bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the Discount Rate in the Absence of Capital Markets
Authors: Ransome G.
Published: December 2007

Traditionally debt and equity Capital Markets are used by firms in determining risk-adjusted discount rates. In countries where capital markets do not exist the discount rate is often determined subjectively.

This paper presents a novel approach for determining the discount rate for Exploration and Production projects by circumventing the use of the market determined rate on equity.
A Financial Analysis of the Natural Gas Industry of Trinidad and Tobago
Authors: Ramlal V. , Boopsingh T. M.
Published: December 2007

The natural gas industry of Trinidad and Tobago is divided into the upstream and the downstream, the latter including the transmission company. Past financial data was collected for both the upstream and downstream, and a computer model was generated that incorporates the upstream with the downstream. Financial projections were made that took into account plant expansions or renovations to the year 1996.

In this paper the relationships between gas price, profit and taxes for the upstream and downstream are investigated, and several combinations of upstream and downstream gas prices and their resulting effect on profitability and taxes are considered. An optimum gas price scenario is sought in order to facilitate further development of the gas industry. The significance of the natural gas industry as a foreign exchange earner is also discussed. The paper concludes that the current pricing system may be close to the optimum, if speedy development of the country's natural gas resources is the principal objective of the system.
Design of Tracer Tests for Natural Gas Underground Storage Operations - A Simulation Approach
Authors: Yeh Y. J. , Kuo M. C. T.
Published: December 2007

Chinese Petroleum Corporation started the import of Liquified Natural Gas (LNG) from Indonesia in 1990 and utilized a depleted gas reservoir, Tiehchenshan Gas Field, to store the surplus LNG. With a compositional reservoir simulator, this paper investigated the feasibility of using CO2 as a tracer for monitoring the flow path of injected LNG. The CO2 content in the Tiehchenshan gas and Indonesia LNG is around 2 mole % and 0 mole %, respectively. The simulation results indicated that monitoring the CO2 concentration change at the producing wells would help understand the flow path of the injected gas and the reservoir description for Tiehchenshan Gas Field.

Currently, compositional simulators seldom take the radioactive decay into account. This paper successfully developed a simple method which would allows the users of compositional simulators to design a test using a radioactive tracer. The simulation results showed that the mechanism of radioactive decay must be taken into account during the design and analysis of radioactive tracer tests for underground gas storage operations.
Steamflooding Experiences at Petrotrin (Trintopec's Operations): A Historical and Technical Perspective
Authors: Khan J. , Lewis W. , Maharajh D. H.
Published: December 2007

Thermal oil recovery was first initiated in Trintopec's operations in 1966, with a small cyclic pilot project in the Company's Palo Seco field. Since that inception, twenty-seven (27) years of thermal recovery, comprising both cyclic and flood-type operations, have witnessed vigorous growth and dynamic expansion to the extent that, by 1993, the thermal recovery statistics of Trintopec's portion of the now overall Company's (Petrotrin's) operations are as follows : Steamflooding operations exist in all the major land fields, viz.: Palo Seco, Central Los Bajos, Guapo, Fyzabad and Apex-Quarry /Coora/Quarry.Production from thermal recovery averages 7,500 bopd, representing 50% of current land production.A total of approximately 40,000 bspd is being supplied by twenty-three (23) steam generators to more that one hundred and fifty (150) injectors

This paper presents highlights of Trintopec's experiences in the design, implementation and operation of its thermal oil recovery schemes. New concepts, innovations, modelling and monitoring techniques over the past twenty-seven (27) years are outlined.
Heavy Oil Recovery by Subcritical Carbon Dioxide Flooding
Authors: Srivastava R. K. , Huang S. S. , Dyer S. B. , Mounts F. M.
Published: December 2007

The immiscible CO2 displacement process appears to be a very promising enhanced oil recovery technique for thin or marginal heavy-oil reservoirs where thermal recovery methods are generally unsuitable. This paper discusses results of laboratory and simulation studies for determining oil recovery mechanisms and displacement characteristics for this recovery method. Phase behaviour, linear coreflood, and scaled model studies were conducted with a medium heavy oil (14°API gravity) from a thin, sandy reservoir. The effects on oil recovery of reservoir operating pressure, CO2 injection rate, waterflood rate, CO2 slug size, and secondary and tertiary WAG (water-alternating-gas) schemes were examined. Oil recovery behaviour for a CO2 presoak process (which involves secondary or tertiary CO2 preflush followed by extended waterflood) was also investigated.

