High-pressure Compartment Research Articles

Optimizing well construction by establishing overpressure mechanism in Panna Formation, Western Offshore Basin, India

The Panna Formation was deposited during the Paleocene period and is the oldest hydrocarbon-bearing tertiary sedimentary unit in the Western Offshore Basin (WOB). It is also believed to be the source rock above which hydrocarbons pools in. In the recent years, exploration activity in the Panna Formation has significantly increased, owing to its own potential hydrocarbon pools. The primary challenge encountered when drilling through the Panna Formation include well flows, mud losses, stuck pipe events, and limitation of using logging while drilling (LWD) tools due to high temperature which makes it tough for real-time monitoring without LWD. The stable-mud-weight window becomes narrow (<2 ppg), and the pore pressure seems to vary considerably from near-hydrostatic to ∼17.5ppg mud weight equivalent (EMW). This overpressure zone is correlated with relative thickness of Panna Formation and well locations in the region. The pore pressure ramp is observed to start either from the bottom of the Lower Bassein or Devgarh Formations (formation overlying Panna) or 120m–150 m inside the Panna Formation itself. Additionally, the transition of pore pressure from near-hydrostatic to overpressure zone is quite sudden. As a result, when the lithological seal isolating the high-pressure compartment is broken during drilling, well flow is encountered. In the process of well control, mud weight is increased to corresponding shut-in-drill-pipe pressure (SIDPP), which sometimes causes mud losses in the overlying formations because of insufficient fracture gradient. To delineate the area with overpressure and identify its mechanism, a comprehensive geomechanics study with lithology types has been carried out across 5 main blocks of WOB. The study integrates petrophysical, geological, and drilling information to give insight into the overpressure mechanism and safe drilling solutions through this complex setup. The pore pressure, rock mechanical properties, and stress profiles have been estimated in multiple wells to build robust geomechanical models and estimate the most stable mud weight windows. This study establishes the Type-II overpressure phenomenon with the help of crossplots between effective stress with velocity, density with compressional slowness, and pressure with porosity. There is a clear shift in the geothermal gradient associated with the overpressure interval. The casing policies for safe drilling have been discussed in different scenarios. The analysis has also outlined the occurrence of overpressure in triangular area adjacent to the Bombay High Oilfield.

High-pressure ESI-MS made easy using a plug-and-play ion source and its application to highly conductive aqueous solutions.

The performance of a compact high-pressure electrospray ionization (HP-ESI) source that can be readily used for commercial atmospheric pressure ionization (API) mass spectrometers is reported. The ion source employs a converging-diverging outlet nozzle, and ions/droplets generated inside the high-pressure compartment are carried by the high-velocity air jet toward the mass spectrometry (MS) ion inlet placed under the atmospheric pressure. With the use of a shielding electrode, the HP-ESI can also be operated with its emitter held at ground potential. This feature prevents the flow of current from the emitter to other electrically grounded components and facilitates the connection of ion source to liquid chromatography (LC) columns or capillary electrophoresis. Sensitive detection of proteins from highly conductive aqueous solutions such as 0.1% trifluoroacetic acid (TFA) solution and the prevention of electrochemical artifacts by the grounded emitter operation are demonstrated.

Shale gas in China: Characteristics, challenges and prospects (I)

Abstract This paper mainly discusses the industrialization progress, “sweet spot” evaluation criterion, E&P technologies, success experiences, challenges and prospects of China's shale gas. Based on the geologic and engineering parameters of the Fuling, Changning and Weiyuan shale gas fields in the Sichuan Basin, this paper points out that China's shale gas has its particularity. The discoveries of super-giant marine shale gas fields with high evolution degree (R o =2.0%−3.5%) and ultrahigh pressure (pressure coefficient=1.3−2.1) in southern China is of important scientific significance and practical value to ancient marine shale gas exploration and development to China and even the world. It's proposed that shale gas “sweet spots” must be characterized by high gas content, excellent frackability and good economy etc. The key indicators to determine the shale gas enrichment interval and trajectory of horizontal wells include “four highs”, that is high TOC (>3.0%), high porosity (>3.0%), high gas content (>3.0 m 3 /t) and high formation pressure (pressure coefficient>1.3), and “two well-developed” (well-developed beddings and well-developed micro-fractures). It's suggested that horizontal well laneway be designed in the middle of high pressure compartment between the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation. The mode of forming “artificial shale gas reservoir” by “fracturing micro-reservoir group” is proposed and the mechanisms of “closing-in after fracturing, limiting production through pressure control” are revealed. Several key technologies (such as three-dimensional seismic survey and micro-seismic monitoring of fracturing, horizontal wells, “factory-like” or industrialized production mode, etc.) were formed. Some successful experiences (such as “sweet spot” selection, horizontal well laneway control, horizontal length optimization and “factory-like” production mode, etc.) were obtained. The four main challenges to realize large-scale production of shale gas in China include uncertainty of shale gas resources, breakthroughs in key technologies and equipment of shale gas exploration and development below 3 500 m, lower cost of production, as well as water resources and environment protection. It is predicted that the recoverable resources of the Lower Paleozoic marine shale gas in southern China are approximately 8.8×10 12 m 3 , among which the recoverable resources in the Sichuan Basin are 4.5×10 12 m 3 in the favorable area of 4.0×10 4 km 2 . The productivity of (200−300)×10 8 m 3 /a is predicted to be realized by 2020 when the integrated revolution of “theory, technology, production and cost” is realized in Chinese shale gas exploration and development. It is expected in the future to be built “Southwest Daqing Oilfield (Gas Daqing)” in Sichuan Basin with conventional and unconventional natural gas production.

