In many cases, the cleat system of undisturbed coals will be water filled and subjected to a hydrostatic head that exceeds the desorption pressure of gas occupying pores in the coal matrix.
Therefore, water must be removed to lower the hydrostatic head below the gas desorption pressure to initiate coal seam gas (CSG) production.
This dewatering phase can last many months, or in some cases years, before the onset of gas production can occur.
To compress this dewatering timescale, some form of submersible pump is usually incorporated in the CSG completion design.
Qteq’s PumpTraq system provides continuous monitoring of downhole annulus pressure to track water fluid level in CSG wells.
This enables CSG operators to optimise dewatering strategies, to limit dewatering timescales and to safeguard against rapid well pumpdown during start-up operations, which can result in significant completion skin and thus loss of CSG productivity.
PumpTraq data is also used to safeguard against the pump-off condition, which can lead to rapid failure of the submersible pump, necessitating frequent and costly CSG well workovers.
The PumpTraq system has been custom-designed for CSG environments and employs an intrinsically safe (IS-rated) pressure sensor that outputs a 4-20 mA signal direct to the CSG operators’ infield instrumentation ecosystem or third party pump controller.
Very extensive best practices have also been developed to ensure reliable installation and long-term performance.
Optimise CSG dewatering strategies
Prevent pump-off condition
Prevent rapid pumpdown
Monitor pressure transients during planned and unplanned shutdowns.