bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of an All-Metal-Sealing Subsea Wellhead System for Critical Service Applications
Authors: Singeetham S. P. , Valka W. A.
Published: December 2007

This paper discusses the design and results of extensive prototype testing of an all metal sealing, weight set, 18-3/4"-15,000 psi subsea wellhead system. This system (Figure 1) has been developed to meet industry requirements of higher pressure and higher temperature in critical applications.

Since the all metal-to-metal sealing packoff is critical to the reliability of the system, emphasis is given to its design and testing. Seal energization and retrieval forces are minimized by the unique seal design. Additionally, the development of an alternative elastomer packoff for use when all metal sealing is not required is discussed. The computer optimized hanger design addresses the need for increased system capacity.
An Environmentally Superior Replacement for Mineral-Oil Drilling Fluids
Authors: Friedheim J. E. , Hans G. J. , Park A. , Ray C. R.
Published: December 2007

Environmental constraints have led to the development of an invert mud system which has excellent toxicity, health and safety aspects, and is biodegradable. This system is particularly suitable for North Sea use where discharges from drilling with mineral oil-base drilling fluids are limited. Based on a synthetic material as the continuous phase, this mud system gives the same high performance as that of mineral oil-base systems. This paper describes this novel mud system and focuses on the impact of its use in environmentally sensitive areas.

The ratio of synthetic liquid continuous phase and aqueous phase (S/W ratio) can vary from 90/10 to 50/50 with mud weights ranging from unweighted to 18.0 ppg. The rheology parameters can be altered with rheology modifiers to give increased low-shear-rate viscosities for enhanced hole cleaning capabilities. Huxley-Bertram HTHP viscometer data shows good stability of the system under downhole conditions. Additional work indicates this system has reduced gas solubility, better lubricity, and lower retention on cuttings when compared to mineral oil-base muds.

Favorable toxicity data, bioaccumulation studies, and biodegradation work have been compiled for both the synthetic material and mud system. U.K. toxicity tests give highly acceptable values. These results, along with the bioaccumulation data, have led the U.K. Department of Energy (DEn) to assign the system a Category 0 classification under its Chemical Notification Scheme. Likewise, the Norwegian government agency (SFT) has agreed to permit this system to be used on a field trial basis. Currently, the U.S. Environmental Protection Agency (EPA) is considering its use, and subsequent discharge of cuttings, for Gulf of Mexico drilling.
Design of Environmentally Safe Drilling Fluids: Tests Under Actual Bottomhole Conditions in an Original Flow Loop
Authors: Degouy D. , Lecourtier J. , Marcassa F. , Forsans T.
Published: December 2007

Numerous additives are now available for designing water-based drilling fluids but in most cases the best conditions for their implementation on fields and their limits of use are poorly documented. This paper presents a comparative study of performances of additives provided by different manufacturers for high temperature well drilling. New environmentally safe drilling fluids usable at temperatures up to 160°C have been designed using the best additives and their performances have been characterized using an original flow loop recently developed by IFP.

This equipment enables the evolution of drilling fluid properties, including HP-HT rheology and static and dynamic filtration, to be characterized inside the loop during aging under actual bottomhole conditions of temperature (180°C), pressure (500 bar) and shear (10000 s-1).

The results indicate that the selected formulations performed satisfactorily during these tests and their field use is now planned. Moreover, these tests provide data allowing field operators to improve predictions and control of the behavior of commonly used additives under downhole conditions.
An Environmentally Acceptable and Field-Practical, Cationic Polymer Mud System
Authors: Retz R. H. , Friedheim J. , Lee L. J. , Welch O. O.
Published: December 2007

With increasing environmental constraints on the use of mineral oil-base muds, attention has turned towards water-base systems. Recent studies have shown that cationic polymer mud systems exhibit a superior degree of inhibition when compared with other water-base muds. Previous considerations of these mud systems were troubled by high toxicity and operational problems. A newly developed, field-practical, cationic polymer mud system gives excellent shale inhibition without sacrificing environmental acceptability.

Cationic polymers provide more effective shale inhibition by attaching to the negatively charged clay surfaces more strongly than anionic polymers. However, formulating practical drilling fluids using cationic polymers is difficult as they tend to react with bentonite, anionic polymers, and weighting agents causing severe flocculation and precipitation. This can cause problems with product compatibility and high mud weights.

