bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Hydrocarbon Histories of the Ivishak (Sadlerochit) Reservoir, Prudhoe Bay Field
Authors: Erickson J. W. , Sneider R. M. 
Published: December 2007

Summary
The Ivishak (sometimes referred to as the Sadlerochit) reservoir is the largest producing horizon in the Prudhoe Bay field. The field, located on the coastline of the Beaufort Sea, has been divided into eight zones with lower sections being deposited in low-energy, marine and delta-front environments and the remaining zones consisting of sandstones and conglomeratic units deposited by braided streams.1 Subsequent burial, structuring, and hydrocarbon emplacement resulted in a maximum accumulation 40 million years ago, with a hydrocarbon-column thickness of 2,080 ft. Continuing burial resulted in flattening and hydrocarbon spillage, resulting in the configuration at field discovery with a hydrocarbon-column thickness of 1,050 ft. Understanding the structural and hydrocarbon histories is key to understanding and calculating the gas-, oil-, and water-saturation distributions at the time of field discovery because some areas of the reservoir appear to have been in capillary equilibrium with the discovery oil/water contact, while structurally high portions of the reservoir appear to be in equilibrium with conditions at the time of maximum hydrocarbon accumulation.
Rock Types, Depositional History, and Diagenetic Effects, Ivishak Reservoir, Prudhoe Bay Field
Authors: Sneider R. M. , Erickson J. W. 
Published: December 2007

Summary
The present-day pore system of the Ivishak reservoir is the result of depositional and postdepositional processes. The pore system is a dual system characterized by intergranular porosity, enhanced by leaching, and intragranular microporosity. The combined interaction of deposition and diagenesis together with burial history has caused porosity, permeability, net pay, and water saturation to be highly variable areally and vertically.
Use of Neural Networks for Prediction of Vapor/Liquid EquilibriumKValues for Light-Hydrocarbon Mixtures
Authors: Habiballah W. A. , Startzman R. A. , Barrufet M. A. 
Published: December 2007

SummaryEquilibrium ratios play a fundamental role in the understanding of phase behavior of hydrocarbon mixtures. They are important in predicting compositional changes under varying temperature and pressure in reservoirs, surface separators, and production and transportation facilities. In particular, they are critical for reliable and successful compositional reservoir simulation. This paper presents a new approach for predicting K values with neural networks (NN's). The method is applied to binary and multicomponent mixtures, and K-value prediction accuracy is on the order of the traditional methods. However, computing speed is significantly faster.
A New Simple Method To Estimate Fracture Pressure Gradient
Authors: Rocha L. A. , Bourgoyne A. T. 
Published: December 2007

Summary
Projecting safer and more economic wells calls for estimating correctly the fracture pressure gradient. On the other hand, a poor prediction of the fracture pressure gradient may lead to serious accidents such as lost circulation followed by a kick. Although these kind of accidents can occur in any phase of the well, drilling shallow formations can offer additional dangerous due to shallow gas kicks, because they have the potential of becoming a shallow gas blowout leading sometimes to the formation of craters.
Often, one of the main problem when estimating the fracture pressure gradient is the lack of data. In fact, drilling engineers generally face situations where only leak off test data (frequently having questionable results) are available. This problem is normally the case when drilling shallow formations where very few information are collected.
This paper presents a new method to estimate fracture pressure gradient. The proposed method has the advantage of (a) using only the knowledge of leak off test data and (b) being independent of the pore pressure. The method is based on a new concept called "pseudo-over- burden pressure", defined as the overburden pressure a formation would exhibit if it were plastic. The method was applied in several areas of the world such as U.S. Gulf Coast (Mississippi Canyon and Green Canyon) with very good results.
Estimation of Recovery Factor in Light-Oil Air-Injection Projects
Authors: Fassihi M. R. , Yannimaras D. V. , Kumar V. K. 
Published: December 2007

Summary
In deep, high-pressure light-oil reservoirs, air injection provides several advantages compared with other improved recovery injection processes. The combination of rapid pressurization, spontaneous ignition, complete oxygen utilization, stripping of the light hydrocarbons [natural gas liquids (NGL's)], and near miscibility of the in-situ-generated combustion gases with the reservoir oil results in improved recovery. The availability of the injectant should allow wide application of air injection. Estimation of the recovery factor for this process is subject to uncertainties and requires history matching. To date, computer models have shown limited predictive capability owing to the complexity of the process. Also, an estimate of the fuel laydown at high pressure is not available.
In this paper, a method is proposed for estimating the recovery factor on the basis of the producing gas/oil ratio (GOR) of the field. The field results of two ongoing air-injection projects, Medicine Pole Hills Unit (MPHU) in North Dakota and Buffalo Red River Unit (BRRU) in South Dakota, are used to illustrate this technique. MPHU and BRRU are unique applications because they use high-pressure air injection into deep, high-temperature, low-permeability carbonate reservoirs producing light oils. The produced-gas analysis from MPHU is used to arrive at the fuel laydown and the H/C ratio of the fuel. This is the first time the fuel laydown has been estimated for a high-pressure air-injection project in a light-oil reservoir. Finally, the results of the produced-gas analysis are used to arrive at the NGL content of the effluent stream. The combined oil recovery and NGL production provide the basis for estimating the total recovery factor for this field. Such an estimate can be used by other operators to assess the economic viability of this process in their fields.
Assessment of Analysis of an Instrumented Drilling Jackup Conductor
Authors: Hamel Djamel , Robinson Richard , Stonor R. W. P. 
Published: December 2007

