bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overview of H2S Souring Cases in Argentina Reservoirs: Origin and Mitigation Scenarios
Authors: Cavallaro A. N. , Alberdi M. I. , Galliano G. R. 
Published: December 2007

Abstract
H2S is an element toxic to life that can be associated to natural gas, oil and production water. It is very dangerous to operational staff and causes corrosion-cracking and pitting of steels-, especially when it is associated to water.
The petroleum fields can early show H2S associated to the original fluids or it can appear later in mature stages. The generation mechanisms of H2S have been classified as biotic (biological sources) or abiotic (geological or geochemical sources). The first one is related to the development of Sulphate Reducing Bacteria (SRB) in reservoirs. The best-known reason is the injection of SRB with seawater in combination with nutrients of formation waters. Abiotic mechanisms involve only chemical reactions between organic, inorganic phases and water. Temperature and pressure are critical parameters: themochemical sulphate reduction (TSR), hydrolysis of metallic sulfhurs, cracking of organic compounds, cracking of kerogen and volcanogenic sources are examples of abiotic mechanisms.
According to this classification, most of the H2S souring cases in Argentina can be, on some level, related to the development of SRB, but alternative sources have been studied to explain the new reports of H2S on fields with high contents of original H2S. This paper classified the fields in Argentina with H2S in three categories;
The oilfields that show progressive H2S souring after a secondary recovery project. SRB were introduced with the injection of foreign waters and three examples are shown: Chihuido Lomitas, Barrancas and Las Heras-Cerro Grande (Cases A, B, C). A second group of oilfields report low concentrations of H2S still in primary production without previous history of H2S. SRB could be indigenous or introduced with drillings fluids. El Alba and Grimbeek fields are presented in this paper as Case D. A third group of fields show medium and high values of original H2S (&gt;2000 ppmv) since the firsts development activities. A possible contribution of abiotic H2S sources is now considered. Some fields in the Neuquen area could show a mixture of mechanisms (biotic and abiotic). The characteristics of these fields are summarized in Case E.
All reservoirs require H2S simulation to design surface pipelines and environment management. However, according to the origin of the H2S, a variety of mitigation and control technologies have already been implemented in these fields.
This paper summarizes the three groups of fields in Argentina that produce H2S, altogether with their water-chemistry, evidences of H2S origin, associated problems and control practices.
Numerical Simulation of Density-Driven Natural Convection in Porous Media with Application for CO2 Injection Projects
Authors: Farajzadeh R. , Salimi H. , Zitha P. L. J. , Bruning J. 
Published: December 2007

Abstract
In this paper we investigate the mass transfer of CO2 injected into a homogenous (sub)-surface porous formation saturated with a liquid. In almost all cases of practical interest CO2 is present on top of the liquid. Therefore, we perform our analysis to a porous medium that is impermeable from sides and that is exposed to CO2 at the top. For this configuration density-driven natural convection enhances the mass transfer rate of CO2 into the initially stagnant liquid. The analysis is done numerically using mass and momentum conservation laws and diffusion of CO2 into the liquid. The effects of aspect ratio and the Rayleigh number, which is dependent on the characteristics of the porous medium and fluid properties, are studied. This configuration leads to an unstable flow process. Numerical computations do not show natural convection effects for homogeneous initial conditions. Therefore a sinusoidal perturbation is added for the initial top boundary condition. It is found that the mass transfer increases and concentration front moves faster with increasing Rayleigh number. The results of this paper have implications in enhanced oil recovery and CO2 sequestration in aquifers.
Upscaling in Fractured Reservoirs Using Homogenization
Authors: Zanganeh M. Namdar , Salimi H. , Bruining J. 
Published: December 2007

Abstract
Homogenization is a powerful upscaling technique, which has been successfully applied to a variety of problems of interest, such as reactive contaminant transport and two phase flow in layered and fractured media. It has several advantages over other upscaling techniques, such as REV averaging. It does not use intuitive closure equations and it explicitly shows the dependence of the upscaled equations on the characteristic dimensionless numbers of interest. It is based on a well defined procedure, which precludes ad hoc assumptions. A disadvantage is that the underlying assumptions of this procedure have not received sufficient attention in the existing literature.
This paper examines the existing homogenization models for two phase flow in fractured media with the purpose to clarify the underlying physical assumptions. We give the derivation for a specific case for which we discuss the validity of the assumptions. Finally, we discuss an example to show the applicability of the ensuing model equations.
The Challenges of Developing a Deep Offshore Heavy-Oil Field in Campos Basin
Authors: Figueiredo F. P. , Branco C. C. M. , Prais F. , Salomão M. C. , Mezzomo C. C. 
Published: December 2007

