国外某油田放空天然气轻烃回收工艺研究

Study on Light Hydrocarbon Recovery from Vent Gas of an Overseas Oilfield

由于国外某油田伴生气全部用于放空,为了提高资源利用率,保护生态环境,对该放空天然气进行C3+组成回收,生产液化石油气(LPG)和凝析油。为此,开展了丙烷制冷+膨胀机制冷+DHX工艺回收轻烃方案设计研究,采用天然气两级预冷的丙烷制冷+膨胀机制冷+DHX工艺,并进行工艺参数优化。研究结果表明:设计的三种轻烃回收方案均能满足产品天然气中组成指标要求,DHX塔操作压力增加导致脱乙烷塔顶气抽出量明显增加,在满足产品天然气指标条件下,脱乙烷塔顶气抽出量范围逐渐变窄;DHX塔操作压力一定时,随着脱乙烷塔顶气抽出量增加,产品天然气中丙烷含量先减小后增加。较优的工艺参数是原料天然气一级预冷温度5℃,二级预冷温度-35℃,DHX塔操作压力1.60 MPa,脱乙烷塔操作压力3.05 MPa,脱乙烷塔顶气抽出量585 kmol/h。放空天然气能够回收LPG和凝析油47.97 t/d,生产天然气280×10^4 m^3/d,经济效益显著。该研究成果对国内外油气田开展放空天然气回收利用具有参考意义。

An overseas oilfield vented all its associated gas.To improve resource utilisation rate and preserve the environment,it was decided to recover C 3+fraction in the associated gas,to produce LPG and condensate.For this purpose,the process system comprising propane refrigeration,expander and DHX process was studied.A two-stage natural gas pre-cooled propane refrigeration+expander refrigeration+DHX process was employed with optimized process parameters.The research results show that the three schemes designed for light hydrocarbon recovery can meet the composition index requirements of the product gas.The increase in the operating pressure of the DHX tower leads to a significant increase in the amount of overhead gas extraction from the deethanizer.The range of overhead gas extraction gradually narrows during this process when the composition index of product gas is met.With the constant operating pressure of the DHX tower,as the amount of overhead gas extraction of the deethanizer increases,the propane content in the product gas first decreases and later increases.The optimized primary pre-cooling temperature of the feed gas is 5℃and the secondary pre-cooling temperature is-35℃,with the operating pressure of the DHX tower and deethanizer being 1.60 MPa and 3.05 MPa respectively.The amount of overhead gas extracted from the deethanizer is 585 kmol/h.The capacity of optimized process for LPG and condensate oil recovery is 47.97 t/d,with gas production rate being 2.8 million m 3/d,which brings about significant economic benefits.The optimized process can be a valuable reference for the recovery and utilization of vented natural gas in oil and gas fields at home and abroad.