High purification of gases by the hybrid gas hydrate-membrane method

A combination of membrane separation with gas hydrate crystallization has been proposed for enhancing the efficiency of separation and purification of gass. A mathematical model of a hybrid gas hydrate-membrane method has been derived. The results of calculation of the degree of separation by this method for different process conditions are presented. It has been shown that the use of gas hydrate crystallization in membrane technology can preclude the concentration of impurities in the high-pressure compartment of a membrane element and thereby significantly improve the gas separation and purification efficiency.

Model for Calculating and Optimizing Gas Flow Rates in the Hydrogen-Permeable Capillaries of Permeators

Differential equations and boundary conditions are derived to interrelate the flow rates and pressures inside and outside the hydrogen-permeable capillaries of high-temperature permeators. Algorithms for solving these equations are presented. The effect of the flow direction in the high-pressure compartment and the capillary geometry on the performance characteristics of the permeators is reported.

Partial Splenectomy, Transposition of the Spleen to the Abdominal Wall or Splenohepatoplasty in Portal Hypertensive Rats. Effects on Portal Venous Pressure and Homeostasis - Microscopical Appearance of the Transposed Spleen

Reduction of the splenic volume by partial resection and collateral development after transposition are of potential value in the elective treatment of esophageal varices, hypersplenism and ascites. A study was performed on young Wistar rats. A simple animal model of extrahepatic portal hypertension was used, narrowing the portal vein to an outer diameter of one millimeter (PVS). One day, three weeks and seven weeks after this operation the portal venous pressure was elevated as compared with the sham-operated controls. The portal hypertension was statistically significant at week three (1.31 +/- 0.04 vs. 0.72 +/- 0.18 kPa, p = 0.01). Portocaval pressure gradient after partial resection of the spleen (SR) and intramuscular transposition (IMTrans) was compared with the pressure gradient after graded portal vein stenosis. Three weeks after intramuscular transposition portocaval pressure gradient was reduced (1.46 +/- 0.38 vs. 1.74 +/- 0.13 kPa, n.s.). This data supports the hypothesis that the portal venous high-pressure compartment and the systemic venous low-pressure compartment are maintained after development of natural shunts to the systemic circulation. In the following experiment different types of splenic transposition were tested and compared to each other and a normal control group or to rats with protal vein stenosis (PVS), respectively. After PVS, the animals were reoperated, an SR was performed and the wound surface of the spleen was transposed into the left abdominal wall subcutaneously (SCTrans) or intramuscularly (IMTrans) or to the left liver lobe (splenohepatoplasty, SHP), respectively. After three weeks the animals underwent measurements of organ weights, collections of blood samples and the spleen was investigated histologically. Blood cell counts were nearly normal but total serum protein, albumin and the colloid osmotic pressure were slightly diminished or significantly reduced (COP in the groups PVS + SR + IMTrans or SCTrans, p < 0.05) compared to the controls. Differences to the group with portal vein stenosis (PVS) were not significant. Serum protein electrophoresis after splenic transposition revealed an unobtrusive distribution pattern. Animals after SHP had the best increase in weight and high protein levels, but splenohepatic collateral development seemed sparse. Differences of plasma ammonium levels were statistically not significant, but some animals had elevated levels after transposition. Morphometry of routine-stained spleen specimens showed an intact immunoarchitecture of the transposed spleens.

The vascular pole of the renal glomerulus of rat.