Abstract
Deep offshore oil production demands very high investments (CAPEX) so its development must rely on a careful planning. This frequently takes place in a setting with very limited amount of information due to high costs of appraisal operations. The figure becomes even more complicated when heavy oils are the target: low energy reservoirs require water flooding which, in turn, reflects in low recoveries and excessive water handling, not to mention other production problems.
This paper highlights different simulation studies that have been performed in order to set up an economical development plan for a 16 API 1700m water depth oil reservoir offshore Campos Basin. The main reservoir consists of a high thickness turbidite channel crossed by a N-S fault whose hydraulic conductivity is the main uncertainty. Vertically the reservoir is composed of three zones, where the upper one has a gas cap partially in contact with the two bottom ones. These structural complexities required a detailed study for positioning injectors and horizontal producers based on a decision tree analysis. The impact of other uncertainty variables was also identified and studied: horizontal permeability, vertical to horizontal permeability ratio, water-oil relative permeability and productivity index. Particular attention was given to the injectivity decline due to the planned produced water re-injection. Vertical and horizontal injection wells performances were compared in a scenario under strict geomechanical restrictions. The simulation model was also used to evaluate the possibility of developing marginal areas close to the main reservoir body.
The study leaded to a robust strategy for the water injection scheme. Risk and marginal reservoir analysis helped the decision of the features of the future production system in terms of oil and liquid processing capacity and adoption of some flexibility to make feasible the future development of marginal areas.
Streamline-Based Simulator for Unstructured Grids
Authors: Pomata M. , Menéndez A. , Valle J. 
Published: December 2007

Abstract
Oil recovery operations are strongly conditioned by a series of complex phenomena that take place in the reservoir. Presently, it is common to use numerical modeling tools for the oilfield development.
In this paper we present the first implementation step of a streamline-based simulator for unstructured grids. In this stage, we focus on a 2D incompressible flow model. Streamline flow simulation has been extensively used for the past ten years, and it is now used as an effective and complementary tool to more traditional flow modeling approaches, such as finite differences.
Streamline-based simulation is suitable for large, geologically complex and heterogeneous systems, where fluid flow is dictated by well rates, rock properties, fluid mobility and gravity. Capillary effects and expansion-dominated systems are not modeled correctly using streamlines.
The mathematical model is based on the mass conservation of the three-phase system.
The basic hypothesis, as well as the mathematical model on which the streamline-based simulator stand, are presented in some detail.
We use the finite volume scheme as the numerical method for the discretization of the differential equations. Trinodal triangular elements are used. The pressure equation formulation is space centered with an upstream formulation for the phases mobilities and is solved using a direct skyline solver2. The 1D saturation equation is discretized using an explicit finite difference scheme in time and an upstream formulation in space.
The results obtained by our streamline-based simulator are compared with known analytical solutions (such as Buckley-Leverett flow) and with our previous full implicit black oil simulator. Good quantitative agreement is obtained.
Validating the Use of Experimental Design Techniques in Exploratory Evaluations
Authors: Amorim T. , Moczydlower B. 
Published: December 2007

Abstract
This work presents a validation of the use of Experimental Design (ED) techniques in exploratory evaluations. The results generated by a commercial software, which uses ED techniques combined with the Monte Carlo method, have been compared with 10,000 equivalent actual flow simulations. Several oil and gas real reservoirs were studied. The static and dynamic variables were selected from real prospect studies, as well as their respective range of variation. For each case studied, the commercial software planned a small number of flow simulations to run, applying different ED techniques. Based on the simulation results, a proxy model was generated using the Response Surface Method (RSM). Making use of this proxy model, it was possible to quickly simulate 10,000 experiments and to perform statistics calculations with the Monte Carlo method.
In order to verify the quality of the proxy, 10,000 simulation files were generated, with the exact same combinations of parameters used in the Monte Carlo method. A script was written to run automatically all the files and to register their results. Besides comparing the statistics generated by these two methodologies, it was possible to compare the actual results of each one of the 10,000 simulations.
The results indicate that the quadratic technique is the one with the best cost-benefit ratio and suggest that the proposed methodology generates reliable results in most cases. This reliability decreases when there are complexities in the flow model, such as well and group controls, water and/or gas reinjection, etc. However, results show that the range of possible results to be emulated by the proxy model is the most influential parameter in the quality of the results generated by it.
The quality of the risk analysis performed with these ED techniques is obviously influenced by the ability of the proxy model to emulate the flow simulator response. The efficiency of different ED techniques, in different reservoirs, was analyzed and the reliability and limitations of this evaluation methodology has been accessed.
A Quadrilateral Element-Based Finite-Volume Formulation for the Simulation of Complex Reservoirs
Authors: Hurtado F. S. V. , Maliska C. R. , da Silva A. F. C. , Cordazzo J. 
Published: December 2007

