Drilling extended reach drilling (ERD) wells starting from the planning phase and engaging various disciplines including drilling, cementing, drilling fluids and geoscience teams. The pre-well engagement and integration between multiple disciplines are vital to define the associated drilling/geosteering challenges and accordingly optimize the drilling program to deliver a successful ERD well. These challenges are included and not limited to geological model uncertainties, differential sticking, high torque and drag, ECD limitation, friction factors and expected mud losses. An integrated and optimized plan was constructed to meet the associated challenges. The drilling engineering team optimized the bottom hole assembly (BHA) design in all sections to ensure a smooth profile using optimum drill bits designs. The BHA included LWD technologies to mitigate the geological challenges and helping in determining the casing points and geosteering operations. A new generation of intelligent fully rotating high dogleg pushthe-bit rotary steerable system was selected with matched drilling bits to geosteer the well in the thin target layer while maintaining the planned target trajectory with minimum borehole tortuosity by means of realtime drilling optimization. Effective collaboration led to successful delivery of the first extended reach well, the geosteering objectives were achieved with 100% reservoir contact and delivered 20,000 feet targeting thin carbonate layer and overcoming the complex geology environment. The well was drilled to record depth of 32,300 feet with 29% ROP improvement in same field. ECD was always maintained below the fracture gradient along with optimal hole cleaning without cuttings buildup or tight hole while reducing the wellbore friction to ensure smooth pulling out of hole operation. Cementing operations were successfully achieved and ensured zonal isolation. Furthermore, a customized and innovative drilling fluid with free RDF Non Aqueous Fluid (NAF) and compatible lubricant were deployed along the different hole sections to reduce the expected induced losses and provide proper hole cleaning. The cementing program has been optimized for the 18 5/8", 13 3/8" and 9 5/8" casings using an innovative flexible expandable lead and tail slurries with enhanced mechanical properties to mitigate the expected losses while cementing and ensure proper isolation across all formations. The best practice of the multidisciplinary approach along with the captured lessons learned opens the door to drill more challenging wells. in addition, it proved that proper planning and execution can shift the boundaries further and gave confidence to drill even deeper.
The conventional drilling fluid to drill the high-temperature wells are non-aqueous fluid. ADNOC used high-temperature water-based drilling fluid instead of nonaqueous fluid to drill the well successfully. High-temperature water-based drilling-fluid systems hold several advantages over non-aqueous systems from financial and environmental viewpoints. However, most conventional water-based systems start to become unstable at temperatures above 300 degF. This paper details the design and implementation of specially designed water-based drilling fluids based on custom-made branched synthetic polymer that meet these temperature stability requirements. The branched synthetic polymer exhibits superior rheological properties and fluid loss control, as well as longterm stability above 400 degF. Under static conditions, the high-temperature fluid shows no gelation, resulting in lower swab surge pressures while the stability of the highly branched synthetic polymer and enhanced rheological profile minimize sag. ADNOC required a cost-effective drilling-fluid system that remains stable under static temperatures expected to exceed 375 degF. The longterm stability of the system was critical for successful wireline logging operations. In addition, the system was required to provide shale inhibition, hydrogen sulfide (H2S) suppression and enough density to maintain well integrity while drilling through anticipated high-pressure zones. The challenging intermediate and reservoir sections were drilled and evaluated using high temperature water-based system. This paper will discuss the successful execution of high temperature water-based system in one of high-temperature well in ADNOC field.
The objective of this paper is to demonstrate the challenges, solutions and results of performing offshore Drilling Waste Management operations in a highly environmentally sensitive marine environment and UNESCO World Biosphere Reserve in offshore Abu Dhabi. The solution was to treat all drilling waste at source. This required both NOV Thermal Treatment Technology and NOV Cuttings Re-Injection Technology and became the World's first single-source operation for this equipment. The equipment was shipped to the island, installed and operated in parallel with the Operator's drilling programme. The drilling waste (Oil-Based Mud) was handled and stored by EMDAD then processed through the NOV Thermal treatment unit, which generated three separate treated waste streams - oil, water and solids. The recovered oil and water were reused on-site, whilst the treated solids were slurrified and fed to the NOV Cuttings Re-Injection system (CRI), which injected the solids into a disposal well. This paper will also demonstrate the results of the integrated operation.
Objectives/Scope Deepest Deviated Appraisal well in Upper Khuff reservoir in a small artificial island, located about 100 KM away from Abu Dhabi shore was successfully drilled and tested. The well has been recognized as the deepest deviated well on offshore Island with highest bottom hole reservoir temperature in UAE about 375 deg F (190 degrees C) and exceeding 9000 psi reservoir pressure complemented with impurities of H2S ranging from 10-22% and CO2 between 9-20%. Methods, Procedures, Process The challenges were immense, from designing to execution, including securing special materials for the unique well design to accommodate the sour environment of Khuff reservoir as exploring new reservoirs always counter many risks comparing to developed reservoirs. The execution was driven with the focus of maximizing the ultimate value and benefit for ADNOC, our respected partners, the community and the UAE. The field is located in the most sensitive and ecological important area and is under UNESCO Biosphere reserve. Results, Observations, Conclusions The appraisal well was successfully drilled to Khuff reservoir at a depth of 19000 ft. The well test using Drill stem test (DST string) was conducted. Multiple challenges ranging from HSE, material selection, drilling and logging tools availability, limitations and procuring them in time were overcome by utilizing the World First Integrated Zero Waste Discharge Solution in Restricted & Highly Environmentally Sensitive Areas. Another major challenge faced during the drilling deeper reservoir was mud rheology changes due to high temperatures. The logging program was tailored to overcome the challenges posed by the mud, high temperature, high pressure, sour condition and to gain maximum representative reservoir data in a reservoir where high-pressure steaks and geological unconformities were anticipated. The Drill stem test, (DST) string was successfully POOH after acquiring all the objectives from Khuff K-4 testing under above mentioned harsh environment. The zonal isolation was carried out with cement and rig was released. Novel/Additive Information The drilling and testing operation was conducted with high level of cooperation and excellence accomplishing the well set objectives without (Lost Time Injury). Lessons learned are widely shared with all the teams across the region to expedite and improve on the technologies used for sour gas production. ADNOC Onshore demonstrated 100% HSE, full commitment, high collaboration and efficient outcome ensuring safety compliance for the successful delivery of this highly critical project. This paper presents the various challenges faced and overcome while carrying out the Drilling and testing of the HPHT Sour well offshore.
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