bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent Safety Work on the Ekofisk Field
Authors: Saxvik Bjørn 
Published: March 2016

Abstract
The Piper Alpha disaster in July 1988 was a painful reminder to all personnel involved in the offshore industry, and emphasized the importance of giving safety the first priority. This paper will concentrate on work initiated within Phillips Petroleum Company Norway (PPCoN) because of the Piper Alpha accident.
PPCoN is the operator of more than 20 platforms in the Greater Ekofisk Area on the Norwegian Continental Shelf. Many of these platforms were designed 15 years ago, and have been less modified to meet revised operational requirements. We are therefore operating platforms which are in a similar period of life as Piper Alpha, even though there are differences. PPCoN is therefore very interested in learning as much as possible from the accident.
Environmental Protection Offshore the Netherlands
Authors: Scholten P. A. , Van Der Ham P. J. M. , Hdijnen W. G. J. 
Published: March 2016

Abstract
The principal environmental impact of the exploitation of oil and gas on the Netherlands Continental Shelf (NCS) is associated with the discharge of cuttings containing residues of oil containing drilling mud and of oil containing production water. In 1986, these discharges amounted to a total of about 4,700 tons of oil being discharged into the sea, that is about one quarter of the oil discharged by all the platforms in the North Sea. The results of monitoring round locations on the NCS where drilling operations took place before 1987 lead to conclusions which correspond with British investigations in the southern part of the North Sea.
Elevated oil concentrations in the sediments are found at distances of up to 750–1000 metres from the drilling locations. Within a distance of 50–250 metres, concentrations occur of 100 to 10,000 times the background level. In these areas, distinct effects on the seabed fauna are also noticeable: a substantial reduction if not a total disappearance of the sea-bed fauna can be observed.
The oil pollution is not distributed homogeneously: as a result of water currents and of spread caused by sea bottom fishing, a patchy pattern has been created.
Specifics of Horizontal Drilling in the Zuidwal Gas Field
Authors: Legris B. , Nazzal G. 
Published: March 2016

Abstract
In the gas field of Zuidwal, situated in one of the most environmentally sensitive areas of the Netherlands, a total of nine wells were drilled, three of which were horizontal. Due to the nature of the location, and its gas-bearing formation with layers of different reservoir characteristics, the operator adopted special programs and procedures, which provide the focus of this paper.
A Subsea Reeled Tubing Service Unit
Authors: Cobb C. C. , Headworth C. S. 
Published: March 2016

ABSTRACT
Recent trends in offshore field development have been toward subsea completions, especially in the North Sea. It is estimated that the number of subsea wells in the North Sea will double by 1994. Since subsea wells are often completed in the same formations as conventional offshore wells and completion designs are the same, downhole service requirements for subsea wells are generally the same. Semi-submersible rigs using tensioned risers have offered the only practical means of performing vertical intervention services such as wireline and reeled (coil) tubing.
A subsea reeled tubing system (SRTS) has been designed and manufactured that offers a more economical means of performing a range of reeled tubing services on subsea wells. The SRTS is operated from a diver support vessel (DSV) or other relatively small vessels in lieu of a rig which effects a considerable savings in cost and time. A tensioned riser is not required with the SRTS.
This paper describes the SRTS in detail and discusses the reeled tubing services offered by the unit. Safety features and operational procedures are also discussed.
Subsurface Safety Valve Developements for Gaswells
Authors: Heijnen W. H. P. M. , Kolthof W. J. , ter Horst B. H. 
Published: March 2016

ABSTRACT
The various types of subsurface Safety valve systems are described together with NAM's resoning for selecting present and future safety valve systems. A design review technique was applied to assist in identifying the possible weak points and also providing a basis for selection of the most optimal safety valve system taking Petroleum engineering, operational and mechanical engineering into consideration. The design review on the hydraulicaly operated flapper wireline retrievable flapper valve did not reveal any major weak points apart from the limited test pressure on the landing nipple. The design review process is explained and suggestion for a future developments with respect to type testing, freezing of designs and possible subsequent certification is adressed.
Design and Application of a Computer-Aided Data Collection System for Displacement Studies
Authors: Kohler T. E. , Ertekin T. , Kohler J. L. 
Published: March 2016

