Estimation of Fracture Properties by Combining DAS and DTS Measurements

Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS) measurements during hydraulic fracturing treatments are used to estimate fluid volume distribution among perforation clusters. DAS is sensitive to the acoustic signal induced by fluid flow in the near-well region during pumping a stage, while DTS is sensitive to temperature variation caused by fluid flow inside the wellbore and in the reservoir. Raw acoustic signal has to be transferred to frequency band energy (FBE) which is defined as the integration of the squared raw measurements in each DAS channel location for a fixed period of time. In order to be used in further interpretation, FBE has to be averaged between several fiber-optic channels for each cluster on each time step. Based on this input, DAS allows us to consider fluid flow through perforation stage by stage during an injection period, and to evaluate the volume of fluid pumped in each cluster location as a function of time, and therefore to estimate the cumulative volume of fluid injected into each cluster. This procedure is based on a lab-derived and computational dynamics model confirmed correlation between the acoustic signal and the flow rate. At each time step, we apply the perforation/fracture noise correlation to determine the flow rate into each cluster, constrained by the requirement that the sum of the flow rates into individual clusters must equal the total injection rate at that time. On the other hand, the DTS interpretation method is based on the transient temperature behavior during the fracturing stimulation. During injection, the temperature of the reservoir surrounding the well is cooled by the injection fluid inside the well. After shut-in of stage pumping, temperature recovers at a rate depending on the injected volume of fluid at the location. The interpretation procedure is based on the temperature behavior during the warm-back period. This temperature distribution is obtained by solution of a coupled 3-D reservoir thermal model with 1-D wellbore thermal model iteratively. Once we confirm that the DAS and DTS interpretation methods provide comparable results of the fluid volume distribution, either of the interpretation results can be used as a known input parameter for the other interpretation method to estimate additional unknown such as one of the fracture properties. In this work, the injected fluid volume distribution obtained by the DAS interpretation is used as an input parameter for a forward model which computes the temperature profile in the reservoir. By conducting temperature inversion to reproduce the temperature profile that matches the measured temperature with the fixed injection rate for each cluster, we can predict distribution of injected fluid for hydraulic fractures along a wellbore. The temperature inversion shows that multiple fractures are created in a swarm pattern from each perforation cluster with a much tighter spacing than the cluster spacing. The field data from MIP-3H provided by the Marcellus Shale Energy and Environmental Laboratory is used to demonstrate the DAS/DTS integrated interpretation method. This approach can be a valuable means to evaluate the fracturing treatment design and further understand the field observation of hydraulic fractures.

The circulating renin-angiotensin-aldosterone system is down-regulated in dogs with glomerular diseases compared to other chronic kidney diseases with low-grade proteinuria

Glomerular diseases (GD) lead to a variety of disorders of the vascular and the total body water volumes. Various pathomechanisms, including vascular underfill and overfill, have been suggested to explain these disturbances. Accordingly, the circulating renin-angiotensin-aldosterone system (cRAAS) is expected to be activated as either a cause or a result of these fluid disorders. The aim of this study was to characterize the activity of the cRAAS in dogs with GD and to evaluate its relationship with the vascular volume status. In a prospective study, we evaluated the plasma renin activity and the serum aldosterone concentration in 15 dogs with GD. Their fluid volume status was estimated with clinical variables reflecting volemia and hydration, echocardiographic volume assessment, N-terminal pro B-type natriuretic peptide, blood urea nitrogen:creatinine ratio, and the urinary fractional excretion of sodium. Ten dogs with chronic kidney disease (CKD) with matching degree of azotemia were recruited as controls. The activity of the cRAAS was low in 10 dogs, normal in 3 dogs, high in 1 dog and equivocal (high renin—low aldosterone) in 1 dog with GD. These dogs had a lower cRAAS activity than dogs with CKD (p = 0.01). The clinical evaluation showed 8 hypovolemic and 7 non-hypovolemic dogs; 3 dehydrated, 9 euhydrated and 3 overhydrated dogs. The cRAAS activity was not different between hypovolemic and non-hypovolemic dogs. The down-regulated cRAAS without obvious association with the clinical volume status of these dogs with GD, suggests different mechanisms of fluid volume dysregulation in dogs with GD than previously assumed. This finding however should be confirmed in a focused larger scale study, as it may influence the use of cRAAS blockers as part of the standard therapy of GD in dogs.

Tribological properties of rock-bit journal bearings tribo-pair with micro-dimples under contaminated grease lubrication

The failure of bit bearings is one of the main factors that restrict the life of a bit, and studies revealed that sealing and adhesive wear failure are common failure modes of bit bearings. To study the adaptability of the optimal textures to anti-wear and anti-friction performance of an 8 1/2” rock bit journal bearingunder sealing leakage conditions, the rheological properties of grease in the range of 0%–50% of the water-based drilling fluid volume in the compound lithium-based grease (rock bit grease) were tested. For the cylindrical dimples (diameter: 300 μm; depth: 40 μm, area ratio: 5%) and elliptical dimples (major and minor axis of 720 and 360 μm, respectively; depth: 40 μm, area ratio: 10%), the experimental study on the wear resistance of the optimized texture tribo-pairs was carried out as the grease invaded different drilling fluid contents based on the pin-disk pair. Results showed that the drilling fluid volume in the rock bit grease significantly affected the rheological properties of the grease. Furthermore, the cylindrical and elliptical dimples still had good anti-wear and anti-friction effects. Especially when the drilling fluid volume ratios in the grease reached 50%, the elliptical dimples can still reduce the friction coefficient and wear amount of the pair by 19.88% and 56.99%, respectively. With the increase of drilling fluid invasion into grease, the wear morphology of the un-textured tribo-pairs showed that the wear form changed from abrasive to adhesive wear, while that of the preferred textured tribo-pairs indicated slight abrasive wear.

