The Experts below are selected from a list of 408540 Experts worldwide ranked by ideXlab platform
Runar Nygaard - One of the best experts on this subject based on the ideXlab platform.
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full fluid solid cohesive finite element model to simulate near wellbore fractures
Journal of Energy Resources Technology-transactions of The Asme, 2015Co-Authors: Saeed Salehi, Runar NygaardAbstract:This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore Region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.
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Full Fluid–Solid Cohesive Finite-Element Model to Simulate Near Wellbore Fractures
Journal of Energy Resources Technology, 2014Co-Authors: Saeed Salehi, Runar NygaardAbstract:This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore Region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.
Saeed Salehi - One of the best experts on this subject based on the ideXlab platform.
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Thermoporoelastic Modeling of Time-Dependent Wellbore Strengthening and Casing Smear
Journal of Energy Resources Technology, 2016Co-Authors: Raj Kiran, Saeed SalehiAbstract:One of the most critical aspects in the drilling operation is to reduce the nonproductive time and to avoid the borehole instability issues such as kicks, blow outs, lost circulation, stuck pipe, and breakouts. To investigate these problems, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In the previous research on this field, the factors were widely discussed and results obtained were related to the formation properties. However, while considering the stresses in the wellbore, the mechanical factors such as the RPM and contact of casing at different positions in wellbore have usually been neglected. In furtherance to this study, the importance of thermal condition, fluid loss, and filter cake formation study cannot be out ruled. This work includes a new insight toward understanding the stress redistribution due to pipe contact by the wellbore and smear mechanism. Additionally, it presents the numerical analysis of influence of casing contact and downhole thermal conditions using the finite-element analysis. The classical equations used to obtain the wellbore stresses include very few parameters such as the far-field stresses, pore pressure, and wellbore geometry. They do not consider the influence of casing contact while drilling, mud-cake permeability, and elastic and inelastic properties of the formation. To take into account the effects of these parameters, finite-element analysis is carried out considering the above-mentioned parameters in various scenarios. The main objective of these simulations is to investigate the hypothesis of the increase in hoop stress considering casing contact with regard to formation stresses orientation. The study of different cases shows the variation of a few hundred psi of hoop stress. However, the thermal effect on the near-Wellbore stress Regions can be important for drilling in deep water and other complex drilling environments. To see the thermal effect, this study develops a thermoporoelastic model. It is found that there is decrease in radial stress and hoop stress in near-Wellbore Region with time. This reduction will have a considerable impact on fracture initiation pressure in the near-Wellbore Region. Also, the smearing effect will be influenced by stress changes due to change in temperature.
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full fluid solid cohesive finite element model to simulate near wellbore fractures
Journal of Energy Resources Technology-transactions of The Asme, 2015Co-Authors: Saeed Salehi, Runar NygaardAbstract:This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore Region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.
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Full Fluid–Solid Cohesive Finite-Element Model to Simulate Near Wellbore Fractures
Journal of Energy Resources Technology, 2014Co-Authors: Saeed Salehi, Runar NygaardAbstract:This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore Region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.
J.-c. Roegiers - One of the best experts on this subject based on the ideXlab platform.
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Double Porosity Finite Element Method for Borehole Modeling
Rock Mechanics and Rock Engineering, 2005Co-Authors: J. Zhang, J.-c. RoegiersAbstract:This paper considers the mechanical and hydraulic response around an arbitrary oriented borehole drilled in a naturally fractured formation. The formation is treated as a double porosity medium consisting of the primary rock matrix as well as the fractured systems, which are each distinctly different in porosity and permeability. The poro-mechanical formulations that couple matrix and fracture deformations as well as fluid flow aspects are presented. A double porosity and double permeability finite element solution for any directional borehole drilled in the fractured porous medium is given. Compared with conventional single-porosity analyses, the proposed double-porosity solution has a larger pore pressure in the matrix and a smaller tensile stress in the near-Wellbore Region. The effects of time, fracture, mud weight, and borehole inclination in the double-porosity solution are parametrically studied to develop a better understanding of physical characteristics governing borehole problems.
T.m. Habashy - One of the best experts on this subject based on the ideXlab platform.
