bluuebunny/crossref_metadata_2025 huggingface dataset:
Static and Dynamic Rock Mechanical Properties in the Hugoton and Panoma Fields, Kansas
Authors: Yale D. P. , Jamieson W. H.
Published: December 2007

An understanding of the mechanical properties of petroleum reservoirs is important for drilling, well stimulation and horizontal well development. Static and dynamic rock mechanical properties were measured on a suite of core samples taken through the Chase and Council Grove carbonate sequences of the Hugoton and Panoma fields, Kansas. The purpose of the study was to characterize the mechanical properties of the different facies and calibrate the dynamic mechanical properties so acoustic well logs from other wells can be utilized more effectively in determining areal and lithologic variation in mechanical properties of the field.

The mechanical properties of rocks can be measured in the laboratory from triaxial tests ("static" tests) or they can be estimated from wireline measurements of compressional and shear acoustic velocities and rock density ("dynamic" tests). Static measurements on cores are much more indicative of the mechanical properties of the reservoir than the dynamic results, however, the information from acoustic well logs covers much more of the reservoir than core measurements and is less expensive. Since there can be significant differences between static and dynamic values, it important to be able to translate the "dynamically" derived mechanical properties to the static values which better represent the reservoir.

Results of the tests show that Young's modulus correlates strongly with lithofacies and porosity. The Chase and Council Grove carbonate sequences can be separated into six "mechanical facies", defined by their modulus-porosity trends and their lithology. Only small percentages of secondary minerals (dolomite and anhydrite) appear necessary to alter the rocks properties significantly. Poisson's ratio is less sensitive to lithology but correlates with porosity. The dynamic Young's moduli are higher than the static values but dynamic and static Poisson's ratios correlate well with each other for liquid saturated samples.

Dynamic to static transforms based on lithofacies were developed from these data to correct the acoustic log derived mechanical properties to static values appropriate for reservoir deformations. The corrected mechanical properties along with the trends observed between mechanical properties, lithofacies, and porosity allow for the design of more effective hydraulic fracture treatments by utilizing accurate values for the reservoir's mechanical properties and their variability.
Development and Testing of a Semi-Analytical Hydraulic Fracture Model for Multistress Media
Authors: Rueda J. I. , Rahim Zillur , Holditch S. A.
Published: December 2007

Over the past 25 years, numerous hydraulic fracture models have been developed to predict the behavior of underground fracture propagation.1 Typical fracture propagation models predict fracture height, length, and width based on formation mechanical and fracture fluid properties.2 Fracturing fluids and effects of leakoff also have great influence on ultimate fracture dimensions. A recent paper by Warpinski et al.3 illustrates the diversity that still exists in the fracture propagation modeling problem.

There are basically two types of three-dimensional fracture models. Pseudo-three-dimensional models, that run efficiently on microcomputers, are mostly applicable in reservoirs bounded by high in-situ stress layers that can suppress rapid fracture height growth. Full three-dimensional models, on the other hand, require more computer memory, run time, and user expertise to design and evaluate a fracture treatment. Reducing CPU time is important, particularly during a fracture design optimization process, since numerous fracture predictions and sensitivity analyses are needed to determine the optimal fracture design.

In this paper, we will illustrate how to couple the equations describing formation elasticity, fracture fluid flow, and fracture mechanics and develop an efficient semi-analytical technique to determine fracture geometry. We have assumed a quadratic pressure and stress profile fit to approximate the fluid pressure inside the fracture and the in-situ stress profile in a multilayered system. We have tested our new model using different reservoir conditions. We provide a detailed sensitivity analysis on reservoir and fluid parameters in order to help us understand how these parameters influence the design of a hydraulic fracture treatment.
Slug Flow: Occurrence, Consequences, and Prediction
Authors: Hill T. J. , Wood D. G.
Published: December 2007

BP Exploration currently has an interest in hundreds of kilometres of operating multiphase flowlines. Most of the company's proposed field developments also involve multiphase flowlines. A large number of these do or will experience slug flow, either as the normal flow regime, or as a result of transient behaviour.

Data on flow regime and slug flow characteristics have been collected from many lines over the past 8 years. Information on slug characteristics from a number of different systems is presented in this paper, including velocity, length and holdup. Some unfavourable consequences of slug flow on both process performance and system integrity are highlighted, including plant shutdowns and mechanical damage.

