页岩气钻采技术综述

Shale Gas Drilling Technologies at a Glance

页岩气开采已成为全球资源开发的一个热点。页岩气储集层通常呈低孔、低渗透率,开采寿命长,生产周期长,采收率变化较大,且低于常规天然气采收率。不同于常规天然气的开采特点决定了页岩气开发具有其独特的方式。水平井技术对于扩大页岩气开发具有重大意义,水平井的成本一般是垂直井的1～1.5倍,而产量是垂直井的3倍左右。水平井技术结合geoVISION随钻成像服务和RAB钻头附近地层电阻率仪器等LWD技术可进行更高效、更合理的开采。压裂增产技术是页岩气开采的另一种方式。清水压裂技术用于产生更密集的裂缝网络,形成额外的渗透率,使气体能更容易流向井中,从而生产出大量地层天然气;多层压裂技术常常用于垂直堆叠的致密地层的增产;重复压裂技术用于在不同方向上诱导产生新的裂缝,从而增加裂缝网络,提高生产能力;还有最新的同步压裂技术,即同时对两口或两口以上的井进行压裂。这些压裂技术结合室内实验和测井技术,使得页岩气具有更大的发展潜力。

Shale gas has become a hotspot for resource development woddwide.A typical shale gas reservoir is characterized by low porosity,low permeability,long production life,long lead time,dramatic change of recovery and usually lower recovery than conventional natural gas.Determined by its characteristics different from conventional natural gas production,shale gas development has its unique pattern.Horizontal well technol- ogy is significant to expanding shale gas development.The cost of a horizontal well is typically 1-1.5 times that of a vertical well and output from a horizontal well is about 3 times that from the latter.Horizontal well technology,coupled with logging while drilling technologies such as geoVISION imaging while drilling technolo- gy and resistivity at the bit （RAB） tools,enables operators to produce shale gas more efficiently.Fracturing is another method for producing shale gas.Riverfrac treatment is used to produce denser fracture network to form additional permeability ,allowing for easier influx of gas into the wellbore ,thus producing large amounts of formation gas.Multilayer fracturing technology is usually used to stimulate vertically stacked tight formations. Refracturing technology is used to induce new fractures in different directions to increase fracture networks, thus raising productivity.The latest simultaneous fracturing technology is used to fracture two or more wells at once.With these fracturing techniques and laboratory and logging technologies available,shale gas development will be even more promising.