Perforation Cavity Research Articles

An experimental study on evolution of vortex structures in perforated cavity structures driven by acoustic waves

In the present study, the vortex dynamics in three perforated cavity structures with different gap distances (l/d = 2, 4, 6) subjected to acoustic waves is investigated by particle image velocimetry (PIV) experiments. First, using a data-acquisition at 48 kHz and transfer function method, the incident acoustic waves of three perforated cavity structures at different frequency was examined. The relationship between the gap distances and the acoustic-vortex coupling phenomena was obtained. Then, PIV was carried out to obtain the flow fields and vortex evolution process in three perforated cavity resonators at specific frequency. Comparisons of different gap distances showed that the vortices generated by turbulent entrainment are confined at the corner in the small gap distances (l/d = 2, 4). For larger gap distance (l/d = 6), large-scale vortices occur due to the wall jet flow. Finally, the flow fields were analyzed by turbulent kinetic energy to obtain the dominant energy distribution and illustrate the energy conversion process.

Productivity Decline Mechanisms in Gravel Packed Perforations

In a cased hole gravel pack completion, perforations are packed with proppant to both mechanically support the perforation cavity, and to filter any produced sand before it reaches the surface. Poor perforation packing sometimes occurs in which the perforation is partially or completely unsupported, leading to earlier productivity reduction than in cases of good packing. We investigated productivity reduction and the associated mechanisms in a series of hollow cylinder experiments on outcrop and field cores with varying proppant packing. Packed perforations maintained significantly higher productivity than unsupported perforations by preventing macroscopic shear failure around the cavity and erosion due to sand production. Partial packing may in some instances maintain productivity almost as well as complete packing, but this likely depends on perforation orientation. Compaction tests and numerical simulations suggest that compaction failure is unlikely at the cavity wall in the current experiments, and that proppant-formation interface damage or proppant filtering of produced sand are more probable explanations for the productivity reduction seen in packed perforations.

Numerical simulations of sand production in oil wells using the CFD-DEM-IBM approach

Three-dimensional CFD-DEM-IBM simulations of sand production in a sandstone formation, using periodic boundaries, were performed using 10000 frictional elastic spheres bonded together and compressed at 1 MPa of overburden pressure. Sand production simulation geometry and procedures are proposed, in which the cone penetration test (CPT) has been used to investigate the physical perforation penetration of the cemented sandstone material with the real-world grain size distribution from the Ustyurt-Buzachi Sedimentary Basin. The Immersed Boundary Method (IBM) was adapted for the sand production simulation geometry to simulate the fluid flow near the well casing. Oil with low viscosity and density was used as an injection fluid (reservoir fluid). This study shows what happens in the first 0.1 s immediately after perforating of the cased horizontal oil well. Erosion near the perforation tunnel was triggered due to the pressure drawdown, where the production of sand particles was initiated during the first flow due to the drag force that lifted the sand particles from the perforation damage zone. At the beginning of the simulation a sand arch was captured around the perforation tunnel and due to the fluid flow it collapsed and the perforation cavity became larger. The amount and mass of produced sand particles were calculated. The research findings provide insight into the sanding process and could be helpful for practicing engineers to understand the sanding mechanism at micro and macro scales. The results show that the proposed model is promising, and the innovative CFD-DEM-IBM-based system should be further elaborated to simulate the sand production in a sandstone formation.

S2231 Successful Endoscopic Therapy of Acute Lower GI Bleeding From Serosal Vessel Within a Contained Perforation Abscess Cavity

