bluuebunny/crossref_metadata_2025_split huggingface dataset:
Underbalanced Drilling Operation for Reservoir Characterization in Jebel Aswad Field, Oman - A Case History
Authors: Nellayappan Karthik , Azzam Zaher , Vieira Paco , Rambo Dean , Moyse Keith , Cook Iain , Kelly Jim , Hengveld Bas 
Published: January 2008

Abstract
Underbalanced (UBD) operations are being utilized with increasing frequency as a means of reducing invasive formation damage, minimizing problems with differential sticking, lost circulation, and increasing rates of penetration in many drilling operations. Additional to the operational benefits, the underbalanced drilling technology is nowadays utilized as a tool formation characterization associated with the reservoir fluids.
Tethys Oil Oman Ltd. has successfully drilled the first underbalanced well, Jebel Aswad 1 in Jebel Aswad field in Block 15. Two lateral re-entry wells were drilled, STK1 & STK2 into Shuaiba and Natih reservoir respectively, using Underbalanced drilling technique. The shuaiba reservoir is composed primarily of micritic lime mudstone, which generally has a moderate to good porosity with poor permeability. The Natih reservoir is a fractured chalky limestone with a predominantly low permeability matrix. The main objective was to drill 6-1/8" hole into the horizontal reservoir sections in underbalance condition to reduce/minimize formation damage and to evaluate production while drilling. Drilling the reservoir in underbalanced mode allowed for an early reservoir characterization.
This paper discusses the objectives, planning, drilling technology used, problems encountered and lessons learned during the first application of Underbalanced Drilling in Jebel Aswad field for Tethy Oil Oman Ltd.
Simplifying MPD: Lessons Learned
Authors: Medley George H. , Moore Dennis , Nauduri Sagar 
Published: January 2008

Abstract
Managed Pressure Drilling has gained widespread popularity and a great deal of press coverage in recent years. By applying MPD techniques, it is possible to drill holes that simultaneously expose formations with pore pressures very close to the frac pressures of other exposed formations with minimal formation influx or mud losses. Complex and expensive systems have been designed and implemented to maintain pressure on the wellbore using hydraulics modeling software, automated chokes, and continuous surface circulating systems, often working in conjunction with each other. These systems usually require several specially trained operators. This aggregation of personnel and equipment increases both the footprint and housing required for implementation, as well as substantially increasing the cost of the operation.
MPD replaces the pressure exerted by static mud weight with dynamic friction pressure to maintain control of the well without losing returns. The objective of the technique is to maintain wellbore pressure between the pore pressure of the highest pressured formation and the frac pressure of the weakest. This is usually done by drilling with a mud weight whose hydrostatic gradient is less than what is required to balance the highest pore pressure, with the difference made up using dynamic friction while circulating. That sounds quite simple but has been made extremely complicated.
The big problem is maintaining constant wellbore pressure while transitioning between circulating with little or no annular pressure and shut-in with proper annular pressure to maintain balance. A great deal of time and money has gone into trying to do this with no change in wellbore pressure throughout the process. Field experience has shown that this is not necessarily cost effective, demanding an answer to the question, "Is all this complexity really necessary?" The answer in many cases is "No."
First Multilateral Well Drilled With Underbalanced Drilling Technology in Sabria Field—Tunisia
Authors: McMechan Roger , Beaudry Julien , Beaudry Raymond , Arnone Maurizio , Al Heureithi Wesam , Vieira Paco , Chopty James 
Published: January 2008

