The plug-and-perf (PnP) method is widely used globally for multistage fracturing operations. With only a few jobs performed worldwide, coiled tubing (CT) assisted PnP operations in high-pressure/high-temperature (HP/HT) wells are largely uncharted and most challenging. The "A" field in India has HP/HT formations, with bottomhole temperature (BHT) of 310°F and reservoir pressure of 9,000 psi. Whereas the PnP method is widely used globally, there are few examples in wells with completion restrictions or whose downhole conditions dramatically increase depth inaccuracies and equipment damage. This study describes how to address challenges such as depth correlation (which affects plug-setting depth accuracy), low injectivity, completion restrictions, and heavy brines (which damage CT). To gain further understanding of operations, simulations are sensitized to identify solutions for pumping rates, HP/HT conditions, well kill fluid, milling, and cleanouts where obstructions hindered BHA penetration. The proposed best practices presented here are for primary CT operations involved in the complete PnP cycle, such as wellbore displacement, well dummy run-drift, setting the isolation plug and milling, acidizing using jetting tools, sand cleanout using gels having best performance in HP/HT environment and motor-mill runs with durable resistance in harsh environment, well kill (using 13.65-ppg calcium bromide), and nitrogen lift. The featured case studies describe operations including seven bridge plugs being set at accurate depths and milled after fracturing; cleanout of a 340-m sand column is also featured, as well as well kills with heavy brines. Optimized operational parameters such as CT speed, pumping rates, and the use of smaller outer diameter bottomhole assemblies doubled operational efficiency during those operations.

Coiled tubing (CT) was used to perform multistage fracturing treatments from the CT-tubing annulus in extended-reach wells of Aishwarya Field, Barmer, India. The wells were completed with chrome completion and included multiple fracturing sleeves. With peculiar challenges faced, solutions and lessons learnt are herein captured. In particular, casing deformation was observed in transverse wells, for which the workflow was developed so the wells with post-fracturing casing deformation could be completed and delivered for production. During the initial phase of the campaign. CT got stuck eight times after fracturing due to casing deformation. In three instances, the bottomhole assembly was left in the hole, and twice the CT was cut for recovery. After the workflow was implemented, no CT stuck incidents occurred due to casing deformation, and all 16 transverse wells in the campaign were delivered successfully. This study highlights the importance of differentiating between transverse and longitudinal wells while understanding their implications. In wells where casing deformation can occur, the workflow for CT-assisted multistage fracturing (MSF) operations must be adjusted. A smaller outside diameter (OD) shifting tool needs to be used without a packer assembly, and the CT cannot stay in the well during fracturing.

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.

Coiled tubing (CT) sand plug operations associated with multistage fracturing operations in high-pressure/high-temperature (HP/HT) wells are very challenging, in part because of the small number of such jobs that have been performed worldwide. The wells in "A" field in India have HP/HT formations, with a bottomhole temperature (BHT) of 310°F and a reservoir pressure of 9,000 psi. Although millable bridge plugs are preferred industry-wide, this case illustrates how sand plugs become a suitable alternate solution for multistage stimulation to address space limitations, equipment and completion restrictions, and small tubing sizes, even in challenging downhole conditions. This study provides solutions to operational challenges of low injectivity and completion restrictions, which preclude bullheading and use of conventional bridge plugs. Simulations were sensitized to identify the best solutions for sand settling time, HP/HT conditions, pumping rates, CT speeds, and cleanouts where calcite or scale deposits on sand hinder bottomhole assembly (BHA) penetration. Best practices are given for sand plug operations in challenging HP/HT environments; those best practices can be applied as a reference to design, prepare, and safely perform CT sand plug jobs in such conditions around the world. To address operational challenges in the cases presented here, the first three stages were bullheaded and the last two (a total 325-m sand plug) were placed using CT. Wireline was run to verify CT sand plug tag at ×200-m measured depth (MD). After the successful refracturing job, the 340-m sand plug was cleaned out, followed by acid spotting and squeeze using CT to rejuvenate the lowest zone. Strict application of the recommendations prevented the occurrence of operational contingencies, such as stuck CT, sand bridging, and settling of sand in surface equipment.

Executing interventions in wells encrusted with wax is challenging because experience with global coiled tubing (CT) dewaxing operations is limited, and equipment failure and stuck pipe risks are high. With few jobs performed worldwide, CT dewaxing (hot oil circulation with CT) operations are largely unexplored. The deviated wells in a field in northeast India pose several challenges including completely seized wellbore due to paraffin/asphaltene deposition, previous failed well cleanout attempts, very slow and low bottomhole assembly (BHA) penetration, pumping corrosive and flammable low wax crude (LWC) through CT, high chances of CT getting stuck, and pumping heated 69°C LWC through the CT. This case study delivers insights about design, safety, and operational considerations for 1.5-in. CT dewaxing and nitrogen lift operations in a subhydrostatic well in the field. The objective of this CT dewaxing and nitrogen kickoff operation was to clear the well of paraffin/asphaltene/wax to 1600 m and activate it with nitrogen, and this paper describes solutions for cleaning out and nitrogen-lifting wells with declining production due to paraffin and asphaltene deposition. One well is described in this case study, but this approach can be used perform CT intervention in similar wells. For this case, simulations were sensitized to identify the best combination of pumping rates, CT speeds, and fluid temperature to remove deposits hindering BHA penetration. This study proposes prevention measures using appropriate grounding and procedures, which determine if the crude oil can be pumped through CT. By use of this methodology, 581 dewaxing runs have been performed in 78 wells. Extensive on-job experience and lessons learnt by performing this operation over the last 3 years bring excellent results and prevent misruns. In many cases, production has been restored from nil; several examples feature a fivefold improvement of productivity thanks to this intervention method. Optimized operational parameters such as CT speed, pumping rates, and the use of smaller outer diameter BHAs doubled operational efficiency during those operations. In addition, strict application of the recommendations prevented the occurrence of operational problems such as stuck CT, crude oil flashing, sand bridging, and equipment failure.