bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possibility of Cycling Deep Depleted Oil Reservoirs After Compression to a Single Phase
Authors: Katz Donald L. 
Published: April 2012

Abstract
The compressing of gas into a partially depleted gas drive oil reservoir to bring the contents to a single phase miscible with gas is proposed as a process worthy of serious study. The compressed gas and vaporized oil would be recovered by cycling. This paper explores the possibility of recovering oil from reservoirs of 6,000'Ft or more by this method.

Introduction
Many new methods for increasing the recovery of oil from reservoirs are under consideration in the various research laboratories. One method which should be considered for recovering oil from partially depleted gas drive fields is to compress gas into the reservoir until the contents become a single phase miscible with more gas. Natural gas then may be cycled through the reservoir to recover the oil. This procedure ideally will eliminate the capillary effects of the liquid in the porous media and, should permit recoveries similar to those obtained in cycling operations, probably of the order of 80 per cent. This paper explores the information now available for the prediction of the performance of such a project and discusses the problems likely to be encountered in recovering oil by cycling.
For many years dry natural gas has been passed through oil reservoirs to recover natural gasoline which would vaporize from the oil. Recently a process of recovering more of the high boiling hydrocarbons has been described by employing high pressures at which the heavier hydrocarbons have a higher volatility. Nevertheless, this reported method does not eliminate the differential nature of the vaporization process and capillary forces are still present in the reservoir. The process under discussion in this paper would minimize differential vaporization and would remove capillary forces which are responsible for low oil recoveries. Higher gas pressure, are required to accomplish this removal of the miniscus, but it does not follow that more gas is required for oil recovery. The process is limited to reservoirs deep enough to permit the use of the required pressure - probably 6,000'Ft and deeper.
Numerical-Simulation Investigation of the Effect of Heavy-Oil Viscosity on the Performance of Hydrocarbon Additives in SAGD
Authors: Hosseininejad Mohebati M.. , Maini B.B.. B. , Harding T.G.. G. 
Published: April 2012

SummaryHeavy oil and bitumen are expected to become increasingly important sources of fuel in the coming decades. There are extensive deposits in Alberta that could be a principal source of fuel in the coming century. The Athabasca oil sands, the largest petroleum accumulation in the world; the Cold Lake oil deposit; and the Lloydminster reservoir are all major Canadian oil-sands deposits. Steam-assisted gravity drainage (SAGD), which has shown considerable promise in all three of these major deposits, remains an expensive technique and requires large energy input. The energy intensity of SAGD and the environmental concerns make it imperative to find new oil-extraction technologies.Coinjecting hydrocarbon additives with steam offers the potential of lower energy and water consumption and reduced green-house-gas emission by improving the oil rates and recoveries. In a previous paper by the same authors (Hosseininejad Mohebati et al. 2010), we showed that the selection of a suitable hydrocarbon additive and the effectiveness of this hybrid process are strongly dependent on the operating conditions, reservoir-fluid composition, the heavy-oil viscosity, and the petrophysical properties of the reservoir. Among these factors, the heavy-oil viscosity, which is the main difference between these three reservoirs, could be a very important parameter in the performance of this hybrid process. Therefore, it is necessary to optimize the hydrocarbon additives to SAGD for these three oil-sand deposits separately.Extensive numerical studies in a 3D model by means of a fully implicit thermal simulator were conducted to evaluate the efficiency of each hydrocarbon additive with different heavy-oil viscosities (resembling those of Athabasca bitumen, Cold Lake heavy oil, and Lloydminster heavy oil). Varying mole percents of hexane, butane, and methane were coinjected with steam to each reservoir with different heavy-oil viscosity. The optimum amount of hydrocarbon injection was reported in each case. This culminated in a novel method for selecting the most advantageous hydrocarbon additive and its optimum concentration considering the heavy-oil viscosity.
Reservoir-Navigation System and Drilling Technology Maximize Productivity and Drilling Performance in the Granite Wash, US Midcontinent
Authors: Janwadkar S.. , Thomas M.. , Privott S.. , Tehan R.. , Carlson L.. , Spear W.. , Setiadarma A.. 
Published: April 2012