Study results indicated that oil swelling and viscosity reduction were the predominant recovery mechanisms for the subcritical CO2 displacement process (operating at 2 to 5 MPa, 28°C) with the oil. The CO2 presoak process improved the oil recovery because of higher mass transfer of CO2 into oil. A reduction in either waterflood rate (or CO2 injection rate) resulted in an increase in oil recovery and showed the interplay of viscous, capillary, and diffusive forces. The incremental oil recovery data, in conjunction with the CO2 requirements, showed that a slug size of approximately 0.4 pore volume (PV) was suitable for laboratory CO2 flooding studies. An increase in the operating pressure improved oil recovery for the CO2 water-alternating-gas (WAG) processes in sandpacks saturated with stock tank oil. However, the recovery in reservoir-fluid-saturated sandpacks was relatively insensitive to the operating pressures investigated, indicating mobility effects to be dominant in laboratory coreflood studies. Poorer oil recoveries for the secondary than for the tertiary WAG process were attributed to the high mobility of the injected CO2 gas. The CO2 presoak and WAG processes appear to offer strong potential for enhancing oil recovery from thin heavy oil reservoirs.
Selective Technique for the Resolution of Oil and Gas Transportation Networks
Authors: González J. , Rotolo M. A. , Suárez S.
Published: December 2007

An algorithm for the analysis and simulation of isothermal networks under steady state flow conditions that could be fed by one or more fluids(liquid or gases), was developed. The algorithm allows solving the network once the fluid properties and the node pressure are known.

The system of equations representing the network is generated through a selective method consisting in dividing the network into open/closed subnetworks, and generating the specific equations system for each subnetwork. Identification of network loops and their pipes was obtained by applying Graph Theory1.

Algorithm validation was carried out by comparing the results, for typical networks2 , with those obtained from the simulator P1PEPHASE3, while effectiveness of the selective method was assessed by comparing its execution times with those of standard methods (node and circuit methods).

Selective method proved to be more effective than the other two, by reducing the response times from 30–1800%.
Identification of Acute Toxicity Sources in Produced Water
Authors: Johnsen Stale , Smith A. T. , Brendehaug Johanne
Published: December 2007

Identification of acute toxicity sources in produced water has been considered an important task for the past few years. The present study outlines a new approach to the problem, where artificial produced water is made based on detailed knowledge of the composition and toxicity of produced water from two major North Sea oil fields. Acute toxicity testing by Microtox (Photobacterium phosphoreum) of produced water qualities made according to a statistical experimental design model, has in combination with multivariate statistical analysis identified the aromatic and phenolic fractions as the main contributors to the toxicity of these produced waters. Process chemicals did not contribute significantly.

A study of changes in acute toxicity and chemical composition during biodégradation of produced water verified that biodégradation of the aromatic and phenolic fractions played a dominant role in the decrease in acute toxicity.
Migrating Legacy Applications to Object-Oriented Frameworks
Authors: Barrett T. , Kennelly M.
Published: December 2007

During the 80's the message ’Wire up the enterprise’ led to a boom in networking computers together. Through the 90's this message will become ’Service up the enterprise’. Businesses will require their computing infrastructure to deliver 'services’ in a reliable, uniform and transparent manner, enabling them to operate effectively.

However it is not feasible or practical to replace many existing (legacy) applications with applications adhering to modern architecture specifications at once. Nor is it possible to have the bulk of the software developers retrained to object based programming overnight. This can only be achieved over the course of time. This document presents the issues encountered when we look to protect the investment made in legacy applications, together with a practical, incremental migration strategy.
Experiences in Incorporating a 3D Geological Model into a Reservoir Simulator
Authors: Rae S. F. , Neve Patrick
Published: December 2007

Advances in computing technology have allowed the development of sophisticated 3D cellular modelling and visualisation software which has found a variety of applications in the oil industry. This includes spatial attribute modelling and the visualisation of hydrocarbon reservoirs to improve the understanding of the geological structure including internal features, the distribution of formation properties and the movement of fluids once field production begins.

This paper discusses experiences gained in building a geological 3D model of the West Flank of the Alwyn North reservoir and the subsequent manipulation and transfer of this data into a 3D reservoir simulator for initialisation. The techniques used differ considerably from the traditional method using 2D surface mapping packages. The advantages of both geoscientist and reservoir engineer being able to see and review the 3D image of the reservoir at an early stage in the project is discussed. The paper covers the modelling of the reservoir's complex heterogeneities, the handling of both vertical and sloping fault surfaces, deviated wells and the contrasts in the number of cells of the geological model compared with the number of blocks in the reservoir simulation model. Procedures for up-scaling from geological to reservoir model are discussed along with the errors introduced in the transfer of data and subsequent re-sampling by different software packages.

