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Concept Select and Preliminary Front End Engineering and Design (Pre-FEED) were carried out on a long-term development plan (LTDP) for a brown oil field with nearly 200 existing Wellhead Towers (WHTs) and four existing artificial islands in the middle east area. The development objective is ramping up the production to certain rate and sustain it as long as economically feasible. This paper will describe: Critical stuff that needs to be performed or taken into account from drilling perspective during Concept Select/Design and Pre-FEED How the drilling discipline should be proactively engaged through Concept Select and Pre-FEED for development project of offshore brown oil field During the Concept Select, necessary data related to drilling was firstly collected such as well target locations, available slots on existing WHTs etc. In addition to that, several assumptions were set, associated with drilling rig specifications, constraints on drilling feasibility and number of well slots on new WHT. Based on the data and assumptions, multiple concepts were developed with respect to different drill centers including new WHTs, new artificial islands and existing WHTs/islands in coordination with other disciplines. Techno-economical evaluation was conducted on each concept. Subsequently, Pre-FEED was conducted based on the selected concept. During the Pre-FEED, more detailed study on WHT locations, WHT orientations, WHT design, island location, island design, HSE assessment etc. was conducted by Pre-FEED contractor, incorporating basis and requirements from all the concerned disciplines. Through the Concept Select and Pre-FEED for Long Term Development Plan (LTDP), following things were found important: Generic drilling limits like maximum horizontal departure to targets should be defined clearly at early timing of Concept Select for optimization of well allocation to drill centers Rig specifications and its limits like air gap, skidding envelope and allowable drilling load should be identified at early stage for optimization of WHT design/locations and island design Slot-to-slot distance and row-to-row distance are quite important especially for island in terms of rig operability on island and anti-collision between wells Requirements for area and its arrangement on island should be well defined item-by-item to avoid shortage in the area dedicated for drilling during subsequent stage of project Anything that needs to be studied or considered by Front End Engineering and Design (FEED) contractor should be captured in FEED Scope of Work (SoW) with detailed requirements, which will be utilized for tender process. Anything that is not captured in the FEED SoW could result in variation order or be difficult to be added to the scope after contract award. This paper will present not only the experience in this specific project but also a fundamental approach that will be applicable in any other offshore brown oil fields worldwide.

In an Offshore field, off the coast of Abu Dhabi, well integrity objectives are becoming more difficult to achieve as open hole sections become deeper, laterally longer and more highly deviated. In this mature field, one of the main challenges of well construction is successfully cementing long production-casing strings covering multiple reservoirs across the 8½-in sections. This paper describes some of the techniques and best practices that were applied on these wells to achieve the required zonal isolation. Achieving zonal isolation across multiple reservoirs through a single or multi-lateral configuration is a major challenge in this field. The reservoir formation is porous and requires a special gas tight design or impermeable cement system. Inadequate hole cleaning due to poor standoff attributed to complex well design is another main limitation, resulting in insufficient mud removal leading to an uneven cement distribution around the casing. Additionally multiple pressure-testing cycles are required post cement-setting and during the completion phase, a practice that can destabilize the cement system causing it to fail. Moreover, controlling loss circulation while running or after landing casing is another challenge in this field. To overcome these challenges a series of customized improvements were applied subsequently through continuous improvement and implementing lessons learnt from previous operations. The elements of this approach included introducing higher density cement systems to cover the horizontal sections, while retaining the ECD within the required margins. Another element utilized was that of two cement slurries; Lead and tail, which were designed to achieve controlled ECD. An additional element which was also implemented addressed enhancing the flexible expandable gas tight slurry by adding Latex to achieve a fit for purpose solution. The last element of this strategy included improving hole cleaning and mud removal efficiency by optimizing spacer design and volumes in addition to the loss circulation additives in the spacer systems. Throughout the operation, the cement jobs were executed successfully with no losses. Cement jobs were evaluated through running job design simulation Vs execution parameters comparison. The approach resulted in substantial improvement on log responses. Additionally, after implementing the approach, logs were compared to offset wells from the same field to track the improvement done. The paper reviews enhanced practices implemented to overcome challenges faced during well cementing. Being able to find a solution to this complex problem, delivering a comprehensive cement quality, and improving cementing integrity on these wells resulted in expanding this approach to the rest of the fields. The improvement measures that were developed are now being adopted across all jobs to yield a similar outcome.

