bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved First-Motion Algorithm to Compute High-Resolution Sonic Log
Authors: Valero Henri-Pierre , Tejada Mauricio , Murray Doug 
Published: December 2007

Abstract
Estimation of formation slowness is of significant value for petrophysical and geomechanical applications. To do this, a source excites a signal in the borehole, which couples with, and propagates within, the formation prior to being recorded by receivers. Generally, sonic tools are composed of one or more transmitters and an array of receivers. A next generation sonic tool developed by Schlumberger is composed of 3 monopole and 2 dipole transmitters. The receiver array is composed of 13 receivers separated by 6 inches. Waveforms are digitized at the sensor with a dynamic range of 16 bits. Digitizing the waveform at the sensor will guarantee optimal data quality as the waveforms will not be corrupted by electronic noise or other undesirable effects. The general technique used to measure formation slowness is based on semblance processing which was first proposed 20 years ago. Semblance processing is robust and provides reliable results in most cases but its vertical resolution is linked to the length of the tool array. Practically, it means it is not possible to detect beds that are smaller than a tool's array length. Hence, it can be difficult to compare slowness logs with other datasets of much higher vertical resolutions.
In order to alleviate this problem, we propose an improved first motion algorithm to compute a high-resolution sonic log. The technique considers that the part of the waveform before and after the first break can be modeled as an AR process. The key parameters of this approach are the "model order", which describes the data and the part of the waveform to be modeled. In this paper we will show that the use of the Bayesian Information Criterion combined with the computation of the envelope of the signal will allow for an automatic computation that is suitable for wellsite operations. We will demonstrate that this first motion technique does not require any human intervention and in most cases provides a robust and reliable result. This algorithm will then be applied on real data and the high-resolution log obtained will be compared with other high vertical resolution measurements.

Introduction
Evaluation of formation slowness using sonic tools is important in oil exploration. This physical measurement allows geophysicists to calibrate their velocity models, and petrophysicists to obtain a porosity estimate of the reservoir. Measurement of the compressional and shear acoustic slownesses of the formation is usually made in open hole. The conventional method is to acquire monopole data, which is used to determine the compressional slowness. If the shear slowness is required, and if it is faster than the mud slowness, it can be obtained from monopole data with waveform processing. In slow formations dipole mode data may also be acquired to provide shear information and can provide redundancy for the monopole shear measurement in fast formations. These results are generally well established and reliable in most cases.
Maximizing Productivity in the Scoter Gas Condensate Field, UKCS: A Multidisciplinary Approach to Expandable Sand Screen Design and Subsea Installation
Authors: Al-Lamki Ali , Twycross Jean , Clarke Gillian 
Published: December 2007

Abstract
Expandable Sand Screens (ESS®) were deployed successfully in two gas-condensate subsea production wells on the Scoter field, in the UK sector of the North Sea in May 2003. The Shell UK operated 22/30a-S1 (Scoter P1) and 22/30a-S2 (Scoter P2) wells are near-vertical, drilled from the semi-submersible rig, Ocean Guardian, and penetrate the Forties sandstone. Well clean-up performance to the rig (June 2003) and first production to the Shearwater processing platform (December 2003) exceeded original expectations.
The success of the Scoter 4" ESS installation has been due, in part, to the multi-disciplinary approach taken by both Shell and Weatherford, from concept selection to after-action review. This paper details learnings on the extensive ESS design and execution including: Torque and drag analysis for screen running in and expansion to minimize damage.Determination of rig-heave effects on screen expansion from an Axial Compliant Expansion (ACE) tool.Use of long-term, synthetic core baking-tests (at temperature) to estimate the effect of completion-to-clean-up time on reservoir return permeability: initial production data showed no evidence of skin (no wellbore damage or screen plugging for both wells).Erosion and collapse modeling of the screens.Well clean-up and bean-up, including offshore petroleum engineering support.Sand control contingency planning (e.g. external gravel pack sand control design, including mud selection testing).Simplified completion including use of a Formation Isolation Valve (FIV)
This technical knowledge can be adopted elsewhere for future sand control applications, including: Any design and installation of ESS, especially from a semi-submersible rig.Any return permeability testing, especially to assess the effect of delayed clean-up on reservoir return permeability.Any clean-up of a gas-condensate ESS well.
Attic Oil
Authors: van der Poel C. , Killian J.W. 
Published: December 2007

