潜山裂缝型凝析气藏注气开发机理  

Research on the mechanism of gas-injection development for buried-hill fractured condensate gas reservoirs

作　　者：张利军 赵林 谭先红 ZHANG Lijun;ZHAO Lin;TAN Xianhong(National Key Laboratory for Efficient Development of Offshore Oil and Gas,Beijing 100027,China;CNOOC Research Institute Co.,Ltd.,Beijing 100027,China)

机构地区：[1]海洋油气高效开发全国重点实验室,北京100027 [2]中海油研究总院有限责任公司,北京100027

出　　处：《天然气地球科学》2024年第2期357-365,共9页Natural Gas Geoscience

基　　金：中国海洋石油集团有限公司“十四五”重大攻关工程项目“海上低渗及潜山油气田有效开发技术”(编号:KJGG2022-0700)资助。

摘　　要：为指导潜山裂缝型凝析气藏的有效开发,分别开展长岩心注气实验及纵向剖面模型注气实验,从驱油效率及纵向波及程度两方面深入认识潜山裂缝型凝析气藏注气开发机理。研究表明,对于衰竭开发,裂缝储层凝析油采出程度在前期(>32 MPa)高于无裂缝均质储层,但中后期(<32 MPa)低于无裂缝均质储层。在最大反凝析液压力(23 MPa)和废弃压力(5 MPa)下,裂缝使采出程度分别降低1.37%和4.77%。在最大反凝析液压力下注气,均质储层的凝析油采出程度提高20%,且与渗透率关系不大;受气窜影响,裂缝储层的凝析油采出程度仅提高13.7%。注气过程中,裂缝储层的气油比曲线呈双台阶状上升,拐点分别位于0.4 HCPV、1.4 HCPV,反映了裂缝和基质—裂缝2类气窜通道的形成。凝析油采出程度的增加主要位于注气阶段,后续衰竭阶段相比直接衰竭开发的增加幅度较小。结合注气PVT实验,认为注气提高驱油效率的机理主要为保压和驱替。注气时机方面,无裂缝储层的高压注气效果显著优于低压注气,但对裂缝储层影响不大。对于纵向波及程度,无裂缝储层的隔夹层遮挡对重力分异存在一定的阻碍作用,但重力驱特征整体上较为明显,顶部气驱程度最高;裂缝潜山高角度裂缝发育,阻碍了注入气在注采井间的横向运移,重力驱特征相对较弱,未形成明显低饱和度区,中部气驱程度最高。研究将对潜山裂缝型凝析气藏注气开发方案设计及动态跟踪调整提供有效指导。To guide the effective development of buried-hill fractured condensate gas reservoirs,in this paper,the experiments of gas injection into long cores and vertical-profile models are performed,which aims to study mechanisms of gas injection in terms of oil displacement efficiency and vertical sweep efficiency for buried-hill fractured condensate gas reservoirs,respectively.Results show that,for the depleted development,the oil recovery of fractured formation is higher than that of non-fractured homogeneous formation at early stage(>32 MPa),but turns to be lower at mid-late stage(<32 MPa).Under the maximum condensate pressure(23 MPa)and abandonment pressure(5 MPa),fractures reduce the recovery rate of condensate oil by 1.37%and 4.77%,respectively.Injecting gas at maximum condensate pressure increases the recovery rate of conden⁃sate oil by 20%for homogeneous formation,and is not closely related to permeability.Affected by gas channel⁃ing,the recovery rate of condensate oil increases by 13.7%for fractured formation.During the gas-injection,the fractured formation presents two types of gas channels,i.e.,fracture and matrix-fracture,which is inferred from the dual-step pattern in gas-oil ratio curve whose inflection points are 0.4 HCP and 1.4 HCPV,respective⁃ly.The oil recovery increases significantly during gas injection,but is essentially coincidence with that in the full-time depletion during the subsequent depletion stage.Combining the gas-injection PVT experiments,it is proposed that the pressure maintaining and oil displacement,serve as the main mechanisms for improving oil displacement efficiency.In terms of the gas injection timing,the effect of high-pressure gas injection is signifi⁃cantly better than that of low-pressure gas injection for non-fractured reservoirs.As for fractured reservoirs,the impact of gas injection timing is not significant.In terms of vertical sweep efficiency,the barrier of the non-frac⁃tured reservoir has a certain obstruction effect on the gravity differentiation,but the grav

关 键 词：潜山裂缝 凝析气藏 注气机理 重力分异 

分 类 号：TE372[石油与天然气工程—油气田开发工程]