bluuebunny/crossref_metadata_2025 huggingface dataset:
E.M. MWD Data Transmission Status and Perspectives
Authors: Soulier Louis , Lemaitre Michel
Published: December 2007

After 20 years of DHMWD the market is still demanding a tool which is discreet and can operate reliably whatever the status of the rig. The electromagnetic transmission overcomes its primary depth limitation and matchs drillers requirements: high reliability, no drilling contraints…, this paper summarises the technology status and points out the potential for future developments.
Polyglycol and Aluminum Chemistry Drilling Fluid Helps Operator Reach Project Goals
Authors: Halliday W. S. , Jones T. A. , Sketcher Byron
Published: December 2007

In the Gulf of Mexico and other parts of the world, bit balling and differentially stuck pipe has resulted in lengthy and costly drilling delays. In recent years the most effective mud system to combat these problems has been oil-base muds. Oil muds provide superior shale inhibition characteristics and excellent lubricity. However, due to increasing environmental concerns and regulations, in certain cases oil muds have become unacceptable options. Viable water-base alternatives, on the other hand, have been developed to incorporate the desired inhibitive and lubricous properties associated with oil-base muds without the problems associated with disposal.

Recently an operator planned an offshore Louisiana multi-well program of directional wells through depleted sands. Past problems in the area include bit balling in hydratable shale sections and differentially stuck pipe in subnormally pressured zones. Until recently oil muds have provided the only solution. After researching the field and testing various inhibitive water-base fluids, the operator implemented a polyglycol (PPG)/aluminum complex water-base system. This system imparts lubricity and shale inhibition characteristics approaching that of an oil-base mud but without the environmental liability.

To date nine wells have beep successfully drilled with the PPG / aluminum complex fluid with no occurrence of stuck pipe, bit balling, or wellbore instability. Additionally, the operator has been able to reduce its total well costs which can be attributed to the following: (1) reducing the number of bits, (2) reducing the number of drilling days, (3) reducing the size of the drilling rig, (4) eliminating the incidence of stuck pipe, and (5) eliminating disposal costs.
Gas Kick Warner-An Early Gas Influx Detection Method
Authors: Stokka S. , Andersen J. O. , Freyer J. , Welde J.
Published: December 2007

A system for early detection of gas while drilling has been developed and taken through field tests onshore and offshore. The working principle of the tool is to measure the propagation time of a pressure pulse travelling through the well. It is generated at the standpipe and travels down the drillstring, through the bit and up the annulus, where it is detected at the top. Small amounts of free gas in the annulus can be detected while downhole.
PDC Bit Selection through Cost Prediction Estimates Using Crossplots and Sonic Log Data
Authors: Falcao J. L. , Maidla E. E. , Dumans C. F. , Dezen J. F.
Published: December 2007

PDC bit technology has developed into an attractive and economical alternative in many drilling scenarios.

Although much has been done for bit selection and optimization for tricone bits, much is still to be done for PDC bits, due to the difficulty of modeling the PDC wear, bit whirl and account for the many types and geometrical configurations of the existing PDC in the market today.

This paper presents a method to select a PDC bit through predicting the lowest drilling cost for a given situation of interest, given the shear stress level it will be subjected to.

The method uses all data from the PDC bit records, therefore containing many different lithologies and rock properties. It is based on the comparison of past bit performance and correlates it to the formation's shear stress. Graphic outputs play a key role in the analysis to queue in to a particular data group of interest within an extensive bit database.

The proposed procedures have been validated using data from 49 wells from 6 Brazilian fields and the results showed that the cost savings are significant. Examples are presented and discussed.
Horizontal Turnkeys: Trends of the Future?
Authors: West Mark , Eggleston Wayne , Patton W. F.
Published: December 2007

This paper presents a case study of a horizontal turnkey well in Southeast Texas. Figure 1 The drilling contractor had overall responsibility for the well, while the horizontal drilling company turnkeyed the directional services from the kickoff point to the end of a predetermined amount of horizontal displacement. Obviously, a close working relationship was necessary for such an undertaking between operator, drilling contractor and horizontal drilling company. The paper attempts to evenly address general management's interests in the turnkey and incentive drilling aspects of the project, as well as the directional aspects of the horizontal drilling operation.

Specific engineering differences between turnkey and daywork contracts on a horizontal well are discussed. Contractor and service company roles are examined at different points in the drilling process. For the sake of this discussion, the well will be classified into three sections: the straight section of the hole, the build section and the horizontal section. Also discussed are the criteria required to affix geological targets in a given plane so that the direction of the well can be firmly set.

