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BACKGROUND:Bacillus Calmette-Guérin (BCG) vaccine-related complications are frequently observed in children in Oman. There are a few regional studies on BCG complications, but none from Oman.OBJECTIVE:Evaluate the spectrum of BCG-vaccine related complications and immune status in Omani children.DESIGN:Retrospective cross-sectional study.SETTING:Referral tertiary hospital.METHODS:Children aged younger than 13 years old and with complications of BCG vaccination recorded from 2006-2018 were included in this study. Clinical characteristics, treatment, immune workup and outcome were reviewed from hospital records.MAIN OUTCOME MEASURES:Different BCG vaccine-related complications categorized by the site of involvement.SAMPLE SIZE:226.RESULTS:Of the 226 children had BCG-vaccine related complications, 99% received BCG vaccine immediately after birth. The median age of presentation was 4 months. The most common complication was isolated BCG lymphadenitis (85%, n=192), followed by BCG-related osteomyelitis (10.2%, n=23) and disseminated BCG infection (4.9%, n=11). The median age of presentation of disseminated BCG was 5 months, with different organs involved. Out of 11 children with disseminated BCG infection, 72.7% (n=8) had primary immune deficiency (PID), including chronic granulomatous disease (CGD, n=5), severe combined immunodeficiency (SCID) (n=2); 1 patient had Mendelian susceptibility to mycobacterial disease (IFNGR2 deficiency); 2 patients with PID not yet identified and the 1 with a non-specific PID had blood or saliva samples sent for whole-exome sequencing.CONCLUSION:Because of the spectrum of BCG vaccine-related complications, including the most severe in children with PID, we suggest that delaying the BCG vaccine from birth to 6 months may prevent disseminated BCG diseases and their complications in children with PID because any PID will have been identified before 6 months. Further studies are needed to guide this recommendation.LIMITATIONS:Single center-based study that may not provide a full overview of all BCG vaccine-related complications in Oman. Unavailability of details of some microbiological results and an inability to determine the detailed management for all patients.CONFLICT OF INTEREST:None.

The prevalence of self-medication (SM) has increased in health professionals due to awareness of disease and symptoms. Incorrect use of medication caused harmful effects. To assess the knowledge, attitude and practice of health professionals, this survey was conducted. A cross-sectional study was carried out among health professionals of different specialities. Knowledge, attitude and practice-based questions were asked through an electronically distributed questionnaire. Data were statistically tested using the Chi-square test with SPSS. Most of the health professionals were aware with the term of self-medication; however the knowledge about related questions was not satisfactory. Almost half of the participants practiced self-medication. The prevalence of self-medication among participants was high. They need to be trained and educate about the incorrect use of self-medication.

A successful cement job is a crucial element of obtaining and maintaining well integrity and ensuring safe and efficient hydrocarbon production. The success of cementation starts with a full understanding of good parameters such as formation characteristics and depends on a properly designed slurry and spacer system. The most challenging part of cementing a wellbore is cementing one with a low fracture gradient. There's a high risk of formation breakdowns and hole instability if maximum allowable equivalent circulation densities (ECDs) are exceeded. In addition to severe losses and formation damage, the outcome includes inefficient placement of the cement that warrants time-consuming and costly operations to assure zonal isolation. In Kuwait, first trial of a new generation of an environmentally friendly enhanced aqueous spacer system was used successfully in a highly deviated well for cementing the production casing covering shale formations. This paper discusses the design of the enhanced aqueous system and its technical features and benefits, which helped improve the cement bond and achieve zonal isolation.