The paper concludes with suggestions for future developments of software to further enhance this effective method of modelling.
Document Imaging: Adding Value to Engineering Drawing and Project Archives
Authors: Irwin W. T.
Published: December 2007

Technical innovations over the past several years now allow for electronic capture of paper-based information as rasterised images. In addition to increased efficiencies in archiving information, this technology offers new opportunities in retrieval, distribution, commentary, and revision of information.
The Cost-Effective Implementation of Production Operation Systems for a New North Sea Development
Authors: Shipton E. C.
Published: December 2007

The development of Kerr-McGee Oil (U.K.) PLC. 's first North Sea operation has provided an opportunity to install modem cost-effective systems in accordance with recent North Sea development philosophy. A greenfield site in Aberdeen provided the chance to install the operation from the cabling upwards and to select a local area network configuration to suit our particular needs. This paper describes how all of the required voice and data systems were installed successfully in a narrow time frame.
Partnering the Development of a New Client-Server-Based Drilling Information Technology System Results in Real Benefits
Authors: Sentance Andrew , Gillett Keith
Published: December 2007

This paper describes how the Drilling Engineering Applications Platform (DEAP) has been designed, built and implemented by a partnership of BPX and Baker Hughes INTEQ based on the open systems principles and a client - server architecture. Through the implementation of this system, real benefits have been realized in delivering information technology (IT) solutions to the partners’ business. By developing DEAP as a commercial rather than a proprietary product these benefits are available to other operators and contractors. In partnering the development of a commercial system, the development costs and risks were shared and the long term maintenance costs can be spread over a broad user base.
Computer Control of Oilfield Production in China
Authors: Song F. Y. , Teng X. S. , Yu G. P. , Islam M. R.
Published: December 2007

Daqing Oilfield is the largest oilfield in China. It provides 50% of China's yearly total oil production of 120 million tons. The no. 6 production plant of Daqing Oilfield is the pioneer in computer application for petroleum production in China. In 1981, the No. 6 production plant bought its first computer. In 1985, based on the comprehensive applications of computers, a network was built to connect all the information sources and decision making agents including production teams, technical service teams, geology teams, testing teams, production management and control offices. Later on, the operation system was put into the network. According to the specific situations in the oilfield, over 300 softwares were developed and their application was very fruitful. With the application of computers, oil production increased by over 1%, production cost decreased by 15%. Energy consumption and equipment damage are decreased. After the computerization in the oilfield, the no. 6 production plant gets economic benefits over 30 million Yuan (5 million U.S. dollars).
Reserve Optimization Utilizing Graphical Analysis Techniques
Authors: Chen Shing-Ming , Chen Li-Wei , George I. R.
Published: December 2007

The advent of small, powerful personal computers has led to the development of many inexpensive and comprehensive data analysis packages which allow the engineer to manipulate and display various types of test and field data. Without proper organization and a systematic approach, however, the benefit of such programs in obtaining an understanding of field production trends and mechanisms is often lost.

The objective of this paper is to present a method of displaying performance information in a simple and complete form to assist the engineer in visualizing (i) individual well behaviour, (ii) regional trends, and (iii) overall field performance.

Once the relevant data has been organized and displayed effectively, its use in the determination of

individual well production capability regional performance and inter-well communication reservoir pressure support and effectiveness of water injection oil recovery and possible reservoir extension

will be discussed. It will also be shown how this information can be used to identify wells requiring stimulations to improve productivities, as well as the need for infill drilling to maximize field recovery. Any gaps in the data, or the need for additional information required to assist in development planning, will also be apparent once the data is analysed.

Finally, for increased clarify, use of the techniques will be illustrated with field examples.
Portable, Computer-Based Rig Crew Training
Authors: Jardine P. F. , Waller M. D. , Kehase Berhane
Published: December 2007

Developing and maintaining high levels of crew expertise and awareness is vital to the productivity and safety of rig and platform operations. The effectiveness and longevity of onshore training can be enhanced through the use of training and simulation packages which staff and crews can use on demand at or near their work place. The widespread availability of, and familiarity with, personnel computers gives an ideal platform on which to build and operate such packages. In addition to the provision of basic training they also include performance enhancement so that both the user and supervisor can assess the levels of competence achieved. In addition to basic training the same platforms may be used as engineering aids, the simulators being used to assess the effect of changing parameters or methods of operation.
Implementing New Permeability Selective Water Shutoff Polymer Technology in Offshore, Gravel-Packed Wells
Authors: Gruenenfelder M. A. , Zaitoun Alain , Kohler Norbert , Ali S. A. , Linser T. M.
Published: December 2007

A new polymer, previously evaluated in the laboratory, has been successfully tested to shut off water production in two offshore high temperature gravel packed wells in the Gulf Coast. The polymer is shear resistant, thus easy to handle, and, since it maintains good permeability to oil in the zones into which it is injected, it does not require zone isolation during injection into the well. After treatment, a strong reduction in WOR was observed in both wells. The effect lasted over 2 years in one well and for several months in the second well. These treatments show that the polymer is stable in field applications at 190 and 200 °F (88 and 93 °C).
Evaluation of Tall Oil Fatty Acid Salt as a Steam/Foam Surfactant
Authors: Osterloh W. T. , Jante M. J.
Published: December 2007

We report the results of laboratory experiments designed to evaluate the performance of the sodium salt of tall oil acid, TOA, as a steam-foam surfactant. The objective of the experiments was to determine if this inexpensive material could be used to reduce the chemical costs of the steam foam process. Tall oil acid is a commercially available blend of oleic and linoleic carboxylic acids obtained by distillation of the wastes from pine pulping mills. The sodium salt soap, TOA−Na+, is easily produced by one-step neutralization of TOA with sodium hydroxide.