The need to be able to predict slug flow for the design of future systems, and to advise the operators of existing systems, remains a high priority for R&D activities, as ever longer and more complex multiphase systems are proposed. BP's latest slug frequency method is described, followed by guidelines for pipework layout, and comments on current R&D on corrosion in multiphase flow.
The Interactive Visualization of Spatial Uncertainty
Authors: Srivastava R. M.
Published: December 2007

Though stochastic and geostatistical methods can produce numerous equally likely models of a petroleum reservoir, most practical case studies that use such probabilistic methods do not explore the entire space of uncertainty but focus instead on a single outcome. When displayed using powerful visualization tools, this single outcome is often mistaken for reality. The traditional graphical displays that geostatisticians use to combat this false belief in the certainty of a single image do not convey uncertainty in an intuitive manner; these traditional displays therefore tend to be less compelling than the slick and polished graphical displays that modern visualization tools provide.

The visualization of spatial uncertainty can be made more intuitive with dynamic displays in which each frame is a plausible outcome that differs only slightly from the previous one. The same approach can be enhanced to allow interaction with the display so that users have a more direct sense of exploring the space of uncertainty.

Interactive visualization tools improve decision-making in the face of uncertainty by confronting engineers and geologists with the spatial uncertainy that is often critical in a comprehensive risk analysis of EOR projects.
Stress Analysis of Drillstrings
Authors: Paslay P. R.
Published: December 2007

Drillstring stress analysis techniques are reviewed with emphasis on the use of torque-drag formulations. Some of the many modifications to torque-drag calculations are reviewed and discussed. The limitations of current results in drillstring dynamics for use in stress analysis calculations are also discussed.
Interpretation of Hydraulic Fracture Mapping Experiments
Authors: Warpinski N. R.
Published: December 2007

Simple mechanical models of the response of a reservoir to hydraulic fracturing have been developed in order to interpret the response of microseismic and downhole-tilmeter diagnostic systems and determine the important reservoir and treatment parameters that influence the response. For microseisms, results of this study can be used to delineate the width of the seismically active zone and possibly distinguish different types of signals. For downhole tiltmeters, the results can be used to interpret the measured tilt response and provide information on height growth, closure pressure and proppant placement.
Acoustic tomographic difference imaging of dynamic stress fields
Authors: Scott T. E. , Ma Q. , Roegiers J. -C. , Reches Z.
Published: December 2007

Acoustic tomographic imaging was conducted on a complex stress field generated during indentation into a Berea sandstone core sample. The imaging process used 130 ultrasonic raypaths and 97 pixel elements to construct tomograms perpendicular to the indentation direction. ‘Zeroed velocity’ acoustic difference tomograms were made by subtracting the initial velocity tomogram from the seven successive indentation tomograms up to stresses of 110 MPa. The tomograms illustrate a marked development of a high velocity zone beneath the indenter. The high velocity maximum continues to increase with increasing application of indentation stress. At the highest indentation stress levels the rate of change in velocities with added deformation is lower than at low stress levels. This observation is attributed to the closure of cracks and pore spaces at high stress levels. These results indicate that it may be possible to image changes in stress fields created during petroleum extraction and production operations.
Results from reservoir depressurisation simulation incorporating phenomena revealed in a reactive reservoir analogue
Authors: Smart B. G. D. , Tehrani D. H. , Olden P. W. H. , Jin M.
Published: December 2007

Field observations of rock mechanical phenomena made in reactive analogues are presented, along with the output from coupled simulation models of reservoirs incorporating these phenomena. The models demonstrate that fault activation occurs during depressurisation, altering conductivities and hence controlling the flow of fluids towards the producing wells.

Als reaktive Analoge gemachte Feldbeobachtungen gesteinsmechanischer Phänomene werden zusammen mit dem Output aus gekoppelten Simulationsmodellen von Speichern, die diese Phänomene aufweisen, vorgestellt. Die Modelle demonstrieren das Auftreten von Fehleraktivierung und Scherung der Ablagerungsebene während einer Druckminderung, wodurch Leitfähigkeiten und damit auch die Kontrolle des Flusses von Flüssigkeiten zum Produktionsbohrloch geändert werden.