The concept of zonal isolation has evolved recently by addressing new industry challenges in identifying dependable barriers throughout the life of a well. In a UAE offshore field, the production section zonal isolation is challenging because of wellbore geometry (long horizontal section) and dual-lateral completion. The cement sheath is exposed to downhole stresses during well construction and the production phases, which compromise well integrity.Adhering to cementing design best practices coupled with the latest technology to enhance mud removal is an important process to achieve a successful cementing job. However, in cases where the cement sheath will be exposed to considerable stresses related to temperature and pressure changes, the selection of cement slurries with adequate mechanical properties will enable the cement sheath to overcome these stresses and maintain zonal isolation during well lifetime. Determining the stress environment between casing/cement/formation vs. cement mechanical properties makes it possible to tailor the cement slurry design to ensure the cement sheath will survive downhole pressure and temperature changes during perforation, stimulation and production operations.Analysis of the offset well data from UAE offshore wells has shown that normal conventional cement systems and previously applied cement job designs have limited success in addressing those challenging complex requirements. Thus, a new approach was required that involved not only the revision of the previously used cement system and spacer, but also revisiting and evaluating every aspect of cementing practices to achieve the desired results. This included increasing the tail slurry density to 16.7 ppg in the horizontal section to overcome equivalent circulating density (ECD) limitations. Fiber-scrabbing spacer technology was introduced to enhance mud displacement and an engineered flexible and expanding cement system was added to achieve and maintain well integrity. The new approach was performed successfully in this case study, and zonal isolation was confirmed by inflow testing. The fiber-scraping approach was used in two wells in the field with excellent results. These successful wells were used to demonstrate the improvements obtained in zonal isolation behind production liners upon implementation of the newly engineered methodology.Numerical analysis modeling was used to simulate the stresses the cement sheath would experience over the well's lifetime and help calculate the cement's minimum required mechanical properties necessary to withstand these stresses. The set cement mechanical properties were then customized using a proprietary trimodal particle-size distribution technology to accommodate the expected downhole stresses. Hydraulic isolation improvement was achieved and confirmed by cementing evaluation logs.

Demands for reutilizing existing slots on the offshore platform are expected to rise to maintain oil and gas productivity by drilling and completing the well to different targets, whereas most of the slots are occupied in mature fields. Slot recovery operations are one of the solutions to recover occupied slots. Different slot recovery techniques have been executed in the Offshore Abu Dhabi field, which include cut & pull, milling, Casing Pulling Tool, and Conductor Deflector Tool techniques which are time-consuming and require high overpull to release the casings. The hollow bit is a slot recovery technique that enables the user to recover casing by the standard fishing tool (i.e., casing spear and overshot) without excessive overpull which inherits a risk of surface equipment damage and safety issues on the rig floor. Moreover, overcoming the strong cement bonding between a 30" conductor and 13-3/8" casing is difficult and is dependent on the cement condition. The casing is cut into short intervals to be pulled out which results in a long operation duration. Hollow bit removes the annulus cement between 30" conductor pipe and 13-3/8" casing by washing over the cement. Casing cuts can be minimized since the removal of cement from the annulus overcomes the cement condition uncertainties which results in a shorter slot recovery duration. This paper presents the 3 hollow bit field trials conducted in 2021-2022 in Offshore Abu Dhabi. Lessons learned accumulated from each trial were implemented in subsequent wells to improve the performance. Performance was increased by 60% compared to other slot recovery methods by reducing the operation duration from 20.8 days to 12.5 days. Best practices that can be implemented to similar application by hollow bit are also presented.

Reducing the number of wells along with the associated capital expenditure, while increasing the production capabilities, has been the target for most of the major oil operators operating in the mature field environment. Wells completed in multi-layered reservoirs with multi-lateral compartments using Extended Reach Drilling techniques has become common practice within offshore Abu Dhabi. Combining smart completion and multi-lateral technology has been proven to be one of the optimum solutions to achieve the well objectives. However, this increases the well complexity and subsequent risk. This paper outlines the recent success story of the first five-zone smart completion, performed in offshore Abu Dhabi. This paper will also highlight the challenges faced, and subsequent lessons learned throughout the installation and operational phases. Achieving a successful well completion installation of a five-zone smart completion in a highly deviated well, with multiple hydraulic and Tubing Encapsulated Cable (TEC) lines in a multi-lateral well involves detailed planning in order to reduce the potential risks and challenges. In order to mitigate these completion challenges, detailed optimizations and improvements were harnessed to increase the success rate and minimize the risk. These optimizations included all aspects of completion design, equipment selection, equipment preparation and completion execution. Simplifying the well design, optimizing the job sequence, and well-planned completion installation procedures assisted with the efficiency of the operation and the overall outcome. Well completion was safely executed ahead of the planned time and achieved the required well integrity requirements. Zonal isolation between flow control valves (FCV), completion tubing, and multiple gas lift mandrels (GLM) were all tested and confirmed as integral. All eight control lines in the completion were tested and confirmed as integral based on the function testing the flow control valves. The permanent down hole gauges (PDHG) were also fully tested before installation and readings taken pre/post installation to confirm their functionality. The successful installation of this well has shown that an optimized well design along with preparation is the key factor to achieving success for a complex smart completion. A well-planned job execution similarly played a crucial factor in this installation. Utilizing proper running equipment, rig space management, and managing the multiple control lines, was also a key factor. This was further complemented by having well-trained service personnel, who were supported onsite during the execution phase which impacted the overall success of the installation. There were, however, some aspects to the operations that require improvements, and this has been captured for any future operations. This paper presents the practices used throughout the well design, and equipment preparation /installation that were adopted over the entire well completion to achieve the key objectives. It also highlights some challenges that were seen during the installation, and operations that allowed for the delivery of a quality completion. All the key learnings from this install, were captured as lessons learned and will be considered for improvements for any future well designs and operations for the future.