Shale encapsulation using this new system is provided by a high molecular weight polymer while swelling inhibition is achieved by using a low molecular weight polymer and/or inorganic salts. Acute aquatic toxicity tests show this cationic polymer mud system is much more environmentally sensitive compared to those previously used. The product incompatibility problem was overcome so that common additives such as bentonite, anionic polymers, and barite can be added for controlling filter-cake quality, fluid loss, and mud weight, respectively. The stability of the system is maintained using non-ionic polymers. Laboratory studies show that the new cationic polymer mud system is considerably more inhibitive than conventional water-base muds.
Measurement of Multiphase Well Fluids by Positive Displacement Meter
Authors: Gold R. C. , Miller J. S. , Priddy W. J.
Published: December 2007

The paper describes a novel positive displacement flowmeter developed to measure the mass and volumetric flowrates of multiphase crude oil fluids in flowlines. After an introductory review of the technical and economic incentives for the development - particularly offshore and subsea, the paper goes on to explain the hydrodynamic problems that hitherto have inhibited the use of conventional metering techniques for multiphase flow measurement.

The paper then describes how these problems have been resolved by a novel combination of simple, well tried principles. The design concepts of the new meter are outlined, together with a brief review of its development from conception to the completion of endurance and calibration tests on two field trial meters. Special features of the positive displacement mechanism design, which enable the meter to withstand rigorous multiphase flow regimes, are explained. Field trial results confirming the meter's capability to resist such conditions are reported, as are the results of independent checks of its measurement accuracy, assessed over a wide range of flow regimes and void fractions. Comparison is made between the performance of the meter and that of a test separator system.
The New UK Oil and Multiphase Flow Measurement Standards Laboratory
Authors: King N. W.
Published: December 2007

The paper describes the new UK Standard for Oil and Multiphase Flow Measurement being built at NEL to replace an existing, smaller laboratory. As well as having a greater single-phase capability, the standard will also include an oil/water/gas multiphase flow measurement standard to meet the needs of the new multiphase flow meters currently being developed. The first of the new flow facilities will be available later this year and all facilities will be fully commissioned by early 1993.

Built as a service to the oil industry it is important that the new laboratory can meet the present and future, needs of that industry. This paper is therefore presented, firstly to inform the oil industry of the capabilities of the new UK Standard for Oil and Multiphase Flow Measurement and, secondly, to invite comments and suggestions from all those with an interest in oil and multiphase flow measurement.
Isolation Techniques for Subsea Gas Pipelines
Authors: Newman W. J. , Saunders P. D.
Published: December 2007

The paper will discuss scenarios and methods to isolate gas pipelines to retrofit subsea valves close to platforms.

The methods discussed represent the conclusions of some of the development work to date by Shell Expro under contract with a variety of contractors over a period of two years.
Retardation of Cement Slurries to 250°F
Authors: Bensted J.
Published: December 2007

Examination of Class G cement slurry retardation up to 250° F has indicated that commonly employed retarders usually give a threshold of unexpectedly long thickening times at ~160-190° F BHCT. Normally, thickening time is not linearly but exponentially dependent upon retarder concentration. The causes of the threshold of long thickening times have been investigated by carrying out appropriate hydration experiments on Class G cements at water/cement ratio 0.44 subjected to thickening under different API Schedule conditions. The cause of the threshold effect has been found to be surge in hydraulic reactivity of the ferrite (C4AF) phase from the Class G cement. The hydration products thus formed, mostly AFt phase or ettringite C3(A, F).3CaSO4.31-32H2O, are deposited on the hydrating clinker surfaces and in particular impede the hydration of the main cementitious alite (C3S) to calcium silicate hydrate (C-S-H), the initiation of which is the prime cause of cement thickening. As a result thickening time is extended and not diminished. However, as the temperature rises above ca 190°F, the increased hydraulic potential of the cement manifests itself. There is no longer an increased surge in ferrite phase hydration to obstruct C-S-H formation, so the C3S hydration rate rises again, culminating in lower thickening times once more. The threshold effect has important implications in cement slurry design.
Emulsion Cement
Authors: Skalle P. , Sveen J.
Published: December 2007

Gas leakage through cement in the annular space around a cemented casing is still a serious problem although new additives and improved techniques have reduced the problem. A new approach is the construction of an emulsion cement, consisting of a double emulsion; water-in-oil-in-cement. Waterdroplets containing a controlled number of species are emulsified into mineral oil. This W/O emulsion is then emulsified into the cement slurry in small amounts (3-15 vol %). The effect of the emulsion on the cement slurry has been recorded through standard API tests. In addition the bond between cement and steel surfaces and the tightness against gas migration have been checked. Compared to other cement slurries, the emulsion cement shows promising results with respect to becoming a friction reducer and an anti gas migration additive. Further tests are necessary to determine the applicability of emulsion cement. Cement slurries behave different at high temperatures, and test procedures and test equipment must be improved in order to comply with down hole conditions.
The Don Field: A Flexible Approach to the Development of a Marginal Field
Authors: Richardson S. M. , Blackburn N. A. , Shere A. J.
Published: December 2007

The Don Field lies in the north-east comer of Block 21 l/18a approximately 15km north of the Thistle Field. The reservoir comprises the Middle Jurassic Brent group of sands and consists of several discrete hydrocarbon accumulations.

