bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-Lapse Ultrasonic Measurements of Laboratory Hydraulic-Fracture Growth: Tip Behavior and Width Profile
Authors: Groenenboom J. , van Dam D. B. , de Pater C. J. 
Published: December 2007

SummaryWe performed acoustic measurements in a time-lapse sequence in scaled laboratory tests. The advantage of time-lapse measurements is that the fracture response can be separated from the background signal. As a consequence, not only can the hydraulic fracture be detected, but its shape and geometry can be measured during its growth. This application requires the combined information of both compressional- and shear-wave measurements. We apply this technique to propagation, flowback tests, and reopening of hydraulic fractures.Acoustic waves excite diffractions at the fracture tip. These diffractions are used to locate and to characterize the fracture tip. The acoustic measurements indicate that we can distinguish between a dry tip and the fluid front of the fracture.Shadowing of shear-wave transmissions allows estimation of the moment of fracture initiation. The width profile of the fracture is determined with compressional-transmission measurements. This application is based on the fact that the attenuation and time delay of compressional transmissions are proportional to the fracture width. Analysis of a flowback test shows that the fracture closed at the wellbore but remained open farther away from the wellbore.
Comparison of Period- or Height-Dependent, Sea-State Parameters From a Theoretical Model With Observation at Sea
Authors: Arhan M. , Ezraty R. , Laurent M. 
Published: December 2007

Abstract
A joint theoretical probability density for individual wave heights and periods, originally developed to describe storm conditions, is compared with about 2,000 routine wave recordings in the Bay of Biscay. From this joint probability density, all other mean sea-state parameters (HT 1/3, - TH 1/3, T 1/3 . . .) can be computed using H 1/3, T, and, the spectrum width parameter. The systematic discrepancy existing between theory and observation can be corrected empirically if necessary.

Introduction
Cartwright and Longuet-Higgins predicted the height of sea waves and computed the significant wave height, h 1/3, or similar variables, h 1/n, as well as the expectancy of the maximum, E(h max), of a given number of waves. They started with mo and, the total energy and the width parameter of the spectrum, respectively.To describe a sea state, a characteristic period and characteristic height are necessary. In the "zero-up-crossing" wave analysis the following periods usually appear: (1) T 1/3 is the mean of the periods usually appear:T 1/3 is the mean of the highest third of the zero-up-crossing periods,TH 1/3 is the mean of the periods connected to the waves used to compute H 1/31 andThis the mean of the zero-up-crossing periods.In the same way, T 1/n and TH 1/n also can be defined.
Wiegel found empirical relationships between these characteristic periods, based on observation at sea. Our theoretical model is based on the theory of Gaussian noise as established by Rice and leads to an explicit formula for the joint probability density of wave heights and periods. probability density of wave heights and periods. This density is fixed when given these parametersa characteristic height, a characteristic period, and epsilon. Then, by appropriate integrations, we can relate the different average heights to the associated average periods that describe a given sea state. Although the narrow-band spectrum hypothesis is not always satisfied, computed values of mean quantities from observations at sea remain close to their theoretical equivalents. Any systematic discrepancy can be corrected if necessary.

THE THEORETICAL MODEL
A model was developed using as a starting point, the joint probability density for a Gaussian noise signal with a maximum value, 1, and a second derivative with respect to time, 3, as
........................................(1)
We have assigned to each positive maximum a sinusoidal wave with amplitude 1 and period T given by
SPEJ
p. 233
Evaluation of the M-Site B-Sand Fracture Experiments: Evolution of a Pressure Analysis Methodology
Authors: Gulrajani Sunil N. , Nolte Kenneth G. , Romero Jean 
Published: December 2007

SummaryThe most comprehensive hydraulic-fracturing data including the first objective measurements of fracture height, length, and width are acquired from the Gas Research Inst. (GRI)/Dept. of Energy (DOE) Multiwell Site (M-Site) tests. In spite of the availability of extensive and reliable fracturing data, significant deviation between predicted and microseismic-determined fracture geometry was reported. The purpose of this study is to provide a consistent analysis of B-sand experiments by applying a systematic methodology for fracture-treatment evaluation.For this analysis, fracture parameters are estimated initially from laboratory data, well logs, and calibration tests. These parameters are refined by matching simulated pressures to field-measured fracturing pressures recorded during the first linear gel injection. These fracture parameters then are used to compare predicted- and measured-fracture pressures on all subsequent injections. Although general agreement for the fracturing pressures was obtained, a discrepancy was noticed between zone stresses estimated by evaluation and their variation as indicated on published stress logs. Stress data were reinterpreted and an acceptable pressure match was established.Fracture parameters resulting from this study are in agreement with independently inferred estimates. In addition, an apparent difference between closure pressure and microfrac stress is resolved. Finally, good agreement between predicted fracture geometry and microseismic readings is observed for each injection test considered in this study. This study shows that fracture pressures and geometry can be predicted consistently with good accuracy using elementary analysis techniques, without a reliance on ad hoc physical explanations.
Proppant Transport Characterization of Hydraulic-Fracturing Fluids Using a High-Pressure Simulator Integrated With a Fiber-Optic/Light-Emitting-Diode (LED) Vision System
Authors: Shah Subhash N. , Asadi Mahmoud , Lord David L. 
Published: December 2007

