bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Net-to-Gross Understanding for Horizontal-Development Drilling in Complex Mature Reservoirs
Authors: Thorsen Arve K. , Eiane Tor , Thern Holger , Kroken Asbjørn , Iversen Marianne , Antonsen Frank 
Published: March 2008

Abstract
Determining net-to-gross in complex, mature reservoirs can prove challenging. Mixed lithologies, changes in sand quality and variations in oil-water contacts can, and do, cause uncertainties in the interpretation of conventional LWD measurements. This paper demonstrates how vibration tolerant LWD Magnetic Resonance (MR) measurements were used in the Troll field to address these conventional uncertainties.
Reservoir sands from several wellpaths were characterized using MR data for fluid identification, saturation determination and facies recognition. Fluid saturations are compared to those derived from traditional LWD formation evaluation measurements. Other petrophysical parameters such as porosity and permeability index are also evaluated. Finally, it is shown how the MR-LWD data can be integrated with imaging while drilling data to enhance structural interpretation in horizontal wells, for a new understanding of reservoir rock quality, moveable fluids and the resultant net-to-gross assessment.
The MR-data has proven to add valuable information to StatoilHydro in the understanding of the complex reservoir in its first field application in the North Sea. It was possible to gather high quality MR data in a highly challenging drilling environment
This paper will explore the ability to measure and utilize LWD-MR data to better understand the development of the reservoir of a mature field. The benefit is improved recovery and a better drainage strategy in a complex reservoir.
Future Projection of Energy Prices: A Predictive Model
Authors: Belhaj Hadi A. , Lay T. 
Published: March 2008

Abstract
As developing countries industrialize and rich countries continue to devour power, global energy demand is projected to increase 60% in the next 25-30 years, according to the International Energy Agency (IEA). Fossil fuels will continue to dominate, estimated to account for 85% of future demand. Even if the Saudi Kingdom pumps to full capacity, currently rated at 15 million barrels per day, it is anticipated that oil markets will face continuing high demand, which is to say that the Excess Demand for Oil (EDO) characterizing world oil markets since 1973, will continue to grow. Assuming current rates of consumption, U.S. reserves are forecast to last only another nine years, as domestic production in the U.S. continues a decades-long decline.
This paper, which forms part of a comprehensive study to develop economic models based on futuristic energy pricing policies, increasing globalization and better understanding of environmental impacts, analyzes oil prices over the last two decades as a basis for discussing four principal scenarios for predicting a general oil-price trend for the coming two decades. Concluding that a major supply-alleviating breakthrough from some other non-fossil-fuel alternative is unlikely, it therefore rules out the "Optimistic Model" scenario of a long-term steady-state for oil prices. After carefully considering the exploration efforts to increase the international reserves through new discoveries on the one hand, and the different implemented techniques of improved oil recovery (IOR) for maximizing production from discovered reservoirs on the other, it concludes instead that any of the other three models (two of them categorized as "Realistic") could emerge sometime in the next 3-5 years as the trend-setter.
Building a Reservoir Model with Problematic Faults
Authors: Hoffman K. S. , Neave J. W. , Nilsen E. H. 
Published: March 2008

Abstract
Certain fault geometries can be extremely difficult or even impossible to incorporate into reservoir models due to limitations of the model-building software. Multiple Y or lambda faults are well-known problems, but even more problematic are the half-Y or half-lambda faults. In these situations, the Y or lambda fault truncates against another fault along the length of the second fault, but also extends beyond the length of that fault. Existing modeling methods cannot include such geometries in reservoir models; the modeler usually removes such faults from the model or changes the fault shape so that intersections do not occur. Both of these workarounds alter the reservoir model so that it no longer correctly portrays the actual structure.
Our methodology for fault modeling does not use pillars as the basis for the faults, and therefore does not have limitations in modeling complex fault intersections. Faults are represented as surfaces built from input data only and not artificial pillars. Fault intersections define areas or sections of faults which may be truncated or removed independently of other sections. Y and lambda faults are not considered special cases and can be easily and routinely included in the reservoir model. The ability to specify and manipulate compounds areas of fault surfaces enables the reservoir modeler to create the correct truncations of half-Y or half-lambda faults without compromising the true structure.
The inclusion of such problematic faults in the reservoir model ensures that volumes are correctly calculated within fault blocks, as the faults have not been altered. The sealing nature of these faults can also be assessed and incorporated into the reservoir model, as the faults are an integral part of the reservoir framework; transmissibilities, for example, do not have to be modified in the grid to account for faults that were left out of the original framework.
The ability to include fault geometries which were ignored in the past is a significant break-through in fault modeling technology. Asset teams can now work with a complete and accurate reservoir model and no longer need to ignore significant structural components simply because of modeling limitations.
Limits on Sweep Efficiency for Solvent Injection into Heavy Oil Reservoirs at Grain-scale
Authors: Taghizadeh O. , Sepehrnoori K. , Bryant S. L. 
Published: March 2008