Summary
The Granite Wash unconventional gas and oil play of the US midcontinent has a multitrillion-cubic-feet-equivalent upside potential. The condensates and natural-gas liquids associated with this gas play make it one of the most-prolific and fastest-growing unconventional fields in North America. However, efficient extraction of hydrocarbons from the Granite Wash play poses drilling and geological challenges. The Granite Wash deposit has significant lateral variation, with extremely abrasive thinly bedded sandstones. Geological complexity of this field requires precise placement and navigation of the wellbore in real time to overcome the variable characteristics of the reservoir. To overcome these challenges, logging-while-drilling (LWD) technology was used in conjunction with geosteering. An azimuthal gamma ray image was used to determine formation bed dip and stratigraphic complexity within the reservoir. Multiple-propagation resistivity measurements were used to correlate position within the reservoir and indicate formation porosity. The LWD data was transmitted in real time by means of satellite to a remote reservoir-navigation center where the reservoir-navigation engineer incorporated the real-time data into the geological model. This strategy has been implemented to drill with excellent results, as compared with the offset wells. The initial production rate obtained was 19.4 MMcfe/D (cfe = cubic foot equivalent). The well was completed 10 days ahead of schedule, resulting in significant cost savings. With the successful implementation of real-time reservoir-navigation and drilling technology, the operator accelerated their drilling program. The results are significant organic production growth, improved drilling performance, precise placement of the wellbore, and significant reduction in rotating hours at lower drilling and production costs.
A New Correlation of Acid-Fracture Conductivity Subject to Closure Stress
Authors: Deng J.. , Mou Jianye , Hill A.D.. D. , Zhu D.. 
Published: April 2012

Summary
The conductivity of an acid-etched fracture depends strongly on void spaces and channels along the fracture resulting from uneven acid etching of the fracture walls. In this study, we modeled deformation of the rough fracture surfaces acidized in heterogeneous formations based on synthetic permeability distributions and developed a new correlation to calculate the acid-etched fracture conductivity.
In our previous work, we modeled the dissolution of the fracture surfaces in formations having small-scale heterogeneities in permeability. The characterization of the correlated permeability fields of rock includes the average permeability, normalized correlation lengths in both horizontal and vertical directions, and normalized standard deviation. These statistical parameters have a significant influence on the fracture-etching profiles obtained from the model. Beginning with this fracture-width distribution, we have modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. The elastic properties of the rock, such as Young's modulus and Poisson's ratio, have effects on the size of the spaces remaining open after fracture closure. After the model yields the width profile under closure stress, the overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system.
In this paper, we introduce our models and investigate the effects of permeability and mineralogy distributions and rock elastic properties on the overall conductivity of an acid-etched fracture. A new acid-fracture conductivity correlation is developed on the basis of many numerical experiments.
The Guard Electrode Logging System
Authors: Owen John E. , Greer Walton J. 
Published: April 2012

Abstract
The guard electrode system measures the resistivity of formations by employing a thin disk of current which is caused to flow perpendicular to the bore hole. The control of this current disk is obtained in a brute force manner through the use of relatively long equipotential electrodes above and below the measuring electrode.
The log obtained from the system is free of "lag," "plateau," "shadow," "reflection" and other distortions evident on conventional logs. The proportionate contributions of the hole size and invaded zone resistivity to the apparent resistivity reading are reduced when the mud and filtrate resistivities are lower. Thus, the guard system favors the use of conductive muds.
The mathematical development of the theory is given in an appendix. Equations are derived to evaluate the effects of mud resistivity, hole size, invaded zone resistivity and depth, and the true formation resistivity.
Sample logs from several provinces are reproduced and compared with conventional electric logs to illustrate the much greater detailed lithology that can be presented by the guard electrode system.

