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Trondheim, Norway

Opstad G.B.K.,Petrell as
Chemical Engineering Transactions | Year: 2010

Intumescent materials have been applied for a long time to protect equipment and structure against fire exposure in chemical and petrochemical industry. In need of optimising use of protection, simulation by use of computer codes has been more and more applied. These codes are dependent on reliable property data as input to the code; data that are partly highly unreliably and partly non existent. The reason is that there is not yet developed a test method for testing of intumescing materials that can give reliable property data applicable in computer codes. Copyright © 2010, AIDIC Servizi S.r.l. Source

Jahani N.,Norwegian University of Science and Technology | Berge G.,Petrell as | Haugen B.,Petrell as
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

In low-permeability and low-porosity reservoirs, oil is trapped in the rock and cannot be extracted by conventional recovery. In this case, well stimulation techniques such as fracturing can be used to increase the permeability of the rock. Oneway ofwell stimulation is matrix acidizing. In matrix acidizing, acid is injected into the rock and reacts with it, etching the wall of its pores, and creating channels called "wormholes".Wormholes increase surface area and allow more fluid to drain to the well-bore, enhancing oil recovery. While acidizing increases oil production and recovery, it also increases the risk of rock collapse, especially wormhole walls. It is therefore important to predict the contrasting effects of increased production rate and decreased rock strength due to wormhole formation. For this reason an integrated model adapted for computer simulation is developed to investigate the multi-physical effect of acid injection in chalk reservoirs. The geometry for the numerical simulation is based on a previously published experimental work. Numerical simulation is based on control volume methods for fluid flow in porous media using a Darcy model, and stress analysis is based on the finite element method using a constitutive model of chalk. For computational simulation of this multiphysics simulation an in-house CFD-FEM (Computational Fluid Dynamics-Finite Element Methods) software, "Brilliant", is used. In this work, the mechanical stability of wormholes and chalk sample under uniaxial compaction load are investigated and are compared with an intact chalk. In presence of wormholes, wormhole walls are subject to shear failure, while the same places on the intact rock will fail by pore collapse at higher stresses. © 2014 Taylor & Francis Group, London. Source

Opstad K.,Petrell as | Berge G.,Petrell as | Holen J.K.,Statoil
Chemical Engineering Transactions | Year: 2010

The risk of fire in process plants containing flammable material requires precautions and protection of vulnerable components. To prevent escalation it is important that the process equipment retain its integrity during fire exposure. Studies have shown that flanges are among the weakest points in a process. Calculation of fire resistance of flanges is considered rather complicated, since it involves thermal conduction through fire insulation in complex geometries of metal and voids of air, stress of bolts, all depending on temperature history. This paper presents results of a 4" ASME flange, from a project where experiments and calculations of a number of 4" and 10" flanges have been conducted, to explore the issue. The jet fire test series includes flanges with and without passive fire protection. Copyright © 2010, AIDIC Servizi S.r.l. Source

Jahani N.,Norwegian University of Science and Technology | Jahani N.,Petrell as | Haugen B.,Norwegian University of Science and Technology | Berge G.,Petrell as
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

Acid injection in a carbonate oil reservoir can increase oil recovery by etching a part of the fractured porous reservoir and generating conductive channels ("wormholes"), which creates an easier path for oil production. However, it is crucial to predict the wormhole and reservoir strength and their failure for a successful acid treatment. For this purpose, a continuum-based computational method is developed. The model includes flow in the porous chalk reservoir, flow in the wormhole and reversible and irreversible deformation of chalk and fractures, which are modeled with an equivalent elasto-plastic damage constitutive model. The coupling between the reservoir flow and the fractured chalk deformation is done by explicit coupling method. The results found that the risk of the wormhole's walls failure is higher if the natural fractures are oriented along the wormhole; however, natural fractures with larger dip angles and higher inclinations in respect to the wormhole increase the risk of the rock failure. Results shows that increased fluid production from the wormhole, which can be the result of the further acid treatments, developing irreversible behaviors of the rock and reduces the natural fracture asperity at the wormhole's tip, in addition to increasing the wormhole's wall deformation, eventually leading to the wormhole's occlusion. © 2015 Elsevier Ltd. Source

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