Finally, the methods used to derive the contract parameters for this turnkey project are addressed, i.e., days estimate, bottomhole assembly types, bit types, etc. The conclusion covers lessons learned and the final results of the project.
North Sea Advances in Extended Reach Drilling
Authors: Eck-Olsen Johan , Sletten Haakon , Reynolds J. T. , Samuell J. G.
Published: December 2007

This paper describes strategies and techniques employed to extend the drilling reach in the Gullfaks field, offshore Norway. Field development plans were originally based upon deviated wells drilled to a maximum inclination of 60° and a maximum displacement of 3 km. Emerging horizontal drilling techniques encouraged a reevaluation of these field development plans. These techniques are now being implemented to increase the inclination and extend the reach to 5 km in support of the revised plan. The early success achieved has urged further consideration of extended-reach drilling to as much as 10 km.
The Importance of Rotation Effects for Efficient Cuttings Removal During Drilling
Authors: Lockett T. J. , Richardson S. M. , Worraker W. J.
Published: December 2007

Successful and economic drilling of highly deviated wells requires the efficient transportation of cut rock to the surface. This paper uses computer simulations of fluid flow and particle transport to investigate whether the removal of rock cuttings is greatly enhanced by toroidal vortices generated by the rotation of the drill-string.
Electronic Identification of Drillstem and Other Components Used in Harsh Environments Proves Successful
Authors: Shepard J. S. , Perkin G. S. , Denny L. A.
Published: December 2007

A reliable and more foolproof means of identifying industrial components for Inventory Control, that minimizes human error and reduces asset management costs, has been a challenge to the oilfield and energy industries for many years. Manual systems that require locating assets and visually finding their unique product code and/or serial numbers is rapidly becoming outdated.

This paper discusses a new alternative method for electronically identifying industrial assets, to include those used in the oilfield, which are subjected to harsh environments. A harsh environment is defined as one in which the asset is used or placed into various extremes of temperature, pressure, erosion, corrosion, vibration, handling, dirt and debris. The results of three (3) extensive downhole tests, utilizing this method, will be discussed and presented.
Preliminary Model Experiments in Redox Well Logging (with Applications to Mineral Exploration)
Authors: Pirson S.J. , Negut Aurelian
Published: December 2007

Preliminary Model Experiments in Redox Preliminary Model Experiments in Redox Well Logging (with Applications to Mineral Exploration)

Model laboratory experiments were performed to simulate stratified sedimentary rocks drilled with fresh muds in which the only potential-contrasts in existence were redox [Eh] and potential-contrasts in existence were redox [Eh] and diffusion [Ed] potentials.

It is shown that the conventional SP curve measures but a small fraction of the total redox potential contrast between the formations, potential contrast between the formations, whereas the redox log recorded in the wellbore may measure a large fraction of the Eh contrast.

Experiments with simulated salt muds indicate that satisfactory measurements are achieved with the redox log, whereas the SP curve is completely suppressed.

The SP curve appears as a subdued curve of the redox potential contrast between formations except that the SP curve is not responsive to the presence of hydrocarbons in clean sands nor to the water-oil contact.

By contrast the redox log may be run in salt muds [inorganic salts] and it indicates the presence of hydrocarbons in formations and the presence of hydrocarbons in formations and the oil-water contact. However, the redox log may not be run satisfactorily when the mud is rich in organic substances such as oil and quebracho.

Example logs illustrate the paper together with example surveys of redox potential measurements in exploration for oil and gas fields, for uranium and for native sulfur ore bodies.

THE REDOX OR Eh POTENTIAL

Oxidation-Reduction Potential [or ORP or redox potential or Eh] is a measure of the tendency for chemical species in ionic solution to change their oxidation or reduction state. It is also a quantitative measure of the energy of oxidation or of the electron-escaping tendency of a reversible oxidation-reduction system.

Chemical reactions involving the transfer of electrons and protons, i.e., of electric charges, depend either upon the pH [a measure of the proton activity] or on the Eh [a measure of the electron activity] or on both pH and Eh of the systems in which the reactions take place. Such reactions at equilibrium are governed by the following general expression at standard conditions:

(1)

in which a is the number of protons [H+] and n is the number of electrons [e-] taking part in the reaction. The equilibrium conditions are thus represented by a straight line on a Cartesian plot of Eh vs pH, the slope of which is [60a/n] mv/pH unit. Eo is the standard potential of the reaction. potential of the reaction.
Design, Execution, and Evaluation of Minifracs in the Field: A Practical Approach and Case Study
Authors: Thompson J. W. , Church D. C.
Published: December 2007

Numerous technical papers have been written on the subject of analyzing the pressure-decline data from a mini-frac. Various theoretical models have been presented which addressed the uncertainties involved from the ideal assumptions originally presented by Nolte. Most of the publications written, however, have dealt mainly with the theoretical modeling of the pressure decline and not the practical application of performing a mini-frac in the field.