Abstract
The area that can be swept by a natural water drive in a dipping reservoir above the structurally highest wells is investigated mathematically and with a parallel plate flow model. This swept attic area (above the structurally highest wells) is found to be a function of two parameters. The first parameter describes the relative influence of the viscous potential gradient or "drawdown" at the well tending to move such oil down from this attic space, and the buoyant force of gravity tending to keep the oil in the attic. The ultimate area that can he swept if production is continued to 100 per cent water-cut is a function of this parameter alone. The second parameter is a combination of water-cut and mobility ratio, and is a measure of the fraction of this ultimate swept area that is actually swept. The attic area swept can vary from zero or even slightly negative amounts, up to perhaps half the square of the well spacing for very favorable circumstances. (There is no theoretical limit on the ultimate area swept as the production rate, for example, is increased. But extremely large ultimate swept areas are approached so slowly that they are not closely realized at even quite high water-cuts.) At sufficiently unfavorable mobility ratio and high production rate, fingering will occur. Fingering reduces the swept area at low water-cuts, but has little effect at high water-cuts. Charts given in the report enable rapid calculation of swept areas for specific field cases, and a criterion is given for fingering.
The complete flow pattern is determined theoretically for the 100 per cent water-cut case. The computed interface shapes and areas swept are in good agreement with the model results. The production history for unit mobility ratio and negligible buoyancy also is determined theoretically, which serves as a guide in correlation, and agrees well with the experimental (model) data.

Introduction
The determination of the amount of oil recoverable updip of the structurally highest wells in a strong water-drive dipping reservoir is particularly important for salt-dome fields, such as at Weeks Island, where it often is not feasible or desirable to complete wells right up against the salt dome.
A Probabilistic Analysis of the Economics of Oil Recovery From the Athabasca Tar Sands
Authors: Iskander Fadel F. , Ikoku Chi U. 
Published: December 2007

ABSTRACT
A general-purpose probabilistic economic evaluation model for petroleum investment ventures has been developed. The model’s operation is demonstrated by considering an actual field in Alberta, where an economic evaluation of the feasibility of producing the Athabasca tar sands is conducted. An oil recovery method (COFCAW) is applied, and necessary input data are selected. Other oil recovery methods may be evaluated by modifying the input data.
The model allows the use of five continuous input probability distributions as well as a discrete input distribution. Input for the continuous distributions is entered as a three point estimate (low, medium, and high), whereas input for the discrete distribution is entered as a number of values and their respective cumulative probabilities of occurrence. The maximum number of values allowed is nine.
The model calculates possible production rates which are directly dependent on the calculated recoverable reserves. The production rates are used to calculate total revenue; this is followed by calculating direct and indirect cost items, taxable income, taxes, earnings after tax, non tax deductible items, cash outflows, and net cash flows. These net cash flows are used to calculate three profitability measures: the discounted cash flow rate of return, a modified rate of return, and the net present value.
The results obtained are summarized as follows: the discounted cash flow rate of return, the modified rate of return, and net present value calculated had average values of 35%, 30%, and $10.5 million, respectively.
A sensitivity study on the input variables was conducted to identify the critical variables whose input values have an impact on the results of the model. Among the most critical variables are well operating expenses, inflation rate on the operating expenses, bitumen selling price, and inflation rate on that price. It is also observed that the modified rate of return is the least sensitive to input data variations of all profitability measures considered.
Seismic-While-Drilling Using a Swept Impulse Source
Authors: Kolle J. J. , Theimer K. 
Published: December 2007

