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Toki, Takahiro
Best Approach From Drilling Perspective Through Concept Select to Pre-FEED for Long Term Development of Offshore Brown Oil Field in Middle East Area
Fujinaga, Ryota (ADNOC Offshore, Abu Dhabi, UAE) | Toki, Takahiro (ADNOC Offshore, Abu Dhabi, UAE) | Toma, Motohiro (ADNOC Offshore, Abu Dhabi, UAE) | Andrews, Kerron Kerman (ADNOC Offshore, Abu Dhabi, UAE) | Alloghani, Khalid Hussain (ADNOC Offshore, Abu Dhabi, UAE)
Abstract 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.
- North America > United States > Texas > Terry County (1.00)
- North America > United States > Texas > Gaines County (1.00)
- Europe > United Kingdom > North Sea > Southern North Sea (1.00)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.16)
A Holistic Approach to Achieve Zonal Isolation Improvements Across 8 1 2 Inch Hole on the in an Offshore Field
Hassan, Azza El (Drilling, ADNOC, Abu Dhabi, UAE) | Abdelatif, Mohamed Samir (Drilling, ADNOC, Abu Dhabi, UAE) | Hamidzada, Ahmedagha (Drilling, ADNOC, Abu Dhabi, UAE) | Andrews, Kerron (Drilling, ADNOC, Abu Dhabi, UAE) | Toki, Takahiro (Drilling, ADNOC, Abu Dhabi, UAE)
Abstract 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.
Delivering Zonal Isolation Assurance in Challenging Long Horizontal Dual Lateral 8- ½-in Hole Reservoir Section–A Case Study in UAE Offshore Field
Hassan, Azza El (ADNOC Offshore) | Abdellatif, Mohamed Samir (ADNOC Offshore) | Hamidzada, Ahmedagha (ADNOC Offshore) | Andrews, Kerron (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Phyoe, Thein Zaw (SLB) | Salazar, Jose (SLB) | Orfali, Mohd Waheed (SLB) | Mozes, Erika (SLB)
Abstract 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.
Abstract 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.
A Challenge for Making a Risk Map of Lost Circulation Based on Geomechanical Evaluation in a Complex Carbonate Reservoir in Offshore Abu Dhabi
Tsusaka, Kimikazu (Inpex Corporation) | Saito, Shun (Inpex Corporation) | Toma, Motohiro (ADNOC Offshore) | Goyara, Yassar Goyara (ADNOC Offshore) | Yudhia, Denya Pratama (ADNOC Offshore) | Fukuda, Kengo (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Matsubuchi, Hitoshi (Japan Oil Development Co., Ltd)
Abstract 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.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.46)
- North America > United States > Wyoming > Bighorn Basin > Garland Field (0.99)
- North America > United States > Texas > East Texas Salt Basin > East Texas Field > Woodbine Formation (0.98)
Hollow Bit: The First Worldwide Campaign Result of a Breakthrough Technology of Slot Recovery Technique in Offshore Abu Dhabi Field
Fukuda, Kengo (ADNOC Offshore) | Biyanni, Hanifan Mayo (ADNOC Offshore) | Toma, Motohiro (ADNOC Offshore) | Moslim, Samaawi Moslim (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Al Zaabi, Ali Yousef (ADNOC Offshore) | Najjar, Abdelrahman (SPETCO) | Chammout, Omar (Western Drilling Tools)
Abstract 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.
- Asia > Middle East > UAE > Abu Dhabi > Arabian Gulf > Rub' al Khali Basin > Abu Dhabi Field (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Dhabi Field > Hith Formation (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Dhabi Field > Gotnia Formation (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Dhabi Field > Burgan Formation (0.99)
Geomechanical Modeling Based on the First Success of Micro-Frac Tests in the Nahr Umr Formation in Offshore Abu Dhabi
Tsusaka, Kimikazu (Inpex Corporation) | Fuji, Tatsuya (Inpex Corporation) | Shaver, Michael Alexander (Independent Consultant) | Yudhia, Denya Pratama (Adnoc Offshore) | Toma, Motohiro (Adnoc Offshore) | Al Ali, Salim Abdalla (Adnoc Offshore) | Toki, Takahiro (Adnoc Offshore) | Couzigou, Erwan (Adnoc Offshore) | Matsubuchi, Hitoshi (Japan Oil Development Co., Ltd.)
