bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Tools Target Oil-Quality Sweetspots in Viscous-Oil Accumulations
Authors: Smalley P. C. , Goodwin N. S. , Dillon J. F. , Bidinger C. R. , Drozd R. J. 
Published: December 2007

Summary
Shallow oil fields frequently contain oils that not only have low oil gravity and high viscosities, but are also highly variable in terms of these properties. It is thus crucial to gather sufficient oil-quality data to sample a statistical cross section of the oil population. This paper describes how oil gravity and dead-oil viscosity can be predicted from geochemical parameters that can be measured on core or sidewall core samples, thus allowing oil samples to be accessed with greater spatial coverage than could reasonably be achieved with conventional fluid sampling. This technique is demonstrated on cored wells from the large Schrader Bluff viscous oil accumulation in Milne Point, Alaska. An oil can inherit a particular oil gravity or viscosity for a variety of causes. Consequently, spatial variations in such bulk-oil properties can be difficult to map empirically simply by contouring data because more than one controlling factor may be operative. A major step forward in fluid mapping is to identify and quantify these controls and map the controls. In Schrader Bluff the controls were discovered to be the degree of biodegradation and the presence of an in-mixed second charge of (light) oil. Variations in these processes can be tracked with geochemical parameters and mapped with a much greater degree of certainty than the bulk-oil properties. The resulting individual maps may then be combined to predict oil gravity and viscosity. Conceptual models exist for these processes, opening the possibility of model-driven prediction of oil properties and sweetspots in areas away from well control.
Salinity, Temperature, Oil Composition, and Oil Recovery by Waterflooding
Authors: Tang G. Q. , Morrow N. R. 
Published: December 2007

Summary
The effect of aging and displacement temperatures and brine and oil composition on wettability and the recovery of crude oil by spontaneous imbibition and waterflooding has been investigated. This study is based on displacement tests in Berea sandstone with three crude oils and three reservoir brines (RB's). Salinity was varied by changing the concentration of total dissolved solids (TDS's) of the synthetic brine in proportion. Salinity of the connate and invading brines can have a major influence on wettability and oil recovery at reservoir temperature. Oil recovery increased over that for the RB with dilution of both the initial (connate) and invading brine or dilution of either. Aging and displacement temperatures were varied independently. For all crude oils, water wetness and oil recovery increased with increase in displacement temperature. Removal of light components from the crude oil resulted in increased water wetness. Addition of alkanes to the crude oil reduced the water wetness, and increased oil recovery. Relationships between waterflood recovery and rate and extent of oil recovery by spontaneous imbibition are summarized.
Material-Balance Calculations in Tight-Gas Reservoirs: The Pitfalls of p/z Plots and a More Accurate Technique
Authors: Payne David A. 
Published: December 2007

Summary
Through the use of theoretical and field examples, the potentially large errors associated with use of straight-line p/z decline (tank) analysis to assess gas in place (GIP) and reserves in tight-gas reservoirs are illustrated. The basic tank assumption that reservoir pressure gradients are small can be violated, even with long shut-in times. It is also demonstrated that a reasonably-straight-line p/z decline does not necessarily indicate that the reservoir behaves as a tank. The communicating reservoir (CR) model is presented as a simple, yet much more accurate, method of performing materialbalance calculations in tight reservoirs. The results of the application of the CR model to the Waterton gas field are used to illustrate the success and large impact that can be obtained by examining the pressure behavior more closely than simply plotting p/z.
Effect of Wafer Saturation on Oil Recovery by Near-Miscible Gas Injection
Authors: Wylie Philip , Mohanty Kishore K. 
Published: December 2007