SummarySlurries of selected hydraulic-fracturing fluids such as 40-lbm/Mgal hydroxypropyl guar (HPG) linear gel and borate-crosslinked 35-lbm/Mgal guar gel were evaluated to characterize their proppant transport properties using 6-lbm/gal 20/40-mesh sand. In addition, fluids such as water, 40-lbm/Mgal HPG linear gel, and borate-crosslinked 35-lbm/Mgal gel were evaluated to determine their relative ability to remove the fluidized layer lying along the top of settling proppant bed and subsequently to erode more compacted layers below. The experimental study used a unique high-pressure parallel-plate flow cell, simulating a down-hole fracture, integrated with a fiber-optic vision system and LED.
Silica Micro-Encapsulation Technology for Treatment of Oil and/or Hydrocarbon-Contaminated Drill Cuttings
Authors: Quintero Lirio , Limia Jose M. , Stocks-Fischer Shannon 
Published: December 2007

Summary
Silica micro-encapsulation (SME) is a new technology that has significant economic and environmental value because it allows disposal of oil- and/or hydrocarbon-contaminated drill cuttings, either onshore or offshore, in an environmentally safe manner.
SME is a process by which the oil attached to the drill cuttings is removed by emulsification and then physically encapsulated within an insoluble matrix of amorphous silica. The process consists of the addition of an emulsifier in an acidic environment, followed by the addition of water-soluble silicate.
Specific emulsifiers are selected to cover hydrophilic-lipophilic balance (HLB) requirements for a broad range of oils used in drilling fluids, including synthetics, mineral oil, diesel, crude oil, and bitumen.
Laboratory and pilot tests of the SME technology show that, using environmentally acceptable emulsifiers, oil-based mud present on drill cuttings is removed and forms a stable oil-in-water emulsion. These results led to development of a process for SME treatment of drill cuttings that could be environmentally acceptable for offshore applications, as described in previous publications.1,2
Electrical Measurements in the 100 Hz to 10 GHz Frequency Range for Efficient Rock Wettability Determination
Authors: Bona Nicola , Rossi Elio , Capaccioli Simone 
Published: December 2007

SummaryThis paper summarizes an experimental and theoretical study conducted to investigate the effect of rock wettability on the electrical response of water- and oil-saturated core samples in a wide frequency band. The aim of the study was to evaluate a technique not previously applied to wettability determination as a practical alternative to conventional tests, and to ascertain the consequent economic and technical benefits in reservoir appraisal.
Effect of Discontinuous Shales on Reservoir Performance During Horizontal Waterflooding
Authors: Jackson M. D. , Muggeridge A. H. 
Published: December 2007

Summary
We investigate quantitatively the effect of inclined and intersecting discontinuous shales on horizontal waterfloods, using generic, dimensionless two-and three-dimensional models. We focus upon whether the shales alter the sweep efficiency. We find that they have a significant effect only if they are continuous over large areas of the bedding surfaces and are steeply inclined to the flow, or if the displacement is highly unfavorable. We also find that two-dimensional simulations can significantly overestimate the effect of intersecting shales, because they assume that the shales are entirely continuous in the third dimension.
Improved Oil Recovery in Carmópolis Field: R&D and Field Implementations
Authors: Mezzomo Roberto F. , Luvizotto José M. , Palagi Cesar L. 
Published: December 2007

SummaryCarmópolis field, in northeastern Brazil's Sergipe/Alagoas basin, is the country's largest onshore oil accumulation at 253 × 106 m3 original oil in place (OOIP) and a current total oil production of 2880 m3/d. Discovered in 1963, it was quickly put into primary production. Waterflooding followed in 1971 at the central portion of the field. The combination of adverse fluid mobility ratio, reservoir heterogeneity, and the lack of proper selective injection led to the quick decline of production; however, a major program of selective plugging, stimulation, and selective injection was able to stabilize production immediately. Waterflooding was then extended to the entire main block of the field. The well pattern was changed from five- to nine-spot arrangement, with a corresponding downsizing in well spacing and injection rates. Carmópolis also was subjected to an intense improved oil recovery (IOR) campaign with pilot tests on polymer flooding, steam-flooding and in-situ combustion. The history of Carmópolis field and the significance of waterflooding to oil production in Brazil, with approximately 2000 × 106 m3 OOIP currently submitted to this method of recovery, led to the selection of Carmópolis as the target for one of the projects in the PRAVAP (Petrobras Strategic IOR Program) portfolio. The scope of this project included a review of the waterflooding operation through improved reservoir characterization and flow simulation, as well as the investigation of other IOR methods that might reverse the declining production trend. This paper reviews the IOR history of Carmópolis field and summarizes the outcome of the PRAVAP project that led to the approval of field implementations worth U.S. $34 million net present value (NPV).
Miscibility Variation in Compositionally Grading Reservoirs
Authors: Høier Lars , Whitson Curtis H. 
Published: December 2007

