The trial of a turbine powered Motorized Reaming Shoe (MRS) was conducted on two fields offshore Abu Dhabi involving the running of 9-5/8″ casing to planned depths in long intermediate sections. The trials involved running casing in the longest12-1/4″ sections to date on each field. This paper will elaborate on detailed parameters, Motorized Reaming Shoe features and operating practices recorded while reaming through multiple restrictions with a cumulative length of more than 200 ft, across various formations, successfully running casing to the planned depth. It will also elaborate on casing cementing and shoe-track drilling operations where MRS were deployed. Referring to the average NPT duration of similar incidents, this initiative has saved 6 to 7 days of operation (eliminating requirement to pull the casing, perform a wiper trip, and re-run back the casing). This is estimated at an average of approximately 1M$ cost savings per NPT event. The failure to run casing to section TD with the MRS in one of the trial jobs is also analyzed including detailed operational learnings and design changes that could positively impact running long casing strings in complex wells. This paper details the technical features and potential benefits of Turbine Powered Reaming Systems, how the trials were conducted and their impact on de-risking casing deployments, with specific reference to application in long intermediate casing sections offshore Abu Dhabi.

Drilling through fractured gas bearing formations to access the oil reserves underneath has been one of the most challenging tasks for the drilling Team due to the embedded risks such as; total circulation losses, Gas migration, well control issues, hole instability, cutting beds accumulation and stuck pipe. This paper explains an approach in drilling fractured gas bearing formations that was performed for the first time in offshore Abu Dhabi field-A, Pressurized Mud Cap Drilling (PMCD). Drilling through fractured Gas bearing formation causes the loss of the mud column and the consequent intrusion of hydrocarbon gas to the wellbore, thus initiating well control response, which adds to the flat time and might cause cutting slippage, stuck pipe and eventually loss of well objective. PMCD is best suited to deal with such situation, as it allows drilling to continue under the mentioned circumstances by filling the well with sacrificial fluid while the well is closed, fractures take seawater, cuttings and the formations pressure lefts the underbalanced annular fluid to reduce losses volume. Two wells were drilled successfully using the PMCD technique in Field A where the anticipated fracture gas bearing formations system was encountered shortly below the 9-5/8″ casing shoe. The performance increased substantially in the second well as lessons learnt were implemented to avoid any time loss. Drilling the 8-1/2″ Hole section started in well #2 conventionally with required 200 psi overbalance mud weight, the drilling fluid system is directly changed to sacrificial fluid (Sea water) once the fracture system is hit and total losses observed. A light Annular mud (Seawater) is pumped in the well's annulus. After having stable PMCD parameters, drilling continued at an ROP of 100-150 FPH. TQ & Drag real-time monitoring & intermittent pumping of 3 × 50 bbls weighted HVP to clean bit & BHA from cuttings were essential to avoid getting the pipe mechanically stuck. The 6,710 ft section was drilled successfully, Striped BHA Out of hole, Ran 7,160 ft of 7″ Liner, perform cement Job & achieved isolation. Comparing with offset wells drilling conventionally in field-A through the gas bearing fractured zone, PMCD saved +/− 44 days of the well time, cost and achieved the target. and greatly improved the operational safety by providing closed-loop drilling. The PMCD application on the two wells is the first of its type in offshore Abu Dhabi, it allowed accessing parts of the reservoir that have been inaccessible due to the fracture system. Additionally, it increased safety of operation & saved rig days that would have been spent in treating losses and well control operation. Pressurized Mud Cap Drilling application in field-A provides a solution for a wider implementation in developing fractured gas cap resources in future.

The development of carbonate reservoirs of a giant field, Offshore Abu Dhabi, requires long horizontal wells to maximize productivity, but at the risk of unwanted gas and water channeling through its inherent heterogeneities. Conformance can be enhanced with dedicated segmented completions (blank sections, Inflow Control Device, Autonomous Inflow Control Device, etc.) or selective acid stimulation (diverter, Limited Entry Liner), which are increasingly implemented to extend well life, and eventually well value. If these technologies have matured, success depends heavily on the quality of the formation knowledge prior to completion. As of today, conventional logs provide the basic ground, but they lack dynamic information, whereas production logging results are obtained too late, when the well is already completed. Initially introduced for the optimization of unconventional well completions (see Jacques et al, URTEC 2019), the Well Testing Logging (WTLog) offers the advantage to record a log of mobility, at the end of drilling the openhole, enabling a favorable timing to influence adapted completion and stimulation design. Contrasted viscosity brines are sequentially circulated through the drill pipes at a constant rate and back-produced from the casing at constant pressure. The fluids interface travels in the drain from the TD to the casing shoe, and the measurement of the differential formation seepage is interpreted into an injectivity profile. Combined with rate fall-off phase analysis, permeability and skin logs are derived. Lasting a few hours and realized with conventional rig equipment (such as cement pumps, coriolis flowmeters, Managed Pressure Drilling system), it is a nonintrusive, safe, and ultimately low-cost operation. Forward, it can replace costly logging, when aimed at characterizing heterogeneities. Within a year, the two first WTLog pilots of the Middle East were successfully designed and carried out. They targeted two appraisal wells in distinct undeveloped reservoirs (Cretaceous and Upper Jurassic formations) which benefited from rich acquisition programs (Image log, Production log) to benchmark and qualify this technology. After an explanation of the technology principles, this paper describes the design, operations, and results of these pilots. It then focuses on the petrophysical consolidation of the matrix/fracture characterization. It concludes by sharing the learnings and offers insight to what extent it is a promising technology to be applied in Middle East carbonate reservoir developments.