bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abandonment Decisions and the Value of Flexibility
Authors: Begg S. H. , Bratvold R. B. , Campbell J. M. 
Published: December 2007

Abstract
This paper describes an investigation of abandonment decisions and shut-in policy as a function of uncertainty in oil price. We first review a fundamental error that is often made in predicting the outcome of, and hence making decisions about, systems that are subject to uncertainty: for many common models, the use of "best" estimates of the uncertain input parameters to the model does NOT result in the "best" estimate of the model's output ("best" is defined as average, or minimum error). The same argument applies to predicting output statistics, such as P10 or P90, from corresponding input statistics. This is part of the reasoning behind, for example, the use of geostatistical simulation models of the sub-surface, rather than smoothed, spatially-averaged models.
In this work the focus is on decision errors caused by temporal averaging, specifically, the "smoothing out" of oil price fluctuations over time, and by restricting uncertainty investigations to the uncertainty in parameters of smoothed price models. We illustrate these points by application to determining optimal abandonment decision policies. We show that it is better to wait for a period after first going cash-flow negative, and how to estimate the length of that time. We also show that these conclusions are relatively insensitive to the oil-price model parameters. Further we show that, if maximizing NPV is the objective, then contrary to normal operating procedures, it is more economic to choke-back production in periods of low oil price.
Use of Dynamic Modeling in Preparations for the Gullfaks C-5A Well
Authors: Rommetveit Rolv , Fjelde Kjell Kåre , Frøyen Johnny , Bjørkevoll Knut S. , Boyce Graham , Eck-Olsen Johan 
Published: December 2007

AbstractDynamic flow modeling has been an essential part of the planning for the Gullfaks C-5A well. This paper discusses the use of such modeling and presents the main results related to:Design of operational window Transient scenarios Development of detailed procedures. Training Flow test modeling Design of under-balanced cementingFirst, the operational window was defined by means of steady state modeling. Various combinations of influx rates and choke pressures were simulated to ensure that bottomhole pressure could be controlled. Also modeling was applied to ensure that proper hole cleaning was maintained during the operation. Modeling of the running of the 7" liner quantified the surge/swab pressures and laid the basis for the liner running procedure.Next, a number of scenarios were developed by means of transient simulations. It was essential to evaluate the dynamics of the system if a fracture with high productivity was drilled through. This would assist the wellsite team detecting the situation and making the correct adjustments with the choke to maintain BHP. Also the effects of choke adjustments on the production rate as well as the transient conditions in the well were evaluated. Various procedures were simulated e.g. connection procedures in order to arrive at the optimal for this well.Dynamic modeling was an important element in the well specific UBD training course which was held for all the personnel involved in the operation. This increased the understanding and preparedness of the crew prior to operation.Modeling of the flow test prior to the drilling of the planned section was also performed.The displacement of heavy kill mud out of the well under pressure was modeled prior to the operation.Modeling of the underbalanced cementing operation was performed for the purpose of developing guidelines for controlling the choke while maintaining constant bottomhole pressure.
Pressure Stability Analysis for Aerated Mud Drilling Using an Analytical Hydraulics Model
Authors: Guo Boyun , Ghalambor Ali 
Published: December 2007

Abstract
Fluctuations in the borehole pressure has been generally recognized as one of the major problems in aerated mud drilling due to its detrimental impact on borehole stability and formation damage. This paper focuses on analyses of bottomhole pressure fluctuations due to circulation break and backpressure variation. The pressure fluctuations due to circulation break is characterized by the gradient loss defined as ECD less EMW. The pressure fluctuation due to backpressure change is evaluated using the pressure instability factor defined as the ratio of change in the bottomhole pressure to the change in the surface choke pressure.
Sensitivity analyses with an analytical model indicate that the gradient loss decreases with depth, increases with both liquid pumping rate and gas injection rate, and decreases with backpressure. The analyses also show that the pressure instability factor increases with depth, decreases with both liquid pumping rate and gas injection rate, and increases with backpressure. At a given depth and backpressure, it is the combination of liquid and gas flow rate, rather than the injection GLR, that determines the pressure instability factor. Following a change in the backpressure, the transition time for borehole pressure to stabilize at a new level depends on several factors including well depth, well geometry, and liquid pumping rate.
This paper presents an easy-to-use method for predicting pressure fluctuations and identifies key factors affecting the pressure stability in aerated mud drilling. The results can be applied to designing of hydraulics for Underbalanced drilling (UBD) and managed-pressure drilling (MPD) wells.
Forecasting US Natural Gas Production into year 2020: a comparative study.
Authors: Garcia Anangela , Mohaghegh Shahab D. 
Published: December 2007

