bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lessons Learned on Gulf of Mexico Gas Wells Drilled With OBM and Completed With Heavy Brine
Authors: McBee Jim , Evans Brian , Umbher Kevin 
Published: December 2007

AbstractDrilling gas wells with oil-based mud (OBM) or synthetic-based mud (SBM) has been proven to create producing wells with very high completion efficiencies. This property makes OBM use very attractive, even if the reservoir conditions are not the traditional hot, high-pressure, harsh variety usually associated with oil mud usage.While oil-based or synthetic-based drilling fluids do an excellent job of creating a nonreactive, stable wellbore, they contain additives that can lead to inflow problems if not properly anticipated and treated early in the completion phase. The well can experience drastic or complete resistance to inflow when high-density completion brine, used to control well pressure, is emulsified in situ by OBM filtrate in the flushed zone around the wellbore. Routine post-perforating acid treatments may not have the desired result due to the nature of OBM emulsifiers and wetting agents. Another problem arises when whole mud (oil-or synthetic-based) is lost during drilling and must be addressed before commencing production.This paper examines two gas well completions in the Gulf of Mexico in which oil-based muds were used for drilling and high-density completion brines were used for post-perforating well control and completion operations. These wells would not flow when opened. Special remedial treatments were required to condition the reservoir, initiate well flow and facilitate drilling, completion and stimulation fluid recovery. The well treatments involved using chemicals to break the downhole emulsion, water-wet the formation and reduce surface tension of aqueous fluids lost to reservoir during drilling and completion. The need for these post-completion treatments has led to changes in well completion procedures to prevent future fluid incompatibilities and formation damage.Treatment results were notable, with both wells going from zero production to over 7 MMcf/D and an increase in both shut-in and flowing tubing pressures.
Decision Making in the Oil and Gas Industry: From Blissful Ignorance to Uncertainty-Induced Confusion
Authors: Eric Bickel J. , Bratvold Reidar B. 
Published: December 2007

Abstract
The battle against deterministic forecasts and financial valuations in the oil and gas industry appears to have been won, as evidenced by the plethora of papers, conference sessions, and forums focused on uncertainty quantification or profit prediction. Yet, decision makers are still not sure what they should do. Rather than basing important decisions on a single number, they now find themselves buried under a mountain of probability distributions. Uncertainty quantification seems to have confused more than it has enlightened.
In this paper, we present the findings of a survey of oil and gas professionals that addressed the following two questions: To what degree has uncertainty quantification improved in the oil and gas industry over the last five years? Has this improvement translated into improved decision making?
Uncertainty quantification is not an end unto itself; removing or even reducing uncertainty is not the goal. Rather, the objective is to make a good decision, which in many cases requires the assessment of the relevant uncertainties. The oil and gas industry seems to have lost sight of this goal in its good-faith effort to provide decision makers with a richer understanding of the possible outcomes flowing from major decisions. The industry implicitly believes that uncertainty is reduced simply by modeling it and that making good decisions merely requires more information.
To counter this, we present a decision-focused uncertainty quantification framework, which we hope, in combination with our survey results, will aid in the innovation of better decision-making tools and methodologies.
Elevated Activity Levels Driving Technology Development at Record Pace:Barnett Shale-North Texas
Authors: Jennings Drew , Felderhoff Floyd , Isbell Matt , Kramer Mark , Pierce Eddie , Roberts Geoff , Paugh Wesley , Janwadkar Sandeep 
Published: December 2007

Abstract
Increased demand for natural gas and the resulting long-term price stability has caused operators to apply new, high-end technology to accelerate development in the Barnett Shale field of north Texas. Expanding drilling schedules on shortening timelines have resulted in the systematic advancement of technology to keep pace with the increased pressure to cut drilling costs and reduce days to production.
One operator and its service providers recognized the potential to replace established technology and drive down costs drilling horizontal boreholes. A team-based approach focused on discrete well intervals to identify issues, analyze problems, and explore solutions to improve overall performance. In the northern part of the field, the introduction of polycrystalline diamond compact (PDC) bits, modifications to the drillstring, and new operational practices in the vertical hole section, previously dominated by roller cone bits, reduced drilling time by 62% over the interval. To the south, a new approach to critical failure analysis was utilized to double the drilling performance through the lithologically challenging curve section with roller cone bits. The rate of penetration (ROP) and footage advancements achieved in both scenarios have changed the drilling landscape in north Texas and made intense drilling schedules significantly more manageable.
In a six-month period, the 8 3/4-in. vertical section was drilled in just one PDC bit run on 23 out of 30 wells in the northern area, cutting interval costs by $150,000 and drilling time by 62%. To the south, new roller cone technology outperformed 90% of the previous runs, increasing ROP by 84% to 18.8 ft/hr from 10.2 ft/hr, saving the operator a total of $1.68 million over 15 wells.
The paper will outline drilling performance improvements in terms of footage, ROP, and the operating parameters/systems required to achieve the dual performance step change.
Permeability and Saturation Evaluation in Deepwater Turbidite Utilizing Logging-While-Drilling Low-Gradient Magnetic Resonance
Authors: Turco Kevin , Brenneke Jim , Jebutu Segun , Kirkwood Andrew , Thern Holger , Chemali Roland , Kruspe Thomas 
Published: December 2007

