CNPC Chuanqing Drilling Engineering
Co. Ltd. Downhole Service Co.
Hydration before hydraulic fracturing improves the connection between pores and natural fractures in
the Lower Silurian Longmaxi natural
gas shale in China’s Zhaotong area in
North Yunnan and
pilot studies demonstrated. The pilot
laboratory experiments done using
core samples. Water enters through
microcracks in the
natural fracture matrix through capillary self-absorption, propagating primary fractures.
Hydration serves as micro stimulation before hydraulic fracturing. Each
shale play must be independently
evaluated to determine its potential
for hydration. More research is needed into hydration’s effect on shale.
Longmaxi shale hydration before
hydraulic fracturing induced microfractures, promoting rock failure and
yielding a more complex fracture network. An increasingly complex fracture network reduces the required
pumping pressure and cuts hydraulic
China’s shale gas operators typically use multistage fracturing, pumping
1,000 cu m/min of proppant at nearly 15 cu m/min/stage
(OGJ, July 1, 2013, p. 70).
Longmaxi operators currently drill 1,500-m horizontal
Hydration improves Longmaxi shale fractures
A CT scan shows Longmaxi shale sample A before hydration (left) and after hydration
(right) (Fig. 1).
CT images of shale samples before (left) and after (right) hydration. (Fig. 2).
wells with 24 fracturing stages. Fracturing fluid recovery
is sometimes less than 10%. Researchers have studied both
how unrecovered fracturing fluid can be imbibed by the