bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas-Water Counter-Current Capillary Imbibition at Different Temperatures
Authors: Babadagli T. , Hatiboglu C. U. 
Published: December 2007

AbstractGas water counter-current matrix–fracture interaction due to capillary forces was studied. The focus was on the rate of capillary imbibition and the development of residual gas phase under low (20 °C) and high temperatures (90 °C). Berea sandstone and Indiana limestone samples with different shape factors were obtained by cutting the plugs 1, 2.5, and 5 cm in diameter and 2.5, 5, and 10 cm in length. All sides were coated with epoxy except one end. Static imbibition experiments were conducted on vertically and horizontally situated samples where the matrix-fracture interaction took place upward and lateral directions, respectively. The effects of the matrix shape factor, wettability, surface tension, and core position on the recovery rate and ultimate recovery were investigated.The experimental scheme followed was useful in identification of the development of residual gas saturation for fully counter-current matrix-fracture interaction. We investigated and clarified to what degrees the rock/fluid properties (wettability and matrix shape factor) and existing conditions (temperature, causing lowered IFT and brine viscosity, and gravity) become effective on the residual gas saturation. It was observed that the residual gas saturation is sensitive to the matrix shape factor. The effect of surface tension on the recovery rate and ultimate recovery was also critical. The vertical cases yielded different recovery rates and ultimate recoveries with increasing temperature. Lower residual gas saturation with increasing temperature was obtained only for large diameters. That was attributed to the reduction in surface tension.Finally, critical matrix and fluid properties were correlated to the residual gas saturation and different dimensionless groups were tested for scaling.
Improved In-Situ Combustion Performance With Metallic Salt Additives
Authors: He B. , Chen Q. , Castanier L. M. , Kovscek A. R. 
Published: December 2007

Abstract
In-situ combustion is an effective thermal recovery process. A part of the oil is burned in-situ, heat is generated, oil viscosity decreases, and larger oil recovery results. Thus, a key mechanism is effective oxidation of a small fraction of the oil in place to generate heat and pressure. Common, water-soluble metallic salts are known to play an important role as a catalyst for some combinations of crude oil/brine/solid matrix. Metallic additives enhance oxidation and cracking of hydrocarbons and thereby affect the nature and the amount of fuel formed. The mechanism of the catalytic effect is, as of yet, unknown.
This paper describes an experimental study combining tube runs that gauge combustion performance and ramped temperature oxidation tests that measure the kinetics of combustion. We propose cation exchange of metallic salts with clay as a mechanism to create activated sites that enhance combustion reactions between oil and oxygen. Sand and clay surfaces are examined with scanning electron microscopy for evidence of cation exchange and alteration of surface properties by metallic salts. The oils studied are heavy and light oil from Cymric (Kern, Co., CA). Effluent gas analysis is conducted and temperature profiles are measured. Additive improved performance in all cases including lower activation energy, greater oxygen consumption, lower temperature threshold, and more complete oxidation. In tube runs, Cymric light oil (34 °API) did not exhibit sustainable combustion, but gave sustained combustion with the addition of iron nitrate. Thus, metallic additives have potential to expand the range of candidate reservoirs for in-situ combustion.
Optimizing Cyclic Steam Oil Production with Genetic Algorithms
Authors: Patel A. , Davis D. , Guthrie C. , Tuk D. , Nguyen Tai , Williams J. 
Published: December 2007

