Small Annulus Research Articles

Sand Control in Horizontal Wells in Heavy Oil Reservoirs

Abstract Horizontal wells are of great interest to most oil companies operating inheavy oil fields. Due to more extensive contact with the reservoir, horizontalwells allow fluid flow at lower fluid velocities yet providing total flowswhich are economic. While horizontal wells have the potential to make many moreheavy oil reservoirs economic, one of the most pressing concerns has been to beable to complete the wells properly. Unfortunately, likely candidates ofhorizontal wells are mostly "quicksand" type formations and thecritical velocities of sand in a wellbore is extremely low. Consequently, sandis very likely to enter the horizontal wellbore if not preventive measure istaken. Problems of sand production in a horizontal well is more complicatedthan in a vertical well due to difficulty in cleaning sands in horizontalwellbores. The present study discusses the problems of sand production in ahorizontal well and offers production in a horizontal well and offersrecommendation in controlling them. Physical simulation of the top part of thehorizontal well showed that both gravitational and inertial forces helpminimizing sand production. This will mean that increasing flow rates willdecrease sand production. Experimental evidence showed that production. Experimental evidence showed that selection of liner diameter and wire spacingare important parameters in controlling sand productions. Permeability damagedue to particle productions. Permeability damage due to particle mixing in theannulus was quantified. It was shown that smaller annulus is of more importancein the case of smaller wire spacing, lower oil viscosity and thinner payzone. Introduction Sand production is considered to be one of the major problems that haveperplexed the petroleum industry. Every year the petroleum industry spendsmillions of dollars in sand cleaning, repair problems related to sandproduction and lost problems related to sand production and lost revenues dueto restricted production rates. Consequently, sand control has been a researchtopic for over five decades. Uncontrolled sand production is very expensive dueto additional production is very expensive due to additional operating expenses(such as pump change, well cleanup, etc.), lost revenues, and creation ofpotentially hazardous situation. These problems are potentially hazardoussituation. These problems are magnified for horizontal or slanted wells forwhich well cleaning technique is not trivial. Additional expenses associatedwith sand production include clean out and disposal of sand and workover coststo return the well to production. The lost revenue due to restricted orcompletely shut in production is often a hidden expense and not alwaysproduction is often a hidden expense and not always considered in economiccalculations. Most of the early research work conducted by petroleum industry involved indesigning largest petroleum industry involved in designing largest practicalsizes of gravels and liners with the practical sizes of gravels and liners withthe notion that this will also lead to highest production rates. For manyyears, the philosophy of production rates. For many years, the philosophy of" if all sand production is stopped, the fluid production will bestopped" seemed to dominate the production will be stopped" seemed todominate the petroleum industry. Recent research efforts, petroleum industry. Recent research efforts, however, have focused on completion and control whilemaintaining highest well productivity. Sand control Methods Sand control methods may be classified as mechanical, chemical andmechanical/chemical. Mechanical methods of sand control prevent sand productionby stopping the formation with liners, production by stopping the formationwith liners, screens or gravel packs. Larger formation sand grains are stopped, and they in turn stop smaller formation sand grains. Chemical control methodsinvolve in injecting consolidating materials into the formation to cement thesand grains. A combination of plastic consolidated gravel and screen may beused to controls and in some wells to provide increased stability to the pack.provide increased stability to the pack. Reasons For Sand Production Sand production occurs when the stresses on the formation exceeds thestrength of the formation.

Convective Boiling in Narrow Concentric Annuli

An experimental apparatus was used to simulate the annulus formed by a single tube passing through a tube support plate (TSP) in the steam generator of a PWR nuclear power plant. It was found that the extent of thin film evaporation, compared to nucleate boiling, is larger for smaller annuli, with a transition at 0.203 mm gap width to a local dryout/rewet condition. A model was developed that predicts an increasing extent of surface dryout/rewet prior to critical heat flux (CHF). A CHF correlation was developed by modification of a pool boiling CHF correlation, and the Chen (1966) correlation was modified to allow prediction of the two-phase heat transfer coefficient.

Use of balloon dilatation to treat supravalvar pulmonary stenosis developing after anatomical correction for complete transposition.

