bluuebunny/crossref_metadata_2025 huggingface dataset:
An Evaluation of Water Reduction Treatments to Improve Vertical Lift Performance
Authors: Sabut Bangkong , Banu Nazrin , Davidson Colin J.
Published: December 2007

Baram Delta Operations (BDO) consists of a collection of nine producing oil fields located offshore Miri, Sarawak, Malaysia and operated by Petronas Carigali Sdn Bhd (Sarawak Operations). Production wells typically comprise dual strings with each string being completed with a single internal gravel pack straddling several producing intervals. In some strings high water production from a particular interval retards oil production from the other intervals by reducing vertical lift efficiency and in these cases water reduction technology was evaluated as a potential oil stimulation technique. Due to the completion configuration, PLT assessment could be of limited value and selective placement of plugging chemicals into target intervals was not considered a viable option. Thus despite the higher degree of uncertainty associated with the use of chemicals designed to selectively reduce water permeability (with little or no impact on oil permeability), these were considered the only viable option for potential application within BDO. Based upon independent confirmation of vendor submitted core flow test data, a linear, amphoteric polymer system was selected for field testing. The results of the core flow tests suggested that for intervals of high water saturation, treatment with the linear, amphoteric polymer system could reduce water permeability by about an order of magnitude while in intervals of high oil saturation, relative permeability to oil would be largely unaffected. Despite the highly encouraging laboratory results, an initial two well field test programme failed to prove the technology in the field. While the first field test failed due to operational difficulties, the second was a clear operational success but did not lead to reduced water production. Despite intensive post job analysis, the very wide discrepancy between the laboratory and field results has yet to be satisfactorily explained.
Application of a Multi-Purpose Compositional Simulator in Designing Steam Injection Projects
Authors: Cicek O. , Ertekin T.
Published: December 2007

In the design of an optimum enhanced oil recovery operation an accurate areal and vertical mapping and analysis of the simulation results plays a fundamental role. In this type of analysis not only should the finer details of the reservoir be considered, but also the grid system superimposed over the domain of interest should exhibit compatibility and consistency with the actual physics of the problem. This will help in accurate characterization of the reservoir and the ongoing physical processes within the domain of interest.

The implications of the aforementioned statements are investigated with the aid of developing a 3-D fieldscale steam injection simulator. The multi-phase mass and energy transport equations are based on compositional balances. In the model the gravitational and capillary forces are accounted together with the viscous flow phenomenon. A fully implicit treatment is used at the multi-block production and injection wells to couple the wellbore to the reservoir. A fully implicit technique is utilized in the solution of the nonlinear system of equations. The model is capable to solve (nhc+5) primary variables simultaneously where "nhc" represents the number of hydrocarbon components that can be considered.

A systematic analysis of the areal and vertical distribution of parameters such as pressure, temperature, phase saturations and composition is conducted. Through this detailed analysis the ever-changing relative effects of the various dominant forces on the establishment of production mechanisms and ultimately on the oil recovery are studied.

The fully implicit formulation, which assumes all the reservoir parameters and operational parameters to be functions of all primary variables identified, makes it possible to focus on any parameter and investigate its effects on oil production. Both qualitative and quantitative implications of capillary pressure on the oil production are observed to be strong functions of the size and uniform nature of the grid constructed over the computational domain.

The proposed model provides some significant insight into the displacement mechanisms and aids us in developing a comprehensive understanding of the nature and magnitude of the forces and controlling parameters. Such an understanding will help in the design of specifics of a recovery operation.
Stability of Junctures for Multilateral/Multibranched Wells
Authors: Fuentes J. A. , Economides M. J. , Carbonell R. S.
Published: December 2007

In creating complex well architecture a primary exercise is the initiation of a second branch from an existing "parent" or "mother" hole. The latter can be vertical, inclined or horizontal. The branch can be initiated at a range of angles depending on the drilling hardware used. In creating this angled branch from the main branch the stress concentration at the juncture depends greatly on the state of the far field stresses and their relative magnitudes and the mechanical properties of the rock. This work shows the calculation of the resulting state of stress at an open-hole juncture of two wells and along with a failure criterion delineates the stability of the new hole. The analysis is carried out for an angle of kick off of 2.5° and rock mechanical properties and far-field state of stress characteristic of a formation in Lake Maracaibo, Venezuela. Comparison of the estimated state of stress by the model and the rock failure criterion, predicts no mechanical instabilities at the juncture for this case. The analysis presented here demonstrates that it can be a useful tool for planning multilateral/multibranched wells by seeking formations that can withstand the stress imposed at the kick-off point and by orienting the initiation of the second branch in a direction that can ensure stability at the juncture.
Application and Prospect of Fine Water-Plugging Technology in High Water Cut Period
Authors: Liu He , Wang Zhongguo , Xu Guomin
Published: December 2007

This paper presents the development of water plugging technology under such situation that the number of casing damage well increases continuously and overall water cut goes up year by year with the extension of production time in XingBei oilfield. Its main contents are as follows.