We present a root-cause analysis of severe lost circulation and creation of its risk map in an offshore oil field, Abu Dhabi. Lost circulation of more than 100 barrel per hour (BPH) has occurred in sixteen (16) boreholes through the carbonate reservoir. Four (4) out of them experienced total loss. The authors investigated spatial distribution of lost circulation and allowable maximum overbalance based on review of drilling operation in nearly two hundred (200) boreholes. The critical overbalance to reactivate the natural fractures for the tensile-opening or shear-slip failures was analyzed by using geomechanical model. The present study clarified that most of severe lost circulations occurred at the specific sub-layers of the reservoir. The core observation showed that lost circulation occurred in the intervals in which fragmented rocks (rubbles) and fractures were distributed together. The fracture stability analysis revealed that the conductive fractures interpreted by borehole imager were geomechanically stable under conventional overbalance applied in drilling through the reservoir sections. Namely, the planer fractures were geomechanically stable under the current in-situ stress condition. The study concluded that the predominant root-cause of severe lost circulations in the carbonate reservoir was cave-related rocks (cave facies) and excessive overbalance applied to reservoir pressure. The cave facies were supposed to be formed by flank-margin cave system and its collapse due to deposition of overburden formations. A risk map of lost circulation defined the five areas with its potential risk. The risk map indicated not only the risk level of lost circulation but also practical recommendations on the depth to set casing and allowable maximum overbalance. It functions as a practical guide for the design of boreholes in the ongoing drilling campaign.

The 3,000 ft long lateral holes drilled through water-injected area in the carbonate reservoir in the offshore Abu Dhabi have been forced to implement hard backreaming. The abnormal extra operational time has been taken due to poor performance in the operation to pull out a bottomhole assembly after drilling to the total depth. The study aims to analyze root-causes of the hard backreaming through the carbonate reservoir in the studied field. The speed of tripping-out was analyzed every stand of drill pipe by using time domain data of movement of traveling block. The correlations between the speed of tripping-out and rock characteristics such as porosity and constituent minerals in rocks were investigated. Hole shape was analyzed in the representative intervals of low trip-out speed using 16-sector caliper derived from azimuthal density logging. Stress concentration around the borehole wall was also analyzed using geomechanical model. The investigation revealed that hole shrinkage due to plastic deformation of the borehole wall was the most possible root-cause of the hard backreaming in the carbonate reservoir. Namely, BHA had to ream up deformed borehole wall in tripping-out. From the viewpoint of rock characteristics, the speed of tripping-out was found to be lower in the specific geologic layers with higher content of dolomite. This is because dolomite rocks cause larger resistance in reaming it in tripping-out since the strength of dolomite rocks is larger than that of limestone. Based on our findings, use of reamers on bit is found to be the better solution to improve the tripping-out performance in the problematic geologic layers instead of conventional operational attempts such as spotting of acid and use of high viscous fluids in hole cleaning. In addition, optimization of the design and position of reamers and stabilizers is essential to succeed in the future 10,000 ft long extended-reach wells in the studied oil field.

In the studied oil field in Offshore Abu Dhabi, the intermediate hole section has suffered from borehole instability and lost circulation in the higher inclination holes. Borehole instability occurs in the Nahr Umr formation. Lost circulation occurs in the Salabikh formation. This study aims to develop geomechanical model and to analyze mud weight (MW) for successful drilling through the two problematic formations in the studied oil field. In the Salabikh formation, spatial distribution of lost circulation pressure in hundreds of wells in the whole field was analyzed. The fracture closure pressure was also evaluated based on the extended leak-off test and fracture interpretation by image logging. In the Nahr Umr formation, Micro-Frac tests in a 6" hole were implemented to evaluate the minimum in-situ stress. This was the first direct measurement of the in-situ stress in the shale. The magnitude of SHMAX was back-analyzed based on the hole geometry using interpretation of six-arm caliper and analytical solution in the two key locations. This study clarified that severe lost circulation in the crest area was likely to occur due to reactivation of the pre-existing fractures in the Salabikh formation. The lost circulation pressure was found to be approximately 1.4 SG. The study also revealed that the in-situ stress regime in the Nahr Umr formation varied from the crest to flank areas. The crest and flank areas are reverse and nearly normal faulting stress regimes, respectively. Its transition area is strike-slip faulting stress regime. The regional difference in in-situ stress regime depends on the extent of mechanical anisotropy of the shale and the magnitude of tectonic strains. By integrating the results, with respect to the borehole stability analysis in the Nahr Umr formation, instead of a conventional lower hemisphere representation of the required MW based on failure width at borehole wall, the study analyzed the geometry of the failure area around the borehole wall under the allowable range of MW constrained by the lost circulation pressure in the Salabikh formation. As a result, the borehole failure cannot be avoided in any hole inclination in the Nahr Umr formation under the allowable range of MW to prevent severe lost circulation in the Salabikh formation. Therefore, appropriate practice to transport cavings is one of the key elements for safe drilling in higher hole inclination across the intermediate hole section in the studied oil field.