Abstract
Underbalanced Drilling (UBD) technology has been applied around the world to drill wells where it is imperative to obtain benefits, as it minimizes the formation damage that is common result in conventional overbalanced drilling operations. In addition to minimizing formation damage, other benefits related to Underbalanced Drilling include increase of penetration rate, elimination of lost circulation problems, elimination of differential pipe sticking and reservoir evaluation while the well is being drilled.
The reservoir screening analysis and the engineering feasibility study performed during the planning stage of this project determined that the Hamra reservoir is a good candidate for underbalanced drilling technology application.
Based on the reservoir pressure and the Lower Hamra formation depth in the Sabria field, a weighted drilling fluid system was required to achieve a controlled drawdown and therefore underbalanced drilling conditions. Comprehensive hydraulic simulations were carried out to determine the required liquid injection rate and back pressure on the choke manifold to ensure safe and manageable drilling conditions. The simulations were also used to predict the anticipated hole cleaning and the impact of reservoir production due to downhole hydraulic conditions while drilling.
Drilling the Multilateral Well A in underbalanced condition allowed Winstar Resources Ltd to evaluate the reservoir and successfully acquire real time reservoir characterization data and production capability of the well while drilling.
A multidisciplinary team contributed to the engineering, planning and execution of the Underbalanced Drilling operation. This paper discusses the planning phase, operational results, lessons learned and recommendations that will permit to improve the UBD benefits for future wells to be drilled in the area.
Performing the Dynamic Shut-In Procedure Because of a Kick Incident When Using Automatic Coordinated Control of Pump Rates and Choke-Valve Opening
Authors: Carlsen Liv A. , Nygaard Gerhard , Gravdal Jan Einar , Nikolaou Michael , Schubert Jerome 
Published: January 2008

Abstract
Automatic drilling operations using different Managed Pressure Drilling (MPD) technologies such as annulus backpressure systems or dual-gradient systems require investigation of the system's ability to operate during various kick incidents. Due to the increased instrumentation typically available in MPD operations, kick incidents can be identified earlier compared to more traditional methods using evaluation of the pit gain. Since early kick detection is possible, the use of new well shut-in procedures such as the dynamic shut-in procedure will probably be accepted as more appropriate during MPD operations. This paper describes how the dynamic shut-in procedure can be performed during a kick incident occurring during drilling.
The main pumps and the choke valve opening are operated using the automatic coordinated control system. The dynamic shut-in procedure is evaluated using a detailed dynamic multi-phase flow model, and the case used for the evaluation is based on the requirements from an off-shore drilling operation of a well in the North Sea. The dynamic shut-in procedure is followed by a procedure using the automatic coordinated control system to displace the kick, and the procedure is compared to both Driller's Method and the Wait and Weight method.
The results show that using the dynamic shut-in procedure together with the automatic coordinated control system reduces the time needed to establish control of the well as compared to the more traditional well control procedures. The results also indicate that introducing the dynamic shut-in procedure reduces the total risk for the whole drilling operation.
Modeling of an Underbalanced Drilling Operation Utilizing Supercritical Carbon Dioxide
Authors: Al-Adwani Faisal , Langlinais Julius P. , Hughes Richard 
Published: January 2008

Abstract
Mechanistic modeling of an underbalanced drilling operation using carbon dioxide has been developed in this research. The use of carbon dioxide in an underbalanced drilling operation eliminates some of the operational difficulties inherent with gaseous drilling fluids, such as generating enough torque to run a downhole motor. The unique properties of CO2, both inside the drill pipe and the annulus are shown in terms of optimizing the drilling operation by achieving a low bottom hole pressure window. Typically, CO2 becomes supercritical inside the drill pipe at this high density; it thus can generate enough torque to run a downhole motor. As the fluid exits the drill bit it will evaporate to a gas, hence achieving the required low density for underbalanced drilling.
The latest CO2 equation of state to calculate the required thermodynamic fluid properties is used. In addition, a heat transfer model that takes into account varying properties of both pressure and temperature has been developed. A marching algorithm procedure is developed to calculate the circulating fluid pressure and temperature, taking into account the varying parameters. Both single phase CO2 and a mixture of CO2 and water have been studied to show the effect of produced water on corrosion rates. The model also is capable of handling different drill pipe and annular geometries.
Applying Underbalanced Drilling Technology Improves Productivity and Enhances Recovery in Libya
Authors: Gaaim A. M. , Qutob Hani 
Published: January 2008