Les phénomenes rocheux mécaniques observés sur le terrain dans des systemes analogiques réactifs sont présentés accompagnés des sorties obtenues de modeles couplés de simulation de reservoirs présentant ces phénoménes. Les modéles démontrent que 1'activation de faille et le cisaillement de plan de stratification se produisent å la dépressurisation donnat des modifications de conductivité affectant 1' écoulement des fluides vers le puits de production.
Fluid-Saturated Solid Flow with Propagation of a Yielding Front
Authors: Geilikman M. B. , Dusseault M. B. , Dullien F. A. L.
Published: December 2007

Sand production instability is considered as the result of wellbore fluid pressure reduction (drawdown) below some critical level. A continuum model for massive continued sand production is developed by considering coupling of fluid flow with the flow of the granular matrix. The model provides a physical mechanism describing propagation of a yielding front away from the wellbore as sand production continues. Solid flow proceeds by "unravelling of fabric" because yield front motion is opposite to the direction of solids mass transport. Short-term enhancement of fluid production because of simultaneous sand production turns out to be dependent not only on instantaneous sand flux, but also on the current radius of the yielded zone around wellbore, that is, the history of sand production for the well. Long-term enhancement is stipulated mainly by growth of a yielded, highly permeable zone around the wellbore.
Effect of the Fracture Process Zone in Directed Crack Propagation in Borehole Blasting
Authors: Exadaktylos George , Agioutantis Zacharias , Lambrou Eleftherios
Published: December 2007

The growth of directed radial cracks originating from diametrically opposite notches in a blasthole, is analyzed. The cracks are considered to be composed from a traction free portion and a microcracking zone where cohesive forces act. A preliminary energy balance approach showed that the length of this zone has an effect on the blast results. Subsequently, a coupled non-linear displacement discontinuity model was applied in order to verify this effect.
Geomechanical Analysis of Small Earthquakes at the Eleveld Gas Reservoir
Authors: Roest J. P. A. , Kuilman W.
Published: December 2007

A distinct relationship exists between the production of natural gas and small earthquakes near the reservoir. Simple models show that the sensitivity for fault activation due to differential compaction evidently depends on the fault-reservoir geometry. A very sensitive geometry, leading to several small earthquakes, is found in the Eleveld gasfield. The observed magnitudes correlate well with estimates from a more complex model. In this specific geological setting residual tectonic stresses are assumed to be negligible. For the coming decades, pressure depletion is expected to amount to only a fraction of the pressure depletion up to now. Therefore the potential magnitudes of possible future earthquakes in this area are expected to become only marginally higher.
Temporal and Spatial Structures of Triggered Seismicity in Romashkinskoye Oil-Field
Authors: Turuntaev S. B.
Published: December 2007

The analysis of spatial-temporal organization of seismicity on the Romashkinskoye oil field (Tatarstan, Russia) was made. The object of analysis was the catalog of about 360 seismic events (0.1<M<4) being registered since 1986. It was found that the slope of magnitude-frequency relationship ship was the same as it is usual for induced seismicity. The analysis of temporal behavior of seismic regime was made in terms of two variables, they are "the activity of seismic process" and "the velocity of activity change". It was shown that the studied seismic process can be consider as Markov chain rather than Poisson' process. Abnormally great number of shocks close in time to each other is observed. The analysis of spatial distribution of such events was made. Correlation between seismic activity and extraction of fluids, injection of water and difference in volume between them was investigated.
The Mechanisms of Seismic Events Around Faults in Mines
Authors: van Aswegen Gerrie , Meijer Olaf
Published: December 2007

Quantitative seismological analysis yields source parameters relating to stress and strain in the source region. Parameters such as seismic viscosity help to distinguish between rock volumes of different strain behaviour. Recorded seismic strain scales aseismic strain (specifically fault creep). Applications of these concepts to the characterisation of fault behaviour are presented, with specific reference to lower order moment tensor analyses. In the mining environment a unique opportunity exists to verify moment tensor analyses by physical inspection of the sources of seismic events. One application of quantitative seismic monitoring could be for the evaluation of the effect of reservoir depletion on faults with earthquake potential.
Capillary Phenomena in an Impure Chalk
Authors: Brignoli M. , Santarelli F. J. , Righetti C.
Published: December 2007

The effects of capillary forces on the constitutive behaviour of reservoir rocks are an item which has been poorly investigated but which could have potential important consequences from an operational point of view especially when considering the behaviour of reservoir rocks with very small pores such as chalks and shaley sandstones. Laboratory investigations have been carried out on an impure chalk in order to determine its mechanical properties and constitutive behaviour under different environment conditions; the variations of the moduli resulting from a set of experiments performed at different temperatures and pressures may be qualitatively interpreted in terms of capillary pressure variations. In the same way, uniaxial compressive strength of some sedimentary rocks seems to be affected by capillary effects: a qualitative interpretation is given and a simple model able to predict variations in strength with respect to saturation has been verified with good agreement between experimental and predicted data.
In-situ Stress Field Determination and Formation Characterization – Offshore Qatar Case History
Authors: Brumley John , Kuhlman Robert , Abass Hazim , Christiansen Claus , Jorgenson Lars Nydahl
Published: December 2007