Introduction GNE myopathy is a rare recessive myopathy caused by mutations in the GNE gene. It is mainly a distal myopathy with relative sparing of the quadriceps muscle. Methods Patients with distal myopathies from Kuwait were examined and tested for the Middle Eastern GNE gene founder mutation, p.M743T. Patients were further studied for disease-associated features. Results GNE myopathy was confirmed in 14 of the 37 patients (37.8%) screened. All cases were caused by the p.M743T mutation. Age of onset and time from disease onset to loss of ambulation were variable. Both wasted and hypertrophied calf muscles were noted. Severely affected quadriceps were present in 1 patient, and ptosis, ophthalmoplegia, and tongue wasting in another. Discussion The scope of the p.M743T mutation now includes the Arabian Peninsula. Variations in age of onset, disease progression, and distribution in patients harboring the same mutation suggest the role of other genetic- and environment-modifying factors. Muscle Nerve 58: 700-707, 2018.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Here we demonstrate biallelic mutations in sorbitol dehydrogenase (SORD) as the most frequent recessive form of hereditary neuropathies. We identified 45 cases from 38 families across multiple ethnicities, carrying a particular nonsense mutation in SORD, c.753delG; p.Ala253GlnfsTer27, either in homozygous or compound heterozygous state with a second variant. With an allele frequency of 0.004 in healthy controls, the p.Ala253GlnfsTer27 variant represents one of the most common pathogenic alleles in humans. SORD is an enzyme that converts sorbitol into fructose, in the two-step polyol pathway that has been implicated in diabetic neuropathy. In patient-derived fibroblasts, we find a complete loss of SORD protein as well as increased intracellular sorbitol. Also, serum fasting sorbitol level was over 100 times higher in patients homozygous for the p.Ala253GlnfsTer27 mutation compared to healthy individuals. In Drosophila, we show that loss of SORD orthologues causes synaptic degeneration and progressive motor impairment. Reducing the polyol influx by treatment with aldose reductase inhibitors normalized intracellular sorbitol levels in patient fibroblasts and in Drosophila, and also dramatically ameliorated motor and eye phenotypes. Together, these findings establish a potentially treatable cause in a significant fraction of patients with inherited neuropathies and may contribute to a better understanding of the pathophysiology of diabetic neuropathy.

This paper investigates the applicability of Low Salinity (LoSal) EOR for a Kuwaiti reservoir. Many reservoirs in the Middle East are not producing satisfied results after depletion methods for a long time of production. Therefore, new management and production strategies must be determined in order to meet the global market demand for oil, which can be done using Enhanced Oil Recovery (EOR) techniques. In Kuwait, one of the EOR methods that could be applied is the use of Low-Salinity (LoSal) Water Flood. Results from previous research have clearly shown that LoSal water injection has a significant impact on oil recovery. Although there are many LoSal experimental results reported in the literature, the process mechanisms and the prediction modeling are yet to be fully investigated and understood. As a result, further experimental work is needed in order to be able to develop reliable prediction tools. The research in this paper is an integrated study combining laboratory work to assess the performance of LoSal water flood using live crude, reservoir brine and native core with wettability conditions restored. The core flooding phase will conduct series of low salinity water flood experiments, design of Salt type and concentration. The performance of LoSal will be compared to different salinities water flood based on reservoir water salinity.

To optimize production from a key reservoir, obtaining a core sample with minimum fluid invasion and damage was necessary. In addition, operational nonproductive time (NPT) related to drilling challenges, such as interbedded formations of varying formation pressures, wellbore instability in the reactive, stressed shale sections, and hole cleaning concerns, needed to be mitigated. This paper describes the design of the drilling fluid and its performance in the field. After completion of the first dump flood water injection well drilled using an 80/20 conventional nonaqueous fluid (NAF) weighted with barite, low injectivity was observed, which led to acquiring cores to analyze permeability and porosity along with the change in mineralogy resulting from long exposure of the reservoir in the water zone. A 70/30 organophilic clay-free (OCF) NAF was selected to mitigate equivalent circulating density (ECD) risks and minimize damage. Proprietary software was used to customize the bridging design, which was verified during laboratory testing, and to help ensure adequate hole cleaning with the customized low-ECD fluid. The engineered OCF NAF contained no damaging materials, such as barite, asphaltic material, or organophilic clay. OCF NAFs are well suited to low-ECD drilling operations because they are more resistant to weighting material sag than conventional NAF systems of similar rheology. This is a product of the high gel strengths developed, even in low-rheology (low-ECD) fluids. Downhole pressure fluctuations are low because these gels are fragile and break easily. For the well in which this OCF NAF was used, drilling, coring, and logging operations were successfully completed without incident. Four cores were acquired with minimal damage compared to the previous wells resulting from the engineered design of the bridging material and fluid-loss control polymers. In addition, there was minimal erosion to these four cores, which was a result of the low-ECD fragile gel fluid used. The fluid-loss control properties of the fluid were also effective in strengthening the wellbore and eliminating differential stuck pipe tendencies that had been observed in previous wells. The fluid properties resulted in minimal ECD, and the OCF NAF displayed excellent suspension along with improved pressure management; no pressure spikes occurred while breaking circulation. There was no NPT related to wellbore instability or any of the drilling challenges previously identified. This unique organophilic clay-free and organolignite-free drilling and coring fluid relies on a specialized technology involving an interaction between the emulsifier package and the polymer additives in the fluid. This provides the behaviors needed for reliable weight material suspension and suitable hole cleaning properties in a low-ECD drilling fluid. Together with the appropriately designed bridging package, the OCF NAF provided a better understanding of the reservoir characteristics by delivering the core with minimal damage.

