bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Pressure on CO2 Foam Displacements: A Micromodel Visualization Study
Authors: Chang Shih-Hsien , Martin F. D. , Grigg R. B. 
Published: December 2007

ABSTRACT
This paper presents the results of a visualization study on the effect of pressure on CO2-foam displacements at pressures above and below the minimum miscibility pressure (MMP). CO2-foam visualization experiments were performed by simultaneous injection of surfactant solution and CO2 into a high-pressure, glass micromodel saturated with Maljamar crude oil. CO2-foam was generated in situ during the simultaneous injection of surfactant solution and CO2. Simultaneous injection of brine and CO2 (WAG) displacements and pure CO2 displacements were also conducted to provide a reference point for the CO2-foam displacements. Results of these displacements were compared to examine the effects of pressure and injection mode on displacement performance and mechanisms. Two different kinds of micromodels were used in this study: modified-layer (MLAY) and modified-heterogeneous (MHET) micromodels. Pressures ranging from 775 to 1320 psia were investigated at a system temperature of 90°F. The surfactant solution used was 1% Alipal CD-128 in a 1 % NaCl brine.
Results show that sweep efficiencies were generally lower for pressures below the MMP. However, the effect of pressure on sweep efficiency for CO2-foam displacements was less than for WAG displacements and much less than for pure CO2 displacements. Sweep efficiencies for CO2-foam displacements at pressures just below the MMP were as high as above the MMP. Due to the lower density of injected CO2 near and below the MMP compared to that at higher pressures, the required mass of CO2 was as little as one-third of that required at higher pressures for similar sweep efficiencies using CO2-foam. These observations suggest the economical potential of operating CO2-foam floods at pressures close to and just below the MMP.
Gas/Oil Lamallae and Surfactant Propagation in the Oil in Carbon Dioxide Foam
Authors: Kuhlman M. I. , Falls A. H. , Wellington S. L. 
Published: December 2007

Abstract
Gas-oil foam has been; observed at reservoir conditions in microvisual experiments, created in laboratory corefloods, and shown to have been responsible for CO2 and N2 mobility reduction in experiments.
Gas-oil foam can increase oil recovery, since gas mobility is reduced without a reduction in oil mobility. It occurs when oil spreads between water and gas, and oil wets solid surfaces. The surfaces may be oil wet, be wet as surfactant partitions into oil, or when a surfactant is used below its Critical Micelle Concentration (CMC).
An oil bank is more mobile than injected brine, so oil soluble surfactants move ahead of aqueous components. Modeling suggest that gas-oil foam improves oil production in a reservoir, because surfactant in the oil rises to the oil bank at the top of a reservoir, where water mobility is too low for surfactant transport.
Composition of Remaining Oil in a Mature Steamflood
Authors: Richardson W. C. , Chu Chieh 
Published: December 2007

ABSTRACT
Steam distillation of reservoir oil occurs in the steam flooding process. The steam distillation phenomenon has been established and extensively studied in the laboratory, but has not been well understood in the field. The present work describes a compositional analysis of remaining oil with depth from a mature field steamflood, and supportive numerical simulation. Inclusion of the steam distillation mechanism in the analysis of the steamflood process is a potential emerging strategy for more enlightened reservoir operation and management.
Heavy stock tank oil characterization by a pseudo carbon number molar distribution and conventional analyses have been used to monitor changes in residual oil in a 70 ft mature steamflood zone in the Kern River Field, California, U.S.A. In order to obtain residual oil distributions, analysis methods were developed where the effect of the extraction solvent on oil composition determination was minimized, and assessments of the non-analyzable portion of the oil were made. The results of analyses of residual oil samples extracted from field core establish the effects of steam distillation and solvent formation in a mature steamflood.
The compositional effects on residual oil observed in the field have been supported by simulation. Numerical simulation of the cored zone was carried out using volatile pseudo components. The results showed the distribution of hydrocarbon components at various depths and grid blocks, and corroborated the laboratory work. Although this was applied to the Kern River Field, the approach has wider application to other steamfloods. The compositional effects will be even more important for lighter oil reservoirs, such as the Duri Field Steamflood.
A New Method To Characterize Fractured Reservoirs: Applications to Infill Drilling
Authors: Ouenes Ahmed , Weiss W. W. , Richardson Scott , Sultan A. J. , Gum Timothy , Brooks L. C. 
Published: December 2007