Abstract
In this work is presented a numerical formulation for reservoir simulation in which the element-based finite-volume method (EbFVM) is applied to the discretization of the differential equations that describe macroscopic multiphase flow in petroleum reservoirs. The spatial discretization is performed by means of quadrilateral unstructured grids, which are adequate for representing two-dimensional domains of any complexity in an accurate and efficient manner. Although mass conservation is enforced over polygonal control volumes constructed in a vertex-centered fashion, media properties are assigned to the primal-grid quadrilateral elements. In this way, non-homogeneous full tensor permeabilities can be handled straightforwardly. Piecewise bilinear shape functions are used for approximating the main variables in the differential equations. The exception is the advection term in the saturation equation, which is approximated by means of a twodimensional positivity-preserving upwind scheme. Numerical results without noticeable grid orientation effects were obtained using this type of approximation, even for the most adverse cases with high mobility ratios and piston-type displacements. Additionally, some simple problems with known analytical solution were solved in order to assess the accuracy of the method. We show that the approximation of the pressure field is second-order even for non-homogeneous anisotropic media. Finally, the ability for solving fluid displacements in faulted reservoirs of complex geometry was tested with a synthetic problem.
Quebrache–A Natural CO2 Reservoir: A New Source for EOR Projects in Mexico
Authors: Muro Heron Gachuz , Campos Sergio Berumen , Alcazar Cancino Luis O. , Rodríguez Pimentel José A. 
Published: December 2007

Abstract
CO2 injection is one of the most efficient methods used to improve oil recovery, and, as world statistics shows, its use has increased recently. Under a high crude oil price scenario, field applications of enhanced oil recovery (EOR) processes are becoming economic in today's environment. The natural CO2 sources come to be an excellent opportunity because of its low cost. Since 60 years ago, 2500 km2 of carbonate formations containing CO2 were discovered in North of Mexico.
The Quebrache region contains several occurrences of natural CO2 that have been discovered during exploration of oil fields. The CO2 that has been naturally trapped in carbonate formations in this region is present in concentrations that can exceed 90% purity. Due to the high concentrations of CO2, some wells were shut-in 60 years ago, others, have been developed for CO2 production intended for industrial uses and some others as a source of gas lift operations in nearby heavy oil fields.
Recently, a plan of acquisition of information and studies to evaluate the CO2 proven reserves has been designed. In addition, analysis of wells deliverability of these natural CO2 reservoirs, located in the southwestern portion of Tampico, has been carried out. In order to understand better this field, a geological model was built and its dynamic behavior and potential was examined through several well tests. Results of the interpretation of these tests showed excellent results associated with a reservoir of good permeability, high conductivity, large drainage radius, etc. According to the geology of this region and the geochemical signatures observed, the CO2 of Quebrache field has an inorganic origin.
This paper discusses the evaluation of potential supply of CO2 of Quebrache reservoirs for EOR projects in the North of Mexico. The main region studied contains estimated proven reserves of 1.9 Tscf of CO2; however, this volume could be extended to larger amounts associated to areas under study. The CO2 from Quebrache field could be the beginning of a new era of EOR projects in Mexico. A field example of potential EOR application in a mature oil field is shown.
Simplifying the People Factor in the Technology Equation: Change Management That Works
Authors: Berger Tina 
Published: December 2007

Abstract
Today's technical workforce is being asked to adopt new technologies, tools, and processes at an unprecedented rate. These changes are being implemented in order to improve the speed and quality of critical decisions, to address the increasing technical complexity of accessing reserves, and to allow fewer experts to support a greater number projects. Examples include Real-Time Operations technologies, Advanced Collaboration Environments, Directional Drilling Tools, 3D Visualization Technologies, and Real-Time Production Reporting.
This paper provides a summary of the key challenges associated with implementing and sustaining technology adoption within today's bustling energy organizations. The paper also provides an overview of key considerations regarding change leadership, generational differences, and typically-encountered resource issues. Best practices are highlighted and examples are provided.
Using Neural Network System for Casing Collapse Occurrence and Its Depth Prediction in a Middle-Eastern Carbonate Field
Authors: Salehi S. , Hareland G. , Ganji M. , Dehkordi Keivan Khademi , Abdollahi M. 
Published: December 2007