Eight balloon dilatations were performed in five patients (aged from 10 to 37 months) in whom supravalvar pulmonary stenosis developed after anatomical correction for complete transposition. The ratio of the maximum diameter of the inflated balloon to the narrowest pulmonary arterial diameter varied from 1.6 to 3.3. In three patients with an initial ratio of less than or equal to 2 dilatation was repeated with a larger balloon. The right ventricular systolic pressure ranged from 0.70 to 1.25 of the simultaneously measured femoral arterial systolic pressure. The major stenosis was in the main pulmonary artery in four patients and at the pulmonary arterial bifurcation in one. After balloon angioplasty in the four patients there was no significant improvement in the ratio of right ventricular to femoral arterial systolic pressure or in the angiographic appearance. There was no change in the pressure ratio after angioplasty in the patient who had a major stenosis of the pulmonary arterial bifurcation and mild main pulmonary artery narrowing. There seemed to be a slight angiographic improvement in the bifurcation stenosis but at restudy two months later the angiographic improvement had disappeared. Balloon angioplasty of supravalvar pulmonary stenosis developing after anatomical correction for complete transposition was not successful in eight procedures. This lack of success may be attributable to a small pulmonary annulus with consequent multiple levels of stenosis and distortion of the main pulmonary artery.

Aortic valve debridement by ultrasonic surgical aspirator: A word of caution

Aortic stenosis was relieved in 11 patients by ultrasonic debridement of the valve and annulus, while 102 other patients underwent valve replacement for aortic stenosis during 1988. Debridement was selectively applied based on findings of small annulus size (19 mm or less) and extensive calcification. Additional patient characteristics were mean transvalvular gradient of 78 mm Hg, advanced age, and marked left ventricular hypertrophy. Six patients had no residual gradient and 5 others a mean gradient less than 10 mm Hg. There were no complications related to the debridement process. Intraoperative transesophageal Doppler echocardiography demonstrated improved leaflet mobility and elimination of the gradient in all patients and elimination of associated valvular insufficiency in 2 patients. Follow-up echocardiography demonstrated late onset of new valvular regurgitation in 5 patients that was progressive and required reoperation in 3. Thickened, hardened, and retracted valve leaflets with loss of central coaptation were found in all 3 patients who underwent reoperation. Ultrasonic debridement can effectively relieve aortic stenosis, provide an excellent immediate hemodynamic result, and decrease operative time. However the early occurrence of aortic insufficiency in a high percentage of patients makes it an unacceptable alternative to valve replacement, and the technique should be abandoned as a treatment for severe calcific aortic stenosis.

Palliative Percutaneous Balloon Valvuloplasty in a Cyanotic Child With Tetralogy of Fallot

We have presented the case of an 8-month-old child who had tetralogy of Fallot with severe pulmonary stenosis and minimal infundibular stenosis. Because of the relatively small annulus (10 mm) and young age of the infant, total correction was deferred, and a percutaneous palliative pulmonary balloon valvuloplasty was done. At the end of the procedure, he had neither cyanosis nor signs of congestive heart failure, and after four months of follow-up, he had only mild cyanosis with activities.

Experimental studies of critical heat flux for low flow of water in vertical annuli at near atmospheric pressure

Experiments are performed to measure the critical heat flux (CHF) for low flow of water in vertical annuli near atmospheric pressure (0.118 MPa). CHF data are collected for water inlet subcooling ranging from 44 K (or 182 kJ kg−1) to 75 K (or 312 kJ kg−1), and mass fluxes from 0 to 260 kg m−2 s−1. The CHF values vary from 155 kW m−2 for zero inlet flow to a maximum of 1418 kW m−2 for a water mass flux of 260 kg m−2 s−1. The data are classified and correlated according to the flow transition which occurred at CHF. Two CHF correlations are developed, one for the slug-churn and the churn-annular flow transitions and the other for the annular-annular mist flow transition. The heat flux at incipient flow chugging is also measured and found to vary from a minimum of about 40% of the CHF values in the smallest annulus (annulus ratio = 1.575) to a maximum of approximately 88% of CHF in the other larger annuli (annulus ratio = 1.72 and 2.0). Results also show that the heat flux at incipient chugging increases as either the water mass flux or inlet subcooling increases. The CHF values for zero inlet flow are predicted within ±25% using Block and Wallis' flooding correlation.

