bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Theory Relating High Temperatures and Overpressures
Authors: Lewis C.R. , Rose S.C. 
Published: December 2007

The theory proposed here is that an overpressured zone, because it is uncompacted, constitutes a thermal barrier. That is, this uncompacted zone contains excess amounts of water, and water has three times the insulating value of the rock matrix. It follows that the greater the water content, the greater the insulating value of the zone.

Introduction
For any drilling area, geothermal gradient maps have been made that attempt to show the "normal" temperature gradients that will be found. Along the Texas Gulf Coast these will range from 1.6 degrees to 2.2 degrees F/100 ft. Most of the time the temperature profile for a new well can be predicted from one of these maps. At times, however, we find that the temperature gradient changes with depth. Other authors have observed that in the Gulf Coast region the overpressured zones also have abnormal temperature gradients. The fact that abnormally high gradients seem always to occur with overpressured zones is both significant and unexplained. We advance a theory to relate high pressure zones and deviations from normal temperature profiles. profiles. The Theory
It is generally agreed that almost all of the heat flowing within the earth comes from the core and moves outward to the surface where it is lost into space as radiant energy. Wherever flowing heat meets an obstacle (an insulator) there is a buildup of heat against its face. The temperature rises on this face until a higher temperature gradient exists across the obstacle. Enough heat will then flow through the insulator to balance the flow of incoming heat. It is clear that a higher temperature gradient must be imposed across a heat insulator than across a heat conductor to achieve equal heat-flow rates. Therefore, if we observe a very high gradient within the earth, we would normally conclude that the high gradient zone is an insulator. Our theory is that high pressure zones are heat insulators; therefore, we expect abnormal temperature gradients to exist across them. An analytical proof follows. proof follows. We must show that a high-pressure zone is in fact an insulator. A high-pressure zone differs structurally from the surrounding rock in that it is less compacted. There is much more pore space to be occupied by fluid. Thus, an overpressured, uncompacted rock has considerably more water than a normally pressured, compacted rock. The conduction of heat is expressed by
where is the heat flow, kh is the coefficient of thermal conductivity of the substance, A is the cross-sectional area of the substance, measured perpendicular to the flow of beat, delta T is the perpendicular to the flow of beat, delta T is the temperature change across the substance, and L is the length (thickness) of the substance. It can be seen that varies directly with kh. Thus, if water has a lower value of kh than silica, water is the better insulator.
JPT
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Casing Design for Trapped Annular Pressure Buildup
Authors: Halal A. S. , Mitchell R. F. 
Published: December 2007

Summary
Conventional single-string analysis for casing design with annular-fluid expansion can underpredict or overpredict pressures between strings because multistring effects are neglected. Multiple-string systems with multiple sealed annuii behave as composite interactive systems. This paper presents a constitutive-based multistring analysis method for composite string effects and complex fluid behavior. The composite stiffness of cemented casings is determined from elastic stress/strain relationships, and the nonlinear fluid behavior is modeled by direct use of fluid PVT relations in the formulation and solution. The method is incorporated in a computer model linking comprehensive stress calculations to accurate temperature and pressure predictions. Sensitivity studies of the system response to various key parameters and operating conditions are presented, and comparisons are made with single-string analyses to demonstrate the strong interaction between casing strings.
Disposal of Oily Cuttings by Downhole Periodic Fracturing Injections, Valhall, North Sea: Case Study and Modeling Concepts
Authors: Moschovidis Z. A. , Gardner D. C. , Sund G. V. , Veatch R. W. 
Published: December 2007

Summary
This paper presents the results of a pilot study for the injection of cuttings at great depth [8,094 ft total vertical depth (TVD)] in Paleocene/Eocene shale by periodic fracturing injections in two wells in the Valhall field in the North Sea. Injection is necessary to meet environmental requirements (&lt; 1 vol% of oil in the cuttings disposed in the sea) that went into effect Jan. 1,1993. Valhall is an Upper Cretaceous chalk oil reservoir ≈ 180 miles offshore southern Norway. Amoco operates the field for Amerada Hess Norge A/S, Elf Petroleum Norge A/S, and Enterprise Oil Norge Ltd. Simulations were performed with a new conceptual model for disposal of cuttings (called the "disposal domain"). The actual pressure response during cuttings injections supports the model predictions. The cuttings are contained within a limited region of the formation (the disposal domain) where a system of hydraulic fractures have been created. The same model then was used to estimate the capacity of the formation to contain cuttings without increasing the treating pressure (and the closure stress) beyond the capacity of the tubulars.
Heated Mud Systems: A Solution to Squeezing-Salt Problems
Authors: Muecke N. B. 
Published: December 2007

