bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permafrost Freeze-Back Pressure Behavior
Authors: Goodman Malcolm A. , Wood Donald B. 
Published: December 2007

Drilling and production in the Arctic will thaw permafrost. At Prudhoe Bay on Alaska's North Slope the permafrost. At Prudhoe Bay on Alaska's North Slope the permafrost is nearly 2,000 ft thick. If thawed permafrost permafrost is nearly 2,000 ft thick. If thawed permafrost is allowed to freeze back, significant collapse loads near the bottom of the permafrost will be generated that must be considered in casing design. The loading mechanism is associated with the phase-change expansion of pore water in the thawed permafrost. The magnitude of the pressure buildup depends on the mechanical response of the frozen permafrost.
This article describes the formulation of an analytical freeze-back model and its correlation with freeze-back field-test data from Prudhoe Bay. As such, it is a condensed version of a paper in which the analytical model was formally developed. The model and field test yield the following conclusions.The 13 3/8-in., 72-lb, N-80 casing used in the field test and commonly used at Prudhoe Bay can safely withstand the maximum freeze-back pressures.For freeze-back from large thaw radii (50 ft of production thaw), the maximum pressure is not significantly production thaw), the maximum pressure is not significantly greater than that for freeze-back from small radii (3 ft of drilling thaw).The maximum freeze-back pressure depends on the elastic and yield properties of permafrost, but is most sensitive to the Young's modulus of frozen permafrost.Based on laboratory studies and supported by the field-test data, the creep or viscoelastic behavior of permafrost subject to freeze-back is negligible compared permafrost subject to freeze-back is negligible compared with the purely elastic and yield behavior.To limit the freeze-back pressure, the model is useful in the design of methods to limit the amount of initial thaw or to limit the extent of freeze-back.

The Freeze-Back Model
At each depth, the permafrost is initially thawed to a radius rb and, after refreezing for some time, is frozen back to radius ra. These two radii are input information to the model and serve to determine the amount of phasechange expansion at each instant in time. At the phasechange expansion at each instant in time. At the beginnig of freeze-back, the thawed permafrost is nearly saturated because of vertical drainage, water influx from drilling fluids, or compaction of the soil structure.
The freeze-back process occurs in three stages: relief of effective stress, elastic behavior, and elastic-yield behavior (see Fig. 1). In the first stage, as the pore water freezes, the ice either expands into the fluid-filled pores, increasing the porosity, and at the same time compressing the pore water, or expands locally, causing lens formation.
P. 949
Pore-Scale Modeling of Wettability Effects and Their Influence on Oil Recovery
Authors: Dixit A. B. , McDougall S. R. , Sorbie K. S. , Buckley J. S. 
Published: December 2007

SummaryThe wettability of a crude oil/brine/rock system influences both the form of petrophysical parameters (e.g., Pc and krw/kro) and the structure and distribution of remaining oil after secondary recovery. This latter issue is of central importance for improved oil recovery since it represents the "target" oil for any IOR process. In the present study, we have developed a three-dimensional network model to derive capillary pressure curves from nonuniformly wetted (mixed and fractionally wet) systems. The model initially considers primary drainage and the aging process leading to wettability alterations. This is then followed by simulations of spontaneous water imbibition, forced water drive, spontaneous oil imbibition and forced oil drive—i.e., we consider a complete flooding sequence characteristic of wettability experiments. The model takes into account many pore level flow phenomena such as film flow along wetting phase clusters, trapping of wetting and nonwetting phases by snapoff and bypassing. We also consider realistic variations in advancing and receding contact angles. There is a discussion of the effects of additional parameters such as the fraction of oil-wet pores, mean coordination number and pore size distribution upon fractionally and mixed wet capillary pressure curves. Moreover, we calculate Amott oil and water indices using the simulated curves. Results indicate that oil recovery via water imbibition in weakly water-wet cores can often exceed that obtained from strongly water-wet samples. Such an effect has been observed experimentally in the past. The basic physics governing this enhancement in spontaneous water imbibition can be explained using the concept of a capillarity surface. Based on these theoretical calculations, we propose a general "regime based" theory of wettability classification and analysis. We classify a range of experimentally observed and apparently inconsistent waterflood recovery trends into various regimes, depending upon the structure of the underlying oil- and water-wet pore clusters and the distribution of contact angles. Using this approach, numerous published experimental Amott indices and waterflood data from a variety of core/crude oil/brine systems are analyzed.
Comparisons of Cloud Point Measurement and Paraffin Prediction Methods
Authors: Monger-McClure T. G. , Tackett J. E. , Merrill L. S. 
Published: December 2007

