Origin of High Salinities in Hydraulic Fracture Flow Back Fluids - An Example from the Haynesville Shale Gas Play, USA

Economic development of shale gas resources requires successful hydraulic fracture stimulation of the gas-bearing shale utilizing significant volumes of water. The availability, treatment and disposal of this water are significant non-technical risks and can be important factors impacting the viability of shale gas opportunities. A typical Haynesville hydraulic fracturing job requires ~11,000 barrels of water and a total of ~350,000 lbs of proppant. The water initially injected into the subsurface is fresh, typically with a TDS content of 1 to 5 kppm (TDS = Total Dissolved Solids). However, clean up and recovery of the fracture fluids prior to bringing gas on stream typically recovers only ~5 to 10% of the originally injected volume of water. This water tends to be highly saline, often with TDS contents of ~200 kppm. Similar observations have been reported from other shale gas plays such as the Barnett and Marcellus. This begs the obvious question “Where did all the water go?”.