SummaryDuring gas injection, bypassing of oil is common because of gravitational, viscous, and/or heterogeneity effects. The oil in the bypassed regions can be recovered through enhanced flow and mass transfer between the bypassed region and the injectant gas. Previously, experiments in our laboratory have been carried out to evaluate the effects of phase behavior and capillary crossflow in near-miscible gasfloods; however, these studies were conducted in the absence of water. In this paper, we evaluate the effects of water saturation on oil bypassing and the rate of mass transfer from the bypassed zones. Injectant gases are first-contact miscible (FCM), multicontact miscible (MCM), or submiscible with the bypassed oil. Gasfloods are conducted in different orientations with different levels of water saturation. Mass-transfer experiments are carried out to isolate and investigate mass-transfer mechanisms. Results indicate that oil recovery from vertical, submiscible gasfloods is not influenced by water-saturation level. Horizontal gasfloods showed evidence of less gravity override in the presence of water. The mass-transfer experiments showed that recovery increases with enrichment and is reduced by the presence of water. Effective diffusion coefficients are estimated as functions of water saturation and enrichment.
The Successive Displacement Process: Oil Recovery During Blowdown
Authors: Irwin D. D. , Batycky J. P. 
Published: December 2007

Summary
Much of western Canada's conventional crude oil occurs in vertically continuous reefal carbonate structures. A common strategy has been to support oil production through downward vertical gas displacement. The gravity-stable displacement yields excellent conformance and high oil recoveries, with typical residual levels of 20% pore volume (PV). Once the oil zone has been depleted, leaving only a sandwich loss, the pools enter a blowdown phase to produce the gas cap from the top of structure. During the blowdown phase, if there is an underlying aquifer, the oil sandwich is displaced upward into the previously gas-displaced oil zone, trapping gas. Owing to the presence of the trapped-gas saturation, the remaining oil saturation in this zone, is reduced to near miscible levels (10 to 15% PV) as it is displaced by the underlying water, mobilizing incremental oil equal to 5 to 10% PV. When an aquifer is not present, bottomwater injection can be applied to ensure displacement through the entire gas-displaced oil zone. The successive displacement process (SDP), as this tertiary waterflood concept has been named, has been confirmed with full-diameter reservoir-condition core tests on carbonate cores in the laboratory. Observation from the initial stages of a full-field SDP application in Imperial Oil's Bonnie Glen reservoir after approximately 4 years of operation provides further encouragement, with performance indicating a reduction in the oil residual of 5 to 6% PV.
Monitoring and Analysis of ECP-lnflation Status Using Memory-Gauge Data
Authors: Gai Huawen , Elliot Graname 
Published: December 2007

Summary
The current surface instrumentation for monitoring the external-casing-packer (ECP) -inflation status has been identified as unsatisfactory, causing a significant degree of uncertainty in the evaluation of ECP performance. Coupled with some unreliable practices in the installation process relating to the use of the instrumentation, data interpretation is often difficult.
To combat the inaccuracy of surface measurement, memory gauges have been used for the first time as a retrospective tool to monitor ECP status downhole in west Shetland. The memory gauges, which are mounted on the workstring close to the ECP, remove the damping effect of the fluid column in the workstring, and are capable of measuring the squeeze pressure below the ECP caused by inflation. It is demonstrated in these operations that the following have been achieved.
• ECP status has been identified unambiguously and reliably in several wells.
• Some problems in job design have been identified, such as hydraulic lock (which may result in partial inflation) and incorrect setting of pressure shear-pin levels for inflation, leading to the formation being fractured.
• Insight has been gained in pipe-movement-induced swabbing and pressure surge, which act adversely on the formation. Certain information on the mud (such as solid settlement and pressure/volume relations) was also obtained.
• Valuable data was gained (both from the memory gauges and the surface gauges) that were a cornerstone for setting certain guidelines in interpreting ECP status by surface instrumentation.
This paper presents a detailed analysis of the data with examples and case histories. Key considerations in operations, lessons learned, and recommendations are discussed before the conclusions are reported.
Experimental and Modeling Studies of Two-Phase Flow in Pipelines
Authors: Manabe Ryo , Tochikawa Tetsuro , Tsukuda M. , Arihara Norio 
Published: December 2007