INTRODUCTION: We present a case of successful colonoscopic therapy of bleeding from a serosal vessel within a contained perforation cavity. CASE DESCRIPTION/METHODS: A 66 year old woman developed severe necrotizing post ERCP pancreatitis with walled off necrosis, multiple abdominal abscesses, and duodenal and colon perforation. She was transferred for evaluation of recurrent lower gastrointestinal bleeding which had been managed with transfusions due to her severe comorbidities. CT showed multiple abdominal collections with the dominant peripancreatic collection communicating with the descending colon. Colonoscopy showed large amount of blood clots and ischemic looking ulcers from 30-35cm from the anus. The scope could not be passed beyond 35cm due to stricture. A cavity was seen at 30cm which corresponded to the perforation from the peripancreatic collection seen on CT. This was filled with large amount of clots. The patient was managed conservatively and discharged back to the nursing facility. She was transferred back 6 weeks later with worsening bleeding. Repeat CT showed worsening abdominal abscesses and a drainage catheter was placed in to the loculated collection near the descending colon. CT angiogram showed bleeding from the stomach. Endoscopy was unremarkable. Sigmoidoscopy showed the known cavity at 30cm which was filled with clots and red blood. The drainage catheter was seen within the cavity. Once blood was cleared a stigmata of recent hemorrhage was seen and obliterated with hemostatic forceps. The bleeding stopped and patient was discharged back to the nursing home. DISCUSSION: Our patient presented with lower gastrointestinal bleeding from a non-gastrointestinal source since her bleeding occurred from a vessel outside of the colon. The blood drained through the colon through the perforation which is why she did not have significant bleeding nor fluid output through her drain since they drained preferentially through the large colonic fistula. Recognition of the stigmata of recent hemorrhage within the abscess cavity and hemostasis resolved the bleeding. It is safe to endoscope cavities communicating with the gut, especially when they are chronic and also have external drainage as in our patient since any CO2 insufflation or irrigation would drain outside of the body. Therefore such cavities including peripancreatic walled off necrosis, abscess, or contained perforation could be evaluated for cause of bleeding which can be safely treated using conventional hemostasis.Figure 1.: Blood clots (triangle) filling the perforated abscess is seen on the left and colon lumen (arrow) on the right.Figure 2.: Stigmata of recent hemorrhage (arrow) seen after clots cleared.Figure 3.: Percutaneous drain (triangle) is seen on the left and obliterated stigmata (arrow) on the bottom.

S2868 A Serendipitous Identification of Contained Duodenal Perforation

INTRODUCTION: Peptic ulcer disease (PUD) is a condition defined by defects in the gastric and/or duodenal mucosa that extend through the muscularis mucosa. Sequalae of untreated PUD include gastrointestinal (GI) bleeding, gastric outlet obstruction and perforation. Typical presenting symptoms of upper GI perforation include sudden onset of severe sharp abdominal pain, peritoneal signs and severe sepsis or septic shock. CASE DESCRIPTION/METHODS: We present a case of a 71-year-old woman with chronic back pain on celecoxib who presented with mild progressively worsening abdominal pain, non-bilious/non-bloody vomiting and decreased oral intake. Abdomen was benign and initial laboratory tests were unrevealing. Computed tomography (CT) revealed a 6.6 cm heterogeneous complex cystic/solid mass originating from the second portion of duodenum with large exophytic component, and abutting the pancreatic head, liver, proximal duodenum, portal vein and inferior vena cava (Figure 1). Esophagogastroduodenoscopy (EGD) revealed a fistulous tract along the duodenal sweep leading into an extra-luminal cavity (Figure 2) and multiple Forrest Class III duodenal bulb ulcers. Intraprocedural surgical consultation was obtained and a decision was made to proceed with endoscopic ultrasonography (EUS). EUS revealed a 40.2 × 27.3 mm hypoechoic heterogeneous porta-hepatis lesion with ill-defined borders, containing a well-circumscribed anechoic component consistent with contained perforation cavity. Fine needle biopsy (FNB) was performed with pathology revealing a grade 1 well-differentiated duodenal neuroendocrine tumor (D-NET) with immunohistochemical stains positive for synaptophysin, negative for chromogranin A and less than 1% positivity for Ki67 (Figure 3). Of note, serum chromogranin A level was markedly elevated to 1,105 ng/mL (normal: < 93 ng/mL). A pancreaticoduodenectomy was advised, however, patient declined. DISCUSSION: Although most common cause of duodenal perforations is PUD secondary to Helicobacter pylori infection and non-steroidal anti-inflammatory drugs (NSAIDs) use, other etiologies include diverticulum, regional infections, autoimmune conditions, ischemia, Bouveret syndrome, chemotherapy and localized tumors. NETs account for 0.5% of all cancers and D-NETs comprise 5-8% of all GI-NET. Although contained GI perforations have atypical presentations, one should always keep tumor on the differential. To our knowledge, this is the first case report of D-NET leading to perforation.Figure 1.: Intravenous and oral contrast enhanced axial (A) and coronal (B) CT images of the abdomen demonstrating a complex heterogeneous and cystic mass in the porta hepatis region. The mass is interposed between and inseparable from the duodenum (straight white arrow) and head of the pancreas (curved white arrow). The inferior aspect of the mass is heterogeneous (white arrowhead) with areas of hyper-intensity compatible with tumor enhancement. The superior aspect of the mass is cystic with complex fluid attenuation (black arrowhead) consistent with the histopathologic findings of perforation and hematoma.Figure 2Figure 3