Internal thick oil layer chemical water-plugging technology which aims at tapping the potential of remaining oil in the internal thick oil layer. Pay zone group mechanical subdivision water-plugging technology that aims at liberating the plugged layer accompanied. Small diameter mechanical fine water plugging technology which aims at tapping the potential of casing damage well with a diameter more than • 95mm. Layer adjustable mechanical water-plugging technology to simplify the operation procedure. Thus, a set of matching water-plugging technology according to different state of well and property of pay zones’ development is formed. Meanwhile, the field application results and adaptability of all water-plugging technology are evaluated, which makes it clear what is key problem to fine water plugging in the future of oil field. And also the prediction of the prospect and potential of water plugging technology in popularization and application.
Study on the Quality of Polymer Flooding Produced Crude Oil
Authors: Ruiquan Zhang , Wei Kang , Shujuan Hu , Shouguo Song , Baochun Zhou , Fujun Xia
Published: December 2007

The influence of polymer flooding on the quality of crude oil was investigated in this work. No significant differences between the quality indexes of crude oil produced by water flooding and polymer flooding in the same reservoir block have been found.
Case History: Carbon Dioxide Foam Stimulates Rome in Eastern Kentucky
Authors: Rodvelt Gary , Dials Gregory Allen , Hay Monte
Published: December 2007

Over the last 10 years, operators searching for commercial reservoirs in the Rome Trough have been unsuccessful. The complex mineralogy of the Rome sand made completion-fluid design a challenge. Core analysis indicated that the formation was sensitive to conventional fluids, and high fracture treating pressures precluded stimulation with nitrogen foam. Consequently, engineers designed a carbon dioxide foam, which they pumped through 2 ⅞-in. J-55 tubing for fracture stimulation of the Rome interval. Treatment fluids cleaned up in 2 days and the well began producing 250 mcf/day. This unique treatment allowed operators to stimulate zones previously considered unsuitable for commercial production, and it generated additional drilling locations.
Coiled Tubing Conveyed Fracture Treatments: Evolution, Methodology and Field Application
Authors: Gulrajani Sunil , Olmstead Clinton C.
Published: December 2007

A common limitation of fracture stimulation is the inability to control placement of a hydraulic fracture. This shortcoming compromises the effectiveness of a fracture treatment for multistage treatments during early field development, as well as single stage fracture stimulation of bypassed zones in mature reservoirs. This limitation can be overcome by integrating coiled tubing with hydraulic fracturing. This combination adds versatility to the fracturing procedure. It also permits control of fracture placement and hence can be used to improve the economic benefits associated with hydraulic fracturing.

The effectiveness of coiled tubing fracturing operations can be constrained by excessive friction pressures, equipment limitations and limited fluid and proppant volumes. Its application thus requires specialized fracture fluids, additional field operational considerations, and alternative design procedures to ensure an efficient and successful fracture stimulation program.

The paper initially explains the motivation for coiled tubing fracture treatments. Operational and design requirements associated with this technique are then outlined. Two case studies are finally presented to illustrate the application of the coiled tubing fracturing procedure.
Integrated Reservoir Evaluation Revives Nearly Abandoned Illinois Basin Field
Authors: Aman B. A. , Nichols T. W. , Snyder R. L. , Payne M. E.
Published: December 2007

Reservoir evaluation for the purpose of production enhancement is generally conducted by the reservoir or production engineering department, which then forwards results to subsequent departments for review. Increased evaluation time and lack of synergy between disciplines during the evaluation process may result in bypassing significant reserves or pre-mature field abandonment. The evaluation of a nearly abandoned field in White County, Illinois was performed through a team approach, which integrated engineering, geology, operations, and management into a seamless network. This allowed the evaluation to proceed effectively, with each discipline having access to current evaluation data on a real-time basis.