The appraisal well data portrayed a complex hydrocarbon bearing structure with considerable uncertainties regarding the degree of faulting, reservoir quality, connectivity and hydrocarbon fluid properties. This pointed to a phased sub-sea development tied back to the Thistle platform, which would allow for systematic reduction of risks, balancing of cash exposure, and lead ultimately to an optimum reservoir management strategy for the field.

First oil flowed in October 1989. Initial performance of the first wells has shown the Don NE reservoir to be highly faulted, and divided into a series of poorly connected compartments. This complex structure severely reduces areal sweep, and recovery from the initial wells will be considerably less than originally predicted.

The paper discusses how the development well results and production monitoring have led to a revised reservoir description of the field. The flexible nature of the Don concept has allowed the development strategy to be modified to accommodate the outstanding reservoir uncertainties, whilst maintaining sufficient production to make effective use of the current facilities.
Fluid Distribution in the Beryl Reservoir
Authors: Erga R. , Knutson C. A.
Published: December 2007

The Beryl Formation, the primary reservoir in the Beryl Field, has a complicated distribution of pressures and fluids. Horizontal permeability restrictions, the result of extensive faulting, subdivide the reservoir into eight inter-related areas as determined by careful analyses of pressure histories, production histories and fluid monitoring. This paper decribes the methodology for constructing a conceptual reservoir model for the Beryl reservoir to identify areas of unswept hydrocarbons, resulting in an aggressive drilling programme, and optimise the effort in simulation history matching.
An Alternative for Shallow Water Oilfield Development in Arctic Waters
Authors: Gaida K. P. , Loh J. K. S. , Mitton F. E. , Pidcock G. A. , Wright B. D.
Published: December 2007

This paper outlines the potential for low cost, shallow water, oilfield development in Arctic waters with equipment that has been utilized in the Canadian Beaufort Sea. A bottom founded structure, Molikpaq, designed and used for year-round Arctic operations, is described along with highlights of previous deployments in the harsh Beaufort Sea environment. The operational flexibility and capability of this structure for use within a range of Arctic offshore development alternatives is discussed, including modifications to the structure for increased production capacity and various transportation options. Cost estimates for these Molikpaq deployment alternatives are also presented so that the application of this proven Arctic technology can be assessed across a range of reserves.
Ivanhoe/Rob Roy Flexible Riser System
Authors: Smith S. N. , Mercer I. L.
Published: December 2007

This paper describes the Ivanhoe/Rob Roy dynamic flexible riser system. The design requirements and considerations are summarised and a general description of the system is given. The paper then concentrates on giving details of the main components involved, thus presenting information on various aspects which are needed to turn theoretical knowledge and techniques into a viable system.
Flexible Risers for J-Tube Pull-In
Authors: McGennis E. , Fleming P.
Published: December 2007

Flexible pipe has been used in a number of recent North Sea projects to upgrade existing platform facilities. This has been done by pulling flexible pipe up through J-tubes to create a new flow path to the top-side facilities. This has eliminated the cost of retrofitting a new riser caisson, and so it can be an economic alternative for the developments which involve a tie back to a host platform. With the increasing interest in this application of flexible pipe, this paper is put forward as an overview of some of the points that have influenced the pull-in projects completed to date.
Tool of the 90's To Optimize Gas-Lift Efficiency in the Gonelle Field, Gabon
Authors: Lemetayer P. , Miret P. M.
Published: December 2007

This paper presents a new method, successfully implemented in March 1990, of operating Gonelle field wells in Gabon. Permanent actions of a programmable logic controller in respect to an expert logic ensure continuous production of the wells with a minimum gas injection rate.

A sharp production increase has been possible despite a simultaneous decrease in gas consumption.
New Water Injection Technology
Authors: Graff O. F. , Nielsen N.
Published: December 2007

Water injection facilities are now used more frequently on offshore platforms to maintain reservoir pressure and hence maintain the oil production capacity and increase oil recovery. The injection of large amounts of treated seawater at high pressure into the reservoir traditionally requires considerable equipment space and power. The system operating weight will also be high.

The development of new fields at increasing water depths has encouraged the use of new technology. The development of topside systems with high efficiency and light weight is thus a challenge for platform designers and equipment suppliers. The water injection system for the Snorre TLP represents a significant advance in the system design, resulting in considerable space savings and a weight saving of about 560 tonnes.