The intent of this paper is not necessarily to discuss the theoretical analysis and design applications of modeling mini-fracs, but to discuss the practical steps involved to properly design, execute and evaluate a mini-frac. The basic concept of the mini-frac is presented. Guidelines are given on how to design a mini-frac, record bottomhole pressure (BHP), obtain closure and interpret the data. Field case studies are presented which illustrate the step processes involved in performing and evaluating a mini-frac.
Project Planning: The Key to Offshore Arctic Drilling Success at Kuvlum
Authors: McKay T. W. , Pidcock G. A.
Published: December 2007

In recent years the frequency of offshore Arctic drilling has declined such that most of the equipment has been shut down or removed from the region. Similarly, many of the personnel and services for mounting an offshore drilling project have been dispersed. The task therefore to plan and execute a short notice drilling project in Camden Bay presented some major hurdles for the Operator, ARCO Alaska, Inc., and the Drilling Contractor, BeauDril.

This paper will describe the project planning details and techniques involved in the short time leading up towards drilling the ARCO Kuvlum No. 1 well offshore the north coast of Alaska. The assembly of numerous highly technical resources to perform this operation required the identification of key milestones and communication to the ever growing project team. Most importantly, the Operator/Contractor team approach will be outlined from the proposal through the contract and startup phases.

In addition to the operational planning, the paper will also address the array of regulatory and community requirements that were planned in support of the project. Careful attention was paid to commitments and deadlines in this area so that all necessary approvals and certificates were received prior to committing major project capital expenditures.

The 1992 phase of the project was completed in the fourth quarter of that year, and the paper will reference some of the actual operations and how the plan was utilized during the different phases of the operation.
Pattern Size Reduction: A Reservoir Management Tool for Prudhoe Bay Waterfloods
Authors: Suttles D. J. , Kwan G. W. L.
Published: December 2007

Introduction

This extended abstract, in support of a poster session, describes the use of the concept of Pattern Size Reduction (PSR) to improve waterflood recovery. This concept incorporates infill drilling, producer-to-injector conversions and peripheral waterflood expansion. Waterflood recovery is primarily improved by creating smaller patterns, improving pattern geometry, increasing the rate of injection throughput and ultimate throughput volume.

Screening Study

A parametric study was conducted in early 1991 which correlated ultimate recovery with controllable field operating variables1. This study clearly showed that patterns with tighter well spacing, higher ultimate injection throughput and optimum pressure maintenance had higher recoveries. It also indicated that more symmetrical patterns have higher recoveries. This study was used to identify areas within the various Prudhoe Bay Unit (PBU) waterfloods where waterflood optimization can improve recovery. These areas were subsequently studied in greater detail and re-development plans created.

The two example given below characterize the analysis techniques used and the results obtained.

Analysis Example – "A" Pad

The parametric study identified the "A" pad area of the WPWZ waterflood as having a lower than average projected ultimate recovery. This pad also had the largest pattern size and well spacing of any PBU waterflood. A multi-company development team, composed of staff from reservoir engineering, production engineering, geosciences and facility engineering, was created and challenged to come up with a re-development plan which would improve "A" pad recovery.
Fluid Surveillance Enhancement as a Valuable Tool in Reservoir Development
Authors: Shirzadi Shawn , Bundy Thomas , Zerzan Michael
Published: December 2007

Often in a mature oil field the question is asked: where is the remaining oil in place, ROIP, and how much oil is left? However, recently the reservoir and production engineers have added the third question to the quest for additional oil recovery. The third question deals with the uncertainty in the distribution and volume of the remaining oil in place in an under-developed part of the field. The integrated work of geologists, production engineers and computer geoscientists can lead to developing a volumetric model which utilizes formation properties, stratigraphy, and fluid surveillance data to determine the ROIP volume, as well as the associated uncertainty with regard to the ROIP. This presentation gives an overall view of the process which produces reservoir grids of original and current fluid in place volumes, and uncertainty factors to be utilized by reservoir and production engineers in targeting future development in the field. Also, these products can be used to enhance and optimize fluid surveillance exercises in the under-developed regions of the field.
The Evaluation of Heterogeneous Skin Effect Reservoirs
Authors: Rowland David A. , Miller Frank G.
Published: December 2007

Transient pressure testing is used extensively as a means of determining formation flow capacity and extent of well damage around producing wells. Analytical expressions developed for evaluating the results of pressure testing are based generally upon the assumption of homogeneous rock properties, even though reservoir inhomogeneities such as faulting, lensing, stratification, fracturing, and anisotropy introduce anomalies in the pressure test data and may affect the accuracy of calculations. This paper presents the results of an investigation of skin effect evaluation in reservoirs having horizontal and vertical permeability variations. A two-dimensional mathematical model in r-z geometry was used to generate these results.