Effect of Excessive Retardation on the Physical Properties of Cement Slurries

Summary As well depths become greater over-retardation becomes more and more commonplace. Precise retarder response is difficult to attain at high temperatures and many cementing slurries end up with thickening times far in excess of what is considered good practice. To avoid sensitive retarder concentration, field blends often show thickening times of more than 6 hours for jobs where 3 to 4 hours is sufficient. Excessive thickening time has been commonly considered detrimental to good cement jobs, but the effect of over-retardation on cement properties was mostly derived from theoretical speculation. Through an extensive laboratory study, thickening time retardation is correlated to static gel strength development, initial set, and early compressive strength. The results indicate that moderate retardation has minimal effect on static cement properties. For deep wells, thickening times up to 10 hours do not appear to be detrimental to early compressive strength at bottomhole static temperature (BHST). Introduction The design of cement slurries and the actual techniques used for cementing hot, deep casings and liners becomes especially important under severe conditions. Most of these conditions complicate slurry design. Some of the more critical design parameters are high-pressure gas sands, lost circulation problems that limit amounts of hydrostatic pressure, and small hole-pipe annuli. Previous work on cementing long, deep liners and casings has been directed at increasing the displacement efficiency of the gelled or immobile mud from the annulus. This displacement problem has been addressed in many papers and studied in great detail. Another very important but sometimes overlooked aspect of deep-well cementing that merits attention is the performance of the cement slurry in the static state after it is placed in the annulus. The first basic design test that every proposed deepwell cement slurry undergoes is a thickening time determination. This value is a dynamic measurement of the hydration of the cement at bottomhole circulation temperature (BHCTI) and pressure (BHP). Many times, this is the only datum that is readily available to indicate how well the cement will perform after placement. It is important to be able to determine to what extent changes in a cement thickening time affects the cement's ability to support the pipe and to control gas flow as it develops compressive strength. The dynamic thickening time must be related to critical cement properties occurring after placement. Because temperature is the most important condition affecting hydration of cement, it is also critical to determine the effects of downhole temperature on the cement slurry properties. To study these phenomena fully, the following subjects are analyzed on the basis of laboratory collected data.What is the relationship between the laboratory measured thickening time and the actual hydration (and set) of the cement under downhole conditions?What is the correlation of thickening time with gel strength development and the corresponding annular gas flow potential?At what point will we actually see over-retardation influence the properties of the cement slurry (gel strength development, set time, and compressive strength development)?In deep applications from 3048 m to 4877 m [10,000 to 16,000 ft] how do temperature differentials between the top of cement (TOC) and bottom of cement (BOC) affect static gel strength, bonding, sealing, and compressive strength development?What are some design criteria that could enhance cement performance in deep, hot applications and limit waiting-on-cement (WOC) time? Scope and Testing Program The mechanism of hydration that a cement undergoes is a complicated process. Some of the variables that influence this process are water content, admixes, stirring time, temperature, and pressure. The two conditions that cannot be modified by design are the downhole temperature and pressure, with temperature being the most critical. Thickening time measurements are conducted on cement slurries at the BHCT and BHP. From a design standpoint, thickening time should provide enough time to place the slurry with ample safety factor to allow for unexpected job difficulty. The safety factor desired for each job varies from company to company. JPT P. 1357^

Posterior Enlargement of the Small Annulus during Aortic Valve Replacement versus Implantation of a Small Prosthesis

Twenty-two patients with a small aortic annulus were identified among 196 consecutive patients undergoing aortic valve replacement (AVR). The 11 patients in Group 1 underwent posterior enlargement aortic annuloplasty, and the 11 in Group 2 received a small aortic prosthesis (less than or equal to 21 mm). The two groups were unselected. Core hypothermia, cardioplegia, and local cooling were employed for all operations. Isolated AVR was performed in 3 patients in each group. In Group 1, the mean increase in diameter of the annulus was 4.82 mm, which resulted in a mean area increase of 169.91 mm 2 (51.7%). Mean aortic cross-clamp times were 140.4 minutes and 93.5 minutes in Groups 1 and 2, respectively. There were 2 operative deaths in Group 1, and 1 operative and 1 late death in Group 2. Mean follow-up was 26.5 months for Group 1 and 43.4 months for Group 2. No thomboembolic or bleeding episodes have been recorded. Considerations and conclusions are offered from the study of this small series of patients.

Combined Annular and Supraannular Prosthetic Implantation for the Small Aortic Annulus

A simple new technique allows the implantation of a large-sized prosthesis in an aorta with a small annulus with or without a hypoplastic aortic route. Results in 2 patients are described.