Summary
The objectives of this study are to develop and evaluate a mechanistic model for gas/liquid two-phase flow in pipelines.
A mechanistic model has been developed by combining currently available models and correlations. The approach of the modeling study was based on the work by Xiao et al.1 Modifications have been made on the annular flow model by implementing the currently developed film-thickness-distribution model.
An experimental database has been developed for model evaluation. Seventy-five runs of steady-state air/water flow tests in horizontal and slightly inclined pipes were conducted using a large-scale experimental facility. The experimental program was set up in a wide range of experimental conditions to cover the intermittent, dispersed bubble, and annular flow patterns.
An evaluation of the model was carried out for each flow pattern, namely, intermittent, dispersed bubble, and annular flow. The comparisons between the measured and calculated pressure drops show good agreement for each flow pattern. Also, overall evaluation revealed that the proposed model provided the best performance among the commonly used empirical correlations, such as Beggs and Brill,2 Mukherjee and Brill,3 and Dukler et al.4
Wettability Changes Induced by Adsorption of Asphaltenes
Authors: Yan Jienian , Plancher Henry , Morrow N. R. 
Published: December 2007

Summary
Asphaltene fractions were precipitated from two crude oils (designated as Prudhoe Bay '95 and Wyoming '95) by addition of n-hexane. A solution of 250 mg/L of asphaltenes in toluene was used to induce wettability changes in Berea sandstone cores by flow of asphaltene solutions through the core. Concentration of asphaltenes in the effluent was measured by ultraviolet (UV) absorbance. Wettability changes were assessed from measurements of the rate of spontaneous imbibition for changes in initial water saturation and brine composition. Water wetness decreased markedly with increase in ionic strength, increase in cation valency, and decrease in initial water saturation. For comparable conditions, changing the brine anions (chloride, nitrate, carbonate, and sulphate) caused lesser but fairly consistent changes in wetting. Wetting changes induced by asphaltenes from the Wyoming '95 crude oil were always higher than for those prepared from the Prudhoe Bay '95 crude oil. Water-flood recoveries for NaCl, CaCl2, and AlCl3 brines (0.09 M) increased with decrease in water wetness, with recovery reaching a maximum at an Amott wettability index of about 0.2. This result agrees with results reported previously for wettability changes induced by adsorption from crude oil.
Parallel Finite Element Simulation of Miscible Displacements in Porous Media
Authors: Coutinho Alvaro L. G. A. , Alves José L. D. 
Published: December 2007

Abstract
In this work, parallel finite element techniques for the simulation of miscible displacements in porous media are addressed. The pressure equation is approximated by Galerkin's method and the velocity field computed through a post-processing approach to recover the required accuracy. The concentration equation is approximated in space by the Streamline Upwind Petrov Galerkin (SUPG) plus a discontinuity-capturing operator. The resulting semi-discrete equations are approximated in time by a predictor-multicorrector algorithm. To increase the robustness of our solution scheme, the feedback control theory is used to select the proper time-step. The pressure, velocity and concentration linear systems of equations are solved with parallel element-by-element iterative techniques. Performance measurements on two different machines, the CRAY Y-MP and the CRAY C90, for a five-spot pattern with high mobility ratio on random heterogeneous media are presented to show that the numerical techniques employed are accurate and result in a fast code.
Viscosity Reduction Of Hydraulic Fracturing Fluids Through Enzymatic Hydrolysis
Authors: Tayal Akash , Kelly Robert M. , Khan Saad A. 
Published: December 2007

