Amir Jahanbakhsh

Rapid Laser Manufacturing of Microfluidic Devices from Glass Substrates

Conventional manufacturing of microfluidic devices from glass substrates is a complex, multi-step process that involves different fabrication techniques and tools. Hence, it is time-consuming and expensive, in particular for the prototyping of microfluidic devices in low quantities. This article describes a laser-based process that enables the rapid manufacturing of enclosed micro-structures by laser micromachining and microwelding of two 1.1-mm-thick borosilicate glass plates. The fabrication process was carried out only with a picosecond laser (Trumpf TruMicro 5×50) that was used for: (a) the generation of microfluidic patterns on glass, (b) the drilling of inlet/outlet ports into the material, and (c) the bonding of two glass plates together in order to enclose the laser-generated microstructures. Using this manufacturing approach, a fully-functional microfluidic device can be fabricated in less than two hours. Initial fluid flow experiments proved that the laser-generated microstructures are completely sealed; thus, they show a potential use in many industrial and scientific areas. This includes geological and petroleum engineering research, where such microfluidic devices can be used to investigate single-phase and multi-phase flow of various fluids (such as brine, oil, and CO2) in porous media.

New Methodology for Numerical Simulation of Water-Alternating-Gas (WAG) Injection

Summary A new methodology is presented to simulate WAG injection scenarios. In addition to properly model three-phase flow, the concept of directional and cyclic hysteresis is modelled to capture the underlying physics. Laboratory measured data is used to validate the proposed methodology. The approach in this paper is based on updating parameters of WAG hysteresis model during the course of cyclic injection to adequately model the key physical mechanisms in WAG injection tests. For this study, we used ‘Modified Stone 1’ model for calculating three-phase relative permeability (kr) data from measured two-phase kr. We used Land’s parameter (C) and the reduction exponent (alpha) for gas secondary drainage relative permeability as the variable parameters in WAG hysteresis model for matching the coreflood production and pressure data. Results of this study showed that, by applying the proposed methodology for simulating WAG coreflood experiments at different wettability conditions, better match to the experimental data can be achieved. In this paper, we highlight the shortcomings of the current capability of numerical simulators for simulating WAG injection. Some areas of improvement to the current WAG hysteresis model is introduced and a new methodology is proposed to improve the performance of current simulation procedures for WAG injection scenarios.

Investigation of non-uniform saturation distribution effects on the interpretation of pressure and pressure derivate curves

ABSTRACT In this study the influences of non-uniform saturation distribution on the analysis and interpretation of pressure and pressure derivative curves is examined. The unusual behavior of the pressure transient data due to non-uniform saturation distribution makes the analysis of such reservoirs complicated and leads to ambiguity in the interpretation. In order to interpret the behavior of pressure transient data, which are influenced by changes of fluid saturation, a theoretical model is developed. The model application is demonstrated using a simulation in the reservoir containing oil and water with the variety of fluids saturation in the initial condition. The theoretical model provides a basis for understanding conclusions derived by numerical results as well as new insight for interpretation of pressure transient behavior affects by non-uniform saturation distribution.

Application of Ensemble Smoother and Multiple-data Assimilation for Estimating Relative Permeability from Coreflood Experiments

Relative permeability curves (kr) are flow functions governing multiphase flow in porous media. These functions are an essential component of any large-scale simulator of porous media flow of different phases (oil, water, and gas) with several applications in environmental and petroleum engineering. Unsteady state methods are commonly performed on core samples taken from subsurface reservoirs to obtain the relative permeability curves experimentally. The obtained measurements are then used to calibrate analytical functions (to be embedded in the flow simulator) through automatic history matching. In this study, we evaluate iterative ensemble-based history matching techniques based on the Ensemble-Smoother (ES) formulation. Mainly, the Ensemble Smoother with Multiple-Data Assimilation (ES-MDA) is used for calibrating the parametric relative permeability models using data from unsteady-state core flood experiments. An Ensemble-Smoother updates the model parameters globally by assimilating all the time depended data at once, from the start to the end of the experiment. This is to be contrasted with online updating scheme adopted in Ensemble Kalman Filtering methods. Recently, ES-MDA was developed to improve on ES and to provide reliable uncertainty quantification of the unknown parameters with low computational cost. In the current work, ES-MDA is compared to global optimization methods for calibrating the relative permeability curves. The results of estimating two and three-phase relative permeability curves from three-phase coreflood experiments are presented. The experiments were performed on 65 mD mixed-wet Clashach sandstone core and cumulative productions and pressure drop across the core were measured during the course of experiments. ES-MDA was able to find the global optimum parameters at much faster convergence rates in comparison to genetic algorithm (GA), a widely used global search method. This was evident for the history matching of three-phase unsteady state experiments where optimal solutions were obtained efficiently while preserving uncertainties in the estimated parameters.

On the Analysis of Well Test Data Influenced by Capillary Pressure

The focus of this study is on the analysis of capillary pressure effects on well test data. Ignoring the capillary pressure is one of the assumptions that have been applied in all multiphase well test analysis approaches. In this work we investigate the influences of capillary pressure on the analysis of pressure transient data in a solution gas drive reservoir and in a reservoir containing oil and water. Reservoir simulations were performed to generate pressure and saturation data for each case and the pressure responses and the fluids saturation distribution for drawdown and build-up tests for two cases with and without capillary pressure are compared. According to the results of this study, it has been concluded that the influences of capillary pressure on fluids saturation behavior in build-up test due to importance of capillary force than viscose force in this period is more noticeable. Though the effects of capillary pressure lead to differences in the fluids saturation behavior but the authors have not observed dissimilarity in the pressure responses affected by capillary pressure for draw down and build-up test in the both reservoirs under study.

The Influence of Multiphase Flow on the Interpretation of Pressure Transient Data in Multilayer Reservoirs With Cross Flow

The authors investigated multiphase flow effects on the analysis of pressure responses in layered reservoirs with cross flow. Virtually all studies on the subject of multiphase well test analysis have been carried out in single-layer reservoirs. However, many reservoirs are found to be composed of number of layers whose characteristics are different from each other and the wells in such reservoirs may be completed and produced from more than one layer. In order to examine the behavior of pressure data in multiphase multilayer reservoirs with interlayer communication several cases are considered. The contrast in phase saturations in each layer is the parameter of interest. For each case the applicability of conventional well test analysis is investigated and reservoir parameters such as phase mobilities, skin factor, and average reservoir pressure are compared with actual values. According to the results of this work, conventional multiphase well test analysis in the single layer reservoir can be used in layered reservoirs with cross flow; however, the data should be interpreted with care if horizontal saturation gradient in the layers is significant.