Abstract
This case study describes a project applying a new technology—genetic algorithms—to the problem of scheduling oil production by cyclic steaming at an oil field in the San Joaquin Valley. The paper has seven parts.
In the first part, we discuss the nature of the problem, the importance of solving it well, and the nature of the work process as it occurred before the project began. In the second part, we discuss genetic algorithms and the way that the project adapted them to solve the problem of scheduling cyclical steam injections. In the third section, we describe a pilot project that demonstrated the potential of the approach. In the fourth, we describe the full project that created an optimization tool that has been working daily with oil field personnel to schedule production for the entire field for more than a year. In the fifth, we discuss two types of results of the project—an increase in production and changes to the work process on the part of the oil field personnel owing to their enthusiastic adoption of the optimizer. In the sixth, we discuss some project management factors that led to the success of the project. Finally, we discuss ways in which the success of this project may be relevant to a variety of other types of scheduling and resource allocation problems in the field of oil production.
The paper will center on three themes: the successful solution of a hard production problem with a new technology; the impact of that technology on the oil field personnel; and the potential of that technology to support other types of projects with similar levels of return.
Viscosity Reduction WAG: An Effective EOR Process for North Slope Viscous Oils
Authors: McGuire P. L. , Redman R. S. , Jhaveri B. S. , Yancey K. E. , Ning S. X. 
Published: December 2007

Abstract
A novel EOR method, Viscosity Reducing Water-Alternating-Gas injection (VR-WAG), has been developed to improve oil recovery from viscous oil reservoirs and under-saturated light oil reservoirs. Heavy components are mixed with produced lean gas to manufacture viscosity-reducing injectant (VRI). When VRI is injected into a heavy oil reservoir, oil viscosity can be reduced by up to 90% and the oil recovery can be improved by 15-20%.
VR-WAG may be widely applied in Alaska's heavy oils. The first enriched gas application will be the West Sak 1-J EOR Project (WS-1J) at Kuparuk. Additional projects are likely to utilize VR-WAG, including the Prudhoe Bay satellite fields, Orion and Polaris, and the S-pad EOR Project at Milne Point. Laboratory experimental data, numerical simulation results, and potential project scopes from each of these fields are included.
Understanding Formation Damage in a Stevens Reservoir at Elk Hills California
Authors: Smith S. , Williams W. , Ansari K. 
Published: December 2007

Abstract
As reservoirs mature, understanding the source and reversibility of any formation damage is particularly critical for sustaining production. The 26R Reservoir at Elk Hills contains a substantial oil column. Gravity drainage is the primary recovery process of this remaining oil in place. Recently, two horizontal wells were successfully drilled through the bottom of the oil column to enhance gravity drainage. Subsequent testing revealed drilling fluids leak off will create a wellbore skin; reducing permeability and production potential by over 90%.
This paper will review analytical calculations and assumptions used to determine well production potential and discusses extensive core description and core flow work completed. The core work has validated production potential assumptions. The extensive core description work and core flow tests has generated a better understanding of rock and mineralogical properties, at a pore level. Cores were exposed to various drilling and workover fluids and stimulation procedures. Treatment effects were then measured via return permeability tests and then further evaluated by preparing contaminated core thin sections and using a scanning electron microscope. Workover fluids are now more carefully applied during well remedial operations. In addition, the core work has modified acidizing and perforating procedures. Follow-up well treatments have shown promise by reducing observed skin, and increasing production
The Geochoke Well Test Response in a Catalogue of Systematic Geotype Curves
Authors: Corbett P. W. M. , Ellabad Y. , Egert J. I. K. , Zheng S. 
Published: December 2007

Abstract
A new well test response has been identified. A distinctive restriction – shown as a hump on the derivative curve – is seen in double matrix porosity (dual permeability) reservoirs. High permeability lenses intersecting the well bore give rise to a negative geoskin response at early time. After the middle time period of flow restriction caused by the limits of the lenses connecting to the wellbore and the presence of additional limited extent, discontinuous, high permeability lenses within the reservoir. This phenomenon has been shown in a series of numerical models and is also observed in two field well tests.
The two field examples come from testing in a braided fluvial oil reservoir. Other interpretational possibilities (e.g., sub- seismic faulting, fluid changes), which might also be considered given the non-uniqueness of pressure data, are eliminated by careful consideration of the geophysical interpretation, the depositional environment and the fluid properies. Sub-seismic faults are often interpreted in well tests from braided fluvial reservoirs. However, we consider that the response in these cases, and possibly in a wider range of cases, is due to geological effects of sedimentary heterogeneity due to secondary channels within the braided system. Braided fluvial sedimentary processes result in heterogeneous reservoirs with double matrix porosity. The heterogeneity and the double matrix porosity nature of these reservoirs are evident from the Lorenz Plot. Such sandstones can produce a variety of well test responses as the two matrices interact at various length scales.
The geochoke model in double matrix porosity reservoirs is an end-member response for reservoirs with short lateral and vertical correlation length. A family of geotype curves can be generated to consider a range of correlation lengths to systematically explore the limits of early, middle and late time responses for specific reservoir cases.
Downhole Harmonic Vibration Oil-Displacement System: A New IOR Tool
Authors: Zhu T. , Xutao H. , Vajjha P. 
Published: December 2007

