页岩气井带压作业关键技术与应用评价

Key technologies for snubbing operation of shale-gas wells and their application

气井带压作业作为川渝页岩气区块完井增产的有效手段,已逐步在中国石油长宁—威远、中国石化涪陵等国家级页岩气示范区块推广应用。为了解决气井带压作业中环空动密封、管柱内密封压力控制及管柱压弯的技术难题,通过优化环空动密封装置组合、对比管柱内密封工具优缺点、建立管柱极限抗弯长度计算模型,制定了环空动密封、管柱内密封方案及管柱抗弯计算公式,形成了页岩气井带压作业关键技术,并对4口井带压作业应用效果进行评价。研究结果表明:①当井口压力小于13.8 MPa时,带压起下管串时至少配备一个环形动密封装置及一个闸板式动密封装置,当井口压力大于13.8 MPa时,至少配备一个环形动密封装置及两个闸板式动密封装置;②定压接头或陶瓷堵塞器是目前气井带压下油管最常用的内密封工具,定压接头安全可靠,陶瓷堵塞器密封效果好,二者配合使用效果最佳;③计算管柱极限抗弯长度,确保液缸行程不超过极限抗弯长度是防止压弯管柱的有效方法;④4口井带压作业应用效果较好,增产效果明显。

As an effective tool for completion and stimulation in Chuanyu shale-gas block,snubbing operation of gas wells has been gradually popularized and applied to other national shale-gas ones,e.g.PetroChina's Changning-Wei yuan block and Sinopec's Fuling block.However,snubbing operation is faced with some technical difficulties of annulus dynamic seal,string internal seal pressure control,and string bending.So,annulus dynamic seal,string internal seal scheme,and string bending resistance calculating formula were established by optimizing an assembly of annulus dynamic seal device,comparing both advantages and disadvantages of string internal seal tools,and building up one model to calculate bending resistance length limit of string.Then,some key technologies for snubbing operation of shale-gas wells were developed.Finally,an application effects of snubbing operation to 4 wells were evaluated.Results show that(1)when wellhead pressure is lower than 13.8 MPa,to run in and out the pipe string under pressure,it's necessary to equip with one annulus dynamic seal assembly and one brake-type dynamic seal assembly at least,and equipped with one annulus dynamic seal assembly and two brake-type dynamic seal assemblies at least while wellhead pressure higher than 13.8 MPa;(2)constant-pressure joint and ceramic plug are currently the most common internal seal tools for running in tubing under pressure.Constant-pressure joint is safe and reliable,and ceramic plug is good in sealing effect,so their collaboration presents the best effect;(3)the effective method to prevent string bending is to calculate the bending resistance length limit of string and ensure the cylinder stroke not ex ceeding this limit;and(4)the application of snubbing operation to 4 wells has better effect,presenting a remarkable stimulation result.