Introduction
With increased ability of those in the petroleum industry to analyze formation characteristics from electrical resistivity data, there has become apparent the need for more precise measures of that parameter.
The measurement of the resistivity of a homogeneous and isotropic material can be made simply when the body of the material is infinite in all dimensions and the measuring electrodes can be placed within the body. In such a case, the current leaving an electrode follows a spherical distribution and the mathematical expression for the potential level at any distance from that electrode can readily be derived.
If it is considered that the active electrodes are within a bore hole filled with mud of a resistivity different from that of the formation, the current does not flow in a spherical pattern near the current source or sink, and the calculations of potential levels become more difficult. The additional consideration of a section of formation invaded by mud filtrates, and thus having resistivity different from either that of the mud, the adjacent formations or of the undisturbed formation, makes the mathematical problem extremely complex. Should the vertical dimensions of the formations be considered as finite, the problem becomes so complex as to preclude reasonable solution. Yet, even these considerations have not described adequately the conditions encountered in a large proportion of the wells to be studied.
Radial Filtration of Drilling Mud
Authors: Prokop C.L. 
Published: April 2012

Abstract
A laboratory investigation has been made of the effects of mud hydraulics upon the formation and erosion of mud filter cakes. The tests were conducted to simulate drilling conditions as nearly as possible.
The formation of mud filter cake in a drilling well does not proceed at a uniform and unbroken rate. Instead, the rate of cake accumulation depends upon whether or not the mud is being circulated. If the mud column is quiescent, filter cake formation is a smooth function of the filtration characteristics of the system. If the mud is being circulated filter cake formation depends not only upon the filtration characteristics of the mud but also upon the erosive action of the flowing mud column.
Filter cakes formed during continuous mud circulation were observed to reach an equilibrium thickness after several hours' circulation. Mud circulation was maintained at a constant volumetric rate throughout each experiment. The fluid velocity at equilibrium cake thickness was dependent upon the thickness of the filter cake. Muds having exceptionally high water loss deposited thick filter cakes in spite of very high eroding velocities. The muds having good filtration characteristics deposited thin filter cakes at equilibrium circulating velocities well within the range of those used in a drilling well.
It was observed that filter cakes deposited during stagnant filtration were quite difficult to erode by mud circulation. The rate of erosion computed from the rate of filtrate accumulation after equilibrium cake thickness had been reached was in reasonable agreement with the rate of erosion obtained by direct observation. Continuous mud circulation usually caused the permeability of the filter cake to decrease with time.

Introduction
Many of the difficulties encountered during the drilling of a well have been attributed to the loss of water from the mud and the attendant deposition of solids upon the walls of the hole. Past experience has shown that a reduction of the filtration rate of the drilling fluid eliminates or greatly reduces these difficulties. Definite filtration requirements, however, are hard to establish for a given set of conditions. This is due, in part, to the fact that the usual filtration test performed upon mud does not simulate well conditions as closely as desirable.
Production Analysis of Tight-Gas and Shale-Gas Reservoirs Using the Dynamic-Slippage Concept
Authors: Clarkson C.R.. R. , Nobakht M.. , Kaviani D.. , Ertekin T.. 
Published: April 2012