Analysis of results using the mathematical model to simulate various heterogeneous reservoir systems indicates that when vertical permeability variation (stratification) exists, the determination of skin effect and formation flow capacity may be performed in the usual manner. On the other hand, whenever radial discontinuities exist, as in lenticular and composite reservoir systems, considerable differences in computed values and actual values of skin effect occurred These differences may be construed to be another form of skin effect. This led to the development of a technique for determining true skin effect that generally gives reliable results in reservoirs having radial permeability discontinuities.

INTRODUCTION

Well damage caused by drilling reduces the production potentials of producing wells and results in great economic losses to the petroleum industry. The economic effects are of two types. First, well damage restricts the rate of fluid flow into we II bores, delaying income that might otherwise be put to good use. Second, it can induce premature abandonment of wells, resulting in less ultimate recovery and less income. Hence, the accurate evaluation of the influence well damage has on productivity is of great importance to the petroleum industry.
Predicting Economic Life Under Conditions of Changing Technology
Authors: Shamblin James E. , Maddox Robert N.
Published: December 2007

In the process of planning new, major investments such as refineries or chemical plants, management should have an estimate plants, management should have an estimate of the economic life of the facility. Economic deterioration is presented as the result of increased operation and maintenance cost and economic obsolescence caused by technological advances while considering the effect of interest or time value of money. Economic life is defined as the service life of an installation which results in a minimum total cost when compared to future alternatives.

This paper develops a model for this purpose, illustrating and interpreting the purpose, illustrating and interpreting the results by means of an example. A derivation of the general model is provided to develop the logic-behind the necessary assumptions.

Methods of sensitivity analysis are demonstrated to provide means of establishing the significance of possible errors in estimating data or to justify simplifying assumptions. In addition, sensitivity analysis is used to determine an operating range to add flexibility for management level decision-making.

Using the general model, an example problem is used to illustrate application and to problem is used to illustrate application and to suggest methods of obtaining valid estimates.

In addition, the example problem is used as a basis for interpretation of the cost factors and the results obtained.

Introduction

In planning a major investment, such as a gasoline plant or a refinery, management should have the means to estimate the anticipated economic life of the facility. This paper presents a model developed for this paper presents a model developed for this purpose and uses concepts of sensitivity purpose and uses concepts of sensitivity analysis to indicate the effects of errors in data estimation or changing conditions upon cost. An attempt has been made to use data in such a form that it may be easily estimated.

The economic life of a facility is defined as that period of use which results in the minimum total cost. Replacement of the facility at a date earlier or later than this optimum life will result in increased cost. In general, the facility would be expected to be in satisfactory operating condition at a time beyond this point, however it would be operating at a deficit from the economic standpoint.
Subseismic Faults in Reservoir Description and Simulation
Authors: Munthe K. L , Omre Henning , Holden Lars , Damsleth Eivind , Heffer Kes , Olsen T. S. , Watterson Juan
Published: December 2007

A program system based on a stochastic model of the fault pattern and properties has been implemented. The faults are modelled as fault planes and displacement of adjacent rock. Realizations of the fault characteristics in a reservoir can be generated.

The generated set of faults is applied to a reservoir description (permeability field). The fault planes may act like barriers to fluid flow. The displacment of rock can disconnect a high permeable zone and thereby reduce the overall flow properties. On the other hand, it can also connect high-permeable rock and improve flow.

Although the reservoir geometry and properties are changed by the faults, well observations may still be honoured by taking faults into account when creating the description.
Real-Time Quality Control of Foamed Cement Jobs: A Case Study
Authors: Thayer R. D. , Ford D. G. , Holekamp Steve , Pferdehirt D. J.
Published: December 2007

Foam cement is a low density cement system prepared by mixing nitrogen gas and surfactants with API Portland cement. The lower density limit for conventionally extended slurries is between 11.0 and 12.0 lb/gal. Foaming permits cement slurry densities lower than water (8.33 lb/gal) while maintaining relatively high compressive strengths. These advantages and others have been well documented.

Actual field mixing procedures and additive rates are critical and must be monitored to assure a competent foam cement. Slight variations in base slurry density, base slurry rate, foamer and stabilizer rate, or nitrogen rate can significantly alter the final foam density. Formerly, foam density was measured by a radioactive densitometer. This allowed for significant error when densities were less than 8.33 lb/gal. There was no physical means to collect and weigh an actual foam cement sample.

