A Transient Model for Hydraulic Simulation of Bullheading and Pressurized Mud Cap Drilling

2016 ◽  
Author(s):  
Abrar Akram Ghauri ◽  
Kjell Kåre Fjelde ◽  
Johnny Frøyen
Keyword(s):  
Numerical Scheme ◽  
Transient Flow ◽  
Downward Flow ◽  
Transient Model ◽  
Hydraulic Simulation ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Fracture Pressure ◽  
Drilling Technique ◽  
Production Wells

Bullheading is the process of pumping fluids into the well without circulating back to surface. This operation can be carried out for several reasons. In well control, this can be an alternative well kill approach in situations where conventional kill methods do not apply. When considering the pressurized mud cap drilling technique, bullheading is used for controlling pressures when drilling highly fractured and vugular carbonate formations. Bullheading is also carried out for killing production wells prior to workover operations. For a bullheading operation to be successful one need to ensure that the correct flow rate is chosen to overcome gas migration. This countercurrent to downward flow situation is best described using transient flow simulators to correctly predict what kind of rates and fluid volumes that are required. In addition, a transient flow model can also predict what kind of pressures that will be experienced during the operation to ensure that equipment and fracture pressure limitations are not exceeded. This paper aims at giving an overview of the application and challenges associated with bullheading operations for different type of well operations including the pressurized mud cap drilling technique. Then a mathematical model and a numerical scheme (AUSMV) that can be used for simulating the transient dynamics of a bullheading operation will be described. The drift flux model combined with a slip law will be used. Here special emphasize will be given on describing how we made the numerical scheme second order to reduce effects associated with numerical diffusion. The numerical boundary treatment and handling of flow regime transitions will also be described since one will here alternate between different conditions like cocurrent, countercurrent and downward flow. Two simulation scenarios will be considered. In the first example, a kick scenario will be considered and it will be shown how the transient model can be used to predict the effect of using different bullheading rates when trying to kill the well. Both time and depth variables will be visualized. The model can also predict how large volumes are required for a successful bullheading operation for a given rate. In the second example, it will be shown how the model can be used for simulating the alternating conditions experienced in a pressurized mud cap drilling operation. Here one will have a situation where surface pressure will build up if a kick is migrating in the closed annulus and if the pressure reaches a certain level, the kick has to be bullheaded back into the formation. This process can be repeated several times. The paper will show that the transient model proposed can provide good insight into the dynamics of bullheading and pressurized mud cap drilling. The model seems to be robust in handling the alternating flow conditions. Finally, some words will be said with respect to what is considered as important with respect to improving the modelling.

Use of a Transient Model for Studying Kick Migration Velocities and Build-Up Pressures in a Closed Well

2021 ◽  
Author(s):  
Thea Hang Ngoc Tat ◽  
Dalila Gomes ◽  
Kjell Kåre Fjelde
Keyword(s):  
Flow Model ◽  
Transient Flow ◽  
Flow Patterns ◽  
Drilling Fluids ◽  
Transient Model ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Gas Kick ◽  
Flux Model ◽  
Migration Velocities

Abstract The objective of the paper is to show that using pressure build-up curves for estimating kick migration velocities can be unreliable. This will be demonstrated by using a transient flow model where different flow patterns including suspended gas are considered. Suspended gas will occur in Non-Newtonian drilling fluids. This can also be the reason why there is reported large discrepancies in literature about what the gas kick migration velocities can be. A transient flow model based on the drift flux model supplemented with a gas slip relation will be used. The model will be solved by an explicit numerical scheme where numerical diffusion has been reduced. Different flow patterns are included i.e. suspended gas, bubble flow, slug flow and transition to one-phase gas. Kick migration in a closed well will be studied to study how pressure build-ups evolve. A sensitivity analysis will be performed varying kick sizes, suspension limits and changing the transition intervals between the flow patterns. It is seen in literature that the slope of the pressure build-up for a migrating kick in a closed well has been used for estimating what the kick velocity is. It has been reported earlier that this can be an unreliable approach. In the simulation study, it is clearly demonstrated that the suspension effect will have a significant impact of reducing the slopes of the pressure build-ups from the start of the kick onset. In some severe cases, the pressure builds up but then it reaches a stable pressure quite early. In these cases, the kick has stopped migrating in the well. However, in the cases where the kicks are still migrating, it seems that the bulk of the kick moves at the same velocity even though the degree of suspension is varied and gives different slopes for the pressure build-up. Hence, it seems impossible to deduce a unique gas velocity from different pressure build-up slopes. However, abrupt changes in the slope of the pressure build-up indicate flow pattern transitions.

Local Liquid Velocity in Vertical Air-Water Bubbly Downward Flow

2003 ◽  
Author(s):  
Xiaodong Sun ◽  
Sidharth Paranjape ◽  
Seungjin Kim ◽  
Hiroshi Goda ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Liquid Velocity ◽  
Laser Doppler Anemometry ◽  
Downward Flow ◽  
Drift Flux Model ◽  
Local Characteristics ◽  
Drift Flux ◽  
Local Measurements ◽  
Flux Model ◽  
Local Conductivity ◽  
Inner Diameter

Local characteristics of the liquid phase in downward air-water bubbly and slug flows were investigated in a 50.8-mm inner-diameter round pipe. A laser Doppler anemometry system was used to measure axial liquid velocity and its fluctuations. To reduce the measurement uncertainty, the experiments were performed in flow conditions with low void fraction. The comparisons between the liquid flow rates measured by the magnetic flow meter and those obtained from the local measurements showed good agreements. In addition, based on the LDA measurements and the data acquired by the local conductivity probes, the local relative velocity distribution, the distribution parameter and the drift velocity in the drift-flux model were obtained for the current downward flow.