Summary
Shales and some tight-gas reservoirs have complex, multimodal pore-size distributions, including pore sizes in the nanopore range, causing gas to be transported by multiple flow mechanisms through the pore structure. Ertekin et al. (1986) developed a method to account for dual-mechanism (pressure- and concentration-driven) flow for tight formations that incorporated an apparent Klinkenberg gas-slippage factor that is not a constant, which is commonly assumed for tight gas reservoirs. In this work, we extend the dynamic-slippage concept to shale-gas reservoirs, for which it is postulated that multimechanism flow can occur. Inspired by recent studies that have demonstrated the complex pore structure of shale-gas reservoirs, which may include nanoporosity in kerogen, we first develop a numerical model that accounts for multimechanism flow in the inorganic- and organic-matter framework using the dynamic-slippage concept. In this formulation, unsteady-state desorption of gas from the kerogen is accounted for. We then generate a series of production forecasts using the numerical model to demonstrate the consequences of not rigorously accounting for multimechanism flow in tight formations. Finally, we modify modern rate-transient-analysis methods by altering pseudovariables to include dynamic-slippage and desorption effects and demonstrate the utility of this approach with simulated and field cases. The primary contribution of this work is therefore the demonstration of the use of modern rate-transient-analysis methods for reservoirs exhibiting multimechanism (non-Darcy) flow. The approach is considered to be useful for analysis of production data from shale-gas and tight-gas formations because it captures the physics of flow in such formations realistically.
A New Additive for Control of Drilling Mud Filtration
Authors: Salathiel R.A. 
Published: April 2012

Abstract
A new synthetic material has been developed which is highly effective in treating drilling muds to reduce filtration rate. The material is the soluble salt of a very high molecular weight condensation product of sulfonated phenol and formaldehyde (SPIF). Laboratory tests show that SPIF is effective in muds of all salinities varying from fresh water to saturated salt water. Alkaline materials, such as soda ash or caustic and quebracho, may be used in combination with SPIF to advantage, and are essential in muds containing saturated salt water. In a field test where the water used in the mud had a salinity of about one-half that of sea water, SPIF in combination with caustic and quebracho made a very satisfactory mud. SPIF does not ferment, but due probably to additional polymerization a slight decrease in effectiveness is found when it is subjected to high pH and high temperature for a long time.

Introduction
Drilling mud is essential in rotary drilling. The influence of variations in the different properties of a mud on its ability to perform the various functions in drilling of wells is thoroughly understood in some cases and poorly understood in others. For instance, the function of mud density in restraining high pressure fluids is simple and well known. On the other hand, while the value of low filtration is widely recognized, it is seldom possible to determine precisely what filtration rate is required for the mud to perform its functions properly. Filtration rate is important because it influences the ease of moving tools in or out of the hole. Filtration rate also affects the stability of the bore hole walls, which are subject to softening and degradation by aqueous filtrate. Difficulties in rotary drilling are often avoided by using low-filtration muds.
Treatment of fresh-water muds to provide moderately low filtration rates usually consists of adding chemicals to improve the dispersion of the clays. To provide very low filtration rates, organic colloidal materials are added. Among the materials that are used in this way are starch, natural gums, and altered celluloses. In muds that contain large amounts of salt or calcium or magnesium ions, the clays are coagulated and, as a consequence, the filtration rate is undesirably high. In such muds organic colloids are of great importance.
Decreasing Water Invasion Into Atoka Shale Using Nonmodified Silica Nanoparticles
Authors: Cai J. , Chenevert M. E. , Sharma M. M. , Friedheim J. 
Published: April 2012

Summary
Fluid penetration from water-based muds into shale formations results in swelling and subsequent wellbore instability. Particles in conventional drilling fluids are too large to seal the nano-sized pore throats of shales and to build an effective mudcake on the shale surface and reduce fluid invasion. This paper presents laboratory data showing the positive effect of adding commercially available, inexpensive, nonmodified silica nanoparticles (NP) (particle sizes vary from 5 to 22 nm) to water-based drilling muds and their effect on water invasion into shale.
Six brands of commercial and nonmodified nanoparticles were tested and screened by running a three-step pressure penetration (PP) test (brine, base mud, nanoparticle mud). Two types of common water-based muds, a bentonite mud and a low-solids mud (LSM), in contact with Atoka shale were studied with and without the addition of 10 wt% nanoparticles. We found that a large reduction in shale permeability was observed when using the muds to which the nonmodified nanoparticles had been added. For the bentonite muds, the permeability of Atoka shale decreased by 57.72 to 99.33%, and, for the LSMs, the permeability of Atoka shale decreased by 45.67 to 87.63%. Higher plastic viscosity (PV) and lower yield point (YP) and fluid loss (FL) of the nanoparticle muds compared with base muds were also observed. We also found that nanoparticles varying in size from 7 to 15 nm and a concentration of 10 wt% are shown to be effective at reducing shale permeability, thereby reducing the interaction between Atoka shale and a water-based drilling fluid.
This study shows for the first time that it is possible to formulate water-based muds using inexpensive nonmodified and commercially available silica nanoparticles and that these muds significantly reduce the invasion of water into the shale. The addition of silica nanoparticles to water-based muds may offer a powerful and economical solution when dealing with wellbore-stability problems in troublesome shale formations.
Improving Sweep Efficiency In A Mature Waterflood: Balcon Field, Colombia
Authors: Perez D. , Muñoz L. F. , Acosta W. , Falla J. , Martínez J. , Vidal G. , Manrique E. , Cabrera F. , Romero J. , Izadikamoue M. , Norman C. 
Published: April 2012