Abstract
The economic recovery of hydrocarbons from deepwater reservoirs continues to be a major challenge facing the exploration and production industry, not just contending with the multitude of market uncertainties, but also, more importantly, reservoir deliverability uncertainties associated with deeply deposited pay targets. One large field subject of this study is such, deposited in stacked Pliocene sandstones. These are high net-to-gross, with predominant very finegrained sands. The efficient sweep of the oil in place requires a detailed understanding of the network of the reservoir pore structure, and the permeability distribution and capillary bound fluids.
To better understand and characterize the permeability and to help quantify the potential reserves, a novel low gradient magnetic resonance LWD tool for application on conventional drilling assemblies was used. This is a major departure from the more conventional techniques which use high gradient magnetic resonance on post-drilled wireline platforms. Advantages of an LWD approach are twofold; the wellbore is in good condition at the time of drilling, yielding high quality data, and the gain in rig time is significant.
The high quality magnetic resonance dataset acquired was confirmed by overlaying with stationary measurements. The data was integrated with offset core data to normalize permeability models and saturation functions. LWD density images acquired during drilling were also used to provide detailed visualizations of the internal laminations of the turbidites, as well as a reservoir structural setting. Formation pressures and mobility measurements acquired during drilling were also integrated in the normalization process to characterize the deliverability of the sands.
The resulting permeability model was used to study and redesign future development in the field. The saturation results also provide an improvement over the previous resistivity-only based saturation values, which were pessimistic due to the fine-grained structure of the reservoir sands.
Modeling of Expandable Slotted Tubulars
Authors: Li Zifeng , Yao Dongping , Samuel G. Robello 
Published: December 2007

Abstract
Advanced technologies are implemented for successful completion of wells and have become paramount objective especially in high-risk, high-cost environments, such as ultradeep water extended reach wells. Challenges are associated not only with complex well architecture but also completing the wells successfully using slotted tubulars, slotted liners and etc. Expandable slotted tubulars have been found to improve well production, reduce sand production and thereby reduce well costs compared with conventional approaches to sand control. While performing these completion operations the maximum running hook loads and static drag encountered during pre and post expansion process are indispensable for making appropriate well-completion decisions. Comparatively little research or modeling has been done to estimate these operating parameters. Traditionally, operating parameters such as torque and drag are estimated using the traditional torque and drag calculations with adjusted friction factors. This will result in under estimation of the values and pose problem in successfully completing the zone. Unduly conservative design or under estimation may pose poor result and lead to undesirable increase in the well cost and may be significant in challenging wells. To avoid this, a simple mathematical model has been developed and presented in this paper. Several simulations were carried out with synthetic as well actual data and have been found that the model prediction is very good as compared to the actual data. This paper documents the comparison between the predicted mathematical simulation results with the actual data.
Development and Application of New Computational Procedures for Modeling Miscible Gas Injection in Fractured Reservoirs
Authors: Hui Mun-Hong , Gong Bin , Karimi-Fard Mohammad , Durlofsky Louis J. 
Published: December 2007

Abstract
Detailed geological characterizations of naturally fractured reservoirs are commonly in the form of discrete fracture models, in which each fracture is defined explicitly. The efficient simulation of flow processes in such models poses a great challenge. In recent work, we developed systematic procedures for upscaling discrete fracture models to coarse-scale continuum descriptions referred to as multiple subregion (MSR) models. In this work, we extend these formulations to generate full dual-porosity, dual-permeability MSR models and additionally introduce the use of global single-phase flow information in the computation of the upscaled interblock transmissibilities required by the method. The resulting models are used for waterflood simulations and, more interestingly, for compositional simulations of first-contact-miscible gas injection. In a series of flow simulations involving both connected and disconnected fracture systems, it is shown that the MSR method provides results of reasonable accuracy, relative to the reference DFM solutions, for both oil-water and compositional oil-gas simulations with six pseudocomponents. Computational speedups of order 1000 are achieved for the compositional models.
A Modeling Study of the Role of Selected Minerals in Enhancing CO2 Mineralization During CO2 Aquifer Storage
Authors: Thibeau S. , Nghiem L. X. , Ohkuma H. 
Published: December 2007