Flow in a small annulus between concentric cylinders

Rotationally symmetric vortex flows between concentric cylinders with the inner one rotating and the outer one at rest have been investigated by numerical simulation and by laser-Doppler velocimetry for an annulus of aspect ratio Γ = 1.05 with a radius ratio η = 0.5066. Stationary states and relaxation towards them were explored close to the transition from the primary flow, which is mirror symmetric with respect to the midplane of the annulus, to a flow which gradually loses the symmetry. Detailed comparison of numerically simulated and measured velocity fields is made.

Stratified two‐phase flog of molten polymers in circular dies

AbstractA theoretical study has been carried out on the steady, axisymmetric two‐phase flow of molten polymers in circular dies. For both fluids, the shear rate dependence of the viscosity is described by a power law and the temperature dependence by an exponential function. Taking into account viscous dissipation, a numerical program has been developed to predict the radial position of the interface between the two fluids, the developing temperature and velocity fields, the shear rates, the shear stresses, the pressure drop as well as the field of shear deformation and the residence time distribution for different thermal boundary conditions. The numerical program is applied to the flow of a high‐viscous polymer melt, (high density polyethylene), surrounded by a small annulus of less viscous polymer ni lt, (low density polyethylene). Computed results are shown graphically.

Responses of bipolar cells in the retina of the turtle.

The responses of bipolar cells in the retina of the turtle have been studied by intracellular recording. Two types of bipolar cell have been identified: one gave graded depolarizing and the other graded hyperpolarizing responses to small circles of light (100 mum diameter). The responses of both types of cell were similar in the following respects.1. Both were extremely sensitive to dim light; the amplitude of response to a small circle of light increased with light intensity more steeply than the cone response.2. Enlarging the diameter of a spot added an antagonistic effect which decreased response amplitude. This decrease in response amplitude was more apparent at dim than at bright light. Stimulating only distant areas of retina with an annulus produced a response of polarity opposite to that normally produced by a central spot. However, the responses of bipolar cells did not appear to be due to a simple summation of opposite polarity signals contributed from central and peripheral parts of their receptive fields.3. When small spots or annuli of light were turned off there frequently occurred an overshooting OFF transient. The occurrence of OFF transients depended on the duration of the stimulus. Cones recorded under similar conditions produced an OFF depolarization. The size of cone OFF depolarizations increased with increasing duration of the preceding light; following approximately 3 sec of illumination their maximum amplitude was roughly 1/10 the amplitude of the preceding hyperpolarization. The size of OFF responses in both cone and bipolar cells was increased when horizontal cells were hyperpolarized by light. It is concluded that bipolar cells produce large responses for very small cone responses, and, as a consequence, a small depolarization in cones following illumination produces large OFF transients in bipolar cells. Furthermore, the responses of bipolar cells do not appear to represent a simple summation of opposite polarity input from receptor and horizontal cells.

Unisurv report no. 9

Summary: Investigations into pointing to sharp, high and low contrast targets in photogrammetry have revealed that pointing accuracies are linearly dependent on the width of the annulus or “edge ribbon”, around the measuring mark for large annuli. For very small annuli, however, the relationship is more complex. While no firm explanations have as yet been put forward which explain the processes involved, the Mach phenomenon has been proposed as a contributing factor. Based on the method developed by the author in a previous work, a study of images actually seen by the visual system has been carried out, in an effort to explain pointing accuracies via this image, rather than by purely geometric properties in the annulus.

Bisection into small annuli

Bisection into small annuli

The ultrastructure of the flagella of three chrysomonads with particular reference to the mastigonemes

The structure of the smooth and the pantonematic flagellum of Mallomonopsis paxillata is described using the negative staining of whole organisms. Little of interest is visible on the smooth flagellum, but details of scales and mastigonemes can be seen on the flimmer-flagellum. The former are small annuli, and the latter tube-like structures with a loose helix of fibrous material wound round them. The mastigonemes of Synura petersenii and Mallomonas striata are also examined and appear to be essentially similar. The main difference lies in the number of thin filaments extending from the mastigoneme tips. The fine structure of the mastigonemes are described and discussed in detail. The mastigonemes also have a basal rigid portion ending in a sharp kink. This structure is discussed with relation to the movement of the organism.

