Evaluation of hetro-stacked target plate response toward different nose shaped projectile impact

Detailed experimental and numerical investigations were carried out for evaluating the dynamic response of the stacked target plates toward moderate (100–250 m/s) velocity projectile impact. A single stage gas gun was utilized to launch the hemispherical and the blunt projectile toward two different hetro-stacked configurations (Al-St and St-Al). A comprehensive experimental (high speed 3D-DIC) and numerical (FE) evaluation was conducted to obtain the transient and post-impact behavior of the target plates. Influence of different projectile shapes on the full-field transient deformation profiles of different stacking configurations was studied in detail. Also, typical perforation parameters like plug size, shape, and perforation hole diameters were carefully measured and analyzed. A comprehensive error measure was utilized to quantify the similarity between the experimental and simulation results, a very good agreement was observed.

TREATMENT OF PATIENTS WITH GASTRIC CANCER COMPLICATED BY PERFORATION

Introduction. Despite the declining incidence of gastric cancer, the problem of treatment of complicated forms of the disease remains one of the most complex and relevant. The aim of the study was to improve the results of treatment of patients with complicated gastric cancer. Materials and methods. The study is based on the analysis of the results of treatment of 19 patients with gastric cancer complicated by perforation, who were treated at the “State Institution «Zaitsev V.T. Institute of General and Urgent Surgery of National Academy of Medical Sciences of Ukraine” from 2011 to 2020 aged 18 to 85. All patients were divided into two groups: comparison — 9 (47.3 %) patients (were treated from 2011 to 2015), the main — 10 (52.7 %) patients (treatment period from 2016 to 2020). Results and discussion. In the comparison group, conventional surgical tactics and operations were used. The main group used active-individualized two-stage surgical tactics, which involve suturing a perforation hole in the first stage and combined and reconstructive surgery in the second. Radical operations were performed in 10 (52.6 %) patients; in 9 (47.4 %) — palliative and symptomatic. Postoperative complications occurred in 5 patients (26.3 %), postoperative mortality was 26.3 % (5 patients). Conclusions. In patients with gastric cancer complicated by perforation, in a serious condition of the patient and the presence of diffuse peritonitis, we consider it appropriate to use two-stage surgical tactics. The introduction of the proposed surgical tactics and new surgical interventions helped to increase the number of radical operations from 4 (21.0 %) in the comparison group to 6 (31.6 %) in the main group and reduce postoperative mortality from 15.8 % to 10.5 %, respectively.

Ball sealer tracking and seating of temporary plugging fracturing technology in the perforated casing of a horizontal well

Multistaged temporary plugging fracturing in horizontal wells is an emerging technology to promote uniform fracture propagation in tight reservoirs by injecting ball sealers to plug higher-flux perforations. The seating mechanism and transportation of ball sealers remain poorly understood. In this paper, the sensitivities of the ball sealer density, casing injection rate and perforation angle to the seating behaviors are studied. In a vertical wellbore section, a ball sealer accelerates very fast at the beginning of the dropping and reaches a stable state within a few seconds. The terminal velocity of a non-buoyant ball is greater than the fluid velocity, while the terminal velocity of a buoyant ball is less than the fluid velocity. In the horizontal wellbore section, the terminal velocity of a non-buoyant or buoyant ball is less than the fracturing fluid flowing velocity. The ball sealer density is a more critical parameter than the casing injection rate when a ball sealer diverts to a perforation hole. The casing injection rate is a more critical parameter than the ball sealer density when a ball sealer seats on a perforation hole. A buoyant ball sealer associated with a high injection rate of fracturing fluid is highly recommended to improve the seating efficiency.