Abstract
Excessively large amplitude excitations resulting from earthquakes, explosions, or mechanically vibrated systems are found to generate macroscopic and microscopic mechanisms that have beneficial effects on the production of wellbores. A downhole harmonic vibration oil-displacement system (DHVOS) that generates a sudden large amplitude excitation to the liquid in the wellbore was developed by researchers at CNPC (China National Petroleum Company). Compared with other downhole artificial vibration systems, the DHVOS system is a heavy-duty unit that can provide long period operations and large amplitude excitations. This system has been implemented in CNPC's oil fields such as Liaohe, Huabei, Shengli and Zhongyuan. The DHVOS system provides a harmonic vibration frequency of 88 shocks per minute with each shock having 5-ton strength. More than 100 oil-producing wells have been stimulated with the downhole vibration system since 1997. The field results demonstrated that periodic application of large amplitude excitation to oil reservoirs led to increased oil production rates and decreased produced fluid water content. The observed oil production-rate increments ranged from 27.5% to over 400% with an average increment of 47.6% compared to the pre-vibration production rates. The reduction in water oil ratio (WOR) varied 10% to 75% with an average of 48.4% in WOR reduction.
New economic indicator to evaluate SAGD performance
Authors: Shin H. , Polikar M. 
Published: December 2007

Abstract
The steam-assisted gravity drainage (SAGD) process simulations described in this study have been optimized to have the lowest cumulative steam-oil ratio (CSOR), highest RF and highest CDOR in order to obtain optimal operation conditions. In addition, net present value (NPV) calculations were performed for each simulation case to take the time factor into account.
A simple thermal efficiency parameter (STEP), based on CSOR, CDOR and RF for the time corresponding to SOR = 4, was developed to evaluate the performance of a SAGD project under optimized conditions. A linear relationship was found to exist between STEP and NPV, with a correlation coefficient in excess of 0.96 for most of the cases studied. For each simulation case, highest values of NPV and STEP indicated optimum SAGD operating conditions.
Chemical Treatments for Removal of Drill-in-Fluid Damage in Horizontal-Multilateral Gas Wells: Lab Studies and Case Histories
Authors: Al-Otaibi M. B. , Nasr-El-Din H. A. 
Published: December 2007

Abstract
Water-based fluids have been used to drill various wells in Saudi Aramco fields. A typical water-based mud consists of xanthan, starch or cellulose polymers, plus bridging agents like sized calcium carbonate or salt particles. The polymers in the drill-in fluids are needed to build the required viscosity to transport cuttings and form a filter cake around the wellbore to reduce the fluid loss. Some of these polymers invade the critical near wellbore area and may cause formation damage.
One of the treated wells was the first multi-lateral ever drilled in a deep sandstone gas reservoir in Saudi Arabia. The dual-lateral well was completed with a pre-drilled liner completion. Mineral and organic acids can be used to remove the filer cake, but they cannot be applied in horizontal and multilateral wells without using an effective diversion technique. In addition, the sandstone formation in this case is acid-sensitive. As a result, a filter cake cleanup process was performed separately in each lateral, using a completion brine wash followed by a specific enzyme treatment.
Several lab studies were conducted using field mud samples to determine the cleaning efficiency of enzymes used to remove damage which occurred while drilling the target zone. For the first time, an enzyme solution was spotted in one lateral and left in the hole for more than four months, until the second lateral was drilled and the well was ready for testing.
Various tests were conducted on well flowback samples after the enzyme treatments. These tests included: chemical analysis of the aqueous phase and full analysis of the produced solids using acid solubility, sieve analysis, XRD, XRF, and SEM. In addition, the carbohydrates content in the aqueous phase was measured using the anthrone method.
A significant improvement in gas production from this well has been realized through the application of the enzyme treatment for the removal of starch and XC polymers used in drilling operations. This paper will discuss in detail laboratory work that was conducted to assess this field treatment.
Injection Fracturing in a Densely Spaced Line Drive Waterflood - The Halfdan Example
Authors: Rod M. H. , Jørgensen O. 
Published: December 2007

