Pressure Surge Research Articles

Computation of Surge-Pressure-Wave Propagation During Cementation Process

SummaryIn this paper, we present a method of modeling surge pressures and wave propagation that can occur during well execution. The surge pressures have an effect on formations [i.e., formation fracture resulting in mud losses and nonproductive time (NPT)]. Knowing the amplitude of surge pressure in advance can lead to operation redesign to avoid losses. Swab- and surge-pressure waves can occur at numerous events during well execution. For example, during liner operations, pressure waves can occur at dart landing or plug shearing, liner-hanger setting, or clearing a plugged shoe-track component. It is possible for surge-pressure waves to create fractures in shale and sand layers (i.e., when surge-pressure-wave amplitude exceeds formation fracturing resistance).A transient-state physical model is built to compute pressure-wave propagation through drillstring, casing, and open hole to predict the amplitude of a surge-pressure wave and to warn when a fracture might occur in the formation, to avoid mud losses and NPT.In the model, continuity and energy partial-differential equations (PDEs) are built for a cylindrical fluid element contained in an elastic hollow cylinder. The method of characteristics is applied to convert the PDEs to ordinary-differential equations (ODEs). The ODEs are solved numerically to compute pressure distribution along well depth and in time. The model is implemented as a graphical-user-interface (GUI) tool to be used by drilling engineers at the design phase of a well to avoid losses. The GUI tool is targeted to address different scenarios that take place during the cementation process. To date, the transient-state physical model has been applied successfully in various applications, such as monodiameter technology, running casing, and perforating operations. Two cases are studied, one for a well in the Gulf of Mexico (GOM) where mud losses have been reported, and the other for a well in Malaysia where no mud losses have occurred. Pressure-wave computations are performed with the GUI tool for the two cases. The results of both cases are presented in this paper and show that formation fracture can be predicted by the GUI tool and subsequent losses can be avoided.

Analysis and determination method of addition mud density in casing program design

The addition mud density is a key part of drilling fluid design to avoid drilling accidents resulting from the pressure surge. However, the current standard of addition mud density is empirical and whether this empirical value can be applied to all wells, especially deep wells, deserves further study. In this paper, in order to quantitatively calculate the variation of downhole pressure during tripping, the transient wellbore surge pressure calculation model during tripping was established and verified by field data fist. Then, through the analysis of the surge pressure and its influencing factors during tripping, it was found that the current standard of addition pressure difference cannot be used as an empirical value for different sections of a well, while the addition mud density was more reasonable for the open hole safety in casing program design. However, the surge pressure was much smaller than the lower limit of current standard addition mud density under the actual working conditions. On the other hand, through the analysis of the wellbore pressure variation and its influencing factors when gas kick occurs, it was found that the variation of bottom hole pressure caused by gas kick was much smaller than that caused by tripping. Therefore, the surge pressure should be the main factor in the determination of addition mud density. Based on this, the determination method of addition mud density for each tripping section was proposed, which can calculate the addition mud density quantitatively and more reasonably for each tripping section based on the comprehensive consideration of factors such as wellbore pressure variation and formation pressure prediction error. The results showed that the current standards of addition mud density are too conservative in medium and shallow formations and may not meet the safety requirements in deep formations.

Computational Study of Gas-Solid Flow in a Horizontal Stepped Pipeline

In this paper, the mechanism governing the particle-fluid flow characters in the stepped pipeline is studied by the combined discrete element method (DEM) and computational fluid dynamics (CFD) model (CFD-DEM) and the two fluid model (TFM). The mechanisms governing the gas-solid flow in the horizontal stepped pipeline are investigated in terms of solid and gas velocity distributions, pressure drop, process performance, the gas-solid interaction forces, solid-solid interaction forces, and the solid-wall interaction forces. The two models successfully capture the key flow features in the stepped pipeline, such as the decrease of gas velocity, solid velocity, and pressure drop, during and after the passage of gas-solid flow through the stepped section. What is more important, the reason of the appearance of large size solid dune and pressure surge phenomena suffered in the stepped pipeline is investigated macroscopically and microscopically. The section in which the blockage problem most likely occurs in the stepped pipeline is confirmed. The pipe wall wearing problem, which is one of the most common and critical problems in pneumatic conveying system, is analysed and investigated in terms of interaction forces. It is shown that the most serious pipe wall wearing problem happened in the section which is just behind the stepped part.