The performance of TOA−Na+was measured in terms of the rate and magnitude at which the foam pressure gradient, Vp, increased when TOA−Na+and nitrogen were injected into a two-foot sandpack. Performance was also measured as a function of temperature, TOA−Na+ concentration, foam liquid volume fraction, foam velocity, salinity, pH, and oil saturation.

Experimental results show that TOA−Na+ is an effective foaming agent that can produce pressure gradients of hundreds of psi per foot in a sandpack. The dominant parameters found to control TOA−Na+ performance were salinity, temperature, and pH. To generate a large Vp at high temperature and in the presence of oil, the salinity of the TOA−Na* solution had to be increased by adding between 1.0 and 1.5 wt% sodium chloride. The TOA−Na+ was effective up to 400°F, but a large Vp could not be produced at 500°F. The pH of the TOA−Na+ solution had to be greater than about nine to achieve a large Vp. Sodium sesquicarbonate was used to buffer the solution at a pH of ten. Other notable results include that TOA−Na+ foam performance was not adversely affected by oil and that stable foams were produced at high and low foam velocities and at low liquid volume fractions.
Improved Oil Recovery in the United States: The Race Between Technology Advancement and Resource Abandonment
Authors: Brashear J. P. , Biglarbigi Khosrow , Ray R. M.
Published: December 2007

Currently available enhanced oil recovery (EOR) and advanced secondary recovery (ASR) technologies could produce a significant amount of the remaining oil resource in the major oil reservoirs of the United States. The potential recovery can be even greater with a well designed, properly focused research, development, and demonstration (RD&D) program and technology transfer effort. However, if low oil prices persist and technology advancement is delayed, a significant portion of the remaining resource could be abandoned before the recovery potential can be realized.

This paper presents the results of a study by the Interstate Oil and Gas Compact Commission (IOGCC) to evaluate the impact of RD&D and technology transfer on future oil recovery in the United States. Major findings of the study include: (1) at the conclusion of conventional recovery operations, over 350 billion barrels will remain in known domestic oil reservoirs; (2) a significant portion (35% to 45%) of the remaining oil resource has already be abandoned, and an even greater portion is at risk of abandonment by the turn of the century; (3) wider application of currently available improved oil recovery technologies could stimulate as much as 7 to 9 billion barrels of incremental reserves in the $16/B to $20/B oil price range; (4) technology advances resulting from a focused RD&D program could stimulate an additional 5 to 8 billion barrels of incremental reserves for a total potential of 12 to 17 billion barrels at these oil prices; and (5) an aggressive and focused RD&D and technology transfer effort on improved recovery technologies needs to be undertaken in order to capitalize on the massive remaining oil resources in the U.S.
Applications and Results of Acrylamide-Polymer/Chromium (III) Carboxylate Gels
Authors: Southwell G. P. , Posey S. M.
Published: December 2007

Since the development of acrylamide-polymer/chromium(III)-carboxylate gels, a wide variety of field applications has demonstrated the utility and versatility of this system. Large volume injection well treatments for areal conformance, treatments for water/oil ratio reduction in producing wells, near wellbore treatments for effective squeeze treatments and the sealing of openhole wellbores as a completion tool will be reported.

The initial treatments were pumped in the Big Horn Basin of Wyoming and in the Permian Basin of western Texas. These large volume treatments pumped into injection wells have added approximately 5 MMBO in reserves at a cost of less than $1.0 per STBO, to naturally fractured waterflood reservoirs. With this success, a program was initiated using the same polymer gel system in high water/oil ratio producing wells with a strong water drive. Water/oil ratios have been reduced from 300:1 to as low as 30:1 in several Big Lake Field wells of western Texas. Another form of the polymer gel system is used for near wellbore total shut-off as a substitute process for conventional squeeze cementing. This technology has been applied to shut off gas or water when pumped into an isolated interval. The same technology is routinely applied to seal the openhole curved section of re-entries for horizontal wellbore completions in the Yates Field Unit of western Texas.
In-Depth Colloidal Dispersion Gels Improve Oil Recovery Efficiency
Authors: Mack J. C. , Smith J. E.
Published: December 2007

In the Rocky Mountain Region, a unique in-depth permeability modification process was applied to 29 field projects over the last 9 years. The process involves continuous, long term injection of environmentally sound colloidal dispersion gels. These gels provide a solution to in-depth channeling and crossflow problems inherent with waterflooding, which cannot be solved by near-wellbore gels. Use of colloidal dispersion gels in the field has never before been reported, yet the process has proven to have a phenomenal impact on efficiency of enhanced oil recovery projects. 22 of the projects were considered successful, resulting in improved oil recovery and reduced water production. Seven of the field projects were considered unsuccessful for a variety of reasons. Both successful and unsuccessful treatments are discussed, as both provide valuable insight into treatment design and application.