Abstract
The movement of low viscosity fluid through a porous medium containing extremely viscous fluid is an important phenomenon in several petroleum engineering applications. These include the recovery of heavy oil by solvent injection, the preferential reduction of water flow using polymer gels, and the enhancement of acid fracturing treatments. The displacement of one fluid from a porous medium by a second immiscible fluid has been extensively studied in two cases: when capillary forces are dominant, and when viscous forces are comparable to capillary forces.
This study examines a third case: when viscous forces are dominant. The viscosity of the fluid initially present in the porous medium is several orders of magnitude greater than the viscosity of the displacing fluid. Consequently, the displacement through an individual pore will be dictated by the hydrodynamic forces required to move the high viscosity fluid. This study develops a mathematical model of the viscosity-dominated displacement in a network of conduits.
Key practical insights from the model are the nature of the displacement and effects of geometry and hydraulic conductivities on the sweep efficiency.
Sensitivity Analyses of Production and Recovery Forecasts Using Variance-Based Methods
Authors: Lawal Azeez Adeyinka , Srinivasan Sanjay , Lake Larry W. 
Published: March 2008

Abstract
During the exploratory stage of field development, reservoir data required for forecasting is often inadequate, and hence uncertain. An understanding of the scope and extent of uncertainty is invaluable in optimizing data gathering operations, planning of field facilities, and assessing exploration and development scenarios. Sensitivity Analysis (SA), the study of how the uncertainty in a model's outputs depends on the uncertainty in its inputs, provides such an understanding.
This work presents the SA of production and recovery histories using a new continuous time Monte Carlo (MC) multiwell tank model (UTSens). The model assumes that reservoir parameters are independent; knowledge about a parameter, does not affect knowledge about other parameters. The model also assumes that the reservoir is homogeneous and undersaturated, and that the reservoir is produced by primary depletion, specifically volumetric expansion. The MC approach is probabilistic rather than deterministic; as such it computes the mean, variance and sensitivity histories of reservoir and well production rates, recovery, and pressure. The model provides a choice between Latin Hypercube and Sobol LPT sampling. These sampling methods are more efficient than conventional MC or random sampling.
In the cases considered, the sensitivity effects of different parameters vary over the producing period. Parameters with negligible main effects nevertheless can have significant joint effects. In one of the cases considered, the main effects of oil viscosity on production rate declined over twenty years of production with a single well. Conversely, the main effect of reservoir thickness increased during the same period. Other parameters like permeability and initial reservoir pressure with no main effects showed appreciable joint effects.
In its totality, the current work is part of a paradigm shift from deterministic estimates to considerations of probabilistic analysis and uncertainty. This prescription is especially relevant during reservoir exploration and appraisal. Data analysis using the MC tank model provides metrics of uncertainty for optimized data gathering and informed decision-making.
Prediction Of Effective Porosity Over the Field Using 3D Seismic Multiattributes, Seismic Acoustic Impedance And Well-Driven Effective Porosity
Authors: Arianfar Abdonabi 
Published: March 2008

AbstractThe prediction of logs and reservoir properties from seismic data plays a critical role in the characterization of oil and gas reservoirs. Even though the physical relationships between seismic attributes and reservoir parameters are not always clear, statistical relationships should be preferred than deterministic approaches. This technique performs a statistical relationship between well data (porosity) and seismic data (attributes) then a calibration process and a residual correction will be calculated and finally the interpretation for the reservoir properties over the field will be carried out and the map of the log or reservoir parameter of interest will be prepared over the whole field.Mathematically, we refer to multivariate geostatistics, which is a broad term that encompasses all methods like cokriging that utilize more than one variable to predict other variables of interest.A volume attribute is defined as the sum of an instantaneous attribute over an interval. The interval can be specified between two zones, or as a constant window around one horizon or zone. So after extracting a volumetric attribute, each value point of the resulted map is the representative for the whole interval between the top and base of the zone under study, i.e. the resulted attribute map is the representative of the whole interval in average.Effective porosity over producible zones of interest was predicted with the aid of multivariate geostatistics method and following data: –A 3D cube of acoustic impedance.–Quadrature trace, cosine of instantaneous phase and inverse of travel time attributes.–Calculated effective porosity for 5 wells in the field.The objective of this study is to find a link between 3D seismic data, which covers the whole field, and effective porosity that is only determined at 5 wells.
Hybrid Drilling Rig With Rotating Coiled Tubing
Authors: Choudhary Arpit , Menezes Richard , Ogra Konark , Garg Rachit 
Published: March 2008

