State of the art technology has been incorporated into the Seria North Flank waterflood development. Both producer and water injector wells are completed with interval control valves, distributed temperature sensing (DTS) and downhole gauges. DTS has been commercially available for more than a decade, however only recently it has been employed in the oil industry. Interpretation of the data has been difficult and therefore its value questioned.
This paper presents an original technique of monitoring wax build up through the use of the DTS data. PVT analysis from the appraisal well showed significant wax content in some of the reservoirs to be produced. The critical wax deposition temperature is higher than the surface temperature and therefore wax is expected to be deposited inside the tubing. The DTS provided temperature trends that showed temperature decline in a section of the tubing string; caused by the additional layer of wax between the crude oil and the gas filled annulus. The paraffin layer has its own heat transfer coefficient therefore thickness can be estimated from temperature data for unchanged flow rate and fluid composition.
Using the temperature trends, the Well and Reservoir Management (WRM) team was able to determine the exact depths where the wax accumulated. This information avoided slick line interventions to determine hold-up depths and also allowed the required volume of solvents to be calculated, prior to for coiled tubing clean out. The Coiled Tubing activity enabled production to be maintained before the wax build-up could significantly impact the well flowrate. This technique has been extended to other wells and is now part of the standard WRM monitoring parameters for this field.