Summary
The performance and costs of deepwater developments can be compromised if paraffin deposition occurs in a subsea production system. Given the desirability of accurate cloud point measurement and paraffin prediction methods, and the consensus that available capabilities did not satisfy normal design-level confi- dence, DeepStar undertook an evaluation process. The primary goal was to use field experience (1) to devise guidelines for obtaining and using measured cloud points, and (2) to "ground truth" the various paraffin thermodynamic and deposition models in use within the industry.
Cloud point measurement studies showed that under preferred operating conditions, cloud points by each of four methods agreed with the average value of all methods within 3°F. The reproducibility for duplicate field samples run by the same method was about 5°F. When very slow cooling rates were not possible, an approximate supercooling correction in °F of 2 times the cooling rate in °F/min was determined. A five-component cloud point standard showed promise for method evaluation. A definite advantage was found to using more than one cloud point method for a given sample because wax-detection sensitivity was method- and crude-oil-dependent. There was good agreement between measured stock-tank oil (STO) cloud points and the highest temperature at which wax buildup was detected in the field.
Results for 10 paraffin thermodynamic models indicated several available models provided useful cloud point forecasts. A representative fluid sample was required to obtain data input for these models, including quantitative n-paraffin analysis using high-temperature gas chromatography. Comparisons of cloud point results for STO versus live oil suggested that the hotter (more conservative) STO predictions and measurements more closely approximated the fifield paraffin deposition experience.
Six paraffin deposition models correctly identified that wax would deposit and which wellbore had the higher buildup rate. However, predicted wax thicknesses and patterns of paraffin deposition varied widely, and could not be judged quantitatively using available field data. Overall, predicted maximum depths of paraffin deposition showed poor agreement with field observations.
Good field data for evaluating cloud point measurement and paraffin prediction methods were difficult to obtain, and additional work to field-validate paraffin deposition know-how is warranted.
Initiatives on Mercury
Authors: Pongsiri Nutavoot 
Published: December 2007

Summary
Mercury has been known to be a trace contaminant in natural gas and condensate produced from Unocal Thailand's operations in the Gulf of Thailand since 1985. It has been detected in well streams, produced formation water, and also in solid waste. Mercury is recovered from process vessels, wellhead chokes, piping, and storage tanks. Almost all of the mercury found in natural gas and produced formation water is in elemental form, but in condensate, mercury is mostly in the colloidal form. Unocal Thailand has taken various proactive steps to minimize and limit both people's exposure to mercury and any impact on the environment, in full compliance with applicable laws and regulations. An example of environmentally sound treatment to dispose of mercury- contaminated solid waste is the deep-well injection technique. Another successful in-house developed technology, currently applied to the treatment of discharge water containing trace mercury, is a system using both gravitational separation and chemical flocculation techniques.
Large-Scale Two-Dimensional Imaging of Wettability Effects on Fluid Movement and Oil Recovery in Fractured Chalk
Authors: Graue Arne , Viksund B. G. , Baldwin B. A. , Spinler E. A. 
Published: December 2007

Summary
The effect of embedded fractures on the movement and recovery of hydrocarbon from larger outcrop chalk blocks at different wettabilities has been measured in the laboratory. Two-dimensional (2D) nuclear tracer imaging was used to produce in situ fluid saturation distributions during oil production. Emphasis was on determining the oil recovery mechanisms by tracking the flow path of the advancing water. Two sequential waterfloods were performed on each of the three different blocks: first before fracturing, and then after fracturing. The same fracture network configuration was used for all three blocks, which were strongly water wet, moderately water wet, and near neutral wet. Waterflooding the unfractured blocks, at high initial water saturation, occurred with minimal water banking while waterflooding at low initial water saturation produced distinct water bank formation. Waterflooding of the fractured blocks showed that the "closed" fractures produced a significant effect on fluid movement in the strongly water wet block, but only minor effect for the moderately and near neutral wet blocks. The open fracture affected flow in all the blocks. Total oil recovery was higher in the strongly water-wet block than in the moderately water wet block with the lowest oil recovery observed in the near neutral wet block.
Water-Cut and Fractional-Flow Logs From Array-Induction Measurements
Authors: Ramakrishnan T. S. , Wilkinson D. J. 
Published: December 2007

