This paper presents a case of study of cementing operations in extended reach drilling (ERD) wells on two artificial islands in UAE. The cementing objectives involved covering and isolating the shallower oil or water-bearing zone, sealing any potential crossflow interval between various reservoirs, and mitigating communication between the 13 3/8-in × 16-in. and 9 5/8-in × 12 ¼-in. annulus. Additionally, the cement will become a secondary barrier planned for the 9 5/8-in. casing to prevent potential exposure of the 13 3/8-in. casing in the event of injection gas percolation. For this case was necessary to design the cement with the necessary mechanical properties to extend the well life expectancy. To accomplish the operation objectives, the formations, well design complexity, and possible complications were considered. Understanding these factors facilitated the improvement in the approach and design to obtain better cementing operations results. To achieve all of the targets, various enhancements were implemented systematically over time, which included adding fiber in the cement spacer to mechanically enhance mud removal, adding corrosion inhibitor and bactericide to protect the casing if fluid remained in the well. Various lead cement slurries were designed with tailored rheology to remain within the established narrow margin between the pore pressure and fracture gradient. A flexible and expandable tail cement slurry system was implemented to increase the likelihood of proper isolation. The expansion of the tail cement slurry after the cement sets and the tailored mechanical properties used to achieve the necessary resilience, provide support for the stresses encountered during the life of the well. Upgraded properties, such as fluid loss, reduced permeability, and static gel strength (SGS) development, were used to mitigate possible influx between formations. Both cement slurries were loaded with resilient fiber to enhance the cement ductility. These strategies combined with software simulations enabled equivalent circulating density (ECD) management, contamination avoidance, friction pressure hierarchy, discernment of the top of cement (TOC), determination of possible channels, and appropriate stand-off design. The application of the solutions combined with outstanding consistent field operational performance enabled the following: Fine-tuning various practices, improving isolation across critical zones, achieving the planned TOC, sealing the formations that could create potential future issues, and reducing the probability of interzonal communication or crossflow. A systematic approach was necessary to achieve all the objectives in these challenging wells and determine which practices and technologies provide the appropriate results. Cementing ERD wells with the challenges previously described is not a standard industry practice. This case study presents the staged application of the enhancements that improved the cementing results. These were inferred by evaluating the operational parameters (density, pumping rate, pressure, volumes, and surface returns) in conjunction with the availability of cement logs (CBL, VDL, ULTRASONIC). The results demonstrated the capability to achieve isolation; Furthermore, the continuous annulus surveillance showed no undesirable sustained casing pressure.

This paper describes how the unique centralizer requirements for extended reach drilling (ERD) wells can be attained. By continuously evaluating past casing runs in combination with engineering input, the learning curve led from a standard centralizer to a highly customized solution. The necessary flow path target to enhance the wellbore isolation through cement placement is met by achieving the right centralizer performance and placing. A single-piece high-restoring-force centralizer is the best solution for the high inclination well profile to obtain the required 9 5/8-in. casing stand-off for ERD wells. The original centralizer design experienced challenges such as high doglegs in some of the longest 9 5/8-in. casing strings that have been run in the UAE to date. Customize the centralizers for different well profiles was necessary. They were developed and tested according to the latest API 10D (2001) specifications using precision equipment to ensure reliable test results that enable accurate hook load and stand-off simulation. Initially, a standard off-the-shelf design of a 9 5/8-in. x 12 1/4-in. single-piece centralizer was used in two wells with the following results:Friction factor exceeded the expected values across the interval on occasion.Total Depth (TD) was sucessfully reached by washing down to bottom.Good centralization as per software design was attained (tageting 80%) with moderate to good isolation. Due to the performance, while running in the hole (RIH), concerns arose due to the unexpectedly high friction factor which, could lead to difficulties RIH and reaching TD in future wells. The modified centralizer design has led to the following improvements:Reduction of friction factor to an average of 0.24 due to a significant decrease in the centralizer running force even through reduced hole diameter intervals and the high dogleg severities (DLS)Reaching TD successfully.Stand-off remained around 80%, as demonstrated by outstanding cement bond log results across the critical sections. It is important to consider that this centralizer was designed not to lose any performance after being run through reduced hole diameter intervals. The application of enhanced centralization design (i.e., standoff >80%) ensured good quality of the cement job.