Summary
This paper presents an assessment of some of the results of an internationally funded joint-industry project to measure the dynamic behavior of a drilling conductor run from a large jackup platform operating in deep water at the North Sea. Three different elevations spanning the conductor were instrumented with environmentally protected strain gauges while the rig was operating. The objective was to gather data for selected storms for subsequent spectral and statistical analyses and to validate finite-element analysis (FEA) of a drilling-conductor system. The response amplitude operators (RAO's) from the analysis showed good agreement with measured RAO's. This agreement increases confidence in the validity of the loading and response calculation methods currently available for the design of drilling conductors. In the frequency analysis, the computed natural periods showed good agreement with those measured under different drilling conditions. Measurements showed that the natural frequency oscillation of the conductor was mainly in the first mode of vibration. In the time-domain analysis, the computed bending loads were found in good agreement with measured values, particularly at the middle and lower gauged levels. The analytical results showed that, for small waves, the dynamic amplification was substantial when comparing static and dynamic analytical techniques. However, for large design waves, the dynamic amplification was found to be small and the static analytical technique was found to be accurate in predicting environmentally induced loads.
Simultaneous Use of Ester and CO2 Sinale-Well Tracers
Authors: Wellington S. L. , Richardson E. A. 
Published: December 2007

Summary
This paper documents the consecutive and concurrent use of both ester and CO2 tracer chemistries in the same single-well test application. The simplicity of the CO2 system, which uses water-soluble-only injectants, and a no-soak/soak test sequence allowed determination of definitive residual oil saturation (ROS) values.
Operator/Contractor Teamwork is the Key to Performance Improvement
Authors: Robins K. B. , Roberts J. D. M. 
Published: December 2007

Summary
The contract strategies developed by the two major E&P companies operating in the North Sea emphasise teamwork between operator and contractors to achieve the common goal of maximising project value. These strategies have had significant repercussions across the whole industry.
This paper compares these strategies, concluding that although they are structurally different, they have the same fundamental objective. It describes the evolution of what these operators consider to be their "core business", with the resultant changing roles for both operator and contractor staff.
Several examples of results achieved through implementing these changes are described, highlighting the need for a structured performance measurement system to quantify the success of these initiatives. Finally the potential for even greater efficiency improvements through further industry wide cooperation is emphasised.
An Evolving Approach in the Analysis of Stress-Test Pressure-Decline Data
Authors: Middlebrook M. L. , Aud W. W. , Harkrider J. D. , Hansen J. T. 
Published: December 2007

Summary
Stress testing (microhydraulic fracturing) is recognized by the petroleum industry as the most direct method of determining the minimum in-situ (closure) stress for a given reservoir rock and the surrounding formations. In general, it is variations of in-situ stress between formations that dominates hydraulic fracture height growth and overall fracture geometry. Misleading interpretations of stress-test data (cased or openhole) can lead to significant errors in the prediction of stress contrast between the producing and bounding rock layers as well as an erroneous estimation of closure stress in the productive interval. In either case, hydraulic-fracture-treatment designs based on this information may not be designed optimally, and the subsequent interpretation of the fracturing treatment pressure response may not be correct. We present an evolutionary approach in the analysis of stress-test data that leads to more consistent results relating directly to actual fracture-treatment pressure responses. Although the emphasis in this paper is on cased-hole stress-test-data interpretation, the methodology presented is also applicable to openhole stress testing and larger-scale pump-in/shut-in (i.e. calibration or minifracture) pressure falloff responses.
Estimating Reserves and Success for a Prospect With Geologically Dependent Layers
Authors: Murtha J. A. 
Published: December 2007