Evaluation methodology and team integration techniques were beneficial in reviving this sucrosic dolomite carbonate field that generated cumulative production of over 279,000 stock tank barrels of oil, but had declined to less than 5 barrels of oil per day, making the field uneconomical to operate. Reserve evaluation, geological interpretation, production operations facilities, and economics were brought together in an attempt to prove and produce additional reserves. Computer modeling was also used to test and validate different scenarios to optimize recovery and cash flow from the project. This paper will describe the reservoir, geologic environment, production and recovery method, and the economic advantages of the project, as well as show the benefits of reservoir evaluation from a team perspective.
An Update On Use of Coiled Tubing for Completion and Recompletion Strings
Authors: Scott W. S. , Hoffman C. E.
Published: December 2007

The paper discusses various recent completions and recompletions using coiled tubing strings. Schematics and discussion of the following completions are included: Patches, Screens and Gravel Packs, Velocity and Siphon Strings, Artificial Lift with Gas Lift, Jet Pumps, and Plunger Lift, Tail Pipe Extensions, and Zone Isolations.
Virtual Well Testing
Authors: Dakshindas S.S. , Ertekin T. , Grader A.S.
Published: December 2007

Well test analysis represent an essential component of reservoir engineering analysis and management. It provides estimates of reserves, heterogeneties, permeabilities, and information on the status of wellbore conditions. A well testing program can become prohibitively costly due to equipment and personnel costs and lost production. It may not be possible to design an effective well testing program that includes all the important wells in a specific field. In this paper, a novel "Virtual Well Testing" approach is presented. The new method uses artificial neural networks (ANNs) to generate virtual transient pressure data. The proposed method does not eliminate the need for traditional well tests, but provides a basis to extract more information from the existing sets of transient pressure data. In virtual well testing, transient pressure data from selected wells in the field are used to train a neural network that is capable of predicting transient pressure responses at other well locations where well tests have not been conducted. The proposed methodology can also be used for designing well tests and for completing the partially recorded pressure measurements due to malfunction of testing equipment.

This paper provides guidelines for selecting actual well test locations, for choosing input parameter neurons and for training the ANN. Several simulated case studies are used to train and evaluate virtual well testing capabilities of the ANN. The effects of the number of wells tested, well locations and production histories are evaluated. The ANN is successful in predicting interference effects and reservoir permeabilities. The ANN generates reliable virtual transient pressure data in a matter of seconds and is an effective reservoir engineering analysis and management tool.
Development Of Reservoir Characterization Models Using Core, Well Log, and 3D Seismic Data and Intelligent Software
Authors: B. R. Soto , Holditch S. A.
Published: December 2007

The degree of success of many oil and gas drilling, completion, and production activities depends upon the accuracy of the models used in a reservoir description. Neural networks have a number of attractive features that can help to extract and recognize underlying patterns, structures, and relationships among data. However, before developing a neural network model, we must solve the problem of dimensionality such as determining dominant and irrelevant variables. We can apply principal component and factor analyses to reduce the dimensionality and help the neural networks formulate more realistic models.

We have used an intelligent software, Oilfield Intelligence (OI)1, as an engineering tool to improve the characterization of oil and gas reservoirs. OI integrates neural networks and multivariate statistical analysis. It is composed of five main subsystems: data input, preprocessing, architecture design, graphics design, and inference engine modules. We validated OI by obtaining confident models in three different oil field problems: (1) a neural network in-situ stress model using lithology and gamma ray logs for the Travis Peak formation of east Texas1, (2) a neural network permeability model using porosity and gamma ray and a neural network pseudo-gamma ray log model using 3D seismic attributes for the reservoir VLE 196 Lamar field located in Block V of south-central Lake Maracaibo (Venezuela), and (3) neural network primary ultimate oil recovery (PRUR), initial waterflooding ultimate oil recovery (IWUR), and infill drilling ultimate oil recovery (IDUR) models using reservoir parameters for San Andres and Clearfork carbonate formations in west Texas2.

This paper presents the models that we developed using OI in C-4 and C-5 for the VLE 196 Lamar Field, Block V in Lake Maracaibo. We found that the best neural network permeability model should have as input variables porosity and gamma ray log. The coefficient of determination of that model is 0.9756 with an average absolute error of 18.03%. From non-linear regression and non-parametric approach methods, the absolute error of these models varies from 38.1 to 97.78%. For the same reservoir, we developed a high-quality, multivariate, and neural network model to predict the pseudo-gamma ray log from 3D seismic attributes. The data points used during the training, testing, and validation comprised approximately 11,800 points. Two dime/depth conversion tables were used to convert the arrival time of seismic to depth. We developed a Fortran-90 program to make that conversion. The confidence of that model is around 90% with an expected absolute error of 11%.

In all cases, we compared the neural network models with the non-linear regression and non-parametric approach models. The results show that one of the ways in the near future to get better reservoir characterization models is using neural networks in conjunction with the multivariate statistical techniques.
World Record Horizontal Bit Runs in Oman
Authors: Geldof Wilco , Merrall Eric , Kent David , Dautel Mike
Published: December 2007

Continuous performance improvements resulting in two consecutive World record horizontal drilling bit runs have been achieved by Petroleum Development Oman (PDO) and its well engineering partners in the Saih Rawl field of North Oman. This paper captures the critical technology and management success factors that both made this achievement possible and point the way forward to further improvements in overall well time and project economics.
Translating Health, Safety, and Environmental Values into Performance
Authors: Radwan Kamal
Published: December 2007

Establishing a safety culture – and ensuring that employees internalise the culture's values – doesn't just make good sense; it makes good business sense. Therefore, it is incumbent upon every company to firmly establish a safety culture and make a concerted effort to convey the value that the company places on safety.