Effect of Fabric Layer on Sound Absorption of Micro-Perforated Panel

Micro-Perforated Panel (MPP) absorber becomes an alternative to common fibrous porous absorber without owning health and environmental issues. The system is considered as the next generation of absorber in noise control. However, such a system suffers from narrow absorption bandwidth so that its application becomes limited. Theoretically, the frequency range with effective absorption is determined by the surface acoustic impedance controlled by the perforation ratio, hole diameter and cavity depth. Hence, by keeping those parameters to be constant, an intervention to the change of impedance is expected to be useful in widening the absorption bandwidth. In this research, textile materials from woven fabrics namely cotton fabric, plain fabric and satin fabric were used to cover the surface of Micro Perforated Panel (MPP) absorber either at the front or at the back surface. The sound absorption coefficients were measured for the normal incidence using an impedance tube. From the measured results, it is found that the presence of the fabric on MPP surface can improve the MPP absorber in terms of amplitude as well as the frequency bandwidth of absorption. Moreover, the placement of the woven fabric at downstream area is more beneficial than at the upstream area.

Transonic flow study in a centrifugal compressor using perforated airfoils

In this paper, the effect on a perforated plate on a centrifugal compressor is investigated using numerical simulation. The performances and fluid flow are compared for two different vaned diffusers, a base case where there are no perforated plates and a case where a perforated plate is inserted in the rotor casing at exit and the stator blade. The impact of this geometry change on the compressor performances it is studied in the case of adverse angles of attack at stator vane. Near wall refinement ensures the accuracy resolution of the boundary layer with a y+ value of one unit corroborated with a growth ratio of 1.1:1. Menter’s SST model was used in all numerical cases performed, as implemented in ANSYS CFX. Following the results of the baseline diffuser, the optimal position of the perforated cavity was determined.

Comparative efficacy of mineral trioxide aggregate and biodentine for the repair of pulpal floor perforation

In the present study, the clinical outcome of mineral trioxide aggregate and Biodentine as repairing materials in the management of pulpal floor perforation was compared in vivo. Thirty teeth having pulpal floor perforation were enrolled in this study, out of which 15 perforations were repaired with mineral trioxide aggregate and the remaining 15 were subjected to Biodentine treatment. Following perforation repair, each tooth was then subjected to root canal therapy. Patients were recalled at 3, 6 and 12 month interval. The assessment of pain, pain on palpation, tenderness on percussion, and radiological evaluation was performed to determine the repair ability of pulpal floor perforation. Statistical analysis was performed with Chi-square test between the two groups and a value of p&lt;0.05 was considered as statistically significant. The results showed that pain, tenderness on percussion as well as the thickness of periodontal ligament was gradually decreased and the communication between the perforation and oral cavity was successfully repaired following MTA and Biodentine therapy. Furthermore, the differences between MTA and Biodentine were not statistically significant. It can be concluded that clinical outcome and repair of pulpal floor perforation by Biodentine is almost similar to MTA.

Gas as a Sign of Critical Illness in Abdominal Diseases

Gas normally only occurs in the gastrointestinal system. Gas in the free abdominal compartment is a sign of perforation. But gas sometimes can also be seen in parenchymal organs (as abscess or covered perforation), also in the retroperitoneal room and very seldom in the wall of bowel or in vessels. Gas at wrong places (extragastral and extraintestinal) is an important sign in gastrointestinal diseases. Perforation of the GIT is occurring very rarely (1-2%). Most frequently it is caused by ulcers of the stomach and the duodenum. X-ray, sonography and endoscopy are most important in the diagnosis of this complication. X-ray is fairly reliable in detecting air but needs a greater emission of gas. Given optimal conditions during the examination ultrasound can detect small amounts of air (1-2 ml). In daily routine sensitivity of this method is low (approx. 50 %). The diagnosis of a covered perforation is very complicated as it is lacking the typical criteria of free air in X-ray and sonography. Patients with strong epigastric pain who were suspected to have a perforation were examined by ultrasound before and after undergoing endoscopy. We payed special attention to the presence of criteria of free air as well as any sonographical changes in the surrounding of the stomach. The detection of free air by sonography sometimes is better after endoscopy. A covered perforation can only be visualized by enhancement of air. Criteria of a covered perforation are: *Echogenuous enhancement of a strictly limited cavity of perforation. *Reverberations of air within the cavity. *Detection of the leakage. (Orifice of perforation) *Detection of air motion. *Change of sonographical image after second look sonography. The detection of a free or a covered perforation by endoscopy and other imaging methods is complicated. Second look sonography after insufflation of air by endoscopy can be useful and shows sometimes the perforation cavity. Under optimal conditions even the leakage can be visualized. The principle of a complementary sonography is little incriminatory. It provides the examiner with additional information, especially in a diagnostic procedure that is marked by a pressure of time. Gas in abdominal organs is a sign of abscess. Abscesses with gas can also occur between the bowel loops as interenteric abscesses. Gas in abdominal vessels can occur in situation of sepsis.