Abstract
The Balcon Field, operated by HOCOL S.A., is located in Colombia's Upper Magdalena Valley Basin. Oil production began in 1988, reaching a maximum primary rate of 5,742 BOPD in January 1994. Secondary recovery started in 1996, achieving a maximum secondary production of 9,198 BOPD in June 2001. Subsequently, water production has increased rapidly accompanied by declining oil production, due primarily to reservoir heterogeneity and an unfavorable mobility ratio. The oil recovery factor as of July 2011, as a percentage of OOIP, is estimated to be approximately 30% at a current water cut of about 84%.
This work presents a methodology to determine the feasibility of polymer gels to reduce water channeling, including water injection and production analysis, diagnostic charts, fluid movement and geological characterization. Results of this integrated analysis led to a comprehensive laboratory study to identify the appropriate gel formulation (e.g. polymer, polymer concentration and cross linker ratio) at reservoir conditions. The recommended gel system developed was validated by a core flood before field implementation.
The first gel treatment was implemented in July 2010, followed by a second injection well treatment in an adjacent pattern with significant water channeling. The treatment designs included several stages of varying gel concentrations and injection rates, which were modified during the field implementation based on surface pressure response.
Post treatment oil response occurred within approximately two months and payout was achieved in 6 months. As of April 2011 incremental oil of 212,000 bbl. has been produced. However, offset producers are still showing incremental production. These promising results led to a second (and ongoing) campaign in 2011.
Polymer gels have been successfully applied in sandstones reservoirs for decades. However, reservoir characterization tools continue to evolve contributing to the improvement of conformance treatment designs. This field case study will provide an updated framework for operators considering chemical sweep improvement technologies as part of an integrated reservoir management strategy.
Modeling Drilling Fluid Losses in Fractured Reservoirs
Authors: Oliveira J. A. , Souza J. Z. , Fontes C. E. , Waldmann A. T. , Martins A. L. 
Published: April 2012

Abstract
Fluid losses are still today one of the most challenging problems in well construction. Most strategies to control losses are empirical and in some situations, detrimental effects can not be avoided. This article deals with unique modeling efforts to understand the dynamics of bridging fractured zones. The main tools adopted to address the problem were the Computational Fluid Dynamics, whenever necessary coupled with Discrete Element Method packages. The main goal was to study particle deposition inside fractures due to losses through the external walls of an axial annular flow. ANSYS FLUENT® and EDEM® were the adopted simulation tools.
The study includes two different modeling strategies: Discrete Element Simulation and Granular Eulerian CFD approach. The first method solves the particle trajectory equations individually, considering collision and cohesion effects. Despite of the reliability of the approach, computation effort is huge and limits the number of particles in the system. The Eulerian approach, on the other hand treats statistically the particulate system, generating a probabilistic field of occurring one or the other phase at given space and time. This approach obviously generates smaller computational costs. The developed methodologies allow the evaluation of the efficacy of bridging agents in plugging fractured zones.