Effective, internalised safety efforts reduce injuries and incidents; assist in the attainment of a sustainable world-class safety culture; lower employees compensation, insurance and lost workday case costs; lessen the likelihood of damaging the environment; and reduce the possibility of legal liabilities. Plus, an improved safety performance actually leads to increased productivity and profitability.
Safety Case for Mobile Offshore Drilling Units in View of Offshore Safety Legislation and Forthcoming ISM Code
Authors: Gupta P. K.
Published: December 2007

Operations at Mobile Offshore Drilling Units (MODUs), deployed for exploration and exploitation of oil and gas in offshore area, are more hazardous and complex in nature due to intricate engineered systems & hostile marine environment and ultimate safety goal is safety of life, installations and environment. A systematic and proactive approach towards safety is of paramount importance for efficient and cost effective operations at MODUs. "Safety Case" is a documentary proof, which is to be submitted by the operator to the Regulatory Bodies to demonstrate that the hazards associated with the operations are identified and adequate resources are in place to control and mitigate those hazards. In India, Offshore Safety Legislation, which is an offshoot of the Lord Cullen's Enquiry Report recommendations on Piper Alpha Disaster, is in final draft stage and it has been written in goal setting terms for safety of life & installations in offshore oil & gas fields of India.

"Safety Case" means a document prepared by an operator to demonstrate that the hazards in the offshore installation have been identified, risks assessed and the adequate resources and the control measures are in place for safe operations. It mainly includes:

Description of MODU's facilities Formal Safety Assessment (FSA) Safety Management System (SMS)

Safety Case ensures that:

All hazards associated with MODU's operations with potential to cause major accidents have been identified and their risks evaluated. Adequate measures are taken to reduce risk to as low as reasonably practicable (ALARP). Management system is in place to ensure compliance with statutory requirements. Adequate resources are onboard MODU to control and mitigate the identified hazards. There is a system for audit and audit reporting.

Further this system will also facilitate the operators of MODUs for compliance to forthcoming "International Safety Management (ISM) Code" which will be effective from July 2002 for all self propelled MODUs.

This paper discusses the elements of Safety Case, major hazards, development of SMS & documentation requirements for MODUs in view of forthcoming ISM Code.
Bit Optimization in Kuwait
Authors: Al-Saleh Ali
Published: December 2007

Although bit cost comprises a relatively small fraction in a well's budget (+5%), bit performance's impact on overall well cost can be significant. This paper will discuss bit optimization in the Kuwait fields. The paper will address the approach and methods used which include optimizing access to technology, incentive performance and utilizing new technologies.

All this was done in a team environment with the bit manufacturers, which ensured better communications and better access to data.

This approach proved to be effective in reducing the average cost per foot and resulted in drilling cost savings for development wells which will be presented in the body of this paper.
Rig Equipment Planning for a Deep, Deviated High-Pressure/High Temperature Khuff Well
Authors: Hadj-Moussa Noureddine
Published: December 2007

In order to drill and complete safely and successfully an offshore Deep Deviated HP-HT Khuff Gas Well, a good study and planning of Rig Equipment and necessary conversions and upgradings must be, carefully, carried out to handle all required drilling and completion operations.

The areas of concern shall include, but not limited to, Drill String, Drilling Machinery, Derrick, Well Control Equipment, Surface Gas Handling Equipment and Health, Safety and Environment.
Cost-Effective Development of Qatar's Al Shaheen Field Through Continuous Drilling Optimisation
Authors: Rønnau Hans-Henrik , Nørrelund Jesper , Dilling Stig , Pitts Michael J. , Jeppesen Morten W.
Published: December 2007

This paper was prepared for presentation at the 1999 SPE/IADC Middle East Drilling Technology Conference held in Abu Dhabi, UAE, 8–10 November 1999.
Designing Effective Zonal Isolation for High-Pressure/High-Temperature and Low Temperature Wells
Authors: Biezen Ewout , Ravi Kris
Published: December 2007

In recent years, many wells have been constructed that are subject to extreme conditions. Two extreme conditions that can pose a particular challenge during the completion of a well are low temperature, for example in deepwater applications, and high-pressure and high-temperature, encountered in HPHT wells. The products and processes that are normally used to cement wells may be insufficient to create zonal isolation for these extreme conditions.