Summary
Minimum miscibility conditions of pressure and enrichment (MMP/MME) have been computed with an equation of state (EOS) for several reservoir-fluid systems exhibiting compositional gradients with depth owing to gravity/chemical equilibrium. MMP/MME conditions are calculated with a multicell algorithm developed by Aaron Zick, where the condensing/vaporizing (C/V) mechanism of developed miscibility is used as the true measure of minimum miscibility conditions when it exists. The Zick algorithm is verified by detailed one-dimensional (1D) slimtube simulations with elimination of numerical dispersion. The miscibility conditions based on the traditional vaporizing-gas-drive (VGD) mechanism are also given for the sake of comparison, where it is typically found that this mechanism overpredicts conditions of miscibility.
Significant variations in MMP and MME with depth exist for reservoirs with typical compositional gradients, particularly for near-critical oil reservoirs and gas-condensate reservoirs where the C/V mechanism exists. An important practical implication of these results is that miscible displacement in gas-condensate reservoirs can be achieved far below the initial dewpoint pressure. The requirement is that the injection gas (slug) be enriched somewhat beyond a typical separator gas composition and that the C/V miscibility mechanism exist. This behavior results in many more gas-condensate reservoirs being viable candidates for miscible gas cycling than previously assumed, and at cycling conditions with lower cost requirements (i.e., lower pressures) and greater operational flexibility (e.g., cycling only during summer months).
Synergy Is Essential to Maximum Recovery Michel T. Calls for Full Coordination Of Petroleum Engineers and Explorationists
Authors: Halbouty Michel T. 
Published: December 2007

You call for full coordination of geologists, geophysicists, and petroleum engineers to advance petroleum exploration, development, and production. Does this require a revolutionary change in the way each discipline and industry managers think of their responsibilities?
Absolutely not. In fact I think that it is the duty and responsibility of industry managers to encourage full coordination of geologist, geophysicists, and petroleum engineers to advance petroleum exploration, development, and production. Any petroleum exploration, development, and production. Any supervisor or manager who does not encourage such coordination is a liability to his company and should be dismissed. Do you see the team approach as basic to most exploration, development, and production work, or useful in limited but vital areas?
The team approach is definitely basic. Not only to most. but to all exploration, development, and production work. This coordination should not be limited in any manner.
How essential is the synergy idea to future petroleum reserves and production?
Very essential. Without it I doubt that we will be able to find the future petroleum reserves which I think exist in this country and require extensive drilling to find.
Do economics already indicate a basic need for a new approach in the petroleum sciences and engineering?
Yes - because costs to explore. drill, and produce are so high that every effort should be made to reduce these costs by coordination of the three disciplines. You would be surprised how this coordination can reduce costs. In our shop we have definitely proven, without any doubt whatsoever, that costs are reduced when geologist, geophysicists, and petroleum engineers get together and discuss every phase of the exploration, drilling, and production effort. This eliminates the "I told you so" chiding if a mistake is made by a particular discipline.
Does the combined effort apply equally to exploration and development in new as well as old areas?
Yes. The combined effort should apply to new as well as old areas. In fact, this combined effort is particularly productive in old areas.
What role does the team approach play in finding new reserves near producing reservoirs?
Traditionally, explorationists seek and find and petroleum engineers develop and produce.
P. 750
A New Approach for Log Analysis of the Pulsed Neutron and Resistivity Log Combination
Authors: Aqivlera Robert 
Published: December 2007

JPT Forum articles are limited to 1,500 words including 250 words for each table and figure, or a maximum of two pages in JPT. A Forum article may present preliminary results or conclusions of an investigation that the present preliminary results or conclusions of an investigation that the author wishes to publish before completing a full study; it may impart general technical information that does not warrant publication as a full-length paper. All Forum articles are subject to approval by an editorial committee.
Letters to the editor are published under Dialogue, and may cover technical or nontechnical topics. SPE-AIME reserves the right to edit letters for style and content.

