bluuebunny/crossref_metadata_2025_split huggingface dataset:
Well Pressure Behavior for a Vertical Well in a Gas Condensate Naturally-Fractured Reservoir
Authors: Escobar Freddy Humberto , Garcia-Rocha Humberto , Suaza Ivan Mauricio , Cantillo Jose Humberto 
Published: December 2007

Abstract
The complex behavior exhibited by gas condensate reservoirs due to the existence of a two-phase system: reservoir gas and liquid condensate and its implications plus the nature of heterogeneities is the subject of the present article which involves handling of reservoir engineering concepts subject to be interpreted, so that by coupling them with pressure transient analysis using a compositional simulator, we can obtain some patterns which lead to facilitate the understanding of the reservoir's dynamics.
Great volumes of fluids are stored in Naturally Fractured Reservoirs (NFR). Simulation of this type of deposits presents great challenges, from not only the geomechanical point of view but also the thermodynamical modeling of the different phases flowing throughout the fracture system.
In this work, we present an attempt to model a gas condensate formation involving the implications of relative permeabilities to observe their effect on the flow behavior once pressure finally falls below the dewpoint and the effect of the capillary number on the fluid flow phenomena in the near-wellbore region. Interpretation of the pressure test is conducted by the TDS technique.
The Impact of Undersaturation on Coal Gas Economics
Authors: Seidle John P. , O'Connor Leslie S. 
Published: December 2007

Abstract
Many coal deposits throughout the world are undersaturated to some degree. With actual gas contents less than expected from reservoir pressure and the sorption isotherm, these coals require dewatering before gas desorbs. An operator must bear water production and disposal costs, frequently for an extended period of time, prior to realizing any revenue from gas sales. Gas and water profiles for wells completed in Powder River and Greater Green River coals were simulated assuming saturated coals and selected degrees of undersaturation. Base case economics were constructed by combining the simulated gas and water profiles from saturated coals with typical capital costs and well operating expenses for each basin. Gas and water profiles from simulation of ever deeper undersaturation were used to drive additional economic analyses. From this suite of economic analyses, the impact of undersaturation on economic parameters such as net present value, time to payout, and breakeven gas price was assessed.
Improving Reserves and Production Using a CO2 Fluid Model in El Trapial Field, Argentina
Authors: Crotti M. A. , Inlab S. A. , Fernandez Gustavo , Terrado Martin 
Published: December 2007

Abstract
The El Trapial field is a 1.2 B bbl OOIP asset located onshore in Argentina, South America. The field was discovered in 1991. Water injection started in 1993 with current infill drilling and development of some areas still taking place. This field consists of several sandstone reservoirs with average permeability and porosity of 75 mD and 17% respectively. One unique challenge of El Trapial field is that the light oil coexist with gas that contains high CO2 concentrations, greater than 75%. This is observed in both dissolved gas and in gas caps in various blocks of the field. Well documented production data have indicated variations in CO2 concentration in different areas of the field. Conventional fluid modeling could not explain the formation of gas caps at dissimilar structural positions, nor could it explain the existence of oil legs at pressures below the apparent (predicted) bubble point pressure.
A fluid characterization model was performed in the El Trapial field in order to improve the understanding of the PVT behavior at reservoir conditions in the presence of the original high content of CO2. An empirical model was created using the assumption that thermodynamic equilibrium was reached before the time of exploitation. This model shows that the bubble point pressure can increase with depth when light oil coexists with high concentrations of CO2, showing an opposite behavior to what is observed when the gas phase is mostly hydrocarbons. Sensitivity analysis was conducted to identify the key variables that impact this distinctive behavior.
The developed model improved the understanding of the areal and vertical distribution of CO2 in El Trapial. It was used to redesign the development strategy of an area of the field, taking advantage of the oil production at shallow structural depths previously identified as potential free gas zones. Also, the production strategy of the entire field in terms of surface CO2 handling, corrosion prevention and production optimization was revised. This paper illustrates the characterization of this unique behavior, including modeling, application and results.
This proposed model can be applied to other reservoirs where CO2 is present. A methodical approach is presented including laboratory tests, field surveillance and monitoring needs as well as resulting development improvements.
Design and Utilization of Low Solids OBM for Aasgard Reservoir Drilling and Completion
Authors: Fossum P. V. , Van Der Zwaag C. , Taugbøl K. , Mjaaland S. , Sletfjerding E. , Høgstøl H. , Olsen P. A. , Pettersen B. 
Published: December 2007