ABSTRACT
Collection of data during an experiment is sometimes tedious and can even be close to impossible. When performing a displacement study, several variables are often monitored with time. Some of these monitored variables might include injection pressure, core pressure or temperature, or water-oil ratio. These data points may need to be collected at specific times, at high rates, or at odd intervals. To simplify the data collection process, an economical data acquisition system was designed. The proposed system monitors any or all of the above variables as per the experimenter's specifications of time and frequency.
The data acquisition system described in this paper was designed to operate on any IBM-PC* or close compatible computer environment. The programs comprising the data collection part of the system are general enough such that only the transducer type and constants need to be known. Therefore, any pressure transducer or any thermistor can be used. This approach allows the system to be used for more than just displacement studies. Once an experiment is started, the experimenter has access to all data collected as either graphs or lists. This availability facilitates the detection of trends and/or problems.
The proposed data acquisition system has been tested and used successfully in various experimental environments. Discussion and data are provided for three specific experiments to highlight the unique aspects of the system designed. First, the effect of steep temperature gradients on two-phase relative permeability characteristics was investigated using this system. Both pressure and temperature variations along the core were measured and recorded as functions of time.
Next, the system was used to measure the rate of propa-gation of a pressure pulse through a slim tube. This pressure pulse rate was then used to calculate the permeability in a tight sand column. Finally, the rate of mud filtrate invasion has also been monitored with this same system. All of these examples demonstrate the capabilities and versatility of the proposed data acquisition system.
Bass Strait: Production Decline Mitigation
Authors: Stewart D. J. , Goodacre J. , Cruickshank C. 
Published: March 2016

ABSTRACT
Since 1985 Bass Strait oil production has declined by over 100 kSTB/D (16 ML/d) to an average of 364 kSTB/D (58 ML/d) in 1988. To mitigate this decline Esso Australia has undertaken a coordinated program aimed at realising the full production potential of existing reserves and facilities. This program centres on three fronts; major projects such as gas lift and waterhandling, a workover program and the removal of facility constraints. Over the next 4 years this rate enhancement activity is currently forecast to offset declining production rates by an average of 60 kSTB/D (10 ML/d).
Currently over 60% of available oil wells are capable of being gas lifted, including two wells with average angles in excess of 70°, and it is planned to increase this number to over 75% in the near term. The strong water drive characteristics of Bass Strait reservoirs has resulted in increased formation water production. Waterhandling facilities have been installed to maximise production levels. Current waterhandling capacity is around 300 kSTB/D (48 ML/d) with half being achieved through use of hydrocyclones which provide improved portability and operating flexibility compared with conventional waterhandling equipment.
Since mid 1987 an average of over 4 workovers per month have been completed in an intensive program to achieve the full potential from all wells. This has been achieved through the use of alternative options to the conventional tubing pull workovers of the past. Extensive use has been made of coil tubing units (CTU), concentric rigs and a jack-up rig instead of conventional platform rigs, thus reducing costs and returning wells to production faster.
Platform facilities have been optimised through close liaison between operations and engineering personnel to locate and remove production constraints where possible. Integration of facilities for new developments has allowed production from existing reservoirs to be increased.
Investigation of the Shape Factor Used in the Dual-Porosity Reservoir Simulator
Authors: Ueda Y. , Murata S. , Watanabe Y. , Funatsu K. 
Published: March 2016

ABSTRACT
Simulation of naturally fractured reservoirs has been one of the topical research subjects and several methods have been proposed as results of these research efforts. Since a fine grid model of an actual reservoir would be impossible to run even with today's advanced computers, all these methods employ dual porosity or dual porosity-dual permeability representations of fractured reservoirs. They differ in the treatment of fracture/matrix fluid transfer. None of them, needless to say, is omnipotent and new approaches continue to appear in the literature.
The new gravity model that the authors and co-workers have developed is one of such approaches. The vertical equilibrium is assumed to define the transition zone in the matrix block in order to better express the transient saturation profile, which is the manifestation of the combined effects of viscous, capillary, and gravity forces. The fracture/matrix fluid exchanges in the lateral and vertical directions are calculated separately using, with some modifications, the Kazemi type shape factor, σ.
This paper reports the results calculated by this new gravity model for the two imbibition cases of advancing water levels in fractures. These calculation results are compared with those obtained from the experiments or fine grid simulations. Physical meanings of the shape factor, σ, are discussed on the basis of this comparison.
Developing Complete Resistance to Stress Corrosion Cracking in Nonmagnetic Drilling Tools
Authors: Kopecki D. S. 
Published: March 2016

ABSTRACT
Stress corrosion cracking (SCC) in nonmagnetic drill string components made of austenitic stainless steel alloys has been a long-standing industry-wide problem. Three currently available technologies, each capable of producing a zero frequency of SCC, are presented in this paper.
The application of compressive residual stress to surfaces exposed to drilling mud is evaluated as the principle technology for developing SCC resistance at present. In addition, two classes of SCC-resistant alloys are examined: The first, a small group of stainless steel alloys with significant nickel, is shown to have functional as well as economic disadvantages despite providing adequate resistance to SCC. A second class of alloys, only now emerging from the laboratory, probably exhibits electrochemical characteristics which fundamentally prevent stress corrosion cracking.
The examination of various aspects of the application of these three technologies will show that complete, practical solutions to SCC of nonmagnetic tools are imminent. Also included are some details on the application of compressive residual stress to used tools with sensitized microstructure.
A New Method for Predicting Fracture Propagation Pressure From MWD or Wireline Log Data
Authors: Holbrook P. W. 
Published: March 2016