Verification of two-dimensional LBM-DEM coupling approach and its application in modeling episodic sand production in borehole

The lattice Boltzmann method (LBM) is implemented in the Particle Flow Code (PFC) as a pore-scale CFD module and coupled with the particulate discrete element assemblage in PFC using an immersed boundary scheme. The implementation of LBM and LBM-PFC coupling is validated with the analytical solutions in a couple of hydrodynamics and fluid-particle interaction problems, i.e., the accuracy of LBM as a CFD solver is verified by solving channel flow driven by a pressure gradient for which the closed-form solution is also derived; the accuracy of LBM-PFC coupling is validated by solving flow across a cylinder, Taylor-Couette flow, Kármán vortex street, and fluid flow through a cylinder array. To demonstrate potential applications of this coupling code, a perforation cavity subjected to axial fluid flush is then tested, showing that the collapse and reconstruction of sand arch in the perforation cavity can be reproduced in this coupling system. The developed system is ready for exploring more complicated physical issues involved in sand production.

Unsteady transonic flow control around an airfoil in a channel

Transonic internal flow around an airfoil is associated with self-excited unsteady shock wave oscillation. This unsteady phenomenon generates buffet, high speed impulsive noise, non-synchronous vibration, high cycle fatigue failure and so on. Present study investigates the effectiveness of perforated cavity to control this unsteady flow field. The cavity has been incorporated on the airfoil surface. The degree of perforation of the cavity is kept constant as 30%. However, the number of openings (perforation) at the cavity upper wall has been varied. Results showed that this passive control reduces the strength of shock wave compared to that of baseline airfoil. As a result, the intensity of shock wave/boundary layer interaction and the root mean square (RMS) of pressure oscillation around the airfoil have been reduced with the control method.

Feasibility of reservoir fracturing stimulation with liquid nitrogen jet

In this paper, a new idea of fracturing with liquid nitrogen jet was proposed because the conventional liquid nitrogen fracturing treatment has difficulty in controlling the fracture initiation location and creating multi-separated fractures along the wellbore. To analyze the feasibility of this treatment, the flow field of liquid nitrogen jet was simulated using computational fluid dynamics method, and the cracking effect of liquid nitrogen on rock was tested by laboratory experiments. The results indicated that under the same nozzle pressure drop, the liquid nitrogen jet presented better performance in abrasive particles acceleration and pressure boosting in perforation cavity than water jet. In addition, the impact effect induced by liquid nitrogen jet was equivalent to that generated by water jet. Liquid nitrogen could bring about additional cracking effect on rock because of cryogenic cooling, water freeze and nitrogen vaporization, which were also beneficial for the improvement of stimulation reservoir volume and the formation of fracture network. What's more, the liquid nitrogen jet induced the pressure boosting effect in cavity and the hydrodynamic sealing effect in annulus, which could realize the control of fracture location and the isolation of wellbore respectively without any machinery packers or bridge plugs. In conclusion, the liquid nitrogen jet fracturing presented apparent superiorities not only in avoiding the problems in hydraulic fracturing but also in overcoming the technical shortcomings of conventional liquid nitrogen fracturing. This technique will play a significant role in oil and gas development with a promising future.