Conventional coring does not provide core samples that are characteristic of the original formation condition. Thus, pressurized coring is required to capture samples that represent the in-situ composition of gases and liquids; pressure, volume, and temperature (PVT) data of the fluids, and porosity, permeability, and wettability, which are critical to reservoir interpretation and development. A customized high-performance water-based mud (HPWBM) was used successfully where prior attempts with conventional water-based mud (WBM) had failed. The key well challenges included wellbore instability with caving shale and depleted reservoir sands. Previous attempts to retrieve pressurized core using conventional WBM proved unsuccessful because of the early activation of the pressurized capture mechanism caused by an accumulation of wellbore and mud solids linked to insufficient hole stability. A HPWBM containing liquid additives was customized to minimize solids content while stabilizing the shales and to minimize the differential sticking potential in the depleted reservoir. The formulation was finalized, based on laboratory testing, to optimize the bridging and inhibition package for the formations drilled. Drilling and logging were successfully completed with no incidents; the fluids parameters were maintained to effectively clean the hole while controlling equivalent circulating density (ECD) through minimizing solids in the mud. The combination of salinity and liquid additives used minimized the total solids of the mud while effectively stabilizing the wellbore, which helped to reduce the premature activation tendency of the catcher system of the pressurized coring tool. Pressurized cores were successfully retrieved with in-situ conditions and analyzed on-site, maintaining a pressure equivalent to the pore pressure. The core samples were retained in their native state for future studies. There was no nonproductive time (NPT) related to wellbore instability, and differential sticking was avoided by the customized bridging across the depleted reservoir. The successful collection of data enabled improved reservoir modeling. This paper discusses the design of the HPWBM system, along with its technical features and benefits, which helped to successfully complete the first global 12 ¼-in. pressurized coring application. The customized HPWBM provided good shale inhibition, low solids and excellent lubricity, and eliminated the need for conventional shale stabilizing materials, which could have interfered with the capture of the pressurized core.

One of the common challenging drilling environments is harsh rocks which require specially tailored drill bit design features to deliver the maximum drilling efficiency. The interbedded nature of harsh rock formations in combination with high rock strength results in reduced bit aggressivity and premature bit wear which increases the drilling costs. This paper presents field testing a new drill bit technology that addresses those challenges. The bit was deployed and tested in a vertical application in an exploratory well in North of Kuwait and achieved the fastest penetration rate in the application. Numerous full scale pressurized laboratory tests were conducted on different rocks including limestone, sandstone and shale to develop and validate a new altered cutter geometry designed for carbonate applications. The main target of the simulations was optimizing the cutting action of the PDC cutter while drilling a carbonate formation. This resulted in development of altered cutter geometry designed for fracturing and shearing, offering improved effectiveness in medium to hard formations such as carbonates and clastic rock and more efficient cutting action than conventional round cutters. By creating subsurface cracks that propagate to the rock surface, the new cutter allows creation of thin and uncondensed cuttings, making an efficient use of energy. The first 12¼ in. 6 blades 16mm configuration bit equipped with the new cutter geometry in conjunction with a stiff rotary BHA was tested in a vertical exploratory well in Bahrah Field, North of Kuwait. The bit delivered improved performance by completing a total interval of 2,655 ft from 5,915 ft to 8,570 ft in 60 hrs resulting in 44.2 ft/hr rate of penetration while drilling from Mutriba to Burgan formations. The bit demonstrated excellent durability with a dull grade of 1-1-WT-A-X-I-NO-TD after drilling in a highly interbedded harsh application where the lithology consists mainly of limestone, shale & sandstone. The performance capability was further confirmed when the same bit drilled the second well to section TD completing a total interval of 2,630 ft with ROP of 68.7 ft/hr. achieving the top record run in north Kuwait vertical application in Bahrah field. The 12¼ in. bit with the non-planar cutters surpassed the average rate of penetration (ROP) for the same application in Bahrah Field by 76% saving the operator significant drilling time and making this bit design the top performing drill bit in the field. As a result of the continuous research and field testing, the new cutter technology has drilled more than 10 million feet globally proving its success and efficiency in a wide range of applications.