Summary
There are several models for predicting US natural gas production. The most referenced model is the one developed and used by the Energy Information Administration (EIA). Recently a model was developed at Texas A & M University that used neural networks in order to learn from the past when predicting the future. One of the major short comings of the existing models is the fact that they appear to be too certain about their predictions. In other words, they fail to take into account the uncertainties associated with predicting many of the parameters that are inputs into their models and treat them as a certain single values.
In this paper authors present a new model with several advantages over the existing models. First, this model treats the US Natural Gas Production as a time series with all its inherent complexities and incorporates the required methodologies during the development process. Second, this model does not use parameters such as gas price as an input. If we know the future price of gas, then predicting the production levels will not be so difficult. Third, this model does not assume that crisp and exact information is available on the future values of all the input parameters such as GDP, Population and average depth of oil and gas wells. Instead by incorporating a Monte Carlo simulation approach, it uses a probability distribution function for each of its input parameters, and hence the outcome of the model (US Natural Gas Production) is not a crisp number for each year rather it is a range that includes a minimum, a maximum and a most likely value.
The model is developed using the state-of-the-art in intelligent systems by using data up to year 1998. The model is then validated by comparing its results with actual US Natural Gas production for years 1998-2002 as blind (verification) years. During this five-year period this model outperforms all the existing models in the literature. The US Natural Gas production is then forecasted until year 2020.
Successful Application of Hydrajet Fracturing on Horizontal Wells Completed in a Thick Shale Reservoir
Authors: East Loyd E. , Grieser William , McDaniel B. W. , Johnson Bill , Jackson Randy , Fisher Kevin 
Published: December 2007

Abstract
The evolution of well completions in the Barnett Shale Reservoir of North Texas has moved into the realm of horizontal wells. This move was clearly evidenced by an increase from 10 permits in 2002 to more than 100 permits in 2003 to drill Barnett Shale horizontals. In late 2003 and into 2004, success with horizontal completions has possibly proliferated the most in the more economically challenging areas of the field (outside of Denton and Wise Counties) where the Viola "bottom" is poor to absent, making Ellenburger water a concern.
Conventional fracturing processes that were well defined in the vertical well stimulation arena have helped to shape the completion strategies of horizontal wellbores, such that operators generally assume that a large-volume, light-sand waterfrac stimulation will be a requirement. However, many are concerned that fracturing of uncemented liners may not provide adequate effective reservoir drainage in horizontal wells. At times, these concerns have pointed to a need for complicated and expensive multistage fracture treatments using cemented liners to get complete lateral zone coverage.
At least one Barnett Shale operator has made extensive use of microseismic fracture mapping during fracture stimulation of horizontal wells for both cemented and noncemented liner completions. Additionally, wells with cemented and noncemented casing have been completed using the relatively new hydrajet-fracturing technology and were microseismic mapped. This paper presents a comparison of varied completion techniques and what has been learned from these mapping efforts.
Using Rotating Control Devices Safely in Today's Managed Pressure and Underbalanced Drilling Operations
Authors: Cantu Joseph A. , May James , Shelton Jaye 
Published: December 2007

Abstract
In today's Underbalanced and Managed Pressure Drilling environments the Rotating Control Device (RCD) is no longer simply a flow diverter, but is a key piece of well control equipment and the critical first safety defense to prevent escape of well fluids during critical drilling operations. The RCD should not be considered just another piece of rental equipment to be called out at the last minute. When planning a UBO or MPD well it is important to consider the RCD, and consult with the supplier early in the planning stages.
This discussion will attempt to identify the information required to properly select the RCD device and trim, define ancillary equipment needed, and assign responsibilities to various parties to ensure that fit for purpose materials and information are available at the rig site when needed. Procedures and safety precautions for installing the device will be addressed. Operational considerations to insure safety while drilling and maintaining the sealing elements and bearings will also be covered.
Benefits and Challenges Associated with CRA Injection Tubing in Corrosive Gas Wells
Authors: Sullivan R. xsB. , Hinson D. L. , Hendrix D. E. 
Published: December 2007