SummaryA drilling prospect with several potential pay zones is modeled. Analytical arguments involving conditional probabilities reveal that geological dependence has no bearing on either the expected number of successful layers or the expected combined reserves. Monte Carlo simulation sheds light on the dispersion of the reserve distribution. A case study of an offshore Louisiana prospect with three layers illustrates the principles described. The general approach outlined in this model of layered pay zones can be applied to other types of prospects having multiple components that may be related such as fault blocks. Moreover, in addition to reserves, we can address other measures such as capital investment or completion costs.
Mechanical Skin Damage in Weils
Authors: Morales R. H. , Brown E. , Norman W. D. , DeBonis V. , Mathews M. J. , Park E. I. , Brown R. 
Published: December 2007

Abstract
This study describes and quantifies a mechanical skin damage resulting from the redistribution of stresses caused by drilling a well in a permeable material. The damage is localized within a cylindrical ring centered at the well axis. The stresses (and related positive skins) increase with depth, angle of inclination, and production time. They rapidly fade with lateral radial distance. The damage becomes insignificant at a distance greater than four times the borehole radius (or elastic/plastic interface radius).
Robust Technique for Real-Time Closure Stress Determination
Authors: Wright C. A. , Weijers Leen , Minner W. A. , Snow D. M. 
Published: December 2007

Summary
To achieve credible engineering estimates of fracture geometry, fluid efficiency, and potential risks of premature screen-out, the engineer must reliably history match the observed net-fracturing pressure. Measurement of net-fracturing pressure requires first, and foremost, a reliable estimate of the formation closure stress, to which the net pressure is referred.
This paper documents both the theory and several example field applications of a novel flow-pulse closure stress determination method. The flow-pulse technique requires only small changes in fracture treatment pumping schedule that can be accomplished at little to no extra cost, yet it allows a robust estimation of formation closure stress in real time. The flow-pulse technique involves pumping a small minifrac (usually with water) and then pumping small pulses (of about 5 bbl) of fluid during the pressure decline. There is a dramatic change in pressure response when flow pulses are pumped into an open fracture vs. a fracture that is already closed.
Simultaneous Measurements of Relative Permeability, Capillary Pressure, and Electrical Resistivity with Microwave System for Saturation Monitoring
Authors: Honarpour Matt M. , Huang David D. , Al-Hussainy Rati 
Published: December 2007

Abstract
Accurate relative permeability (kr) and capillary pressure (Pc) data are essential for predicting the performance of hydrocarbon reservoirs. Traditionally, kr and Pc are measured independently in different experimental systems, and rarely on the same samples under identical conditions. However, because these properties can be very sensitive to the same variables, simultaneous measurements are needed for consistency and for rigorous modeling. It is also important to have the capability to establish field-observed initial water saturations in laboratory tests because relative permeability and capillary pressure during imbibition rely on the values of the initial water saturations.
A novel apparatus has been constructed to allow simultaneous measurements of capillary pressure, relative permeability, and electrical resistivity on cores up to 2" diameter and 6" long. Fluid saturation profile is monitored by a state-of-the-art microwave technique. A microwave scanner moves along the core, and in-situ fluid saturation is calculated from the transmitted signal intensity. This method does not require tagging fluids which may affect wetting properties. The apparatus can reduce water saturation to a low initial value and can operate at moderate temperature, overburden stress, and fluid pressure. It is equipped with an in-line viscometer for continuous and accurate monitoring of oil viscosity. In this paper, the unique features of the apparatus is presented, along with some capillary pressure and relative permeability data measured simultaneously at elevated temperature and pressure for illustration.
Characterization of Reservoir Core using Computed Microtomography
Authors: Coles M. E. , Hazlett R. D. , Spanne P. , Muegge E. L. , Furr M. J. 
Published: December 2007

Abstract
X-ray tomography is often utilized to evaluate and characterize structural characteristics within reservoir core material systems. Generally, medical computed tomography (CT) scanners have been employed because of their availability and ease of use. Current spatial resolutions of conventional medical CT scanners have, however, not allowed their use in obtaining pore level characterizations for most core samples. Recently developed high resolution computed microtomography (CMT) using synchrotron radiation x-ray sources is analogous to conventional medical CT scanning and provides the ability to obtain three dimensional characterization of specimens with a spatial resolution on the order of microns. Application of this technique to the study of core samples provides excellent two and three dimensional high resolution description of pore structure and mineral distributions. Statistical and variogram analysis of the microtomographic images provide descriptors characteristic of the specific core material. Pore space interconnectivity is accurately characterized and visualized. Pore level endpoint saturation microtomograms obtained during a core flood of a sandstone sample are presented.
On the Sensitivity and Spatial Resolution of Transient Pressure and Tracer Data for Heterogeneity Characterization
Authors: Datta-Gupta Akhil , Vasco D. W. , Long J. C. S. 
Published: December 2007