Ultimate oil recoveries in successful treatments are in excess of 40% OOIP, in highly heterogeneous matrix reservoirs with Dykstra-Parsons permeability variations on the order of 0.80. Chemical costs of $1.00 to $2.00/BBL incremental oil recovered are typical, and this cost has decreased below $1.00 in more recent floods due to improved technology. The colloidal dispersion gel process was applied successfully at bottom hole temperatures up to 202 °F. Oil viscosities are often high, from 10 cps to more than 20 cps at the reservoir bottom hole temperature. This paper provides a complete picture of project development from start to finish, including initial laboratory design, project selection criteria, field design, field implementation and project performance. The in-depth colloidal dispersion gel process is a versatile process that has proven an effective tool in long term enhanced oil recovery programs.
Pore-Scale Network Modelling of Waterflood Residual Oil Recovery by Immiscible Gas Flooding
Authors: Øren P-E. , Billiotte Joel , Pinczewski W. V.
Published: December 2007

The paper presents a precise description of the pore-scale displacement mechanisms responsible for the mobilization and subsequent recovery of waterflood residual oil by immiscible, gas flooding. The displacement mechanisms are incorporated into a numerical three-phase invasion percolation type network model which is used to compute oil recoveries by tertiary gas flooding for oil-water-gas systems displaying positive and negative spreading behaviour under strongly water wet conditions. Computed oil recoveries are shown to be in good agreement with those observed in micromodel displacement experiments. The network model confirms the. important role of oil spreading films in increasing recovery of water-flood residual oil for positive spreading systems.
What Determines Residual Oil Saturation in Three-Phase Flow?
Authors: Blunt M. J. , Fenwick D. H. , Zhou Dengen
Published: December 2007

We present a theoretical and experimental treatment of three phase flow in water wet porous media from the molecular level to the core scale. We compute the equilibrium thickness of a flat oil layer between water and gas considering both van der Waals and structural forces. We show that although most oils will spread over water, they will eventually form a film that is only a few molecules thick. The film thickness, which is in the range 0.1-5 nm, is determined by the capillary pressure and by whether or not the film was formed from thinning a thicker layer or by encroaching over a hitherto clean interface. Both spreading and non-spreading oils can form thin films. Drainage through this film would be far too slow to account for the recoveries seen experimentally. We then present results from drainage experiments in capillary tubes with a square cross-section. The tube has water wetting the corners and contains oil ganglia separated by air bubbles along its length. The gravitational driving force in the experiment allows oil ganglia to drain by swelling the oil film. We predict not only that eventually all the oil is recovered, but that we can calculate the drainage rate. The predicted rate agrees well with the measured values. Finally we perform a series of gravity drainage experiments in sand columns at high and low oil/water surface tensions. Air is introduced into the top of the column containing waterflood residual oil. At the end of the low surface tension experiment there is a thick oil layer (several microns across) between water and gas, stabilized by capillary forces, whereas for the high surface tension fluids, only a molecular oil film is present. In both cases oil is displaced by air, since the oil ganglia will drain under gravity by swelling the oil films. However, the low surface tension case gives a lower final recovery, since a significant amount of oil remains in the column in the thick oil layers. In both experiments virtually all the oil can drain from the top of the column.

The residual oil saturation in the presence of water and gas can be almost zero under favorable circumstances.
Influence of Connate Water on Oil Recovery by Gravity Drainage
Authors: Skauge Arne , Eleri O. O. , Graue Arne , Monstad Per
Published: December 2007

This paper summarizes results from gas gravity drainage experiments at different water saturations. The initial water saturation was varied from zero to very high water saturations where water starts to segregate during gravity drainage. The fluid distribution detected by in-situ saturation measurements along the core was compared to effluent production.

The results show that oil recovery by gas gravity drainage depends on the connate water saturation. A maximum in the oil recovery was observed at intermediate high water saturation. The total residual liquid phase (sum of oil and brine) increased at high initial water saturation.

The experimental results show that water-oil capillary forces influence the total liquid production by gravity drainage. The oil relative permeability increased with connate water present.
Surfactant Flooding: Technical and Economical Conditions to Succeed
Authors: Jakobsen S. R. , Hovland Frank
Published: December 2007

Surfactant flooding in four North Sea sandstone reservoirs have been studied by numerical simulations. The paper discusses the technical and the economical potential for surfactant flooding in these reservoirs, in addition to the uncertainty involved. The results indicates that optimum economy is achieved when typically less than 50 % of the surfactant flood technical potential is recovered.
Oil Recovery Improvement Through Profile Modification by Thermal Precipitation
Authors: Acock A. M. , Reis J. C.
Published: December 2007

This paper presents a method for lowering the permeability of thief zones in oil reservoirs to improve recovery during waterflood operations. The method consists of preheating the thief zone around the injection or production well by injecting hot water or steam and then injecting a hot, saturated chemical solution. If the chemical has a lower solubility at reservoir temperature than at injection temperature, cooling within the formation will result in the precipitation of solids in the pore spaces.