Summary
Squeezing salts have been a major problem to operating companies worldwide for many years. Most previous solutions to the problem have been aimed at treating the symptoms rather than the cause. Generally, these have been based on running casings capable of withstanding the nonuniform salt loadings because satisfactory cementations have been virtually impossible to achieve because of large washouts in the salt layers. The solution is to use standard oilfield equipment to drill a gauge hole through the squeezing salts, thus providing an optimum cementation environment. Various methods were used to try to resolve the problem; the last was the use of thick-walled casings in conjunction with saturated potassium/ magnesium drilling fluids to reduce salt washout. Unfortunately, washouts still occurred because the muds could not be saturated at the surface to downhole conditions. Now, the drilling fluid is heated on the surface, enabling the required level of salt concentration to be achieved. The heating system, comprising a boiler and heat ex-changer from a conventional well-test package, has been used on eight wells to date. In each case, a gauge hole was drilled through the squeezing-salt sections and, subsequently, successful cementations were performed.
Gas-Well Deliverability Monitoring: Case Histories
Authors: Thrasher T. S. 
Published: December 2007

Summary
This paper presents practical techniques that can be used to monitor gas-well performance. These techniques, along with the routine examination of performance data, can help the engineer maintain production potential and extend well life. This paper demonstrates the importance of monitoring well performance on a regular basis through case history examples. Four types of well conditions are described: (1) deterioration in performance over time, (2) drainage area change, (3) liquid loading, and (4) tubing design constraint. This paper also discusses the use of a personal computer program as a tool to facilitate and encourage gas-well performance monitoring.
Using PC's and Monte Carlo Simulation To Assess Risk in Workover Evaluations
Authors: Wiggins Michael L. , Zhang Xu 
Published: December 2007

Summary
Implementing Monte Carlo methods on a PC can significantly improve risk assessment in the evaluation of workover opportunities. Monte Carlo simulation is a probabilistic method that allows the evaluator to consider an entire range of potential outcomes. This paper presents a method for implementing Monte Carlo methods in a PC environment to evaluate workover opportunities.
Parameterization of Complex 3D Heterogeneities: A New CAD Approach
Authors: Wietzerbin L. J. , Mallet J. L. 
Published: December 2007

SummaryThis paper presents a new method for generating and interpolating complex reservoir shapes in 3D. The method combines integration of quantitative knowledge about the shapes of the geologic bodies being modeled and generation of a large range of possible geometries corresponding to this knowledge. It is a new CAD approach based on the discrete smooth interpolation method (DSI). We apply this method to the geometric modeling of part of a complex turbiditic reservoir. In this example, channels and lobes account for most of the production, and their geometries are critical factors for oil recovery. Data include well logs, statistics about the shapes of main reservoir heterogeneities, and 3D templates representing the most likely shape. Geometric characterization of the sand bodies in this field is performed through stochastic modeling. The method used involves a Boolean approach based on indicator components and emphasizes the importance of honoring well data.
Gas/Oil Capillary Pressure of Chalk at Elevated Pressures
Authors: Christoffersen K. R. , Whitson C. H. 
Published: December 2007

Summary
Accurate capillary pressure curves are essential for studying the recovery of oil by gas injection in naturally fractured chalk reservoirs. A simple and fast method to determine high-pressure drainage capillary pressure curves has been developed. The effect of gas/oil interfacial tension (IFT) on the capillary pressure of chalk cores has been determined for a methane/n-pentane system.
Measurements on a 5-md outcrop chalk core were made at pressures of 70, 105, and 130 bar, with corresponding IFT's of 6.3, 3.2, and 1.5 mN/m. The results were both accurate and reproducible. The measured capillary pressure curves were not a linear function of IFT when compared with low-pressure centrifuge data. Measured capillary pressures were considerably lower than IFT-scaled centrifuge data. It appears that the deviation starts at an ΓFT of about 5 mN/m.
According to the results of this study, the recovery of oil by gravity drainage in naturally fractured chalk reservoirs may be significantly underestimated if standard laboratory capillary pressure curves are scaled by EFT only. However, general conclusions cannot be made on the basis of only this series of experiments on one chalk core.
Permanent Downhole Gauges Used in Reservoir Management of Complex North Sea Oil Fields
Authors: Unneland Trond , Haugland Torstein 
Published: December 2007

Summary
This paper presents experience with and applications of permanent downhole pressure and temperature gauges in the reservoir management of two complex North Sea oil fields, Gullfaks and Veslefrikk (both operated by Statoil A/S). In total, 40 quartz and quartz capacitance gauges from three different suppliers have been installed in platform wells over 6 years. The gauges have given invaluable realtime data for reservoir management of these two fields and contribute directly to increased daily oil production. The installations have proved to be safe and reliable, as well as good investments.
Real-Time Pore Pressure and Fracture-Pressure Determination in All Sedimentary Lithologies
Authors: Holbrook P. W. , Maggiori D. A. , Hensley Rodney 
Published: December 2007