Challenge pressure surge - which tasks have engineering and HAZOP?

Challenge pressure surge - which tasks have engineering and HAZOP?

Fatigue crack growth analysis of surge line under thermal stratification conditions

As the connection between the pressurizer and the main pipeline of nuclear reactor, thermal stratification occurs in the pressurizer surge line during the operation. The thermal stratification through the pipe wall increases the possibility of plastic deformation and fatigue failure in the nozzle, tee, elbow and weld. So it is of great significance to carry out research on the fracture mechanics of surge line under thermal stratification conditions. Therefore, in this paper, based on the results of finite element analysis and ASME specifications, and with the results of pipeline stress analysis under temperature and pressure transient loads, the fatigue crack growth analysis of the surge line under thermal stratification conditions is carried out, and the technical means of suppressing crack propagation is explored, which provides a reference for the safe operation of the surge line of the nuclear power plant.

Nocturnal dipping status and the association of morning blood pressure surge with subclinical target organ damage in untreated hypertensives.

The authors aimed to investigate the association between sleep-through morning surge (MS) in blood pressure (BP) and subclinical target organ damage in untreated hypertensives with different nocturnal dipping status. This cross-sectional study included 1252 individuals who underwent anthropometric measurements, serum biochemistry evaluation, 24-hour ambulatory blood pressure monitoring, echocardiography, and carotid ultrasonography. Left ventricular mass index, left atrial dimension, and carotid intima-media thickness were evaluated. Participants were grouped according to nocturnal systolic BP dipping rate (388 dippers, 10%-20%; 674 non-dippers, 0%-10%; 190 reverse dippers, <0%). Twenty-two extreme dippers were excluded. While reverse dippers exhibited the most severe signs of damage, only dippers showed significant and positive correlation between MS and hypertension-mediated organ damage (all P<.05), with significant area under the receiver operating characteristic curve for discriminating left ventricular hypertrophy (0.662), left atrial enlargement (0.604), and carotid intima-media thickening (left, 0.758; right, 0.726; all P<.05). MS showed significant association with subclinical organ damage on both logistic and multiple linear regression analysis adjusted for age, sex, body mass index, smoking status, and alcohol consumption status, as well as for the levels of fasting blood glucose, uric acid, serum creatinine, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol, even when 24-hour, daytime, nocturnal, and morning systolic BP were included (odds ratio >1 and P<.01 for all types of damage). Besides race, nocturnal dipping status might affect the role of MS in subclinical target organ damage, with a significant association only in dippers, independent of other systolic BP parameters. Dipping status might account for the discrepancies across previous reports.

Prognostic value of average real variability of systolic blood pressure in elderly treated hypertensive patients.

The independent prognostic significance of ambulatory blood pressure variability in the elderly is incompletely clear. We investigated the prognostic value of average real variability of 24-hour blood pressure in elderly treated hypertensive patients. The occurrence of a combined end-point including stroke, coronary events, heart failure requiring hospitalization and peripheral revascularization was evaluated in 757 elderly treated hypertensive patients. According to tertiles of average real variability of 24-hour systolic blood pressure patients were classified as having low (≤8.66 mmHg; n = 252), medium (8.67-10.05 mmHg; n = 252) or high (>10.05 mmHg; n = 253) average real variability. During the follow-up (6.9 ± 3.4 years, range 0.4-12.9 years), 195 events occurred. The event rate of the population was 3.74 per 100 patient-years. After adjustment for age, sex, previous events, diabetes, estimated glomerular filtration rate, left ventricular hypertrophy, left atrial enlargement, asymptomatic left ventricular systolic dysfunction at baseline, 24-hour systolic blood pressure, non-dipping and dipping with high morning surge of blood pressure, patients with high average real variability were at higher cardiovascular risk than those with low average real variability (hazard ratio 1.64, 95% confidence interval 1.12-2.40). In elderly treated hypertensive patients, high average real variability of 24-hour systolic blood pressure is associated with higher cardiovascular risk independently of other risk markers, average 24-hour systolic blood pressure and circadian blood pressure changes.