Abstract
Induced fractures are actively steered along horizontal water injection wells in a densely spaced line drive water flood, thus ensuring efficient sweep and minimising random connections between parallel producer and injector wells. Due consideration of flow-induced changes to the stress field reduces the risk of premature water breakthrough during injection at fracturing conditions. The paper differs from other works concerning flow-induced stresses by focussing on the application of this phenomenon and the practical experiences from a field-wide implementation.
A technique, named "Fracture Aligned Sweep Technology" (FAST), has been implemented on the Halfdan chalk field in the Danish North Sea with horizontal wells drilled at 600 ft lateral spacing in a parallel pattern of alternating producers and water injectors with 10,000 to 15,000 ft long reservoir sections. Fracturing of the injector wells is the key to the process of voidage replacement, due to the low mobility of water compared to oil and gas.
FAST uses the fact that fluid flow in rock of low permeability affects reservoir stresses. Before propagating a fracture, the prevailing pressure field is manipulated through a period of injection below fracture propagation pressure and simultaneous production from the neighbouring wells. Numerical simulation of fracture propagation shows that seepage forces strongly influence the propagation direction when an injection fracture propagates in a laterally varying pressure field. At slow propagation rates the pressure diffusion from the fracture itself causes alignment of the fracture with the injection well, i.e. the technique works because the injection rates are actively controlled.
Confinement of injection fractures along horizontal injector wells is verified by production data from areas where FAST has been implemented. After 2-3 years of injection, water breakthrough to the neighbouring producers has not occurred. A positive production response to the high rate injection is demonstrated by increasing oil rate and decreasing gas-oil ratio.
Visual Investigation of Oil Depressuristion in Pores with Different Wettability Characteristics and Saturation Histories
Authors: Nejad K. S. , Danesh A. 
Published: December 2007

Abstract
When the water-cut is too high for economical production, the field is usually abandoned with significant quantity of oil and gas still remaining in the reservoir. It is likely that in some cases a significant amount of gas and residual oil can be produced by the process of depressurisation. The underlying physics of the above complex three-phase flow is not well understood to allow reliable predictions to be made for economic evaluation of the process.
We have conducted flow visualization at the pore level using high-pressure glass micromodels to identify the key features of the process. Depressurisation tests were conducted on model fluids simulating black and volatile oil samples at several depletion rates. Micromodels with realistic pore patterns and different wettability characteristics, including water-wet, oil-wet and mixed-wet, were used in the tests. A series of experiments were performed to investigate the effect of fluid properties, depletion rate, saturation conditions, and wettability and saturation history on the nucleation process, gas evolution and hydrocarbon movement. Tests were conducted on water-flooded oil as well as virgin oil.
Our observation highlighted that gas nucleation was dependant on fluid properties, particularly the gas/oil interfacial tension (IFT). In high IFT systems, the nucleation behaviour and the degree of supersaturation were affected by the saturation history and system wettability. In volatile oil systems with low interfacial tension between gas and oil, nuclei could form homogeneously and independently of wettability conditions and saturation history. Critical gas saturation and subsequent gas/oil production are strongly affected by the critical value of supersaturation and the number of bubbles that are formed during the depressurisation process. Two generalized correlations were developed to predict the critical supersaturation and the number of bubbles. The correlations reliably predicted independent experimental data reported in the literature. The data generated by the study provides information on gas nucleation sites, the gas nucleation rate and build up of the gas phase, which are essential in field development planning and estimation of oil and gas recovery.
Development of a Hydraulically Expanded Metal Internal Casing Patch
Authors: Louden F. , Mathiassen E. , Hazel P. , Skjerping F. , Gorrara A. , Bøe K. 
Published: December 2007

