Significant mud losses during drilling often compromises well integrity whenever sustainable annular pressure (SAP), is observed due to poor cement integrity around 9-5/8-in casing in wells requiring gas lift completion. Heavy Casing Design (HCD) is applied as a solution; whereby, two casing strings are used to isolate the aquifers and loss zones, thus ensuring improved cement integrity around the 9 5/8-in intermediate casing. Casing While Drilling (CWD) is a potential solution to mitigate mud losses and wellbore instability enabling an optimized alternative to HCD by ensuring well integrity is maintained while reducing well construction cost. This paper details the first 12 ¼-in × 9-5/8-in non-directional CWD trial accomplished in Abu Dhabi onshore The Non-Directional CWD Technology was tested in a vertical intermediate hole section of a modified heavy casing design (MHCD) aimed at reducing well construction cost over heavy casing design (HCD) as shown in the figure 1. A drillable alloy bit with an optimized polycrystalline diamond cutters (PDC) cutting structure was used to drill with casing through a multi-formation interval with varying hardness and mechanical properties. Drilling dynamics, hydraulics and casing centralization analysis were performed to evaluate the directional tendency of the drill string along with the optimum drilling parameters to address the losses scenario, hole cleaning, vibration, and maximum surface torque. The CWD operation was completed in a single run with zero quality, health, safety, and environment (HSE) events and minimum exposure of personal to manual handling of heavy tubulars. Exceptional cement bonding was observed around the 9 5/8 in casing indicative of good hole quality despite running a significant number of centralizers (with smaller diameter), compared with the conventional drilled wells (cement bond logging was done after the section). CWD implementation saved two days of rig operations time relative to the average of the offset wells with the same casing design. The rate of Penetration (ROP) was slightly lower than the conventional drilling ROP in this application. The cost savings are mainly attributed to the elimination of casing-running flat time and Non-Productive Time (NPT) associated with clearing tight spots, BHA pack-off, wiper trips. The application of CWD in the MHCD wells deliver an estimated saving of USD 0.8MM in well construction cost per well compared to the HCD well design. Additional performance optimization opportunities have been identified for implementation in future applications. The combination of the MHCD and CWD technology enhances cementing quality across heavy loss zones translating into improved well integrity. Implementing this technology on MHCD wells could potentially save up to USD 200MM (considering 250 wells drilled). This is the first application of the technology in Abu Dhabi and brings key learning for future enhancement of drilling efficiency. The CWD technology has potential to enhance the wellbore construction process, which are typically impacted by either circulation losses and wellbore instability issues or a combination of both, it can applied to most of the offshore and onshore fields in Abu Dhabi.

Loss of circulation while drilling the surface holes has become the main challenge in the Abu Dhabi Onshore developed fields. Typical consequences of losses are blind drilling and high instability of the wellbore that eventually led to hole collapse, drill string pack-offs and other associated well-integrity risks. Expensive operations including implementing aerated drilling technique, high water consumption and logistical constraints lead to difficulties reaching planned depth and running casing with added complexities of well integrity due to poor cement quality and bonding in the required isolation zones. Casing while drilling (CWD) is becoming a powerful method in mitigating both lost circulation as well as wellbore stability issues. This paper details the first 13 3/8″ × 16″ successful non-directional CWD trial accomplished in Abu Dhabi and the various advantages of the process. The Non-Directional CWD technology is used to drill vertical or tangent profiles with no directional drilling or logging (formation evaluation) requirements. The casing string is run with drillable body polycrystalline diamond cutters (PDC) bit and solid body centralizers are installed into the casing to achieve the required stand-off for cementing purpose. Some of the best practices applied to conventional drilling operations are not valid for CWD. The paper presents the methodology followed by the drilling engineers during the planning and preparation phases and presents a detailed description of the execution at the rig and the results of the evaluation including time savings, cement quality, rate of penetration, bottomhole assembly (BHA) directional tendency and losses comparison among others.The implementation of CWD saved the operator five days. The bit selection and fit-for-purpose bit design were critical factors for the success of the application. The interval was drilled (as planned) in one run through interbedded formations with a competitive rate of penetration (ROP). In this trial the interval consisted of 2,470ft with an average on-bottom ROP of 63.7 ft/hr, zero quality, health, safety and environmental (QHSE) incidents with enhanced safety for the rig crew.The technology eliminated the non-productive time (NPT) associated with tight spots, BHA pack-off, vibrations or stalls which it is an indication of good hole cleaning and optimum drilling parameters.Medium losses (10-15 BBL/hr) were cured due to the plastering and wellbore strengthening effect of CWD allowing drilling to resume with full returns.Well Verticality maintained with 0.3 degrees Inclination at section final depth.The drillable CWD bit was drilled out with a standard 12.25-in PDC bit in 1 hour as per the plan.

This paper will highlight the first level 2 Multi-lateral well in BAB Field with permanent limited entry liner completion in the lower borehole to enhance accessibility and production. The well presents a technical milestone to the company in the development of multiple reservoir by combining two (2) wells from different reservoir and produce from both by using same surface well construction. At initial stage, the economics related to the implementation of the multilateral approach were analysed. Calculation was done by comparing the cost related to the technology application against the cost to prepare one (1) location plus completing a well up to the 7″ liner and mobilizing the rig twice. Then, it was necessary to select the candidate wells to be drilled from the same slot where synergy between Study team and drilling team was in place in order to ensure proper target alignment to make feasible the drilling and completion operations at the same time that the production targets were fulfilled. This project confirmed the feasibility of multilateral well application in a very congested field in terms of wells construction and surface facilities. In order to achieve such goal full synergy must be in place to select proper wells candidates and align targets. Cost reduction is massive considering the elimination of three (3) well phases plus avoidance of one (1) location construction and also the elimination of 1 rig move represents a big impact in terms of economics. Furthermore, the impact in terms of the risk reduction must be considered By combining two (2) wells in one (1) and eliminating three (3) phases in the standard well construction the harmful impact of location preparation, drilling fluids and cuttings on the environment is reduced by 45%, especially with oil base mud system. Geological problems can be observed during drilling each phase of a new well. However, drilling multilateral wells will reduce this occurrence. Well was completed with 7″× 4-1/2″ top packer, 4-1/2″ Slotted tubing and seven (7) swellable packers in lower borehole as well as Dual upper completion with 7″ single retrievable and 9-5/8″ dual retrievable packer and 2-7/8″ and 3-1/2″ tubing combination in both short and long string. This paper presents ADNOC Onshore first and successful experience in the deployment of new acquired technology for the Drilling multi-lateral / dual completion systems in BAB Field. The screening criteria for selecting the system as well as the benefits realized and lessons learned from this experience are also discussed together with the design simulations required to ensure the success of the well construction.