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Aims: This study was aimed to report the characteristics and treatment of ventricular tachycardia (VT) following surgical treatment of pulmonary stenosis with intact ventricular septum.Methods and Results: Five patients underwent radiofrequency catheter ablation for sustained monomorphic left bundle branch block (LBBB) type VT who previously underwent surgical treatment of pulmonary stenosis. Except stimulation, voltage and activation mapping was performed using three-dimensional (3D) electro-anatomic mapping and ablation was applied accordingly. Four VTs were induced during EP study. Two VTs were focal and the earliest activity was targeted in the right ventricular apex (RVA). The other two VTs were reentrant and the critical isthmus located in the mid-lateral wall and anterior wall of right ventricle, respectively. Ablation abolished all inducible VTs in four patients. In the patient whose VT was non-inducible, radiofrequency (RF) energy was delivered to the RVA where pacing mapping matched the clinical VT. One focal VT recurred 60 months after the initial RF ablation. Repeat mapping and ablation was performed and no VT recurred over a 24-month period.Conclusions: The mechanism of VT following surgical treatment of pulmonary stenosis can be either focal or reentrant. Ablation of this subgroup of VT is feasible. [ABSTRACT FROM AUTHOR]

ABSTRACT Aiming at good thickening ability and temperature resistance in water-based drilling fluid, a novel copolymer viscosifier (SDKP) of sodium 2-acrylamido-2-methylpropane sulfonate (NaAMPS) with N-vinylcaprolactam (NVCL) and cross-linking divinylbenzene (DVB) was prepared by micellar radical polymerization. The composition and molecular structure of optimal SDKP under the optimum reaction conditions was characterized by FT-IR, 1H-NMR, and elemental analysis, and the molecular weight was determined by GPC. Thermal gravimetric analysis showed that the SDKP was even stable when the temperature was not higher than 330 °C. The performance of SDKP as viscosifier for aqueous, brines, and saturated brine bentonite drilling fluid was evaluated before and after aging tests at 230 °C for 16 h. The evaluation results indicated that the SDKP had excellent thickening ability, thermal resistant, and salt tolerance. HTHP rheology test showed that the SDKP containing drilling fluids displayed a thermo-thickening effect in temperature range of 150 to 180 °C, which was beneficial to increase the viscosity and strength of fluids at high temperatures. Shear test showed that the SDKP illustrated a similar shear thinning to xanthan gum. ESEM observations demonstrated that the continuous three-dimensional network was formed in the SDKP aqueous and brines solution, which was probably the main reason for its excellent thickening properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44140. [ABSTRACT FROM AUTHOR]

In the L Area, big data techniques are employed to manage the principal controlling factors of coalbed methane (CBM) production, thereby regulating single-well output. Nonetheless, conventional data cleansing and the use of arbitrary thresholds may result in an overemphasis on certain controlling factors, compromising the design and feasibility of optimization schemes. This study introduces a novel approach that leverages raw data without data cleaning and eschews artificial threshold setting for controlling factor identification. The methodology supplements previously overlooked controlling factors, proposing a more pragmatic CBM production adjustment scheme. In addition to the initial five controlling factors, this approach incorporates three additional ones, namely, dynamic fluid level state, drainage velocity, and fracturing displacement. This study presents a practical application case study of the proposed approach, demonstrating its ability to reduce reservoir damage during the coal fracturing process and enhance output through seal adjustments. Utilizing the full spectrum of original data and minimizing human intervention thresholds enriches the information available for model training, thereby facilitating the development of a more efficacious model. [ABSTRACT FROM AUTHOR]

Most scholars believe the existence of starting pressure, thinking of the threshold pressure resulted from the abnormal of fluid boundary zone properties, non-Newtonian fluid and the lagging of oil-gas phase permeability. But the abnormal of fluid boundary layer properties have been proven to be negative by chemical experts; Small part of scholars believe that there is no threshold pressure, and the illusion of starting pressure existing is because of the respond process of rock strain, the limit of experimental instrument accuracy, man-made measurement error, and additional pressure difference caused by reservoir damage, besides, the presence of threshold pressure gradient cannot explain hydrocarbon migration and production pressure differential phenomena, so the exemplified explanation means no start-up pressure. The investigation shows found that, threshold pressure related problems have always been studied, and there is still much work to do. The core of the work is to make clear the connotation of starting pressure. [ABSTRACT FROM AUTHOR]

The current researches on shale gas formation damage derive from the conventional theory of sandstone reservoir and carbonate rock reservoir. To review the researches of shale gas formation damage, factors affecting penetration ability were focused on. It was thought that the internal factors have mainly been recognized as listed below: the low-permeability leads to water block; the high content of clay tends to swell and block channels; shale surface capillary force increases resistance to gas flow; the conditions of high temperature and high pressure do harm to the performance of working fluids and easy to increase the reservoir fluids residual; the CO2 flow contaminates the working fluids and increases the residual. While the external factors of formation damage include the following items: the swell of clays caused by the insufficient inhibition ability of working fluids; the invasion and residual of working fluids as well as the additives; the biofilms generated by working fluids obstruct gas flow in reservoir; and the liquid volatilization speed around the borehole is too low to prevent water blocking and causes channel blocking, which results from low production pressure. The mechanisms of the formation damage during desorption and diffusion process in shale gas has not been systematically researched as well as the effects of different processes such as drilling and completing, reservoir stimulation and drainage on desorption and diffusion capacity. The basic theory on the formation damage of the shale gas has not been established. Moreover, there is no agreed evaluation criterion on shale gas formation damage indoor and in the field on shale gas. [ABSTRACT FROM AUTHOR]

The theories for lost circulation control are divided into five major categories, including Rigid Plugging Theory, Flexible Plugging Theory, Lost Prevention by Lowering Pressure Theory, Lost Prevention by Bearing Pressure Theory, and Fuzzy Plugging Theory, based on plugging mechanisms. Before the emergence of plugging theories, the main causes of lost circulation were considered as the lost circulation medium, including fractures and caves in the formation. The medium was attempted to be blocked by plugging materials, without considering the size matching relationship between plugging materials and formation lost circulation medium. By Rigid Plugging Theory, including Packing Plugging Theory and Bridging Plugging Theory, the lost circulation is controlled by accumulating particles or bridging in the medium. By Flexible Plugging Theory, the lost circulation is controlled by the special properties of the polymer which invades the formation porous medium with working fluids and generates a special area to kill the lost circulation by physical and chemical reaction of some special ingredients. The Lowering Pressure Theory prevents lost circulation by lowering fluid column pressure to lower the pressure difference between bottomhole pressure and reservoir pressure. The Bearing Pressure Preventing Lost Theory plugs the micro-fractures to improve the bearing pressure capacity of wellbore, according to the principle of fracture stability. The Fuzzy Plugging Theory controls lost circulation by the particles, which are described by the fuzzy mathematics for the parameters of the pores and fractures such as size, shape, and number. Nowadays, the main plugging theory is Rigid Plugging Theory. The Lowering Pressure Prevention Lost Theory will not be used extensively since it is largely limited by formation and facilities, though it develops rapidly. The Fuzzy Plugging Theory may have a bright future for its compatibility between the natural formation and the property of the lost circulation materials. [ABSTRACT FROM AUTHOR]