This paper presents a comparison of several methods that can be used to obtain in-situ stress field data in an oil/gas well. In an offshore well recently drilled in the Arabian Gulf, the following techniques were used to acquire data used in the design of hydraulic fracture treatments for the well:Microfrac pressure analysis yielded information about the magnitude of the minimum principal stress.A borehole extensometer used during the microfrac testing gave additional information: the in-situ shear modulus, the orientation of the principal stress axes, the actual orientation of the created fracture, and the width of the fracture.Anelastic strain recovery (ASR) was employed as a secondary method to determine the orientation of principal stress axes.Oriented coring after microfrac testing was used to recover a portion of the actual microfrac and determine the orientation.A borehole scanning record was used to determine the orientation of natural fractures.A multi-arm caliper log was used for wellbore ellipticity evaluation, while borehole breakout was used as an indicator for the orientation of principal stress axes.

The results obtained are compared and discussed based on general knowledge of the regional stress field variations as obtained from geological surveys. In addition, rock properties obtained from core sample tests and from processing of an acoustic wireline record were compared with the data calculated from the wellbore extensometer. A comparison of the various methods for determining the magnitude and orientation of the in-situ stress field demonstrate the relative reliability, for this case, of the individual methods. This paper demonstrates the necessity of using several methods to obtain reliable in-situ stress data.
Issues in the Estimation and Application of Discount Rates for Investment Evaluation
Authors: Allison J. C.
Published: December 2007

The management of any petroleum company is charged with allocating resources among potential investment opportunities. Determination of the appropriate discount rate is a critical element in the analysis of these opportunities using discounted cash flow techniques. The appropriate discount rate is affected by a number of factors, some a matter of macroeconomic conditions (e.g., inflation and interest rates), some a matter of company policy (capital structure), and some specific to the particular project. This paper discusses (1) the general methodology for estimating company-average discount rates, reflecting both macroeconomic factors and company policy choices, and (2) the circumstances under which the company-average rate is likely to be significantly inappropriate and the adjustments that can be made under those circumstances.
Entering the U.K. Upstream Gas Business: A Generator's View
Authors: Morgan J. R.
Published: December 2007

In the early 1990's, the removal of restrictions on the use of gas for power generation and the privatisation of the UK electricity supply industry prompted the rapid introduction of gas as a fuel of choice for new power plant. Much of this gas has been purchased under long term contracts with the owners of offshore gas fields or from British Gas plc. More recently the two major power generators have entered the upstream gas business directly.

This paper reviews entry strategies to the upstream gas business seen from the perspective of a power generator – PowerGen plc. It begins by examining the company's rationale for moving from contracting for gas supplies to direct ownership of gas, and outlines the objectives set for entry. Alternative entry strategies are compared and contrasted, and the distinctive features of the chosen strategy are reviewed. Finally some of the key events in implementing the chosen strategy are described culminating in two recent acquisitions.

Background – Rationale for Diversification

PowerGen is set to become the largest user of gas in the UK. From 1996 it will have in operation some 3000 Mwe of CCGT plant, fuelled entirely by gas contracted directly with offshore producers and equivalent to more than 10% of all UK daily gas supplies. Even without further CCGT plant, these supplies will have to be replaced as the initial contracts decline. In addition, PowerGen is developing new businesses in gas transportation and marketing (Kinetica Limited – a joint venture with Conoco (UK) Limited); in combined heat and power (through PowerGen GHP Limited); and in international power generation (through PowerGen International).

These businesses are likely to increase substantially the company's long run demand for gas. Whilst some of this need will continue to be met from contracted gas, there is a clear rationale for extending PowerGen's capability to direct ownership of gas: To support the core and core-related new businesses by securing gas at lower cost than direct purchase.To benefit the company's position as a purchaser by improving its understanding of contract terms and producer costs and increasing its contractual flexibility.To support the other gas consuming and trading businesses so as to add value to the core business.To allow smoothing of earnings by "hedging" gas generation earnings with gas production earnings.

A key reason for pursuing this limited diversification to upstream gas is to create a source of good quality earnings from a closely related business, during a period when the core business is likely to come under increasing competitive and regulatory pressure.
Planning for Information Technology in Exploration and Production
Authors: Hunter L. R.
Published: December 2007

This paper will provide corporate wide investment in Information Technology (IT) that is more consistent with the goals of the business and will help ensure there is an appropriate return on the expenditure. It will be of most interest to those in an oil and gas company with several departments or functions that are sharing resources and information.

