超深巨厚油藏顶部注烃气提高采收率调控机制

Regulation mechanism of EOR for natural gas crestal injection in super deep and thick reservoir

关键词:  超深巨厚油藏  烃气驱  混相能力  注入气突破  提高采收率

Key words:  super deep and thick reservoir  natural gas flooding  miscibility  gas breakthrough  EOR

摘要:

以超深巨厚D油藏顶部注烃气开发为背景,针对注入气气源不稳定、甲烷物质的量分数增加的现场情况,开展细管实验和长岩心驱替实验,研究多种烃气/地层油混相能力、驱替特征及产出流体组分变化规律。根据5种不同组成注入气/地层油的混相能力实验,得到最小混相压力与注入气中甲烷物质的量分数的对数计算关系式。通过长岩心驱替实验中产出端多次取样,分析不同驱替阶段的产出流体组分变化规律。结果表明:D油藏目前注入气与地层油的最低混相压力为38.9 MPa,在目前地层压力42 MPa下可以实现混相驱,且最终驱油效率达81.35%；注入烃气中甲烷物质的量分数小于92.38%时能确保D油藏实现烃气混相驱；注入气突破后产出流体中轻质组分物质的量分数增加,重质组分物质的量分数降低。

Abstract:

Considering natural gas crestal injection in super deep and thick reservoir and in view of the instability of injected gas source and the increase of methane content, a series of slim tube experiments and longcore flooding experiments were conducted. The miscibility evaluation of various natural gas, formation oil, as well as the change regulation of production fluid components were investigated. Based on miscibility experiments of five different compositions natural gas and formation oil, the logarithmic relationship between the MMP(minimum miscible pressure) and the methane content in the injected gas were obtained. Through the longcore displacement experiment, many production samples were taken to analyze the variation law of produced fluid components in different displacement stages. It is found that the MMP of D reservoir is 38.9 MPa for current injection natural gas, and the driving efficiency is 81.35% at the formation pressure of 42 MPa. The maximum content of methane is 92.38% in the injected gas to ensure natural gas miscible flooding. According to the longcore flooding experimental results, after the breakthrough of injected gas, the content of light components in the produced fluid increases and heavy components decreases.