Abstract
Recent trends in the Oil & Gas industry have been toward the utilization of new technologies in order to optimize production and improve recovery. The National Oil Corporation (NOC) of Libya is considering deploying Under-balanced Drilling (UBD) technology as one of the most effective methods when it is effectively applied in conjunction with horizontal and/or Multi-lateral well drilling and completion techniques
Under-Balanced Drilling Technology has enabled the commercial development of numerous oil and gas reservoirs around the world that would have otherwise not been exploited due to technical and/or economic limitations. Under-Balanced Drilling has only become possible as a result of the integration of many developing technologies that facilitate directional control of the well trajectory, control of the bottom hole circulating pressure and the safe handling of drilling fluids and drill cuttings on surface.
When drilling Under-balanced, the annular pressure profile is maintained below the expected reservoir pore pressure and is particularly beneficial in evaluating the productivity of prospective formations in their virgin state. This means that the formation can be evaluated without being subjected to damage during conventional drilling and the required clean-up operations.
As of today, a total of three wells have been drilled under-balanced by ZUEITINA Oil Company in Libya. Through three examples, the paper will demonstrate that the key to selecting appropriate Reservoir candidates for UBD is achieving a balance of Technical, Safety and Economic factors.
This paper describes the Front End Engineering Design, Project Management, Risk Mitigation, Operational Results and Lessons Learned for this project.
Managed-Pressure Drilling and Downhole Isolation Technologies Deliver High Rate Gas Wells
Authors: Dharma Nyoman , Toralde J. S. S. 
Published: January 2008

Abstract
Pressurized MudCap Drilling (PMCD), a variant of Managed Pressure Drilling (MPD), is known for allowing drilling to continue despite a total loss of circulation, while at the same time monitoring and controlling the entry of influx into the wellbore. A weakness of this technique is that the well still has to be killed prior to pulling out of the hole, which can be timeconsuming and ultimately lead to reservoir damage. Utilizing a downhole isolation system to eliminate the need to kill the well during and after PMCD operations would therefore greatly improve the efficiency and effectiveness of this drilling technique and enhance its acceptability in operations where well productivity is a major consideration.
A combination of MPD and downhole isolation technologies was recently used successfully to drill a highly prolific, fractured gas reservoir in Suban Field, South Sumatra, Indonesia, resulting in wells capable of producing in excess of 300 mmscfd. MPD with downhole isolation allowed drilling to continue even with total loss of circulation, increased the safety margin of operations, reduced the amount of mud and lost circulation materials (LCM) required, minimized formation damage and made the running and installation of the completion assembly possible without the need to kill the well. The project demonstrated the clear and practical advantage that can be gained from combining these two technologies.
This paper focuses on how MPD and downhole isolation technologies were successfully integrated to produce high-rate gas wells in the Suban field and details how the system was effectively utilized for the first time to produce improvements in the safety and efficiency of drilling and completion operations, as compared to previous methods used in the area. It will also present the equipment, set-up, processes and procedures used in integrating these two technologies.
Resting Heart Rate in Middle Age and Diabetes Development in Older Age
Authors: Carnethon Mercedes R. , Yan Lijing , Greenland Philip , Garside Daniel B. , Dyer Alan R. , Metzger Boyd , Daviglus Martha L. 
Published: January 2008

OBJECTIVE—Based on prior research showing inverse associations between heart rate and life expectancy, we tested the hypothesis that adults with higher resting heart rate in middle age were more likely to have diagnosed diabetes or to experience diabetes mortality in older age (&gt;65 years).
RESEARCH DESIGN AND METHODS—Resting heart rate was measured at baseline (1967–1973) in the Chicago Heart Association Detection Project in Industry. We used Medicare billing records to identify diabetes-related hospital claims and non–hospital-based diabetes expenses from 1992 to 2002 in 14,992 participants aged 35–64 years who were free from diabetes at baseline. Diabetes-related mortality was determined from 1984 to 2002 using National Death Index codes 250.XX (ICD-8 and -9) and E10–E14 (ICD-10).
RESULTS—After age 65, 1,877 participants had diabetes-related hospital claims and 410 participants had any mention of diabetes on their death certificate. The adjusted (demographic characteristics, cigarette smoking, and years of Medicare eligibility) odds of having a diabetes-related claim was ∼10% higher (odds ratio [OR] 1.10 [95% CI 1.05–1.16]) per 12 bpm higher baseline heart rate. Following adjustment for BMI and postload glucose at baseline, the association attenuated to nonsignificance. Higher heart rate was associated with diabetes mortality in adults aged 35–49 years at baseline following adjustment for postload glucose and BMI (1.21 [1.03–1.41]).
CONCLUSIONS—Higher resting heart rate is associated with diabetes claims and mortality in older age and is only due in part to BMI and concurrently measured glucose.
Transplant Estimated Function
Authors: Caumo Andrea , Maffi Paola , Nano Rita , Bertuzzi Federico , Luzi Livio , Secchi Antonio , Bonifacio Ezio , Piemonti Lorenzo 
Published: January 2008