This paper is not a comprehensive description of the planning process but highlights the efforts needed to align the business and technology drivers. Most articles on computer related technology in the upstream petroleum industry describe isolated technical applications without reference to any impact on the broader computing and operating environment. This paper will build on those efforts by setting a framework for planning and investment that integrates total IT requirements with the needs of the business. It explains how the application of vision, integrated planning and portfolio evaluation can encourage a better analysis thereby ensuring more appropriate investment.

Table 1 highlights the main topics in this paper. It also outlines the prime checkpoints for the information planning process.
General Access Well Information Database
Authors: Bourgoyne A. T. , Sinha V. K. , Rocha L. A.
Published: December 2007

The large amount of data collected during drilling wells is important in the design of the future nearby wells. These data include information such as fracture gradient (leak-off test and integrity test), formation density, pore pressure, lithology etc. Lack of this information may lead to a bad well design. The availability of these data can play an important role in reducing the risk of severe accidents such as blowouts.

Generally data for explored wells is available in each company's information storage system in some format decided by that company. Some of these data are not highly proprietary and could be shared. Well design could be significantly improved if pore pressure and fracture gradient data were readily available for all wells drilled in an area rather than data from just the wells drilled by the company planning the new well. Presently this information is not shared because of the following: The data in the company is often not centrally organized, especially for drilling engineering purposes.There is a lack of a centralized communication channel.A large effort is required to collect the information from various companies and put them into one format.

A central public database would minimize the above problems. If such a database containing important well information were readily accessible to the companies, it would be of great benefit to them.

This paper describes a prototype database containing limited information about wells explored by companies in different areas. The database is developed on IBM RS/6000 platform and is publicly available in a test mode. Users can interact with the database by connecting to the internet node of Petroleum Engineering Department of Louisiana State University or by connecting to the machine by telephone modem. The results of the queries can be downloaded onto user's machines.
Computer Based Training System for the Diagnosis of Failure in Flow Stations
Authors: Villalobos Adriana , Rosales Orlando , Granadillo Amir
Published: December 2007

Flow stations have the specific function of receiving, separating, temporarily storing and pumping the fluids coming from the nearby wells. It is the key element of oil production because the productivity of the wells depend on the correct operation of the flow station. When an automatic shutdown occurs, the automatic income valves of crude at the separators close. As a consequence, the oil production stays trapped in the general production manifold. The time the station stays closed represents the deferred oil production of the station.

When a shutdown occurs, the first step to be taken is to make a diagnosis of the problem to determine the cause. It should be emphasized that the operation requires highly trained staff who are well aware of the importance of making a rapid diagnosis so the stations remains closed only for a short time.

To increase the quality of the processes, the oil industry has automated the management and processing of information. To accomplish this objective, the Training Center of Petróleos de Venezuela (CEPET) had to design training systems based on the computer to improve the training quality of the staff. These new training systems are directed at diagnosing failures that cause automatic shutdowns in a flow station. This is done because there are no specific instructions for operators, intrumentalists and foremen in this particular area. This training system is to supplement the normal training received in the field.
An Architecture for Decision Support: Integration Across Multiple Independent Databases and Applications
Authors: Larson B. M. , Moorhouse John , Balcom M. L.
Published: December 2007

ABSTRACT*

As most companies move to improve the effectiveness of their information systems, one of the most important goals is to ensure that corporate data is easy to access, monitor, and share. In trying to achieve this goal, petroleum companies face the challenge of managing data stored across numerous, disparate databases and accessed by independent applications.

Pembina is pursuing an integration strategy to achieve greater efficiency in their management of corporate data. One project involves the retrieval of well and production information from the data source and the update of corporate reserves and land applications. Merak Projects, an engineering software vendor, and Digitech Information Services, a data vendor, are working with Pembina to automate this process. Merak's Helios program integrates diverse information systems and databases across multi-platform configurations, thereby improving data consistency and accessibility.

This is Pembina's first step towards an automated, corporate wide information system which will span a variety of applications residing on UNIX and PC systems on Novell networks. Access to the most recent and reliable data will improve the quality of decisions and assist Pembina in maintaining a competitive advantage.
Critical Technologies for Success in Extended Reach Drilling
Authors: Payne M. L. , Cocking D. A. , Hatch A. J.
Published: December 2007

This paper overviews critical technologies for extended-reach drilling (ERD). ERD is a pivotal industry activity because it enables optimisation of field development through the reduction of drilling sites and structures and provides access to otherwise unavailable reserves. These efficiencies increase profit margins on viable projects and can make marginal prospects financially viable.