Shale stability and differential sticking are the main challenges while drilling through shale and sand sequences. Conventional mud systems cannot always provide the required wellbore stability and sustained high overbalance, which has led to an increase in use of ‘customized fluids’. Offset wells were reviewed to identify the issues while drilling this challenging trajectory through troublesome stressed Zubair shale and sand sequences. This review revealed serious well-bore instability, pack offs, differential stuck pipe leading to the loss of downhole tools and sidetrack operations. Traditionally, oil-based mud (OBM) have been used while drilling these formations with high NPT hours. Due to necessity of comingling two sections in a single section, it was necessary to identify a fluid's solution, which can provide good borehole stability. A customized drilling fluid system was designed by using deformable sealing polymer (DSP, deformable size) in conjunction with Synthetic Resilient Graphite and Sized Calcium Carbonate (CaCO3) in conventional OBM. These Nano particles effectively plug the pore throats and minimized the fluid invasion, which was confirmed by particle / permeability plugging tests under down hole conditions to overcome below challenges. Improve hole stability through stressed shale formationsMinimize risk of differential stuck pipe across low pore pressure formationsMitigate induced losses by utilizing unique wellbore-strengthening techniqueEnhance hole-cleaning efficiency at critical angle Drilling, logging, running and cementing liner was successfully completed in the commingle section without any incident. There was no NPT related to well-bore instability or differential sticking tendency reported. Very low torque and drag was observed in addition to enhanced well-bore cleaning in the high angle section. This paper will present the success of the deformable sealing polymer in OBM utilized to comingle Upper Zubair shale and Ratawi shale with case histories for reference.

GNE myopathy is a rare recessive myopathy caused by mutations in the GNE gene. It is mainly a distal myopathy with relative sparing of the quadriceps muscle.Patients with distal myopathies from Kuwait were examined and tested for the Middle Eastern GNE gene founder mutation, p.M743T. Patients were further studied for disease-associated features.GNE myopathy was confirmed in 14 of the 37 patients (37.8%) screened. All cases were caused by the p.M743T mutation. Age of onset and time from disease onset to loss of ambulation were variable. Both wasted and hypertrophied calf muscles were noted. Severely affected quadriceps were present in 1 patient, and ptosis, ophthalmoplegia, and tongue wasting in another.The scope of the p.M743T mutation now includes the Arabian Peninsula. Variations in age of onset, disease progression, and distribution in patients harboring the same mutation suggest the role of other genetic- and environment-modifying factors. Muscle Nerve 58: 700-707, 2018.

Strongyloides stercoralis is an intestinal nematode that causes chronic gastrointestinal infection. In immunosuppressed patients this persistent disease can lead to disseminated disease and/or hyperinfection that are life threatening conditions. We present a fatal case of S. stercoralis hyperinfection and the appropriate treatment for immunosuppressed patients is discussed., Strongyloides stercoralis je crijevna nematoda koja uzrokuje kroničnu gastrointestinalnu infekciju. Kod imunokompromitiranih bolesnika ova perzistentna bolest može dovesti do diseminirane bolesti i/ili hiperinfekcije koje su životno ugrožavajuće. Prikazujemo slučaj hiperinfekcije S. stercoralis sa smrtnim ishodom te odgovarajuće liječenje kod imunokompromitiranih bolesnika.

