bluuebunny/crossref_metadata_2025 huggingface dataset:
Top-Drive Drilling Systems: Electric vs. Hydraulic-A Technical Overview and Comparison
Authors: Williams M. K.
Published: December 2007

Since 1982 over 300 Top Drive systems have been installed worldwide, on virtually every type of drilling rig. An ongoing debate centres on the prime moverfor rotating the drill pipe. Should it be "electric" or "hydraulic"?

The purpose of this paper will be to provide a detailed comparison of both systems, outlining the advantages and disadvantages of both. Details of the designs, installation requirements, efficiencies, actual field performance and relative cost comparisons to install and operate will be presented.

The results presented will showthe relative merits of each system and technically compare the overall operational aspects of each system as reflected in the current drilling environment we are experiencing today. The data presented will provide the potential user with the necessary information to evaluate an application and select a system.
State-of-the-Art Trip Monitor
Authors: Bible M. J. , Hedayati Z. , Choo D. K.
Published: December 2007

This paper describes a state-of-the-art trip monitor program which makes drilling safer and more efficient. The trip monitor program computes drillstring friction while tripping. The friction calculation is insensitive to the effects of wellbore geometry, buoyancy and BHA used. Volumes of mud and steel transferred into and out of the hole are accurately monitored to detect kicks and losses. The program is flexible enough to work automatically with all fill-up techniques. The program calculates swab and surge pressures in real time and uses pore pressure and fracture gradient information to calculate safe tripping speeds. A rig floor CRT display delivers answers to the driller which he can read at a glance.

This paper outlines the different features of the trip monitor program and the theory behind them. In particular, the friction analysis is discussed in detail to include the influence of the block sheaves and an imperfect description of the pipe geometry on the answer. Field examples are presented to demonstrate the usefulness of the method.
Keys to a Successful Cement Job for a Horizontal Liner on Statfjord A Platform, Well A-37A: A Case History
Authors: Torsvoll A. , Olaussen S. R. , Almond S. W.
Published: December 2007

This case study provides complete details of the steps taken to cement a 700 meter horizontal section of 7in. liner on the Statfjord A Platform, Well A-37A. By properly addressing the four major problem areas associated with horizontal well cementing (displacement mechanics, cement slurry design, cement job simulation, and on-site job execution), a near perfect bond log and complete zonal isolation were obtained.
6,000-ft Water Depth Upgrade of the Sonat Discoverer 534
Authors: Karlsen G. , Sikes J. D.
Published: December 2007

This paper discusses the upgrade of the Discoverer 534, from a turret moored 3500 ft [1100 m] rated drillship, to a fully dynamic positioned vessel rated at 6000 ft [1830 m] water depth. After the upgrade, the vessel commenced drilling in 3730 ft [1137 m] water depth which will be followed by a well in 5900 ft [1800 m] waters during the first quarter of 1991. This will be a world water depth record for a vessel with a 18-3/4 in. [476 irm] BOP stack and a 21 in. [533 mm] drilling riser.
Increasing Reach From 3,000 m to 5,000 m
Authors: Scott P. W.
Published: December 2007

Changes were made to drilling equipment and practices to be able to drill to 5000 metre radius wells from anoffshore production platform. Based on an optimised long reach well design, drilling equipment was sized and selected to achieve good drilling parameters and then integrated into a seven year old drilling rig. Drilling practices were modified to take advantage of the changes and a training programme assisted the smooth resumption of drilling.

The final cost of the upgrade project was US $9.5 million.
Improved Rig Safety by Rapid and Automated Kick Detection
Authors: McCann D. P. , White D. B. , Marais L. , Rodt G. M.
Published: December 2007

Rapid kick detection is an essential part of rig safety. The smaller the influx when detected, the easier it is to control the well. The introduction of an extensive computerised monitoring system on a drilling contractor's offshore fleet has led to the development of displays and intelligent alarms designed to help drilling personnel detect kicks and losses before they would normally be apparent, thus increasing rig safety.

In this paper we describe an automated system with three independent monitors checking once a second for an influx into the well. Field tests and examples demonstrate the effectiveness of the intelligent alarm system.

The Active System Volume and differential flow (Row-out minus Flow-in) are continually monitored both during circulation and pipe connections. Whilst tripping the volume of drillpipe is measured accurately and is automatically compared with changes in the trip tank volume. A graphical representation of the difference between the two is given to the Driller, Rig Superintendent and operator representative, together with alarms when a consistent deviation is identified.