ERD technologies to be reviewed include torque/drag, drillstring design, wellbore stability, hole cleaning, casing considerations, directional drilling optimisation, drilling dynamics, and rig sizing. These technologies have been found critical to the success of ERD.

The paper is based on experience gained in the pursuit of world record ERD objectives in BP Exploration’s Wytch Farm oilfield, and as a result combines current technology assessments with practical field knowledge.
Extending Barriers to Develop a Marginal Satellite Field from an Existing Platform
Authors: Justad T. , Jacobsen B. , Blikra H. , Gaskin G. , Clarke C. , Ritchie A.
Published: December 2007

Changing geological requirements during the development of a satellite field from the main Gullfaks platforms, resulted in the drilling of a "complex, mega reach, designer horizontal well". The original well plan, to reach a horizontal displacement of 4000m (13,123ft.) at a vertical depth of 2020m (6,627ft.), underwent significant modification as accumulating geological data was used to re-map the field. - Figure 6.

We will demonstrate how pre-engineering studies, computer modelling and real time data recording allowed successful completion of the project and removed many of the perceived barriers to the development of out-lying structures.
The Application of Petrophysical Data to Improve Pore and Fracture Pressure Determination in North Sea Central Graben HPHT Wells
Authors: Ward C. D. , Coghill K. , Broussard M. D.
Published: December 2007

Pore and fracture pressure determinations are key considerations for the successful planning and drilling of North Sea Central Graben High Pressure High Temperature (HPHT) wells. Knowledge of these downhole pressure constraints can have a significant impact on drilling safety and economics. In this paper we present recent advancements to a previously presented methodology. Pore and fracture pressure is determined using wireline or MWD petrophysical data and an effective stress approach. The results have increased our understanding of overpressure generation mechanisms and hydrocarbon migration in this basin.

Most traditional pore pressure estimation methods use a shale disequilibrium compaction model for their calculations. We assess these methods and propose that excellent results can be obtained by deriving porosity from density or deep resistivity data. This porosity, together with a lithology estimation from the gamma ray, are input into an Effective Stress Loading limb (ESL) model that calculates pore and fracture pressures through all major lithologies.

Along the North Sea Central Graben axis there are two distinct pressure domains. These are separated by a low porosity (<5%) horizontal pressure seal within the Cretaceous Chalk Group. This seal occurs between ~3.5-4km and is independent of stratigraphic level within the chalk. Above ~3.5km, rapidly deposited Tertiary shales and Upper Cretaceous chalks are on the compactional loading limb. Here, moderate overpressures are generated by disequilibrium compaction. Below ~4km, low porosity (5-10%) Mesozoic sediments are unloaded by fluid expansion mechanisms to produce extreme overpressures.

The upper limit for the pore pressure is the fracture propagation pressure. When this is exceeded, hydraulic fracturing can occur and the fluids escape, allowing the fracture to close and pressure to build again. In this environment, primary hydrocarbon migration may be largely dependent on the rate of the hydraulic fracturing formed as a consequence of the extreme fluid pressures generated by fluid expansion.

An understanding of these pressure generating mechanisms, together with improved porosity determinations, has led to more accurate pore and fracture pressure determinations. Implementing the results into well planning and drilling can help avoid many of the costly pressure related problems inherent to HPHT wells.
Quantifying Stuck Pipe Risk in Gulf of Mexico Oil and Gas Drilling
Authors: Wisnie A. P. , Zhu Zhiwei
Published: December 2007

Stuck drillpipe is one of the most costly risks of exploitation drilling. However, few, if any companies incorporate this risk into their project evaluation economics. This paper describes a method to quantify such risks. The method involves gathering data from over 311 cases drilled in the Gulf of Mexico. From this data. Logistic Regression was used to build stuck pipe probability models for both water-based and oil-based drilling mud. These models, which measure both the probability of getting stuck and freeing the drillpipe once it becomes stuck, are incorporated into a Monte Carlo simulation, which yields a log-normal distribution of costs for a hole section of a given design. This distribution of costs can be incorporated with exploration risk methods for a project evaluation technique that incorporates cost (mechanical) risks as well as revenue (exploration) risks.
Implementing Residual Bend in a Tubing Forces Model
Authors: Bhalla Kenneth
Published: December 2007

Coiled Tubing (CT) is being used increasingly to service highly deviated wells. Among the mechanical problems encountered in running coiled tubing into a highly deviated well is helical buckling of the tubing which leads to lockup. Furthermore, contact between the CT and casing can restrict the weight that can be applied to a downhole tool, thereby limiting the placement of tools in deviated sections.

