33 research outputs found
Numerical ModelâSoftware for Predicting Rock Formation FailureâTime Using Fracture Mechanics
Realâtime integrated drilling is an important practice for the upstream petroleum industry. Traditional
preâdrill models, tend to offset the data gathered from the field since information obtained prior to
spudding and drilling of new wells often become obsolete due to the changes in geology and geomechanics
of reservoirârocks or formations. Estimating the complicated nonâlinear failureâtime of a rock
formation is a difficult but important task that helps to mitigate the effects of rock failure when drilling
and producing wells from the subsurface. In this study, parameters that have the strongest impact on
rock failure were used to develop a numerical and computational model for evaluating wellbore
instability in terms of collapse, fracture, rock strength and failureâtime. This approach presents drilling
and well engineers with a better understanding of the fracture mechanics and rock strength failureprediction
procedure required to reduce stability problems by forecasting the rock/formation failuretime.
The computational technique built into the software, uses the stress distribution around a rock
formation as well as the rockâs responses to induced stress as a means of analyzing the failure time of
the rock. The results from simulation show that the applied stress has the most significant influence on
the failureâtime of the rock. The software also shows that the failureâtime varied over several orders of
magnitude for varying stressâloads. Thus, this will help drilling engineers avoid wellbore failure by
adjusting the stress concentration properly through altering the mud pressure and well orientation with
respect to inâsitu stresses. As observed from the simulation results for the failure time analysis, the
trend shows that the time dependent strength failure is not just a function of the applied stress.
Because, at applied stress of 6000â6050 psi there was time dependent failure whereas, at higher
applied stress of 6350â6400 psi there was no time dependent strength failure
A modified empirical criterion for strength of transversely anisotropic rocks with metamorphic origin
A modified empirical criterion is proposed to determine the strength of transversely anisotropic rocks. In this regard, mechanical properties of intact anisotropic slate obtained from three different districts of Iran were taken into consideration. Afterward, triaxial rock strength criterion introduced by Rafiai was modified for transversely anisotropic rocks. The criterion was modified by adding a new parameter α for taking the influence of strength anisotropy into consideration. The results obtained have shown that the parameter α can be considered as the strength reduction parameter due to rock anisotropy. The modified criterion was compared to the modified HoekâBrown (Saroglou and Tsiambaos) and Ramamurthy criteria for different anisotropic rocks. It was concluded that the criterion proposed in this paper is a more accurate and precise criterion in predicting the strength of anisotropic rocks
The performance of stochastic designs in wellbore drilling operations
© 2018, The Author(s). Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heterogeneity and sometimes unpredictable behaviour of underground systems increases the sensitivity of drilling activities. Quite often the operating parameters are set to certify effective and efficient working processes. However, failings in the management of drilling and operating conditions sometimes result in catastrophes such as well collapse or fluid loss. This study investigates the hypothesis that optimising drilling parameters, for instance mud pressure, is crucial if the margin of safe operating conditions is to be properly defined. This was conducted via two main stages: first a deterministic analysisâwhere the operating conditions are predicted by conventional modelling proceduresâand then a probabilistic analysis via stochastic simulationsâwhere a window of optimised operation conditions can be obtained. The outcome of additional stochastic analyses can be used to improve results derived from deterministic models. The incorporation of stochastic techniques in the evaluation of wellbore instability indicates that margins of the safe mud weight window are adjustable and can be extended considerably beyond the limits of deterministic predictions. The safe mud window is influenced and hence can also be amended based on the degree of uncertainty and the permissible level of confidence. The refinement of results from deterministic analyses by additional stochastic simulations is vital if a more accurate and reliable representation of safe in situ and operating conditions is to be obtained during wellbore operations.Published versio
Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes
Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy. We identified 45 individuals from 38 families across multiple ancestries carrying the nonsense c.757delG (p.Ala253GlnfsTer27) variant in SORD, in either a homozygous or compound heterozygous state. SORD is an enzyme that converts sorbitol into fructose in the two-step polyol pathway previously implicated in diabetic neuropathy. In patient-derived fibroblasts, we found a complete loss of SORD protein and increased intracellular sorbitol. Furthermore, the serum fasting sorbitol levels in patients were dramatically increased. In Drosophila, loss of SORD orthologs caused synaptic degeneration and progressive motor impairment. Reducing the polyol influx by treatment with aldose reductase inhibitors normalized intracellular sorbitol levels in patient-derived fibroblasts and in Drosophila, and also dramatically ameliorated motor and eye phenotypes. Together, these findings establish a novel and potentially treatable cause of neuropathy and may contribute to a better understanding of the pathophysiology of diabetes
Inter-seasonal compressed air energy storage using saline aquifers
Meeting inter-seasonal fluctuations in electricity production or demand in a system dominated by renewable energy requires the cheap, reliable and accessible storage of energy on a scale that is currently challenging to achieve. Commercially mature compressed-air energy storage could be applied to porous rocks in sedimentary basins worldwide, where legacy data from hydrocarbon exploration are available, and if geographically close to renewable energy sources. Here we present a modelling approach to predict the potential for compressed-air energy storage in porous rocks. By combining this with an extensive geological database, we provide a regional assessment of this potential for the United Kingdom. We find the potential storage capacity is equivalent to approximately 160% of the United Kingdomâs electricity consumption for January and February 2017 (77â96âTWh), with a roundtrip energy efficiency of 54â59%. This UK storage potential is achievable at costs in the range US$0.42â4.71âkWhâ1
Sitagliptin attenuates cardiomyopathy by modulating the JAK/STAT signaling pathway in experimental diabetic rats
Nouf M Al-Rasheed,1 Nawal M Al-Rasheed,1,2 Iman H Hasan,1 Maha A Al-Amin,1 Hanaa N Al-Ajmi,1 Ayman M Mahmoud3 1Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, 2Department of Pharmaceutical Sciences, College of Pharmacy, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia; 3Physiology Division, Department of Zoology, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt Abstract: Sitagliptin, a dipeptidyl peptidase-4 inhibitor, has been reported to promote cardioprotection in diabetic hearts by limiting hyperglycemia and hyperlipidemia. However, little is known about the involvement of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway modulation in the cardioprotective effects of sitagliptin. The current study aimed to investigate the protective effects of sitagliptin against diabetic cardiomyopathy (DCM), focusing on the modulation of the JAK/STAT pathway. Diabetes was induced by streptozotocin injection, and rats received sitagliptin orally and daily for 90 days. Diabetic rats exhibited hyperglycemia, hyperlipidemia, and a significant increase in heart-to-body weight (HW/BW) ratio. Serum troponin I and creatine kinase MB, cardiac interleukin-6 (IL-6), lipid peroxidation, and nitric oxide levels showed significant increase in diabetic rats. In contrast, both enzymatic and nonenzymatic antioxidant defenses were significantly declined in the heart of diabetic rats. Histopathological study revealed degenerations, increased collagen deposition in the heart of diabetic rats. Sitagliptin alleviated hyperglycemia, hyperlipidemia, HW/BW ratio, histological architecture, oxidative stress, and inflammation, and rejuvenated the antioxidant defenses. In addition, cardiac levels of pJAK2 and pSTAT3 were increased in diabetic rats, an effect which was remarkably decreased after sitagliptin treatment. In conclusion, these results confer an evidence that sitagliptin has great therapeutic potential on DCM through down-regulation of the JAK/STAT signaling pathway. Keywords: diabetic cardiomyopathy, DPP-4 inhibitors, JAK/STAT, oxidative stress, inflammatio