Abstract
A large carbonate oil field in Iran is suffering from severe casing collapses. 48 casing collapses have been found to be reservoir compaction and poro-elastic effects and corrosion.
The application of neural networks for predicting casing collapses using complex multi-dimensional field data has been undertaken. This paper shows how a neural network (ANN) system can be trained based on the parameters affecting casing collapse to estimate the potential of collapse of wells to be drilled as well as the current wells producing in the field. The potential use of this type of analysis is large in that it can be linked as a critical risking parameter in future field development analysis. Being able to quantify the potential for collapse of a well in the future can give management the foundation for a better financial decision making on what wells and where to drill them with the potential for the larger net return on the investment. The estimated collapse and corresponding depth could also benefit in the type of casing design and completion method to be selected as well as workover designs. Interpretation of the neural network results, together with engineering judgment, allowed us to conclude that using this method is technically feasible for predicting casing collapses in this field.
Securing the Future in Mature Gas Fields
Authors: Schinagl Werner , Denny Mark 
Published: December 2007

Abstract
As North Sea gas fields become mature, significant production losses are increasingly caused by liquid loading. The reservoir energy is insufficient to transport liquid particles to surface, liquid falls back and builds up a hydrostatic column in the wellbore that balances out with the reservoir pressure, killing the well and - if nothing is done - leaving significant reserves behind.
This is, in North Sea gas fields, a relatively new problem, and is being addressed by Gas Well Deliquification, which aims to produce the liquids artificially in order to help the gas to flow unobstructed again. The major challenge however, is to find a suitable artificial lifting technology, as most artificial lifting technologies work well with liquid, but cannot handle free gas. A further challenge is to make the existing onshore technologies fit for use in environments that require the use of a SSSV (offshore).
This paper addresses the phenomenon of liquid loading, and presents various technologies that are currently being worked-on to be implemented in North Sea gas fields. Moreover the paper shows the results of the first sets of very promising batch surfactant trials in Southern North Sea fields which were a breakthrough in offshore surfactant application. Moreover it discusses a state-of-the art multiphase pumping method that is being trialled in an onshore oil field, but has significant opportunity for gas well deliquification. Another focus will be on the planned use of "combination methods" that combine the benefits of various artificial lifting technologies in one system, and should be able to produce liquid loaded wells until they are fully depleted.
Applying these deliquification technologies will lead to higher gas production rates in the short-term and extended field lives until wells are fully depleted, in this way securing the future of gas supplies from mature gas assets.
Implicit 1D Transport Solvers for a Streamline Simulator for Fractured Reservoirs
Authors: Andrianov Nikolay , Bratvedt Kyrre , Myasnikov Artyom 
Published: December 2007

Abstract
Naturally fractured reservoirs can be seen as a set of low permeability matrix rock blocks and a high permeability network of fracture channels. This representation is conventionally described by a dual porosity model, which is the one used in the present work. More precisely, the porosities and absolute permeabilities at each point of a reservoir are considered to be those of two interpenetrating continua, the matrix and the fractures one. It is also assumed that the flow occurs in fractures only, i.e., the matrix permeability is equal to zero. Mass transfer between matrix and fractures is modeled by empirically determined transfer functions.
Fracture permeabilities can differ in orders of magnitude, which results in very different flow velocities in different parts of the reservoir. This circumstance is advantageous for simulating the reservoir numerically with the streamline method [1,4,6,7,8,9,11,17,18,21]. Indeed, in the streamline method the transport part is solved along a set of onedimensional streamlines, and the corresponding time step used for the update of the solution can be chosen independently for each streamline. Therefore, there is no global time step restriction, which is the case for finite difference simulation.
This work is a further development of methods, proposed in [19,16] and [2]. We are concerned with the efficient solution of saturation transport along streamlines. To this end, we propose to use an implicit method. This eliminates the CFL restriction on the time step which is inherent to explicit methods, at the price of possibly introducing more numerical diffusion. The numerical method can be further accelerated with the use of adaptive mesh refinement along streamlines [2]. We show that the proposed technique can be useful when one needs to estimate the flow pattern in the reservoir quickly, e.g., for ranking of geological models.