Mechanism of Ultra-Low Water Recovery Rate with High Productivity in Fuling Gas Shale Filed

Shale gas formation is sensitive to high water saturation due to its ultra-low porosity and permeability, if too much fracture fluid were held up into the formation, water block and formation damage phenomenon will happen. In Fuling shale gas field, a lot of wells get ultra-low flowback rate without causing any water block or productivity loss even shows an increasing tendency in productivity with a lower flowback rate. Focusing on this unusual phenomenon, pore-fracture system properties in Fuling were investigated by experiments under multiscale. The pore-fracture system and imbibition characteristics are the key mechanisms. we divided pore-fracture system in Fuling into four levels, among which highly developed bedding fractures and micro-fractures in Fuling play vital role in the enhancement of imbibition capacity of the formation and help keep high conductivity of the fracture system before and after fracturing fluid recovery. We also find Graptolite fossils in the key that make bedding fractures unique in Fuling.