TOTAL’S concern for safety, especially on difficult wells, has led to the installation of the contractor's system on an offshore rig in Indonesia. The results of field tests on this rig are presented together with field examples of real kicks from other systems.
Development of Sour Service Drillstring With 110-ksi Yield Strength
Authors: Tsukano Y. , Asahi H. , Terasawa T. , Ueno M.
Published: December 2007

A sour service drill string with 110 ksi [758 MPa] yield strength has been developed. The NACE threshold stresses are above 90% of the specified minimum yield strength (110 ksiC758 MPa]) for the tool joint and the drill pipe and above 65% for the weld area. Also, the sulfide stress cracking (SSC) resistance of the drill string was totally evaluated by full-size SSC testing. The practicality was confirmed through finite element analysis (FEA) and full-size performance testing (gas leak, full-size fatigue, full-size tensile, overmakeup and make-and-break testing).
New Lightweight Technology for the Primary Cementing of Oilfield Casings in Cold Environments
Authors: Harris K. L.
Published: December 2007

New lightweight cement technology, based on increased cement fineness, has been developed in response to problems associated with cementing primary oilfield casings in cold environments. When low density slurries are required at low temperature conditions, adequate compressive strengths may be difficult to obtain. The new technology presented in this paper, called ultrafine cement, offers lightweight cement slurries (10.0 lb/gal-13.0 Ib/gal) which exhibit much higher early compressive strengths than conventional lightweight systems when cured in cold environments (40°F - 80°F).

By means of laboratory investigation, this paper introduces ultrafine cement as a unique lightweight primary cementing material. Performance properties of ultrafine slurries are discussed and comparisons to commonly used lightweight cements are presented.
Thixotropic, Crosslinking Polymer/Borate/Salt Plug: Development and Application
Authors: Powell J. W. , Stagg T. O. , Reiley R. H. , Dobson J.
Published: December 2007

Off-bottom liner cementing operations in horizontal wells on Alaska's North Slope led to the development of a unique and patented crosslinked polymer/borate/salt (PBS) plug material. Functioning to temporarily plug back the horizontal wellbore while the gas isolation liner is reciprocated and rotated during cementing, the PBS plug protects the production zone from surge and swab pressures and minimizes the risk of sidetracking during cement cleanouts.

Fluid properties and the functional physical and chemical properties of the plug include: viscoelasticity and elevated low shear rate viscosity for plug-flow displacements, and thixotropy to aid plug placement; workable set time; no syneresis; combination of low fluid loss and water/acid solubility to minimize formation damage; a final plug shear strength high enough for functionality and low enough to ensure removal by washing or jetting.

This paper describes the use and field performance of the plug in the off-bottom cementing procedure, and reports pre-set fluid properties, chemical and physical properties, and mixing and spotting procedures. Information is also presented on how the plug has been used to combat difficult lost circulation problems encountered during drilling, workover, and coiled tubing operations.
Effect of Ultrasonic Radiation on Contaminants Adsorbed on Activated Carbon
Authors: Tumeo M. A. , Wheat P. E.
Published: December 2007

A common practice used in water, wastewater and hazardous waste site remediation involves the use of granulated activated carbon to treat effluent waters. When the adsorption cycle is complete the contaminant saturated activated carbon is often regenerated. Regeneration commonly involves the use of high temperature steam (~800-900°C) or solvents to extract adsorbed contaminants. This process may be performed onsite or the contaminated carbon can be shipped off-site for treatment, however, both options present difficulties. Stringent emission requirements and large capital equipment investment often make on-site regeneration economically infeasible. Offsite regeneration poses the added risk of contaminant release during transport and is strongly discouraged under EPA regulations. For these reasons there is great interest in obtaining an activated carbon regeneration methodology which can be economically performed on-site while minimizing potential hazards.

The ability of ultrasound to enhance extraction of organic contaminants adsorbed on activated carbon in the presence of organic solvents has been demonstrated. The use of ultrasonic radiation to facilitate the extraction of adsorbed organic contaminants from the surface of soil and sediments into organic solvents has also been investigated and is recognized by EPA as an approved extraction technique (method #3550).. However, there is no evidence in the literature that any work has been done on using ultrasonics to induce de-adsorption in aqueous environments.

