bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Polymer Displacement in Hydraulic Fractures at the Pore-Scale
Authors: Balhoff Matthew , Thompson Karsten E. 
Published: December 2007

Abstract
Proppant-packed fractures provide a relatively low-resistance pathway for the recovery of reservoir fluids. However, residual polymer left over from the proppant transport can greatly reduce the fracture conductivity and, therefore, productivity. Poor fracture cleanup is often observed and it is important to understand the fundamental reasons behind the phenomenon. It is believed that non-Newtonian fluid rheology, viscous fingering, and leak off may all contribute to the problem. The vast majority of fracture cleanup modeling has been limited to continuum-scale modeling. However, important aspects of the cleanup problem may be affected by pore-scale events. For this reason, it is desired to model flow at the pore-scale to obtain a better understanding of the qualitative fingering patterns and quantitative flowrates in a fracture during the cleanup process, as a function of basic parameters such as proppant size, fluid rheology, and imposed pressure gradients. These pore-scale results may help explain the fundamental reasons for the observed poor polymer cleanup and give insight on how to improve cleanup in the future.
In this work, computer-generated, random sphere-packs are used to approximate a small portion of the propped fracture. The sphere-packs are transformed into physically representative networks of pores and connecting throats. The network models are used to model flow through the proppant pack at the pore-scale. Modeling the dynamic cleanup process consists simulating a low-viscosity, Newtonian fluid (e.g. water) displacing a high-viscosity, non-Newtonian polymer from the pack. A novel approach is used to couple the network to a continuum model for flow in the reservoir, and realistic boundary conditions are used that allow the displacing fluid to flow in from the side of the fracture. Current modeling is used to better understand displacement behavior under different conditions. Future results will be upscaled and integrated with large-scale reservoir models.
Role of Surveillance in Improving Subsea Productivity
Authors: Amin Amin , Smedstad Eric , Riding Mark 
Published: December 2007

Abstract
A number of industry sources have identified the need to improve overall productivity of subsea wells through the application of monitoring and control systems in the wellbore and on the seabed. To achieve this goal, two elements must be mastered: information and measurements of key attributes of the well/reservoir productivity, and a means to change and command the process, preferably through remote-controlled devices rather than traditional well intervention.
With the advent of intelligent wells, the second element has been addressed through a variety of process control devices used at different points in the wellbore and on the seabed. However, the growth of this process was limited by the absence of effective information gathering and data transmission systems in subsea wells, which remained underdeveloped compared to other subsea hardware. This resulted in systematic information bottlenecking caused by poor connectivity between the wellbore and the rest of the subsea infrastructure.
The paper introduces a complementary surveillance system that works with existing subsea devices and highlights its role in gathering and transmitting well and subsea data reliably and in sufficient time needed to maintain optimal production. In particular, the system targets high data traffic areas in order to de-bottleneck the subsea transmission systems and provides wellbore monitoring and inflow quantification. A continuous data highway is now available to both wellbore and subsea-based measurements, leading to improved monitoring and control of the entire subsea system.
The applications and benefits of the system are demonstrated through a case study. The study discusses the role of the surveillance system in bringing the productivity index of subsea wells to be in par with the platform wells. It also demonstrates the need to rethink the flow assurance process as increasing number of distributed seabed measurements become available to the subsea industry and tie-back distances increase to make the best use of expensive host facilities.
Can You Have Probable Without Proved Reserves?
Authors: Etherington John R. , Hunt Elizabeth J. 
Published: December 2007

Abstract
One of the unresolved issues in reserves evaluations is the continuing practice of assessing probable reserves for projects where no proved reserves have been claimed.
The practice typically arises in the early delineation stage. The initial assessment of best estimate recoverable quantities (proved plus probable ("2P")) meets internal criteria sufficiently to justify development. While the project is potentially commercial, it may not meet all the criteria for disclosure of proved reserves under regulatory guidelines. In this paper, it is assumed that governing agency is the U.S. Securities and Exchange Commission (SEC).
The issue is an interesting exercise in logic. Is probable a discrete entity or is it merely the incremental volume beyond proved in a 2P estimate? If no part of the accumulation meets the proved reserves criteria, then can the total 2P estimate be classified as probable reserves?
The resolution may lie in more careful application of the full resource classification published by the Society of Petroleum Engineers (SPE) in 2000. The SPE recognized that ambiguity may exist between their definitions of uproven reserves and contingent resources. While reserves are accumulations that are recoverable under current conditions, this same distribution of volumes would be classified as contingent resources if technical and/or commercial risks prevent development commitment. The separation of risk and uncertainty in the assessment process is critical.
One solution is to initially classify volumes associated with all new discoveries as contingent resources with its internal certainty categories (low/best/high estimates) until such time as the SEC proved reserves criteria are satisfied. As contingencies are removed, volumes would then be transferred to reserves subdivided into parallel certainty categories of proved (1P), proved plus probable (2P) and proved plus probable plus possible (3P).
It may or may not be that simple; this paper critically examines associated issues with examples.
A Methodology to Discover Contaminated Data in Spatial Databases
Authors: Wei Mingzhen , Sung Andrew H. , Cather Martha 
Published: December 2007