Abstract
The use of chemical injection (1/4" capillary) strings has gained tremendous popularity in the oilfield during the last few years. Application of these duplex stainless steel strings are now routinely used not only for corrosion chemical injection but also for injecting fresh water where downhole salt precipitation is present, as well as injection of foamer to address water loading issues.
This paper describes an exhaustive investigation into the repetitive failure of these orbital welded duplex stainless steel strings due to environmental cracking in Anadarko's prolific Bossier play. Anadarko currently is very active with 12 drilling rigs running in Freestone County, Texas. The Bossier formation is encountered at a depth of 13,000 ft with a bottom hole temperature of 300 deg F. The gas stream typically contains 3% CO2, 3-5 ppm H2S, and the produced water is saturated with chlorides.
Failures have occurred in numerous wells throughout the field. The paper details the root cause failure analysis investigation conducted, and the influence of well environment, tubing manufacturing process, and tubing material properties in failure. A risk-based approach was used in an attempt to predict tubing failure based on well conditions and material properties. The risk matrix was rationalized against a database of approximately 70 tubing failures. Parameters used in the risk matrix included weld type, weld and base metal hardness, and austenite/ferrite volume fraction ratios. The rationale and factors influencing replacement-tubing decisions (alternate metallurgy) to minimize the occurrence of failures is also described.
Fast Method Finds Infill Drilling Potentials in Mature-Tight Reservoirs
Authors: Guan L. , Du Y. 
Published: December 2007

Abstract
Infill drilling has been identified to play an important role in improving oil or gas recovery in the tight hydrocarbon fields. But quantifying the infill drilling potentials in producing tight hydrocarbon fields is often a challenging problem, due to large variability in rock quality, well spacing, well completion practices, and the large number of wells involved. At the same time, with the increasing demand for energy and favorable oil and gas prices, more and more fields all over the world are undergoing infill drilling. It is not uncommon for a company to have hundreds or thousands of infill candidates to choose from. Complete integrated reservoir studies to determine infill potential are often very time-consuming and costly for many tight hydrocarbon fields.
This paper presents an alternative approach to conduct detailed reservoir studies to find infill drilling potentials in tight hydrocarbon basins. This method can quickly evaluate the infill drilling potentials within weeks even with thousands of wells. Several field examples are provided to demonstrate the application of the method in mature-tight gas basins and the primary advantages of the technique are its speed and reliance upon well location and production data only.
Pushing Fracturing Limits to Maximize Producibility in Turbidite Formations in Russia
Authors: Rueda J. I. , Mach J. , Wolcott D. 
Published: December 2007

Abstract
Engineers use boundary-dominated productivity equations for fracture designs in medium permeability formations. These equations are critical to optimize fracture designs and are different for primary depletion and formations under waterflooding processes.
This paper presents two new models to calculate the dimensionless productivity index, JD, of finite-conductivity fractured wells producing either at pseudo-steady or steady state conditions. These models use a new "definition" of the equivalent wellbore radius to incorporate the finite conductivity and fracture penetration dependency of the solution. New easy-to-use correlations (from 1500 numerical simulation runs) to calculate consistent shape factors and f-functions for fractured wells are also presented in the paper. The f-functions are an extension to PSS and SS conditions from the Cinco-Ley’s original work. These equations are used to regenerate JD type curves of a finite-conductivity fractured well under pseudo-steady or steady state conditions. A comparison of the JD type curves of SS versus PSS is also presented. The maximum JD value, for fully penetrated infinite conductivity fractured well was 4/PI for SS versus 6/PI for the same case under PSS.
These productivity equations are also used to understand more post-fracturing production performance and to push the limits in hydraulic fracturing by injecting very large volumes of proppant of very large retained permeability. The paper will present the production results of the evolution of this hydraulic fracturing technique in these turbidite formations in Russia. It will be shown how the dimensionless productivity indices have been improving as the proppant volume per foot and proppant size has been increased. Statistics has shown how productivity index JD has increased from 0.3 to 0.55 when proppant concentration is increased from 4 tons/meter to 8 tons/meter. Definitely, pushing the fracturing limits in Russia has had a great impact on the production increase on these turbidite formations.
Optimization of PDC Drill Bit Performance Utilizing High-Speed, Real-Time Downhole Data Acquired Under a Cooperative Research and Development Agreement
Authors: Roberts T. S. , Schen A. E. , Wise J. L. 
Published: December 2007

Abstract
PDC drill bit performance has been greatly improved over the past three decades by innovations in bit design and how these designs are applied. The next leap forward is most likely to come from using high-speed, real-time downhole data to optimize the performance of these sophisticated bits on an application-by-application basis. By effectively managing conditions of lateral, axial and torsional acceleration, damage to cutting structures can be minimized for improved penetration rates. Avoiding these damaging vibrations is essential to increasing bit durability and improving overall drilling economics.
This paper describes one set of independent drilling optimization results obtained as part of a series of controlled demonstrations of PDC bits. Sandia National Laboratories on behalf of the U. S. Department of Energy (DOE) managed this work. The effort was organized as a Cooperative Research and Development Agreement (CRADA) established between Sandia and four bit manufacturers with DOE funding and in-kind contributions by the industry partners. The goal of this CRADA was to demonstrate drag bit performance in formations with degrees of hardness typical of those encountered while drilling geothermal wells.
The test results indicate that the surface weight-on-bit (WOB), revolutions per minute (RPM) and torque readings traditionally used to guide adjustments in the drilling parameters do not always provide the true picture of what is really taking place at the bit. Instead, a holistic approach combining traditional methods of optimization together with high-speed, real-time data enables far better decisions for improving bit performance and avoiding damaging situations that may have otherwise gone unnoticed.
New Bit Design, Cutter Technology Extend PDC Applications to Hard Rock Drilling
Authors: Clayton Robert , Chen Shilin , Lefort Guy 
Published: December 2007

