页岩气井邻井压裂干扰响应特征及机理探讨:以涪陵页岩气田为例

Response characteristics and mechanism for fracturing interference of ad-jacent wells of shale gas wells:A case study in the Fuling shale gas field

涪陵页岩气田是我国探明储量最大的非常规页岩气田,储层以页岩为主,具有低孔低渗、非均质性强等特点。自2018年率先在国内部署开发调整井并实施水力压裂,面临着由于压力场变化导致周围老井压力异常变化,从而影响老井正常生产等问题,给气田采收率的提升带来了不确定的因素。从已产生影响的一次井网老井生产情况来看,邻井压裂影响干扰特征呈现多类型、多特征、多结果、多主控因素的特点,而目前还没有统一的邻井压裂干扰响应特征描述方法和机理解释。以涪陵页岩气田为例,在大量文献调研的基础上,基于一次井网整体有效动用程度,开展了页岩气井邻井压裂干扰响应特征及机理探讨。研究表明:(1)页岩气邻井干扰按照对母井技术可采储量的影响结果分为正面、无、负面干扰3种类型,造成3种干扰类型的差异主要与子母井空间井距、穿行层位、采出程度、地层压力、应力差异等因素相关;(2)初步明确了产生邻井压裂干扰的机理是子井和母井裂缝沟通程度及两者人工缝网重叠程度不同;(3)根据干扰带来的不同结果需采取合理的井距设计,压裂施工前采取母井关井恢复压力至稳定状态、子井压裂施工期间采取远场封堵转向压裂技术等方式规避负面影响。研究结果为制定合理的压裂防干扰措施提供了理论支撑,对行业具有良好的指导意义。

[Objective]Regarding conventional gas resources,research on the fracturing interference of adjacent wells has focused mainly on interference during the production process;the interference of adjacent wells is usually avoided by determining the rational spacing between wells,and the radius of influence is the key to determining a reasonable well spacing.The fracturing interference of shale gas adjacent wells involves various types,phenomena,results and control factors;however,there is no generally accepted description method or mechanism for studying the response characteristics of the fracturing interference of adjacent wells.[Methods]The Fuling shale gas field is taken as an example to discuss the response characteristics and mechanism of the fracturing interference of adjacent wells in shale gas.[Results]According to the impact on the recoverable reserves of parent wells,the fracturing interference of shale gas adjacent wells can be divided into three types:positive interference,noninterference and negative interference.The three types of interference are mainly related to the spacing of the child and parent wells,crossing layers,recovery percentage,formation pressure,stress difference and other factors.The closer the spacing and crossing layers between wells are,the greater the recovery degree of the parent wells or the lower the formation pressure is,the greater the difference between both sides of the stress of the child well becomes,and the greater the fracturing interference becomes.On the basis of the different results caused by fracturing interference,to avoid negative effects,shale gas development requires the formulation of reasonable well spacings,the shuttling of parent wells to restore the pressure until it stabilizes before fracturing,and the use of diverters during fracturing of new child wells.The generation mechanisms of fracturing interference are the degree of fracture and the overlap of artificial fracturing networks between child wells and parent wells.The ideal situation is that the fracturing network edge of the child wells just reaches the fracturing network edge of the older parent wells,which has a positive effect on increasing production;however,the noninterference type does not occur when the child wells′SRV is insufficient,nor does the negative interference type occur when the fracturing networks are connected between the child wells and parent wells.[Conclusion]The research results provide theoretical support for formulating reasonable fracturing interference prevention measures and have good guiding significance in industry.