Abstract
High viscosity formulations of guar are used as fracturing fluids to enhance oil and gas production. Following fracturing, these fluids are hydrolyzed and flushed out of the well to provide outflow for oil or gas. Enzymes offer an effective and environmentally benign method for hydrolyzing the guar to a low viscosity fluid. In this study, we used steady shear rheometry to elicit fundamental information on the capabilities and limitations of enzymes. The effect of commercial and new thermostable enzymes on polymer viscosity was investigated in terms of process variables such as temperature of hydrolysis, pH of solution and enzyme concentration. The commercial enzyme was most effective in degrading the guar at slightly acidic conditions and up to 60°C. Above 60°C, the extent of hydrolysis of guar solutions decreased. With increasing temperature, enzymatic activity increased but enzyme stability decreased and this balance was critical in determining the extent of viscosity reduction. Experiments using preheated enzyme also revealed lower viscosity reduction, suggesting that most of the hydrolysis occurs during the enzyme heat up, following which the enzymes deactivate rapidly. Similar experiments with the thermostable enzyme system demonstrated high levels of viscosity reduction at elevated temperatures (up to 85°C) and limited viscosity reduction at ambient conditions. This is suggestive of enhanced capability of this enzyme system at elevated temperatures compared to that of the commercial system. Experiments using purified enzymes from both enzyme systems also revealed that the largest reduction in viscosity of guar solutions occurs with endo-β-D mannanase, the enzyme cleaving the bonds between the mannose backbone units.
Simulation of Transient Well-Test Signatures for Geologically Realistic Faults in Sandstone Reservoirs
Authors: Matthäi Stephan K. , Aydin Atilla , Pollard David D. , Roberts Stephen G. 
Published: December 2007

Summary
For the design of production strategies one must identify how faults that are detected in seismic surveys influence fluid flow in hydrocarbon reservoirs. In this study we use the Entrada sandstone formation, Arches Natl. Park, Utah, as an outcrop analog of a faulted sandstone reservoir. Field measurements of the geometry, thickness, and layered permeability of the normal faults that crosscut this sandstone are incorporated in two-dimensional (2D) fluid- flow models, facilitating the simulation of fault signatures in transient well tests with a high-resolution finite-element method.
In our simulations, structure and inhomogeneous permeability lead to fault signatures in derivative plots that differ significantly from those of idealized impermeable barriers. Highly permeable slip planes facing the well create the illusion of a nonsealing or nonexisting fault because remote fluids are focused along the slip planes toward the well. Measured low, fault-normal permeability shields fault-bounded blocks of the analog sandstone reservoir from drawdown and large pressure differentials build up across faults during production.
Thus, test data from a single well are insufficient to assess the flow properties of a nearby fault with an inhomogeneous permeability like the normal faults in the Arches Natl. Park. Test responses from multiple wells need to be considered to detect fault segmentation or fault terminations even if the general fault trend is underpinned by seismic data. Flow paths in the reservoir during production are complex. Importantly, formation water is likely to flow into the reservoir along the permeable slip planes of the normal faults.
Identification of Reservoir Heterogeneities Using Tracer Breakthrough Profiles and Genetic Algorithms
Authors: Guerreiro J. N. C. , Barbosa H. J. C. , Garcia E. L. M. , Loula A. F. D. , Malta S. M. C. 
Published: December 2007

Summary
In this paper, we describe a methodology to identify reservoir properties by using numerical techniques that combine finite element methods, a streamline approach, and genetic algorithms. As a model problem, we consider the system of equations governing incompressible miscible displacement in two dimensions (2D) in which the solution furnishes tracer breakthrough profiles that are parametrized as functions of the properties to be determined. Given a population of initial parameters, after the solution of the model problem and the comparison of each profile with a target one, we evolve to a new population, following the concepts of genetic algorithms and according to the fitness of each member of the previous population.
Mathematical Modeling of Secondary Precipitation From Sandstone Acidizing
Authors: Li Y.-H. , Fambrough J. D. , Montgomery C. T. 
Published: December 2007

