塔里木盆地顺北超深断控型凝析气藏巨厚缝洞储层及流体相变对开发政策的影响

Impact of ultra-thick fracture-cavity reservoirs and fluid phase behavior on development strategies for Shunbei ultra-deep fault-controlled condensate gas reservoir, Tarim Basin

  • 摘要: 塔里木盆地顺北4号断裂带是国内规模最大的断控条带状立式巨厚缝洞型凝析气藏,该气藏兼具超深、超高温超高压、缝洞结构及流体相态变化规律复杂等特征,导致对其进行科学开发对策的选择与调整带来极大挑战。为明确储层架构及超临界复杂流体相态特征对该气藏开发技术政策的影响,运用缝洞型储层地质精细描述、超临界凝析气非平衡相态特征研究方法,结合气藏开采过程的生产动态,分析储层与流体耦合作用对开发技术政策的控制作用,厘清断控储集体孔缝洞纵深及沿长轴方向的发育特征,揭示复杂储集体地质特征对成藏及开发单元凝析油气分布的控制作用。研究认为在超高温超高压特征下,气藏从原始压力到露点压力的衰竭开采阶段,凝析油气采出程度可同步达到30%;通过测定露点到最大反凝析(Retrograde condensation)压力衰竭开采阶段的非平衡重力沉降弛豫现象,能推演出断控体储层中此弛豫时间(Relaxation time)可达3个月,同时探明注气过程气—气两相重力分异相态演化分层的控制作用,确定注气非平衡扩散时间可超1年;进一步明确气藏北、中、南段流体分布差异对开发政策的不同影响机制,以及注气部位选择对注气驱效果的作用规律。综合上述研究成果,针对性提出适配该类气藏的三段式开发方式,为顺北超深断控凝析气藏开发政策制定提供技术支撑,也为同类超深层断控缝洞型凝析气藏的高效开发提供参考。

     

    Abstract: The Shunbei No. 4 fault zone in the Tarim Basin is the largest fault-controlled, strip-shaped, vertical, and ultra-thick fracture-cavity condensate gas reservoir in China. This gas reservoir is characterized by ultra-deep burial, ultra-high temperature and pressure, complex fracture-cavity structures, and intricate phase behavior of reservoir fluids, posing significant challenges to the selection and adjustment of scientific development strategies. To clarify the impact of reservoir architecture and supercritical complex fluid phase characteristics on the development technical policies of this gas reservoir, methods including fine geological characterization of fracture-cavity reservoirs and non-equilibrium phase behavior study of supercritical condensate gas were employed, combined with the production dynamics during gas reservoir exploitation, to analyze the controlling effect of reservoir-fluid coupling on development technical policies, clarify the pore-fracture-cavity development characteristics in fault-controlled reservoirs both in depth and along the long axis direction, and reveal the controlling effect of complex reservoir geological characteristics on the distribution of condensate oil and gas in accumulation and development units. The study indicated that under ultra-high temperature and pressure conditions, during the depletion production stage from initial pressure to dew point pressure, the recovery degree of condensate oil and gas could simultaneously reach 30%. By measuring the non-equilibrium gravitational settling relaxation phenomenon during the depletion stage from dew point pressure to maximum retrograde condensation pressure, it could be deduced that the relaxation time within the fault-controlled reservoir could reach 3 months. Additionally, the controlling effect of gravity segregation and phase evolution stratification of the gas-gas two-phase system during the gas injection process was explored, and the non-equilibrium diffusion time for gas injection was determined to exceed one year. It further clarified the different influencing mechanisms of fluid distribution differences in the northern, central, and southern sections of the gas reservoir on development strategies, as well as the effect of gas injection location selection on the effectiveness of gas injection displacement. Based on the above research findings, a three-stage development approach tailored to this type of gas reservoir is proposed, providing technical support for the formulation of development strategies for the Shunbei ultra-deep fault-controlled condensate gas reservoir, as well as serving as a reference for the efficient development of similar ultra-deep fault-controlled fracture-cavity condensate gas reservoirs.

     

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