bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integration of Uncertainty Analysis and History Matching: Application in a Complex Case
Authors: Silva Luciana dos , Schiozer Denis 
Published: April 2012

Abstract
The large amount of uncertainties on reservoir modeling increases petroleum production forecast risks. Therefore, the history matching, which refines the simulation model to closely reproduce production data, is a vital procedure once it approximates numerical models to reality providing reliable predictions. As history matching is an inverse problem, the use of multiple models with good match is important to guarantee future analysis.
Many methodologies were developed to integrate uncertainty analysis and history matching, in order to mitigate the reservoir uncertainties by using the observed data. In this context, the present article aims to evaluate the application of existing methods on a synthetic complex model (i.e. similar to a real field) and propose new methods with some improvements to be applied in real cases of the petroleum industry.
The main characteristic of these methods is the use of differences between observed and simulated data to recalculate the probabilities distribution of uncertain parameters with the purpose of reducing reservoir uncertainties. The redistribution of occurrence probabilities is made with different formulas, representing the distinct four methods discussed: the first two are reviewed from literature and other two proposed by authors. The first proposed method combines the best practices of the two reviewed ones, making it robust to be used in real cases with a great number of wells and production functions to be adjusted such as water production and pressure. The second proposed method is only an iterative application of the first one with a redefinition of attribute values in order to refine the results.
A comparison of the results of the four methods shows an evolution in the uncertainty reduction. Besides that, there is a decrease in the dispersion of the representative curves, which are centralized around the history data. Finally, this work presents a simple and practical way of integrating uncertainty analysis with history matching that provides reliable reservoir simulation models for production forecast and risk analysis of future projects.
Interference Tests Analysis in Fractured Formations with a Time-Fractional Equation
Authors: de Swaan-Oliva A. , Camacho-Velázquez R. , Vásquez-Cruz M. 
Published: April 2012

Abstract
Fluid flow analytical models traditionally used in well test analysis not always yield adequate results for reservoir characterization. Contrastingly, fractal formulations have proved to be a more suitable tool. Among the various formulations, the Metzler-Glockle-Nonnemacher (MGN) equation includes a fractional time derivative. In this paper, that equation was applied to analyze interference tests in actual field cases. The MGN equation was applied and automatically matched to the observed pressures. Both usual reservoir properties -porosity and permeability- and also fractal exponents were varied in the matching procedure.
Automatic matches of the involved variables resulted in pressure increments that compare fairly well with observed data from the field tests. The responses show a high anisotropy in the rock properties.
The MGN equation implemented in this paper comprises fractal behavior in spatial variables as well as in the time term.
Thus, well tests recorded in highly heterogeneous media, not amenable to standard techniques, can be analyzed with such analytical fractal approach.
Dilatancy Criterion Applied for Borehole Stability During Drilling Salt Formations
Authors: Rios A. , Roegiers J. 
Published: April 2012

Abstract
Despite the fact that drilling activity through salt formations became an important issue for the oil industry since 1901, with the discovery of the Spindletop Field in Texas, wellbore stability in the neighborhood of rock salt has been seldom by analyzed. Considering that pore pressure is not present in salt formations because the low porosity they have, and that the fracture gradient is considered greater than the overburden; constraints for a safe mud weight is difficult to determine. Therefore, the mud weight program for salt section is mostly determined using the isothermal curves given by Leyendecker et al. (1975) or following rules-of-thumb. Currently, the approaches to study wellbore stability issues through salt formations are based on creep behavior, which is function of the activation energy. These models were elaborated under certain pressure and temperature conditions, so their reliability is not universal. Hunsche & Cristescu (1998) analyzed the deformations mechanisms due mostly for the volumetric behavior of rocks. They determined a compressibility/dilatancy boundary for rock salt which is function of the state of stresses that prevails. In 2007 Henglin et al. presented the hypothesis that a borehole would be stable only if the magnitude of the octahedral shear stress is below the dilatancy boundary given by Hunsche & Cristescu. This paper tries to explain the wellbore instability in rock salt based on Henglin et al. hypothesis. A new stability criterion is proposed and applied to field data from Yaxche and Sen Oil Fields to planning the appropriate mud weight for salt sections. Yaxche field is classified as high pressure-high temperature conditions, is offshore in the Gulf of Mexico; whereas Sen field is an onshore field, under low-pressure-high temperature conditions.
Integrated Risk Analysis of Uncertainties in Geological Model and Dynamic Flow Properties for the Development of Oil Fields
Authors: da Silva Genilson A. , de Oliveira Guimarães André M. , da Silva Gislene A. , Lucas Marcos Aurélio 
Published: April 2012

