bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Freeze Plug Process Proves a Viable Barrier Technique in Sajaa Field, Sharjah, United Arab Emirates
Authors: Powers Brian S. , Pruitt Randal D. , Tuppen James 
Published: December 2007

Abstract
A Dynamic Freeze Plug Process (DFPP, U.S Patent 5,649,594 Flak, L.H) was applied to several packerless Sajaa Field wells to achieve a second mechanical annular pressure barrier prior to removing the trees for hydraulic, live well work over operations. Four wells were successfully frozen with minimal fluid lost to the formation. Several equipment and procedural modifications made after the first job improved subsequent jobs and reduced the time required to complete the freeze and achieve barrier. The DFPP is a proven technique to achieve an annulus barrier in a gas filled environment.
BP's Drilling and Well Operations Policy requires two independent pressure barriers before any pressure envelope is broken for well interventions. The barriers must be capable of operating independently and simultaneously and must be pressure tested from the direction of flow. Dual tubing barriers are easily achievable with tubing plugs, tubing hanger backpressure valves, or a combination of the tow. The packerless wells in Sajaa Field only have one permanent annular barrier, the metal-to-metal tubing hanger seal, and during normal well operations the annulus is pressured at the surface. Thus, achieving additional annular barriers is more challenging, Sajaa well completions consist of tubing strings landed above the perforations or horizontal lateral zones, or tubing strings set in permanent packers to separate multi-lateral zones (Figures 1a. and 1b.)
Using Artificial Neural Networks to Develop New PVT Correlations for Saudi Crude Oils
Authors: Al-Marhoun M. A. , Osman E. A. 
Published: December 2007

Abstract
Reservoir fluid properties data are very important in reservoir engineering computations such as material balance calculations, well testing, reserve estimates, and numerical reservoir simulations. Ideally, those data should be obtained experimentally. On some occasions, these data are not either available or reliable; then, empirically derived correlations are used to predict PVT properties. However, the success of such correlations in prediction depends mainly on the range of data at which they were originally developed. These correlations were developed using linear, non-linear, multiple regression or graphical techniques.
Recently, researchers utilized artificial neural networks (ANN) to develop more accurate PVT correlations. ANNs are biologically inspired non-algorithmic, non-digital, massively parallel distributive and adaptive information processing systems. They resemble the brain in acquiring knowledge through learning process, and storing knowledge in inter-neuron connection strengths.
The present study presents new models developed to predict the bubble point pressure and, the formation volume factor at the bubble point pressure. The models were developed using 283 data sets collected from Saudi reservoirs. These data were divided into three groups: the first was used to train the ANN models, the second was used to cross-validate the relationships established during the training process and, the last was used to test the models to evaluate their accuracy and trend stability. Trend tests were performed to ensure that the developed model would follow the physical laws. Results show that the developed models outperform the published correlations in terms of absolute average percent relative error, and standard deviation.
Cement: How Tough is Tough Enough? A Laboratory and Field Study
Authors: Mack David J. , Dillenbeck Robert L. 
Published: December 2007

Abstract
Casing is cemented into the wellbore to provide zonal isolation of producing zones, protect fresh water zones from contamination, prevent casing collapse caused by moving salts or sloughing clays and isolate the casing from corrosive brines. In other words, casing is cemented to create annular isolation. Historically, the major physical property of the cement used to determine whether these results would be attained for the life of the well, was the unconfined compressive strength of the set cement.
Recent studies have shown that there are other "strengths or mechanical properties" that are even more important to consider. These strengths include tensile and flexural.
This paper discusses why tensile and flexural strengths must be considered in slurry design, alonf with the interrelationship of compressive, tensile and flexural stresses that occur in wells, and provides Appalachian Basin field examples, where reduced, unconfined compressive strength cement, with enhanced tensile and flexural strengths has been successfully used.
Selection and Evaluation EOR Method Using Artificial Intelligence
Authors: El-M Shokir E. M. , Goda H. M. , Sayyouh M. H. , Fattah Kh. A. 
Published: December 2007