Abstract
In this information age, the problem of data quality deserves more attention than it is getting. Contaminated or corrupted data are data that were misunderstood or misrecorded in data sets. The success of the petroleum industry relies upon a combination of multi-dimensional reliable information and proper cross-disciplinary techniques. Contaminated data can mislead the strategic-level decision making and cause operational failures.
This paper presents a methodology to identify contaminated data in large spatial data sets in the data quality control cycle. Graphical and quantitative spatial outlier detection methods are discussed. All these methods are different for identifying spatially abnormal data, both in mechanisms and results. This paper discusses these methods and compares their advantages and disadvantages. The effectiveness of these methods is evaluated by using a real spatial database, the Produced Water Chemistry Database (PWCD) in New Mexico.
Mechanisms and Main Parameters Affecting Nitrogen Distribution in the Gas Cap of the Supergiant Akal Reservoir in the Cantarell Complex
Authors: Rodríguez Fernando , Sánchez José L. , Galindo-Nava Agustín 
Published: December 2007

Abstract
An analysis of the mechanisms and main parameters that determine the distribution of nitrogen in the gas cap of Akal, a super giant naturally fractured reservoir in the Cantarell Complex, during nitrogen injection for pressure maintenance, is presented in this paper.
The analysis follows from a dual porosity compositional numerical simulation study aiming at history matching the behavior of the Akal field, observed before and after nitrogen injection started, particularly the matching of nitrogen concentrations measured in wells invaded by the advance of the gas-oil contact and in other gassed out wells located at the top of the reservoir.
Molecular diffusion and natural convection were considered in matching the observed gas-cap nitrogen distribution of the Akal reservoir, besides other conventional transport mechanisms. It was found that gravity drainage, effective molecular diffusion and the partition of total porosity between matrix and fractures are the main parameters controlling flow dynamics and affecting the distribution of nitrogen in the gas cap. It was also found that these parameters have an impact on the diffusion of nitrogen into the oil column. Analysis of results also shows that gas-cap gas and nitrogen gravity differences play an important role in the distribution of nitrogen in the gas cap and that natural convection, under current conditions, is not relevant. Another finding is that the main transfer mechanism for nitrogen into the gas-cap matrix blocks is the substitution of the gravity-drained oil and that exchange by molecular diffusion is very slow.
In matching the distribution of nitrogen in the gas cap, distinction between small-scale secondary porosity, which dominates fluids flow locally, and large-scale secondary porosity, which dominates fluids flow at the scale of the reservoir, was required. The way this requirement was handled in the dual-porosity model is described.
A New Method for the Determination of Gas Condensate Well Production Performance
Authors: Xiao J. J. , Al-Muraikhi Ahmad J. 
Published: December 2007

Abstract
The determination of gas condensate well production performance when a well's flowing bottomhole pressure is below the original gas dew point requires condensate banking to be taken into account. This can be accomplished with reservoir simulation models with fine grids near the well. The calculation can be significantly speeded up with relatively coarse grid models by applying the two-phase pseudopressure technique.
The two-phase pseudopressure technique, however, cannot be applied independently for well performance evaluation since it requires the well production gas-oil ratio as an input. Simplified methods have been published recently to calculate gas condensate well production deliverability without the use of reservoir simulators. This paper presents a new calculation method. The new method models condensate banking by considering the combinational effects of condensate dropout (PVT effect) and condensate accumulation (relative permeability behavior). This new approach gives a better understanding of the mechanisms involved.
The proposed method is verified with simulation data presented in the literature. The new method gives results that are in good agreement with published data for vertical, fractured and also horizontal wells. High gas velocity impact near the wellbore (non-Darcy flow and high capillary number effect) can be incorporated into the method. As with other simplified methods, the new technique allows quick well performance evaluation as well as full field modeling involving multiple wells and surface facilities without reservoir simulations.
History Match Tuning Through Different Upscaling Algorithms
Authors: Allam Farid A. , El-Banbi Ahmed H. , Bustami Sami S. , Saada Tamer H. , Fahmy Ismail I. 
Published: December 2007