This paper presents methods to help design and execute effective cement jobs for HPHT and deepwater, low temperature wells. First of all, recommendations are outlined for the deepwater conditions. Drilling fluid removal, sealant placement, and sealant sheath strength development are all affected by extreme conditions and are therefore designed accordingly. In order to help determine how strong the sealant sheath needs to be, formation properties are taken into account as well as the operations to be performed during the life of the well. These operations include well testing, stimulation, production, and injection.

The paper goes on to discuss the advantages of new products and processes for cement wells under extreme conditions. The laboratory testing procedures, pre-job design procedures, job implementation and evaluation procedures that were used to test the new products and processes are described. Finally, guidelines are given for optimized designs for HPHT and low temperature wells using these products and processes.
Integral Maintenance Plan Applied to Offshore Facilities in Campeche Bay
Authors: Rodriguez Victor M. , Aguila Miguel A.
Published: December 2007

The new Petroleum Competitive Landscape requires focusing the strategic management to reduce Operation Expenditures (Opex). A determinant factor in Opex is the investment in infrastructure and process equipment Maintenance in offshore facilities of Pemex exploration & production in Campeche bay.

This paper development a Competitive Strategy of Integral Maintenance its aim is to keep 31 offshore fixed platforms and 153 kms. Of pipelines in optimal safety and operational conditions, and to keep the environmental conditions.

The Integral Maintenance Plan (IMP) is going to stablish in a short period and to give us the next benefits:

□ Reduce the risk in platforms □ Increase the Reliability of facilities □ Reduce the opex in maintenance □ Exchange the policy of maintenance from corrective to preventive □ Reduce the expenditures in insurance □ Keep the facilities in World-Class.

Apply this IMP require economical resources of 147 million DLLs and in a period of ten years will give us a benefit of 466 millions DLLs. These earnings represent 4% of yearly oil exportation of Mexico.
Design and Development of Hydrocarbon Surface Production Facilities and Pipelines Based on Process And Transport Simulators
Authors: Castillo M. P. , Murillo M. , Cabrales C.
Published: December 2007

Among the main objectives of Pemex Exploracion and Produccion Region Sur is found the analysis of the operation, the optimizacion and the modernization of the systems of produccion, transportation and distribution of hydrocarbons, in order to provide better security conditions, efficiency and opportunity, without forgetting the proteccion to the environment and the society.

For the foregoing, it results from great importance to count on a methodology for planning the behavior and development of the infrastructure of produccion and transportation to face current and future needs, bearing in mind the operational requirements and quality that demand best engineering practices.

The utilization of Process and Transport Simulators to analyze the facilities in the current operation conditions, and to predict their behavior under different stages is a valuable tool that applied combined with the best practices of engineering allows to predict, with meaningful time savings, the necessary modifications to be adjusted to the new operative philosophy, without putting on risk the facilities.

As added value, the results obtained from the application of this methodology also contributes to the construction of a data base, of the facilities of produccion as well of transportation, of great usefulness for activities related to the maintenance programs.

The results of modeling are completed with an economical analysis in order to find the best alternative to solve a particular situation. The obtained information is documented and ordered to justify the new projects and the required investments.
Elaboration of Analysis Studies of Risks to Production and Distribution Facilities of Gas
Authors: García F. , Castillo M. P. , Peña P. J.
Published: December 2007

The inherent hazards in the Production and Distribution Facilities of Gas of the Mexican Southeast, particularly in the Compression Stations, with their respective consequences, combined with the probabilities of the fact that occur, represent different risk levels that they can be detected timely with the application of techniques recommended by the API, OSHA and AICHE. The application of such technical and the modelling of the worst scenarios, using a specialized software, permits us also to determine the affectation areas (by fire, explosion and/or toxic concentration by emissions to the atmosphere) that would be presented in the supposed case of an accident in the Compression Stations.

The group of these techniques and the modelling of the scenarios form part of a Analysis Study of Risks, which is a powerful tool of the Risks Administration that contributes to a better performance of the safety levels in the facilities. For this reason was effected the Analysis Study of Risks to 40 compression units of 5 facilities.

In the study were employed qualitative and quantitative techniques such as: the Checklist, Hazard and Operability Analysis (HAZOP), Operation and Maintenance Log Data Analysis, Analysis of Failures Tree and Modelling of Scenarios.
The Application of New Generation CaCl2 Mud Systems in the Deepwater GOM
Authors: Paul D. , Mercer R. , Bruton J.
Published: December 2007

A new generation calcium chloride (CaCl2)/polymer-base drilling fluid system has been developed and successfully applied in the deepwater Gulf of Mexico. The system was developed specifically to address the myriad of operational problems associated with drilling the highly reactive, gumbo-laden clays found throughout the Gulf of Mexico.