With the desired objective of increasing Oil production, the Operator initiated a high inclination well drilling campaign utilizing open hole completions with Inflow Control Device (ICD) screens in Burgan (sandstone) reservoirs. The approach dramatically reduces the effect of water and gas breakthrough, while optimizing production rates throughout the completion interval. Challenges encountered while drilling these high inclination wells included increased non-productive time resulting from interbedded formations with varying formation pressures, wellbore instability in the reactive, stressed shale sections and hole cleaning challenges. A non-aqueous reservoir drilling fluid (RDIF) system was customized with extensive laboratory testing to overcome the challenges and protect the reservoir from drilling fluid damage. The formation damage phenomena investigated included foreign particle invasion, formation clay swelling, chemical incompatibility, oil wetting of the reservoir rock, emulsion blocking and fluid invasion (water blocking). Based on the reservoir rock morphology and the calculated pore throat size distribution, the bridging particles type, size distribution, and concentration to be selected to rapidly establish a tight thin filter cake and prevent the invasion of filtrate and fine drilled solids deep into the formation to minimize damage to reservoir and avoid getting differential stuck pipe incident. Removal of skin damage resulting from external and internal filter cake deposition while drilling reservoir with invert emulsion fluid is vitally important to enhance production. The customized near-wellbore damage remediation system constructed around an in-situ acid precursor was designed to improve hydrocarbon recovery. This paper also summarizes engineering best practices developed while drilling, tripping and performing PST to achieve the operators well objectives. The lessons learned during these applications were incorporated into future wells to standardize operating procedures and improve field performance.

West Kuwait's 22-in. section comprises a vertical hole through 3,500 feet of interbedded carbonates varying significantly in compressive strength, and drilled commonly with minimal or no fluid returns. The section is typically drilled with roller-cone tungsten carbide insert (TCI) bits because large polycrystalline diamond compact (PDC) bits are extremely costly and require expensive performance motors to support their generated torque. PDC bits are also at risk of impact damage when drilling through the interbedded formations in this interval. Operators tend to apply higher drilling parameters while in the lower compressive strength intervals to achieve higher rates of penetration (ROP). Consequently, when the TCI bit enters the following harder formations with the same high operating parameters, it often suffers severe cutting structure damage. The result is reduced ROP. Greater weight on bit is then applied, causing further bit damage and possible sealed bearing failure. An engineering project was launched to develop a TCI bit specifically for the interbedded carbonates of this section. The primary challenges of the project were: Ensure the bit finishes the section in one run Improve dull condition of bit coming out of hole Surpass current field average ROP consistently Maintain efficient cleaning at lower flow rates for drilling in complete fluid-loss scenario Based on data and experience in drilling the application, an engineering process took place where several designs improvements with potential to improve performance were identified and trialled. Field engineers then worked onsite to identify how to drill the interval with optimal parameters for each sub-layer. The final design included: Specialized TCI cutting structure for carbonate drilling High impact-resistant insert geometry Simulated hydraulic efficiency to improve hole cleaning Improved high aspect ratio elastomer seals designed to endure longer runs Specialized tungsten carbide to improve cutting structure durability The engineering process yielded a design that successfully drills the complete section in one fast run - the fastest of the section - with an improved field average penetration rate to 63%, saving the operator more than 38% in associated cost for drilling the section. The application-engineered cutting structure enabled the use of lower drilling parameters than normal, thereby improving drilling efficiency and enhancing the post-drilling dull condition from the average of 3-3-BT to 1-2-WT. The paper shows a case study in Kuwait demonstrating the engineering and results of designing a TCI bit matched to application.

The drilling of development wells in layered sand-shale sequence involves thin and sinuous targets. Optimal well placement is a requirement for these thin reservoirs in order to drain them in a cost effective manner. A slanted well with 84 deg inclination was planned and drilled to drain oil from the Lower Cretaceous layered sands of target formation as part of a development plan to increase the production rate from the North Kuwait oil field which is aligned to Kuwait Oil Company's (KOC) goal of producing 4 million bbl/d oil by 2020 and sustained it until 2030. Plan is to build the inclination through the 12 ″ hole section kicking off with Motorized Rotary steerable system up to 54 deg inclination. The 8 ″ section is planned to build from 54 deg to 84 deg and again planned to be drilled with rotary steerable system and neutron, porosity technologies to allow precise landing with high angle in the required zone of interest. The 6 1/8″ section is planned to be drilled with Rotary steerable and triple combo Logging While Drilling (LWD) technologies to precisely drill through the required zone of interest. The well was planned to be drilled with Rotary steerable tools to enable smooth well profile and avoid micro doglegs to enable smooth deployment of ICD completions through difeerent layers - sand - shale - silt - shale sequences. After drilling the top hole curve sections, well was successfully landed into the target sand channel and drilled through the drain hole section using resistivity, gamma ray and density neutron tools. Well was monitored in real time with a multi task team comprising drilling department, field development, well placement and target depth was called out while it approached the expected zones with water fingering. After the completion of the 6 1/8″ reservoir section, achieving very smooth profile with pre - selected technologies, a dedicated cleanout run was performed to make sure that the hole profile is more precise and smoother for the deployment of ICD completions for the first time in a high angle deviated well crossing through different layers. After taking all the precautions related to hole cleaning, mud weight management to mitigate the shale sections open at high angles and well geometry, well was completed with ICD completions for the first time in Kuwait for a slanted 84 deg well within sand-shale sequence.