Uso clínico del agregado de trióxido mineral (MTA) en el tratamiento de lesiones periapicales y perforaciones radiculares

El propósito de la presente investigación fue emplear el cemento MTA (agregado de trioxido mineral) en forma clínica para resolver complicaciones en el tratamiento de endodoncia como son las perforaciones radiculares a nivel de cámara pulpar, así como en la obturación retrograda de tratamientos de apicectomia. Se empleó el cemento MTA - Blanco, Angelus, (Industria de productos odontologicos Ltda. Londrina - PR – Brazil) que se caracterizó por tener un tiempo de endurecimiento inicial de 10 minutos y el tiempo de endurecimiento final de 15 minutos. La radiopacidad que mostró el material fue algo superior a la de la dentina y el tejido óseo, facilitando su visualización en las radiografías de control. Se hicieron controles clínicos y radiográficos a los casos tratados tanto en el postoperatorio inmediato como a los sesenta días. Los resultados muestran que hubo adaptación del cemento a las paredes de la cavidad retroapical y de los trayectos de perforación, produciéndose un sellado apical y marginal. Los elementos constituyentes del cemento: silicato tricálcico, aluminato tricálcico, silicato dicálcico, aluminato ferrico tetracálcico; permitieron una estimulación del proceso de cicatrización y reparación de los tejidos circundantes, que evolucionaron en forma favorable hasta el momento del último control realizado en esta investigación.

Portland Cement Use in Dental Root Perforations: A Long Term Followup

Root canal and furcal perforations are causes of endodontic therapy failure and different materials that stimulate tissue mineralization have been proposed for perforation treatment. In the first case, a patient presented tooth 46 with unsatisfactory endodontic treatment and a periapical radiographic lesion. A radiolucent area compatible with a perforating internal resorption cavity was found in the mesial root. The granulation tissue was removed, and root canals were prepared. The intracanal medication was composed of calcium hydroxide and the perforation cavity was filled with Portland cement. The 11-year followup showed radiographic repair of the tissue adjacent to the perforation and absence of clinical signs and symptoms or periapical lesion. In the second case, a patient presented with edema on the buccal surface of tooth 46. The examination showed a radiolucent area in the furcation region compatible with an iatrogenic perforation cavity. The mesial root canals were calcified, and only the distal root canal was prepared. The cavity was filled with a calcium hydroxide-based paste and the distal root canal was obturated. In sequence, the perforation cavity was filled with Portland cement. The 9-year followup showed the tooth in masticatory function with radiographic and clinical aspects compatible with normality.

Validation of Predicted Cumulative Sand and Sand Rate Against Physical-Model Test

Summary This paper presents a numerical model to study the onset and rate of sand production and compares its predictions against physical-model testing data on Salt Wash South (SWS) sandstone. A reliable sand-prediction tool is essential in sand-production management. It enables engineers to improve well-completion design, with the aim of maximizing well productivity without compromising well integrity. A sanding test on a weakly consolidated sandstone sample was numerically simulated using a finite-difference-based numerical model. The model is based on erosional mechanics in which coupling between fluid flow and mechanical deformation captures some of the key mechanisms that are involved in sand production. Sand is assumed to be produced when the material is fully degraded and hydrodynamic forces are high enough to remove the particles. The outcome of the numerical model shows a reasonable agreement against perforation-test results in terms of the onset and rate of sand production. The model shows that sand production initiates from the perforation tip and propagates to the top and sides of the perforation cavity. The sanding rate increases at higher flow rates. Furthermore, the model predicts external deformations of the sample, which are in close agreement with the experimental observations.

LBM–DEM modeling of fluid–solid interaction in porous media

SUMMARYThree porous media flow problems, in which the fluid mechanical interactions are critical, are studied in a mesoscopic–microscopic coupling system. In this system, fluid flow in the pore space is explicitly modeled at mesoscopic level by the lattice Boltzmann method, the geometrical representation and the mechanical behavior of the solid skeleton are modeled at microscopic level by the particulate distinct element method (DEM), and the interfacial interaction between the fluid and the solids is resolved by an immersed boundary scheme. In the first benchmark problem, the well‐known and frequently utilized Ergun equation is validated in periodic particle and periodic pore models. In the second problem, the upward seepage problem is simulated over three stages: The settlement of the column of sphere under gravity loading is measured to illustrate the accuracy of the DEM scheme; the system is solved to hydrostatic state with pore space filled with fluid, showing that the buoyancy effect is captured correctly in the mesoscopic–microscopic coupling system; then, the flow with constant rate is supplied at the bottom of the column; the swelling of the ground surface and pore pressure development from the numerical simulation are compared with the predictions of the macroscopic consolidation theory. In the third problem, the fluid‐flow‐induced collapse of a sand arch inside a perforation cavity is tested to illustrate a more practical application of the developed system. Through comparing simulation results with analytical solutions, empirical law and physical laboratory observations, it is demonstrated that the developed lattice Boltzmann–distinct element coupling system is a powerful fundamental research tool for investigating hydromechanical physics in porous media flow. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Simulation of Sand Production with a Coupled Seepage-Deformation-Damage Model

The deformation of the oil sand matrix is an important issue given that in situ and well pumping induced stresses impact on the susceptibility of the oil reservoir to produce sand. Focusing on this problem, a fully coupled seepage-deformation-damage model is developed to simulate the enhanced sand production phenomena. Finite element method with explicit and sequential iterative algorithm is used to solve the coupled governing equation system. Simulation results relating perforation cavity propagation, sand production rate and cumulative sand production are presented. The study suggests that the proposed model may be used to generate quantitative information for predicting sand production and optimizing pressure drawdown.