Abstract
This paper describes a prototype swept impulse hydraulic tool capable of generating a broadband seismic signal at the bit while drilling. The source was designed to overcome the limitations of drill bit seismic services by allowing operations with PDC bits in inclined wells and in soft formations. Operating principles, seismic processing techniques and results of a field demonstration of seismic profiling while drilling in a shallow well are described. Downhole tests of a prototype swept impulse tool were conducted in a deviated well while drilling with a PDC bit at depths of 2000 to 2500 feet. These tests represent the first demonstration of reverse vertical seismic profiling while drilling with a PDC bit or while drilling in an inclined well. The swept impulse seismic source generated a broadband, high-intensity compression wave signal that can be used for high resolution seismic profiling and look-ahead imaging while drilling. Velocity measurement accuracy is comparable to checkshot/VSP or sonic log and the information is available in real time with no interruption of conventional drilling operations.
Measurement and Analysis of Induced Torsion in Helically Buckled Tubing
Authors: Zdvizhkov A. , Miska S. , Mitchell R. 
Published: December 2007

Abstract
In the original publication on helical buckling by Lubinski, Althouse and Logan (1962) it was assumed that no torsion can be developed in buckled tubular string (Lubinski-Woods problem) if there is no casing-to-tubing friction and tubing remains in elastic range of bending.
The recent theoretical work by Mitchell1 (2003) presented the large displacement analysis of helically buckled slender beam and predicted, that shear force and twisting moment are induced in helically buckled pipe without externally applied torque.
In short, there is an induced left-hand torsion in tubing buckled into right-hand helix that is surprisingly large and in some cases may approach or exceed the make-up torque values for connections.
For study of this phenomenon an experimental facility was setup at The University of Tulsa, depicting straight horizontal wellbore with the inner steel tubing 0.50" (12.7mm) OD and outer acrylic tube 1.90" (48.3mm) ID representing drillstring and wellbore respectively.
For precise measurement of pure torsion in the tubing, the strain gages, arranged into the full torsion bridge configuration were employed.
The experiments were performed with "bottom end" of the steel tubing held stationary and axial buckling force applied from the "top end".
The end conditions for the tubing were represented by clamped and pinned connections.
It was observed that torsional equilibrium in the tubing is disturbed as soon as buckling force is applied with further increase in torsion as shape of the tubing is transforming from sinusoidal into helical.
Upon the tubing reaching full helical shape, the internal torsion continues to increase with increase of axial buckling force in the manner predicted theoretically.
The results of this study are important for practical design and analysis of drillstrings and completion tubing.
Versatile Expandables Technology for Casing Repair
Authors: Storaune Anders , Winters Warren J. 
Published: December 2007

Abstract
Three installations of a new expandable casing patch in 5 ½" production casing are described. During field trials, 2,530 ft and 8,380 ft patches were installed in Wyoming and Texas gas wells previously shut-in due to corrosion leaks. The third application was in a new-drill well where a 205 ft patch isolated holes in casing from a perforating gun misfire. All three patches pressure-tested successfully thus enabling the wells to be fracture stimulated and produced.
The product provides high-strength flush-bore expandable seals at the ends of a liner comprised of conventional OCTG pipes. Unique about this system is that the expansion mandrel becomes integral with the seal assembly to provide internal yield and collapse resistance comparable to the OCTG liner. A hydraulic setting tool powered via work string by a high-pressure/low-volume pump (i.e., typical BOP or tubing tester) drives the expansion mandrel into the patch body.
The product, built initially as a one-trip system, was simplified and made more reliable by running as a two-trip system. First, the lower expandable seals and polished bore receptacle are installed. Next, the spacer string with upper seal is stung into the lower receptacle and the upper seals are expanded. The system is versatile in that the upper expandable seal also provides a receptacle to which a tieback liner, production tubing or another patch can be attached.
The paper highlights job design and execution including use of casing inspection logs, problems encountered, system improvements and best practices resulting from this work.
Determination of Relative Permeabilities and Capillary Pressures by an Automatic Adjustment Method.
Authors: Chavent G. , Cohen G. , Espy M. 
Published: December 2007