This paper explains methods to improve the accuracy of the additive rates. It also defines a method for real-time measurement of foam cement density. The paper describes the use of a high pressure device downstream of the nitrogen addition that can weigh a pressurized foam cement sample during the job.
Fracture Initiation and Propagation from Deviated Wellbores.
Authors: Weng Xiaowei
Published: December 2007

This paper presents the results of an analytical study of hydraulic fracture initiation and propagation from deviated wellbores. The interaction and link-up of the starter fractures initiated from perforations and the turning of the linked fracture are investigated. A criterion that correlates fracture link-up to stresses and wellbore parameters is established. The characters of the near-wellbore multiple fractures and their effects on fracture width reduction and friction loss are also studied. The model-predicted pressure response, which takes into account the near-wellbore friction loss, is compared to the measured bottom hole pressure data during a fracture treatment.
Thermodynamic Measurement and Prediction of Paraffin Precipitation in Crude Oil
Authors: Erickson D. D. , Niesen V. G. , Brown T. S.
Published: December 2007

Economically and technically viable methods for controlling paraffin buildup in pipelines and wellbores are critical to the production of crude oil in deep water and cold environments. Conoco has identified laboratory test methods and developed a paraffin prediction program to better quantify the paraffin (wax) deposition potential of a crude oil and to evaluate or develop methods of preventing or controlling paraffin buildup. This paper will describe the thermodynamic paraffin model and the complementary laboratory test methods. A companion paper will describe the kinetic deposition model and the associated laboratory and field data.
The Use of Laser Doppler Velocimetry (LDV) for the Measurement of Fracturing Fluid Flow in the FFCF Simulator
Authors: Mears R. B. , Sluss J. J. , Fagan J. E. , Menon R. K.
Published: December 2007

Laser Doppler Velocimetry (LDV) is an optical point velocity measuring technique that has revolutionized velocity measurements in hostile flow environments. The high pressures and high temperatures encountered in hydraulic fracturing simulations at the Fracturing Fluid Characterization Facility (FFCF), coupled with the abrasive character of the proppant laden fracturing gels proposed for study, makes LDV the preferred technique for this application. This paper describes a unique nine probe LDV system that is applied to fluid flows in the FFCF simulator. The LDV system consists of nine specially designed laser probes, three power supplies, a unique signal processor/multiplexer, and a personal computer for system control and data display. In addition, three automated precision traversing stages are coupled to three of the laser probes for velocity profile studies. This system has been applied to both Newtonian and non-Newtonian fluids in the simulator at several crack widths and flow rates. Some point velocity data, along with extensive velocity profile data, is presented and discussed for several fluids. The fracturing fluid studies presented are for flows without proppant. The velocity profiles are compared to theoretical models that are applied with volumetric flow rates measured by an independent flowmeter. The results show that LDV is a valuable tool for gathering point velocity information from fracturing fluid flows in the FFCF simulator.
Gamma Ray Absorption Measurements, Laboratory Experiments in Bottomhole Conditions
Authors: Putz A. G. , Morineau Y. M. , Begani Rino
Published: December 2007

A gamma ray attenuation measurement apparatus performs saturation measurements during core flood experiments in bottomhole conditions. Pressure and temperature limits are 450 bar and 170°C. The core, with a maximum length of 1 meter, is mounted vertically. An americium 241 source and a detector can be translated and rotated very precisely along and around the core.

Two complex studies of primary depletion have been run, each lasted close to a year. The first experiment was a light oil depletion in a Berea core at 136°C and 220 bar, the other was a condensate gas depletion in a composite dolomite core at 406 bar and 135°C. The methodology of the saturation measurements is presented together with the saturation profiles. The accuracy of the results is determined in each case.
Matrix Permeability Measurement of Gas Productive Shales
Authors: Luffel D. L. , Hopkins C. W. , Schettler P. D.
Published: December 2007

Three laboratory methods were developed to measure matrix gas permeability (Km) of Devonian shale cores and drill cuttings at native water saturations. The first method uses pulse pressure testing of core plugs with helium. The second, new method uses pulse pressure testing of core chips or drill cuttings with helium. These methods gave comparable results on 23 companion shale samples from two wells, with Km = 0.2 to 19 × 10−8 md. The third, new method uses degassibility of core plugs with helium and methane, and yielded Km higher by a factor of 3 to 10. Most of the core plugs tested showed multiple microfractures that remain open at reservoir stress, and these dominate conventional flow tests. These microfractures are parallel to bedding, are coring induced, and are not present in the reservoir. Knowledge of Km is important in computer simulation modeling of long term Devonian shale gas production, and has been a key to understanding the nature of the natural fracture network present in the reservoir.
Tracking Injected Components in Fully Compositional Reservoir Simulations
Authors: Kim J. S.
Published: December 2007

A new method to track injected components has been successfully tested in fully compositional reservoir simulations. This method treats the injected components independently from the corresponding components indigenous to the original reservoir fluid in fluid characterization and reservoir simulation. This approach enables tracking both injected and resident reservoir components separately at the surface production stream and within the numerical model. Two test applications of this method, a gas cycling operation and a CO2 flood operation are discussed in detail along with the results.