In 2020, A Major Offshore Operating Company in UAE faced a high differential pressure stuck event. This took place, during the execution of formation evaluation with a conveyed pipe sampling BHA. It is well known that after a differentially stuck pipe event happens, the success ratio will be time dependent (i.e. the less time a pipe remains stuck, the more chances there will be for it to become released) and the chances of releasing the BHA are always limited to the logging tools tensile limitations. One of the most common and successful methods to release differentially stuck BHA's specifically in limestone formations is by pumping and soaking acid pills. However, under such a high differential pressure environment, the use of acid may induce losses in the so called "thief zones", causing worse problems. The standard release procedure started by working the string within the tensile limits, followed by pumping acid pills (using the available volume mobilized before spudding each drilling section). During the first acid pills pumped to attempt to release the stuck pipe, loss volume pump rates, acid pill position(s) and coverage in the annulus was assessed and evaluated. Based on the results it was observed that the thief zone was in direct contact with the Pipe Conveyed circulation port, at the latching assembly. This then created a situation whereby, the acid pills were lost immediately after the acid came into contact with the formation. Utilizing low acid concentration pills also had the same effect. The solution was to pump an Obturating pill made-up of a weighting agent as a spacer behind the high volume, low concentration acid pill with crosslinking divergent chemicals, pumped at a high flow rate. This solution reduced the acid losses across the thief zone and once the Obturating pill came into contact with the loss zone, it facilitated the seal and cured the losses, by allowing the acid to move up the annulus until it reached the differentially stuck point and soaked across the problematic area. Once the acid pill was successfully placed at the required location using this method, the string was worked and successfully released. This combination of low concentration acid along with crosslinking divergent chemicals coupled with the Obturating pill behind the acid helped a major offshore operating company to pump the acid pill under partial losses only, to regain full circulation after only 10 bbl. of Obturating pill had entered inside the annulus. It allowed the acid pill to react across the stuck point, while keeping the string under low torque and compression. The operator was able to release the sampling BHA and bring it back to surface avoiding a lost in hole cost of around 4 MM$. The Obturating pill combined with low concentration CDC acid pill is proven to be a successful method in drilling operations when trying to release differentially stuck BHA's within a wellbore.

Drilling and completion operations in depleted reservoirs, are challenging due to narrow margin between pore and fracture pressures. Therefore, Ultra-Low Density Reservoir Drilling Fluid (RDF) with optimum parameters is required to drill these wells safely. Design and effective field application of a sound engineered fluid solution to fulfill these operational demands are described. Ultra-Low Density RDF NAF with minimal fluid invasion characteristics was developed after extensive lab testing, to cover the fluid density from 7.2 – 8.0 ppg. The fluid properties were optimized based on reservoir requirements and challenging bottom-hole conditions. The design criteria benchmarks and field application details are presented. Fluids were stress tested for drill solids, reservoir water and density increase contamination. Multi-segment collaboration and teamwork were key during job planning and on-site job execution, to achieve operational success. For the first time in UAE, a major Offshore Operator successfully applied an Ultra-Low Density RDF-NAF, which provided remarkable stability and performance. The fluid was tested in the lab with polymeric viscosifier alone and in combination with organophilic clay. In order to gain rheology during the initial mixing, about 3.0 ppb of organophilic clay were introduced to system along with the polymeric viscosifier. Later, all the new fluid batches were built with polymeric additives alone to achieve target properties. A total of 10,250 ft of 8 ½" horizontal section was drilled to section TD with record ROP compared to previous wells in the same field, with no fluids related complications. With limited support from the solid control equipment, the team managed to keep the density ranging from 7.5 ppg to 7.8 ppg at surface condition, using premixed dilution. Bridging was monitored through actual testing on location and successfully maintained the target PSD values throughout the section by splitting the flow on three shaker screen size combination. Due to non-operation related issues, hole was kept static for 20 days. After such long static time, 8 ½" drilling BHA was run to bottom smoothly precautionary breaking circulation every 5 stands. Finally, after successful logging operation, 6 5/8" LEL liner was set to TD and the well completed as planned. Success of this field application indicates that an Ultra-Low density fluid can be designed, run successfully and deliver exemplary performance. Lessons learned are compared with conceptual design for future optimization. Laboratory test results are presented, which formed the basis of a seamless planned field application.