Summary
Despite the importance of relative permeabilities in reservoir simulation, no information regarding them is available from current logs. In this paper, for the first time, we demonstrate a continuous log of multiphase flow properties. Mud filtrate invasion is usually regarded as a process that corrupts the true logs. In reality, the multiphase flow characteristics that influence filtrate flow also determine the subsequent reservoir performance. We propose the notion that invasion is an experiment, albeit uncontrolled, that may be used to invert for multiphase flow properties. Thus, in principle, inversion of array induction measurements in terms of the fractional flow curve is possible. The forward model for filtrate invasion is based on two-phase (aqueous and oleic), three-component (oil, water and salt) transport. Hysteretic behavior of relative permeability functions is included. The radial conductivity profiles calculated from the flow model are converted to induction logs using radial response functions. An algorithm for rapid calculations of the forward logs by combining the electromagnetic and flow models is developed. A nonlinear least squares method is used for parameter inversion from measurements. Additional data of near-wellbore resistivity, or logs obtained during drilling, may be included. Presentations for several output logs have been developed: a reserves estimate that partitions porosity into residual and movable saturations, initial water cut in the production stream, the fractional flow curve as a function of saturation, filtrate loss per unit depth, and a quality indicator. A field example of the processing, and its comparison with production data is also discussed.
Brent Field Reservoir Modeling: Laying the Foundations of a Brown Field Redevelopment
Authors: James S. J. 
Published: December 2007

Summary
The Brent Field was discovered in 1971. It is now a mature asset and, in order to increase oil and gas ultimate recovery, will commence depressurization in 1997. The redevelopment of the field has been underpinned by extensive static and dynamic modeling studies. Developments in geological computing and the numerical processing power of reservoir simulation platforms significantly improved the quality of the Brent Field static and dynamic models. The static models have been used for a range of studies including gas cap volumetrics and bypassed oil investigations. Their functionality provides significant scope for target sizing as a basis for selecting the appropriate reservoir access well technology.
Determination of Pressure-Transient and Productivity Data for Deviated Wells in Layered Reservoirs
Authors: Larsen Leif 
Published: December 2007

Summary
Analytical methods are presented to determine pressure-transient and productivity data for deviated wells in layered reservoirs. The computational methods, which are based on Laplace transforms, can be used to generate types curves for use in direct analyses of pressure-transient data and to determine the effective skin of such wells for use in productivity computations.
Horizontal Underbalanced Drilling of Gas Wells with Coiled Tubing
Authors: Cox R. J. , Li Jeff , Lupick G. S. 
Published: December 2007

AbstractCoiled tubing drilling technology is gaining popularity and momentum as a significant and reliable method of drilling horizontal underbalanced wells. It is quickly moving into new frontiers. To this point, most efforts in the Western Canadian Basin have been focused towards sweet oil reservoirs in the 900–1300 m true vertical depth (TVD) range, however there is an ever-increasing interest in deeper and gas-producing formations. Fig. 1 shows a composite vertical section of the horizontal or directional under-balanced wells drilled with coiled tubing in Canada, and also highlights the aforementioned trend towards oil over gas. Significant design challenges on both conventional and coiled tubing drilling operations are imposed when attempting to drill these formations underbalanced.Coiled tubing is an ideal technology for underbalanced drilling due to its absence of drillstring connections resulting in continuous underbalanced capabilities. This also makes it suitable for sour well drilling and live well intervention without the risk of surface releases of reservoir gas. Through the use of pressure deployment procedures it is possible to complete the drilling operation without need to kill the well, thereby maintaining under-balanced conditions right through to the production phase. The use of coiled tubing also provides a means for continuous wireline communication with downhole steering, logging and pressure recording devices.Coiled tubing drilling rigs currently exist in several different forms and setups, but generally consist of a drilling coil, injector to feed the tubing into or out of the well, (blowout prevention) (BOP) system for well control and return fluid path, and a control cab and power unit. The coiled tubing drilling equipment used to drill the case studies presented later in this paper consisted of either 60.3 or 73.0 mm coiled tubing and injector with a hydraulic power unit with control cabin and accumulator. A coiled tubing hybrid mast unit and substructure complete with V-door and catwalk was used. Pumping equipment included a fluid pumper capable of liquid rates of 0.10–1.5 m3/min, nitrogen pumper capable of 10–120 m3/min, and a nitrogen bulk storage unit of 50,000 m3 capacity. When drilling sour gas formations, a chemical injection pump for corrosion inhibition is typically used.
Analysis of Riserless Drilling and Well-Control Hydraulics
Authors: Choe Jonggeun 
Published: December 2007

Summary
Riserless drilling is an unconventional technique using a relatively small diameter pipe as a mud return line from the sea floor instead of a large diameter marine riser. The schemes were developed in the late 1960s to reduce wear on blowout presenters and to make drill pipe re-entry easier by balancing internal and external subsea well pressures. However, these concepts were not implemented at that time because water depths were shallow, and technology was not available. In the Gulf of Mexico, exploration attempts have been made in areas which have more than 7,000 ft water depth. A conventional large diameter riser requires a vessel with huge weight and space capacities, large mud volumes to circulate through a riser, and numerous casing points because of the relatively low separation between the formation pore pressure and fracture pressure, especially in the Gulf of Mexico. These problems may be reduced significantly by applying riserless drilling. Therefore, riserless drilling is one of the attractive alternatives for economically exploring oil fields in deep water. The concept of riserless drilling currently has many unsolved problems such as system configuration and well control. This paper presents basic concepts of riserless drilling and a brief review of problems associated with conventional marine riser drilling for deep water applications. The paper also presents hydraulics and well control considerations for riserless drilling with comparison to conventional riser drilling.
Objectives of Engineering Education
Authors: Houston W.V. 
Published: December 2007