Abstract
Given the high degree of uncertainty in the oil industry present production development projects, the use of probabilistic models is of considerable interest as a means to support decision making. Besides that, there is a constant pursuit to optimize oil drainage, to maximize reserves as well as the financial outcome of the project. A robust study, characterizing the uncertainty of the various critical parameters, such as number of wells, maximum water injection rates, relative permeabilities and rock and PVT data, is of paramount importance to assure that the impact of all uncertain parameters have been accounted for.
The present risk curve construction methodology takes into consideration uncertainties in the geological model and in the dynamic properties in an integrated manner. Six geologic scenarios with distinct permo-porous distributions were generated. A study was conducted to obtain PVT correlations of the produced fluids.
A sensitivity analysis was performed to eliminate non-significant parameters. The relevant ones were well adjusted to the production data in all geologic scenarios. Optimum exploitation configurations were obtained for each model, using the net present value (NPV) as an objective function. Each configuration was applied to all scenarios and the estimated monetary values (EMV) of each configuration were calculated. The maximum EMV was used as optimum criteria. The final product obtained was a development strategy risk curve, showing the viability of the proposed methodology.
Results of the Implementation of the Project Management System: Towards a Competitive Quality Model
Authors: García L. F. , Naranjo J. G. , Salazar J. S. , Linero L. M. 
Published: April 2012

Abstract
Investment projects are the primary vehicle for companies to achieve their goals, maximize the value of its shares by generating value. It is therefore important that the resources allocated to projects are used efficiently and that the promise of value of each project is met according to plan.
In response to this need, it was proposed to implement a project management system in the Vice-presidency of Exploration, Ref 1, based on international standards, industry best practices and definition of deliverables to achieve a continuous improvement process designed to develop more efficient exploration projects.
Implementation of the proposed management system for exploration activities has shown strong benefits, as evidenced in the systematic measurements of the FEL index over the past 5 years.
This paper presents an account of the FEL measurements of exploratory wells from 2006 to 2010 and its corresponding analysis considering the sustainability of the model's application in time, the benefits in terms of time, costs and characterization that determines the FEL index measurement.
Because of the confidentiality of information, for purposes of this article the names of projects were omitted were omitted and the figures are presented as monetary and time units.
Estimation of Geological Facies Boundaries Using Categorical Indicators with P-Field Simulation and Ensemble Kalman Filter (EnKF)
Authors: Nejadi S. , Trivedi J. J. , Leung J. 
Published: April 2012

Abstract
The Ensemble Kalman Filter (EnKF) is a Monte-Carlo based technique for assisted history matching and real time updating of reservoir models. However, it often fails to detect facies boundaries and proportions as the facies distributions are non-Gaussian, while prior knowledge of the data is usually insufficient.
It is common to represent distinct facies with categorical indicators, which are intrinsically non-Gaussian. We implemented discrete cosine transform (DCT) to parameterize the facies indicators. This methodology was promising for simple and two facies models. For more complex models, though observed data were matched, it failed to reproduce realistic facies distribution corresponding to the prior variogram and facies proportion.
In this paper a new step is proposed to be included in the history matching of complex reservoirs using EnKF: realizations exhibiting the largest mismatch in terms of production data, experimental variogram, and histogram are discarded after the first few update steps, and a probability map for facies modeling is derived using the remaining ensemble members. Probability field (P-Field) simulation is performed subsequently using the facies probability map to generate a new set of realizations replacing the discarded members. The new realizations are updated again from the beginning using EnKF.
Several case studies with different facies distribution and well configurations were conducted. Initial ensembles were created using known facies classification at the well locations and populating binary facies data throughout reservoir using numerous variogram models and prior facies proportions. The regenerated realizations are closer to the true reservoir state since they already take into account the first few set of production data.
The qualities of the history-matched models were assessed by comparing the experimental variograms of facies distribution and facies propositions of the final ensemble, as well as the Root Mean Square Error (RMSE) of the predicted data mismatch.
Combination of DCT-EnKF and regenerating new realizations using P-Field simulation demonstrates reasonable improvement and reduction of uncertainty in facies detection. Incorporating the new step in the procedure assists filter to preserve the reference distribution and experimental variogram for complex reservoirs.
Inclusion of Environment Assessment in the Decision-Making Process of Petroleum Fields Projects
Authors: Barreto C. E. , Schiozer D. J. 
Published: April 2012