It is a challenge to drill in highly deviated or horizontal holes with high differential pressures. Wellbore instability, differential sticking and mud loss are frequently encountered problems while drilling slanted wells in Kuwait across shale and sand series. Drilling became more challenging with considerable non-productive time. Therefore, it is necessary to identify a fluids solution when other options with casing zone isolation are not viable. Traditionally, oil-based mud (OBM) was used while drilling these formations with limited success. A customized fluid system was designed to overcome the issue of high overburden pressure in shale and sand series formations targeting effective bridging, minimizing pore pressure transmission, and strengthening the wellbore. A nano-size deformable synthetic polymer, along with sized calcium carbonate and graphite, was identified to effectively plug the pore throats and minimize fluid invasion, which was confirmed by particle plugging tests. A well section was identified to comingle the highly depleted and pressurized formations. This was the first attempt on a high-angle well with development drilling operations in Kuwait and was performed to facilitate the successful drilling of the reservoir. Traditional OBM was converted to a customized fluid system using a nano-size polymer and sized bridging additives based on proprietary software selection and a series of laboratory tests. Drilling and logging were successfully performed for the first time in the commingled section without incident. There was no wellbore instability or differential sticking tendencies, less torque and drag, as well as enhanced wellbore cleaning in the high-angle sections. This paper also presents some successful applications of the nano-size deformable polymer in OBM to drill highly depleted formations in HTHP wells managing up to 3500 psi overbalalnce across highly permeable formations.

Charcot-Marie-Tooth disease type 4C (CMT4C) is an autosomal recessive demyelinating neuropathy associated with SH3TC2 mutations. More than 60 variants including nonsense, frameshift, and splice site variants have been reported in families of different ethnic origins as well as in sporadic patients. CMT4C is clinically characterised by early onset neuropathy, cranial nerve involvement and spine deformities. We present a family from Kuwait with a novel deletion of exons 13 and 14 in the SH3TC2 gene combined with a novel homozygous mutation in the DPYD gene. The 40 year-old male patient had foot deformities in infancy and delayed walking after the age of two. He first required walking aids when ten years old and became wheelchair-bound since the age of 18. He had progressive hearing loss over five years. Walking difficulties and wheelchair-dependency were reported in his father as well as a cousin of his mother while there were no symptoms reported in his own siblings and child. Clinical examination showed hypoacusis requiring the use of hearing aids, marked widespread symmetric muscular atrophies with weakness, and areflexia. He could walk a few steps with bilateral support. He had sensory neuropathy with skin atrophy and loss of hair on the lower legs. Spinal examination and X-ray showed slight hyperkyphosis of the thoracic spine but no signs of kyphoscoliosis. Electrophysiological studies showed severe motor and sensory neuropathy with very low amplitudes, markedly prolonged distal motor latencies and very slow motor nerve conduction velocities in the ulnar nerve. Needle electromyography detected fibrillations, positive sharp waves and complex repetitive discharges. High resolution sonography of the median nerve at the wrist showed a few enlarged fascicles with only moderately raised cross sectional area. Creatin kinase levels were constantly and significantly raised. Genetic testing revealed a homozygous large deletion in the SH3TC2 gene comprising exons 13 and 14 that had not been described before. Furthermore a second homozygous novel mutation (c.680+1G>T;p.?) was found in the DPYD gene. The same combination in heterozygous form was detected in the asymptomatic eight year old daughter. This newly described family with CMT4C broadens the spectrum of genetic causes and underlines the clinical variability of phenotypes as the absence of scoliosis does not exclude mutations in the SH3TC2 gene even in patients with severe disabling Azzedine et al., 2006 , Azzedine et al., 2016 , Varley et al., 2015 , Inherited Peripheral Neuropathies Mutation Database, 2016 .