ABSTRACT
A new approach in fractured reservoir characterization that integrates geomechanics, geology, petrophysics and reservoir engineering is proposed and illustrated with an actual oil reservoir. This approach uses a generalized form of the curvature method to derive a model for fracture intensity and orientation for the Young Deep Unit (YDU). A reservoir inverse model was used to convert the fracture properties into effective petrogeological attributes. The inverse model uses simulated annealing and a black oil simulator to estimate fracture directional permeabilities and pore volume, reservoir wettability, and wellbore properties. The conditioned reservoir model that matches oil, gas, and water monthly rates, and reservoir pressure for a 151 month period, was used to construct an infill drilling criterion map to locate the best infill locations in the YDU.
A Combined Use of CRYO-SEM and NMR-Spectroscopy for Studying the Distribution of Oil and Brine in Sandstones
Authors: Rueslåtten Håkon , Øren P-E. , Robin Michel , Rosenberg Elizabeth , Cuiec Louis 
Published: December 2007

Abstract
This paper investigates the wettability behaviour of three rock samples from a Middle Jurassic Brent Group North Sea sandstone reservoir using a combination of traditional Amott and USBM tests, Cryo-SEM and NMR-spectroscopy. From Cryo-SEM observations it is concluded that two of the samples aged in crude oil display an oil-wet to intermediate wet behaviour and that residual oil is preferentially associated with kaolinite. The third rock sample (which has a permeability of only 19.4 mD) displays a more water-wet behaviour. The intermediate wettability nature of the rock samples is also reflected in the NMR data and it is demonstrated that NMR relaxation data may provide quantitative information about the saturations of wetting and non-wetting fluids and their distribution within the rocks.
Use of Horizontal Wells for Improving Steamflood Performance of a Thin, Low-Permeability Heavy-Oil Reservoir
Authors: Sarkar A. K. , Sarathi P. S. , Strycker A. R. 
Published: December 2007

Abstract
About 4 ×109 bbl heavy oil resource exists in thin (20-40 ft) domestic reservoirs. For this type of reservoir, steamflooding with conventional vertical wells is not economic, and in situ combustion methods are not applied due to operational difficulties. Horizontal well technology offers a potential for improving technical and economic performance of steamflood operations. A reservoir simulation study was conducted to (1) evaluate the viability of applying steamflood operations using horizontal wells in the Charivari Creek, Arkansas, waterflooded heavy oil reservoir and (2) analyze in detail the effects of different pattern configurations, including vertical injectors-vertical producers, horizontal injectors-horizontal producers, horizontal injectors-vertical producers and vertical injectors-horizontal producers, on steamflood performance.
Low permeability was found to have the most negative influence on steamflood performance for vertical injectors and producers. The injected steam raised the pressure and temperature of the reservoir to higher values than those observed in the high-permeability reservoirs, resulting in ineffective displacement and reservoir heating. Among the different configurations tested, the horizontal injectors-horizontal producers with 1,272-ft laterals increased the cumulative oil-steam ratio to 0.2 and decreased the production cost to $12.70/STB. Comparable results obtained for vertical wells are cumulative oil-steam ratio of 0.1 and production costs of $23.50/STB. Inclined wells showed poorer performances than horizontal wells because of nonuniform displacement. Configurations using horizontal injectors-vertical producers were not as effective as vertical injectors-horizontal producers because of fluid flow difficulties created with the high injecti vity of horizontal injectors and the low productivity of vertical producers.
Injection Conformance Control Case Histories Using Gels at the Wertz Field CO2 Tertiary Flood in Wyoming
Authors: Borling D. C. 
Published: December 2007

Abstract
Case histories described in this paper demonstrate the technical and economic value of using a specific work process coupled with advances in gel technology to improve vertical and areal injection fluid distribution at the Wertz Field carbon dioxide (CO2) Tertiary Flood in Bairoil, Wyoming. The Wertz case histories incorporate results from ten injection well gel conformance workover repairs with fluid performance response at offset producing wells. Post appraisal findings confirmed individual pattern life for tertiary processing was extended by nearly two years resulting in incremental oil recoveries of up to 140,000 barrels per pattern.
Polymer Gels for Conformance Treatments: Propagation of Cr(III) Crosslinking Complexes in Porous Media
Authors: Bartosek Martin , Mennella Aniello , Lockhart T. P. , Causin Emilio , Rossi Elio , Passucci Claudio 
Published: December 2007

