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.
Rotary Steerable System (RSS) has been used for quite some time in the industry and in UAE onshore fields. But as the wells become increasingly more complex operators are forced to look into upgraded technologies to expand the envelope beyond the known limits, often implying more complex and costly bottom hole assembly (BHA). At the same time the current oil price situation make it extremely difficult for operators to justify any increment of Authority for Expenditure (AFE) or to take the risk of experimenting new solutions that could potentially increase non-productive-time (NPT), even if for just limited period until the learning curve is established. This case study demonstrates that adopting both fit for purpose technology and invisible lost time (ILT) reduction strategy can yield tremendous performance improvement delivering wells ahead of AFE. A preliminary field analysis carried as first thing to understand the field drilling challenges and performance limiters highlighted that both on bottom (rate of penetration, ROP) and off bottom time (connection time, wiper trips, circulation time, tripping time, etc.) presented areas for improvement. Throughout the life cycle phases of field development more complex reservoirs have been targeted for example thinner layers, multi-structural drain sections, extended laterals, etc. The demand of an RSS being able to drill smoother wellbore minimizing tortuosity and enabling longer sections and trouble-free tripping had gradually changed from being a "nice to have" feature to be a necessity not only to eliminate time waste but also to prevent costly stuck pipe events. The new high performance RSS (HP-RSS) and its enhanced software for trajectory control enabled a faster on bottom ROP by minimizing the need of directional driller intervention to correct the trajectory hence maximizing on bottom time. The enhanced directional control translated into smoother wellbores resulting in reduced friction factors and torque and drag which eliminated the need of wiper trips and decreased tripping and connection times. In parallel with this also drilling and connection procedure were revised, utilizing torque and drag real time monitoring to optimize connection time. The expanded envelope of HP-RSS also enabled further improvement of hydraulics for effective hole cleaning while drilling minimizing the hole conditioning time on connection. The advantage of having superior quality wellbore extended also to post drilling phases, for example it enabled a faster and trouble-free running of complex smart completion reducing HSE risks and further impacting AFE. In summary, the HP-RSS enabled superior performance saving $287.5K for an invidual well. The total amount of saving projected over a year in this field is estimated to be around $ 2.9M. Efficiency and reliability are keys to lower costs and increase profitability in oil and gas operations. This paper introduces a novel approach that aim to expand technical confidence to drilling and reservoir management to target more challenging drains sections with higher productivity.
Due to the declining reservoir pressures in some of its onshore gas carbonate fields, ADNOC decided upon an initial 3 well UBCTD, (Underbalanced Coil Tubing Drilling), campaign in its onshore Asab and Bab fields, with 2 wells to be drilled in Asab and 1 in Bab. Both target fields have high H2S concentrations up to 6% and ADNOC undertook the necessary candidate selection process, Basis of Design, and equipment selection to enable them to drill these wells using UBCTD techniques. Due to the high H2S content, it was required that a closed loop system design was implemented, which was the 1st successful one implemented in the Middle East. The project's given objectives were analyzed, and the planning was conducted considering the different aspects to achieve ADNOC's objectives and expectations. Several challenges were faced during the designing phase which had to be resolved prior the operations start-up. These challenges included extended drilling reach, closed loop returns handling system, handling high H2S levels at surface amongst others. One of the main design objectives, the drilling reach, was improved by optimizing the trajectories Dog Leg Severity, (DLS), and Bottom Hole Assembly, (BHA), configuration. Instead of a conventional mud motor, a turbine was used to give power to the bit and allowed having a lower Weight on Bit, (WOB), to drill the formation, thereby increasing the depth of the section. The trajectory was planned in a way to maximize the reservoir contact within the production layers and reduce footage in the non-productive zones between the producing formations, therefore maximizing the well productivity. Increasing the well production was key to the project economics and to prove the value brought by the UBCTD to ADNOC's hydrocarbons production. Several business disciplines collaborated closely under the IWC, (Integrated Well Construction), stewardship to provide practical solutions and design a system specifically tailored to achieve the objectives and overcome the various challenges associated with this project. The final solution was a closed loop system capable of:removing solids/drilled cuttings from the system.measuring flow rates of different fluid phases (gas, condensate & water).treating and removing H2S.exporting gas and condensate to ADNOC's production facility.whilst drilling the well in Underbalanced conditions. After the operations start-up on the 1st well, the returns handling system was modified to improve the efficiency and enhance the safety of the personnel and equipment. This paper will discuss the design and planning involved in the successful drilling of these three wells and the operational challenges and mitigations encountered while drilling.