This paper presents the preliminary data from an ongoing study into the use of an ultrasonic field of varying pressure amplitude to induce physical and thermodynamic changes in contaminants adsorbed onto the surface of activated carbon. Increasing radiation intensities up to and including the cavitation point of each heterogeneous activated carbon/aqueous solution system are being investigated and physical changes in the activated carbon as well as contaminant transformation due to cavitation induced modifications examined. The aim of the research is to develop a cost-effective methodology to regenerate contaminated activated carbon, perhaps chemo-selectively.
Pressure-Transient Behavior of Horizontal Wells with Finite-Conductivity Vertical Fractures
Authors: Larsen L. , Hegre T. M.
Published: December 2007

Methods are introduced to generate synthetic pressure-transient data for horizontal wells with finite-conductivity vertical fractures. For the main results flow from the reservoir is only assumed to take place through the fractures, but methods to include flow directly to the wellbore are also outlined. Although the paper is aimed mainly at transverse circular fractures, mathematical derivations for flow to rectangular fractures have also been included. Boundaries and multiple fractures can be treated with considerable flexibility, but examples discussed in the paper are restricted to individual or pairs of circular fractures in unbounded reservoirs, and hence also to single circular fractures in the presence of a sealing fault.

The approach taken follows classical studies of vertical wells with finite-conductivity vertical fractures. Basic solutions are developed in terms of Laplace transforms, with numerical inversion used to obtain end results. The main objective of the paper is to introduce methods to generate synthetic data for fractured horizontal wells. Application of the methods to investigate productivity of various well and fracture configurations has not been considered. Only cases to illustrate the methods are included.

The results of the paper are verified in part by ccmparisans with models developed far vertical wells producing layered and double-porosity reservoirs and with results from a 3D, finite-difference, numerical reservoir simulator.
Model Pile Tests in Saline Soils
Authors: Christopherson A. , Nelson W. , Nottingham D. , Somerville D.
Published: December 2007

The purpose of this project was to measure the secondary creep rate of 4.5 inch (114 mm) diameter steel piles that were forced into frozen saline silt. The silt contained 30% water with a salt content of 33.4 ppt. The piles, embedded in 19°F (-7°C) silt, were loaded to produce shear stresses of 0.5, 1.0, 1.5, and 2.0 psi (3.4, 6.9, 10.3 and 13.8 kPa). Results are compared to published data related to frozen soils containing fresh water.
Evaluation of Vacuum-Insulated Tubing for Paraffin Control at Norman Wells
Authors: Purdy I. L. , Cheyne A. J.
Published: December 2007

Paraffin deposition in the production tubing of wells in the Norman Wells field has been an ongoing operational problem. Although many solutions are possible a passive thermal solution is most desirable. Using a wellbore thermal simulator, it was predicted that vacuum insulated tubing could raise the flowing tubing temperature at the wellhead above the cloud point of the crude oil. A string of vacuum insulated tubing was installed and has performed as predicted by the thermal simulation model.
Wellbore Multiphase-Flow Correlation for the Eastern Operating Area of Prudhoe Bay
Authors: Bradley D. A.
Published: December 2007

This paper describes the development of a pressure-calculation computer program for producing wells. The program is currently in use for the Eastern Operating Area of Prudhoe Bay. An accuracy analysis and some of the results of the use of the program are presented, as well.

The program was developed primarily to provide precise bottomhole flowing-pressure calculations for the entire range of well geometries and flowing conditions existing in the area at the time. Although the friction component of the pressure-drop of a producing well is calculated by using standard correlations, the elevation component is calculated by using an empirical fit of field data. This empirical fit involved the creation and use of a database of well tests and survey pressures for many wells. Ultimately the database was streamlined into two number groups representing the elevation and friction losses for all wells. This causes the program to run as quickly as possible, while providing accurate and smooth results.
Modeling of In-Situ Stress Change Due to Cold Fluid Injection
Authors: Clifton R. J. , Brown U. , Wang J- J.
Published: December 2007

In hydraulic fracturing, the temperature for the treating fluid usually differs from the initial temperature reservoir. Because of fluid migration and heat transfer in the reservoir, such differential temperature induces thermal stresses. This paper presents a computational model, adaptive to hydraulic fracturing simulators, for calculating these thermoelastic changes in the in-situ stress distribution.
Evaluation of Reservoir Fluids Using Formation Tester Tool Samples
Authors: Morris C. W. , Sonnier B.
Published: December 2007

The evaluation of petroleum resources requires a good understanding of the reservoir fluids and their behavior. Specifically, PVT (pressure-volume-temperature) data are required at the earliest possible stage to develop economic evaluations, interpret well test data, design production equipment, and predict future reservoir performance.