ABSTRACT
A new approach has been developed for predicting fracture initiation and propagation pressure from MWD or wireline log data. The technique combines well established principles of rock mechanics and petrophysics to calibrate earth stresses and pressure to rock properties. Real-time pressure predictions are based upon MWD data derived while drilling the well rather than depth from a regional average or planning well.
Fracture propagation pressure (Fp) is the sum of pore pressure (P) and the effective horizontal stress (σh) during fracturing (Fp = p + σh). Pore pressure is first determined as the difference between overburden(S) and effective vertical stresses (σy) from the relationship (P=S-σY). This rock mechanics approach is fundamentally different from the "normal" (Pn) and "excess" (Pe) additive fluid pressure approaches (P=Pn+Pe) for predicting pore pressure (P). The overburden calculation accounts for the water column, average rock densities above the measured interval, and calculated rock densities within the measured interval Effective vertical stress (σV) is calculated for all lithologies in the sand-shale continuum using empirically derived Power Law expressions of lithology (v-shale) and porosity (Φ).
The new fracture pressure prediction approach is an extension of the effective stress concept using Drucker Prager failure criteria. Leakoff test data has been used to define effective stress-rock properties limits for fracture initiation and propagation pressures. The new approach is shown to be about four times more accurate than traditional approaches that determine effective horizontal stress as a function of depth.
The calibration data and three log examples are shown to demonstrate the accuracy of the technique. The use of Fracture Pressure logs before or during drilling could have prevented lost circulation in two cases and the setting of unnecessary casino in the third.
Salinity and Saturation Effects on Shaly Sandstone Conductivity
Authors: Argaud M. , Giouse H. , Straley C. , Tomanic J. , Winkler K. 
Published: March 2016

ABSTRACT
Although a considerable amount of effort has been expended on the subject, the interpretation of shaly sandstone resistivities often proves problematic. Since the amount of high quality experimental data is somewhat limited, a joint research project was conducted to acquire more laboratory data and to evaluate the data in terms of new and existing theoretical models.
This project consisted of two sets of experiments:
conductivity measurements on fully brine saturated rock samples investigating the effect of changes in salinity and/or type of cations; resistivity index measurements at decreasing water saturation and various salinities achieved by capillary drainage.
The second set of experiments will be presented in this paper. Supporting data consist of mercury porosimetry, SEM analysis, and Qv as measured by chemical titration, membrane potential and Co vs Cw intercepts.
Our data on resistivity index show that commonly used shaly-sand models such as Waxman-Smits or Dual-Water have difficulty predicting saturation when clay conductivity is dominant. This can occur when clay content is high or when brine conductivity is low. Models that incorporate additional geometrical information about the conducting paths, such as the Schwartz-Sen model or the DC model of Giouse and Argaud, do a better job of predicting the experimental results.
The Effects of Depositional Environment on Petrophysical Properties of Mesaverde Reservoirs, Northwestern Colorado
Authors: Lorenz J. C. , Sattler A. R. , Stein C. L. 
Published: March 2016

ABSTRACT
Petrophysical (rock and reservoir) properties of Mesaverde strata in northwestern Colorado change significantly with variations in both lithology and depositional environment. The Mesaverde Group at the U.S. Department of Energy's Multiwell Experiment site contains strata that were deposited in shallow marine, lower and upper delta plain, and fluvial environments. The detrital compositions of the original sands in these environments were similar, but differing depositional and diagenetic modifications produced zones of differing sandstone mineralogy and texture. Different mineralogies in turn cause significant differences in reservoir porosities and permeabilities, and in rock properties such as Young's modulus, Poisson's ratio, fracture toughness, capillary pressure, and compressive and tensile strength.
Correcting the Induction Log for Dip Effect
Authors: Barber T. D. , Howard A. Q. 
Published: March 2016