ATRIAL GRAFT FOR RIGHT VENTRICULAR OUTFLOW TRACT ROOF. AN EXPERIMENTAL STUDY.

Complete relief of the outflow tract obstruction of the right ventricle is essential for successful surgical correction of the tetralogy of Fallot. Pulmonary valvulotomy and/or infundibulectomy will be adequate in many cases. In others, however, a significant narrowing will remain. This is usually a consequence of a small pulmonary valve annulus and some hypoplasia of the proximal main pulmonary artery, but it may be due to a small infundibular region (even after extensive resection of infundibular muscle), or in some instances to a combination of these abnormalities. A roof must be used in these cases to widen further the right ventricular outflow tract. Various materials have been used to construct a patch for this area. This report concerns the long-term evaluation of free grafts of autogenous right atrium used for this purpose. Materials and Methods Mongrel dogs were anesthetized, and moderate hypothermia was induced by immersion. Bilateral thoracotomy was performed;

Electron Microscopy of Amoeba proteus*†

SYNOPSIS. Thin sections of Amoeba proteus, fixed in osmium tetroxide and embedded in methacrylate, were examined in the electron microscope. The fine structure of various protoplasmic components is described. The plasmalemma, or cell membrane, varies in thickness and structure. These variations may be due to variations in physiological state, or they may be due to differences in preparation. Along its cytoplasmic edge is always present a definite line approximately 0.01 to 0.02 μ thick. The mitochondria, or beta granules, exhibit a structure similar to that of the mitochondria of several other protozoa and comparable to that of the mitochondria of other animals. In definite association with the membrane of the food vacuole are dense, rounded particles which in size are below the limit of resolution of the light microscope. Such dense particles are much less frequently present in the hyaloplasm and in association with the plasmalemma. A possible relationship to the neutral red granules associated with food vacuoles of Paramecium is suggested. The contractile vacuole possesses a thin membrane surrounded by a much thicker circum‐vacuolar zone of irregular strands which may form a three‐dimensional network around the membrane. This may represent the contractile element of the vacuole. A single layer of mitochondria is closely apposed to the circum‐vacuolar zone. Many small vacuoles and irregular vesicles are present throughout the cytoplasm. At times there occur groups of small, thin‐walled vesicles, which may correspond to an endoplasmic reticulum. The nuclear envelope consists of a thick inner porous layer and a thinner outer layer that is continuous yet is marked by the presence of numerous small annuli, each apparently surrounding a pore. In its structure, this outer layer appears to correspond to the entire nuclear envelope of many other cell forms.

Initiation of Explosives by Adiabatic Compression of their own Vapour

PREVIOUS work has shown that the sensitivity of liquid explosives to impact is greatly increased by the presence of minute gas bubbles1. The initiation is of a thermal nature and is due to the adiabatic compression and heating of the trapped bubbles. A simple method of including a gas space in an explosive is to spread it as a small annulus on a flat anvil. When this is struck with a flat hammer, the small amount of gas in the centre is trapped and compressed.

Memoirs: On the Antennal Musculature in Insects and other Arthropods

The first antennae of arthropods are divisible into two main types, viz. (1) segmented antennae and (2) annulated antennae. In the first type the antenna consists of a variable number of segments, each having intrinsic musculature. The antennae of the Ohilopoda, Diplopoda, Pauropoda, Symphyla, Collembola, and Thysanura Entognatha all pertain to this type; also, the first antennae of many Copepoda and Ostracoda. In the second type the antenna consists of a peduncle or protopodite composed of one or more segments, each with intrinsic musculature. Distally it bears an annulated flagellum, or a pair of flagella, devoid of intrinsic muscles and whose movements are effected by muscles originating within the peduncle. The first antennae of the Crustacea Malacostraca and the antennae of the Thysanura Ectognatha and of all the Insecta Pterygota belong to this type. The greatly elongated antennae of the Schizotarsia are intermediate between these two types. They are composed of an immense number of small annuli and an elaborate intrinsic musculature is present, thus allowing these appendages a wide range and flexibility of movement. The absence of intrinsic muscles in the antennal flagellum throughout the Insecta Pterygota and the Malacostraca appears to be irreversible in the sense that such muscles are never reacquired. It thus lends support to the generalization known as Dollo's Law. The presence of segmented antennae in the Thysanura Entognatha affords additional evidence in support of the Symphylan theory of the ancestry of insects.