A fluid sample obtained with an openhole wireline formation tester tool provides the engineer with the first (and potentially the only) chance to analyze a representative reservoir fluid sample before significant decisions are made. The fluids must be characterized by direct measurement of certain properties and the quality of the PVT laboratory results depends almost entirely on the validity of the sample used for the analysis.

This paper compares the fluid PVT data obtained using samples from wireline formation tester tools and from surface production test equipment. The PVT laboratory procedures and the accuracy of the analysis methods are discussed. The compositional analyses of the hydrocarbon samples are compared, from methane to heptanes-plus chemical structure, along with the key volumetric parameters such as density, bubblepoint pressure, viscosity, formation volume factor, and gas-oil ratio. Different types of reservoirs (with fluids ranging from low gas-oil ratio oils to dry gas) were examined to determine the effects of mud filtrate invasion in the openhole environment, type of fluid, and reservoir characteristics.

In general, the results indicate that samples obtained with wireline formation tester tools can provide representative reservoir fluid parameters from compositional analyses to basic volumetric behavior as a function of pressure and temperature. Critical reservoir parameters such as the fluid density, bubblepoint pressure, formation volume factor, viscosity, and gas-oil ratio are consistent within about 15 percent for most oil reservoir fluids.

Gas condensate reservoir fluids present the most difficult sampling conditions for both the downhole and surface sampling operations. Careful sampling techniques and detailed monitoring of the downhole and surface fluid conditions are required to reconstruct useful results for the reservoir fluid properties.
Shaft and Tunnel Access (SATAC) Concepts for Developing Petroleum Reserves
Authors: Haskin C. A. , Bugno W. T. , Miller R. M.
Published: December 2007

Shaft and tunneling technology commonly employed in the mining and construction industries has been shown to have application in the development of some petroleum deposits. The use of Shaft And Tunnel Access (SATAC) technology in the Athabasca Oil Sands in Alberta has been well documented by Hasten,1 Best,2 and others.3-8

Arctic reservoirs, because of the hostile weather, are among the potential candidates for development using SATAC methods, particularly shallow (<5000’) heavy oil reservoirs. Underground space concepts offer solutions to many problems now commonly associated with developing oil reserves in these and other areas.

While not applicable to all reservoirs, SATAC is recognized technology and should be considered among the available tools to access and develop oil reservoirs. Possibilities include: (1) employing mining to develop oil reserves; (2) using for infrastructure, like access roads and pipelines; or (3) using in combination with other technologies like subsea production.
Creation of High-Productive Seeding Meadows on Disturbed Arctic Lands
Authors: Tikhmenev E. A.
Published: December 2007

The specific features of disturbed lands-heat resource accumulation, aeration and deep seasonal surface melting (up to 1.5-2.0 m) - work to the advantage of their successful reclamation.On the basis of the field experiments an effective technology of the biological stage of reclamation with the use of perrenial grasses has been worked out. This reclamation technology helps to creat valuable communities adaquate to nature. Different species of natural flora adapted to the extreme conditions of the Arctic are being used: Elymus sibiricus, E. mutabilis, Bromopsis inermis, Arctagrostis latifolia. Positive results have been obtained by reclamation of reindeer pastures. The productivity of reclaimed plant cover being 1.5-2 times higher than that of initial native lands. Chemical analysis indicated high quality of plants quite appropriate for reindeer grazing.
Cold Region Hydraulic Oil Applications
Authors: Uhrik S. L.
Published: December 2007

A literature search confirmed that the engineering design for machinery and systems used in cold region environments needs to include an evaluation of the hydraulic oil application. The process begins with a basic understanding of the terms absolute viscosity, kinematic viscosity, cloud point and pour point.