OBJECTIVE—The β-score is a highly regarded approach to the assessment of transplant functionality. Our aim was to develop an index of β-cell function that hinges on the pillars of the β-score (daily insulin requirement and A1C), has a straightforward physiological interpretation, and does not require the execution of an insulin stimulation test.
RESEARCH DESIGN AND METHODS—The new index is denoted transplant estimated function (TEF) and is obtained from the daily insulin requirement and A1C. TEF estimates the amount of insulin secreted daily and can be normalized to the number of transplanted islets, thus permitting evaluation of the cost-effectiveness of the transplant. TEF was compared with the area under the curve of C-peptide [AUC(C-pep)] concentration over 24 h, as well as the acute insulin response to intravenous glucose (AIRglu) and to arginine (AIRarg). The association between TEF and β-score was also investigated.
RESULTS—The correlation of TEF with 24-h AUC(C-pep) was r = 0.73 (P &lt; 0.005), whereas that for β-score versus 24-h AUC(C-pep) was r = 0.33 (NS). The correlation of TEF with AIRglu was r = 0.59 (P &lt; 0.001) and close to that for β-score versus AIRglu (r = 0.65, P &lt; 0.001). The correlation of TEF with AIRarg was r = 0.33 (P &lt; 0.005) and was similar to that for β-score versus AIRarg (r = 0.34, P &lt; 0.005). TEF and β-score were correlated well (r = 0.69, P &lt; 0.0001) and showed similar time profiles.
CONCLUSIONS—TEF estimates daily insulin secretion, it is simpler than the β-score, and its performance against reference indexes of β-cell secretion is in line with that exhibited by β-score. TEF can be normalized to the number of transplanted islets and thereby provides a benchmarking tool to evaluate the cost-effectiveness of the transplant.
Pancreatic Exocrine Dysfunction in Maturity-Onset Diabetes of the Young Type 3
Authors: Vesterhus Mette , Ræder Helge , Johansson Stefan , Molven Anders , Njølstad Pål R. 
Published: January 2008

OBJECTIVE—Exocrine pancreas dysfunction is seen in 10–30% of patients with type 1 and 2 diabetes. We have recently identified a syndrome of diabetes and exocrine pancreas dysfunction attributable to mutations in the carboxyl ester lipase (CEL) gene. We wanted to investigate the prevalence of pancreatic exocrine dysfunction in patients with maturity-onset diabetes of the young type 3 (MODY3).
RESEARCH DESIGN AND METHODS—All 119 patients with MODY3 in the Norwegian MODY Registry were invited to participate, and 70 (60.5%) responded, among whom 63 were adults. Control groups included 140 subjects with type 1 diabetes and 78 nondiabetic control subjects. Pancreatic dysfunction was defined by fecal elastase deficiency. Fecal fat excretion was measured in 25 patients with fecal elastase deficiency. CEL was investigated for sequence changes.
RESULTS—We found a prevalence of fecal elastase deficiency of 12.7% in adult patients with MODY3, compared with 18.6% in patients with type 1 diabetes and 3.8% in nondiabetic control subjects. The six patients with MODY3 with fecal elastase deficiency available for analysis all had increased fecal fat excretion. Fecal elastase decreased with age. Controlled for age, patients with MODY3 still had decreased fecal elastase compared with control subjects. Twelve of 70 patients (17%) had single-base insertions in CEL exon 11. Two of these had fecal elastase deficiency.
CONCLUSIONS—The prevalence of pancreatic exocrine dysfunction was 12.7% in a cohort of 63 adult patients with MODY3, similar to the prevalence among type 1 diabetic patients. Fecal fat excretion was increased in all patients with MODY3 with fecal elastase deficiency who were investigated, underscoring the potential clinical importance of the exocrine dysfunction.
Race/Ethnicity and Economic Differences in Cost-Related Medication Underuse Among Insured Adults With Diabetes
Authors: Tseng Chien-Wen , Tierney Edward F. , Gerzoff Robert B. , Dudley R. Adams , Waitzfelder Beth , Ackermann Ronald T. , Karter Andrew J. , Piette John , Crosson Jesse C. , Ngo-Metzger Quyen , Chung Richard , Mangione Carol M. 
Published: January 2008