Abstract
Determining the true formation resistivity Rt from induction logs in the presence of either dip or well deviation is complicated by the distortions in the log introduced as the apparent dip angle increases. This effect is well documented. The effect on traditional ID logs is to make shoulder effect somewhat worse, causing resistive beds to read even lower. The effect of dip on Phasor* induction logs is more readily apparent, since the shoulder effect has been removed. As the dip angle increases, the Phasor ID logs read more nearly like the traditional ID log.
A correction algorithm has been developed which produces the correct curve shape and resistivity reading in resistive beds, but which does not attempt to reduce the apparent thickening of resistive beds. The charge-buildup effects which lead to this apparent thickening are quite nonlinear, depending strongly on the conductivity contrast across the boundary. The increase in shoulder effect with dip angle, however, is approximately linear in both contrast and conductivity magnitude. This near-linearity allows a correction algorithm to be developed using the inverse-filter method.
The algorithm as currently developed gives greatly improved resistivity accuracy in resistive beds at angles up to 70°. Tests on a large number of computed logs confirm the apparent linearity of the main part of the dip effect.
Optimizing Design and Performance of an MWD Resistivity Sensor
Authors: Turvill J. A. , Evans H. B. , Hebel J. B. 
Published: March 2016

Abstract
Design specifications of any MWD resistivity sensor are constrained by the sensor being part of the drill string and by the resistivity environment in which the system must operate. Several alternative designs were modeled using Boundary Element Method software, running on a PC. Sensitivity of the device measurement parameters to variations in the system configuration was obtained by modeling and physical testing.
The design of the sensor, based on model results, incorporates several unique features including a software control system that may offer significant operational benefits.
The resulting guarded current resistivity device (GCR) has a diameter of investigation in the formation slightly less than a LLS under the same conditions of formation to mud resistivity ratios, Rf/Rm, ranging from 0.1 to 1000. For values of Rf/Rm between 0.7 and about 11,000, the borehole correction factor for the 6.75" tool is within 10 percent in boreholes of 8.5" to 9.875" (0.22 to 0.25 m) diameter. Calculation and field tests indicate that formation resistivity can be resolved in beds as thin as three inches (0.08m).
Test well data were used to validate the model results and to confirm the operating parameters of the sensor. Actual sensor performance was evaluated downhole using a special test configuration which provided a continuous bi-directional link to the surface permitting pipe movement, circulation and drilling.
Formations having a wide range of resistivities and lithologies were logged with the MWD system. Relogging with muds of different resistivity, yielded comparisons with the modeled sensor response over a variety of borehole, formation and operating conditions. Wireline logs and other data from the same well intervals were the basis for a more detailed evaluation of the resistivity sensor response.
A New Approach to Modeling Miscible Displacement Tests
Authors: Wu R. S. , Batycky J. P. , Harker B. C. 
Published: March 2016

Abstract
To develop a design basis for water-alternate-gas miscible flooding with hydrocarbon solvents in two of Esso Resources Canada Limited's carbonate reservoirs, a series of waterflood and tertiary solvent miscible flood core tests were conducted using restored-state composite cores. Because of the major differences in fluid compositions and properties, the tests provided insights into the physics as well as quantified the impacts of water/solvent ratio (WSR), displacement rates and water blockage on ultimate recovery, oil recovery rates and asphaltene precipitation.
In both reservoirs, it was observed that water blocking was not significant even at water/solvent ratios as high as 5. Ultimate residual oil saturations that resulted in the tertiary miscible floods were dependent on the amount of asphaltene precipitation. In addition, when it occurred, permeability reduction due to asphaltene precipitation showed the largest effects under pure solvent injection conditions.
Simulations of each waterflood and the subsequent tertiary floods using the Tqdd-Longstaff mixing parameter model were conducted, and led to a methodology that enabled both oil recovery and pressure drop data to be matched. It was possible to apply the waterflood relative permeabilities to match the tertiary flood performances. For one of the reservoir fluids that was characterized by the larger amount of asphaltene precipitation, a new asphaltene precipitation model was developed that provided additional quantification of the permeability reduction process.
Capillary-Gravity Equilibria for Hydrocarbon Fluids in Porous Media
Authors: Lee S-T. 
Published: March 2016

ABSTRACT
A theory and a general formulation have been developed to describe the influences of gravitational and capillary forces on reservoir fluid PVT properties and phase behavior. The theory assumes thermodynamic equilibrium for the fluid system and makes use of the Leverett J-function concept to approximate the in-situ pore curvature as a function of wetting saturation at a given height in the reservoir. The general formulation then permits interpretation and prediction of fluid phase and compositional variations in the capillary transition zone and beyond.
The effects of capillarity (interfacial curvature) and gravity on reservoir fluid PVT and VLE were investigated, for a gas-condensate system and assuming different curvature functions. It is shown that the interfacial curvature has no practical effect on fluid PVT and VLE for typical sand packings used in the laboratory. However, for in-situ reservoir conditions, it is possible to have quite high interfacial curvature with pore radius in the order of about 1 micron. Under such condition, the capillarity effect was found to become appreciable. A lower reservoir temperature would also make the capillarity effect more pronounced.
A second example was presented to show the variations of composition and saturation of the gas-condensate system above the gas-oil contact. It is shown that the capillary behavior of the reservoir rock controls the oil saturation variation above the gas-oil contact.