Online Surge Detection Method Based on Axial Displacement Sensor of MSCC

Magnetically suspended centrifugal compressor (MSCC) can get higher speed with no friction and improve transformation efficiency. However, with speed increases, air flows more easily to separate from the blade and cause the gas pressure unsteadily, which leads to surge occur, causing the system destroyed. Aiming at the problem that existing surge detection methods usually increase complexity or cannot detect surge in time, this paper proposes an online surge detection method and corresponding surge judgment criteria of MSCC system using the signal of axial displacement sensor based on adaptive interference canceller (AIC) and average phase forward linear predictor (APFLP). At first, the system model of the MSCC is established and the transfer function between surge pressure signal and rotor displacement signal is derived. On these basis, an AIC is designed to eliminate the synchronous vibration signal, which has serious interference to surge detection and an APFLP is designed to estimate the frequency of the surge signal. Finally, the simulation and experimental research of the new method are carried out. The simulation and experimental results show that the method can detect surge quickly and effectively.

FEATURES OF IMPLEMENTATION AND OPERATION OF PRESSURE WAVES SMOOTHING SYSTEMS IN OIL PIPELINE TRANSPORTATION

Background The scale of PJSC Transneft activities implies a high load and almost uninterrupted operation of the pipeline network. At the same time, during its operation, deviations from the standard modes of transportation, pressure pulsations and hydraulic shocks are possible, the consequences of which can damage equipment or cause damage to the pipe and oil outflow into the environment. A regular or abnormal shutdown of an aggregate or an entire intermediate oil pumping station (OPS) during pumping is accompanied by an increase in pressure, resulting in a steep pressure wave propagating upstream in the direction of the previous station. Due to friction losses, the initial perturbation decays, i.e. its slope and amplitude decrease in absolute value. Reaching the previous station, the increase in pressure wave leads to an increase in pressure at the station outlet. To maintain the setpoint at the LPS outlet, the automatic control system (ACS) of the pressure creates a wave of pressure reduction (vacuum). If the speed of the ACS is not enough to offset the surge pressure, the pressure at the outlet of the pump station can reach the setpoint for the operation of the corresponding station overpressure protection. The action of general station protection comes down to shutting down a single pump or an entire station. When this protection is triggered, a wave of pressure reduction begins to propagate towards the incoming wave of pressure increase downstream. As a result of wave interference, the pressure decreases in the linear part of the pipeline. However, before the wave reaches the previous OPS, the pressure in the section between stations may exceed the allowable working pressure of the pipe sections, which can lead to depressurization of the pipeline. In most cases, in the Transneft system, the protection of line pipes sections from verpressure in transient processes caused by the disconnection of the main pumping unit or the whole pumping station is protected by means of pressure wave smoothing systems. Aims and Objectives The study aim is study of the issues of protection of trunk pipeline facilities from high-pressure waves arising from pressure pulsations, water hammer during normal or abnormal shutdown of pumping units or an intermediate pumping station as a whole, with unauthorized closure of valves, etc. Results The main aspects of the implementation of pressure wave smoothing systems are considered and the economic criteria for their installation on existing and projected oil pipelines are defined. An example is given of the calculation of non-stationary processes necessary to substantiate the expediency of using the high pressure pump at intermediate oil pumping stations. Presents the main types of system designs, features of their operation and planned maintenance.

Experimental investigation on two-phase flow instabilities in long-distance transportation of liquid oxygen

Two-phase instabilities are inevitably encountered in the cryogenic transport process, which are significant for the high-efficient utilization of cryogenic fluids as well as the safe operation of cryogenic devices, especially for long distance transportation systems. An experimental study is performed on a 200-meter-long transfer system with liquid oxygen to investigate the details with respect to the cryogenic two-phase instabilities. The fluid pressure, temperature as well as flow rate along the conveying pipelines are measured, and the pipeline chill-down, tank chill-down, filling and parking steps are conducted sequentially. The results demonstrate the important role of gas forced convection for long pipelines, and reveal the flow and thermal performance of chill-down process. The system damage caused by chill-down pressure surge might be possibly avoided through properly controlling the inlet pressure of the pipeline and simultaneously chill-down efficiency can be improved. Besides, the geyser phenomenon with 8 min duration and 0.18 MPa pressure amplitude was observed in a 10-meter-high vertical pipeline during the parking process, and the consumption rate of cryogenic fluids was greatly increased.