A Major Operating Company in UAE planned and drilled a challenging 6 inch horizontal drain after crossing twenty-seven formation sub-layers. The heterogeneity of pore pressure varied from equivalent mud weights as high as 10.6 ppg to as low as 7.1 ppg across the exposed reservoirs. Control of the equivalent circulating density (ECD) values to safely drill across these multi-reservoir sections and diverse reservoir pressures was one of the top challenges on this well, as the fracture gradients (FG) ranged from 13.5 ppg across the competent reservoirs to as low as 11ppg across the fractured reservoir section. The offset well data review show that 4 out of 6 wells encountered moderate, severe and total losses with mud weight (MW) ranging from 11 ppg to 11.3 ppg, which were cured by using heavy LCM treatments and in some cases, after several failed attempts to cure losses, cement plugs were used. Historically, the average time spent curing total losses in these wells varied from 2-3.5 weeks causing well cost increments as consequence of this non-productive time. All of the above, without mentioning the extra efforts, resources and risks were faced due to well control and stuck pipe events which occurred on those wells. Engineering and Operation teams worked together to engineer a solution to drill this well in one run while safely maintaining the well under control and managing the losses. The Bottom Hole Assembly (BHA) was designed to withstand the well challenges including multiple contingency options. These options allowed:Improving hole quality while tripping using a special type of eccentric reamer stabilizer.Pumping various LCM concentration scenarios through a multi-cycle circulation valve. In addition, a special type of float valve was placed on the top of the BHA as barrier, stopping back flow under surface backpressure or kick scenarios.Optimizing mud weight by using formation pressure while drilling (FPWD) and monitoring both equivalent circulating density ECD and equivalent static density (ESD) by pressure while drilling tools. The drilling fluid was loaded with non-damaging loss circulation material without compromising the MWD/LWD limits. Additionally, the mud rheology was carefully selected and monitored to achieve the desired ECD. On surface, a managed pressure while drilling system was deployed to give control on reservoir pressures. In instances of influx, MPD allows to early detect any kick and controlled by surface back pressure without requiring shut in for applying standard well control techniques. Keeping the well under control by surface back pressure (SBP) during connections time (flow–off). Additionally, MPD also enables the contingency of applying pressurized mud capping in case of unable to control the losses. As decision point, a loss management plan was prepared and implemented. Also, a dynamic formation integrity test was planned and performed to calibrate the fracture gradient across the loss zones. The problematic zone was successfully drilled with one BHA in under six days (5.73 days). The estimated savings for the company were 8 days, which equates to ±1MMUS$ after including the MPD cost which increased the well cost by 200MUS$. To further complement the outright savings, the engineered solution managed to safely stave off operational complications as well as incurring the related complexities and non-productive time (NPT) as recorded on the offset wells. Additionally, well was successfully landed and geo-steered across the target formation and 4½ in liner was run and cemented off-bottom avoiding the need to develop a slot recovery scope on this well with an extra duration of +/-35 days. The engineered solution provided a high level of preparation and contingencies within the BHA, Managed Pressure Drilling Equipment, real time monitoring, mud and cement formulation. The applied techniques allowed the operating company to successfully execute this challenge well within the proposed time and budget.

107 new wells are planned to be drilled primarily from two new Artificial Islands during the period of one project from 2023 to 2029. The number of existing wells in the oil field has reached 1,068 Mother bores, 2,178 wellbores @16,453,666ft total well length as of December 2019. Trajectories, especially from existing Artificial Islands, are getting more complex so as to avoid collision issues, and it is becoming increasingly difficult to drill accordingly. It is of great importance to assure that it is possible to drill the planned wells without serious collision issues before the execution of the project. Trajectories for planned wells were drafted one-by-one utilizing "DecisionSpace Well Planning" based on the predetermined slot allocation with the planned drilling pad design. Geological models are incorporated into DecisionSpace Well Planning. Therefore, formation tops were taken into account in order to make the trajectories more realistic. After that, trajectories were exported to "COMPASS" and anti-collision scan was performed on well-by-well basis. Anti-collision scan was performed among planned wells as well as actual wells. In case that one well has such serious collision issues that the well cannot/should not be planned based on company policy as a result of Anti-collision scan, trajectory or Landing Point (LP)/Total Depth (TD) location were adjusted. Then, Anti-collision scan was carried out again. If it was confirmed that there is no serious Anti-collision issues, trajectory was considered as final. It has been found that all the wells during the period from 2023 to 2029 can be drilled without serious collision issues by slightly adjusting LP/TD while satisfying several practical drilling requirements. Through the Anti-collision study, following recommendations for the avoidance of collision were obtained:Multi Station Analysis (MSA)+In-Field Referencing (IFR)+SAG correction should be applied in all the Jack up operations as well as Island operationsApplication of real-time MSA should be considered on a case-by-case basisMWD survey for the past wells should be corrected with IFR+MSA to reduce EOU sizeRe-Gyro jobs for low-quality survey wells should be enhanced around the project's development areaKick off point (KOP) should be deeper in the center of the drilling pad and shallower in the edge of the drilling pad