The most apparent effect of cold weather on hydraulic oil is the rapid viscosity increase that accompanies the lowering of ambient temperatures. Viscosity Index (VI) defines this effect. Various authors and methods have attempted to use equations, graphs, and tables to compare this response for different fluids. The theoretical work has found practical application in oil classification systems developed by API, SAE and ASTM.

Viscosity Index improvers, additives and oil blend formulations can overcome the operating problems associated with low temperature. A discussion of this knowledge is presented with applications to aviation hydraulic oils, motor vehicle oil change intervals, storing marine engines for the winter months, starting cold soaked engines and an empirical equation for refinery formulations of summer, winter and arctic product blends.

Guidelines are given to aid in the evaluation and selection of hydraulic fluids for cold region applications. Five major fluid classes are examined. Hydraulic system maintenance and troubleshooting tips complete the presentation.
A Comparison of MWD and Wireline Steering Tool Guidance Systems in Horizontal Drilling
Authors: Gaudin D. B. , Beasley J. C.
Published: December 2007

In horizontal drilling, proper equipment selection is a key factor for success. Particularly in today's horizontal drilling market, where technology is changing so rapidly, a well informed and systematic approach to well planning can help ensure selection of equipment that will result in the most efficient and cost effective drilling program. However, it is often difficult for oil company personnel to assure themselves that they are indeed selecting the best available techniques for particular applications.

One area in which this dilemma is particularly evident is wellbore guidance. Many people are of the opinion that measurement while drilling (MWD) tools are best; others prefer to use wireline steering tools. To determine which method is actually best for any given situation, factors such as economics, availability, accuracy and application should be considered.

This paper analyzes the operational details of each system as they pertain to the different intervals of horizontal wells, and offers comparative information that will help operators in selecting the most efficient surveying method for any application.
The Principle of a Critical Invasion Rate and Its Implications for Log Interpretation
Authors: Fordham E. J. , Allen D. F. , Ladva H. K. J.
Published: December 2007

The interpretation of MWD and wireline logs of invaded formations can be enhanced by an understanding of the controls on invasion rates. Experimental investigation of dynamic filtration rates has shown that under certain conditions these are dependent only on the hydraulic shear stress at the mudcake surface for a given mud composition. They are virtually independent of differential pressure and independent of porous medium permeability (as opposed to mudcake properties) over a 1:104 range. For very low permeability media however, the clear fluid Darcy flux may already be below the dynamic filtration rate. Then no mudcake forms and filtration rates obey Darcy's law. Comparison with theory suggests that there is a critical flux (filtration rate per unit area) above which clay particles accrete irreversibly to the mudcake; below this flux they cannot stick at all.

Invasion volumes at the time of wireline logging are usually dominated by fluid loss that occurred under conditions of dynamic filtration. The conjecture of a critical dynamic filtration rate, dependent only on mud composition and shear, means that invasion volumes should be independent of mud overbalance pressure and of formation properties (permeability, saturation, far field pressure, internal mudcake)—unless formation permeability is so low that it limits the filtration flux to less than the critical flux. Then, formation properties control fluid loss. The permeability at which the behavior changes depends on both mud overbalance pressure and mud flow rate.

These results are important for the interpretation of MWD and wireline logs in the presence of invasion. Field examples of multiple pass MWD and wireline resistivity logs and invasion volume computations from a single pass of wireline resistivity and porosity logs often indicate trends in the invasion volume within a zone or between zones. These trends may be interpreted as indicating differential formation resistance to invasion at low permeabilities but must be due to factors other than the loss rate at moderate to high permeabilities. One such factor is vertical movement of the filtrate under the influence of gravity.
Current Calibration and Quality Control Practices for Selected Measurement-While-Drilling Tools
Authors: Brami J. B.
Published: December 2007

The purpose of this paper is to compile and explain calibration and quality control practices for Measurement While Drilling (MUD) formation evaluation tools for current vendors. MWD logs are usually run in high-operating-cost, geologically complex, and hostile environments. They are commonly justified as "insurance logs" in case the operator can’t get a wireline log. On occasion, these insurance logs become "the only log". Uhen the MUD log exhibits either the desired or expected response, it is believed. Conversely, when an unexpected response is recorded, the MUD log is treated skeptically. Uhen the operator does not believe a log, the data may be suspected to be inaccurate or uncalibrated.