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Application of the MR-CSI Method for Three-Dimensional Imaging of the Triaxial Induction Measurements
IEEE Transactions on Geoscience and Remote Sensing, 2010Co-Authors: A. Abubakar, T.m. HabashyAbstract:We present a nonlinear inversion method for 3-D imaging of the near-Wellbore Region employing multiarray triaxial induction data. The method used is the so-called multiplicative-regularized contrast source inversion method. There are two main features of this method. The first is that the method does not require the explicit solution of the full forward problem at each iteration step. The second is that the regularizer is included as a multiplicative constraint that allows the automatic and adaptive determination of the regularization parameter. These two features enable us to robustly solve a large-scale inverse problem using single-processor present-day computer power.
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Three-Dimensional Single-Well Imaging of the Multi-Array Triaxial Induction Logging Data
SEG Technical Program Expanded Abstracts 2006, 2006Co-Authors: A. Abubakar, T.m. HabashyAbstract:We present a rigorous nonlinear inversion method for three-dimensional (3D) imaging of the near-Wellbore Region employing multi-array triaxial induction data. The method used is the so-called Multiplicative-Regularized Contrast Source Inversion (MR-CSI) method. There are two main features of this method. The first is that the method does not require the explicit solution of the full forward problem at each iteration step. The second is that the regularizer is included as a multiplicative constraint that allows the automatic and adaptive determination of the regularization parameter. These two features enable us to robustly solve an inverse problem with 65,536 unknowns using single-processor present-day computer power.
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A 3D near-Wellbore Imaging Algorithm for Triaxial Induction Data
68th EAGE Conference and Exhibition incorporating SPE EUROPEC 2006, 2006Co-Authors: A. Abubakar, T.m. HabashyAbstract:We present a rigorous nonlinear inversion method for the three-dimensional (3D) imaging of the near-Wellbore Region employing multi-array triaxial induction data. The method used is the so-called Multiplicative-Regularized Contrast Source Inversion (MR-CSI) method. There are two main features of this method. The first is that the method does not require the explicit solution of the full forward problem at each iteration step. The second is that the regularizer is included as a multiplicative constraint that allows the automatic and adaptive determination of the regularization parameter. These two features enable us to robustly solve an inverse problem with 65,536 unknowns using a single-processor present-day computer power.
Catalin Teodoriu - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Back Pressure Effects on Transient Gas Flow Through Porous Media via Laboratory Experiments and Numerical Simulation
Volume 5: Materials Technology; Petroleum Technology, 2014Co-Authors: Xiaolei Liu, Gioia Falcone, Akkharachai Limpasurat, Catalin TeodoriuAbstract:When developing a transient numerical reservoir simulator, it is important to consider the back pressure effects that waves propagating from one end of the porous medium will have on the temporal distribution of pore fluid pressure within the medium itself. Such waves can be triggered by changing boundary conditions at the interface between reservoir and wellbore. An example is given by the transient reservoir response following pressure fluctuations at the wellbore boundary for gas wells suffering from liquid loading.Laboratory experiments were performed using a modified Hassler cell to mimic the effect of varying downhole pressure on gas flow in the near-Wellbore Region of a reservoir. Gauges were attached along a sandstone core to monitor the pressure profile. The results of the experiments are shown in this paper.A numerical code for modelling transient flow in the near-Wellbore Region was run to mimic the experiments. The comparisons of simulations and laboratory test results are presented here, for the initial and final steady-state flowing conditions, and where the inlet pressure was maintained constant while initiating a transient pressure build up at the core outlet.The concept of the U-shaped pressure profile along the near-Wellbore Region of a reservoir under transient flow conditions, originally proposed by Zhang et al. [1], was experimentally and numerically reproduced for single-phase gas flow. This is due to a combination of inertia and compressibility effects, leading to the reservoir response not being instantaneous. The results suggest that, in two phase gas-liquid conditions, liquid re-injection could occur during liquid loading in gas wells. From the experimental results, the U-shaped curves were more obvious and of longer duration in the case of greater outlet pressure. The transition from the initial to the final steady state condition occurred rapidly in all the cases shown here, with the U-shaped pressure profile appearing only over a relatively short time (at the small scale and low pressures tested in this study).Copyright © 2014 by ASME
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Modeling fully transient two-phase flow in the near-Wellbore Region during liquid loading in gas wells
Journal of Natural Gas Science and Engineering, 2010Co-Authors: He Zhang, Gioia Falcone, Catalin TeodoriuAbstract:Abstract In oil and gas field operations, the dynamic interactions between reservoir and wellbore cannot be ignored, especially during transient flow in the near-Wellbore Region. A particular instance of transient flow in the near-Wellbore Region is the intermittent response of a reservoir that is typical of liquid loading in gas wells. Despite the high level of attention that the industry has devoted to the alleviation of liquid loading, the fundamental understanding of the associated phenomena is still surprisingly weak. This applies not only to the flows in the wells, but also to the ways in which these flows interact with those in the reservoir. This paper presents the results of a numerical modeling effort using bespoke code written at Texas A&M University, to identify the pressure profile in the near-Wellbore Region during fully transient flow conditions for a synthetic, low permeability gas reservoir. The results show a “U-shaped” pressure profile along the reservoir radius in the near-Wellbore Region. The existence of such pressure profile might explain the re-injection of the heavier liquid phase into the reservoir during liquid unloading in gas wells. A comparison of the results with those obtained using a commercial reservoir simulator show the limitations of the latter, which is unable to mimic re-injection of the liquid into the near-Wellbore Region.
