In an offshore mature asset workover jobs involve high cost and operational risk that impact on the profitability of the projects. Non-rig interventions are a more sustainable approach to effectively sustain production. The fact that some reservoirs are depleted while many are water flushed often result in modest incremental gains. Due to the age of the asset, several wells present mechanical issues which make any intervention more challenging. The non-rig methodology has proven to be well-suited to these conditions.

This paper will describe the criteria and technology used to mitigate the production decline of the TSP (Teak, Samaan & Poui) asset located off the south-east coast of Trinidad. TSP is a mature oil field which has been producing for almost 40 years. The main constraints for flow assurance are sand production, scale and paraffin deposition, high IGLR, skin damage, high water cut, depleted reservoir and mechanical problems. A variety of non-rig interventions have been employed since 2006 in order to mitigate the mentioned constraints and therefore maximize production from the field. These interventions include tubing and formation acid/de-wax jobs, gas lift valve changeout, addition of new perforations, tubing punch, sand clean out, thru-tubing gravel pack and other jobs aimed to acquire information such as pressure surveys and cement, production, reservoir saturation and multi finger logs. These jobs, together with regular gas lift optimization exercises and re-activation of previously shut-in wells, have proven to be quite effective at slowing the natural production decline.

An annual technical and operational screening of all wells (active and shut-in) is performed and the under-performing wells are identified and targeted for the non-rig campaign and reactivation. In addition to that, multi-rate tests are carried out throughout the field prioritizing those critical wells. This ensures that the injection gas rates are at their optimal values, maximizing the oil rates and saving injection gas volumes.

The non-rig, well re-activation and GLO campaigns have maintained the annual production decline of the TSP field between 8 to 12% while facing operational and reservoir issues inherent in an aging field.

You can access this article if you purchase or spend a download.