ABSTRACT
The influence of pH, temperature, and gelation delaying ligands on the stability of Cr(III) complexes in bulk solution and on Cr(III) propagation in porous media has been investigated for acetate, glycolate, and malonate complexes of Cr(III). For a given complex, Cr(III) instability to hydrolysis and Cr(III) retention increase with increasing pH and temperature. The chemical nature of the gelation delaying ligands bound to Cr(III) and their coricentration in the solution have a profound influence on the resistance of the Cr(III) complex to hydrolysis and on Cr(III) retention. Thus, whereas the Cr(III) acetate crosslinker, by itself, propagates poorly at elevated temperature, addition of sodium glycolate to the solution markedly reduces retention. We show that Cr(III) retention in sandstone cores can be virtually eliminated at 90°C by appropriate formulation of the gel-forming solution. Other experiments establish that Cr(III) precipitation at elevated temperature is reversible in the presence of polymer and that significant accumulation of the Cr(III) precipitate can have a negative impact on injectivity.
Practical Implementation of Risk Analysis
Authors: Patteson R. M. , Grittner S. F. 
Published: December 2007

EXECUTIVE SUMMARY
Formal Risk Analysis and Decision Theory Principles are being utilized in daily operational decisions. A PC and Macintoch software program has been developed to minimize the effort and time required for this type of analysis. The process encourages structured thinking and the documentation of the justification and assumptions used in making decisions. This approach is not designed to replace the intuitive approach to decision making but rather to augment it.
The results of the project are encouraging. This methodology is being used more often by a larger group of decision makers. Communication between project team members has been improved as the common language of probability and cost is more frequently used when discussing alternatives. The emphasis of the project is to convince potential users that problem structure and the correct layout of alternatives is the single most important component of the process.
An Analysis of Oil and Gas Property Assessment Practices Used by County Assessors in California
Authors: DeWitt B. A. , Fiddler C. D. 
Published: December 2007

ABSTRACT
This paper discusses the methodology used by California tax assessors to set a fair market value (FMV) on California oil and gas properties for ad valorem tax purposes. A 265 parcel data set from 70 California independent oil and gas producers was used to look at how the assessors projected price, production, and cost data, and the basis they used to set a discount rate (DCR) for their cashflow projections in determining FMV. The study concludes that for the 1993-94 tax year county assessors did not adequately handle oil price risk, production forecast risk, or cost forecast risk in their analyses. As a result, the counties overassessed many of the parcels in the data set. An analysis of the derived market value indicators (MVFs) (i.e., payout, dollars per barrel oil equivalent reserve ($/BOE) and dollars per daily barrel oil equivalent ($/DBOE)) tends to verify the overvaluation conclusion.
Methods for Eliminating Pipeline-Riser Flow Instabilities
Authors: Jansen F. E. , Shoham Ovadia 
Published: December 2007

Abstract
Flow instabilities can occur in pipeline-riser systems operating at low liquid and gas rates, leading to an undesirable cyclic operation. Traditional methods for elimination of riser flow instabilities are choking and gas lift. However, each of these methods suffers from operational disadvantages. Choking can increase the back pressure, thereby, reducing production, while gas lift requires large volumes of injected gas.
The objective of this paper is to investigate existing methods and to propose a more optimum method for the elimination or minimization riser flow instabilities. An experimental study has been conducted to predict the behavior of the different methods of elimination of riser instabilities. It was found out that a combination of gas lift and choking is an efficient elimination method, reducing both the required degree of choking and the amount of injected gas required to stabilize the flow in the riser. The proposed method is less sensitive to choke setting and injected gas volume, as compared to elimination by either choking or gas lift alone. Additional advantage is the capability of a smooth and controlled start-up of the system.
This study demonstrates the usefulness of flow pattern maps as a simple and effective tool for the visualization and prediction of the occurrence of flow instabilities. Theoretical criteria have therefore been developed to predict the flow behavior for riser base gas lift and riser top choking.
Facility Optimization Through Process Review: A Case Study
Authors: Korn D. E. , Houghton M. K. , Langweil R. T. , Pauley J. C. 
Published: December 2007

ABSTRACT
The current operating environment of low oil prices and high regulation is putting significant pressure on operators to reduce their costs and environmental exposures. All too frequently these costs and exposures are the result of operating practices that date back to conditions and requirements that are no longer applicable. Often improvements can be made by optimizing the processes that are currently in place. In order to achieve the greatest gains however, a company must be willing to challenge the paradigms behind their current operating practices and be willing to change or eliminate processes as necessary.
This paper will describe the process and results of a systematic review of Texaco's Kern River Field plant operations.
This review resulted in the generation of dozens of process improvement ideas, some minor and some major. The significant improvements are discussed below. The results include a more stable operation and one that is much more cost effective.
An Operator's Perspective on Through-Tubing Recompletion Technology
Authors: Fleckenstein W. W. , Garner T. A. 
Published: December 2007

