This paper describes the evolution of descaling interventions via coiled tubing (CT) performed in Saudi Arabia gas wells in the Ghawar field. Throughout these operations, the introduction of new technologies and improved surface equipment has significantly enhanced the efficiency and effectiveness. CT is the preferred choice for descaling interventions in wells whose reservoirs are underpressured/ depleted because it can accurately place fluid and deploy mechanical tools at the specific depths where scales are present. High leakoff into the formation and hydrogen sulfide (H2S) released at the surface are two main challenges that occur in this well type. Therefore, it is paramount to continuously monitor and control both downhole and surface parameters. The aforementioned challenges can be addressed by optimizing real-time fluid placement or by manipulating the choke size, among other parameters. A chemical plug can be pumped to isolate the reservoir before commencing descaling interventions, but this process may require stimulation or re-perforation of the reservoir system after the treatment. Therefore, it is preferable to use a system that is flexible enough to execute a wide range of operations, from reservoir isolation to descaling treatment, while maintaining the well in balanced or marginally overbalanced conditions. Previously, CT descaling operations were executed relying only on surface parameters. Today, new technologies are available that can provide live downhole parameters such as pressure, temperature, load, and torque, and these technologies have advanced descaling interventions. Although downhole parameters via downhole tools have been available for years, tools providing such parameters were limited with respect to pumping rate, working pressures, temperature, and ability to sustain high torque and vibration. To address these issues, a new tool was developed that can acquire downhole parameters during milling and clean out operations. The ability to monitor downhole parameters enables field personnel to act instantly to any change in downhole conditions. At the same time, introduction of advanced surface equipment has helped in better handling of returns from the well and in maintaining a constant wellhead pressure irrespective of dynamic returns. Therfore, the treatment is executed within its defined limits and risks of service quality events are mitigated. This paper describes the evolution of CT descaling intervention treatments and the technologies used. It details how the introduction and integration of new technologies have enhanced descaling operations in Saudi Arabia where real-time decisions were made to optimize treatment, make the operation safer, and prevent formation damage.

This paper will discuss the coiled tubing (CT) fiber optic real-time telemetry system evolution for varied interventions performed in Saudi Arabia’s Ghawar field. The paper will show the benefits achieved with consistent improvement of the CT fiber optic real-time telemetry system, leading to better understanding of intervention and reservoir in real-time, optimization of treatment, opening new horizons and meeting huge successes. For years CT with fiber optic real-time telemetry, has been used in Saudi Arabia Ghawar field, whereas the initial version of the CT fiber optic real-time telemetry system consisted of 2-1/8 in BHA, comprising measurements of pressure, temperature, casing collar locator, gamma ray, tension and compression and distributed temperature sensing. Though the successes achieved from this system were remarkable, it was restricted to 2-bpm, had temperature limitations, and was not able to bear shocks and vibrations. As the time passed, interventions became more chanllenging. In order to meet well intervention objectives, a new tool was developed enabling higher pumping rates up to 8-bpm, and working temperatures of 300 °F. The challenge of bearing high shocks and vibrations was still not met, so a new was further designed to meet that objective. In the field, the new tool proved to be the most superior and advanced one, as the CT fiber optic real-time telemetry system gave high pump rates of 8-bpm, worked at temperatures of 350 °F, has a higher pressure rating, and was used in interventions where high shocks and vibrations were encountered. In addition to the above-mentioned CT fiber optic real-time telemetry system evolution, the system was enable to run the logging tools, leading to the development of a CT dedicated downhole flow measurement tool. These new tools provided the following advantages: optimize the treatment stages during a particular intervention, help operators gain a better understanding of the well and reservoir response during an intervention, assist in optimization of treatment strategy, and enable pre and post-treatment evaluation in minimum CT runs. This paper will explain the evolution of the CT fiber optic real-time telemetry system, and the significant impact the system has made to the oil and gas industry. The system enables CT interventions in a concise manner where decisions during a treatment are made using both surface and downhole parameters.