Challenges of oil recovery in mature assets continue to increase, requiring horizontal wells to be drilled for longer intervals. To improve the overall production in Kuwait, horizontal injector wells are required in some carbonate reservoirs in north Kuwait fields with the main objective of driving reservoir pressure in cases where aquifers cannot contribute to sustained oil recovery. Drilling several injector wells with long lateral sections was found to be the best approach to improve reservoir sweeping efficiency and drive the pressure regime for sustaining higher production levels. Historically, all horizontal wells drilled in similar reservoirs utilized oil-based mud (OBM), which was instrumental in reducing torque and friction along the lateral sections. Recently, all injector wells in the area were switched to water-based mud (WBM) systems in the lateral to reduce reservoir damage and improve injectivity and to enable the use of microimaging logging tools while drilling. This switch, together with limited drilling rig capability and geological uncertainty, posed major challenges on the deliverability of the horizontal section to planned total depth (TD). The operator, in collaboration with the drilling services provider and other service providers, completed a substantial planning phase to optimize the well design and make it achievable using current resources. The bottomhole assembly (BHA) was modeled, with iterations made to enhance the capability of drilling long laterals with proper weight transfer without sacrificing well stability or directional control. To overcome the challenge of drilling the long lateral section without the need for intermediate trips, the tool string design was customized for additional robustness and durability. Completed in two runs, the 6979 ft section was considered to be the longest lateral in north Kuwait ever achieved at the time. Maintaining the well in the desired trajectory, the motorized rotary steerable system was used to achieve a rate of penetration (ROP) improvement above the field average and within the allowable torque limit permitted, reaching the required total depth successfully. The bit and BHA selection and design were both critical to success. The subject reservoir known for high rock stresses and varying local formation dip angles posed a challenge to maintain the well on the desired trajectory due to unpredictable changes in the BHA tendency. Rotary steerable system (RSS) automation through the use of closed loop and cruise control features helped minimize human intervention. These features enable the RSS to automatically react and change downhole settings to track target inclination. This paper discusses the planning, design and execution of the subject well, in addition to the added value and resulting improvement in reservoir sweeping efficiency.

Abstract An operators renewed focus on horizontal well drilling and open hole completions, using Inflow Control Device (ICD) screens, necessitated the use of oil-based drill-in fluids (DIF) to drill and complete their reservoir. The challenges were increased by low reservoir pressure conditions, increasing the risk of drilling fluid invasion and possible reservoir damage. Comprehensive laboratory studies were carried out to evaluate DIF performance and ensure understanding of the possible damage mechanisms produced while drilling, considering the reservoir characteristics and drilling conditions. The customized near-wellbore damage remediation system, with a delay-reaction, was designed based on Mesophase technology. This paper discusses detailed laboratory analysis for the clean-up system and its field applications in Kuwait horizontal wells. The applications included drilling carbonate and sandstone reservoirs, open hole ICD completion, and performing effective cleanup required for maximum production. The effectiveness of the Mesophase clean-up system to remediate reservoir damage and improve producibility was evaluated immediately after well kick off and again after steady production levels were reached. This paper shows the results obtained after the application of the near-wellbore remediation technology. The lessons learnt during the Mesophase application were incorporated on upcoming wells to standardize the operating procedures and improve field performance. Background To meet production targets from Raudhatain field, the operator initiated a horizontal well drilling campaign with open hole ICD completions in Mauddud (Carbonate) and Burgan (Sandstone) reservoirs. The ICD screens control flow rates across the completion for the entire length of the interval. This approach dramatically reduces the effect of water and gas breakthrough, while optimizing production rates across the full completion interval. Challenges encountered during drilling these horizontal wells included increased non-productive time resulting from interbedded formations with varying formation pressures, wellbore instability in the reactive and stressed shale sections and hole cleaning issues. An oil-based drill-In fluid system was designed with a high oil water ratio (OWR) to overcome these challenges and protect the reservoir from drilling fluid damage. The formation damage mechanisms analyzed included:Foreign particle invasionFormation clay swellingChemical incompatibilityOil wetting of the reservoir rockEmulsion blockingFluid invasion (Water Blocking)

