Case Study: Successful Application of Coiled Tubing With Real-Time Data Communication System for Selective Reservoir Treatments Using Straddle Packer Assemblies

Abstract

Abstract Two gas wells in Germany showed a decline in production and wellhead pressures and were selected for acid treatments for skin removal. PLT measurements showed that certain reservoir intervals were not contributing to the gas production. To optimise treatment of individual zones a coiled tubing intervention with a resettable straddle packer assembly was chosen. Due to the depth-critical nature of straddle packer interventions, the use of an accurate depth correlation system was required. Straddle packer well interventions were performed with real-time data communication, using a mono-conductor cable inside the coiled tubing. The robust data communication system provides real-time information from a Casing Collar Locator (CCL), down-hole pressure and temperature gauges and is suitable for use during acid treatments due to a protective jacket around the cable. Information provided by the CCL tool ensures depth correlations, whereas differential pressure measurements from the down-hole pressure gauges provide positive information about the setting and sealing conditions of the inflatable packer system. The combination of the down-hole real-time temperature and pressure readings allow full control during the injection process to avoid re-fracturing during acidizing. Furthermore, down-hole temperature readings can be useful for optimizing the corrosion inhibitor loading in acid recipes. In this paper the real-time data communication system and the benefits in combination with straddle packers are discussed. Case histories in Germany illustrate the preparations, the execution and the lessons learned from selective treatment interventions with coiled tubing and real-time data communication in two gas wells. After the treatments the production of the wells was increased by more than 10% in each well. The real-time in situ pressures and temperatures were a valuable input to the reservoir engineering model and further action will be based on the results. With the use of the resettable straddle packer several zones were treated in one run resulting in reduced operating time and thus a minimum in lost production.