硫酸盐热化学还原作用的启动机制研究

硫酸盐热化学还原作用(TSR)是导致高含硫化氢天然气生成和聚集、碳酸岩盐储层酸化和溶蚀的重要因素,是地质盆地内烃-水-岩三者之间的复杂反应。本文利用黄金管热模拟实验,对TSR反应的可能启动机制及控制因素进行了研究。通过不同盐溶液与原油的热解实验,证实了硫酸盐的存在是启动TSR反应的必要因素,MgSO4比CaSO4和Na2SO4更容易启动TSR反应,体系中盐度的增加会加速H2S的生成。实验结果表明,不同水介质条件下,TSR反应的程度与溶液的离子强度呈正相关,弱酸性环境并不足以启动TSR反应;原油中不稳定含硫化合物的含量越高越有利于TSR反应的发生,饱和链烷烃比原油中其它组分更容易引发TSR反应,且大分子烷烃比小分子烷烃更容易被硫酸盐氧化。

Research on the initiation mechanism of thermochemical sulfate reduction (TSR).

Thermochemical sulfate reduction (TSR), which includes a series of complex chemical reactions involving hydrocarbons, water and rocks in sedimentary basins, is an important reason leading to the occurrence and accumulation of natural gas with high hydrogen sulfide content, the acidification and corrosion of carbonate reservoir. In this paper, we try to elucidate the initiation mechanism and the controlling factors for TSR under gold-tube pyrolysis. By hydrous pyrolysis of oil with various inorganic salts (including chlorides and sulfides), it was attested that the presence of sulfate should be the essential factor for initiating TSR, MgSO₄ will be more effective for the onset of TSR relative to CaSO₄ and Na₂SO₄, the generation rate of H₂S can be accelerated with the increase of salinity of the solution in MgSO₄ system. Meanwhile, the experiments results indicated that TSR reaction rate is positive with the ionic strength of solutions, while weak acid conditions were demonstrated to be hard to initiate TSR. High content of organic labile sulfur compounds will avail the occurrence of TSR, saturated paraffin, especially those with larger-weight, are easier to be oxidated by sulfate relative to other groups in crude oils.