A tubing forces model has been developed that calculates the resulting stresses and deformation of the coiled tubing as the coiled tubing is run into and pulled out of the well, the points at which helical buckling occurs and an indication of whether lockup has occurred.

An inconsistency in current tubing forces models is that they utilize two differing coefficients of friction for running in hole and pulling out of hole. This criterion suggests some technical deficiency in the formulation of the models. Results from the tubing forces model presented in this paper account for the residual bend due to coiled tubing being wound on the reel and gooseneck. A consequence of this is that it is unnecessary to use two differing friction coefficients for running in hole and pulling out of hole.

Results are presented in the form of the surface weight indicator and compared to field data. It is observed that the surface weight indicator predictions are in good agreement with field data.

This work suggests that accounting for residual bend, the tubing forces model accurately provides the state of stress, operating forces and deformations during coiled tubing placement. This allows for accurate job design prior to running the tubing in the hole at the well site.
Different Shales Dictate Fundamentally Different Strategies in Hydraulics, Bit Selection, and Operating Practices
Authors: Pessier R. C. , Fear M. J. , Wells M. R.
Published: December 2007

Full-scale simulator tests under hydrostatic pressure in Wellington, Catoosa and Mancos shales reveal fundamental differences in balling characteristics and drillability. These differences call for distinctly different strategies in hydraulics, bit selection and the optimization of mechanical drilling parameters.

This paper presents test data and photographs to illustrate the unique behavior of these three shales, which differ widely in composition and mechanical properties.
A CPI Process Review of the AFE Decision-Making Process
Authors: Pieters D. A.
Published: December 2007

Idea generation, engineering and approval are all necessary parts of the decision making process in all oil and gas companies. These individual steps however, can be combined into a single high-level process referred to as the AFE process. AFE (Authorization For Expenditure) terminology has become widely used in the oil industry environment. The process combines financial capital with engineering talent to produce enhanced output in the form of successfully drilled wells. The AFE decision making process starts with an idea or concept and concludes with the finished product of a drilled well. A direct comparison can be made between the new product development process in a manufacturing company with this process. Similarly, improving the AFE process is as critical as bringing new, innovative products to the market in as short a time as possible.

This paper flow-charts the decision making process from the idea inception to the final drilled well as it is currently performed within a company. Each step is examined in detail and a total cycle-time is calculated. A continuous performance improvement (CPI) style process review is carried out to remove bottle-necks and redundant steps in order to reduce cycle-time and improve the process flow. The new process becomes significantly improved over the old one. Cycle-time is reduced by performing various steps in a parallel rather than series mode. Decision making is employed at a team level where the entire team becomes responsible for the process rather than the individual. Ultimately, consensus and buy-in is reached at a quicker pace. A project kick-off checklist is designed to facilitate complete and thorough review at the start and at specific milestones as the project progresses. Suggestions are outlined for increasing idea generation, deciding on data needs and on when service-company partnering should be considered. In addition, methodologies for establishing project quality control checks, lookbacks and for reviewing each project for technical soundness are investigated.
Reform and Privatization in the Hydrocarbon Sector
Authors: Khelil Chakib
Published: December 2007

Like in many other developing countries, Argentina, Bolivia and Peru formed state oil and gas companies to exploit their hydrocarbon resources. The government policy considered these resources part of the national patrimony and of great strategic importance in providing energy self sufficiency and fueling the country’s planned industrialization. Among other things, this policy provided a monopoly to state companies over many activities in the hydrocarbon sector, limited investments by private oil companies, restricted oil and petroleum products exports and imports and regulated crude oil and petroleum products prices and distribution margins. This policy had negative impacts on the state resources and debt. This paper presents the major transformations and privatization in the hydrocarbon sector that were recently achieved by Argentina and the outlook for Bolivia and Peru carrying out similar transformations. New hydrocarbon laws have been issued which did away with the state monopoly in the sector, provided major incentives for private investments and cleared the way for an open and competitive crude oil, natural gas and petroleum products markets. The passage of these laws paved the way for the privatization of state oil and gas companies Yacimientos Petroliferos Fiscales (YPF) and Gas del Estado (GdE) of Argentina. Soon Petroperu and YPF of Bolivia (YPFB) will be under the control of private investors. Argentina, Bolivia and Peru’s economies are showing revitalized growth and renewed interest by oil sector investors.
An Area of Review Variance Methodology
Authors: Warner D. L. , Koederitz L. F. , Dunn-Norman Shari , Laudon R. C.
Published: December 2007

When the Underground Injection Control (UIC) Regulations were promulgated in 1980, by the U.S. EPA, existing Class II (oilfield) injection wells operating at the time that the regulations became effective were excluded from Area of Review (AOR) requirements. EPA has expressed its intent to revise the regulations to include the requirement for AORs for such wells.

