川西致密气藏裸眼水平井分段压裂技术

Multi-Stage Fracturing Techniques for Open Hole Horizontal Wells in Western Sichuan Tight Gas Reservoirs

  • 摘要: 川西中浅层气藏致密、低孔、低丰度,裸眼水平井分段压裂是开发该类气藏的有效技术之一,但存在压裂参数难确定、压裂管柱下入难度大、水平段钻井液替出困难、压裂液返排效率低等问题。为此,在分析气藏特点和借鉴多级压裂经验的基础上,提出将裸眼水平段分成8~10段进行压裂,砂比优化为17%~21%;在注入前置液阶段采用支撑剂段塞处理近井效应,降低初期施工压力及形成多裂缝的概率;设计了可完全替出水平段钻井液的压裂管柱;制定循环钻井液、旋转管柱和给管柱加压的措施,保证压裂管柱下至设计位置;采用液氮伴注和大小油嘴交替更换的助排和返排技术,提高压裂液返排的速度和效率。XP105-1H井的裸眼水平段分成8段,采用以上技术和措施成功分段压裂;压后自然返排,返排率达95%;压后天然气产量6.441 2×104 m3/d,是相同层位水平井的2倍,天然气无阻流量达到23.168×104 m3/d。XP105-1H井裸眼水平段分段压裂的成功,可为类似致密气藏裸眼水平井分段压裂提供有益参考。

     

    Abstract: RCWestern Sichuan shallow gas reservoirs are characterized as tight formation,low porosity and low abundance.For these types of reservoirs,a multi-stage open hole fracturing of a horizontal well is an effective method.However there are some difficulties associated with this technique such as the selection of fracturing parameters,running of fracturing string,displacement of mud in horizontal section and low flowback efficiency of fracturing fluid.Based on reservoir property analysis and multi-staged fracturing experience,it is suggested to fracture the open hole horizontal wells in 8 to10 stages with proppant concentration of 17%-21%.In the stage of fluid pad injection,a proppant slug is used to treat near wellbore effect,lower the initial fracturing pressure and avoid creating multiple fractures.Fracturing string for drilling fluid displacement in the horizontal section has been developed.Measures in mud circulation,string rotation and pressure application to string has been made to ensure the fracturing string can be run to the designed location.At the same time,liquid nitrogen injection and different sized chokes were employed to improve the rate and efficiency of fracturing fluid flow-back.Those measures were applied in 8 stages fracturing of Well XP105-1H successfully and natural flowback rate naturally reached up to 95%.Gas production of this well is 6.441 2×104 m3/d,two times of that of other horizontal wells in the same formation.It can be reference for similar open hole horizontal wells in tight gas reservoirs.

     

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