This paper describes the evolution of these systems and the lessons learned during this experience, including mixing and shearing procedures to eliminate the shaker screen blinding seen on wells drilled with first generation CaCl2 systems.

The authors will present the application of the newest generation CaCl2 system, which employs a uniquely engineered encapsulating polymer. Among the field trials to be reviewed is one from a newly built drillship, which used the system to drill its debut well in the deepwater Gulf of Mexico. Further, the paper examines the performance of this new system compared with other water-based systems traditionally used to drill similar intervals.

Experience from several wells employing calcium chloride/polymer systems and evolutionary modifications to improve their efficiency will be discussed. These sequential improvements have allowed the development of a decision tree to determine optimum applicability.
Research and Application of Recirculating Foam Drilling and Completion Fluid
Authors: Sui Yuehua , Cheng Xiaohua , Sun Qiang , Ji Hongtao , Gao Jianli , Gao Qinghua , Zhuang Zhiwei , Qing Jishun , Zhou Aizhao
Published: December 2007

The re-circulating foam drilling and completion fluids (RFDCF) is a low density system developed by Shengli Drilling Mud Company of China. Its outstanding advantages are that no special equipment needed in field operation, the density can be adjusted between 0.60-0.99g/cm3 and can be re-circulated. The laboratory evaluation proves that the density of RFDCF decrease with the increase of temperature and is always lower than 1.00g/cm3 even in the pressure of 40Mpa. The on-site application in 48 wells proves that it can be used in high-angle well, horizontal well and under-balance drilling operation. It successfully solves the serious loss in buried hill formation of Shengli Oil Field and make important break through in oil production from igneous rock formation. The use of RFDCF greatly cut down the drilling expense and makes significant economical and social benefit.
Details of In Situ Foam Propagation Exposed with Magnetic Resonance Imaging
Authors: Wassmuth F. R. , Green K. , Randall L.
Published: December 2007

Transient and steady state foam propagation experiments in carbonate packs were imaged with a Magnetic Resonance Imaging (MRI) instrument. In situ saturation profiles can be resolved with MRI to a greater degree than previously tried methods.

Transient foam propagation experiments were carried out by co-injecting surfactant solution and gas into water saturated, carbonate packed, cores. In the case where surfactant adsorption was not initially satisfied, a unique water saturation wave developed between the advancing gas front and the lagging foam (lagging due to surfactant adsorption). In the experiment where surfactant adsorption was satisfied before injecting the foam, a stable foam front propagated at a rate close to the combined gas and liquid injection rate.

Steady state foam experiments were carried out at a variety of foam qualities. The saturation profiles along the length of the carbonate pack demonstrated two distinct regions, the foam generation region in the first 3 cm of the core and the foam propagation region in the remaining part of the core. With the enhanced resolution of MRI, small saturation changes with change in foam quality were evident in the foam propagation region. Previously, such small changes in liquid saturations during foam experiments were ignored and lumped together into the critical water saturation required for foam propagation.
Asphaltene Precipitation and Alteration of Wetting: Can Wettability Change during Oil Production?
Authors: Al-Maamari Rashid S. H. , Buckley Jill S.
Published: December 2007

Wettability controls the distribution and flow of immiscible fluids in an oil reservoir and thus plays a key role in any oil recovery process. Once thought to be a fixed property of each individual reservoir, it is now recognized that wettability can vary on both microscopic and macroscopic scales. Polar oil components can adsorb onto the pore-bounding mineral surfaces by several different mechanisms. In this study, we explore a transition in the mechanism of wettability alteration that relates to the asphaltene fraction and its stability in the oil phase.

Asphaltene stability was varied by addition of n-heptane to samples of five crude oils. Conditions ranged from asphaltene stability to mixtures in which aggregates formed and separated from the oil. The onset condition—where the first asphaltene particles become visible—was used as a reference point with respect to asphaltene stability in each crude oil sample.

Muscovite mica sheets, treated with brine and with the crude oil-heptane mixtures, were examined using contact angles between decane and water as a measure of altered wettability on the oil-treated surfaces. A significant increase in oil-wet conditions very near the onset of asphaltene precipitation was observed with four of the five oils, indicating the potential for wetting changes during the course of oil production if conditions of asphaltene instability are approached. Implications of changes in the mechanism of wetting alteration during the course of production from an oil reservoir are considered.
A Process-Based Approach for Three-Phase Capillary Pressure and Relative Permeability Relationships in Mixed-Wet Systems
Authors: van Dijke M. I. J. , Sorbie K. S. , McDougall S. R.
Published: December 2007