Several chemicals were identified as having a suitable temperature-dependent solubility with a low environmental toxicity, including potassium carbonate and sodium borate. The porosity and permeability reduction from temperature-dependent precipitation of these chemicals was then experimentally determined and a correlation between the permeability and porosity reduction was obtained. A theoretical analysis of this promising new process and how it can be applied are also presented.
Miscible Displacement in Fractured Porous Media: Part II—Analysis
Authors: Firoozabadi Abbas , Tan J. C. T.
Published: December 2007

Numerical simulation of miscible displacement experiments in fractured porous media was carried out to analyze the data. It was found that both the location and the magnitude of the fracture permeability heterogeneity were the main factors in determining the miscible displacement efficiency. The stripping of solute from matrix to fracture, which is caused by the permeability variation in the fracture, significantly increases the recovery efficiency. By taking the fracture permeability heterogeneity into account, the experiments were successfully simulated.
Determination of Injector Steam Quality and Flow-Rate From Orifice Data and Wellhead Pressure
Authors: Blacker H.F.
Published: December 2007

Obtaining accurate measurements of steam injection rate and quality for each injection well in a Thermal EOR flood is an essential part of effective flood management. This paper presents a technique which can be employed, without costly upgrades to field equipment, that provides a relatively accurate estimate of both steam injection rate and steam quality on a continuous basis.

A method of determining a well's injection characteristic is given. This response to injection is then used in conjunction with a conventional orifice flow calculation to provide an estimate of injection rate and quality that cannot be obtained from the orifice flow data alone. The theory and results of the initial field testing are presented in this paper.

Introduction

A series of field tests were run at the Midway Sunset Field with the objective of quantifying our ability to accurately determine an injection well's rate and quality from an orifice flow correlation (James Equation) and the change in wellhead pressure due to a change in mass flow rate and quality.
The Simulation of Paraffin Deposition and Removal in Wellbores
Authors: Keating J. F. , Wattenbarger R. A.
Published: December 2007

Paraffin deposition creates production problems and formation damage. To eliminate these problems, the deposited paraffin must be removed. Paraffin deposition and removal in reservoirs has been simulated by Ring and Wattenbarger1,2 and paraffin deposition due to natural cooling in reservoirs has been simulated by Peddibhotla.3 The objective of this work is to simulate paraffin deposition and removal in wellbores.

The paraffin simulator described in this paper models heat flow in the wellbore, reservoir, underburden, and overburden. This simulator also models mass flow in the wellbore and reservoir. This mass is composed of three pseudocomponents (gas, oil and paraffin) that can exist in three phases (vapor, liquid and solid). Some of this solid paraffin mass deposits onto the tubing during production. This natural phenomena was modeled with the following depositional mechanisms: (1) diffusion deposition and (2) shear deposition. Only one mechanism is used to model paraffin removal, the dissolving of solid paraffin.

Paraffin deposition results are presented for a single hypothetical well. These results indicate that only a fraction of the precipitated paraffin deposits onto the tubing. Paraffin removal results are presented for the following three thermal removal techniques: (1) hot oil injection, (2) downhole heaters, and (3) electric tubing heating. These results indicate that hot oil may cause formation damage if the paraffin concentration of the injected oil is high. These results also indicate that downhole heaters and electric heating of the are is a viable thermal removal techniques.
Uncertainty in Well Test Interpretation
Authors: Horne R. N.
Published: December 2007

Uncertainty is inherent in any nonlinear inverse problem. Well test interpretation suffers from a particularly unfortunate variety of uncertainties that combine to reduce the confidence that can be associated with the answers obtained. Nonetheless, well test data provide one of the few effective methods of direct reservoir analysis, and therefore it is important for petroleum engineers to overcome as much of the uncertainty as possible, and to understand that part which cannot be overcome. This paper will attempt to summarize the uncertainties found in well test analysis, will show examples of the difficulties, and will discuss methods that have been proposed to reduce or eliminate them.
Coal Gas Openhole Well Performance
Authors: Mavor M. J.
Published: December 2007

Gas production from coal seams has been highly successful due to the use of open-hole completion techniques in the high permeability fairway of the San Juan Basin (Colorado and New Mexico) Fruitland Formation. Based upon extensive formation evaluation data collected during Gas Research Institute funded research efforts, dynamic open-hole (cavity) completion production out-performed hydraulic fracture completion production regardless of the magnitude of natural fracture permeability due to lack of formation damage. This paper will illustrate four examples of the use of open-hole completion procedures that resulted in undamaged completions in reservoirs with absolute permeability ranging from 0.9 to 95 md. The formation evaluation data upon which the conclusions were based included open-hole logs, production logs, sonar logs, single well tests, and interference tests. The latest information has not been previously reported upon in the literature.
An Approach for Implementing Dual Porosity Models in Existing Simulators
Authors: Chen J. , Miller M.A. , Sepehrnoori K.
Published: December 2007

In dual porosity modeling of naturally fractured reservoirs, the reservoir is idealized as a set of disconnected matrix blocks within a highly conductive fracture network. It has been well recognized that the conventional dual porosity model does not accurately model matrix/fracture transfer flow. In the recent literature, matrix blocks have been further discretized to account for transient flow. Unfortunately, this approach greatly increases computational cost and requires much code modification if one tries to add a dual porosity option to an existing single porosity simulator.