Study Investigates Factors Affecting Coefficient of Discharge in Stimulation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 200612, “The Role of Backpressure and Perforation-Hole Erosion on the Magnitude of the Coefficient of Discharge in Hydraulic Fracturing Stimulation,” by Davood M. Yosefnejad, Bernd Fricke, and Joern Loehken, DynaEnergetics Europe, et al., prepared for the 2020 SPE Virtual Europec Conference, 1–3 December. The paper has not been peer reviewed. One of the important factors affecting the near-wellbore-fluid pressure drop is the coefficient of discharge (Cd). In the complete paper, the authors investigate some of the factors that can affect Cd, such as the erosion of the perforated hole and the backpressure given by the fracture. The paper studies the effect of perforation hole size, geometry, and shape on the Cd value at ambient conditions and with backpressure, before and after sand erosion. Setup Specifications and Materials For this study, a high-pressure, high-flow setup was built for Cd measurements, as well as a second setup in which the holes can be eroded by proppant-laden slurries. The test cell was the same for both setups. The holders of the plates were stainless steel and connected to 7-in. pipes approximately 4 ft long on each side. In all the experiments, the flow rate and inlet and outlet pressure data were recorded simultaneously vs. injection time by high-precision sensors. All experiments were carried out at an ambient temperature of 15–28°C. For these flow-test experiments, only water was used, circulated with different pressure differentials to determine the effect of pressure on Cd magnitude. In addition, backpressure was applied through the needle valve to simulate real reservoir conditions and to compare the Cd value with the tests under ambient conditions. The flow rate range of the pump was 1–7 bbl/min at maximum pressures of approximately 2,000 psi. Erosion tests have been performed for 30 minutes with a near-constant flow rate (approximately 1 bbl/min), constant pressure (approximately 200 psi), and constant sand concentration. For the erosion test, a viscosity of approximately 10 cp was used. The sand concentration was kept at 1 to 2 lbm/gal to keep the erosion rate low, which would allow distinguishing between shape-driven changes in Cd and changes caused by an increase of the hole size. The study used machined holes and holes created by differently shaped charges, which also differed in size and geometry. A description of these holes, and associated shaped-charge tests, is provided in the complete paper. Experimental Results and Discussion Generic Holes. In the first sets of experiments, generic holes with different entrance-hole diameters were used. The experiment began with the lowest inlet pressure, which gradually was increased to the maximum pressure. The outlet pressure was kept constant at an ambient pressure. The flow rate increased because of the increase in differential pressure. After reaching the maximum pressure, the inlet pressure was kept constant and the choke on the outlet side was closed step by step to establish a backpressure, which led to a decrease in differential pressure. Surprisingly, the flow rate stayed constant until the differential pressure surpassed 700 psi.

A Shot in the Dark: How Your Post-Fracture Perforation Imaging can be Misleading and How to Better Understand Cluster Efficiency and Optimize Limited Entry Perforating

With recent advances in downhole imaging technology, it has become evident that surface perforation testing does not directly translate to downhole conditions. A total of 279 pre- and 595 post- fracture treatment perforations were imaged in this analysis. Pre-treatment perforation hole size was highly variable, even with oriented equal-entry charges. Because of high pre-fracture treatment variability, it is not recommended to use an average diameter of unstimulated perforations to evaluate cluster efficiency of perforations post-fracture treatment. Ideally, perforations should be individually imaged before and after treatment for direct comparison. However, since pre-treatment imaging is costly, an alternate methodology is presented. The findings in this paper will challenge current understanding of actual pre-treatment hole sizes, their variability, and their implications on cluster efficiency. Cluster efficiency cutoff limits have historically been subjective and promoted a false confidence in the ability of Completions Engineers to extend stage lengths and adjust perforation designs. A more stringent and calculated method of determining cluster efficiency is presented. Utilizing both wireline pumpdown for pre-treatment measurements, and coil tubing for post-treatment measurements, downhole imaging technology was deployed to measure perforations from four separate perforation charge manufacturers for pre- and post- treatment erosional analysis. Additionally, while understanding the strike/slip stress state of the Anadarko basin, perforations were oriented at 90° and 270° (degrees from top of wellbore), parallel to the maximum rock stress, promoting a shorter and less tortuous path to the fracture initiation point. Perforating at 90° and 270° reduced tortuosity and surface treating pressure, promoted a less variable pre-treatment perforation hole size due to its symmetry, and resulted in a significant increase in cluster efficiency verses pervious designs. This project effectively optimized a perforation design utilizing pre- and post- fracture treatment perforation imaging and a thorough understanding of pre-treatment perforation hole size to evaluate the effectiveness of stress-targeted, oriented perforating and its effect on cluster efficiency, tortuosity, and pre-treatment hole size variability. The optimized design resulted in 84%-97% cluster efficiency and reduced surface treating pressure by 770 psi. This workflow can be applied by Completions Engineers to any unconventional basin where plug and perf design is utilized.

Quantitative evaluation indexes of the spatial steering effect of directional perforation hydraulic fractures

To better evaluate the spatial steering effect of directional perforation hydraulic fractures, evaluation indexes for the spatial steering effect are first proposed in this paper. Then, these indexes are used to quantitatively evaluate existing physical experimental results. Finally, with the help of RFPA2D-Flow software, the influence of perforation length and azimuth on the spatial steering process of hydraulic fracture are quantitatively analysed using four evaluation indexes. It is shown by the results that the spatial deflection trajectory, deflection distance, deflection angle and initiation pressure of hydraulic fractures can be used as quantitative evaluation indexes for the spatial steering effect of hydraulic fractures. The deflection paths of directional perforation hydraulic fractures are basically the same. They all gradually deflect to the maximum horizontal principal stress direction from the perforation hole and finally represent a double-wing bending fracture. The deflection distance, deflection angle and initiation pressure of hydraulic fractures increase gradually with increasing perforation azimuth, and the sensitivity of the deflection angle to the perforation azimuth of hydraulic fractures also increases. With increasing perforation length, the deflection distance of hydraulic fractures increases gradually. However, the deflection angle and initiation pressure decrease gradually, as does the sensitivity.