Abstract
CO2 mineralization is a process whereby the CO2 that is injected into a geological formation dissolves into the formation water, reacts with the in situ minerals and ions, and precipitates as carbonate minerals. This process governs the long-term fate of the injected CO2 and ensures a safe storage once CO2 has been converted into minerals.
In a previous study involving the modelling of the long-term fate of CO2 in the Utsira aquifer storage, the authors observed that CO2 mineralization was not possible if mineral reactions were limited to Calcite and Dolomite precipitation and dissolution.
Indeed, to mineralize CO2, non carbonate minerals that are present in the formation have to: –dissolve in order to buffer the pH decrease resulting from the CO2 injection;–provide cations such as Ca2+, Mg2+, Fe2+ to the formation water;–not release bicarbonate (HCO3−) to the formation water.
Then the released cations react with HCO3− resulting from the dissolution of the injected CO2 and precipitate new carbonate minerals.
In this study, the CO2 mineralization process is modelled, taking into consideration various possible reactive pathways.
In the first step, the different reactive pathways are investigated in terms of reactive potential, CO2 mineralization potential and consequences on the porous network.
In the second step, simulation of flow and dissolution of CO2 together with geochemical reactions is performed to examine the mineralization process in space and time for two different time scales:
– 1000 years with a finer grid to examine how chemistry interacts with the CO2 dissolution process; and – 18,000 years with a coarser scale to reach geochemical equilibrium in the aquifer.
This work shows that a limited amount of non-carbonate reactive minerals (for a given time scale) can contribute to the mineralization of CO2 that is significant for an industrial CO2 storage project. As such, the identification of the reactive pathways leading to CO2 mineralization is a key step to evaluate the long-term fate of the injected CO2 in a geological storage project.
Predicting Undulating Well Performance
Authors: Kamkom R. , Zhu D. , Bond A. 
Published: December 2007

Abstract
Undulating wells are one of the alternatives to horizontal wells in field developments for extremely low vertical permeability formations. Undulating wells offer higher reservoir exposure and they do not depend on vertical permeability as much as horizontal wells do. This makes undulating well trajectory sometimes more attractive than horizontal wells.
Although undulating wells have been used in the field, predicting and understanding well performance is still a challenge. In the past, we have presented an analytical model that uses a segmented vertical well model with a slanted skin factor to estimate undulating well performance. The analytical model works well under certain formation and well structure conditions. In this paper, we will present a more comprehensive model for undulating well performance. The model evaluates undulating well performance in a parallelepiped reservoir based on a line source solution. The well can be located anywhere in the reservoir. The result is also compared with the previously developed analytical model to identify the conditions that the analytical model can be applied.
Field examples are used in the paper to illustrate optimizing undulating well performance by the model. The Cosmopolitan Field, Cook Inlet Alaska, and the Oooguruk Field, North Slope Alaska, are planned for development with undulating horizontal wells. Both reservoirs are challenged with relatively low permeability, low kv/kh ratios and moderate viscosity oil. Undulating horizontal wells are needed to overcome these issues and deliver commercial production rates. The performance model developed in this study demonstrated the additional value of an undulating well over a conventional horizontal well, which provided a key support in well design and field development plan.
A Robust Steady-State Model for Flowing-Fluid Temperature in Complex Wells
Authors: Hasan A. R. , Kabir C. S. , Wang X. 
Published: December 2007

Abstract
This paper presents an analytic model for computing the wellbore-fluid-temperature profile for steady fluid flow. Although wells with constant-deviation angle can be handled with existing analytic models, complex well architectures demand rigorous treatment. For example, changing geothermal-temperature gradient and deepwater wells present significant challenges. Additionally, available analytic models rarely provide calculation methods for various required thermal parameters, such as the Joule-Thompson coefficient and fluid expansivity.
The approach taken in this study entails dividing the wellbore into many sections of uniform thermal properties and deviation angle. The governing differential equation is solved for each section, with fluid temperature from the prior section as the boundary condition. This piecewise approach makes the model versatile, allowing step-by-step calculation of fluid temperature for the entire wellbore. We present simple, thermodynamically sound approaches for estimating thermal parameters.
Good success is indicated when performance of the proposed model is compared with data from three wells; producing two-phase gas/oil mixture, single-phase oil, and single-phase gas. Sensitivity of the estimated fluid temperatures to various thermal properties is also examined using our model. Overall, the effects of Joule-Thompson coefficient and liquid expansivity are found to be significant.
An Iterative Ensemble Kalman Filter for Data Assimilation
Authors: Gaoming Li , Reynolds A. C. 
Published: December 2007