Dynamic Cuttings Slip Velocity Evaluation in Non-Newtonian Fluids Using a Temperature Dependent Transient Drift-Flux Model for Directional Wells

2018 ◽  
Author(s):  
Ekaterina Wiktorski ◽  
Dan Sui ◽  
Kjell Kåre Fjelde ◽  
Vebjørn Langåker
Keyword(s):  
Numerical Scheme ◽  
Slip Velocity ◽  
Newtonian Fluids ◽  
Experimental Results ◽  
Velocity Variation ◽  
Cuttings Transport ◽  
Hole Cleaning ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flux Model

The objective of drilling a well is to prepare a clean hole without obstructions for further casing and production tubing running. Cuttings transport has always been important, but challenging process, especially when drilling long directional wells. Poor hole cleaning causes severe problems, as stuck pipe, extreme torque and drag, difficulties in casing landing, cementing, etc. Extensive studies of cuttings transport, both theoretical and experimental, have been performed to estimate, for example, cuttings concentration and cuttings slip velocity to determine optimal conditions for effective hole cleaning. This paper presents a dynamic analysis of cuttings transport in non-Newtonian fluids based on a transient drift-flux model and an associated numerical scheme AUSMV (advection upstream splitting method) developed by Evje and Fjelde 2002. In this paper, the scheme is modified to simulate cuttings transport dynamically taking into account effects related to pressure, temperature and cuttings slip. During drilling, the heat is transported from the formation into the wellbore and up to the surface. In this paper, the energy balance is enhanced by introducing an analytical temperature model into the AUSMV scheme. The temperature distribution along the well is calculated at the beginning of simulation and kept constant throughout the simulation. Additionally, the AUSMV scheme is improved by considering drilling fluid’s transport- and thermal properties. Transport properties of an oil-based mud, such as viscosity and density, are obtained from experiments. The experimental results were used to determine the coefficients in a linear density model used in the study to investigate the effect of non-Newtonian behavior on the heat transfer, cuttings transport and downhole pressure. Furthermore, a model to calculate the apparent viscosity at various pressures and temperatures was developed based on the experimental results and used to evaluate the impact of viscous forces on the cuttings distribution in the well. Presented numerical scheme solves dynamic cuttings transport problems taking into account the slip velocity variation with wellbore geometry, operational (controllable) parameters and formation properties. In comparison to the traditional steady-state models, the transient cuttings transport model with integrated depth-dependent parameters gives a possibility to achieve a more realistic simulation of cuttings transport, distribution and accumulation along the wellbore through the time.

Local Liquid Velocity in Vertical Air-Water Downward Flow

2004 ◽  
Vol 126 (4) ◽  
pp. 539-545 ◽  
Author(s):  
Xiaodong Sun ◽  
Sidharth Paranjape ◽  
Seungjin Kim ◽  
Hiroshi Goda ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Liquid Flow ◽  
Liquid Velocity ◽  
Laser Doppler Anemometry ◽  
Two Phase ◽  
Downward Flow ◽  
Flow Rates ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Local Measurements ◽  
Flux Model

This paper presents an experimental study of local liquid velocity measurement in downward air-water bubbly and slug flows in a 50.8 mm inner-diameter round pipe. The axial liquid velocity and its fluctuations were measured by a laser Doppler anemometry (LDA) system. It was found that the maximum liquid velocity in a downward two-phase flow could occur off the pipe centerline at relatively low liquid flow rates and this observation is consistent with other researchers’ results. The comparisons between the liquid flow rates measured by a magnetic flow meter and those obtained from the local LDA and multi-sensor conductivity probe measurements showed good agreement. In addition, based on the local measurements the distribution parameter and the drift velocity in the drift-flux model were obtained for the current downward flow tests.

Interfacial Structures and Regime Transition in Co-Current Downward Bubbly Flow

2004 ◽  
Vol 126 (4) ◽  
pp. 528-538 ◽  
Author(s):  
S. Kim ◽  
S. S. Paranjape ◽  
M. Ishii ◽  
J. Kelly
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Superficial Velocity ◽  
Phase Flow ◽  
Two Phase ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flow Parameters ◽  
Interfacial Structures ◽  
Flux Model

The vertical co-current downward air-water two-phase flow was studied under adiabatic condition in round tube test sections of 25.4-mm and 50.8-mm ID. In flow regime identification, a new approach was employed to minimize the subjective judgment. It was found that the flow regimes in the co-current downward flow strongly depend on the channel size. In addition, various local two-phase flow parameters were acquired by the multi-sensor miniaturized conductivity probe in bubbly flow. Furthermore, the area-averaged data acquired by the impedance void meter were analyzed using the drift flux model. Three different distributions parameters were developed for different ranges of non-dimensional superficial velocity, defined by the ration of total superficial velocity to the drift velocity.

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