In the reservoir simulation of three-phase displacement processes, the saturation dependency of three-phase relative permeabilities is of central importance. However, little is known a priori about these saturation dependencies in nonstrongly water-wet systems. This behavior is intimately connected with the pore-scale physics of these displacements for the specific wettability state of the system. We refer to a model, which connects the macroscopic properties with the underlying pore-scale physics as a process-based model. In this paper, and in related work, such a model has been developed to determine the saturation-dependency regions of three-phase relative permeabilities. This processes-based model applies to both non-spreading and spreading oils for all types of mixed-wet and fractionally-wet porous systems that contain clusters of oil-wet and water-wet pores. Based on a classification of all allowed pore occupancies in a completely accessible porous medium, saturation-dependencies of the corresponding relative permeabilities are derived. The variation of regions in saturation space where the three-phase relations depend on either one or two phase saturations is determined and analysed in terms of the basic parameters of the model, i.e. range of pore size distribution, fraction of water-wet pores and the interfacial tensions (σgw, σgo, σow ).Furthermore, three-phase relative permeabilities that appear to depend only on their own saturations are either linked to the corresponding two-phase relative permeabilities or it is shown that such a link cannot be established. A comparison has been made with existing relative permeability models with respect to their saturation-dependencies.
CO2 Injection in the Weyburn Field of Canada: Optimization of Enhanced Oil Recovery and Greenhouse Gas Storage With Horizontal Wells
Authors: Malik Qamar M. , Islam M. R.
Published: December 2007

Recently, a billion-dollar CO2 injection project has been launched to increase oil recovery in the Weyburn field of Canada. Initially, the project will use 5000 tonnes of CO2 daily in 19 patterns. The background economic calculations use the assumption that miscibility will be achieved and a steady supply of CO2 at a cost of $35/tonne will be available. This paper provides detailed results of a comprehensive reservoir simulation study using a fully compositional model, in order to optimise the pattern and injection/production strategies.

The prototype reservoir models developed are by integrating geologic and petrophysical data available in the literature (1960-1998) for the Weyburn unit, in the southeastern part of Saskatchewan, Canada. The models provide successful history matching, optimise secondary and tertiary recovery schemes, predict an incremental oil recovery through improved oil recovery, and give an estimate of the subsurface storage capacity of greenhouse gases (GHG). The validity of the models developed is evident from the agreement obtained and the conclusions drawn from these diverse data sources that enabled a successful history match of the fluid movement in the reservoir. The models developed are robust in nature and helped determine key parameters controlling miscible CO2 flood. The effects observed due to the contaminated gas stream highlight several of the significant unexplained phenomena, faced by the industry. They are: role of impurities in controlling mobility of the injected gas, effect of impurities in the GHG stream, effect of the loss of miscibility, effect of gas injection directly into the bottomwater zone and the effect of bottomwaters transmissivity on oil recovery.

A technical conflict is encountered towards the optimal operating conditions for simultaneous objectives of higher recovery and higher CO2 storage. In this study, horizontal injection wells have proved to be efficient for CO2 flooding process to improve recovery while increasing the storage of anthropogenic CO2. Twenty-one different scenarios for two different schemes have been simulated and investigated simultaneously for storage and recovery. The incremental recovery is related to the flood injection operating strategies employed, introducing back pressure on the reservoir through injectors and producers. The CO2 flood front is controlled through horizontal well adjusting pressure, simultaneously adjusting water injection in the offsetting vertical injection wells and holding back pressure on the associated production wells. Efficient back pressure, achieved is by limiting high operating bottom hole pressure of the producers corresponding to those of injectors that helped maximise the vertical sweep. In addition, opting GOR strategy, location of the horizontal well, optimal injection rates helped to achieve conformance within the reservoir that enabled one to overcome the conflict of achieving the simultaneous objectives.
Influence of Geological Features on Well Test Behavior
Authors: Zambrano Judith , Zimmerman R. W. , Gringarten A. C.
Published: December 2007

Early recognition of porosity and permeability contrasts in a reservoir has economic implications in reservoir management. Reservoir characterization aims at developing a detailed knowledge of the geological heterogeneities that may affect production rates and recovery factors. In the area of reservoir characterization, geological and engineering data have been traditionally inverted separately: a 3-D static reservoir model is established from static data (geology, geophysics and petrophysics) and the parameter distributions in that model are adjusted by history matching with production and other dynamic data. The underlying assumption in this process is that production data correspond to the same model as static data (Floris et al.1; Landa et al.2). This may or may not be the case. Hence, the requirement to first identify separately a model for each type of measurement and to verify that each model is consistent with all the others. Because identification is an inverse problem, with a non-unique solution, it is also desirable to confirm each feature of the reservoir model with different types of measurements3. For some features this is possible with today's technology. For instance, well test analysis can confirm the location of a fault identified from geophysical measurements and vice-versa. Other features, on the other hand, require additional development.

