The coiled tubing (CT) e-line system is ideal to perform real time production logging (PL) in long horizontal wells, however, the wireline cable inside the CT can restrict the pump rate while the large volumes of acid normally pumped could potentially damage the CT pipe's integrity. Furthermore, using two different CT strings, one for pumping acid and another for performing the PL in real time is neither practical nor economical. A common approach is to use a memory PL tool (PLT), with the associated drawback of recording poor quality data or eventual misruns.To overcome these challenges, a new CT multipurpose system has been developed, allowing real time PL and conventional applications. Leveraging on the telemetry offered by the fiber optic enabled CT (FOECT), already used for downhole measurements while treating in the M field; the new downhole assembly enables the use of standard PLTs in real time mode. At the surface, the converted optical signal is transmitted wirelessly to the PL engineer's portable computer; eliminating the need for conventional acquisition equipment and personnel.In a world first application, the system was used in a land water injection well, after the stimulation job; obtaining the injection profile log with the same quality measurements as a conventional wireline conveyed log. Moreover, the data demonstrated a uniform injection profile. Additional field applications are also briefly discussed in this paper.The new multipurpose FOECT reduces the mobilization and logistics otherwise required, as well as the time and cost compared to existing alternatives. This new capability can be extended to other scenarios like offshore or remote environments, where operational costs have a larger impact. Ultimately, the system opens the door for performing diagnosis, treatment and evaluation in a single well intervention mobilization; making CT operations more efficient and providing more data for production engineers.

Critical coiled tubing treatments, such as fill cleanouts of sub-hydrostatic wells and perforations of small reservoir intervals have historically posed a high uncertainty for Norwegian operators due to nature of the complex completions i.e. long and large monobore completions. The complexity is exacerbated with the strict offshore environmental regulations that limit the fluids that can be used for intervention operations. Fill cleanouts on these wells with CT face the difficult challenge of achieving the desired rate for pumping seawater which leads to the need for better understanding the downhole conditions while performing the operation. Without understanding these conditions it can be costly and create operational complications. A way to provide insight to the changing conditions during the cleanout operation is to use CT enabled with real time downhole measurements. The use of real time downhole measurement allows recognition of the wellbore response due to changes in hydrostatic pressure as the fill/debris are removed from the wellbore and adjustment of the operational parameters needed for effective treatment. Following the cleanout, this ability to adjust the parameters allows efficient well kick off by optimizing the use of nitrogen. This paper will present several case histories incorporating real time downhole measurements for effective and efficient clean outs as well as optimized well kick offs in the Norwegian sector of the North Sea. Introduction The Valhall field is an Upper Cretaceous, asymmetric, chalk anticline that forms an overpressured, undersaturated, oil reservoir located in the Norwegian sector of the North Sea. It is characterized by high porosity (25 to 48%) and high oil saturation (92 to 97%).1,2 Fill cleanouts are often necessary during the life of these wells as the unconsolidated nature of the reservoir and the compaction mechanism contribute to production of particles and fines which plug reservoir perforations and obstruct wellbore access. Cleanouts are also challenging in these wells due to the unpredictable nature of the fill to be found and the possible wellbore damage that can exist especially in old wells.2 Improved method for cleanouts It is generally accepted that many, if not all, coiled tubing downhole applications can be optimized with the availability of real-time downhole information. Many of the existing treatment simulators/monitors for these operations use calculated values for downhole parameters based on extrapolation from surface measurements - giving at best an approximate result. Realtime downhole measurements allow interpretation and job optimization with services delivered through coiled tubing. It provides the information needed to adjust job parameters immediately, to improve effectiveness, reduce risks, and optimize performance with the operation still in progress.

This paper shares the best practices for performing coiled tubing (CT) operations in high-temperature geothermal wells with major challenges such as live well challenges, scaling of pumping fluid, high surface temperatures causing damage to wellhead stack, and CT tag issues. Some geothermal wells have very high bottomhole temperature (BHT) of 550 to 600 °F and surface temperature of 350 to 400 °F, which possess many service quality and health, safety, and the environment risks. With limited CT geothermal interventions as compared to conventional operations, performing live well CT interventions can be highly risky. Because commonly available pressure control equipment (PCE) seal material is rated to 250°F, the biggest risk is damage to the surface CT equipment, which may result in a well control situation. Generally, the lead time is high, and it is expensive to use temperature seal material rated more than 250°F. A generalized design methodology was developed to check the CT job feasibility in a high-temperature geothermal well. To gain further understanding on the same, three cooling loop designs are compared in this study. Then, the best solution was simulated, implemented, and verified on some wells of "X" field. This design proved to be effective operationally and has reduced the risks for steam inflow into the PCE. For the case of scaling caused by pumping fluids at high temperatures, this was identified while performing CT operations in geothermal wells of X field. The scale deposited on the CT along with pumping fluid was sent for laboratory hardness and solubility analysis. The results were compared, and lessons learnt to prevent any scaling are discussed. Most of the geothermal wells are completed with a large-diameter completion (7-in., 9.625-in., and higher), which has a bigger flow area to accommodate high steam inflow. Using even a 2.875-in. CT in these wells presents issues of CT tagging at the completion-liner interface, lower annular velocities, and lifting capacity, among others. The best practices were developed on the job to identify the most efficient bottomhole assembly (BHA) design, reducing the probability of CT getting tagged at these depths.

The wells in the "A" geothermal field located in the Philippines, have high bottomhole temperature (BHT) of 600°F and bottomhole flowing pressure (BHFP) of 2,000 psi. The productive section in this field has "shallow" and "deep" reservoirs which are separated by a low-permeability formation. The interaction between the reservoirs is hence limited except through the wells resulting in intrazonal flows under shut-in conditions. As observed with time, these flows have been upflows making the overall production very stable. However, in recent years, it has been found that the cooler fluid inflow from the shallow reservoir has relatively increased, causing reduction in production levels. Under flowing conditions, this has resulted in both flow instability and downflows in wells, which in turn have decreased the individual well production capacity. In order to activate and enhance well production, coiled tubing (CT) nitrogen lift operations were required to be performed to unload the cold water in geothermal wells, hence enhancing steam production. The wells in this field are completed with large completion sizes (7-in., 9.625-in., and 13.375-in.) and have high BHT (600°F), which makes conventional coiled tubing operations highly challenging. Because the coiled tubing operations in geothermal wells are limited as compared to the conventional operations, planning and executing these for the first time in the "A" field was challenging operationally and technically. As such, surface equipment failure risk was high, putting at risk successful coiled tubing operations. To gain further understanding of operations in high temperature and cold water downflow environments, CT simulations were combined with simulations from the geothermal reservoir to overcome modeling limitations. The outcome helped designing a new cooling loop system and allowed optimizing the nitrogen lift technique. As a result, two large-diameter geothermal wells were lifted safely with 2-in. coiled tubing in the Philippines.