Abstract
An advanced series of PDC drill bits incorporating a new highly abrasion-resistant PDC cutter has extended effective PDC bit application to hard rock drilling. In direct offset comparisons, the advanced series of PDC bits fitted with the new cutters delivered significant increases in footage drilled and rate of penetration.
To achieve an optimum match in drilling efficiency and bit life to lower costs and mitigate risk in hard rock environments, the series is designed using a combination of advanced modeling capabilities and sophisticated analytical tools. These tools allow the designs to be "customized" for specific applications, optimizing cutting efficiency and durability according to specific rock properties and drilling parameters. A transitional drilling model simulation allows evaluation of how cutting forces are affected during transitional drilling, common in "hard rock" environments. The bit design is globally balanced to optimize axial, lateral, and torsional forces, and can be modified by adjusting features such as profile shape, cutter rake angles, impact arrestors, and cutter type, to optimize bit performance when drilling in hard and transitional environments.
In addition, recognition of a third dimension of PDC performance – Thermal Mechanical Integrity (TMI) -- has lead to development of a new PDC cutter that provides 13.5 times the abrasion resistance of the industry standard, without sacrificing impact resistance. This improved understanding of PDC cutter failure provides a different way of looking at the traditional characteristics of abrasion and impact, enabling cutter durability to be optimized in both abrasive and hard, inter-bedded formations.
The paper discusses the science behind the advanced series of bits, including the impact of TMI on cutter performance. New laboratory capabilities and testing results are described, and actual field case histories presented to demonstrate performance improvements of these PDC bits in hard rock applications.
New Platform Rigs: Design and Construction
Authors: Nichols J. , Emans M. , Witton D. 
Published: December 2007

Abstract
There have been a number of dry tree developments over the past 5 years where new build drilling facilities have been designed and constructed as an integral part of the overall platform.
Each project has approached the specification, design and integration of the rig using different contractual arrangements. For example, the stage at which the drilling design team, the equipment suppliers, the fabricator and the drilling contractor become involved has varied widely between projects.
The degree of success of these integrated drilling facilities projects, both in terms of the rig being delivered on time and within budget, and also then operating as intended, has at best been variable.
The paper will describe the approach taken for the Benguela Belize project that started detailed design in February 2003. The fully mechanised 4,600hp rig is currently being commissioned in Houston and will sail away in February 2005 following the completion of onshore commissioning and acceptance.
The paper will cover how the project has been set up, including the development of an appropriate safety culture, the detailed design, fabrication, onshore commissioning and the training of the senior drill crew members prior to sail away.
The lessons learned from designing an appropriately specified rig and integrating the rig systems with the topsides contractor throughout the design will be discussed.
Understanding Torque and Drag: Best Practices and Lessons Learnt from the Captain Field's Extended Reach Wells
Authors: Rae G. , Lesso W. G. , Sapijanskas M. 
Published: December 2007

Abstract
This paper describes how torque and drag (T&D) analysis was used to successfully drill extended reach (ERD) wells in the Captain field in the North Sea. The issues and best practices associated with using this basic real-time drilling technique, particularly on Captain subsea development wells drilled from 2000 to 2003, are explained. The paper also explains the tactics used in overcoming issues such as how far could we drill and the associated risk. The applicability of available T&D reduction technologies and why many of them were eliminated as possible solutions reinforced the criticality of good T&D analysis on this project.
The Captain subsea wells have the highest aspect ratio (unwrapped displacement [UD] / true vertical depth [TVD]) ever for development wells drilled and completed from a floating vessel. Although the wells are short in displacement for ERD wells, the shallow nature of the reservoir requires the application of T&D analysis, which has been at the core of good ERD drilling principles and practices for some time.
This paper outlines what T&D analysis is and why it is important. The design of the bottomhole assembly (BHA) and drilling string, drilling string buckling, friction factor (FF) analysis, casing sanding considerations, trajectory design, and wellbore tortuosity all must be considered in applying this basic technique to field operations. Other issues such as why it is often misunderstood or badly applied, the importance of calibration with offset data, and conditions that effect FF determination are explained.