Mitigation of flow-induced pressure fluctuations in a Francis turbine operating at the design and partial load regimes—LES simulations

High-fidelity large eddy simulations (LES) were conducted to characterize the spatial and temporal structure of turbulent flows in an industrial-sized Francis turbine while the unit operated at the design point and partial load. A pressure surge with an amplitude of 8% of the turbine head was observed at partial load while the amplitude was <1% at the design point. The vortex rope precession observed in the draft tube correlated to the amplitude and frequency of the pressure surge. Central and peripheral water injections at various volumetric rates were considered to control the flow-induced pressure fluctuations. Central injection at the 4% and 6% flow rates attenuated high amplitude pressure fluctuations by 40% and 75% respectively at partial load. At the same operating conditions, peripheral injections did not have the same desired effect. Although power generation was not changed with water injection at the design point, it was reduced by about 2.5% by central injection and 0.5% by peripheral injection at partial load, showing a water injection mitigation strategy could be applied without any penalty.

A Pressure-based Compressible-Liquid Flow Model for Computation of Instantaneous Valve Closure in Pipes

A generalized, pressure-based compressible-liquid flow model is proposed for the isothermal low-speed flow of liquids. The flow model incorporates dedicated equations of state for liquids into the pressure-based solvers to simulate the compressible effects in liquids. The model’s capability to handle compressible liquid flow problems is evaluated against the well-established density-based water-hammer model. The isothermal flow problem of an instantaneous valve closure in an irrigation pipe and the associated flow transients are numerically solved using the proposed model by employing the Tait equation of state in conjunction with a segregated pressure-based solver algorithm. The transient flow problem is solved for a range of operating pressures, and the surge in pressure and variation of other flow properties and their interrelations are studied in detail. The proposed model could successfully capture the entire physics of the problem, including the compressible modeling of the liquid involved and could produce high accuracy numerical results. The results suggest that the pressure-based compressible-liquid flow model is a reliable and computationally inexpensive numerical tool for isothermal low-speed compressible liquid flow computations.

Optimal valve closure operations for pressure suppression in fluid transport pipelines

When a valve is suddenly closed in fluid transport pipelines, a pressure surge or shock is created along the pipeline due to the momentum change. This phenomenon, called hydraulic shock, can cause major damage to the pipelines. In this paper, we introduce a hyperbolic partial differential equation &#x0028 PDE &#x0029 system to describe the fluid flow in the pipeline and propose an optimal boundary control problem for pressure suppression during the valve closure. The boundary control in this system is related to the valve actuation located at the pipeline terminus through a valve closing model. To solve this optimal boundary control problem, we use the method of lines and orthogonal collocation to obtain a spatial-temporal discretization model based on the original pipeline transmission PDE system. Then, the optimal boundary control problem is reduced to a nonlinear programming &#x0028 NLP &#x0029 problem that can be solved using nonlinear optimization techniques such as sequential quadratic programming &#x0028 SQP &#x0029. Finally, we conclude the paper with simulation results demonstrating that the full parameterization &#x0028 FP &#x0029 method eliminates pressure shock effectively and costs less computation time compared with the control vector parameterization &#x0028 CVP &#x0029 method.

Moderate morning rise in blood pressure has lowest risk of stroke but only in women.