In this paper, a new dual porosity modeling approach is presented for oil/water flow in fractured reservoirs. In the formulation, matrix blocks are also discretized. The resulting finite-difference equations for the matrix blocks, however, are mathematically decoupled from the fracture equations. The equations for the fracture system are the same as for single porosity models except for a source and/or sink term for each grid. This scheme does not affect the formulation of the original simulator, since the matrix computations are decoupled. This also greatly reduces computational and coding effort. Also, implicitness of the primary variables is maintained.

The model is verified by solution of Warren and Root's classical dual porosity model and an analytical solution which incorporates transient flow in matrix blocks. Results of the new model are also compared with fine-grid simulation of a fractured reservoir, in which both the fracture network and matrix blocks are discretized. Excellent agreement is achieved for a variety of reservoir properties. The simulator is also used to model published laboratory experiments and to conduct field-scale simulation studies. These results show that the new simulator provides computationally efficient and accurate means of modeling fractured reservoirs. The formulation developed can easily be extended to other recovery processes by modifying existing single porosity simulators.

Introduction

The most efficient approach to modeling fractured reservoirs appears to be the dual porosity model, proposed by Barenblatt et al. (1960) and introduced to the petroleum industry by Warren and Root (1963). The dual porosity model assumes that two equivalent continuous porous media are superimposed: one for the fracture system and another for the rock matrix. Continuity equations for each system are connected by so-called transfer functions that characterize flow between matrix blocks and fractures. Since Kazemi et al. (1976) introduced the first multiphase dual porosity model, almost all subsequent dual porosity models have been based on modifications of the transfer functions. These transfer functions are what distinguish various dual porosity models in the literature. Various transfer functions in the literature can be classified into three categories:the basic transfer function and its modifications,subgrid methods, anddiffusion methods.

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Core Damage Effects On Compaction Behaviour
Authors: Holt Rune M. , Brignoli Marco , Fjær Erling , Unander Tor Erling , Kenter Cor J.
Published: December 2007

Core damage caused by stress release is a source of potentially large errors in reservoir compaction predictions. Synthetic sandstone (with properties close to a certain reservoir rock) created under controlled stress conditions, can simulate the behaviour of both a virgin reservoir rock and a cored rock. The difference in behaviour is then an effect of coring. For low levels of depletion, uncorrected core measurements may lead to largely overestimated compaction in very weak sandstone. Core damage effects increase with stress and stress anisotropy. Field data supports the relation between core damage (seen through core recovery) and compaction behaviour.
Waterflooding of oil saturated Stevns outcrop chalk
Authors: Vanggaard Morten , Christensen Helle F.
Published: December 2007

Oil saturated specimens of Stevns outcrop chalk were tested in a standard Hoek cell. The test programme included uniaxial strain and waterflooding. The waterflooding test results lead to the conclusion that above the yield stress level the Stevns chalk compacts due to waterflooding. Strain gauges measurements in 3 levels on the specimen indicated that the waterflooding may be characterized as a plug flow and local compaction due to waterflooding was recorded. SEM studies showed no significant signs of cementation due to specimen preparation before testing.
Wellbore stability analysis in brittle rocks with continuous damage model
Authors: Shao J. F. , Khazraei R.
Published: December 2007

In this paper, the application of continuum damage mechanics to wellbore stability analysis is presented. In order to show the impact of the induced damage by microcracking process, three constitutive models are considered; an elastoplastic model, an isotropic damage model and an anisotropic damage model. All these models are calibrated from the same triaxial test on a sandstone. The application of the models to a plane strain borehole allows to clearly show impacts of different irreversible deformation mechanisms on predicted wellbore stability.
A Semi-Analytic Elastoplastic Model for Wellbore Stability with Applications to Sanding
Authors: Bradford I. D. R. , Cook J. M.
Published: December 2007

A semi-analytic elastoplastic model predicting the onset of failure in wellbores subjected to in-situ stress and pore pressure fields is presented. The model also has sanding applications. Rock elastic behaviour is modelled as being linear, with the plastic response described by a non-associated Mohr-Coulomb strain hardening deformation theory. The pore pressure gradient is taken into account using a source solution at the wellbore. Constitutive relations are calibrated using triaxial tests on Castlegate Sandstone cores. Hollow cylinder experiments, again performed with Castlegate sandstone, are used to evaluate predictions. Numerical examples illustrate how constitutive parameters influence the stress state around the wellbore and the onset of failure.
The Crack Tip Solution for Hydraulic Fracturing in Rock of Arbitrary Permeability
Authors: Lenoach B.
Published: December 2007