This paper presents drilling and completion fluids design for drilling long lateral / horizontal wells in a North Kuwait field and its field application on well RA-AAA, RA-BBB, RA-CCC and RA-DDD. The offset wells were reviewed to identify the issues from drilling a challenging trajectory through troublesome reactive formations that showed serious wellbore stability issues and stuck pipe incidents. The customized drilling and completions fluids system was designed for different intervals, taking the following objectives in consideration: Improved hole stability through stressed and reactive formationsEnhanced hole-cleaning efficiency at critical anglesMinimized risk of stuck pipe across depleted formations with high porosity and permeabilityMinimized / no induced losses to formation by utilizing unique wellbore-strengthening techniqueMinimal damage to reservoir section during drilling phaseNear-wellbore damage remediation during completion phase This paper describes the customized drilling and completions fluids performance as compared to offset wells. A comprehensive engineered approach addressed the challenges of drilling horizontal wells by using a revolutionary bridging technology to strengthen the wellbore and improve wellbore stability to reduce non- productive time (NPT) related to losses, stuck pipe, etc. This paper also describes the completions fluids design to minimize reservoir damage and utilize Mesophase technology to remediate near-wellbore damage and improve reservoir producibility. The lessons learned on these wells were incorporated in drilling subsequent wells to continue improve on performance.

This paper presents drilling and completion fluids design for drilling long lateral / horizontal wells in a North Kuwait field and its field application on well RA-492, RA-493 and RA-499. The offset wells were reviewed to identify the issues from drilling a challenging trajectory through troublesome reactive formations that showed serious wellbore stability issues and stuck pipe incidents.The customized drilling and completions fluids system was designed for different intervals, taking the following objectives in consideration: Improved hole stability through stressed and reactive formationsEnhanced hole-cleaning efficiency at critical anglesMinimized risk of stuck pipe across depleted formations with high porosity and permeabilityMinimized / no induced losses to formation by utilizing unique wellbore-strengthening techniqueMinimal damage to reservoir section during drilling phaseNear-wellbore damage remediation during completion phaseThis paper describes the customized drilling and completions fluids performance as compared to offset wells. A comprehensive engineered approach addressed the challenges of drilling horizontal wells by using a revolutionary bridging technology to strengthen the wellbore and improve wellbore stability to reduce nonproductive time (NPT) related to losses, stuck pipe, etc. This paper also describes the completions fluids design to minimize reservoir damage and utilize Mesophase technology to remediate near-wellbore damage and improve reservoir producibility. The lessons learned on these wells were incorporated in drilling subsequent wells to continue improve on performance.

Kuwait Oil Company (KOC) is engaged in an early phase of development of a giant, tight, fractured carbonate play within the State of Kuwait, spread over a large area covering six fields. The producing reservoirs belong to the geological Formations of Toarcian to Tithonian age. Some reservoirs are characterized by very low porosity and permeability and productivity of these reservoirs is driven by the natural fracture system. This paper described the approach followed in developing a 3D fracture model for these reservoirs.Carefully planned data acquisition resulted in a rich suite of dataset consisting of image logs, conventional cores covering the target pay zones in a number of wells. Analysis of these data gave a clear understanding about fracture orientation, density, aperture, and other fracture parameters. Special 3D seismic processing was carried out to derive a volume curvature attribute, which was able to detect and identify the fracture corridors away from the wells. Structural geological analysis resulted in an understanding of the tectonic history of the area, which helped in genetically relating the identified fracture orientations with the structural evolution. A discrete fracture network was developed for these reservoirs combining the well and seismic attribute data. Parameters like aspect ratio, orientation and aperture of fractures was assigned to different fracture sets based on this analysis. The apertures were corrected for the present day stress effect based on the borehole breakout data. This fracture model was upscaled into the 3D geological model to get the fracture porosity and the permeability tensors. The fracture model was validated by history matching pressure build up and production data and was used for dynamic flow simulation studies for the field development planning.