The understanding of salt beds has been significantly improved over the years; however, certain operational challenges still persist. Conditions encountered during drilling salt formations may lead to stuck Logging While Drilling (LWD) and or wireline tools, which, at times, can contain radioactive sources. As data gathering remains a primary requirement in exploration wells, cost optimization, beside risk mitigation, is a further challenge in today’s economic landscape. A holistic approach is proposed to address these main objectives. The conventional procedure required drilling and formation evaluation (LWD and or wireline) in the section above the interbedded salt formation, followed by rotary steerable (RSS) only in the interbedded salt formation sections of the well. Considering the shallow depths of the well and the proximity to the aquifers, the threat posed by losing radioactive sources in the well is significant, therefore, formation density and neutron porosity logging operation is often compromised due the inherent risk. Logging While Tripping, a method in which tools record open hole data from inside the pipe, resolves this compromise, as the risk of lost in hole (LIH) is virtually eliminated. The empty LWT collars are run in the last bit trip or reamer run, as they do not affect the drilling operation. Once the well’s total depth is reached, the LWT logging tools are pumped from surface, safely inside of the pipe, and data is acquired while tripping the drill pipe out of the well. If the situation is evaluated as risky, drilling operation may continue without data acquisition. In case the logging tools already were deployed, they can be retrieved at any time by wireline or slickline. Prior to the introduction of the LWT in the drilling/data acquisition procedure, only gamma ray - sonic data was acquired over the challenging formation sections. Compressional and shear data may be important to improve modelling accuracy; however, they may be negatively affected by various factors such as drilling noise, mud properties, washouts and gas in the formation, particularly reservoir rocks interbedded with thick salt beds. When compared to the Neutron-Density porosity, sonic porosity is noticeably inferior, showing limited formation signature. Neutron-Density porosity correlates well with core data.
During a tubing depressurizing operation in a sour gas producer, the Sub-Surface Safety Valve dislodged from the nipple profile, broke and stuck inside the tubing hanger, restricting accessibility to the well. Multiple attempts to recover the stuck fish via slick line in combination with a permanent magnet resulted in recovering a few broken pieces and revealed a limited clearance of 1.85" through the fish. The well was killed and attempts to secure the well by installing through tubing inflatable bridge plugs using coil tubing were unsuccessful. It was then decided to exclude the coiled tubing operation for well integrity purposes due to limited clearance as the coil tubing had to pass through broken fish and could get stuck compromising the X-tree valves operation and it was decided to carry out work over operation to recover the broken fish. The cost for well work over was estimated at $ 3.0 MM. An innovative approach to secure this gas well riglessly using through Inflatable bridge plugs setting with electric line was introduced and the job was conducted successfully after completing all the risk assessments saving the significant costs associated with rig intervention. Two 1-11/16" through tubing inflatable retrievable bridge plugs (TTIRBP) were set with electric line passing thru the limited access hole of the broken fish. Plugs were set inside 4-1/2" and 3-1/2" tubing and pressure tested to 3000 PSI. The well was secured and the fish was successfully retrieved. Both bridge plugs were retrieved using 0.108 inches slickline and the well was put back into production. This great achievement was recognized as a 1st trial to carry out securing a sour gas well in the Middle East using a combination of electric line and slick line for setting and retrieving TTRPB Inflatable packers and plugs run on coiled tubing and wireline through production tubing for water & gas shut-off applications were introduced in late 1980s. This has brought substantial cost savings by eliminating the workover rig and all ancillary operations required by conventional workover in additional to bringing wells back to production in significantly less time. Expanding the use of thru-tubing retrievable beyond their usual scope, to secure wells where maintenance work was required on x-mas trees, tubing hangers and in this example to retrieve and replace the sub surface safety valve stuck in the tubing hanger in a rigless environment sheds light on a whole new range of applications. The rigless program designed and executed successfully to secure the sour gas well utilizing through tubing retrievable bridge plugs.
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