SummaryField and laboratory experience clearly demonstrates that, besides primary dissolution, precipitation from both secondary and tertiary reactions with aluminosilicates adversely affects matrix acid treatment success. In the secondary reaction, fluosilicic acid from the primary dissolution will further react with aluminosilicates to form hydrated silica on the matrix surface. In the tertiary reaction, aluminum fluoride also extracts aluminum from aluminosilicates to form silica gel by lowering the fluoride/aluminum (F/Al) ratio in the solution. In the presence of a high concentration of metal ions, metal fluorides and fluosilicates are also likely to precipitate.An optimum acidizing design package can be derived for a specific formation mineralogy and damage mechanism if this complex reactive system can be modeled properly. A geochemical model for acidizing has been developed for this purpose. The numerical simulator is a reactive flow model that solves the reactive system with both reaction kinetics and chemical equilibrium calculations. All possible reactions among all species in the system are solved simultaneously. As acid spends, the computer simulation shows the progress of aluminosilicate dissolution and the formation of different precipitates as the change of dissolved species along the reaction path occurs. The evolution of the damage skin can be evaluated as simulation continues. On the basis of simulation, different pumping schedules with different types of acids can be quickly evaluated to optimize treatment volume and minimize precipitation of hydrated silica and other precipitates.To validate the model, a series of laboratory coreflood tests has been fully analyzed. The results indicate that the formation of silica gel is significant, on the basis of hydrofluoric acid (HF) effluent analysis. The same set of kinetic data derived from the laboratory coreflood data adequately predicts and explains a sandstone acidizing field case.
Interval Pressure Transient Testing With MDT Packer-Probe Module in Horizontal Wells
Authors: Kuchuk Fikri J. 
Published: December 2007

Summary
In this paper, the use of various pressure measurements is investigated for determining formation pressure and permeability distributions by use of the multiprobe formation testing packer and probe modules (PPM's) in horizontal wells. It is shown that reservoir pressure measurements along the wellbore give local and reservoir-scale information about how the reservoir is being depleted and how cleanup takes place. The estimation of horizontal and vertical permeabilities, skin, and reservoir pressure along the wellbore is also presented by use of interval (local) pressure transient tests. For PPM in horizontal wells, an interpretation method is presented for determining the reservoir parameters. A few interval pressure transient test (IPTT) examples are presented for formation pressure and permeability distributions, and fluid sampling.
Teamwork Results in Wo rld-Record Length Casing String
Authors: Jellison M. J. , Eckroth J. J. , Fulton Jim , Ogren L. A. , Moore P. W. , Barber Vance , Vesely Don 
Published: December 2007

Summary
On 12 April 1996 Louisiana Land and Exploration Company successfully ran and cemented a 14,510 ft string of 16-in. 146.2 lbf/ft (0.907-in. wall) P-110 casing in their Big Horn 4-36 well located in Fremont County, Wyoming. The string had an air weight of over 2.1 million pounds and a hook load of over 1.8 million pounds. This world record feat was the result of a concerted, team effort involving Engineering, Purchasing, Suppliers, and Service Companies. The 16-in. casing string played a critical role in drilling the well that had a total depth of over 24,000 ft. The paper details the complementary roles and contributions of each group involved in this challenging project. The overall well design philosophy is discussed along with a review of the detailed 16-in. casing design structural load and von Mises triaxial stress analysis. The specialized casing material specifications and manufacturing procedures are presented and related to casing string performance requirements. The paper outlines the casing connector selection criteria and describes the premium connector used on the casing string to withstand the high axial forces and pressures encountered while running the casing and drilling the well. The equipment and procedures used to safely and efficiently run the casing string in a total of only 43 hr from rig up to tear down with 31 hr running time are also described. The 14,510 ft casing string was cemented back to the surface in a single stage. The paper addresses the importance of the mud properties prior to cementing as well as the design and execution of the cement job. Both were critical to successfully completing the job.
Effect of Heterogeneity on the Non-Darcy Flow Coefficient
Authors: Narayanaswamy Ganesh , Sharma Mukul M. , Pope G. A. 
Published: December 2007

SummaryAn analytical method for calculating an effective non-Darcy flow coefficient for a heterogeneous formation is presented. The method presented here can be used to calculate an effective non-Darcy flow coefficient for heterogeneous gridblocks in reservoir simulators. Based on this method, it is shown that the non-Darcy flow coefficient of a heterogeneous formation is larger than the non-Darcy flow coefficient of an equivalent homogenous formation. Non-Darcy flow coefficients calculated from gas well data show that non-Darcy flow coefficients obtained from well tests are significantly larger than those predicted from experimental correlations. Permeability heterogeneity is a very likely reason for the differences in non-Darcy flow coefficients often seen between laboratory and field data.