bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

Abstract
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

ABSTRACT
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

Abstract
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

ABSTRACT
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.
1990's Requirements for Platform Automation Systems
Authors: Daniel C. J. 
Published: December 2007

ABSTRACT
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

ABSTRACT
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.
An Integrated Approach to Prospect Evaluation
Authors: Davies G. G. , Whiteside M. W. , Young M. S. 
Published: December 2007

ABSTRACT
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

ABSTRACT
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

ABSTRACT
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.