Slot recovery operation can be considered as one of the most time consuming operation. Cut and pull casings, or milling casings have been carried out as typical method of slot recovery. However there are a lot of risks with this typical method such as poor progress of milling, damaging top drive due to high vibration while milling or sudden string jumping up while overpulling and possibility of string stuck caused by poor hole cleaning while milling. We have completed slot recovery operations on numbers of wells, but there were a lot of troubles caused by above mentioned adversaries on rig equipment and taking a lot of time to complete operation. There are several kinds of new slot recovery technologies that may save rig time and less harmful than conventional method. Casing Pulling Tool (CPT) is one of the new technologies which eliminates or mitigates risks mentioned above. CPT has piston internally and it is activated by applying pressure inside string. CPT is run with casing spear and drill pipes. Once spear is engaged with casing and apply pressure inside drill string, CPT provides pulling force on casing. Pulling force is varied depend on the applied pressure and maximum available pulling force is more than 1,000 kips. Hence upper part of string is anchored at rotary table by slips, pulling force is applied on casing and drill string below rotary table. This means no pulling force is applied on top drive and minimize the chance of getting damage on it. As an actual case, we could successfully recover 13-3/8" casing by CPT without having any troubles and complete slot recovery operation with saving rig time compared to the conventional methods. This paper introduces the details about the case mentioned above.

Over the course of drilling wells in one of ADNOC Offshore fields, there have been numerous endeavors in the Crestal region of the field with each well presenting its unique array of issues and challenges related to well construction, stability and delivery. Even while drilling two identical wells with extremely similar well designs and architecture, the wells encountered different and at times opposite responses from the formations being drilled. This resulted in the well construction becoming more problematic than expected in some cases while in others the situation was completely opposite, thus drilling and well construction went extremely smooth delivering the well ahead of time as opposed to the nearby sister well. While the denominators may be segregated based on commonality and differences, there is one particular aspect of the drilling process and planning that has been significantly overlooked, the Azimuth of the well particularly in the crestal region of the field. Over the years, investigation into the well trajectory, the well fluids and intrinsic properties have been dissected to arrive at a result but has not produced the expected success. The Azimuthal impact on the resultant seems to have been ignored to the extent of not understanding the Azimuth impact on a well trajectory. It is of paramount importance to investigate and identify the imp act since the related stresses and their directions directly define and drive the stability and the optimal mud weight needed to drill successful wells.

The paper explores the contributing factors impacting/constituting enhancement of the drilling in the 6' section in one of the giant offshore fields of ADNOC. While there is a tangible and obvious contribution from the surface manipulation of parameters, there is also an irrefutable connect between down hole factors and ROP. Factors such as formation density, porosity, Mechanical Specific Energy, Orientation, mud weight, DDI crestal or flank placement of the well and their impact on performance. The crestal wells have come with their own inherent downhole problems and challenges. While at times there is linearity between the formation Mechanical Specific Energy and formation Density, there isn't necessarily a linear relationship between the drilling parameters and the resultant ROP. The density and porosity of the formation not only impact the MSE but the ROP downhole as well. The required parameters to drill each formation also vary with these properties and their effectiveness can in turn be tracked with the MSE being seen as a direct result of the BHA and formation interaction. The analyses entailed cover the formation density, discrimination plots, Azimuth, mud weight, BHA stabilizations, MSE and the respective intra parameter interactions that form the overall resultant drilling performance.

Driving efficiency to ensure cost and risk reduction in well operations is paramount for any operating company; to achieve this, the main objective was to implement a continuous improvement process that measures performance to then improve it, acquiring lessons learned and finally implement new technologies to reduce non-productive time, invisible loss time and push the technical limit to the limit. The first step was to measure the current performance to determine average and best references to compare against. The drilling operations and engineering teams defined KPIs for each well type and respective sections and activities involving all levels of the organization including every individual, ensuring effective communication inclusive of Rig Crew and Service Providers. The initial KPIs were defined, discussed, validated and agreed by both operations and engineering management, all engineers were informed and challenged to measure their performance against KPIs. Once new records were achieved, a workflow to document best practices initiated, once identified, validated and documented, becoming the new standards. Similarly, once average performance was not achieved, a ‘Lessons Learned’ workflow was initiated. Aiming to get the team engaged a communication protocol of the Highlights and Lowlights was put in place, including recognition during operations meeting and emails. The primary results of the deployment of this initiative include the delivery of a 10% additional well count compared to the initial year's plan. An overall improvement of the overall Drilling and Completion Performance was also noted. An important improvement of the overall Rate of Penetration (ROP) was observed, as one of the key performance indicators. It was also notice a considerable reduction of the Flat time. New practices for losses mitigation in hazardous areas were stablished. The lower completion design was enhanced. The upper completion design and utilize Dual Hydraulic Packer in Oil producer well was optimized. Finally, the 1st Maximum Reservoir Contact Well was completed for two of the three Fields in the Team. The added value achieved by the implementation of these innovative practices includes the implementation of the KPI Gauges as a visual instrument to be used on daily operations meeting by the engineers and management, to quickly and effectively understand performance and improvement in multiple dimensions. Additionally, the implementation of a continuous improvement mind-set, focus in introducing changes gradually instead of radically to ensure a soft and solid adoption embraced by all team members. Finally, the improvement of the office-field communications, including a sense of ownership and achievement for each goal to achieve and record to break, to the point that every colleague involved in a specific operation, independently of their organization (Operator, Contractor or Service Company) is equally committed and engaged.

