Gravel Pack Maintenance and Stimulation by Air Lifting

Abstract

This paper presents a case study on reducing pressure build-up in some injection wells in a geothermal heat plant in Sweden. The plant has been in operation for 25 years. Four production wells are used and after heat extraction the geothermal water is re-injected in 5 wells approximately 2 km from the production area. In the injection wells there is a build-up of injection pressure over time and the wells needs a regularly maintenance to reduce the pressure. This is performed by a regular reversal of the flow direction in the gravel and screen section of the wells. The water production during the stimulation is carried out by airlifting.

From the start of the plant in 1984, recordings of production and injection parameters such as pressure, temperature and flow rate has been done daily. Over the years geophysical logging has also been performed in both production and injection wells. Parameters that have been studied are for instance temperature and flow profile along the screen sections etc.

The pressure reduction by stimulating the gravel pack is recorded and the results are also shown by flowmeter logging before and after stimulation.