The present work looks at the medium-scale architectural elements that have been formed in different depositional environments,, with the objective of reconciling geological and well testing modeling in order to increase the confidence in the evaluation of fault sealing, sandstone bodies geometry and lithofacies distribution. In this approach, the heterogeneities are regarded as geological objects characterized by geometrical parameters as well as by petrophysical properties. Synthetic genetic-type objects are generated by stochastically modeling their external geometries and internal rock-property distribution and their response in a well test is evaluated with the help of a numerical well test simulator. The systematic evaluation of the well testing responses of various geological objects yields a new source of reliable information for reservoir characterization.
Estimating Oil Reserves in Oil-Water Transition Zones
Authors: Christiansen R. L. , Heymans M. J. , Fanchi J. R.
Published: December 2007

The amount of recoverable oil in an oil-water transition zone depends on the distribution of oil saturation as a function of depth, and the relationship between initial oil saturation in the transition zone (Soitz) and residual oil saturation in the transition zone (Sortz). Traditionally, it is assumed that Sortz is the same as the residual oil saturation in the oil column (Sor) above the transition zone. However, data in the literature show that residual oil saturation depends on initial oil saturation. So, residual oil saturation in the transition zone (Sortz) should be a function of initial oil saturation in the transition zone (Soitz). The relationship between Sortz and Soitz is referred to as a trapped oil relationship.

The purpose of this paper is to show recent experimental corroboration of the trapped oil relationship and to demonstrate the impact of the trapped oil relationship on reserves determination in oil-water transition zones.

First, fundamental issues for appropriate selection of rock-fluid properties for characterizing transition zones are addressed. Graphical illustrations are presented to compare and contrast conventional methods for characterizing transition zones with an improved characterization method that requires additional rock-fluid property measurements.

Then, results from laboratory studies of recovery from transition zones are used to demonstrate features of the improved characterization method. These results show that oil in the transition zone is much more mobile and recoverable than is assumed by the conventional approach.

For these laboratory studies, unconsolidated packs of sand, glass beads, and plastic beads were used. The media were varied to observe the effects of wettability and grain size on transition zone properties. It is believed that the variety of media qualitatively represent what would be observed for actual reservoir formations. Local saturations in the transition zones were correlated to gray level of video images of the surface of the packs. The laboratory methods for unconsolidated media could be extended in the future to reservoir rock (having much lower permeabilities) with centrifuge technology.

Finally, the effect of the trapped oil relationship on reserves determination is shown with an extended black oil simulation that incorporates the effects of relative permeabilities on reserves determination.
Gas Management in a Large, Complex, Miscibly Flooded Oil Field
Authors: Dunn M. D. , Lagerlef D. L. , Chamberlain J. A.
Published: December 2007

The Kuparuk River Field, on the North Slope of Alaska, is an extremely complex system when predicting and managing produced gas and artificial lift gas. Encompassing an area of almost 200 square miles, it is one of the largest full-field waterfloods in the world. On a daily volume basis, it is the second largest miscible gas flood in the world, second only to Prudhoe Bay. The field has approximately 400 gas-lifted wells and a dozen wells on ESPs. Currently, the field is characterized as "formation gas constrained" because wells over a formation GOR of ~6000 scf/bbl must be shut-in. Fluids are processed and gas is compressed at three different processing plants, with some processes being shared between plants, and other processes being independent. Combined with a reservoir that is composed of two distinctly different sands, makes reservoir management and particularly gas management, an extremely challenging task.

In late 1998 a multi-disciplinary team was assembled to develop a framework and implement tactics that would better optimize gas handling at Kuparuk. At the time, several nearby "satellite" fields had just come on-stream that further taxed the existing gas handling capacity and oil prices were such that expansion projects were unattractive. This Gas Management Team was charged with optimizing reservoir, gas lift, and equipment performance. This required developing a better understanding of the leveraging mechanisms and processes, and communicating a set of tactics that could be implemented by the Organization.

This paper discusses the work of the Kuparuk Gas Management Team, composed of EOR, reservoir, optimization, and process engineers. This team studied the various facets of gas injection, gas production, gas storage, and gas lift to establish a plan to optimize this system. Efforts and topics that will be discussed are as follows:

More consistent measures of gas handling capacities Methods to improve forecasts of gas production Identification of the reservoir management "levers" that effect gas production Definition of the value of gas lift and the importance of quality data

Results to date show the optimization target was significant, and that much of it was achieved by applying the recommended tactics. This paper should benefit anyone who is working large fields where gas is re-injected for disposal or EOR purposes. It should also benefit those working gas-lifted fields where the value of gas lift must be understood in order to optimize the entire system.