Injection of drilling waste into subsurface formations proves to be an environmentally-friendly and cost-effective waste management method that complies with zero discharge requirements. It has now become the technology of choice in offshore Abu Dhabi. The aim of cuttings reinjection (CRI) is to mitigate risks associated with subsurface waste injection and reduce cuttings processing time and cost. In order to meet these goals, a cuttings reinjection subsurface assurance methodology was developed to improve cuttings processing and continuously monitor drilling waste injection operations. Preparing for CRI operations required extensive drilling cuttings slurry testing to minimize processing time and develop optimum particle size distribution to reduce cost and increase the injected waste volume. The improvements were accompanied by downhole pressure and temperature monitoring of the injection well, thus facilitating analysis of injection pressures. Fracture containment was verified through a combination of pressure decline analysis, periodic injectivity test, temperature survey, and periodic modelling for fracture waste domain mapping. A backup injection well was used also as an observation well to monitor the pressure signitures in the injection formation. More than 1 million barrels of drill cuttings and associated drilling waste have been safely and successfully disposed of into a single injection zone of CRI well over three years of operations. The cuttings reinjection subsurface assurance method optimizes grinded cuttings particle size distribution, detects and identifies potential risks to provide mitigation options to prolong the life of the injector. The proactive subsurface injection monitoring-assurance program was built into the fit for purpose CRI injection procedure to continually avoid injecting any rejected hard material, improve and update the process as per subsurface injection pressure responses, thus reducing processing time and cost, mitigating injection risks, and extending the injection well life. This paper presents the unique and technically challenging cuttings slurry properties design and pressure interpretation experience learned in this project; the enhancement of cuttings processing helped increase injection volumes and an in-depth interpretation of fracture behavior which behaved like a risk-prevention tool with mitigation options. Significant enhancement was developed in slurry treatment procedures to avoid injectivity loss and maximize the disposal capacity.

Gathering of wireline data in Extended Reach Drilling (ERD) wells is still not a standard process, complicated even more by inclination and step out. This paper presents a case study of recording logs conveyed using an open hole tractor in a highly deviated section. The challenge was made more difficult because Water Based Mud (WBM) was required to allow the full suite of planned logs. The operation time that can be saved is up to four days. The 8.5 in. pilot hole was designed based on the target and the sidetrack points for the mother hole. The inclination of the pilot hole was 63° and the wireline accessibility simulation based on offset friction factor showed that the open hole was not 100% accessible with Wireline Conveyed Logging (WCL) string. Therefore, an open hole tractor was selected to reach the required point. To minimize the risks for the logging operation, a six blade Polycrystalline Diamond Compact (PDC) bit, Rotary Steerable System (RSS) and Logging While Drilling (LWD) were used in the pilot hole to make a smooth trajectory and confirm wellbore conditions. The logging operations were conducted smoothly and safely. It was observed that the actual results matched very well simulations, and the open hole tractor was required to convey the tools to the Total Depth (TD). The total tractoring length was 16,000 ft over the four runs, and there were no issues observed during the tractoring which confirms that the steps taken while drilling the section were correct and approximately four days of operation were saved by means of the open hole tractor as compared to Pipe-Conveyed Logging (PCL) operation. In addition, the mother hole length also was minimized to get proper sidetrack point from the optimized pilot hole trajectory and the potential total saving time would be more than seven days. This paper also describes the optimization of well trajectories for pilot hole and mother hole and the gap related to planning from drilling and logging points of view, with aim to ensure 100% data gathering. The use of an open hole tractor for long interval in highly deviated well is the first time in the United Arab Emirates (UAE) and WBM conditions are non-standard operations which require significant amount of preparation during execution.

From the start of the drilling campaign on the remote Satah Al Razboot (SARB) artificial islands located in United Arab Emirated (UAE) the operator used multiple optimization initiatives to enhance drilling performance and well delivery. Even though the complexity of the wells increased over time, when extended reach drilling (ERD) envelop started to expand, with the implementation of optimization initiatives the well construction time significantly decreased. This paper describes the way of thinking and steps taken to boost the performance to the absolutely new level for the operator. The main objective in actual harsh economic conditions was to drill the wells under the budget without jeopardizing well integrity, service quality and HSE. The ultimate goal was to decrease well construction time by 25%. To achieve this goal, several well construction optimization workshops were organized aiming to challenge and find improved drilling processes, operations procedures, tools, equipment and well design, as well as to have a clear plan on smooth expanding ERD envelop. In addition with the workshop initiatives, an Operational Performance Improvement Plan was developed aiming to analyzed all operational opportunities to reduce time; a dedicated well engineering, subsurface and operations team was set up to lead the feasibility studies and ensure the implementation of the approved initiatives. Implementation of all performance improvement initiatives required a balance between all involved parties. Every decision should be verified by multiple teams, included but not limited by drilling, equipment, completion, subsurface, production and intervention. Once the approval is obtained then the initiative is implemented and analyzed, taking into account increasing complexity of the wells and lesson learnt captured. At the same time not all the initiatives were implemented – some were rejected due to significant increase of service quality risk; some due to HSE associated risks. The implementation of the initiates and ideas contributed to the reduction of flat time, elimination of online operations, etc. The manuscript describes the steps taken to drill extended wells within shorter time compare to standard deviate and horizontal wells. It highlights main challenges faced during implementation of the performance improvement plan and describes techniques and technologies used to overcome them.