Abstract
In the last decades, environmental issues have been discussed more carefully. Consumers and government have required that companies become cleaner and make operations environmentally safer. Discharge of produced water from petroleum reservoirs may have a significant impact on environment and it is expected that this operation will be more taxed and the costs of treatment will be increased, besides the influence of consumer's preference. Considering that the relevance of the water discharge may impact on the field operation, it is important to study if the cost of discharge may change the choice of the production strategy. This work proposes a methodology to assess the environmental impact of water discharge and to consider this factor at the economic evaluation, including environmental analysis in the decision-making process. The methodology combines reservoir simulation, contaminants dispersion simulation and economic evaluation in order to make feasible the proposed assessment. The main idea is to make an economic valuation of an environment assessment and to add it in the project net present value (NPV). The maximum benefit is to implement a strategy with the concept of "zero discharge". This methodology was applied in a study case considering a reservoir simulation model in which different strategies are evaluated taking discharge of water evaluation into account. Different economic scenarios are evaluated. The results show that considering an environmental factor in the cash flow analysis can change the choice of the production strategy. The strategies producing less water obtained best results when compared with strategies which produced more water. This study points out that environmental analysis can be included in a global strategy selection process. Moreover, it is concluded that considering environmental impact on economic evaluation can really change the choice of production strategy.
Development of a Static/Dynamic Model for Chac Field Based on a Novel Multidisciplinary Workflow
Authors: Galindo R. Ortega , Galindo-Nava A. , Pérez-Alvis E. , Ortuno E. , Morales C. A. 
Published: April 2012

Abstract
The development of advanced computational systems has increased not only the capability but also the demand of complex simulation models in the oil industry. Unfortunately, due to the complexity of naturally fractured reservoirs in the Gulf of Mexico, PEMEXs North-East Marine Region has faced many difficulties in producing these models for its new and mature fields.
A practical workflow to generate static-dynamic simulation models for naturally fractured reservoirs is presented, with a strong emphasis on multi-disciplinary integration and interaction. A constant feedback between the various disciplines is crucial for a successful project.
The methodology was applied to develop the static-dynamic model for Chac field, located off the coast of Campeche. The simulation model was constructed with 100% active cells. The dimensions of the grid were optimized to maximize efficiency without losing vertical geological definition.
The model is able to reproduce the historical pressure-production behavior of the field, as well as the behavior of individual wells. Using coning and channeling correlations for fractured reservoirs; uncertain oil production data of some wells were revised to reproduce observed water productions.
The results of this work show how a multidisciplinary approach, during the construction of static and simulation models, creates a synergic environment that strengthens available tools. Additionally, this approach encourages the creation of larger pools of information from different sources and specialties, which can be used to explain reservoir phenomena observed during history matching.
This novel methodology, based on an integrated workflow, will allow the optimized construction and history match of numerical models developed for the RMNE. The interaction between various disciplines will provide a better understanding of reservoir phenomena, which in turn, will provide better tools during the decisions making process.
Understanding the Impact of Channel Fracturing in the Eagle Ford Shale through Reservoir Simulation
Authors: Altman R. , Viswanathan A. , Xu J. , Ussoltsev D. , Indriati S. , Grant D. , Peña A. , Loayza M. , Kirkham B. 
Published: April 2012

