Recirculation to improve progressive cavity pumps (PCPs) run life

Abstract

Progressive cavity pumps (PCPs) are widely used as a method of artificial lift, commonly found in coal seam gas (CSG) wells in Queensland. One of the major challenges with PCPs is the pump torqueing up due to solids and not being able to restart, which results in lost production and the need for intervention with a flush-by unit or service rig. Up to 30% of PCPs in the Surat Basin can be down at any given time on account of this issue.

We have engineered a solution whereby fluid is produced using the existing PCP, a desander is used to remove solids and the clean fluid is reinjected down the annulus, via hollow rods or by a capillary string. This complete system has many benefits: it removes sands and solids from the wells produced water stream; and it reinjects clean water down the well bore, which serves the dual purpose of diluting the concentration of downhole solids and, via the introduction of additional clean fluid, allows the PCPs to be sped up, thus increasing the velocity to aid in lifting the solids out of the well.

This can all be done at a fraction of the cost of intervention with a flush-by unit or service rig. Lessons learned from field trials to date include: (1) how to account for loss of reinjected fluid in early field trials, which was solved by the introduction of hollow rods; (2) increasing PCP speed for 1 h per day to clear the solids, as a preventative flush; (3) verification of solids issues in CSG wells in the Surat Basin; and (4) quantification of produced solids.