Formation Sand Liquefaction: A Mechanism for Explaining Fines Migration and Well Sanding

To understand the basic relationship between the rising water-cut, well sanding, and migration of fines, the author’s work led him to examine the mechanism of well sanding due to sand liquefaction in cases where the storm chokes in offshore wells were activated and when the production platform separator lines froze due to sudden cold weather. The author found that as the original water-oil contact plane rose above the original plane of contact, it caused a drastic change in water saturation and relative permeability. We show the increased water saturation decreases the resistance of the formation to stress by as much as 50%. This is one of the causes of sand liquefaction at or near the perforation cavities. The parameters affecting the process most are the fine-particle buoyancy, changes in the effective stress and the bulk density of the sand, the pore pressure buildup and changes in porosity near the perforation cavities, the induced transient shear stress resulting from the water-hammer total pressure wave, and the lack of adequate cohesive cement or interlocking contacts between the grains of the unconsolidated sand. The simple model calculations pointed to the conclusion that if the grains of the unconsolidated sand or the fine particles accelerated above the threshold limit of 0.19000g, the chances for fines migration and sand liquefaction were high. Furthermore, if, at the free face of the washed-out perf tunnels or the cavernous cavities of the unconsolidated sand, the total pressure wave magnitude exceeded the shear resistance of the sand, then sand liquefaction was certain to occur. The obvious outcome of this process is nothing but serious formation damage. Based on his models, the author’s recommendation for alleviating this type of damage, includes but is not limited to selective perforation, oriented perforation, gravel packing, frac packing, filter packing, trajectory planning for well reentries, and controlled drawdown.

A case report of an esophageal perforation due to idiopathic esophageal ulceration associated with human immunodeficiency virus infection

We report a case of a 32-year-old man with HIV infection who has an esophageal perforation of an idiopathic ulcer. He had been treated by conservative therapy, and an endoscopic therapy was performed for the closure of the perforation. The HIV infection was well controlled by anti-HIV drugs administration and the ulcer became scared. In January 2002, he felt difficulty to swallow and had a high fever. He was admitted and computed tomography (CT) of the chest showed right pyothorax. Drainage of the pyothorax cavity and antibacterial therapy was performed. His blood examination indicated HIV infection. Esophagogram showed an esophageal perforation. Endoscopic examination showed giant ulcer that was considered as idiopathic one because cytomegalovirus antigen was not detected in his blood and it was cured without anti-herpes-virus drugs. He was conducted enteral nutrition and medication of anti-HIV drugs through gastoric tube. HIV infection was well controlled and the ulcer got healed progressively, but the perforation remained. So we performed an endoscopic therapy which was a brushing technique with irregular epithelium on inner face of perforation cavity by a pancreatic duct biopsy brush. Successfully the perforation was closed and he could regain to take orally soon. He discharged 152 days after admission and his HIV-infection is controlled as an outpatient.

Investigating fault slip in a model of an underground gas storage facility

Physical model experiments have been performed on perforation cavities in a weak sandstone. The objective of the study has been to investigate the effect of the flow geometry on sand production risk. Two extreme geometries have been tested, one with flow mainly axially towards the tip of the cavity and one with fluid flowing radially towards the side of the cavity. The experiments have been performed in a special pressure vessel for sand production studies. We have recorded the deformation of the cavity, the flow rate through the sample and monitored sand production and acoustic emission activity as functions of the imposed confining pressure and pore pressure drop across the sample. From the tests, we have found initial cavity failure and initial sand production at various combination of confining and pore pressure. The results have also been corroborated by finite element simulations. We have concluded that by directing the flow through the bottom of the cavity sand production is inhibited compared to the case where flow mainly enters through the side of the cavity. This is because the cavity fails along the wall first, while the bottom is intact. As flow promotes the removal of failed material, radial flow increases the risk of sand production.