The Snorre Water Injection Facility is the first of a new generation of systems. Cartridge filters which are cleaned by means of sulphuric acid are used for fine filtration of the seawater. The deoxygenation of the seawater is carried out in a two stage nitrogen stripping unit, reducing the oxygen content to below 10 ppb without chemical additives. Vertical injection pumps were also selected eliminating the traditional booster pumps and lube oil system. A full scale test of this unique system was carried out in the summer 1990. Test results showed that all parts of the system were operating satisfactorily and within the design specification.
Tethers 2000: Advances in Offshore Tether Technology
Authors: Casey N. F. , Holmes R.
Published: December 2007

This paper demonstrates work being conducted which will result in advances in the technology of offshore tethering products; steel wire rope, synthetic fibre rope, chain and welded tubulars. The work will have major implications for the improvement of operational safety and discard criteria for mooring tethers. The objective of the paper has been achieved by discussing NEL's current involvement in several major studies and presenting an overview of the research conducted. This research has generated testing of the highest quality through the development of test assessment criteria and gained an insight into the fatigue behaviour of the tether products through the widespread use of condition monitoring techniques.
Reservoir Engineering Aspects of a North Brae Horizontal Well
Authors: O'Byrne D. K. , Fleming C. H. , Prentice D.
Published: December 2007

The North Brae field is the first offshore gas condensate field in the North Sea to be developed by gas cycling for pressure maintenance and improved recovery. Withinthe reservoir the fluid composition changes with depth from a lean gas near the top to an oil rim at the base of the hydrocarbon bearing reservoir in low permeability conglomerate.

This paper details the design and production performance of a horizontal well completion within the oil rim of the North Brae reservoir. The well was completed at a true vertical depth sub-sea of 12405 feet with a perforated horizontal section of 1400 feet in August 1990 and produces condensate at a rate of about 10,000 BOPD.

A multidisciplinary approach to well planning is presented along with results of performance prediction by numerical simulation.The paper gives an insight to the practical aspects of planning such novel completions in the North Sea operating environment.
Effect of Pressure Drop Along Horizontal Wellbores on Well Performance
Authors: Folefac A. N. , Archer J. S. , Issa R. I. , Arshad A. M.
Published: December 2007

The representation of a wellbore in a reservoir simulation model has led to over prediction of productivity index and deliverability of horizontal wells. Recent experience with horizontal wells has revealed that in many circumstances (oil production wells), the inflow performance of horizontal wells and hence their deliverability may be affected by pressure drop along the wellbore. This effect has serious implications on perforated well length because the productivity index is no longer directly proportional to the well length.

Although pressure variation along horizontal wellbores has been reported by some authors: [16] and confirmed by production logging: [17], there still remains the problem of calculating it in a reservoir simulation model. In this paper we describe the equations on which the wellbore pressure drop model is based and present an outline of a novel computational method which solves these equations. The ease with which the wellbore model can be coupled to an existing reservoir simulator is demonstrated.

Altough little dat is available to us, the model is tested for plausibility against production data from a horizontal well. The results indicate that wellbore parameters such as well length, diameter and perforated interval have the most significant effect on the level of pressure drop in the wellbore. The consequences of ignoring this wellbore pressure drop is to over predict the well deliverability. It is also shown the wellbore pressure drop increases dramatically with increase in reservoir productivity.
A Platform Abandonment Program in the North Sea Using Coiled Tubing
Authors: Hoyer C. W. J. , Chassagne A. , Vidick B. , Hartley I. P.
Published: December 2007

A campaign in the North Sea was carried out to permanently abandon 24 wells using coiled tubing (CT). This was used to fulfil the Department of Energy requirement that the production screens had to be plugged back with cement prior to the removal of any well completions. A review of the advantages of using CT and the operational difficulties experienced during the placement of the cement are presented. A financial comparison with present day abandonments, using a rig for the entire operation, is also presented.
Productivity of Multiply Fractured Horizontal Wells in Tight Gas Reservoirs
Authors: Roberts B. E. , van Engen H. , van Kruysdijk C. P. J. W.
Published: December 2007

Horizontal wells can be stimulated by the creation of a number of hydraulic fractures along the wellbore. If the welll is drilled in the direction of the minimum horizontal stress, a series of transverse hydraulic fractures will be induced. The limited communication between such transverse fractures and the wellbore creates a choking effect near the well and causes an apparent reduction in fracture conductivity. Methods to estimate the effect of the limited communication between the wellbore and the fracture based on Darcy flow of fluid in the fractures have been recently reported. Such methods, however, should not be applied to gas reservoirs since non-Darcy flow effects within the fracture may significantly influence well performance, particularly as the degree of communication between the fracture and the wellbore is reduced. This study considers the effect that non-Darcy flow within the hydraulic fractures has on horizontal well productivity in tight gas reservoirs. Well performance was simulated with semi-analytical models and by numerical simulation. The effect of fracture and reservoir properties of gas well productivity is discussed, and various development options for tight gas reservoirs are compared.
Recent North Sea Experience in Formation Evaluation of Horizontal Wells
Authors: White J.
Published: December 2007