AbstractThis paper describes the development of a low-solids mineral oil-based fluid and its successful application as a drill-in and completion fluid in a multilateral (MLT) well on Statoil's Aasgard field, off Mid-Norway.The introduction of highly complex technology, such as multilateral well design with long horizontal reservoir sections, demands a strong focus on the drilling fluid characteristics. Recent field experience showed that conventional oil-based mud (OBM) systems had limitations, when used in a demanding downhole environment influenced by elevated temperatures and ambitious drilling and completion objectives. This resulted in lower than expected drilling efficiency and well productivity. Accordingly, a development program was instituted to qualify a new high-temperature OBM that possessed reduced formation damage potential and superior bridging characteristics while remaining thermally stable.The candidate fluids investigated were OBM of three different types: 1) standard OBM with a mineral base oil, 2) OBM with a linear paraffinic base oil and 3) a low-solids (LS) OBM. The latter was based on an emulsion with a heavy calcium bromide brine as the internal phase and a mineral base oil as the external phase. Bridging materials and organoclay for viscosity were added as the only solids materials.The results of the qualification programme showed that the LS OBM exhibited superior sag stability and much higher return permeability values as compared to the two other oil-based alternatives.The field application of the fluid was very successful. And the Aasgard subsurface team managed to drill and complete a total well path length of about 4900 m. The well was drilled and completed 37 days ahead of plan and produces with a productivity index as expected.
A New Matrix-Acidizing Simulator Based on a Large-Scale Dual-Porosity Approach
Authors: Cohen C. E. , Ding D. , Bazin B. , Quintard M. 
Published: December 2007

Abstract
The principle of a matrix acidizing treatment in carbonated reservoir is to bypass damaged near wellbore zone by creating empty channels called wormholes. The success of the stimulation depends on the ability of an operator to control the unstable process producing those wormholes. Length, size and density of these channels depend on numerous parameters from injection rate to rock properties. Significant efforts have been made in both experimental and numerical studies to optimize stimulation procedures. Today, core-scale numerical models can successfully reproduce the dissolution process, but they are limited in their ability to simulate wormholes at the wellbore scale. Large-scale models are based on semiempirical approaches.
We present in this paper a new simulator for matrix acidizing, built to simulate full acid treatment while considering every mechanism involved in the dissolution process at all physical length scales. It is based on a dual porosity model written at the wellbore scale, and derived from a volume averaging of the Dar?y-scale equations describing acid-rock local equilibrium dissolution. This model can reproduce different types of dissolution patterns, from compact to uniform through dominant wormhole patterns, and it accounts for wellbore-scale heterogeneities. An application of the simulator is presented in this paper. For a given damaged well, we first illustrate the interaction between the wormholing dynamics and the formation heterogeneities. Then we study the optimization of the treatment design, which is function of fluid placement and flow rate. For a set of acidizing parameters, we extract the resulting specific skin factors along the well from simulations. The skin values of each layer are then introduced in a reservoir simulator to calculate the well productivity. An objective function using this productivity change is minimized by an inversion algorithm, to converge toward optimum values of the treatment parameters.
The Centrifuge as a Tool To Determine the Pore-Throat Size Distribution in Plugs
Authors: Martin Carlos A. , Ramia Maximo E. , Barberis Lucas 
Published: December 2007

Abstract
The standard use of the centrifuge is to determine capillary pressure in plugs. What is proposed in this work is to extend its application making it possible to determine the pore-throat size distribution in plugs in addition to the capillary pressure indicated above.
To this end we start with a plug properly cleaned and saturated with the corresponding brine. The plug is then placed in the centrifuge and the collected data consists of the total evacuated brine volume VT(v) as a function of the centrifuge rotation speed v.
A simple model, consisting of capillary tubes running from one end of the plug to the other, is proposed to describe the complex system network of pores and the corresponding interconnecting pore-throats. The corresponding theory, based on treating the capillary pressure as that due to the water-air interphase, is worked out in such a way as to link the capillary size distribution to VT(v) vs. v. The mathematical procedures turn out to be straightforward and the solution is unique. This original analysis of the centrifuge data was successfully applied to a large number of plugs. As an example the corresponding data and analyses are fully given and described. In a companion paper these results are compared with those obtained by MICP (Mercury Injection Core Porosimetry), and the agreement found may be considered as excellent. There is a practical limitation of the method proposed in this work. The capillary pressures that can be reached with the centrifuge are not as high as those that can be reached by MICP. This limitation manifests itself in the fact that pore-throat sizes below 1 μm are poorly detected or not detected at all. However, for pore-throat sizes above that value the agreement is excellent.
The main result obtained in this work is that it is shown that similar information to that produced in a MICP run with two main advantages (1) the centrifuge is a non-destructive experiment, and (2) is a non-contaminating experiment.
Modeling and CT-Scan Study of Foams for Acid Diversion
Authors: Carretero-Carralero M. D. , Farajzadeh R. , Du D. X. , Zitha P. L. J. 
Published: December 2007