Tertiary dentin deposition in the proximity of the cervical perforation aperture – A case study

Dead tracts are dentin areas characterized by degenerated odontoblastic processes; may result from injury caused by caries, attrition, erosion, or cavity preparation. Odontoblasts can also form tertiary dentin, as a response to injury, in association with caries, trauma, or restorative procedures. Generally, this dentin is less organized than primary and secondary dentin and mostly localized to the site of injury. The reactive dentin formation that lays under caries, the pulp displays chronic inflammation and tertiary dentinogenesis takes place on the inner walls of the pulp space, in the region of the dentinal tubules associated with the base of the carious lesion. Higher-power photomicrograph of tertiary dentin shown in a primary dentin, first period of tertiary dentin formation, second period of tertiary dentin formation. We initiated a case study regarding depositition of tertiary dentin in the close proximity of the cervical perforation hole on mesial root of the second maxillary molar. The repair material used (Biodentine, Septodont) was found placed under the tertiary dentin layer, rather than at the perforation place, mentioning the fact that the group of residents was not experienced with the management of the endodontic microscope and did not use a proper field. We consider that we have identified dead tracts due to the fact that they were formed consequently carious lesions pathology, thereafter the tertiary dentin at the appearance of the coronal aspect was identified at the end of the dead tracts. The portion of the canal entrances were investigated both with analyzed filters (Crossed Polars) and with compensatory devices (retardation plates). The present study identified tertiary dentine deposits in the coronary portion of the adjacent root canal entered in the perforation. At a thorough analysis of the coronal portions of the mesial root canal with compensating devices and analyzers filters, it was noticed a soft dentin blanket in which the dentinary tubules do not exist or are of very rare deposition.

Physical modeling of deformation and filtration processes in low-permeability reservoir rocks when implementing the directional unloading method

This article describes the results of physical modeling of deformation and filtration processes in low-permeability reservoir rocks of the Achimov deposits of the Urengoy gas condensate field. The experiments were carried out on a unique true Triaxial Independent Loading Test System (TILTS) of the Institute for Problems in Mechanics of the Russian Academy of Sciences. The effect of the non-uniform triaxial stress state on the character of deformation and filtration processes in rocks was studied. Real stresses that occur in the bottomhole formation zone when the pressure in the well decreases were created in the rock specimens. Experiments were carried out to simulate the stress state at the walls of the open hole and at the tip of the perforation hole. The geomechanical approach is shown to be promising for creating ways to improve the quality of wells; in particular, the adaptation of the directional unloading method for the conditions of a given reservoir is considered. These studies are essential both in fundamental scientific and practical terms to substantiate technological solutions in the development of fields with low-permeability reservoirs.

Laparoscopic surgery by spontaneous rupture of the esophagus, a case report of treatment Boerhaave syndrome

Spontaneous rupture of the esophagus, Boerhaave syndrome, is a rare pathology and emergency condition for the patient. Patient, 63-year-old, on the 6th day of the disease falls into the clinic, where a Boerhaave syndrome was diagnosed. Laparoscopic surgery was performed. Sanitation and drainage of the mediastinum, suturing of the perforation hole were performed. After the operation, а positive response to treatment was observed. A group of authors believes that a minimally invasive approach to the treatment of spontaneous esophageal rupture is the alternative method for patients with severe somatic status and a small perforated opening of the esophagus.

A Perforated Baffle Design to Improve Mixing in Contact Tanks

In this study, a perforated baffle design is proposed to improve mixing in contact tanks. Turbulent flow through the perforated baffle is studied at the perforation hole scale. The contribution of jets emerging from the perforations to the mixing process is evaluated in terms of standard mixing indexes for various perforation parameters, such as the solidity ratio and hole diameter. Based on numerical simulation results, the two sets of perforated baffles that yielded the highest performance were manufactured from polycarbonate and tracer studies were conducted on a laboratory model. Comparison of numerical and experimental results demonstrates that the numerical model developed is reliable in simulating the flow through the perforated baffles and the associated mixing level in the contact tank. Numerical simulations indicate that the jet flow structure through the perforated baffle penetrates to the recirculation zones in the neighboring chambers and turns the dead zones into active mixing zones. Furthermore, large scale turbulent eddies shed by the perforations contribute to the mixing process in the chambers of the tank. With the use of the perforated baffle design, it is shown that the hydraulic efficiency of the tank can be improved from average to superior according to the baffling factor, and the associated mixing in the proposed design can be improved by 31% according to the Morrill index.