The ability to drill horizontal wells is now firmly established, as is the ability to convey formation evaluation sensors into the horizontal hole environment However, the evaluation of these logging sensor measurements requires care in high angle wells. This is because most sensors and interpretation methods have been designed for lower angle holes, typically from 0° to 65° deviation. In near horizontal holes, there is a potential breakdown in radial symmetry around the wellbore, a symmetry that is normally taken for granted in conventional log interpretation. In a typical North Sea layered formation, a good understanding of the volume investigated by each logging sensor is essential to the complete interpretation of logs from near horizontal wells. Examples are provided that show how a layered formation model can be built up using logging data from such wells. This model can then be used to guide any further drilling, improve petrophysical evaluation or help design an optimum completion strategy.

Guide-lines are given to planning a logging job that should overcome some of the uncertainties of interpreting logging data from these high angle wells.
The Prediction of Well Stability Using the Yield Zone Concept
Authors: Somerville J. M. , Smart B. G. D.
Published: December 2007

This paper presents work conducted on borehole stability of consolidated and unconsolidated sandstone formations. A simplified stress equation, developed for work in mine tunnels in soft sedimentary rocks, which has been modified for the case of petroleum reservoir rocks is presented. A method of determining failure criteria from limited unconsolidated samples is presented, and the results used to predict the extent of a failed zone in an unconsolidated formation for various mud weights.
An Operator's View on Safety and Technical Integrity of Jackup Rigs for Drilling in the Nineties
Authors: Colmer R. A. , Sliggers P. G. F.
Published: December 2007

Oil Companies who are generally the Operators of offshore Jack Up drilling rigs have a requirement to be able to assess the structural integrity, the drilling capabilities, and safety aspects of these units. Given that the units are designed against a generic specification it is frequently complex to differentiate between the standards and potential performance of individual rigs. This paper addresses the Operator's requirements for Jack up structural integrity and the desired performance of the drilling equipment.
The Occurrence of Annulus Pressures in the North West Hutton Field: Problems and Solutions
Authors: Attard M.
Published: December 2007

This paper discusses the occurrence of annulus pressures in the North West Hutton oilfield, offshore UK, and how the problems associated with these pressures have been addressed. Several wells have experienced annulus pressures in this field, where production is exclusively via gas lift. The causes of annulus pressures are discussed in the context of the mechanical configuration of the wells. An evaluation of the safety aspects and concerns associated with these pressures is then presented.

Annulus pressure monitoring and operating procedures have been developed for use by offshore production personnel. These procedures contain a list of criteria which, when exceeded, require some type of action to remedy the problem in the well. Some of these criteria are based on a maximum pressure limitation for each well annulus. The derivation and application of these pressures is explained. The final section describes the changes made to the drilling and completion design of wells, in order to prevent or minimise the occurrence of annulus pressures.
Stochastic Models for Seismic Depth Conversion of Geological Horizons
Authors: Abrahamsen P. , Omre H. , Lia O.
Published: December 2007

A stochastic approach to modeling multiple geological horizons in a layer-cake model is presented. Intercorrelations between the different horizons and interval velocity fields are specified and handled properly. Bayesian statistical methods applied to Gaussian random fields provide stable and consistent predictions and simulations for all horizons and interval velocities in the model. Realistic estimates for the uncertainty can be calculated. The methodology is demonstrated by means of a instructive example as well as on a data set from a petroleum reservoir on the the Norwegian continental shelf.
Alwyn North Completion Striving for Reliability
Authors: Raimond M. R. , Graulier J-R.
Published: December 2007

This paper describes the completion principles used for the development of the Alwyn North field. The main goal was to achieve a high level of reliability and safety.

Operational problems during completion installation and exploitation are analyzed. The corrective actions taken to overcome these problems are also described.
Equipment Temperatures in Hot Completions
Authors: Guice W. L.
Published: December 2007

This work illustrates the application of accepted relationships to thermal problems in production equipment. Previous work has shown that relationships which were developed for much simpler cases are adaptable to oilfield problems. The current work illustrates such application in a valve design, and also shows a means of calculating the temperature of a casing seal.
1990's Requirements for Platform Automation Systems
Authors: Daniel C. J.
Published: December 2007

This paper will discuss today's platform automation requirements and how they differ from 1980 designs. As we move into the 1990's in common with downstream activities the design of platform operations are being examined from a total life cost and not purely from the traditional capex/opex point of view. The platform automation pyramid is discussed, containing safety, regulatory, audit analysis and management information system requirements.