A Federal Adivisory Committee (FAC) has recommended that AORs for existing wells, not previously subject to that requirement, be performed within five years of promulgation of amended UIC regulations. The FAC has, however, recognized that conditions can exist that make it unnecessary to perform well-by-well AORs and that can allow wells in a basin, producing trend, region or field or a portion of such areas to be exempted from an AOR through a variance program.

A methodology for identifying areas that would be eligible for variance from AOR requirements has been developed. The methodology provides for evaluation of an area for variance based upon five criteria. These criteria could be used in any order, singly or in combination, to exclude some or all wells from the AOR process. Wells not excluded by variance would be subject to well-by-well AORs.
Seismic-Guided Estimation of Reservoir Properties
Authors: Schultz P. S. , Ronen Shuki , Hattori Masami , Mantran Pascal , Hoskins Josiah , Corbett Chip
Published: December 2007

When 3D seismic data and logs from multiple wells are available, maps of rock or reservoir properties for reservoir characterization can be improved in both detail and accuracy by using seismic attributes (mathematical transformations on the data) with log data in a statistical analysis, guided by principles of rock physics. A controlled study in a field with 3D seismic and 15 logged wells demonstrated both improved detail and improved accuracy in maps of effective porosity and water saturation.
Pressure Transient Testing of Horizontal Wells With an Overlying Gas Cap
Authors: Fleming C. H. , Perschke D. R. , Gilman J. R. , Kazemi Hossein
Published: December 2007

This paper investigates pressure transient testing of horizontal drainholes in an oil reservoir with a large overlying gas cap. The study was prompted by the observation that many of the buildup tests obtained on horizontal drainholes exhibited large oscillations of the pressure derivative.

Results presented in this paper are based on both field data and numerical simulation. The main purpose was to determine the cause of the pressure derivative oscillations and to explore whether conventional analysis of buildup tests could yield reliable estimates of permeability and skin factor under existing field conditions.
Design and History Matching of a Very Large Waterflood/Miscible Gas Flood Model of the Northwest Fault Block, Prudhoe Bay, Alaska
Authors: Weiler Bruce E. , Saidikowski Ronald M. , Breit Vernon S.
Published: December 2007

Prudhoe Bay, located on Alaska’s North Slope, is the largest field discovered in North America. Over eight billion barrels of oil have been produced since the start of production in 1977. Four major waterflood/miscible water-alternating-gas (WAG) flood projects are in progress in the Prudhoe Bay field. This paper describes the construction of a model representing one of these projects using a combination of stochastic and deterministic tools, and input data from the major field owners (ARCO, BP and Exxon) by personnel from multiple companies. These techniques produced porosities and permeabilities that required only minor modifications to obtain an excellent history match for the Northwest Fault Block (NWFB) area of the Prudhoe Bay field.

The historical production period matched in this study included primary, secondary waterflood and tertiary miscible WAG flood mechanisms. During the history matching process, proper representation of the well’s perforation and wellwork history and the existence and extent of flow barriers (e.g. shales) were important to achieving a good match. Fluxes between the NWFB and the remainder of the field were a dominant force in some predictive cases, emphasizing the importance of field-wide reservoir management. The model demonstrated a close link between overall production and management of voidage replacement requiring a good balance between productivity gains associated with reservoir fracture treatments and injection rates.
PNC Log Evaluation in Gas-Filled Borehole Environments: A Case Study
Authors: Hashem M. N. , Gilchrist W. A.
Published: December 2007

This is a case study of Pulsed Neutron Capture (PNC) log evaluation in gas-filled environments. We describe the technique we have used to address the problem caused by the effect of gas-filled annuli on PNC logs in the Gulf of Mexico, south of the Mississippi River. Previous papers have considered the effect of various borehole environments, but none has addressed this specific problem. The PNC log is a key tool in reservoir management, surveillance, and depletion planning in the Gulf of Mexico. However, hydrocarbon saturations based on PNC surveys can be difficult to interpret due to borehole and diffusion effects on the capture cross section measurement, Σ. Although borehole and diffusion corrections are available for many cases, gas-filled annuli still present a significant problem. We have found a method for addressing this problem using the actual log data.