Abstract
Although computer power has significantly increased in recent years, the need for upscaling is still mandatory to save run time for many reservoir-modeling studies. In this paper we demonstrate the results of reservoir upscaling using nine different algorithms. A comprehensive evaluation for these upscaling methods was performed using several models with increasing complexities and heterogeneity.
Several simulation models were constructed to investigate the effect of the upscaling technique on the quality of the simulation results (including history matching). A very fine model, closest to the geological model, was constructed as a benchmark. Simulation models were then upscaled using nine different upscaling techniques for both natural depletion and water injection driving mechanisms. The models were run for a period of time and the results were compared with those of the fine model. The results were treated statistically to quantify the resultant deviation (errors) from the benchmark results. It was found that some of the upscaling techniques gave better results than others.
In this paper, we also suggest a road map to follow when upscaling geological models and discuss the upscaling for different levels of refinement. The suggested procedures can be applied to many modeling problems and is expected to save time in simulation studies.
Experimental Analysis of Primary and Secondary Oil Recovery from Matrix by Counter-Current Diffusion and Spontaneous Imbibition
Authors: Hatiboglu C. U. , Babadagli T. 
Published: December 2007

Abstract
Matrix–fracture interaction is a commonly encountered process in fractured subsurface reservoirs during oil, gas, and geothermal fluid recoveries and contaminant transport. It occurs in counter-current manner if the interaction between matrix and fracture takes place from the same side. In the first part of this paper, the effects of the matrix shape factor, wettability, and interfacial tension on the rate of capillary imbibition and development of residual non-wetting phase saturation were studied experimentally. In the second part, secondary oil recovery by diffusion of a solvent from the samples exposed to capillary imbibition is investigated. Primary diffusion experiments were also performed on selected core sizes for comparison.
To achieve all these, experiments were conducted on Berea sandstone samples. Cylindrical samples with different shape factors were obtained by cutting the plugs ½, 1 and 2 inches in diameter and 2, 4, and 6 inches in length. All sides were coated with epoxy except one end. Static imbibition experiments were conducted on vertically and laterally situated samples where the imbibition took place upward and lateral directions, respectively. Brine-kerosene, brine-mineral oil and surfactant solution-mineral oil pairs were used as fluids. The rate of imbibition was evaluated for different matrix size, shape factor, wetting/non-wetting phase types and IFT. Conditions at which the shape factor controls the residual oil development were identified.
Diffusion experiments were conducted using n-heptane as a solvent. In addition to the cores exposed to full capillary imbibition, oil saturated (virgin) cores were also tested. To serve as a benchmark, uncoated versions of two different core sizes were used.
It was observed that the residual oil after capillary imbibition is controlled by the matrix shape factor for the vertically positioned samples unlike horizontal samples. Surfactant concentration plays a role on the rate of imbibition and the development of residual oil saturation.
Primary and secondary diffusion experiment showed that it could be more efficient to begin the oil recovery process by capillary imbibition (primary recovery) then continue with diffusion (secondary recovery) depending on the matrix shape factor.
The Boris Field Well Management Philosophy-the Application of Permanent Downhole Flowmeters to Pressure Transient Analysis: An Integrated Approach
Authors: Coludrovich E. J. , McFadden J. D. , Palke M. R. , Roberts W. R. , Robson L. J. 
Published: December 2007

Abstract
Considering the large capital investments and returns for high rate completions in overpressured, unconsolidated sandstone reservoirs, a testing methodology with defined objectives, designed to define acceptable risk levels for rates of individual completions is necessary. Critical parameters, such as permeability and skin, are dynamic properties in these types of reservoirs and require frequent measurement. BHP Billiton has implemented a program in the Boris Field that relies on the use of permanent downhole pressure gauges and flow meters. The well management philosophy and integration of pressure transient results is described, and our approach and experiences since first oil will be reviewed.
Our program relies on several novel well test approaches. A) Intermittent, unplanned build-ups can be analyzed to arrive at a continuous history of permeability and skin. B) Permanent downhole flowmeter data allows for analysis of unplanned build-ups which otherwise would be uninterpretable. C) Methods to quality control the results such as specialized trend plots of skin and permeability are reviewed.
Wellbore management is constrained by limits established by drawdown, flux, water handling, and flow assurance. Surveillance is performed by corroborating the instantaneous well performance from the permanent flowmeters with the most recently interpreted properties. Observations are presented about the utility of intermittent, unplanned shut-ins compared to planned tests.
This process is evolving and requires the advancement of available industry tools with regard to data handling and the use of classical analytical pressure transient techniques combined with numerical methods. Historical data files for individual completions using continuous downhole data are very large which makes manual manipulation of the files undesirable. Management of the data and the impact on the methodology is reviewed
Pushing the Limits of Hydraulic Fracturing in Russia
Authors: Economides M. J. , Demarchos A. S. , Mach J. M. , Rueda J. , Wolcott D. S. 
Published: December 2007

