cannot support a flame in the conventional Claus thermal reactor and (b) the alternative low-level options rarely produce commercial quality sulfur. The catalytic direct oxidation of H2S at pressure can be completed without costly recompression of pure CO2 and provide two value-added products; namely CO2 and S8. High-pressure heterogeneous catalysis research is being applied to define the operating conditions for such a process.****(iii) Sulfur chemistry in a eutectic mixture of biphenyl and diphenyl ether (Dowtherm® A)***Hydrocarbon solvents such as PEG are used in some sulfur recovery processes; however, higher temperatures cannot be used due to reaction with elemental sulfur. For an alternative solvent, we are exploring carrying out common industrial sulfur chemistries within Dowtherm® A. ***Progress in all three of these research areas help with the safe and sustainable development of emerging low-carbon energy sources. ********