注含氧氮气油藏产出气的爆炸极限与临界氧含量研究

Study on the explosion limits and critical oxygen content for the gas produced after oxygen containing nitrogen injection

西部某碳酸盐岩缝洞型油藏,在注入氮气的过程中,存在着氮气源内含有氧气的问题,这对油田的实际生产产生很大的安全威胁。为了研究该油藏注气的可行性,在室内进行了氮气不同含氧量条件下注入过程、生产过程以及处理过程中的安全性评估实验,得到不同含氧条件下注氮气驱的评价效果。研究表明:在高温高压油藏内部,氧气不会因分子质量较大等原因发生沉积;含氧氮气在油藏内部会与原油发生氧化反应,氧气含量越高,氧化反应越强;氧化产生的CO2对油藏的抽提作用明显,会使油藏流体变稠,气油比降低。文中用化学法和作图法对产出气体的临界氧含量作出简单确定,化学法确定临界氧含量为12%左右,作图法为16%,考虑到安全系数等因素,建议实际生产过程中氧气含量应低于8%。

Because the injected nitrogen source contains duction of the field in some western carbonate seam hole oxygen, there exists great security threats for actual pro type reservoir. Security assessment experiments were car ried during injection process, productive process and treating process under different oxygen content, to study the feasibility of the reservoir gas injection. Results showed that oxygen does not precipitate at high temperature and high pressure inside the reservoir. The nitrogen, containing oxygen, will react with reservoir, and the higher the oxygen content, the more severe the oxidation reaction. Moreover, CO2, produced from oxidation reaction, plays an obvious role in reservoir extraction. It can make the reservoir fluids thicken and gas oil ratio reduced. Chemical and plotting methods were used to roughly estimate the critical oxygen content in produced gas, which were respec tively 12%, 16%. Considering safety, it is suggested that oxygen content should be less than 8% in the process of actual production.