Compensation effect analysis in DIE method for through-casing measuring formation resistivity

The measuring technique based on Double-Injection-Electrodes (DIE) and its compensation arithmetic method have been proven to be very useful for eliminating the errors caused by electrode-scale mechanical tolerances in formation resistivity measurement through metal case. In this paper, we found that even minor casing joint or casing corrosion may deteriorate the measurement accuracy. Based on theoretical analysis and self-adaptive goal oriented hp-Finite Element (FE) simulations, the compensation effects of DIE measurement technique were estimated. The calculated results from this measuring method are always close to the real formation resistivity, regardless of whether the metal casing is ideal or not. Meanwhile, large errors occur when recording measurements based on Single-Injection-Electrodes (SIE), since the calculated formation resistivity may provide negative values when casing joint or casing corrosion exists. The Double-Injection-Electrode (DIE) measurement technique is predicted to have good compensation effects in many non-ideal situations with uneven metal casing besides electrode-scale mechanical tolerances.MTM2010 1651

New post processing method for interpretation of through casing resistivity (TCR) measurements

We propose a new iterative method for post processing through casing resistivity (TCR) measurements. This method can be seen as a correction or extension of Kaufman´s theory to more complex scenarios, in which the casing is no longer assumed to be uniform along the axis of the borehole. It can also be seen as a simplified inversion method based on the main physic al principles of TCR measurements. To derive our post processing method, we first use the method of images, which enable us to introduce all key factors involved on TCR measurements, including casing length, casing radius, casing thickness, formation resistivity, location of injected current and resistivity distribution of formation layers . Then, we design our iterative Post processing Method by simplifying the complex formulation resulting from using the method of images. Numerical results using goal oriented hp FEM simulations show that our correction method provides a more accurate approximation to the actual formation resistivity than that predicted by Kaufman´s theory. In addition, the new method is pr oven to be very efficient and robust, since it is independent of spatial resistivity variations in the formation.MTM2010 1651

Arithmetic method of double-injection-electrode model for resistivity measurement through metal casing

Through-casing resistivity (TCR) measurement instruments such as Cased Hole Formation Resistivity are extensively used for the dynamic monitoring of oil reservoirs during the production phase in oil wells to evaluate the residual oil distribution. However, two shortcomings still exist in the common TCR model based on single-injection electrodes: The real value of steel-casing resistance is difficult to acquire, and the effect from mechanical tolerances of electrode scale is unpredictable. This paper proposes an innovative model based on doubleinjection electrodes. In this new model, all the required variables can be measured simultaneously; furthermore, a compensating arithmetic method is employed to obtain the real casing resistance. Self-adaptive goal-oriented hp-finite-element simulations have been performed to prove that the influence of mechanical tolerances of electrode scale can be reduced effectively. Therefore, the TCR measurement accuracy is highly improved

Asymptotic Models for the Electric Potential across a Highly Conductive Casing

We analyze a configuration that involves a steel-cased borehole, where the casing that covers the borehole is considered as a highly conductive thin layer. We develop an asymptotic method for deriving reduced problems capable of efficiently dealing with the numerical difficulties caused by the casing when applying traditional numerical methods. We derive several reduced models by employing two different approaches, each of them leading to different classes of models. We prove stability and convergence results for these models. The theoretical orders of convergence are supported by numerical results obtained with the finite element method

Impedance Transmission Conditions for the Electric Potential across a Highly Conductive Casing

Borehole resistivity measurements are a common procedure when trying to obtaina better characterization of the Earth's subsurface. The use of a casing surrounding the boreholehighly complicates the numerical simulations due to a large contrast between the conductivities ofthe casing and the rock formations. In this work, we consider the casing to be a thin layer of uniformthickness and motivated by realistic scenarios, we assume that the conductivity of such casing isproportional to the thickness of the casing to the power of -3. We derive Impedance TransmissionConditions (ITCs) for the static (zero frequency) electric potential for a 2D configuration. Then,we analyse these models by proving stability and convergence results. Next, we asses the numericalperformance of these models by employing a Finite Element Method. Finally we present presentasymptotic models for similar configurations including the time-harmonic configuration and a 3Daxisymmetric scenario.Les mesures de résistivité en forage sont communément utilisées pour obtenirune meilleure caractérisation du sous-sol de la Terre. Pour obtenir de telles mesures, on utilisetypiquement un tube métallique qui protège le forage, mais cela complique énormément la sim-ulation numérique à cause du fort contraste entre les conductivités du tube et des formationsrocheuses. Dans ce travail , motivé par des configurations réalistes, on considère que la con-ductivité du tube est proportionnelle à l'épaisseur du tube à la puissance -3. On développe desconditions de transmission d'impédance (ITCs en Anglais) pour le potentiel électrique dans lecas statique, dans un domaine bidimensionnel. On présente la construction des modèles asymp-totiques, validés par des résultats de convergence. On illustre les résultats théoriques avec dessimulations numériques obtenues en utilisant une discrétisation par éléments finis. On présenteaussi des modèles asymptotiques pour d'autres problèmes et configurations, à fréquence non-nulleet en 3D

Modelling, Simulation and Data Analysis in Acoustical Problems

Modelling and simulation in acoustics is currently gaining importance. In fact, with the development and improvement of innovative computational techniques and with the growing need for predictive models, an impressive boost has been observed in several research and application areas, such as noise control, indoor acoustics, and industrial applications. This led us to the proposal of a special issue about “Modelling, Simulation and Data Analysis in Acoustical Problems”, as we believe in the importance of these topics in modern acoustics’ studies. In total, 81 papers were submitted and 33 of them were published, with an acceptance rate of 37.5%. According to the number of papers submitted, it can be affirmed that this is a trending topic in the scientific and academic community and this special issue will try to provide a future reference for the research that will be developed in coming years