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Relative Permeability Hysteresis Effects in the near-Wellbore Region During Liquid Loading in Gas Wells
SPE Latin American and Caribbean Petroleum Engineering Conference, 2010Co-Authors: He Zhang, Gioia Falcone, Catalin TeodoriuAbstract:In oil and gas field operations, the dynamic interactions between reservoir and wellbore cannot be ignored, especially during transient flow in the near-Wellbore Region. A particular instance of transient flow in the near-Wellbore Region is the intermittent response of a reservoir that is typical of liquid loading in gas wells. Our previous numerical simulation study (Zhang et. al. 2009 and 2010) successfully captured the liquid backflow rates resulting from bottomhole pressure (BHP) oscillations typical of liquid loading, and emphasized their detrimental effect on gas production. This paper presents a numerical modeling effort to investigate the relative permeability hysteresis effects in the near-Wellbore Region during transient flow conditions for a synthetic, low permeability gas reservoir. Firstly, the previously validated "U-shaped?? pressure profile along the reservoir radius was generated with an increased BHP from a starting steady-state flowing configuration. This pressure profile can lead to reinjection of the liquid phase into the reservoir. The BHP was then let to decrease, with a corresponding temporary recovery in gas productivity. With subsequent BHP oscillations, the flow direction was allowed to switch back and forth, which could represent a typical liquid loading scenario. The Killough method was used to calculate the relative permeability hysteresis during the various imbibitions and drainage processes. The results reveal that the hysteresis effect is negligible at a high-frequency alternation of imbibition and drainage in the near-Wellbore Region, and may therefore not be significant in liquid loading problems.
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Numerical Modeling of Fully-Transient Flow in the near-Wellbore Region During Liquid Loading in Gas Wells
Latin American and Caribbean Petroleum Engineering Conference, 2009Co-Authors: He Zhang, Gioia Falcone, Peter P. Valko, Catalin TeodoriuAbstract:In oil and gas field operations, the dynamic interactions between reservoir and wellbore cannot be ignored, especially during transient flow in the near-Wellbore Region. A particular instance of transient flow in the near-Wellbore Region is the intermittent response of a reservoir that is typical of liquid loading in gas wells. Despite the high level of attention that the industry has devoted to the alleviation of liquid loading, the fundamental understanding of the associated phenomena is still surprisingly weak. This applies not only to the flows in the wells, but also to the ways in which these flows interact with those in the reservoir. The classical way of dealing with these interactions, inflow performance relationships (IPRs), relate the inflow from the reservoir to the pressure at the bottom of the well, which is related to the multiphase flow behavior in the tubing. These relationships are usually based on steady-state or pseudo steady-state assumptions. However, such IPRs may be inadequate when a transition from an acceptable liquid loading regime to an unacceptable occurs over a relatively small range of production rates and, hence, over a relatively short time. The most satisfactory solution would be to couple a transient model for the reservoir to a transient model for the well. This paper presents the results of a numerical modeling effort focused on the identification of the transient pressure profile in the near-Wellbore Region during fully transient flow conditions. The preliminary results, obtained for a single-phase (gas) situation and for a three-phase (oil-water-gas) situation, show a "U-shaped" pressure profile along the reservoir radius. The existence of a similar pressure profile could be the explanation for the reinjection of the heavier phase into the reservoir during liquid unloading in gas wells.