ABSTRACT
This paper reviews through-tubing recompletion technology, the isolation and/or addition of perforations in a wellbore without pulling the existing production equipment. Topics covered include through-tubing plugbacks and bridge plugs, coiled tubing cementing and through-tubing perforating. Several well case histories are also presented.
Reorientation of Propped Refracture Treatments in the Lost Hills Field
Authors: Wright C. A. , Stewart D. W. , Emanuele M. A. , Wright W. W. 
Published: December 2007

ABSTRACT
Chevron has performed over 200 refracture treatments in the diatomite reservoir within the Lost Hills field. Most treatments have consisted of refracturing intervals originally stimulated with less than adequate fluid and proppant volumes to efficiently deplete the reservoir. Many of these refracture treatments show production and pressure responses similar to new development wells completed in "virgin" reservoir. Recently, from 1990 to 1993, four new wells (post 1986) with modem initial fracture treatments were refractured in the same intervals with treatments similar (fluid and proppant volumes) to the original fracture treatments. All wells responded with post refracture production response equal to or slightly less than that of the original treatments. On the average these wells showed production increases of 50 BOPD over the previous daily rates of approximately 10 BOPD.
An effort began in 1993 to investigate possible reasons for the apparent "virgin" production response that resulted from the refracture treatments. A number of potential mechanisms were considered, including dramatic fracture conductivity degradation of the original propped fracture treatments; greatly enhanced fracture length growth upon refracturing; and stress change induced reorientation of the refracture treatments along a different fracture plane than the original fractures. This latter mechanism was considered the most likely mechanism and a program was designed to gather the necessary data for positive determination. Because Chevron had previously utilized tiltmeter fracture mapping on over 100 propped fracture treatments in the Lost Hills Diatomite, there existed ample original fracture treatment orientation data for comparison with fracture mapping data from refracture treatments.
In the Spring of 1993 tiltmeter fracture mapping was performed on five refracture treatments. All five of the refracture treatments propagated along a significantly different orientation than the original fracture treatments in these wells. Refracturing along a different fracture plane from the original fracture plane has dramatic implications for production strategies of both primary and secondary recovery. The tiltmeter fracture mapping results, production data, calculated reservoir stress changes, and proposed mechanism for refracture reorientation are all presented in the paper.
Individual Layer Transient Tests in Low-Pressure, Multi-Layered Reservoirs
Authors: Ryan T. C. , Sweeney M. J. , Jamieson W. H. , Tanigawa J. J. 
Published: December 2007

ABSTRACT
The Hugoton Field in southwestern Kansas, western Oklahoma and northwestern Texas is the largest gas field in North America. Gas production is from the shallow (2,100+ feet to 2,900+ feet) heterogeneous, multi-layered Chase reservoir. This paper details the results to date of an individual layer pressure testing program conducted by Mobil in 1992 on two wells in the Kansas Hugoton field. The recent history of pressure transient attempts in the Hugoton field is covered. How this information was used in planning the testing programs, foam drilling and coring, drill stem tests (DST), wireline pressure testing, in-situ stress and strain testing, and logging programs is explained as well as the evolution of the drilling, individual layer DST, completion, and individual layer cased hole testing operations and procedures. These wells represent the first time in recent history individual layer pressure and rate data has been measured in non-stimulated layers on any wells in the Hugoton field. The results of this test program are covered as well as how this data is being incorporated into Mobil's reservoir characterization and simulation efforts in this field. This analysis shows: (1) The pressures ranged from 142 psia to 320 psia, compared to 484 psia initial bottomhole pressure, in the five major carbonate layers in the Chase reservoir, (2) The three more permeable layers had the lowest pressure and were being effectively and efficiently drained while the less permeable layers had the highest pressure and were being effectively, and possibly efficiently drained, by original wells 2,100 feet to 3,300 feet away, (3) The wireline pressure testing results were accurate and precise, but often not representative of the layer pressures in the individual layers, and (4) The various testing operations require extra planning in a foam system due to underbalance conditions and conflicting wellbore fluid requirements.
Feasibility Study for the Drilling of a Horizontal Well in the West Panhandle Field
Authors: Taylor L. L. , Carden R. S. , Selinger K. A. 
Published: December 2007

ABSTRACT
Choosing the proper application is crucial to the success of any horizontal well. Many horizontal wells drilled in the past were technical successes and economic failures. Thousands of horizontal wells have been drilled in the last five years, but most have targeted oil reservoirs with relatively low permeability and high pressures. This paper considers the applicability of horizontal drilling to a large gas reservoir with high permeability and low pressures. More specifically, it discusses an approach for evaluating the economics of drilling such a well in the West Panhandle Field