Typical injectant components such as CO2, methane, ethane, or propane often exist in the initial reservoir hydrocarbon fluid. This makes it impossible to distinguish between injected and resident components in the conventional compositional reservoir simulations. In this work, at least one of the common components is represented as a pseudo-component with identical equation of state parameters: one initially present in the resident reservoir fluid, the other to be carried in the injection gas. Thus, both injected and resident components are traced separately in the surface production stream and within the reservoir fluid. This paper details how this method has been used to depict injected hydrocarbon gas or CO2 breakthrough, estimate make-up gas volume requirements and CO2 retention rate more rigorously, and track movements of injected components at different times during simulation studies.

This method gives the same results as the conventional techniques in equation-of-state characterization, oil production, GOR changes, and individual component concentrations in two simulation applications with only a 5–65% increase in computer time due to the added components. It is very useful in visualizing physical phenomenon such as mixing zone growth and injectant breakthrough. By tracking concentration changes and movements of injected components such as CO2, methane, ethane or propane within a numerical model and in the surface production streams, mass transfer effects can be clearly depicted during simulation studies.
An Economic Model for Assessing the Feasibility of Exploiting Naturally Fractured Reservoirs by Horizontal Well Technology
Authors: Guo Genliang , Evans R. D.
Published: December 2007

An economic model for assessing the feasibility of exploiting naturally fractured reservoirs using horizontal well technology is presented. Detailed equations are derived for calculating the cost, return on investment and discounted net present value over the production life of a naturally fractured reservoir. An analytical production forecasting method is also developed for predicting the future production performance of horizontal wells in naturally fractured reservoirs. A computer program is developed which can be used to perform the production forecasting and economic evaluation of a naturally fractured reservoir for any given natural fracture characteristics, horizontal well configuration and reservoir fluid properties. A case study indicates that the proposed economic evaluation and production forecasting models provide a simple analytical tool for assessing the production process of complex naturally fractured reservoirs intersected by horizontal wellbores. They allow engineers to identify an optimum horizontal well drilling scheme from comparisons of the production and economic performance profiles for various alternatives.
An Evaluation of Recent "Mechanistic" Models of Multiphase Flow for Predicting Pressure Drops in Oil and Gas Wells
Authors: Pucknell J. K. , Mason J. N. E. , Vervest E. G.
Published: December 2007

The reliable calculation of tubing pressure drops in oil and gas wells is important for the most cost effective design of well completions. None of the traditional multiphase flow correlations works well across the full range of conditions encountered in oil and gas fields. Consequently, two of the recently published "mechanistic" models, one by Ansari, the other by Hasan & Kabir, were evaluated. The performance of these methods was compared against traditional correlations in three ways:

The predicted against measured pressure drops were compared for stable flow conditions using 246 data sets collected from 8 producing fields, including a gas and gas-condensate field. None of these data were available to the developers of any of the multiphase flow models evaluated. Suitable methods should reliably predict the "lift curve minima". This determines when a well may need to be "kicked off', artificially lifted or recompleted. The multiphase flow model must not contain discontinuities or be subject to convergence problems.

No single traditional correlation method gives good results in both oil and gas wells. In fact, most of the traditional methods which work reasonably in oil wells give very poor predictions for gas wells.

Hasan & Kabir's mechanistic method was generally found to be no better than the traditional correlation methods. However, the Ansari mechanistic model gave consistently reasonable performance. Although it did not give the most accurate results in every field, it gave reasonable results across the complete range of fields studied. The Ansari method also gives a reliable prediction of the lift curve minima. Areas in which it needs improvement were identified.