A Computational Analysis for Active Flow and Pressure Control Using Moving Roller Peristalsis

Peristaltic motion arises in many physiological, medical, pharmaceutical and industrial processes. Control of the fluid volume rate and pressure is crucial for pumping applications, such as the infusion of intravenous liquid drugs, blood transportation, etc. In this study, a simulation of peristaltic flow is presented in which occlusion is imposed by pairs of circular rollers that squeeze a deformable channel connected to a reservoir with constant fluid pressure. Naturally, this kind of flow is laminar; hence, the computation occurred in this context. The effect of the number and speed of the pairs of rollers, as well as that of the intrapair roller gap, is investigated. Non-Newtonian fluids are considered, and the effect of the shear-thinning behavior degree is examined. The volumetric flow rate is found to increase with an increase in the number of rollers or in the relative occlusion. A reduction in the Bird–Carreau power index resulted in a small reduction in transport efficiency. The characteristic of the pumping was computed, i.e., the induced pressure as a function of the fluid volume rate. A strong positive correlation exists between relative occlusion and induced pressure. Shear-thinning behavior significantly decreases the developed pressure compared to Newtonian fluids. The immersed boundary method on curvilinear coordinates is adapted and validated for non-Newtonian fluids.

Delirium in Acute Poisoning with 1,4-Butanediol and Its Correction

Delirium complicating regular use of psychoactive substances remains one of the major issues of critical care, toxicology, and psychiatry. However, the pathogenetic mechanisms of delirium development in patients with 1,4-butanediol poisoning have been poorly studied until now.The aim of the study was to reveal specific patterns of delirium in patients with 1,4-butanediol poisoning as well as to study the changes in systemic hemodynamic parameters, respiratory function, and body fluid compartments during the treatment.Material and methods. The study was prospective and treatment-randomized. Forty-eight male patients aged 20 to 45 years with delirium and acute 1,4-butanediol poisoning were enrolled. Of them, 24 patients were administered with succinate-containing drug 40 ml daily, 24 patients received standard treatment without antihypoxic agents. We studied the evolution of delirium, changes in anaerobic metabolism parameters, systemic hemodynamics, respiratory function, and the volume of fluid compartments. Impedance measurement method adjusted for interference was used in the study.Results. At the «peak» of delirium (days 1–3), the hyperdynamic circulation, increased systemic arterial tone, stroke output, respiratory function parameters, and metabolic lactate acidosis were recorded. A decrease in total fluid volume and extracellular fluid volume was clearly observed during day 1 of intoxication delirium along with increased permeability of cell membranes. On day 3 of delirium, a decrease in intracellular fluid volume and increase in extracellular fluid volume were noted. After the cytoflavin administration, shorter delirium duration (7.5 [6; 8] days), more rapid correction of lactate acidosis, stabilization of respiratory parameters and stabilization of cell membrane permeability by day 5 were found. In the control group, delirium persisted for up to 14 [11; 15] days (z=-5.9; P=0.00011) with more frequent development of complications such as nosocomial pneumonia (χ2=8.4, P<0.001).Conclusion. The severity of delirium in acute poisoning with 1,4-butanediol was associated with metabolic lactate acidosis, changes in systemic hemodynamics and pulmonary function. A positive effect of adjunctive antihypoxic therapy with succinate-containing agent on cardio-respiratory parameters, cell membrane permeability, water balance due to elimination of tissue hypoxia and prompt switching to tissue aerobic metabolism has been found.

Prospective comparison of the effects of intraoperative goal-directed fluid therapy and restrictive fluid therapy on complications in thoracoscopic lobectomy

Objective Restrictive fluid therapy is recommended in thoracoscopic lobectomy to reduce postoperative pulmonary complications, but it may contribute to hypovolemia. Goal-directed fluid therapy (GDFT) regulates fluid infusion to an amount required to avoid dehydration. We compared the effects of GDFT versus restrictive fluid therapy on postoperative complications after thoracoscopic lobectomy. Methods In total, 124 patients who underwent thoracoscopic lobectomy were randomized into the GDFT group (group G, n = 62) or restrictive fluid therapy group (group R, n = 62). The fluid volume and postoperative complications within 30 days of surgery were recorded. Results The total fluid volume in groups G and R was 1332 ± 364 and 1178 ± 278 mL, respectively. Group R received a smaller colloid fluid volume (523 ± 120 vs. 686 ± 180 mL), had a smaller urine output (448 ± 98 vs. 491 ± 101 mL), and received more norepinephrine (120 ± 66 vs. 4 ± 18 µg) than group G. However, there were no significant differences in postoperative pulmonary complications, acute kidney injury, length of hospital stay, or in-hospital mortality between the two groups. Conclusion Restrictive fluid therapy performs similarly to GDFT in thoracoscopic lobectomy but is a simpler fluid strategy than GDFT. Trial registration: This study has been registered at the Chinese Clinical Trial Registry (ChiCTR2100051339) ( http://www.chictr.org.cn/index.aspx ).