Abstract
This paper details the technical development & implementation of a Coiled Tubing (CT) deployed, expandable internal metal casing patch. The driver for the development of the technology was to introduce an internal casing patch system for deployment in 7" tubing, designed to extend the completion life and delay a full workover operation. The compliant patch would provide a substantive localised tubing repair (e.g. water shut-off, leak repair, patch corroded pipe) with minimal internal diameter restriction to optimise access for future well interventions, and hence minimise the restriction to oil production (or water injection).
Physical and Rheological Behaviour of High Pressure-High Temperature Fluids in Presence of Water
Authors: Gozalpour F. , Danesh A. , Fonseca M. , Todd A. C. , Tohidi B. , Al-Syabi Z. 
Published: December 2007

Abstract
An equation of state-based phase behaviour model has been developed to describe the behaviour of high pressure-high temperature (HPHT) fluids in presence of water. The interaction between water (polar) and hydrocarbon (non-polar) has been simulated by addition of an asymmetric (non-random) term to the attractive term of a conventional (random) mixing rule. Vapour-liquid and liquid-liquid hydrocarbon-water solubility data of a wide range of hydrocarbons have been used to determine the binary interaction parameters of the conventional and non-random terms. The developed phase behaviour model was evaluated against two-phase and three-phase equilibrium data of hydrocarbon and water binary and ternary mixtures, not used in developing the model, over a wide range of temperature.
The impact of water on the viscosity of pure and binary mixtures of hydrocarbons at HPHT conditions has also been investigated. A HPHT facility equipped with a capillary tube viscometer was used to make the measurements at 150 and 200°C and up to 20000 psia. The generated data have been used to evaluate residual viscosity models.
Micro-PIV: A New Technology for Pore Scale Flow Characterization in Micromodels
Authors: Perrin C. L. , Sorbie K. S. , Tardy P. M. J. , Crawshaw J. P. 
Published: December 2007

AbstractEtched micromodels have often been used to visualize complex fluid flow and displacement mechanisms at the pore scale. Studies have been reported of two and three phase processes such as waterflooding and water-alternating-gas (WAG) injection. Many of these models have been etched in glass although the use of etched silicon in their manufacture allows for the much more precise replication of two-dimensional (2D) network structures. A feature of previous micromodel studies is that they have almost exclusively been confined to making qualitative observations; e.g. descriptions of pore-scale displacement events, the effects of wettability, the formation and collapse of films etc. However, quantitative information relating for example to the network velocity field at the pore scale has never been reported and this issue is addressed in this paper for the first time.Particle Imaging Velocimetry (PIV) is a well-known technique used in large-scale fluid mechanics experiments. It has recently been adapted to study microfluidics problems. As a result, the velocity field can now be measured at any location in pore-scale micromodels where the channels have widths of typical rock pores (10s – 100s μm). For the first time, this new technology, known as micro-PIV (μ-PIV), has been used to study the flow of Newtonian and non-Newtonian fluids in model pore channels with sizes typical of natural sandstone.In this study, we apply μ-PIV to the flow of water, and non-Newtonian fluids in straight micro-capillaries. The μ-PIV experimental velocity profiles match the analytical solution for water, and the finite element calculations for non-Newtonian fluids, thus validating the technique. μ-PIV was then applied to the flow in a Berea sandstone replica micromodel. The potential of this technique is highlighted for use in several other applications of complex flows in porous media.