Abstract
In this paper we present a 1D and 2D analysis of foam development in porous media based upon a new stochastic bubble population foam model and provide a detailed experimental validation. We present systematic experiments consisting of the co-injection of N2 gas and surfactant solution in homogenous sandstone cores, varying the liquid and gas injection rates. During the experiments X-ray computed tomography (CT) scans were used to map locally the fluid saturations with high spatial and temporal resolution.
Defining and Implementing Functional Requirements of an Intelligent-Well Completion System
Authors: Ajayi Arashi , Konopczynski Michael , Nielsen Victoria Jackson , Giuliani Corrado 
Published: December 2007

Abstract
There are various challenges involved in the design and implementation of an intelligent well system for field development. Different challenges are encountered at different stages of the intelligent well project. In order to arrive at a fit-for-purpose system, each of the challenges will have to be addressed adequately.
These challenges can be categorized under the following: value driver identification, well location, system selection, third party equipment integration, control and monitoring objectives, data management and project management. Addressing these challenges will highlight the relationship between project value drivers, functional well requirements and how these influence the selection of the final intelligent well completion. Provision of feasible solutions to the challenges also requires an integrated approach.
This paper divides the intelligent well completion project into different stages and addresses issues specific to each stage. The authors provide recommendations that increase overall chances of project success and ensure that the promised values of the technology are delivered.
Streamline-Based Integral Modeling for Waterflooding Design Optimization, Surveillance and Monitoring
Authors: Galacho Mirta , Vázquez Pablo , Laiz Gerardo , Krittian Andrés , Gutiérrez Fabián , Pací Victor 
Published: December 2007

Abstract
The Dynamic Numerical Simulation in Flowlines (DNSFL) is an alternative tool adapted to handle Dynamic Models in Fine Scale. This feature has been particularly relevant for studying the current case, a huge multilayered waterflooding process developed in a giant field of great extension reservoirs with considerable facial and stratigraphical variations.
The DNSLF develops these tasks suitably because uncouples reservoir geometry and heterogeneity from transport equations, solving the problems dominated by convective flows in a faster and computationally more efficient way. This allows to build models of greater space discretization and, therefore, to represent better the heterogeneity of the reservoirs.
The analyzed field is constituted by fluvio-lacustrine deposits, nine sand-clay cycles of normal grading (only eight of them were modeled), partially connected reservoirs; with 250 actives wells in commingled production and water injection; and with a long and detailed history of simultaneous primary and secondary events.
In a previous paper (SPE 94815) a Streamline-based Global History Matching of this field was presented. This process enabled to achieve the Geological Modeling Calibration, a clear conceptualization of the current primary and secondary production mechanisms, its productive behavior, and to evaluate the geostatistical and Upscaling procedures to apply for the definition of the Simulation Model.
This paper illustrates how the Integral Model achieved, with a detailed Streamline-based History Matching, is used for Waterflooding Design Optimization, Surveillance and Monitoring, showing that these principles are key factors to understanding reservoir performance and identifying opportunities that will improve the ultimate recovery.
During the detailed History Matching process CPU runtimes around 200 minutes were achieved using a 1225000 grid cells Model, with 190 timesteps, quarterly at the starting, and monthly after, based in a Pentium 4 PC, 3.2GHz CPU and 2GB RAM. It showed that it is possible to work with a big Streamline-based Model in relatively short processing time.
Filtration Effect on Water in Oil Emulsions Stabilization in Slop Crude Treatment
Authors: Ricaurte M. , Perozo H. 
Published: December 2007