Introduction
A current technique for evaluating the pulsed neutron-resistivity combination involves crossplotting the capture cross-section, Sigma, as read from the log vs true formation resistivity, Rt, on an inverse-square-root scale. The data points must be from clean zones with a limited range of points must be from clean zones with a limited range of porosities. The Sigma - Rt crossplot generates a clean porosities. The Sigma - Rt crossplot generates a clean oil-water straight line with a slope equal to a R w (Sigma w - Sigma hy). Values of water saturation can be determined directly from this straight line.This paper presents a different approach for evaluating clean zones of a single lithology using the pulsed neutron-resistivity combination. The method has the same capabilities as the technique mentioned previously, plus the following advantages. plus the following advantages. 1. This method permits analysis in the presence of porosity variations. porosity variations. 2. The value of the porosity exponent, m, does not have to be assumed as 2.0.3. Under favorable conditions, the method allows us to estimate the value of the water saturation exponent, n, from logs alone.The procedure discussed here is inspired by the pattern recognition approach introduced by Pickett.

Theory
The fundamental equations for log analysis are
(1)
(2)
(3)
The basic equation for quantitative analysis of clean formations from pulsed neutron logs is
(4)
Solving for porosity we obtain
(5)
Combining Eqs. 2, 3, and 5 and taking the logarithm of both sides leads to
(6)
where
(7)
Analysis of Eqs. 6 and 7 indicates that a log-log crossplot of Rt vs Sigma - Sigma ma for zones that are 100% saturated with water must result in a straight line with a slope equal to -m, provided the values of a, R w, m, Sigma ma, and Sigma w are constant. If the value of Sigma ma is not known, this type of analysis allows us to determine Sigma ma by trial and error. In fact, if the value of Sigma ma is incorrect, it is impossible to obtain the desired straight line, and only curves result.Once the 100% water-bearing trend is established, we can create a family of parallel lines, each representing a value of water saturation.
JPT
P. 415
The Use of Resistivity-at-the-Bit Images and Annular Pressure While Drilling in Preventing Drilling Problems
Authors: Rezmer-Cooper Iain , Bratton Tom , Krabbe Helle 
Published: December 2007

Summary
The cost of well construction can exceed budget dramatically if drilling operations are plagued by wellbore-instability problems and excessive time and resources are needed to free stuck pipe, regain circulation, or clean the hole efficiently. Annular pressure while drilling has been recognized recently as one of the key downhole measurements for aiding real-time diagnosis of the condition of the wellbore and drilling fluids. In addition to conventional drilling-mechanics measurements, time-lapse logging-while-drilling (LWD) documents the dynamic change in measured properties during well construction. This can be essential in diagnosing wellbore failure, and the mechanism of failure, in addition to dynamic processes such as cuttings buildup.
An example from a horizontal well in the North Sea is used to illustrate how LWD resistivity images can be used in conjunction with annular-pressure-while-drilling measurements to detect the onset of drilling-induced fractures. Although the majority of azimuthal images have been acquired to understand the geology and petrophysics of reservoirs, the images usually contain features resulting from geomechanical processes.
Analysis of these features reveals important information for optimizing drilling and understanding the geomechanics of the well. Coupling resistivity images to the pressure measurement enables problem identification and correct remedial actions to optimize the drilling operation, for example, ensuring that swab and surge pressures are kept to a minimum, and correct hole-cleaning procedures are used to prevent irreversible formation breakdown.
Multiple Proppant Fracturing of Horizontal Wellbores in a Chalk Formation: Evolving the Process in the Valhall Field
Authors: Norris M. R. , Bergsvik L. , Teesdale C. , Berntsen B. A. 
Published: December 2007

Summary
Oil production from this chalk field has been improved significantly over the last 3 years using multiple proppant fractures placed from horizontal completions. Following early successes, the engineering effort focused on increasing value through engineering innovation and increased productivity. This paper describes, through case histories and field data, advances made in the design and execution of these completions over 13 wells in the Valhall field.
Wellbore completion activities and stimulation are performed now as a stand-alone process. Using specialized large-diameter coiled-tubing (CT) equipment allows ongoing drilling operations to be performed concurrently. This has reduced daily spread costs significantly while bringing wells on production in a much-reduced time frame. This lower cost environment also has allowed innovative field procedures to be developed resulting in further improvements such as proppant plugs for isolation between stimulation zones, novel bottomhole assemblies (BHA's) for perforating, and treatments using recycled proppant to minimize waste.
Productivity is the driver for economic success. Treatmentdesign requirements have evolved through laboratory testing to account for longer-term downhole-operating conditions below the bubblepoint while also improving initial conductivity. Field data to date through production logging operations have confirmed the hydrocarbon contribution from each fracture. This is used to validate the effectiveness of each treatment. Normalized well productivities continue to improve and the challenge is to maintain the rate of evolution through the improved application of new and existing technologies.