The morning period which is recognized as the highest risk for cardiovascular events is associated with a surge in blood pressure (BP). However, it is unclear what aspect of this rise is important. To determine whether the rate of rise (RoR), the magnitude (day night difference) or the product [BP power (BPPower)] is associated with increased cardiovascular risk. We developed a logistic equation method to fit individual 24-h patterns of BP to determine RoR, amplitude and BPPower using the ambulatory recordings from the Ohasama study including 564 men and 971 women (16.6 years follow-up). Men had a higher risk of cardiovascular events than women (24, 16%, P < 0.001). Age and night BP were strong linear risk predictors. In men sorting risk by quintiles of BPPower (adjusted for age, night BP, smoking status) revealed no clear linear or nonlinear pattern. However, in women BPPower had a U-shaped relationship with the lowest risk being the 2-3rd quintile for all cardiovascular events (Pquadratic = 0.01) including cardiovascular death (Pquadratic = 0.03) and nonfatal stroke (Pquadratic = 0.02). A similar but less clear trend was observed with the RoR but only stroke (infarct) reached significance (Pquadratic = 0.03) while sorting by range showed a U shaped pattern for combined cardiovascular events (Pquadratic = 0.04). These findings suggest that the morning BPPower is an important independent risk factor for predicting cardiovascular events and stroke but only in women with median levels having the lowest risk.

THE MORNING BLOOD PRESSURE SURGE IN PATIENTS WITH HYPERTENSION

Objective: The aim of study was to definite validity and reliability of the new morning blood pressure surge (MBPS) assessment method in patients with arterial hypertension (AH).Design and method: We assessed 150 ambulatory blood pressure monitoring (ABPM) data of AH patients. ABPM monitor (Spacelabs 90207) was applied after the washout period. The new method determined the MBPS value as the difference between the mean BP during the period from 6 to 8 hours (for this period we determined the maximum rate of BP rise) and the minimum night BP (MBPS6_8/BPnigh_min). Test-re-test reliability (reproducibility) of the new method was determined as the correlation between the measurements of the first and second ABPM sessions carried out during the week (only for MBPS6_8/BPnigh_min indices). Construct validity of the new method was defined as the correlation between the MBPS6_8/BPnigh_min coefficient and left ventricular mass index (LVMI) (only for 98 patients). LVMI was measured using echocardiography (L. Teichholtz et all.). Results: The mean daytime BP was (M ± SD): systolic (SBP) – 141,1 ± 13,9; diastolic (DBP) – 90,1 ± 10,3 mm Hg. We found that the new method of MBPS assessment had a high degree of reliability: coefficient correlation (r) between parameters of the two ABPM sessions were (for MBPS6_8/BPnigh_min): for DBP r = 0,70, for SBP r = 0,83 (table 1). The validity of the new method was high: the MBPS value obtained using new method (MBPS6_8/BPnigh_min) correlated with LVMI (an objective factor of validation) (table 2). Conclusions: We found that the new method of the morning blood pressure surge assessment had a high level of validity and reproducibility (test-re-test reliability). The high reliability of the new method is probably due to the exclusion of subjective factors (patient's diary) in the evaluation of the MBPS value. The reference mean morning BP was determined for a fixed time period, and not by the patient's diary.

On the role of pore pressure in dynamic instabilities of saturated model granular materials

Drained triaxial axisymmetric isotropic and subsequently shear compression tests are performed on fully water-saturated short cylindrical samples of nearly monodisperse glass beads, initially assembled in a loose state by moist tamping and undercompaction technique. Both fully drained isotropic and shear tests are affected by dynamic instabilities triggered under uncontrolled isotropic or deviatoric stress. These dynamic instabilities encompass isotropic collapses, compression stick-slips and especially the unexpected isotropic liquefaction. The most reasonable but imprecise scenario points to a possible dynamical collapse of the granular structure triggered by a spontaneous failure of the force chains, generating an instantaneous surge of excess pore pressure in a fully saturated system. This paper aims in exploring the key role of pore pressure outburst on some global macroscopic parameters of these dynamic events. It focuses on the unforeseen, short-lived and stabilised excess dynamic pore pressure and proposes an in-depth assessment of the validity and the reliability of pore pressure measurements. Irrespective of loading condition (i.e. isotropic or drained compression shear) the ephemeral stabilised excess dynamic pore pressure controls the evolution of the axial and volumetric strains in an essentially dynamic consolidation process. Some appearance conditions for these unexpected dynamic instabilities are discussed.

