Many coal seam gas wells are experiencing scaling problems, which impacts the productivity of the wells.
The reason this happens is that the geochemical equilibrium in the coal seams is disturbed during gas extraction activities. This equilibrium is a bicarbonate equilibrium under a high partial pressure of carbon dioxide (around pH 7.1). The high CO2 pressure allows calcium and magnesium to be somewhat soluble as bicarbonate based species.
As gas migrates through the seam towards the well bore, the pressure drops and this causes some carbon dioxide to leave the aqueous environment. This causes the pH of the aqueous phase to rise, and shifts the equilibrium to a scaling environment. At the surface the produced water may have a measured pH higher than 8, and this is because some CO2 has already been lost from solution. You may notice this CO2 in your gas samples.
In the formations, the pressure is lowest in the near well bore region, and so it is an attractive place for scale deposition to occur. This is also the place in the formation with the highest flux, and so any restrictions forming in this area will have an impact on performance.
Hard crystalline calcite scales have been observed in CSG wells. We can show you what these scales look like and demonstrate how ECOStim dissolves them.
Wells that are impacted by mineral scales are typically subjected to expensive interventions (i.e. workovers). If scaling is becoming a problem in your operations, we can help you with options to address scaling without the use of workover rigs. It is a lower cost philosophy.
ECOStim is used to dissolve scale which has formed in the near-wellbore region of the well, and also on the wet internal surfaces of the well. It is ideally applied as part of a regular well maintenance program with the intention of delaying / reducing the frequency of expensive well workovers. It may also be used during workovers to increase the effectiveness of the workover program.
It can also be used to stimulate new wells, where the intention is to dissolve naturally occurring mineral deposits which happen to be in the seam as part of the coal matrix.
This product has been used on coal seam gas wells in Queensland, and has been tested on coal cores at the University of Queensland, with excellent results.