In the present study we provide a detailed structural analysis of the vascular pole of superficial and midcortical glomeruli of the rat kidney. A description of the juxtaglomerular portions of the afferent and efferent arterioles, the extraglomerular mesangium and the glomerular stalk is included. The specific structural elaboration of the epithelial transition from the podocytes to the parietal epithelium is emphasized, with particular attention to the arrangement of the cytoskeleton and its connections to extracellular matrix elements. The branching patterns of the afferent and efferent arterioles are quite different. Immediately at the glomerular entrance, the afferent arteriole divides into its primary branches. In contrast, the efferent arteriole has a specific outflow segment (consisting of an intraglomerular portion and a portion associated with the extraglomerular mesangium) established by the confluence of capillary tributaries deep inside the glomerular tuft. Just at the transition from inside to outside, this segment includes a prominent narrow portion with conspicuous endothelial cells bulging into the vessel lumen. The extraglomerular mesangium has been found to represent a solid block of cells and matrix filling the space between the macula densa and both arterioles and extending into the entrance funnel. Peripherally located extraglomerular mesangial cells attach to the outer aspect of the parietal basement membrane. As a whole, the extraglomerular mesangium occludes the glomerular tuft. The results appear relevant with respect to four major aspects: (1) a support function counteracting the expansile forces resulting from the high intraglomerular pressures, (2) a direct functional influence of the afferent on the efferent arteriole, resulting from their narrow assemblage at the glomerular entrance, (3) a specific shear stress receptor function of the intraglomerular segment of the efferent arteriole, and (4) fluid leakage from the glomerular tuft through the stalk and the extraglomerular mesangium into the cortical interstitium. 1. The glomerulus is a high-pressure compartment; expansile forces continuously tend to expand glomerular capillaries, the glomerular stalk, and the glomerular entrance. Counteracting centripetal forces at the vascular pole appear to be developed as circular forces by the cytoskeleton of podocytes and parietal cells surrounding the glomerular entrance and as interconnecting forces between both arterioles and between opposing walls of the glomerular entrance, as well as of the glomerular stalk. These interconnecting forces are developed by the extraglomerular mesangium which--as a whole--forms a spiderlike closure device holding the glomerular entrance together. In addition, the extraglomerular mesangium develops occluding forces, allowing a gradual pressure drop between the glomerular stalk and the macula densa. 2. At the glomerular entrance, the outflow segment of the efferent arteriole is narrowly associated with the bifurcation of the afferent arteriole. Both are enclosed together in a common compartment surrounded by the glomerular basement membrane; there is no pressure barrier individually encompassing each vessel. Therefore, it may readily be suggested that the hydrostatic pressure of the afferent arteriole acts on the efferent arteriole. As a consequence, the luminal width of the efferent arteriole at this site, i.e., its resistance, may be directly modified by the pressure in the afferent arteriole. 3. The efferent arteriole at the transition of the intraglomerular segment to the segment that passes through the extraglomerular mesangium has a conspicuously narrow portion with endothelial cells protruding into the vessel lumen. In addition, this segment is prominent by the expression of the neuronal type of nitric oxide synthase. We therefore propose that this segment acts as a specific shear stress receptor. The possible relevance of a shear stress receptor at this site would be

Transient Compartment Syndrome of the Forearm After Attempted Radial Artery Cannulation

Transient Compartment Syndrome of the Forearm After Attempted Radial Artery Cannulation

Distribution of sub-surface pressure in the Norwegian Central Graben and applications for exploration

The Norwegian Central Graben contains a distinctive three-tiered sub-surface pressure system. This pressure system has an important effect on distribution of oil and gas fields, generation and migration of hydrocarbons, reservoir qualities and drilling procedures. A number of mechanisms have been proposed for the development of overpressure. In this paper, five are briefly discussed: thermal expansion of water, sedimentary compaction, rate of sediment burial, volumetric increases due to generation of hydrocarbons, and column heights of major oil and gas fields. None of the factors are mutually exclusive and all contribute to the development of overpressure in the Norwegian Central Graben. Utilizing drill-stem tests (DSTs), repeat formation tests (RFTs) and sonic and density logs, the horizontal and vertical boundaries of the three-tiered pressure system of the Norwegian Central Graben have been mapped. A shallow hydropressure system exists down to 1000–2000 m, underlain by a transition zone where pressures abruptly increase to the fracture level where overburden and fluid pressure are in balance. Under the transition zone, a geopressure zone exists to 3000–4000 m, within which pressures increase with depth at a hydrostatic rate. In the centre of the graben, this compartment is underlain by a second transition zone and a deep, high temperature, high pressure zone. The location and depth of the boundaries of the two upper pressure compartments and transition zones are more dependent on temperatures than lithologies or tectonic movements. Within the deep, high pressure zone, variations in pressure gradients indicate the presence of a number of smaller pressure cells, probably separated by faults. The identification and prediction of overpressured zones can have a significant effect on exploration programmes. From the drilling standpoint, prediction of sharp increases in pressure is a major safety factor, reducing the danger of well blowouts and allowing the operator to be adequately prepared for a number of drilling hazards. In potential reservoirs, overpressure reduces net overburden, thereby reducing porosity loss due to compaction. Sub-surface pressure variations have a significant effect upon hydrocarbon migration as oil and gas will attempt to move from high to low pressure compartments. Defining pressure variations from well to well can give indications of sealing and non-sealing faults. The pressure configuration has a significant effect upon the distribution of discovered hydrocarbons in the Central Graben. Most recoverable hydrocarbons are found in the first sealed permeable bed in the middle pressure compartment, overlying or adjacent to the transition zone above the deep, high pressure compartment. This includes the Cretaceous to Danian chalk fields in the centre of the graben and the Jurassic sand-reservoired fields on the northeast flank. Exploration in the deep, high pressure compartment has resulted in only limited success due mainly to poorer potential reservoir conditions, more difficult definition of traps and increased drilling expenses and risk.