Abstract 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.
- North America > United States (0.93)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.72)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.56)
- Geology > Structural Geology > Fault > Dip-Slip Fault (0.35)
- Asia > Middle East > Oman > Central Oman > South Oman Salt Basin > Nahr Umr Formation (0.99)
- North America > United States > Texas > East Texas Salt Basin > East Texas Field > Woodbine Formation (0.98)
- Asia > Middle East > Saudi Arabia > Thamama Group Formation (0.98)
- Asia > Middle East > UAE > Abu Dhabi > Arabian Gulf > Rub' al Khali Basin > Abu Dhabi Field (0.97)
Development and First Application of an Ultra-Low Density Non-Aqueous Reservoir Drilling Fluid in the United Arab Emirates: A Viable Technical Solution to Drill Maximum Reservoir Contact Wells Across Depleted Reservoirs
Jeughale, Ramanujan (ADNOC offshore) | Andrews, Kerron (ADNOC offshore) | Al Ali, Salim Abdalla (ADNOC offshore) | Toki, Takahiro (ADNOC offshore) | Tanaka, Hisaya (ADNOC offshore) | Sato, Ryosuke (ADNOC offshore) | Luzardo, Juan (Petrochem Ltd) | Sarap, Girish (Petrochem Ltd) | Chatterjee, Saumit (Petrochem Ltd) | Meki, Zakaria (Petrochem Ltd)
Abstract 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.
- North America > United States (0.68)
- Asia > Middle East > UAE > Abu Dhabi Emirate (0.29)
- Asia > Middle East > UAE > Abu Dhabi > Arabian Gulf > Rub' al Khali Basin > Zakum Concession > Zakum Field > Thamama Group Formation (0.99)
- Asia > Middle East > UAE > Abu Dhabi > Arabian Gulf > Rub' al Khali Basin > Abu Dhabi Field (0.91)
Hard Backreaming Due to Hole Shrinkage Through Carbonate Reservoir in Offshore Abu Dhabi
Tsusaka, Kimikazu (INPEX CORPORATION) | Fuji, Tatsuya (INPEX CORPORATION) | Toma, Motohiro (ADNOC OFFSHORE) | Fukuda, Kengo (ADNOC OFFSHORE) | Shaver, Michael Alexander (INDEPENDENT CONSULTANT) | Yudhia, Denya Pratama (ADNOC OFFSHORE) | Ogasawara, Hiroyasu (INPEX CORPORATION) | Al Ali, Salim Abdalla (ADNOC OFFSHORE) | Toki, Takahiro (ADNOC OFFSHORE) | Couzigou, Erwan (ADNOC OFFSHORE) | Matsubuchi, Hitoshi (Japan Oil Development Co., Ltd.)
Abstract 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.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.68)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Chalk Formation (0.99)
- North America > United States > Texas > East Texas Salt Basin > East Texas Field > Woodbine Formation (0.98)
Use of Obturating Pills Combined with Low Concentration Acid Pills to Overcome Differential Stuck Challenges in Highly Deviated Wells
Al Ali, Salim Abdulla (ADNOC Offshore) | Mendez Gutierrez, Freddy Alfonso (ADNOC Offshore) | Al Zaabi, Mohamed (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Tanaka, Hisaya (ADNOC Offshore) | Al Kasasbeh, Ameen (ADNOC Offshore) | Vieyra Vallejo, Adolfo (ADNOC Offshore) | Antillon Moreira, Rodrigo (ADNOC Offshore) | Salem Khamis, Ahmed Mohamed (ADNOC Offshore) | Iftikhar, Bilal (ADNOC Offshore) | Wood, James (ADNOC Offshore)
Abstract 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.