The paper emphasizes the need for a totally integrated approach to platform automation systems and highlights the benefits gained.
The Use of Nonlinear Methods in Design of Platforms for Improved Safety
Authors: Medonos S. , Logendra K.
Published: December 2007

Platforms in the North Sea have been traditionally designed using working stress linear elastic methods. These methods are perfectly adequate to simulate normal operational conditions experienced on offshore installations. Use of these methods in design for accidental events, however, leads to over-design which can be costly to fabricate and operate. The criteria for accidental loads are focused on prevention of loss of lives and property, and protection of the environment. As such, they are related to loss of containment or collapse of supporting structures. With the relatively recent technology progress in development of non-linear methods, an elasto-plastic approach is more frequently adopted which enables a platform to be designed for accidental loads with improved safety at a reasonable cost as a result.

This paper describes how use of non-linear methods leads to enhanced knowledge on resistance of structures to accidental loads and improved, safer design. It outlines selection of topside framing arrangement for improved ductility, non-linear verification of jacket imperfections and plastic collapse due to ship impact. The method can also be used for assessment of structural resistance to fire.

It would be an impossible task for a regulatory body to specify all possible accidental scenarios in designing an offshore platform. It is therefore rather the implication of statements in various Rules, Codes of Practice or recommendations which concern us, e.g. risks to the integrity of TSR (temporary safe refuge), escape routes, embarkation points, etc. within a specified period of endurance.
Optimising Efficiency through Intelligent Choice of Technology
Authors: Markley J. I.
Published: December 2007

There are presently three main methods of detecting explosive concentrations of hydrocarbon gases, namely catalytic detectors, infrared point detectors and infrared open path detectors. This paper explains the principles on which such devices operate, summarises their properties and gives suggestions as to when their use seems appropriate.
An Integrated Approach to Prospect Evaluation
Authors: Davies G. G. , Whiteside M. W. , Young M. S.
Published: December 2007

Prospect evaluation requires a multi disciplined approach and should recognise uncertainty in respect of the determination of recoverable reserves, field life production costs, product prices, political and fiscal regimes. This paper compares alternative prospect evaluation methodology and demonstrates, in an example, that significantly different values can be calculated using the alternative methods. An integrated approach to prospect evaluation is put forward and a preferred methodology using an interactive computer model is suggested. The importance of location and the proximity of existing infrastructure to the prospect is discussed, and the incorporation of advances in drilling and subsea development techniques are addressed.
Development and Production Prospects for Oil and Gas From the UK Continental Shelf After the Gulf Crisis: A Financial Simulation
Authors: Kemp A. G. , Rose D. , Dandie R.
Published: December 2007

This paper examines the future prospects for oil and gas in the UKCS with the use of a large financial simulation model. The model contains as inputs all the known information relating to (a) currently producing fields, (b) those under development, and (c) discovered but not developed prospects. The model operates by triggering the development of a field when a given minimum rate of return is in prospect.

The main findings of the study are that oil and gas production will rebound to reach a new peak in the mid-1990s. Gas production from the Central North Sea and the Southern Basin could be buoyant well into the next century, depending on whether recent discoveries are eventually developed. New development investment will be very high in 1991 and 1992 but fall off somewhat in the middle of the decade. A further upturn is forecast for the later years of the decade. North Sea oil and gas will continue to make a major contribution to the UK economy well into the next century.
Sand Prediction and Exclusion Decision Support Using an Expert System
Authors: Peden J. M. , Tovar J. J.
Published: December 2007

The prediction of the occurrence and the production conditions under which sand influx will occur into the wellbore, has always had great impact on well completion design. Several criteria have been used with limited success, most of which are based on complex mathematical algorithms and which were developed for well defined areas.

A model has been developed to assist in identifying sand production problems utilising drilling, logging, core analysis and well test data. The model emulates how human experts in well completion design solve such problems in a predictive mode. Information was gathered and coded in sets of production rules that represent the basic knowledge and reasoning used by the experts. Inferences from conventional data are used instead of complex mathematical algorithms, even though provision is made to include mathematical algorithms in order to compliment the reasoning process of the model. The computerised model is implemented using Artificial Intelligence Technology. The result is a prototype of a knowledge based system for sand production prediction. The process of developing such a system, its applications and further development is described in this paper.
Water Injection Program, Shallow Oil Zone, Elk Hills Field, California
Authors: Walker W.A.
Published: December 2007

The program of water injection at Elk Hills into the main Shallow Oil Zone Sand, the SS-1, has been taking place since February 1958. Injection wells are located to the south and down dip of the oil band to halt the oil movement away from the developed area. The purpose of the program was primarily to reduce or prevent loss of oil resulting from oil saturating sand which formerly had been grey. The paper covers the planning phase of the water injection program, the development phase and the injection phase. The planning phase consisted of a 1) geologic study to determine the magnitude of the aquifer, 2) a regional potentiometric model to define aquifer boundary conditions, flow patterns and pressure distribution, 3) a detailed potentiometric model to determine aquifer geometry, to evaluate the initial production program for slowing migration and to guide in determining injection points and 4) a resistance-capacitance model study to define the pressure effect of various injection patterns and rates. The development phase consisted of the installation of a water collection system, treating and shipping facilities, the drilling of two wells and the installation of a centrifugal water injection pump. The injection phase consists of three and one-half years of aquifer injection and the successful pressure build-up in the oil band.