This paper extends previous work on analytical solutions for a KGD hydraulic fracture to include the effect of fluid loss. Our main new results are intermediate asymptotic solutions for arbitrary rock permeability; it is shown how these may be obtained in an asymptotic series whose leading term is the near-tip solution in the high permeability limit. In fact there is always a region immediately adjacent to the fluid front where the solution is dominated by fluid loss. The extent of this region depends on the fundamental parameter δ; our most important conclusion is that the solution may always be constructed as a series in δ which starts from the loss dominated limit.
Simulation and Field Analysis of Waterflood Induced Fracturing
Authors: Settari A. , Warren G. M.
Published: December 2007

The paper describes the theory of modelling waterflood induced fractures and the features which distinguish this process from conventional hydraulic fracturing. The mechanisms which are described in detail and illustrated by examples include 2-dimensional leak-off, the effect of previous injection, relative permeability and thermal effects, and pre-existing propped or acid fractures. All of these features have been found necessary for accurate matching of complex injection history of North Sea wells.
In-Situ Reservoir Compaction Monitoring in the Groningen Field
Authors: Mobach E. , Gussinklo H. J.
Published: December 2007

In-Situ reservoir compaction measurements have been performed in the Groningen field since 1974. The technique is based on regularly monitoring the distance between radio-active markers shot at regular distances across the reservoir. The application of this technique in the Groningen field is unique in the sense that it is normally used to monitor compaction in unconsolidated reservoirs, that compact much more than the Groningen reservoir. In practice, it has been proven difficult to obtain the required accuracy, 1 mm per 10 m. Until recently, the vertical rock compressibility could only be measured in three of the eight wells. The reservoir rock is so competent, that the target resolution is very close to the instrument resolution. Over the years, much effort has been put into improving the accuracy and reliability of the measurements, improvement on tools as well as on interpretation techniques. In 1993/1994, part of the surveys has been re-interpreted, using a new marker position algorithm, and a selection mechanism has been developed to identify statistically significantly deviating data. As a result, in all but one well could the vertical compressibility be obtained. The in-situ measured compressibilities match with the compressibility as inferred from the surface subsidence over the field.
Reservoir Microseismicity at the Ekofisk Oil Field
Authors: Rutledge James T. , Fairbanks Thomas D. , Albright James N. , Boade Rodney R. , Dangerfield John , Landa Geir H.
Published: December 2007

A triaxial, downhole geophone was deployed within the Ekofisk oil reservoir for monitoring ambient microseismicity as a test to determine if microearthquake signals generated from discrete shear failure of the reservoir rock could be detected. The results of the test were positive. During 104 hours of monitoring, 572 discrete events were recorded which have been identified as shear-failure microearthquakes. Reservoir microseismicity was detected at large distances (1000 m) from the monitor borehole and at rates (> 5 events per hour) which may allow practical characterization of the reservoir rock and overburden deformation induced by reservoir pressure changes.
Underground Storage of Hydrocarbons in Japan – Past and Present
Authors: Ogawa T. , Yamaguchi U. , Yamaguchi K.
Published: December 2007

Underground spaces are becoming more and more attractive as a new frontier, with the increase in public necessities such as rearrangements of infrastructures, conservation of natural environments, and preservation of landscapes in urban areas. They are also important for the storage of hydrocarbons, such as oil, LPG and LNG. This paper reviews the history and current situations of hydrocarbon storage in Japan, and the state of the art applied in design is highlighted.
Waste Disposal Monitoring Using the Surface Displacement Field
Authors: Rothenburg Leo , Dusseault Maurice B. , Bilak Roman A. , Bruno Michael S.
Published: December 2007

Massive injection of slurried solid waste generates permanent strains and displacements. These can be measured and analyzed to give useful information related to the shape and orientation of the injected body, and therefore lead to a monitoring approach based on accurate surface measurements of vertical movements or tilt. We discuss waste emplacement, present information showing the magnitudes of the final deformations, and show how some displacement field features are sensitive to certain parameters, whereas others are insensitive. Tilt measurements continuously through time give the best possibility of accurate monitoring of the waste body.
Sensitivity and Uncertainty Analysis Applied to Cavity Design Computations in Rock Salt
Authors: Wallner Manfred
Published: December 2007

Geotechnical safety for a cavity field will be assessed on the basis of model computations. The statistical uncertainty of rock salt parameters as well as possible variations in the dimensions of a cavity field under design result in the necessity to carry out a parametric study. The purpose of the paper is to explain probabilistic modeling with respect to structural response computations, using sensitivity and uncertainty analysis. Probabilistic finite element computations have been carried out for a hexagonal cavity configuration. The results are discussed with respect to the variability of the following parameters and their interrelation: diameter, spacing, depth and height of the cavities, creep of the salt rock, and stiffness of the overburden.