Model for episodic flow of high-pressure water in fault zones before earthquakes

In this model for the evolution of large crustal faults, water that originally came from the country rock saturates the initially highly porous and permeable fault zone. During shearing, the fault zone compacts and water flows back into the country rock, but the flow is arrested by silicate deposition that forms very low permeability seals between the fault zone and the country rock. Because of variations in temperature and mineralogical composition and the complex structure of the fault zone, a three-dimensional network of seals is formed in the fault zone itself; thus, the high-pressure fluid is not evenly distributed. As in deep oil reservoirs, the fluid will be confined to seal-bounded fluid compartments of various sizes and porosity that are not hydraulically connected with each other or with the hydrostatic regime in the country rock. When the seal between two of these compartments is ruptured, an electrical streaming potential will be generated by the sudden movement of fluid from the high-pressure compartment to the low-pressure compartment. When the pore pressure in the two compartments reaches its final equilibrium state, the average effective normal stress across them may be lower than it was initially, and, if the two compartments are large enough, this condition may trigger an earthquake. During an earthquake, many of the remaining seals will be ruptured, and the width of the fault zone will increase by failure of the geometric irregularities on the fault. This newly created, highly porous and permeable, but now wider fault zone will fill with water, and the process described above will be repeated. Thus, the process is an episodic one, with the water moving in and out of the fault zone, and each large earthquake should be preceded by an electrical and/or magnetic signal.

Hypertension - en circulus vitiosus: patofysiologiske synspunkter

SummaryThe changes in function and structure of the high pressure compartments in experimental hypertension in animals are briefly reviewed. Several studies have demonstrated a gradual restructuring of the high pressure compartments, characterized by media hypertrophy in the arterioles and muscular hypertrophy in the left ventricular wall. Functional studies in spontaneously hypertensive rats have demonstrated a gradual change in the haemodynamics from a hyperkinetic circulation in the early phase to a hypokinetic circulation when the hypertension has been established and lasted for several months.Based on personal data the central haemodynamics in man with essential hypertension is discussed. A recent 10-year haemodynamic follow-up study in untreated essential hypertension is presented. These results are consistent with the concept of a similar restructuring of the high pressure compartments also in man with essential hypertension. Over the 10-year period, there was a decrease in cardiac index at rest an...

Direct-Current Generators for Electrostatic Precipitation

IN the English Electric Co.'s Journal for October, a description is given of the high-pressure D.C. dynamos it constructs for use in electrostatic precipitation plant. The Whessoe Foundry and Engineering Co., Ltd., specialises in apparatus for fog and mist extraction, and the English Electric Co.'s dynamos are specially designed to work with its plant. The removal of suspended particles from large volumes of gas is an important commercial problem at the present time. Electrostatic precipitation is now regarded as the most efficient and economical method for cleaning gases. The English Electric Co. has designed many high-pressure D.C. machines for radio transmission purposes, and the new dynamos are based on the experience gained in radio work. The generating unit for a typical equipment has to supply a current of about 0.15 amperes at a pressure of 45 kilovolts. The unit consists of a driving motor made to suit the local supply, coupled to three generators connected in series. The frames of the machines are insulated from the earth by individual supports of solid porcelain. The whole of the high-pressure apparatus is enclosed by screens which separate it from the driving motor and prevent unauthorised access. A simple interlock on the door renders it impossible for anyone to enter the high-pressure compartment when the generators are running. As a further precaution, every conductor which is at high pressure when the machine is running is connected with the earth when the set is at ‘standstill’. Accidental shocks are thus avoided. A notable feature of the set is its ability to withstand a short circuit without a ‘flash-over’. A model precipitation equipment was shown in action at the English Electric Co.'s exhibition last November.