Summary
Pore pressure and fracture gradient are the two natural limits that exert the greatest influence on drilling costs and safety. Traditional empirical "pore pressure" models are limited to one lithology type (shale) and rely on incorporating petrophysical or drilling data vs. depth trend lines. We describe a new method that quantifies the effective-stress law, p = S − σv. This method uses petrophysical data (gamma ray, resistivity, density) and mineralogic stress/strain relationships to calculate pore pressure and fracture gradient, on a foot-by-foot basis, through all sedimentary rock types.
Cretaceous marls and limestones have proven to be an obstacle for traditional pore-pressure evaluation methods. With numbers of high-pressure exploration wells in the North Sea Central graben increasing, there is a need for a better understanding of pressures through the Cretaceous and into the pressured formations below. This effective-stress-law method, which is used to determine pore pressure/fracture gradient, has been tested successfully in the complex limestone/shale and sandstone-shale sequences of the North Sea as an aid to well planning and real-time drilling operations decision making by use of measurement while drilling (MWD) petrophysical data.
This method has recently been used successfully on two Central graben wells. BP drilled a high pressure/high temperature (HPHT) well in the second quarter of 1993 and used on-site pore pressure and fracture gradient (PP/FG) calculations, along with other more traditional pore-pressure methods, to help set an intermediate casing string at an optimum depth. We discuss results of these case studies and technical content of this pore-pressure method.
Pressure Transient Analysis of Dually Fractured Reservoirs
Authors: Al-Ghamdi Abdullah , Ershaghi Iraj 
Published: December 2007

Abstract
Dual fracture models are examined as a more realistic alternative to dual porosity models for the representation of naturally fractured reservoirs. A major component of the fracture system is the network of microfracture which by virtue of their lower permeability respond somewhat later than the macrofractures. A delineation of microfracture response versus matrix response is made using the proposed conceptual models. It is demonstrated that the microfractures response may at times be mistakenly attributed to matrix.
A Simplified Analysis of Unsteady Radial Gas Flow
Authors: Aronofsky J.S. , Jenkins R. 
Published: December 2007

Abstract
A simple means of predicting the flowing well pressure history in a natural gas reservoir has been developed. The differential equation for unsteady radial flow of gases through porous media was solved by numerical methods using electronic punch card machines. The results obtained from these calculations are presented in a generalized form which is believed to be most convenient for engineering use. These results are compared with those presented in a paper by Bruce, et al.
An effective radius of drainage has been defined which permits the equation of steady state gas flow to be used easily to predict well pressures in gas reservoir depletion. An equivalent effective radius of drainage is defined for liquid flow systems and a comparison is made of the gas solution to the liquid solutions.

Introduction
This paper presents a numerical method for describing the transient flow of gases radially through a porous medium from which the production rate is specified. The results obtained from these calculations are presented in a generalized form which is believed to be the most convenient for engineering use.
The principal application of these calculations should be to flow in natural gas reservoirs, in the interpretation of pressure drawdown tests, in the estimation of reserves, and in calculation of injection pressures required in gas injection and cycling operations. The evaluation of natural gas wells is based upon back-pressure tests in which measurements of production rate and flowing well pressure are made for periods of one, two, or more days. The flow is assumed to have stabilized at this time, and the observed values of pressure and production rate are used with standardized formulae to determine the well's allowable production rate. Furthermore, the results obtained from such a test of short time duration are extrapolated in such a manner to allow a prediction of what the well pressure will be at some future time for a specified (but possibly untested) flow rate.
Effects of P-p-T Behaviour of Muds on Static Pressures during Deep Well Drilling - Part 2: Static Pressures During Deep Well Drilling
Authors: Babu D. R. 
Published: December 2007

Summary
In this study, published p-ρ-T data of twelve muds are compared using three models already proposed. The empirical model suggested by Kutasov is found to represent the measured data more accurately than the other models for a majority of the muds. With the help of the empirical model, an explicit equation is derived analytically to predict static pressures at different depths. Based on the analysis, an equivalent static density (ESD) variable is defined that incorporates the mud p-ρ-T behavior, pressure and temperature of the mud at surface, thermal gradient, and depth of the well. It is suggested that ESD should be used in place of normally used mud weight term in all phases of deep well drilling. The analysis is applied to a high-temperature, 25,000-ft deep example well. It is observed that static pressure or ESD at the bottom of the well decreases during tripping and the extent of decrease is dependent on the type of mud. For the example well, it is estimated that a maximum reduction in ESD of about 0.62 lbm/gal occurs in the case of 18-lbm/gal water-basedmud, and a minimum reduction of about 0.2 lbm/gal occurs in the case of a 11-lbm/gal diesel-oil-based mud.
Examples of Petroleum Engineering Objects
Authors: Griffiths A. E. 
Published: December 2007