SUMMARY
The emulsion (water, crude and solids) remaining in W/O interface after dehydration (water removal) constitutes Slop crude. Its recovery requires more complex processes than conventional treatment of crude because it has a very stable emulsion and vast amounts of fines. In the oil industry filtration is commonly used to treat crudes with such characteristics.
Shear effect, resulting from filtration of a Slop crude from west Venezuela, on emulsion stability and thereby on its dehydration was studied. Static stability tests, at laboratory scale, were conducted. They were carried out on diluted Slop crude, unfiltered and filtered with different meshes size, at different temperatures, injection of moisturizing and demulsifying products, and settling time.
After treatment, water and sediment content (%W&S) was lower in unfiltered crude than in the filtered one. All unfiltered samples reached commercial specifications (&lt;1 %W&S). The parameter studied to explain how the filtration process affects emulsion stabilization was the determination of droplet size on the Slop crude, before and after filtration.
The microphotographs show that filtered samples have smaller droplet size than the unfiltered ones. Thus, evidencing that shear resulting from pressure drops and partial pluggings of meshes lead to decrease in emulsion droplet size and on increase stabilization. This decrease explains why thermochemical dehydration of unfiltered samples is more effective than that of filtered samples.
Based on these results, it was concluded that solid separation through filtration, prior to thermochemical treatment, is negative to dehydrate the studied Slop crude because a decrease of droplet size on the dispersed phase is produced, there by stabilizing emulsion even more.
Assessment of CO2 Corrosion Damage: Likelihood of Failure in Deviated Wells by Deterministic and Stochastical Modelling
Authors: Case R. , Carpio M. 
Published: December 2007

Abstract
Damage due to CO2 corrosion related processes is a cause of major concern regarding the structural reliability of subsurface installations used in oil and gas production. As to well completions, the effective control of CO2 corrosion includes the complete characterization of the operating environment since corrosion rates and CO2 corrosion morphology are closely related to variables such as the presence of multiphase flow, temperature and produced water composition.
In the present paper an a priori damage assessment methodology is used to analyze casing failures observed in deviated wells with electro submergible pumps (ESP) in the Oritupano oilfield (located in eastern Venezuela). The study analyzes the assessment of CO2 corrosion damage and determines the subsequent probability of failure in relation to the structural reliability of the well. The method proposed is based on the mechanistic CO2 corrosion and multiphase flow modelling in order to deliver a comprehensive quantitative description of the expected corrosion rates within the context of the actual well operating environment and completion design.
The probability of failure is quantified by assessing two independent probability events: damage distribution and the fracture mechanics associated failure probability. The corrosion related damage distribution is calculated by using stochastical simulation of the CO2 corrosion mechanisms, linked to the deterministic corrosion study. The fracture mechanics associated probability is quantified by defining the main operating parameters (such as temperature and bottom hole pressure) as stochastically sensible independent variables within the context of a Level 2 Failure Assessment Diagram (FAD), as defined in API 579.
The results obtained explain the difference observed in the reported work over rates between vertical and deviated wells in the specific oilfield (Oritupano A) using the same extraction methodology. It is also possible to predict consistently the reliability curves obtained from actual field data and discriminate among the possible causes of failure.
Fracture Treatments of Horizontal Wells on Western Siberia Oil Field—Maximizing Long-Term Production
Authors: Baranov Dmitry , Kontarev Roman , Senchenko Dmitry , Faizullin Ildar , Gayfullin Albert , Ivshin Anatoly , Kazykhanova Naylya 
Published: December 2007

Abstract
Recently, several Russian oil-producing companies have started to implement various technologies for stimulation of horizontal wells. Due to significant vertical permeability anisotropy of Western Siberia oil reservoirs, hydraulic fracturing treatments seem to be an effective method of production acceleration and sometimes a method of production enhancement.
In this paper, a comprehensive analysis of horizontal wells fractured from 2005–2006 in the Western Siberia oilfield is presented. This paper will discuss a list of criteria for successful candidate selection, suggest some statistical relationships for post-fracturing production forecasting, and show important factors that affect long-term performance. A new fracture treatment design optimization approach was developed on the basis of the best field practices and results of this investigation.
Simulation studies for testing the obtained results were performed using a multiphase flow reservoir simulator and a pseudo-3D fracture simulator. Three types of studies were investigated: (1) "base" cases representing horizontal well production without fracture treatments, (2) "real" cases, a study of treated well performance, and (3) "ideal" cases, which represented a modeling of horizontal well performance for treated wells on the basis of the developed design optimization approach. The impacts of some important factors—such as reservoir pressure decline in drainage zones on long-term, post-treatment production—were estimated using matched "real case" sector models. Refracture cases were also considered. Comparison of well performance for those cases enabled the estimation of long-term production increases resulting from fracturing treatments and potential incremental production increases expected from implementation of the new design approach for the Western Siberia oil field.
Results from this program resulted in new candidate selection criteria, methods for improving the accuracy of post-treatment production forecasting, and a suggested fracture design optimization approach. These important developments can help maximize long-term performance of the horizontal wells in this Western Siberia oil field and consequently can increase output for the operator from that asset.