Introduction

The problems of maintaining reserves of oil in the underground reservoirs at Elk Hills for an emergency supply-of fuel have been discussed in previous papers in the form of progress reports to the industry in 1947 and 1954, references 1 and 2. One of these problems is discussed in this paper. The project is called the SS-1 South Flank Migration Project of the Shallow Oil Zone. In this area a receding edge water in the SS-1 Sand has been causing underground loss of oil due to the oil moving into grey sand. The development of methods to combat this loss are traced through these planning and application phases.

HISTORY

A brief statement of the history of the area will help in understanding the problem.

The development in the eastern part of Elk Hills began in 1920.
Gravel Sizing Criteria for Sand Control and Productivity Optimization: Part II—Evaluation of the Long-Termed Stability
Authors: Chan A. F. , Parmley J. P.
Published: December 2007

Previous laboratory study has demonstrated that adequate sand control can be obtained even though the gravel is much larger than 5-6 times the formation grain size conventionally used as a sizing criteria. In a formation of interest, the −16+20 Ottawa sand was shown to be effective in preventing the production of a formation sand in spite of a 16:1 ratio of gravel to mean sand grain size as determined by sieve analysis. Mechanism studies indicate that the formation sands were clusterized by illite/smectite mixed-layer cementing bonds, and were subsequently mobilized as agglomerates rather than individual sand grains. The critical size parameter for the formation appears to be the mean diameter of the agglomerates and not that of the sand grains. The use of larger gravels, which provides much higher well productivity due to increased permeability, remains consistent with the Saucier's rule.

The long-termed stability of sand control using −16 + 20 Ottawa sand is evaluated in this continuation study. Experiments were performed in flow cells using carcass material and core plugs from a friable sandstone reservoir. Impacts of physical forces such as intermittent pressure surges and long-duration two-phase flow on sand control are investigated. The effects of chemical treatments using common oilfield chemicals, completion brines, and acidizing with HCl, HF, or HBF4 acids are also included.

The results show no deterioration in sand control ability of −16+20 Ottawa sand when subjected to intermittent pressure surges, nor degradation with time during long-duration two-phase flow. The use of diesel, IPA, common completion brines, and seawater has no effect on the sand control. However, exposure to fresh water and acidizing using HF acid resulted in loss of sand control. Permeabilities of the core plugs also became significantly decreased after these treatments. These observations can be explained by the breaking of mixed-layer clay cements due to swelling/dispersing by fresh water or dissolution by the HF acid.

Treatments with HBF4 or HCl acids did not affect the sand control ability of −16+20 Ottawa sand, although some permeability impairments to the core plugs or gravel packs were observed during two-phase flow after HBF4 treatment. Acid treatment with HCl increased the permeability of formation sand significantly, however, the permeability gain diminished somewhat during the onset of two-phase flow.
The Rheological Properties of Carbon Dioxide and Nitrogen Foams
Authors: Valkó Peter , Economides M. J. , Baumgartner S. A. , McElfresh P. M.
Published: December 2007

A large series of experiments was performed to measure the downhole rheology of various quality foams of Carbon Dioxide, Nitrogen and mixtures of the two with aqueous phases consisting of non-crosslinked and crosslinked polymer solutions. Traditional methodology for rheological data analysis, used in small scale horizontal pipe experiments, could not be applied to these large scale vertical experiments because of the interrelation between friction and hydrostatic pressure drops. Therefore, a two-step methodology was developed which consisted of obtaining friction factors from primary data by solving a two-phase vertical flow equation. Then a rheological model was applied to describe the friction factor behavior. A new variable, the specific volume expansion ratio, was found the most useful to correlate friction factor data. The obtained correlation, named Volume Equalized Power Law model, is suitable to represent foam rheology. Model parameters are given for various liquid formulations. A calculational procedure is presented, applicable in field conditions, where a varying quality is always evident.
Evaluation and Comparison of the Formation Damage Models
Authors: Civan Faruk
Published: December 2007