By comparison the best of the traditional methods, the Hagedorn & Brown correlation, gave good results for stable flow conditions in oil wells, but it does not correctly predict the lift curve minima. A field example shows how this can lead to erroneous conclusions.
Strategic Exploration and Production Portfolio Management Using Marketing Planning Techniques
Authors: Harrison Robert , Jeffs Paul
Published: December 2007

A method for managing the asset portfolio of an oil E&P company is proposed based on marketing planning techniques proven within the commercial sector. A multi-tiered approach is adopted to allow consideration of assets, both producing and prospective, within a regional, national or basinal context. The use of life-cycle concepts, gap analysis and directional policy matrices to evaluate and rank assets is illustrated through reference to a typical diversified North Sea portfolio. The implementation of these techniques within a company environment is also discussed. As well as allowing properties at different stages of maturity to be compared, appropriate strategies on how to manage the assets at each stage of development can be deduced from the categorisation introduced by the policy matrices. The method presented also allows the forecasting of potential shortfalls in production and facilitates strategic planning decisions to change the nature and size of the portfolio. The method is considered to be rigorous and rational and constitutes an improved, auditable technique for E&P portfolio management.
Beryl Alpha – Condeep GBS Analysis
Authors: Galbraith D. N. , Hodgson T. , Darby K.
Published: December 2007

A significant upgrade to the topsides facilities of the Beryl Alpha platform has recently been undertaken by Mobil North Sea Limited (MNSL). Structural reassessment of the deck structure was performed to demonstrate its continued integrity under the resultant increase in topsides loads. Previous papers [1. 2] describe how this was achieved with only minor strengthening. The reanaiysis has now been extended to incorporate an assessment of the concrete gravity base substructure, which is of the Condeep design. VTNSL's purposes for undertaking this reanaivsis were to:

– reassess the structure taking into account the platform's operational history and the increased deck loads: – review the implications of extending the operational life: – investigate how the reinforced, prestressed concrete design performs against contemporary rules and codes: – provide a basis for future inspection: – provide a rapid reanalysis capability in the event of accidental damage or freak environmental loads.

Many aspects of the substructure design were evaluated, thus providing a unique opportunity to review the performance of a Condeep and its foundation after eighteen years of operation. The analysis included the development and validation of hydrodynamic and all other loads. A particular feature was the integrated use of both a simple skeletal simulation of the platform and a detailed finite element model. Extensive concrete code checking has been performed to a number of limit states using specialist software.

This paper presents the philosophy employed in, and discusses the preliminary results of, this analysis.
Planning and Start-Up of the Heidrun TLP Predrilling Program
Authors: Actis S. C. , Smith K. L. , Chenier D. E.
Published: December 2007

Development drilling at the Heidrun field offshore mid-Norway is currently underway. The Heidrun field will be developed with a concrete hull Tension Leg Platform (TLP) in 345 meters (1132 feet) of water1,2. The pre-drilling program to be conducted from a semi-submersible includes drilling and partially completing nine wells, setting 30" conductor and 22" surface liners in the remaining 47 TLP-template well slots and drilling and completing 6 water injection wells in two remote subsea templates.

This paper will review the extensive planning as part of the overall Heidrun project and present a review of drilling operations to date. The state of the art drilling techniques being implemented to overcome unique drilling problems and complete the substantial scope of work will be described.
Piloting Safety Cases To Support Decisive Management of Change
Authors: Wong Norman
Published: December 2007

This paper discusses the piloting work done by Amoco (U.K.) Exploration Company, from 1988 to date, in developing safety cases for a total of 21 diverse installations in the United Kingdom sector of the North Sea.

The period is characterised by an unprecedented degree of change during which operators have sought to achieve a practical and consistent outcome in anticipation of new offshore safety regulations finally introduced in 1993 [1].

The paper describes Amoco's approach to the management of that change, the formation and the work of the Amoco Safety Case Team, and the value of the information and experience obtained during the process. It concludes by discussing the key elements in the project's success and the future challenges facing the industry in continuing to implement the new approach to safety.
Features of a Safety Case for a Complex of Platforms with NNM's
Authors: McIntosh A. M.
Published: December 2007

July 6th 1988 saw the worst disaster in the history of offshore operations. The total destruction of the Piper Alpha Platform claimed the lives of 165 of the 226 persons on board, and two of the crew of a fast rescue craft. The Public Inquiry into the Piper Alpha disaster led to the publication of the so called "Cullen Report' in November 1990 containing Lord Cullen's 106 recommendations for improving or achieving optimum safety.

The report was welcomed and the recommendations were quickly accepted by the UK government. Many people envisaged the report as having a radical effect on the design and construction of offshore installations, and while this is true to a point, detailed examination of Lord Cullen's recommendations show that the greatest part of these related to Safety Management. Over half his recommendations refer to management and training issues, approximately a further 25% deal with safety engineering assessment and analysis and only about 25% relate purely to hardware issues.