Abstract
Recently, the theory of Artificial Neural Network has found a worldwide approval from those who are concerned with the research in the field of petroleum and natural gas engineering. This may be due to the neural network potentialities in solving problems to which the network is designed, depending on the gained experiences of some similar problems joined with their solutions. This theory has been found to give high possibilities with amazing results as applied and tested in petroleum engineering.
A model composed of two neural networks was designed to work in series in order to perform the task of EOR project selection through the first network (Technical network), and then evaluate the selected project economically using the second network (Economics network). As the model, with the two networks, performs its task successfully, it is then tested with data seeded with certain level of error affecting the parameters given to the model in the test features in order to determine the power of the model and its ability to overcome what we call noisy data.
Study on EOR Mechanisms by Microbial Flooding
Authors: Feng Qing-xian , Zhou Jia-xi , Chen Zhi-yu , Wang Xiao-lin , Ni Fang-tian , Yang Huai-jun 
Published: December 2007

Abstract
We have carried out flooding test with cores, sandpack, pore level model by microbe NG80, special metabolic products (G01, G02, G03) under reservoir temperature. The results are:
Microbes migrated through core pore and fermented in it; microbial concentration has an increasing trend, part of cells were absorbed on sand surface. Oil recovery that flooded by bacteria with concentration 10% is over 6% higher than in water. The highest recovery is 13.8%, flooded at best flooding mode, NG80 products and its constitute; The earlier the time of injecting fermented broth, the better the result obtained; Metabolites bear effect of denudation on oil films; and metabolisms result in alteration of wettability, in witch a special biochemical process and "in situ growth" effects characterized by bacteria take place; Mechanisms observed in the pore level model during microbial flooding are: starting residual oil re-flowing by emulsification-carrying, changing the wettability, denuding oil films and producing "Jamin Effect" in the pores while flooding.
We performed microbial flooding program in G69 block, which has 5 injections wells and 7 drainage points. Mixed original, NG80, 80 and DG2, fermented broth 720m3 was injected in with three slugs during March to July,2001. Monitored preliminary results show that the decline trend of the block oil production was controlled and some wells' production began to increase. That the mechanism of microbial flooding in the oilfield improves poducibility.
Combined Global and Local Optimization Techniques Applied to History Matching
Authors: Schulze-Riegert R. W. , Haase O. , Nekrassov A. 
Published: December 2007

Abstract
Evolutionary Algorithms and local optimization methods are applied to the problem of history matching in reservoir engineering. Application of global optimization methods to history matching of complex reservoir models is generally limited by the convergence behavior. In this paper concepts for an integrated workflow of different optimization methods, parallel computing and statistical analyses are developed.
Global optimization methods and a Bayesian approach to identify best results are combined to improve the convergence behavior. Result data generated in the course of an optimization cycle are used for analyzing sensitivities, correlations and trends of model parameters in a global search space. Statistics are used to reduce the search space by combining correlated model parameters, to exclude less important parameters and to identify regions by correlating well parameters. These techniques are applicable, irrespectively of the quality of a converging objective value.
Results are presented for different complex real three phase reservoir models. The potential and area of applicability is discussed.
In conclusion, results suggest that presented techniques are well prepared to extend the manual process of history matching. The introduction of a workflow based on parallel computing combined with global optimization methods effectively allows to investigate the solution space. Identification of different parameter sets which equally match history data represent an existing model diversity and prepares a basis for uncertainty estimations of production forecasts.
Experiences With Automated History Matching
Authors: Kabir C. S. , Chien M. C. H. , Landa J. L. 
Published: December 2007

AbstractMatching historical performance of a reservoir is a time-consuming exercise with uncertain outcome. The current practice of manual matching is subjective and goodness of the match owes largely to the experiences of the team members involved in a study and to the quality and quantity of various input and observed data.This paper describes approaches taken to speed up the history matching effort during the course of replicating multiyear performance of two West African reservoirs. The study entails validation of production data, and matching of single-well and full-field performances with two automated-history-matching (AHM) approaches based on the Gauss-Newton algorithm. These finite-difference results obtained with AHM are contrasted with those obtained from the traditional manual approach.Results show that both AHM approaches shorten length of a study, and preserve objectivity of a history match. The use of grid coarsening results in impressive speed gain that can quickly provide clues whether adjustments of certain parameters are justified for some wells. That multiple parameter adjustments can be made within specified bounds with a few iterations in a 24-hour run is a profound improvement in our speed of learning of key reservoir flow behavior. This speed, in turn, guides the study in a path that leads to rapid conclusion in a fraction of time taken in a traditional study.
Quantifying Production Strategy Impact in Risk Analysis of an E&P Project Using Reservoir Simulation
Authors: dos Santos J. A. M. , Schiozer D. J. 
Published: December 2007