Introduction
In recent years it has become customary to regard a university education as important for an engineer, but this has not always been the case. Engineering work has been done for thousands of years, and only for some 150 of them has it had any formal connection with universities. For several centuries the universities of Europe and the engineers of Europe had no connection with each other. Probably there are still a few practical men who look with considerable suspicion on a university graduate as he comes to an engineering job. And there are probably also a few university people who regard engineering departments as interlopers.
Engineering has two aspects and two traditions. One is the tradition of the master craftsman. It is a little hard to trace, historically, for its representatives rarely wrote books. They were builders and doers, rather than thinkers and talkers. But they did develop a strong sense of professional responsibility. Mistakes could not be tolerated. The art was handed down from master to apprentice and the road to mastery involved hard work. Experience was its measure.
The other tradition is a scientific and mathematical one. It is represented in ancient times by Plato's Academy and by the School at Alexandria. At the time of the Renaissance it comes to light in the faculties of philosophy in the universities and in the mathematicians attached to various courts. Today it is represented by the scientific and mathematical aspects of work in the universities. The men of this tradition were often, and are sometimes today, dismissed as merely theoretical, or impractical, by those who have had little understanding of the matters in which they find an absorbing interest. But from this group have come most of the strikingly new ideas of engineering.
And when men from this group have been able to establish close and sympathetic relationships with men of experience, engineering has leaped forward with great bounds.

Demands Upon the Engineer
The expansion of engineering in recent years has put severe demands on all sides of an engineer's proficiency.
Steam-Drive Correlation and Prediction
Authors: Myhill N.A. , Stegemeier G.L. 
Published: December 2007

Introduction
During the past 15 years, steam-injection processes have become an importantmeans of exploiting heavy oil reserves. Traditionally, these processes havebeen classified as either steam soaks or steam drives. With combinations, suchas presoaking drive wells and partially driving steam soaks, the distinction isnot always applocable. Furthermore, our experience auggests that oil/steamratios from most mature processes converge to a calue determined only byreservoir and steam properties and time.
To date, the steam-soak process has proven the more attractive, partlybecause the immediate response allows an early evaluation of a reservoir andpartly because oil rates from initial soak cycles tend to be better than latercycles. Successful steam soaks are limited to reservoirs where natural recoverymechanisms (gravity drainage, pressure depeletion, and solition gas drive)areineffective because of the low oil mobilities.
Successful steam drives requiregood conformance,a means ofstarting the process because high oil saturations can limit injectivityseverely and prevent effective initial reservoir heating, andsustainedhigh injectivity throughout the process life. Unlike steam soaks, steam drivesdo not respond until built-up oil banks and heat reach the production wells.
Because peak production rates may not be observed for several years after thestart of injection, piloting is expensive and expansion to full scale issoemwhat hazardous. For those reasons, screening methods that predict ultimateoil/steam ratio are useful in planning new projects or in modifying existingones.
In the past, steam injection has been applied to a wide spectrum ofreservoir conditions, many of which have proven unsuitable. In retrospect, wecan explain the varied response withh a simple mathematical model thatincorporates reservoir and steam properties in the prediction. This paperdescribes the model and compares prediction from it with laboratory and fieldresults.
Reproducible Wettability Alteration of Low-Permeable Outcrop Chalk
Authors: Graue A. , Viksund B. G. , Baldwin B. A. 
Published: December 2007

Summary
A total of 41 chalk core plugs, cut with the same orientation from large blocks of outcrop chalk, have been aged in crude oil at 90 °C for different time periods, in duplicate sets. Different filtration techniques, filtration temperatures and injection temperatures were used for the crude oil. Oil recovery by spontaneous, room temperature imbibition, followed by a waterflood, was used to produce the Amott water index for cores containing aged crude oil and for cores where the aged crude oil was exchanged by fresh crude oil or decane.
The main objective was to establish a reproducible method for altering the wettability of outcrop chalk. A secondary objective was to determine mechanisms involved and the stability of the wettability change.
The aging technique was found to be reproducible and could alter wettability in Rordal chalk selectively, from strongly water-wet to nearly neutral-wet. A consistent change in wettability towards a less water-wet state with increased aging time was observed.