Lord Cullen's first and overriding recommendation was that operators should be required by regulation to submit a Safety Case, similar to the CIMAH Safety Report, for each of its installations. He was firmly directing operators towards assessing and demonstrating a safe operation via the production of a Safety Case as is now required by the Offshore Installations (Safety Case) Regulations 1 992 and if the operator can make that demonstration then he will have met the intention of the vast majority, if not all of, Lord Cullen's recommendations.
A Joint Industry Research Project to Investigate Coiled-Tubing Buckling
Authors: Tailby R. J. , Cobb D. O. , Riva M. C. , Jones Colin , Rydland J. A. , Christensen O. S.
Published: December 2007

A joint industry project (JIP) has been conducted to investigate the behaviour and limitations of coiled tubing (CT) in a horizontal well environment. Full scale testing (FST) revealed limitations in traditionally accepted industry theories and changes have been implemented in field operating procedures. Residual bending in the CT, tip (end) load, and well profile are critical parameters with regards to maximising coiled tubing penetration into a well. Computer models have traditionally predicted significantly less penetration in these wells. However, recent testing and field experience has confirmed extensions to these predictions. This paper describes the JIP and presents the main results and conclusions, including some reference to recent field examples.
Continuous Semirigid Electric Line for Downhole Measurements in Highly Deviated Wells
Authors: Fay Jean-Baptiste , Huvey Michel , Grosjean Francois
Published: December 2007

The development of highly deviated to horizontal wells has raised the problem of using downhole measurement tools where such tools can no longer be run in under the simple effect of gravity. Transmission of a force from the surface, whether thrust or traction, to a logging tool at a depth of several thousand metres can be achieved by semirigid stems. Such stems made of composite materials — glass or carbon fibres embedded in a resin — may also include a way of transmitting data. As compared to steel, the combination of materials such as fibres and resin provides advantageous mechanical properties with regard to traction strength, flexibility and lightness. Moreover, the continuous manufacturing technique — pultrusion — is well suited both for producing long single-unit lengths and for inserting any line such as a monoconductor, multiconductor or coaxial electric conductor.

So far, several lengths of semirigid stems, including end fittings, have been produced, reaching more than 200 metres of single-unit length and showing that the extension to several thousand metres raises no technical problem. The principal parameters of the composite material such as the Young's modulus, the ultimates stress and strain have been measured during bending, tension and compression tests. Dynamic tests in tension and bending have also been performed.

The use of a semirigid stem may be considered by itself or inside a coiled tubing:

When used by itself to push or pull a tool in a highly deviated borehole, the integrated electric conductor ensures two-way data transmission; When used inside coiled tubing, it preserves all the inherent advantages of the coiled tubing (implementation, high-pressure hydraulic conduit). More hover, the semirigid stem is fully compatible with winding/unwinding cycles, and it protects the electric line from any damage.
Reliability of Well Completion Equipment
Authors: Moines Einar , Sundet Inge
Published: December 2007

This paper presents the methodology and results from a major research project on well completion equipment reliability. Historical data were collected and analysed from a large number of installations represented by 17 participating oil companies.

The data were analysed using a purpose designed software package for reliability analysis (CERED). A standardized reliability data collection format was defined for the most critical items of downhole completions and implemented in this software package.

Generic and detailed reliability data are presented for entire completions as well as specific items, such as tubing, annulus safety systems, electrical submersible pumps and downhole permanent gauge systems. The paper also discusses the potential benefit of using reliability data as a decision basis, with consideration of limitations in data quality. The database established in this project represents nearly 800 completion equipment failures covering some 6600 well years of operation.

A separate database is established and maintained by SINTEF on Surface Controlled Subsurface Safety Valves (SCSSV). The paper also describes some long term trends in SCSSV reliability extracted from this database which now holds information on some 1400 failures. The latest update of this database was completed and reported in February 1992 as an integral part of the well completion study.

The cooperation with the participating oil companies and the major completion equipment manufacturers was instrumental in obtaining useful results in the study and is described in detail in the paper.
Win 90's in Practice: Implementation and Results
Authors: Crozier S. C. , Hoekstra Piet , Blake A. J. , McKee J. D. A.
Published: December 2007

1991 saw the implementation of a new approach to well construction in the U K sector of the North Sea with Well Engineering in the Nineties (WIN 90s). With this new approach the responsibility for drilling is devolved to drilling contractors, allowing the operator to concentrate on core business. This has provided the opportunity to streamline the drilling process through integration and improved supply chain management. The use of teams is building close customer – supplier relationships throughout the supply chain, and developing a common purpose focused on the needs of the operator.

After 18 months of WIN 90s operations, there are clear signs of benefits to the operator, the drilling contractor and the drilling service contractors. This paper discusses the results achieved so far in the development of new relationships, the reorganisation due to the shift of responsibility to the drilling contractor and the implementation of quality management. The results of the initiative are measured in terms of safety, drilling performance and productivity. The paper also discusses the work required to take WIN 90s to the next stage, and the opportunities available for further improvements.