ABSTRACT
Drainage or imbibition experiments in laboratory are often interpreted by trial and error: the flow equations are solved for different values of petrophysical parameters and the best fit determined by successively adjusting calculated productions with measured ones. These methods can be slow and time consuming.
In this paper we propose an automatic adjustment method based on optimal control theory. The unsteady one dimensional biphasic flow differential equations have been rewritten so as to exhibit three linearly independent terms which are functions of relative permeabilities and capillary pressure. These three functions are determined by a least square technique following discretization of the equations by a mixed finite elements method.
Two types of experiments are needed to carry out the interpretation, one with a fast flow rate, the other with a displacement velocity representative of reservoir conditions.
Running the automatic adjustment scheme on the results of the two experiments mentioned above yields directly the relative permeability curves and the capillary term function. The capillary curve is deduced from the capillary term function.
Use of mixed finite elements significantly contributes to accuracy and stability in the solution of the equations. Furthermore, the method remains valid in the two limiting cases of hyperbolic (imbibition alone) and parabolic equations (Buckley-Leverett approximation).
We illustrate the method for oil displacements by water and gas and for imbibition. Very satisfactory results are obtained, A comparison is also made with results given by trial and error adjustment.
Two Phase Flow in Well-Flowlines
Authors: Yocum B.T. 
Published: December 2007

Introduction
Effective oilfield planning in Arabia required approximate solution of the two phase flow problem in oil wells and flowlines. Stated in broad terms, the problem resolved to determination of well flowline potential (B/D) as a function of major system variables:Flowing bottom-hole pressure, reservoir pressure and temperature, productivity index.Crude characteristics; pressure - volume - temperature (PVT) relationships, viscosities, and composition.Depth of oil well, diameter of casing and tubing, length and diameter of flowline.Trap pressure (back pressure at end of flowline), ambient temperature, ground temperature.
Relationships developed for well-flowlines have maximum usefulness if they can be extrapolated to low reservoir pressures, representing future conditions, with confidence. It was therefore decided to develop the physical relationships from basic fluid dynamic and thermodynamic principles whenever possible rather than relying on existing empirical equations. The coefficients of the theoretically sound equations; friction factors, heat transfer coefficients, thermal gradients, etc., were then correlated for flowing mixtures of gas and oil in actual well-flowlines. For convenience, the oil well will be taken up first and the flowline afterwards. Then, the two will be combined to give the overall well-flowline relationships.
Scanning Electron Microscope-Cold Stage : Viewing Fluid Saturated Reservoir Rock
Authors: Schwartz Daniel E. 
Published: December 2007

ABSTRACT
A single module cold stage unit has been interfaced with a Scanning Electron Microscope to allow for the observation of fluid (oil, brine, water, etc.) saturated reservoir rock. The module provides sample freezing, fracturing, and coating capability for the observation of fully saturated rock material at liquid nitrogen tempertures. The ability to observe fluids in place in sedimentary rocks has expanded our understanding of relative fluid distributions and has increased the usefulness of the S.E.M. for reservoir rock characterization.
Hydraulics of Drilling with Aerated Muds under Simulated Borehole Conditions
Authors: Zhou L. , Ahmed R. M. , Miska S. Z. , Takach N. E. , Yu M. , Saasen A. 
Published: December 2007