Summary
This paper examines the sensitivities of interwell tracer and transient-pressure response to spatial distribution of permeability heterogeneity. On the basis of these sensitivities, we describe a formalism to quantify the resolution and spatial averaging associated with estimates of permeabilities derived through inversion of tracer and/or pressure data. The resolution is a measure of the effectiveness of the data in estimating local-scale (gridblock) permeabilities. The spatial averaging kernels quantify the inherent averaging associated with our estimates because of limited data or sampling. By examining the resolution and averaging kernels as a function of various data types, we can evaluate quantitatively the relative importance of tracer vs. pressure data for heterogeneity characterization and the improvement in estimates obtained by combining the data types. We illustrate the concepts by application to transient-pressure and tracer response from five-spot patterns and also to an experimental tracer response from a well-characterized slab of Antolini sandstone. Tracer data is found to yield much better resolution compared to transient-pressure response. Also, both transient-pressure and tracer data appear to resolve barriers to flow better rather than channels to flow.
Full-Field Reservoir Modeling of Central Oman Gas-Condensate Fields
Authors: Leemput L. E. C. van de , Bertram D. A. , Bentley M. R. , Gelling R. 
Published: December 2007

SummaryGas reserves sufficient for a major export scheme have been found in Central Oman. To support appraisal and development planning of the gas and condensate fields, a dedicated, multidisciplinary study team comprising both surface and subsurface engineers was assembled. The team fostered a high level of awareness of cross-disciplinary needs and challenges, resulting in timely data acquisition and a good fit between the various work activities. A field-development plan was completed in March 1994. The foundation of the subsurface contributions was a suite of advanced full-field reservoir models that were used to do the following.Provide production and well requirement forecasts. Quantify the impact of uncertainties on field performance and project costs. Support the appraisal campaign. Optimize the field-development plan. Derive recovery factor ranges for reserves estimates.The models were constructed early during the study, initially with general data with large uncertainty ranges and gradually refined with new appraisal data. This ultimately resulted in more than 20 full scenarios, quantifying and ranking the remaining uncertainty ranges. Geological/petrophysical uncertainties were quantified by use of newly developed, 3D probabilistic modeling tools. An efficient computing environment allowed a large number of sensitivities to be run in a timely, cost-effective manner.The models also investigated a key concern in gas-condensate fields, well impairment caused by near-well condensate precipitation. Its impact was assessed by use of measured, capillary-number-dependent, relative permeability curves. Well-performance ranges were established on the basis of equation-of-state (EOS) single-well simulations and translated into the volatile-oil full-field models with pseudorelative permeability curves for the wells. The models used the sparse available data in an optimal way and, as part of the field-development plan, sustained confidence in the reserves estimates and the project, which is currently in the project specification phase.
Mass Transfer From Bypassed Zones During Gas Injection
Authors: Burger J. E. , Mohanty K. K. 
Published: December 2007

SummaryGasflooding in oil reservoirs leads to bypassing of the oil as a result of gravitational, viscous, and/or heterogeneity effects. A part of the bypassed oil can be recovered by the flowing solvent because of crossflow/mass transfer. In this work, we studied the effect of the orientation of the bypassed region and the enrichment of the solvent on the mass transfer. Laboratory-scale mass transfer and coreflood experiments were conducted. Numerical simulation was used to identify the role of the different mechanisms. Results indicate that the mass transfer is the least for the vertical orientation, intermediate for the inverted orientation, and the highest for the horizontal orientation. The mass transfer increases with enrichment for all orientations. Liquid-phase diffusion controls vertical-orientation mass transfer for the fluids studied. Gravity-driven flow contributes the most to the mass transfer in the horizontal and inverted orientations. Oil recovery in horizontal gasfloods can be nonmonotonic with enrichment. Multiphase flow in the near-miscible floods leads to less gravity override compared with the first-contact-miscible (FCM) floods.
Capillary Entrapment Caused by Small-Scale Wettability Heterogeneities
Authors: van Lingen P. P. , Bruining Johannes , van Kruijsdijk C. P. J. W. 
Published: December 2007

SummarySmall-scale heterogeneities are abundant in oil reservoirs. It is well known that these heterogeneities can reduce the displacement efficiency of immiscible flooding because of capillary entrapment of oil. A typical heterogeneous facies is the laminated crossbed set with alternating high- and low-permeability laminae. Apart from this heterogeneity in grain size, the wettability of the laminae can also differ. The laminae can contain different minerals with different wetting characteristics, and wettability can be affected by adsorption of hydrocarbons to the grain surface. In this paper we focus on the effects of wettability on the entrapment. We describe a procedure that allows the reader to quantify the trapped oil saturation depending on absolute permeability, relative permeability, and capillary pressure curves of the foreset laminae, on the basis of a simplified crossbed geometry. The example calculations show the sensitivity of various parameters with respect to the magnitude of trapping.