Prognostic value of morning surge of blood pressure in middle-aged treated hypertensive patients.

We investigated the prognostic value of morning surge (MS) of blood pressure (BP) in middle-aged treated hypertensive patients. The occurrence of a composite end point (coronary events, stroke, and heart failure requiring hospitalization) was evaluated in 1073 middle-aged treated hypertensive patients (mean age 49years). Patients with preawakening MS of BP above the 90th percentile (27/20.5mmHg for systolic/diastolic BP) were defined as having high MS of BP. During the follow-up (mean 10.9years), 131 cardiovascular events occurred. After adjustment for various covariates, including known risk markers and ambulatory BP parameters, patients with high MS of systolic BP (hazard ratio 1.81, 95% confidence interval 1.10-2.96) and those with high MS of diastolic BP (hazard ratio 1.98, 95% confidence interval 1.19-3.28) were at higher cardiovascular risk than those with normal MS. In middle-aged treated hypertensive patients, high MS of systolic and diastolic BP is independently associated with increased cardiovascular risk.

Exploring the performances of the dual technique-based water hammer redesign strategy in water supply systems

Abstract This paper explored and compared the effectiveness of the inline and branching redesign strategies-based dual technique, implemented to enhance the conventional technique skills in terms of attenuation of positive and negative pressure surge magnitudes and limitation of the spreading of pressure wave oscillation period. Basically, this technique is based on splitting the single inline or branched plastic short-section, used in the conventional technique, into a couple of two sub-short-sections made of two distinct plastic material types. Investigations addressed positive and negative surge initiated water hammer events. Additionally, high and low density polyethylene materials were utilized for sub-short-section material. Results illustrated the reliability of the dual technique in protecting hydraulic systems from excessive pressure rise and drop, and evidenced that the (HDPE/LDPE) sub-short-sections' combination (where the former sub-short-section is attached to the sensitive region of the steel piping system parts, while the latter is attached to the second extremity of the steel piping system) is the most prominent configuration providing the best trade-off between pressure surge attenuation, and pressure wave oscillation period spreading. Lastly, it was found that the pressure head peak (or crest) and the pressure wave oscillation period values were markedly sensitive to the (HDPE) sub-short-section length and diameter.

INVESTIGATING USE OF PRESSURE PULSES TO ASSESS NEAR WELLBORE RESERVOIR PARAMETERS

Pressure surge in a pipe due to sudden flow rate change or full-stop of fluid flow is a pressure wave propagating in fluid along the pipe. This phenomenon has been used to determine the flow rate and to detect and monitor changes in effective flow diameter. It turns out that the pressure surge, also known as pressure pulse, can be used to estimate the formation transmissivity and storativity in the near wellbore region. In this study, propagation of pressure pulse generated by sudden valve closure is simulated with a transient pipe flow model, and it is coupled with a transient analytical reservoir model. The coupled model is used to estimate the reservoir parameters by history matching approach, which is to iterate the transmissivity and the storativity values until an acceptable match is obtained between the measured and simulated pressure history at the upstream of valve. The developed modeling and estimation scheme is applied with two data sets from a field well test to estimate reservoir parameters. The reservoir parameters transmissivity and storativity in the near wellbore region were obtained from the history matching analysis. Matching analysis with the coupled model on the recorded wellhead pressure during two tests showing obvious different flowing conditions points out very similar reservoir parameter values.

Functional Censored Quantile Regression

We propose a functional censored quantile regression model to describe the time-varying relationship between time-to-event outcomes and corresponding functional covariates. The time-varying effect is modeled as an unspecified function that is approximated via B-splines. A generalized approximate cross-validation method is developed to select the number of knots by minimizing the expected loss. We establish asymptotic properties of the method and the knot selection procedure. Furthermore, we conduct extensive simulation studies to evaluate the finite sample performance of our method. Finally, we analyze the functional relationship between ambulatory blood pressure trajectories and clinical outcome in stroke patients. The results reinforce the importance of the morning blood pressure surge phenomenon, whose effect has caught attention but remains controversial in the medical literature. Supplementary materials for this article are available online.