Abstract
We have established the concept of Unified Fracture Design (UFD) to maximize the dimensionless productivity index (JD) following a hydraulic fracture treatment. For a given mass of proppant there is a specific dimensionless fracture conductivity, which we called the optimum, at which the JD becomes maximum. The Proppant Number is a seminal quantity unifying the propped fracture and the drainage volumes and the two permeabilities, those of the proppant pack and the reservoir.
For each injected proppant mass there is a corresponding Proppant Number and, at the optimum conductivity, the dimensionless PI can be readily determined. Increasing the proppant mass or the proppant-pack permeability would result in an increase in the JD, which has a maximum limit of approximately 1.9. In a recent publication we have shown how to push the limits in hydraulic fracturing by injecting very large volumes of proppant of very large retained permeability.
There are physical constraints to our approach, one of which is an upper limit of the net pressure resulting from both the physical limitations of injection equipment and tubulars but also from the need to prevent undesirable fracture height migration. However, the use of much larger proppant pack permeability leads to a correspondingly smaller width for the same fracture conductivity. The smaller width requirement allows the injection of far larger proppant masses before the net pressure constraints are met. This is a departure from current industry practices, which are aimed to "save" injection costs for a specific rate. Our approach, in medium to high permeability formations is to maximize the rate within the injection constraints. Rudimentary economics suggest that such treatments pay for themselves in just a few days of incremental production.
We present here field case studies and results showing the application and success of our design approach.
Gelled Organic Acid System for Improved CaCO3 Removal in Horizontal Openhole Wells at the Heidrun Field
Authors: Selle Olav M. , Wat Rex M. S. , Nasvik Haavard , Mebratu Amare 
Published: December 2007

Abstract
To remove calcium carbonate (CaCO3) damage from openhole wells, proper contact with treatment fluids must occur. Poor results are often caused by the improper placement of acid. Such was the case in the horizontal, openhole wells with sand screens on the Heidrun Field (Norwegian Sea). In these wells, bullheading plain HCl acid to dissolve carbonate kill pills provided only temporary effectiveness.
Recently, an operator and a service company initiated a joint project to study Heidrun's CaCO3 removal problem. Two wells were selected as candidates because of their severe CaCO3 plugging. Repeated attempts to remove the damage with HCl bullheading resulted in improved productivity that lasted only until the wells quickly became plugged. The temporary gain seemed to come from the heel of the wells. The team surmised that treatment could be improved with more uniform placement of acid. To provide a more even distribution of the acid treatment, the team developed a gelled organic acid system.
This paper describes the product qualification process and the chemistry of the new gelled organic acid system. A diversion technology study screened possible treating methods, and different gelling products were tested for potential formation damage, viscosity profile, and gel-breaking characteristics. A purified xanthan polymer with an added breaker was selected for further evaluation. When used to viscosify HCl, the gel-breaking time of the xanthan gel was too short for bullheading applications at Heidrun. Subsequently, an organic acid blend with acceptable CaCO3 dissolution power was formulated, and an environmentally acceptable corrosion inhibitor was incorporated.
Two case histories are presented to show that the system was applied with success. The gelled organic acid system is now qualified for use in the Heidrun Field. This system is applicable to most types of completions and the paper includes a discussion of its benefits.
Soft Sensing for Gas-Lift Wells
Authors: Bloemen H. H. J. , Belfroid S. P. C. , Sturm W. L. , Verhelst F. J. P. C. M. G. 
Published: December 2007

Abstract
This paper considers the use of extended Kalman Filtering as a soft-sensing technique for gas-lift wells. This technique is deployed for the estimation of dynamic variables that are not directly measured. Possible applications are the estimation of flow rates from pressure measurements or the estimation of parameters of a drift-flux model. By means of simulation examples different configurations of sensor systems are analyzed. The estimation of drift-flux model parameters is demonstrated on real data from a laboratory set-up.