Abstract
The ensemble Kalman filter (EnKF) is a subject of intensive investigation for use as a reservoir management tool. For strongly nonlinear problems, however, EnKF can fail to achieve an acceptable data match at certain times in the assimilation process. Here, we provide iterative EnKF procedures to remedy this deficiency and explore the validity of these iterative methods compared to standard EnKF by considering two examples, one of which is pertains to a simple problem where the posterior probability density function has two modes. In both examples, we are able to obtain better data matches using iterative methods than with standard EnKF.
In Appendix A, we enumerate the assumptions that must hold in order to show that EnKF provides a correct sampling of the probability distribution for the random variables. This derivation calls into question the common derivation in which one adds the data to the original combined state vector of model parameters and dynamical variables. In fact, it appears that there is no assurance that this trick for turning a nonlinear problem into a linear problem results in a correct sampling of the pdf one wishes to sample. However, we show that augmenting the state vector with the data results in a correct procedure for sampling the pdf if at every data assimilation step, the predicted data vector is a linear function of the combined (unaugmented) state vector and the average predicted data vector is equal to the predicted data evaluated at the average of the predicted combined state vector. Without these assumptions, we know of no way to show EnKF samples correctly. For completeness, in Appendix C, we show that each ensemble member of model parameters obtained at each step of EnKF is a linear combination of the initial ensemble, which emphasizes the importance of obtaining a sufficiently large initial ensemble.
What Are Our Options for Sequestration of Atmospheric CO2—Some Thoughts
Authors: Gupta Subodh 
Published: December 2007

Abstract
Use of fossil fuel ever since the dawn of the industrial age has led to increased level of CO2 in the environment. Our world today is fueled mainly by fossil energy and it is unlikely that this dependence will significantly change in the near future. This coupled with the fact that majority of the developing world is at the beginning of the economic growth which is implicitly energy-intensive, the concentration of CO2 in atmosphere will only increase in the business-as-usual case.
Reduction in per capita CO2 emission both on account of minimizing explicit wastes and improving efficiencies will play a significant role in slowing down the build up of CO2. But to bring its concentration down and back to the preindustrial or comfortable levels, emphasis may have to shift to CO2 sequestration.
This paper discusses the role and potential of geological and biological sequestration approaches. Furthermore, for a longer time horizon it highlights the importance and practicality of a modified approach to bio-sequestration, where CO2 is captured and stored on surface by Carbonization of biomass through its conversion to charcoal. It highlights the fact that biosequestration can be very effective and practical but requires achievement of longer bio-storage duration which is achievable through conversion to charcoal. Also, combinations of various approaches including geological sequestration and efficiency improvement are essential to reverse the trend of increasing concentration of CO2 in the atmosphere in a short run.
Effective Matrix Acidizing in High-Temperature Environments
Authors: Aboud Ricardo , Smith Kern , Forero Leandro , Kalfayan Leonard 
Published: December 2007

AbstractWorld demand for energy is substantial and continues to grow. By 2020, it is expected that the world will need approximately 40% more energy than today, for a total of 300 million barrels of oil-equivalent energy every day. Meeting higher energy demands will require a portfolio of energy-generation options including but not limited to oil, natural gas, coal, nuclear, steam, hydro, biomass, solar and wind.New horizons are being explored. Wells are drilled in greater water depths. Drilling units are continually upgraded to target deeper hydrocarbon-bearing zones. Wellbore tubular metallurgy is continually upgraded. Drilling, completion and stimulation fluids are being developed for extreme temperature and pressure environments.As the preferred technology to enhance "oilfield" energy production, well stimulation has and will continue to have an important role in fulfilling the world's future energy needs. Well stimulation generally uses fluids to create or enlarge formation flow channels, thereby overcoming low permeability, as in "tight" formations, and formation damage, which can occur in any formation type. A common and very successful stimulation option, matrix acidizing, utilizes acids that react to remove mineral phases restricting flow. Depending on the formation and acid type, flow is increased by removing pore-plugging material; or by creating new or enlarged flow paths through the natural pore system of the rock. However, higher-temperature environments present a challenge to matrix acidizing effectiveness. High temperatures can negatively affect stimulation fluid properties and certain acid reactions. Thus, careful fluid choice and treatment designs are critical to successful high-temperature matrix acidizing.With proper fluid selection, design, and execution, matrix acidizing can be applied successfully to stimulate high-temperature oil & gas wells and geothermal wells. These types of wells have some common features, but they also have significant differences (e.g., completions, mineralogy, formation fluids and formation flow) that influence stimulation designs and fluid choices.This paper summarizes best practices for designing matrix acidizing treatments and choosing stimulation fluids for high-temperature oil & gas wells and geothermal wells. Included are case histories from Central America. Lessons learned about differences and commonalities between stimulation practices in these well types are also discussed.