Abstract
Maintaining optimum circulation rates is important in aerated mud drilling operations. However, reliable predictions of the optimum rates require accurate modeling of the frictional pressure loss at bottom-hole conditions. This paper presents a mechanistic model for underbalanced drilling with aerated muds. Extensive experiments in a unique field-scale high pressure and high temperature flow loop were performed to verify the predictions of the model. This flow loop has a 150 mm × 89 mm (6" × 3.5") horizontal annular geometry and is 22-m long. In the experiments, cuttings were introduced at a rate of 7.5 kg/min, representing a penetration rate of 15m/hr in the annular test section. The liquid phase flow rates were in the range of 0.30 - 0.57 m3/min, representing superficial liquid velocities in the range of 0.47 - 0.90 m/s. Gas liquid ratio (gas volume fraction under in-situ condition) was varied from 0.0 to 0.38. Test pressures and temperatures ranged from 1.28 to 3.45 MPa, and 27 °C to 80 °C, respectively. Gas-liquid ratios were chosen to simulate practical gas-liquid ratios under downhole conditions. For all the test runs, pressure drop and cuttings bed height over the entire annular section were measured. Flow patterns were identified by visual observations through a view port. The hydraulic model determines the flow pattern and predicts frictional pressure losses in a horizontal concentric annulus. The influences of gas liquid ratio (GLR) and other flow parameters on the frictional pressure loss are analyzed using this model. Comparisons between the model predictions and experimental measurements show a satisfactory agreement. The present model is useful for the design of underbalanced drilling applications.
Planning for Drilling, Completing and Testing a Deep, Abnormal Pressure, Sour Gas Wildcat in Mississippi
Authors: Stair Mark A. , Rogers Ronald D. , Carlton Louis A. 
Published: December 2007

ABSTRACT
Exxon has spudded and drilled to total depth a deep sour gas well in the South Jackson Area in Mississippi. This well is planned to be completed with a redundant pressure string concept using a high strength (150,000 psi minimum yield) corrosion resistant alloy. The use of this completion concept required larger hole sizes and heavier casing strings than have previously been used by other operators in this area.
Are You Prepared Before You Start
Authors: Bowden Joe R. 
Published: December 2007

ABSTRACT
The search for oil and gas has led to more hostile environments below and above the ground. This, coupled with the experience level of today's rig crews, has led to a growing concern for human and environmental safety. This concern should not begin at the development of a crisis but should be carried back to the well planning stages. The success of averting or preventing a crisis usually lies with proper well planning.
A great deal of literature and technical knowledge is available today for the operator to assist him in the drilling of oil and gas wells. Tubular design, mud rehology, pore pressure determination, drilling equipment design, bit design, etc., have all become highly technical and are far superior today than 10 years ago. Extensive well planning has become a common practice for many of today's drilling departments but is not carried down the ranks to the field.
The planning of a successful adventure is important, but even more important is the correct implementation of the well plan. The importance of a spud meeting with the well site supervisor cannot be overemphasized. A spud meeting would review the mechanics of drilling the well, the necessary communications, company oriented paperwork, and kill procedure to be used if a kick is taken. Once the well site supervisor knows his level of responsibility for the particular job he will be more qualified to execute the well program.
Comprehensive Design Formulae for Hydraulic Fracturing
Authors: Cleary Michael P. 
Published: December 2007

ABSTRACT
This paper provides a number of comprehensive algebraic formulae, with readily determinable coefficients, which can be used to predict the extent and width of fractures produced by fluid injection at specified rates or borehole pressures, when these are reasonably well-behaved functions of time. The fracture geometries described include as special cases the models currently in use for industrial design of hydraulic fractures, but extensions to allow variable fracture height are readily achieved. The formulae serve both to simplify the implementation of conventional models and to allow development of more realistic simulations which contain the rather idealised concepts of those models in their rightful place as components of a more general three-dimensional description. One such pseudo-3-D model is described in its simplest form; it allows physically credible tracing of length, height and width distributions under conditions of slow vertical spreading which a desirable stimulation treatment would achieve. All of the models admit quite general reservoir properties and frac-fluid behavior. A few popular applications are used to illustrate their power and simplicity.