Abstract
Recent computer developments allow the quantification of geological and physical uncertainties in the appraisal phase of a reservoir using numerical flow simulation. However, such a process is normally performed with a fixed production strategy because a variable strategy is very time consuming. The objective of this work is to study the impact of the production strategy in the risk analysis process. That risk analysis methodology comprises: definition of the uncertain attributes, construction of a base simulation model, selection of the most critical attributes using sensitivity analysis, simulation of all possible models, risk calculation using the Net Present Value (NPV) as the objective function, and choice of a few simulation models that represent the geological uncertainty. An optimization procedure is applied to both base and representative models. Finally, the changes in the objective function are measured and some conclusions and recommendations are made. In this work, two examples are analyzed. In the first case, the study is applied to a real offshore field in Brazil. In the second one, it is considered a very heterogeneous reservoir with greater uncertainty in the structural model and in the hydraulic connectivity between reservoir blocks. Both cases are solution gas drive reservoirs with water injection. In the cases studied, the variation in the NPV due to optimization procedure was small when compared with the uncertainty in the geological model, and changes in the optimized production strategy and investments are not significant, leading to the conclusion that, in such cases, the optimization procedure can be applied only to the base model. The use of a unique production strategy in the whole process can reduce significantly the computational effort. It is also shown that a more accurate result can be obtained by optimizing only selected models called here representative models.
New Developments in Multiblock Reservoir Simulation: Black Oil Modeling, Nonmatching Subdomains and Near-Well Upscaling
Authors: Lee S. H. , Wolfsteiner C. , Durlofsky L. J. , Jenny P. , Tchelepi H. A. 
Published: December 2007

Abstract
In multiblock reservoir simulation techniques, the reservoir model is divided into a number of subdomains or blocks. In our current implementation, these blocks are locally structured but globally unstructured. This representation enables the modeling of geometrically complex reservoir features such as fault surfaces and nonconventional wells while avoiding many of the complications of fully unstructured formulations. In this paper, we present several important developments within this frame-work. These include the extension of a previous two phase flow finite volume formulation to the general black oil case, the implementation of techniques for treating systems in which grid lines do not match between adjacent subdomains, and the application of a near-well radial upscaling technique to the multi-block paradigm. Simulation results illustrating the accuracy and efficiency of these new capabilities are presented. These include a black oil simulation for a local well study, flow through a realistic reservoir with several wells and faults, flow through a fault surface represented by nonmatching grid lines, and a two phase flow simulation demonstrating the applicability of the near-well upscaling procedure to multiblock models. With the new developments presented in this paper, the finite volume based multiblock simulator can be applied to a variety of problems of practical interest.
Use of PEBI Grids for Complex Advanced Process Simulators
Authors: Skoreyko Fraser , Sammon Peter H. , Melichar Herbert 
Published: December 2007

Abstract
PEBI ("perpendicular bisector") grids have been shown in the past to have the potential to reduce computational times for the simulation of relatively straight-forward processes. It is the purpose of this paper to investigate PEBI-based gridding for a much more complex thermal process in a full field setting using commercial simulation products. The goals are to study both computing efficiency and accuracy by comparing results obtained by modelling a field using the more conventional corner point-based gridding with local grid refinement to those obtained using a PEBI gridding approach.
The field in question has been produced for about 20 years, with an operational history that includes cyclic steam stimulation in portions of the field. Many vertical faults have been mapped in the reservoir, and over 140 wells, many of them deviated or horizontal, have been drilled. A simulation study had been done using approximately 170 000 active corner point cells. It was found that the inclusion of foamy oil behaviour was necessary to get a good match of the production history. It appeared though that this simulation was lacking in accuracy near horizontal wells. This was probably due to the inability of the model to align its locally refined grids properly with many of the wells, and the difficulty in getting reasonable refinement levels where cyclic steam stimulation was being carried out, without making the problem considerably larger.
A second simulation study was carried out using a PEBI-based grid. The more flexible aspects of this gridding system allowed construction of a better aligned grid, especially near the horizontal wells and near faults. Moreover, the characteristics of the PEBI-based grid also allowed efficient grading of grid cell sizes, so that particularly fine-scale gridding could be used near wells, while still maintaining an overall model size that was about half that of the corner point model. All processes modelled in the original simulation were replicated in the PEBI-gridded model, including the foamy oil and thermal aspects.
The PEBI gridded model ran in about a third of the time of the original corner point model, and showed accuracy improvements which were attributable to the better placement of grid cells. These results showed that the simulator's ILU-based sparse matrix solver technology was very capable of computing in an unstructured grid environment, even while using cells near wells that were smaller than those used in the corner point model.
Thus, PEBI-based gridding can be used to efficiently model complex processes in a full field setting. These grids can demonstrably improve accuracy and are much more adaptable for modelling near wells and in a complex geological setting. A three-fold run time improvement was noted for the field in question when comparing to a more conventional, corner point gridded model.
High Order Upwind Schemes for Two-Phase, Multicomponent Flow
Authors: Mallison B. , Gerritsen M. , Jessen K. , Orr F. M. 
Published: December 2007