OBJECTIVE—To examine racial/ethnic and economic variation in cost-related medication underuse among insured adults with diabetes.
RESEARCH DESIGN AND METHODS—We surveyed 5,086 participants from the multicenter Translating Research Into Action for Diabetes Study. Respondents reported whether they used less medication because of cost in the past 12 months. We examined unadjusted and adjusted rates of cost-related medication underuse, using hierarchical regression, to determine whether race/ethnicity differences still existed after accounting for economic, health, and other demographic variables.
RESULTS—Participants were 48% white, 14% African American, 14% Latino, 15% Asian/Pacific Islander, and 8% other. Overall, 14% reported cost-related medication underuse. Unadjusted rates were highest for Latinos (23%) and African Americans (17%) compared with whites (13%), Asian/Pacific Islanders (11%), and others (15%). In multivariate analyses, race/ethnicity significantly predicted cost-related medication underuse (P = 0.048). However, adjusted rates were only slightly higher for Latinos (14%) than whites (10%) (P = 0.026) and were not significantly different for African Americans (11%), Asian/Pacific Islanders (7%), and others (11%). Income and out-of-pocket drug costs showed the greatest differences in adjusted rates of cost-related medication underuse (15 vs. 5% for participants with income ≤$25,000 vs. &gt;$50,000 and 24 vs. 7% for participants with out-of-pocket costs &gt;$150 per month vs. ≤$50 per month.
CONCLUSIONS—One in seven participants reported cost-related medication underuse. Rates were highest among African Americans and Latinos but were related to lower incomes and higher out-of-pocket drug costs in these groups. Interventions to decrease racial/ethnic disparities in cost-related medication underuse should focus on decreasing financial barriers to medications.
A Randomized Trial Comparing Continuous Subcutaneous Insulin Infusion of Insulin Aspart Versus Insulin Lispro in Children and Adolescents With Type 1 Diabetes
Authors: Weinzimer Stuart A. , Ternand Christine , Howard Campbell , Chang Cheng-Tao , Becker Dorothy J. , Laffel Lori M.B. ,   for the Insulin Aspart Pediatric Pump Study Group
Published: January 2008

OBJECTIVE—The safety and efficacy of insulin aspart continuous subcutaneous insulin infusion (CSII) was compared with that of insulin lispro CSII in children and adolescents with type 1 diabetes.
RESEARCH DESIGN AND METHODS—Children and adolescents aged 4–18 years with diagnosed type 1 diabetes ≥1 year previously and treated with insulin analog in a CSII ≥3 months were randomly assigned 2:1 to 16 weeks of insulin aspart CSII (n = 198) or insulin lispro CSII (n = 100) in this open-label, parallel-group, multicenter study. Standard diabetes safety and efficacy parameters were assessed.
RESULTS—Baseline demographics, subject characteristics, and diabetes history were similar between treatment groups. After 16 weeks of treatment, insulin aspart CSII was noninferior to insulin lispro CSII as measured by change in A1C from baseline (aspart, −0.15 ± 0.05%; lispro, −0.05 ± 0.07% [95% CI of the treatment difference −0.27 to 0.07]; P = 0.241). No significant differences between treatment groups were observed in fasting plasma glucose, hyperglycemia, and rates of hypoglycemic episodes. At week 16, 59.7% of subjects in the aspart group and 43.8% of subjects in the lispro groups achieved age-specific American Diabetes Association A1C goals (&lt;8.5% for subjects aged &lt;6 years; &lt;8% for subjects aged 6–18 years) (P = 0.040, corrected for baseline). Daily insulin dose (units per kilogram) was significantly lower at week 16 for subjects treated with aspart compared with those treated with lispro (0.86 ± 0.237 vs. 0.94 ± 0.233, P = 0.018).
CONCLUSIONS—Insulin aspart was as safe and effective as insulin lispro for use in a CSII in children and adolescents with type 1 diabetes.