An evaluation and comparison of six selected models bearing direct relevance to formation damage prediction for petroleum reservoirs are carried out. The modeling approaches and assumptions are identified, interpreted, and compared. The model equations are presented according to the SPE symbols Standard and Units. It is concluded that the present models are applicable for special cases involving singlephase fluid systems in petroleum reservoirs.
Hydraulic Rig-Assisted Well Servicing Techniques Can Reduce Formation Damage
Authors: Maddox Steve
Published: December 2007

This paper discusses a technique for the completion and servicing of oil and gas wells while under pressure which can prevent formation damage caused by exposure to kill fluids. Operational procedures and actual field examples of completions and workovers performed with this technique are discussed, and the necessary equipment is described in detail.
Kinetics of BaSO4 Crystal Growth and Effect in Formation Damage
Authors: Wat R. M. S. , Sorbie K. S. , Todd A. C. , Chen Ping , Jiang Ping
Published: December 2007

In the North Sea, due to the extensive use of water injection for oil displacement and pressure maintenance, many reservoirs experience the problem of scale deposition when injection water starts to breakthrough. In most cases the scaled-up wells are caused by the formation of sulphate scales of Barium and Strontium. Due to their relative hardness and low solubility, there are limited processes available for their removal and the preventive measure such as the ‘squeeze’ inhibitor treatment has to be taken. It is therefore important to have a proper understanding of the kinetics of scale formation and its detrimental effect on formation damage under both inhibited and uninhibited environment.

In this paper, we will present results of BaSO4 formation kinetics in both beaker tests and in highly reproducible sandpacks which simulates the flow in porous medium. The effect of scale deposition on the dynamics of formation damage will also be discussed. In the studies of BaSO4 crystal growth kinetics and formation damage, we have included both normal formation/injection brine mixture and the addition of scale inhibitor chemical. There are significant differences in the results of static (beaker tests) and dynamics (core flood) conditions, and between the normal and inhibited brine mix.
New World Record in Extended-Reach Drilling From Platform Statfjord ’C’
Authors: Njaerheim Asgeir , Tjoetta Helge
Published: December 2007

This paper is a case history of the drilling of well C3 from the Statfjord ‘C’ platform, currently the world record in Extended Reach Drilling. The horizontal reach is 6086 m (19 968 ft) and the measured depth 7250 m (23 787 ft), with a sail angle of 80 degrees in the 12 1/4″ hole section. This paper will concentrate on the important aspects of well planning, such as well profile, torque, drag, hole cleaning and surveying, and how the work was executed.
Trajectory Equations for Constant Tool Face Angle Deflections
Authors: Schuh F. J.
Published: December 2007

Prior to the introduction of steering tools and MWD survey equipment, all deflection tools produced circular arc deflections. In order to drill a circular arc deflection the directional driller must change the tool face angle during the course of the correction. With modern bent housing motors and MWD or steering equipment, it is easier and more precise to make corrections using constant toolface angles. Holding a constant tool-face angle produces a uniform vertical build rate which is especially useful for the horizontal driller. This paper presents the derivation of the trajectory equations for drilling constant toolface deflections. The paper also includes both the equations as well as several forms of graphic solutions.
Rig Supervisors: Preparing the Next Generation
Authors: Nordt D. P. , Stone M. S.
Published: December 2007

This paper helps prepare the inexperienced rig supervisor to manage a drilling operation. It outlines operational-knowledge requirements and optimization concepts for improving drilling performance and lowering drilling costs. It gives guidelines on safety and environmental responsibilities, and provides recommendations on work tools, leadership, and communication.
Performance of Rock Bits in the 17½- and 14¾-in. Sections of Germany's Ultradeep KTB Well
Authors: Wohlgemuth Lothar , Meany N. C. , Reinsvold C. H.
Published: December 2007

The Continental Deep Drilling Program of the Federal Republic of Germany (Kontinentinales Tiefbohrprogram der Bundesrepublik Deutschland - KTB) is drilling ahead on its planned 10, 000-meter (32, 808-ft) investigatory borehole in Bavaria, which is expected to reach total depth in 1994. Designed to research the earth's crust, the program was initiated with a pilot hole completed in April 1989 to a total depth of 4000 meters (13, 123 ft). The majority of the pilot hole was cored and the data obtained proved invaluable in planning for the current well, which is located 200 meters (656 ft) east of the pilot hole. Drilling of the current well commenced in October 1990.

Rolling cutter bits were specially designed for drilling the hard crystalline rock. The highly abrasive formations and elevated temperatures, coupled with expected deviation problems, mandated bits be developed to withstand the extremely hostile downhole environment. The bit design program focused on maintaining gage and enhancing bit life under the uniquely challenging downhole conditions.

This paper will discuss the design and performance of a variety of rolling cutter bits used in the 17 1/2″ and 14 3/4″ sections of the borehole, consisting primarily of gneiss and amphibolite rock. The performance of the first 50 bits will be analyzed.