Abstract
CTU has been gaining importance in the oil industry. It is a multipurpose unit with one application being drilling. The major limitation of CTU was eliminated recently by inventing rotating coiled tubing which is yet to hit the commercial market.
In this concept a conventional derrick based rig is modified to a Hybrid Drilling Rig. A coiled tubing unit is incorporated inside derrick structure itself at a height above the derrick floor which depends on type of derrick. The coiled tubing unit added is not the conventional one instead it is a unit that actually rotates the coiled tubing. This coiled tubing will be placed horizontally above the floor. It has a support structure passing through its center which is detachable. The use of this center structure is that it has straightening injector fixed in it and it supplies the torque to the CTU. Coiled tubing from the CTU will take a helical path around the support structure, pass through the injectors and become straight.
The purpose of the paper is to discuss the advantages and limitations of this hybrid drilling rig technically and economically. Also some calculations are included which are used in the design of the rig used. This paper also outlines fatigue analysis and advantages and limitations of using rotating coiled tubing.
A Critical Review of the Status of SAGD: Where Are We and What Is Next?
Authors: Albahlani A. M. , Babadagli T. 
Published: March 2008

AbstractWith around 7 trillion barrels reserves and recent increase in oil demand, there is no doubt that there would be tremendous effort on the development of heavy-oil/bitumen (HO-B) reservoirs in the next decades. Yet the in-situ recovery of HO-B is still not a simple process and there are many technical challenges accompanied with it.Two major techniques, namely thermal and miscible, have been considered in the HO-B development, along with several other auxiliary methods (chemical, gas, electromagnetic heating etc.) for different well configurations, steam assisted gravity drainage (SAGD) being the most popular among others. Miscible techniques did not yet go to a high commercial level, while thermal techniques have by far a stable foundation in the industry.Despite remarkable amount of laboratory experiments and computational studies on the thermal techniques for HO-B, especially SAGD, there was no extensive and critical literature review of the knowledge gained over almost three decades. We believe that a critical review of the status of the SAGD process will fill the gap by shedding light on the deficiencies and limitations of the process, further development areas, and new research topics. Specific attention, in this paper, was given to (a) the effect of geological environment on the physics of the process, (b) evaluation of the laboratory scale procedure and results (reasons of residual oil saturation, is it well configuration or pore scale dynamics?) and the reasons of the inconsistency between the lab and field scale performances, (c) problems faced in numerical modelling (capturing the physics of the process, relative permeability curves, dynamics of gravity controlled counter-current flow), (d) evaluation of the pilot and commercial level field applications, and (e) operational and technical challenges.It is believed that a good compilation of the records produced over three decades will constitute a useful reference for the industry and academic people.
A Sensitivity Analysis for Effective Parameters on Fracture Network Permeability
Authors: Jafari A. , Babadagli T. 
Published: March 2008

Abstract
Fracture network mapping and estimation of its permeability constitute two major steps in static model preparation of naturally fractured reservoirs. Although several different analytical methods were proposed in the past for calculating fracture network permeability (FNP), different approaches are still needed for practical use. We propose a new and practical approach to estimate FNP using statistical and fractal characteristics of fracture networks. We also provide a detailed sensitivity analysis to determine the relative importance of fracture network parameters on the FNP in comparison to single fracture conductivity using experimental design approach.
The FNP is controlled by many different fracture network parameters such as fracture length, density, orientation, aperture, and single fracture connectivity. Five different data sets were generated for random and systematic orientations. In each data set, twenty different combinations of fracture density and length for different orientations were tested. For each combination, ten different realizations were generated. The length was considered as constant and variable. This yielded a total of one thousand trials. The FNPs were computed through a commercial discrete fracture network modeling simulator for all cases. Then, we correlated different statistical and fractal characteristics of the networks to the measured FNPs using multivariable regression analysis. Twelve fractal (sandbox, box counting and scanline fractal dimensions) and statistical (average length, density, orientation and connectivity index) parameters were tested against the measured FNP for synthetically generated fracture networks for a wide range of fracture properties. All cases were above the percolation threshold to obtain a percolating network and the matrix effect was neglected.
The correlation obtained through this analysis using four data sets was tested on the fifth one with known permeability for verification. High quality match was obtained.
Finally, we adopted experimental design approach to identify the most critical parameters on the FNP for different fracture network types. The results were presented as Pareto charts. It is believed that the new methodology and results presented in this paper will be useful for practitioners in static model development of naturally fractured reservoirs and will shed light on further studies on modeling and understanding the transmissibility characteristics of fracture networks.
Evaluation of Intra-Molecular Cross-Linked Polymers
Authors: Wang W. , Lu X. G. , Xie X. 
Published: March 2008