Abstract
In this paper, we investigate high order finite difference schemes for compositional simulation. Results presented for one-dimensional (1D) gas injection problems suggest that a third order essentially non-oscillatory scheme is more accurate and efficient than first order methods and is more robust than traditional total variation diminishing schemes. We investigate also the use of adaptive mesh refinement (AMR) to further improve the efficiency of high order schemes. Preliminary results indicate that the savings in computation time with AMR can be significant for compositional problems. Our 1D results can be extended to three dimensions through conventional finite difference approaches but we plan to apply them in a compositional streamline simulator.
Coupled Simulation of Reservoir Flow, Geomechanics, and Formation Plugging With Application to High-Rate Produced Water Reinjection
Authors: Bachman R. C. , Harding T. G. , Settari A. Tony , Walters D. A. 
Published: December 2007

Abstract
Produced water re-injection at high rates presents a coupled problem of reservoir flow, formation damage, stress alteration around the injector, and fracture propagation. Accurate prediction of permeability changes, fracture propagation pressure, and fracture dimensions is required for minimization of disposal costs and design of surface equipment. The paper presents the formulation and numerical implementation of a coupled reservoir, damage and geomechanical model which includes the above couplings. Details of the model are first described. A simple empirical damage model, calibrated to field data is then presented. Finally, application of the complete model to high rate reinjection in the Masila Block in Yemen is presented. The model predictions show that it is feasible to sustain over 100,000 BWPD in a single Masila disposal well by injecting above fracture pressure.
Coupled Geomechanical and Reservoir Modeling on Parallel Computers
Authors: Gai Xiuli , Dean Rick H. , Wheeler Mary F. , Liu Ruijie 
Published: December 2007

Abstract
In coupled geomechanics and reservoir modeling, the finite element discretization of the force balance equation leads to very large linear systems, whose solution is both time and memory consuming. ICCG (Incomplete Cholesky Factorized Conjugate Gradient) is a popular technique for solving for displacements, but the technique is limited to about 60,000 nodal points on desktop machines. Most large 3D field scale problems will have to be run on parallel machines. In this paper, we present a reduced-communication, super coarsening multigrid method that can be combined with other domain decomposition-based preconditioner to achieve faster convergence with high parallel scalability. A preliminary test case of 1.5 million grid blocks with up to 59 processors shows a parallel efficiency of above 90%.
Uncertainty Quantification to Evaluate the Value of Information in a Deepwater Reservoir
Authors: Portella R. C. M. , Salomão M. C. , Blauth M. , Duarte R. L. B. 
Published: December 2007

Abstract
In petroleum industry, the development of oil resources is performed under strong uncertainty conditions, not only related to the geological and reservoir characterization, but also concerning the economic parameters. Depending on the number of appraisal wells drilled at the time of the decision, we may choose to start the execution of the development plan, or to pay for more information. This includes the realization of a new seismic acquisition, the drilling of a new well, or the execution of pressure tests.
In the present work, we applied a value of information analysis, under uncertainties conditions, to optimize the exploitation of a new block in a deep water field, located in Campos Basin, Brazil. The reservoir rock consists on high permeability sandstone, with good lateral continuity, without internal sealing faults. The most important properties that impact the volumetric uncertainty are the net to gross relation, and the position of the oil-water contact. Equally, the dynamic parameter that strongest affect the recovery factor are the absolute permeability and the well productivity. In order to simultaneously study the geometric and dynamic uncertainties and minimize the number of simulation runs, we performed an experimental design process
The calculated economic value of the information from the new well, which results essentially from the optimization of the exploitation project, was much higher than its cost, recommending for its application. In contrast, the anticipated production did not show to be advantageous, and was discarded. Based on these results, the new well was drilled, and the reduction of the volumetric uncertainty permitted to implement a sharper design to the exploitation project.