Abstract
Oil and gas production from unconventional reservoirs has witnessed significant growth in the last few years. Historically, massive stimulation treatments have been used to produce these hydrocarbons. While the in-place hydrocarbon volumes are often large, the challenge is to increase recovery while using fewer resources. One of the technologies that have been used to address this challenge is the channel fracturing technique. A number of horizontal wells have been stimulated in the Hawkville field of the Eagle Ford shale with this technique. The objective of this work was to evaluate the impact of the channel fracturing technique in these wells by using numerical reservoir simulation.
Numerical simulations were performed on a total of 15 horizontal wells. Six wells were completed with channel fracturing and nine wells were completed with slickwater or hybrid fracturing treatments. Because the Hawkville field has large variations in fluid composition, wells producing in the condensate-rich section were studied separately from those in the dry gas section. A consistent history matching methodology and workflow was applied across all wells which enabled a direct comparison of results.
Results from analytical work, such as normalized production comparisons, were used to narrow down the range of uncertainties and assumptions made in the numerical simulations. A trend emerged from the analytical evaluations, showing that wells completed with the channel fracturing technique have higher productivity while using significantly less proppant and fracturing fluid. Numerical simulations confirmed the finding and provided insights on the cause of higher production on these wells. Unlike analytical methods, numerical simulation can model changes in complex fracture properties between wells, the effects of transient flow, shale gas desorption from kerogen, interference effects between perforation clusters, and accounts for differences in shale reservoir quality between wells. Furthermore, calibrated well models allowed for sensitivity studies such as evaluating the impact of changes in fracture geometry and conductivity on future wells.
Reservoir modeling provided an estimation of effective stimulated fracture volume and fracture conductivity. Wells treated with the channel fracturing technique were observed to have on average 50% greater effective stimulated volume and more than double the stimulated conductivity compared to wells fractured with slickwater. When compared to wells fractured with hybrid treatments, channel fracturing wells had on average 27% greater effective stimulated volume and 50% more stimulated conductivity.
Design of a Neural Network Model for Predicting Well Performance after Water Shutoff Treatments Using Polymer Gels
Authors: Ferreira I. , Gammiero A. , Llamedo M. 
Published: April 2012

Abstract
Current selection of candidate wells for water shutoff by polymer gel technology is based on empirical criteria which make uncertain its result. Although sophisticated models to resemble the injection of polymer gels in a porous media are available, they require extensive knowledge of the well and reservoir, plus specific yet to be characterized gel kinetics parameters. In this work a model is proposed to predict a well future production response based on well and reservoir information that is commonly available.
Neural network models were designed, trained and validated for predicting wells production performance after a polymer gel treatment for water shutoff. A total sample of 31 historical applications of gel treatments were used for training and validating the proposed networks. Historical applications gathered include different well and reservoir types, which make the model prediction validity wide broad.
Neural networks with two different tasks were developed during this study, one of them with a bi-valuated response (output), and qualified as classification networks and the others with a wider range of potential output, identified as regression networks. The model aims to predict a well future oil production and the percentage of water associated to that production after the execution of a gel treatment. Training of the neural network was carried out using 90% of the wells set gathered and 10% of the wells were used for validation. An average relative error of 20% was obtained when comparing the actual production performance of wells and the neural network prediction for oil rate and water content.
The proposed neural networks allow the selection of future candidate wells for gel treatments, based on its potential success. Additionally, the proposed network allows improving future gel treatments by evaluating the effect of the volume of gel to be injected on the treatment's result.
A Simulation Study of Chemically Enhanced Water Alternating Gas CWAG Injection
Authors: Majidaie S. , Khanifar A. , Onur M. , Tan Isa M. 
Published: April 2012

Abstract
Water alternating gas (WAG) injection has been a popular method for commercial gas injection projects worldwide. The injection of water and gas alternatively offers better mobility control of gas and hence, improves the volumetric sweep efficiency. Although the WAG process is conceptually sound, its field incremental recovery is disappointing as it rarely exceeds 5 to 10 % OOIP. Apart from operational problems, the WAG mechanism suffers from inherent challenges such as water blocking, gravity segregation, mobility control in high viscosity oil, decreased oil relative permeability, and decreased gas injectivity.
This paper addresses the aforementioned problems and proposes a new combination method, named as the chemically enhanced water alternating gas (CWAG), to improve the efficiency of WAG process. The unique feature of this new method is that it uses alkaline, surfactant, and polymer as a chemical slug which will be injected during WAG process to reduce the interfacial tension (IFT) and improve the mobility ratio. In a CWAG process, a chemical slug is chased by water, preceded by gas slug and followed by alternate CO2 and water slug or chemical slug injects after one cycle of gas and water slug. Essentially CWAG involves a combination of chemical flooding and immiscible carbon dioxide (CO2) injections. These mechanisms are IFT reduction, reducing water blocking effect, mobility control, oil viscosity reduction due to the CO2 dissolution and oil swelling.
CMG's STARS was used to study the performance of the new method using some of the data found in the literature. It is a chemical flood simulator that can simulate all aspects of chemical flooding, and it can also handle immiscible CO2 injection features by considering K-value partitioning. The sensitivity analysis shows that the new method gives a better recovery when compared to conventional WAG. This study shows the potential of CWAG to enhance oil recovery.