Summary
In recent years, object-oriented (OO) methods have gained prominence among software developers as a means of more closely modeling the real world.1,R2 Most OO applications to date have their roots in the field of computer science, and this may deter people without a strong computing background from further investigating OO. However, OO methods can be applied to concepts that may be more familiar to petroleum engineers. The intention of this paper is to demonstrate that the power of OO can be used to simplify the solution of practical problems by engineers having only a limited background in computing. We present three such petroleum engineering applications in this paper: probabilistic reserves evaluation, a gas recycling scheme, and material-balance calculations.
In the first of these examples, we use OO methods to model a simple gas recycling scheme, taking into account explicitly vapor/liquid equilibrium, both in the surface separation train and in the reservoir. In the second example, we use OO methods instead of the well-known Monte Carlo method to derive a reserves expectation curve. In the third example, we analyze the Schilthuis material-balance method and represent it using simple objects.
A brief introduction to objects will prepare the ground for the more detailed analysis of these applications. In each case, we briefly review the underlying principles and analyze them in terms of objects. We will demonstrate the structure and implementation of each of the resulting object classes using short C++ programs.3 Finally, we apply these object classes to the solution of some real-life problems that have appeared in the petroleum engineering literature.
Ensemble Computing for the Petroleum Industry
Authors: Annaratone Marco , Dossa Don 
Published: December 2007

Summary"Computer downsizing" is one of the most often used buzzwords in today's competitive business, and the petroleum industry is at the forefront of this revolution. Ensemble computing provides the key for computer downsizing with its first incarnation, i.e., workstation farms. This paper concerns the importance of increasing the productivity cycle and not just the execution time of a job. We introduce the concept of ensemble computing and workstation farms. Then we discuss how different computing paradigms can be addressed by workstation farms.
An Analysis of Horizontal Wells Intercepted by Multiple Fractures
Authors: Raghavan Rajagopal S. , Chen Chih-Cheng , Agarwal Bijan 
Published: December 2007

Summary
A mathematical model is developed and used to discern the characteristic responses of a multiply-fractured horizontal-well. A systematic discussion of pressure behaviors is given. New interpretations and conclusions are provided. A simple, screening guide to evaluate the efficacy of this completion scheme is presented. The consequences of perforating selective sections after fracturing are examined. The pressure behaviors that are discussed in this work are used to analyze responses of a field test. This test was conducted on a medium-radius horizontal-well completed in a dolomite/anhydrite formation with a 1900′ horizontal section. Four distinct intervals were perforated and individually stimulated. Results from the analysis of the commingled test are presented in this work. The methodology outlined here should be useful to others. Practical guidelines are provided.
Gel Placement in Fractured Systems
Authors: Seright R. S. 
Published: December 2007

SummaryThis paper examines several factors that can have an important effect on gel placement in fractured systems, including gelant viscosity, degree of gelation, and gravity. For an effective gel treatment, the conductivity of the fracture must be reduced and a viable flow path must remain open between the wellbore and mobile oil in the reservoir. During placement, the gelant that "leaks off" from the fracture into the rock plays an important role in determining how well a gel treatment will reduce channeling. For a given volume of gelant injected, the distance of gelant leakoff is greater for a viscous gelant than for a low-viscosity gelant (other factors being equal).In one method to minimize gelant leakoff, sufficient gelation is designed to occur before the gelant leaves the wellbore. We investigated this approach in numerous experiments with both fractured and unfractured cores. We studied Cr(III)/acetate/hydrolyzed polyacrylamide (HPAM), resorcinol/formaldehyde, Cr(III)/xanthan, aluminum/citrate/HPAM, and other gelants and gels with various delay times between gelant preparation and injection. Our results suggest both hope and caution concerning the injection of gels (rather than gelants) into fractured systems. Tracer studies indicate that some gels can effectively heal fractures under the right circumstances. However, high resistance factors exhibited during placement could limit the ability to propagate certain gels deep into a fractured system unless the fractures are very conductive.
Modeling the Effects of Infill Drilling and Pattern Modification in Discontinuous Reservoirs
Authors: Christman P. G. 
Published: December 2007

Summary
This paper present a lens model, based on a physical concept of the individual pay members, that is the first model designed to calculate reserves from infill drilling and pattern changes. The model conceptualizes the reservoir as being made up of a large number of randomly located circular disks or lenses sealed at the edge. Calculations of drainability, floodability and secondary/primary ratio are presented for two calibrated lens-size distributions. The results of these calculations are compared with the performance of some Wasson Clearfork trend waterfloods.