After Cuttings Re-Injection (CRI) wells are drilled and cased over the targeted zone, the next step in the process towards finalizing the well is usually perforating the casing. Perforating guns can be deployed with the rig on location or rigless after the production string has been run in the well. Operations with the rig usually offer the benefit of being able to use larger guns with improved formation penetration and larger perforation tunnel size. The extra penetration helps bypass the damaged zone around the wellbore to get into the better permeability of the undamaged formation rock for improved injectivity. The larger perforation tunnel allows more contact with the formation and increased flow area, factors which also help improve injectivity. Rigless perforating generally requires smaller guns which can pass through the tubing, and therefore offer less formation penetration and smaller perforation tunnels. However, one of the major benefits of the rigless operation is the rig time savings, which can often be substantial. Very good injectivity is a must for CRI wells to manage the large amount of cuttings that will be injected. Large diameter holes in the casing are necessary along with a high shot density for more holes, and 7″ perforation guns were required for the 9-5/8″ casing to achieve these characteristics for injection purposes. When large perforating guns are used, the tubing-conveyed perforating (TCP) technique is usually prefered over cable-conveyed guns because of possible cable damage from shock when the guns are detonated. The TCP technique often requires more rig time however and usually results in more overall cost than for a wireline operation with a small number of gun runs. Another consideration for the CRI wells is that they are drilled by a new rig with a relatively inexperienced rig crew. Considering rig performance, using wireline for the perforating operation could therefore be more effective in reducing operating time. However, a number of factors have to be taken into account when preparing for perforating using longer, large diameter gun strings on cable, including gun string weight, shock on cable head when the guns are detonated and cable weak points. The shock forces for this case were modeled with special software and the necessary high-strength cable, shock absorbers and weak points were procured for the operation. Rig up limitations also had to be considered to manage the length and weight of the heavy string and a special sequence was prepared and implemented using an on-site crane. The job was managed safely and efficiently in the single planned run, marking the first time this type of operation has been done in the country and this paper summarizes the process and the efficiency results.

This paper examines the challenges, solutions and milestones of the hydraulic fracturing based cuttings reinjection (CRI) process implemented on two artificial islands offshore Abu Dhabi. During the development of an offshore field from two artificial islands, disposing of vast amounts of drilling waste and cuttings, generated from almost 100 wells, presented a major challenge. The conventional skip-and-ship for onshore treatment and disposal was technically, logistically, and economically unviable and posed possible future environmental liability. After careful assessment, total containment of drilling waste on the islands through multiple hydraulic fractures in suitable formations, for permanent in-situ waste confinement, was concluded by the operator as environmentally and economically the only sustainable process. Two CRI wells were planned on each island to accommodate an estimated 8 million barrels of drilling waste slurry expected to be generated at the islands. While CRI is a proven technology wherein cuttings are slurrified and injected into sub-surface formations, fracture injections have high risks too. Many failures are known in the industry, including well and formation plugging and waste breaches to sea-bed and near-by wells, with far-reaching consequences and liability to operators. Considering the complexity of the multiple-hydraulic fracturing process that requires careful planning, execution, monitoring, and analysis, a comprehensive geomechanical study was performed to identify and characterize all potential injection formations to achieve successful long-term injection. This was followed by front-end engineering design (FEED), fracture simulations, CRI well design, surface facilities design, slurry simulations, and followed by careful execution. Two CRI wells were drilled on each island. Specifically designed injectivity tests were performed on each well before commencing injection, followed by regular injectivity tests to continuously analyze fracture behavior. A carefully designed slurrification and injection process, incorporating detailed QA-QC at all process stages, was implemented that helped to avoid solids settling, fracture or perforation plugging, uncontrolled fracture propagation, or well integrity issues. About 500,000 barrels has been successfully injected to-date in two CRI wells with injection pressures as per FEED estimates. The paper details also the proactive sub-surface injection monitoring-assurance program built into the CRI injection procedure to continually modify the process as per sub-surface pressure responses, thus proactively mitigating injection risks. Periodical injectivity tests, model alignment studies, temperature logs, and fracture pressure analysis facilitated regular recalibration of the geomechanical model to define fracture-domain sizes, monitor fracture height growth, and estimate residual formation domain capacity as injection progressed. The multiple-hydraulic fracture-based CRI process implemented first time in Abu Dhabi incorporates many unique features which can be applied in similar projects elsewhere. This paper also describes the downhole gauges for accurate pressure-temperature monitoring at perforations, a detailed slurry design, the particle-size distribution for slurry quality analysis and quality control, the sub-surface monitoring-assurance program and regular tests and recalibration studies.