Abstract
There are two types of cross-linked reactions to form polymer gels, intra-molecular cross-linked reaction that takes place within a polymer molecule, and inter-molecular cross-linked reaction that takes place among different polymer molecules. Viscosity measurements and flow performance tests can be used to differentiate between intra-molecular and inter-molecular cross-linked reactions. Viscosity increases with time if inter-molecular cross-linked reaction occurs in a polymer solution, but stays constant or slightly decreases with time if intra-molecular cross-linked reaction occurs. Flow resistance and residual flow resistance increase when intra-molecular cross-linked polymer gel is injected into the porous media. This phenomenon is not observed with polymer injection.
Cross-linked reaction in a polymer solution is affected by the concentrations of the polymer and the coagulant, electrolyte type and concentration, temperature, and pore size and structure. Laboratory results show that high electrolyte concentration and temperature (in a reasonable range) can increase the tendency for intra-molecular cross-linked reaction. The higher the concentration of electrolytes, the more the polymer molecular clews curl and contract, improving the probability for intra- molecular cross-linked reaction to occur. For the three studied electrolytes, Ca2+ is more likely to enhance the intra-molecular cross-linked reaction, Mg2+ is not as good as Ca2+ but better than Na+. Three of the possible intra-molecular cross-linked polymer gels that are verified by the viscosity tests are injected into the artificial cores for flow performance tests. The results confirmed the intra-molecular cross-linked reaction in the tested polymer gels. The mechanisms of curling and stretching of polymer molecular clews may be explained by Stern-Grahame double layer theory.
Improved Analysis of the Kinetics of Crude-Oil In-Situ Combustion
Authors: Cinar M. , Castanier L. M. , Kovscek A. R. 
Published: March 2008

Abstract
In-situ combustion (ISC) is an effective thermal recovery process that provides an important alternative to steam injection. ISC is the process of injecting air into a reservoir to oxidize a small portion of the hydrocarbons present to generate heat and pressure. It suffers from fewer reservoir limitations than steam injection, but is not applied widely. One factor that has limited application of ISC is lack of predictability at both the laboratory and field scale. Proper experimental kinetic analysis (using, for instance, ramped temperature oxidation) provides critical parameters, such as activation energy, for modeling efforts. Conventional methods of kinetic analysis for crude oil assume, a priori, a two-step or three-step oxidation reaction.Any in-consistency between the assumed model and the real system is reflected as error in model parameters.Iso-conversional tech-niques, as applied here, provide model-free methods for estimating activation energy and naturally deconvolve multi-step reactions. The iso-conversional approach obtains the reaction kinetics for a given rock/oil sample at identical reaction extent from multiple experiments with different heating rates.The technique has never been applied to ISC kinetics, to our knowl-edge. Our work falls into two major sections.First,the applicability of the iso-conversional method to multiple step oxidation of oil in porous media is established via synthetic examples. Second, and on the practical side,the combustion kinetics are reported for two quite different crude oil samples thereby adding to the knowledge base of crude-oil and rock-matrix charac-teristics that make for successful ISC. The iso-conversional analysis of ramped temperature oxidation data appears to provide new insight into systems where ISC is/is not successful.
Liquid Carrying Capacity of Gas in Underbalanced Drilling
Authors: Guo Boyun , Yao Yuan , Ai Chi 
Published: March 2008

Abstract
Air/gas drilling is a technique of Underbalanced drilling (UBD) used for increasing rate of penetration in relatively dry formations. Fluid conversion from air/gas to foam frequently causes drilling complications to drilling engineers. This is mainly due to the lack of understanding of liquid loading problem and limited knowledge of liquid-carrying capacity of gas.It is highly desirable to gain the insight of the problem and develop techniques to minimize drilling complications.
Based on Turner’s theory of liquid loading in gas production wells, we have established in this study the minimum kinetic energy criterion for flowing gas to carry liquid up the borehole in air/gas drilling. A theory for estimating the minimum required gas injection rate to remove formation liquid influx has been established. A calculation procedure has been developed for estimating the minimum required gas injection arte to remove a given rate of fluid influx from the formation. Engineering charts have been generated for predicting the liquid-carrying capacity of gas that is injected into the borehole at various rates. This paper provides drilling engineers necessary knowledge and a useful tool for minimizing complications in air/gas drilling.