No abstract

Hydraulic fracturing operations in unconventional reservoirs are typically monitored using geophones located either at the surface or in the adjacent wellbores. A new approach to record hydraulic stimulations uses fiber-optic distributed acoustic sensing (DAS). A fiber-optic cable was installed in a treatment well in the Meramec formation to monitor the hydraulic fracture stimulation of an unconventional reservoir. A variety of physical effects, such as temperature, strain, and microseismicity are measured and correlated with the treatment program during hydraulic fracturing of the well containing the fiber and also an adjacent well. The analysis of this DAS data set demonstrates that current fiber-optic technology provides enough sensitivity to detect a considerable number of microseismic events and that these events can be integrated with temperature and strain measurements for comprehensive hydraulic fracture monitoring.

Published case reports have documented the relationship between exenatide use and acute kidney injury. However, to our knowledge, no cases of this adverse effect with liraglutide, another glucagon-like peptide-1 receptor agonist approved for the treatment of type 2 diabetes mellitus, have been reported. We describe a 53-year-old Caucasian woman who came to a community hospital with severe and progressively worsening gastrointestinal symptoms for several weeks, leading to dehydration and development of acute kidney injury. Laboratory results showed an increase in her serum creatinine concentration to 22.8 mg/dl and blood urea nitrogen to 150 mg/dl; she also had lost 8.9 kg in the previous month. One month earlier, the patient had begun liraglutide 1.8 mg/day subcutaneously for uncontrolled type 2 diabetes. Use of the Naranjo adverse drug reaction probability scale indicated a possible relationship (score of 3) between the patient's development of acute kidney injury and liraglutide. Renal biopsy and laboratory testing were helpful in ruling out other potential causes of renal failure and adverse drug reactions due to other drugs such as ciprofloxacin and quinapril. After the reports of the renal biopsy were obtained, liraglutide was determined to be a likely cause of acute tubular necrosis. The patient was successfully treated with discontinuation of liraglutide, volume repletion, and hemodialysis. To our knowledge, this is the first documented case of liraglutide-induced acute tubular necrosis. Clinicians should be aware of this possible complication and closely follow liraglutide's dosage titration recommendations in the package insert. Patients should also be educated about the need to report unusual or prolonged gastrointestinal symptoms.

Hydraulic fracturing operations in unconventional reservoirs are monitored using distributed fiber-optic sensing through which physical effects such as temperature, strain, and microseismic activity can be measured. When combined with treatment curves and other reservoir information, these measurements give engineers more data to understand the effectiveness of a treatment program and make future reservoir management decisions. Distributed fiber-optic data are acquired within a borehole that is actively being fractured and is subsequently used as an observation well for treatments of a neighboring well. The large-aperture and finely sampled data acquisition provides a variety of measurements at different resolution scales as changes are induced in the reservoir. Distributed acoustic sensing microseismic events are observed with magnitudes above −2. The spatial distribution of events, up to 500 m from the observation well, allows us to estimate diffusivity and fracturing trends for nearby treatment wells. Microseismic events acquired using a standard three-component borehole tool provide insight into the type of events that can be observed only on one system or simultaneously on both systems. We correlate very low frequency (well below 1 Hz) strain-front behavior with the onset of microseismic events, as they are triggered by pore pressure and fracturing progress throughout the reservoir.