Regardless of the type of measuring device, wireline or MUD, calibrations must be understood before a log is trusted. Standards for reference for MUD logs are not always understood by operating oil company personnel. Over the past 50 years, log analysts have studied and become comfortable with the standards to which wireline tools are referenced. The understanding of calibration practices for MUD tools by oil company operators has proven to be a major hurdle for MUD service companies. Until MUD tool calibrations are understood and accepted by oil company petrophysicists, MUD tools will continue to be followed out of the hole by wireline tools. These redundant logs result in additional cost, risk, and delay in hydrocarbon production.

This paper is the product of several preparation steps. In the first phase of preparation, MWD service companies were asked to supply very general and simplified explanations of how they calibrated or verified their tools. In the second step, more detailed explanations were supplied. Then, several Ad Hoc MUD Calibration Committee meetings were held over the course of a year to develop concise explanations of calibration practices in the MUD industry.

Using a common format and vocabulary, this paper explains MUD calibration practices for gamma ray, resistivity, density, neutron porosity, and caliper tools that are now, or soon to be, commercially available. The data compiled in this paper identify the extent and frequency of calibrations for all major MUD tools. Several case histories are reviewed to illustrate some of the more common quality control concerns. MUD and corresponding wireline logs are shown that raise questions or concerns about invasion and washouts, depth control, and high rates of penetration.

Technical information on tool calibration/verification has been supplied by service companies and has not been independently verified by the authors.
Bending Stress Magnification in Constant Curvature Doglegs With Impact on Drillstring and Casing
Authors: Paslay P. R. , Cernocky E. P.
Published: December 2007

When drill string in a gradual dog leg is subjected to either tensile or compressive axial loads, the maximum curvature of the drill pipe body exceeds that of the hole axis curvature. Lubinski recognized this fact and published an analysis in 1961 for the tensile case. His results are given in the API RP7G manual.

Contemporary technology uses compressive axial loads in some extended reach and horizontal drilling applications. In addition, when casing is set, it is common to have the casing in a dog leg under compression. An analysis for compressive loads, analogous to Lubinski's analysis, is required to evaluate the bending stresses in these situations accurately.

This work presents the analytical solution for maximum drill pipe curvature when an axial compressive load, in the practical range, is applied to the drill string. Similar to the tensile case, contact (point and wrap) between the drill pipe and the hole wall as well as tool joint contact load must be taken into account.

Dimensionless curves are presented for bending stress calculation for both tensile and compressive axial loads. The curves allow easy evaluation of the bending stress magnification (BSM). The results show it is important to take the bending stress and the BSM into account in practical design particularly because of coupling with axial tension and compression loads. The results given in this paper complement calculations based on torque and drag models of drill strings. The results also complement and build on the earlier work of Lubinski.

The results are extended to burst and collapse analysis in casing and to fatigue analysis in drill pipe. The important influences of BSM are made clear in design curves for these applications.
The Effects of Temperature, Pressure, and Angle of Deviation on Free Water and Cement Slurry Stability
Authors: Matson R. P. , Rogers M. J. , Go Boncan V. C. , Gandy R. G.
Published: December 2007

The importance of free water control upon slurry design and performance in deviated and horizontal wellbores has been recognized and documented. The literature contains suggested procedural modifications to API Spec 10, Free Water Test, to better approximate bottom-hole cementing conditions. Suggestions include (1) pre-conditioning the slurry in a pressurized consistometer at bottom-hole conditions, (2) conducting the Free Water Test at various angles from a vertical position, (3) utilization of a new settling tube for evaluating the degree of segregation of the cement particles (density segregation). Little has been written on the interaction of temperature, pressure and increased slurry surface area due to deviated conditions on free water and cement slurry stability.

This paper presents laboratory results of a comparison between the current API Free Water procedure, modified API Free Water procedure and modified British Petroleum Settling Tube Test. The comparison includes differences in both free water and slurry stability at elevated temperatures and pressure at various angles. From this research, results highlight possible unsupported optimism concerning cement slurry performance in deviated and horizontal applications when based on current API Free Water Test procedure.
Analysis of a Gas Kick Taken in a Deep Well Drilled With Oil-Based Mud
Authors: Tarvin J. A. , Walton I. , Wand P. , White D. B.
Published: December 2007

A gas kick taken in a deep well drilled with oil-base mud is simulated with a new model. In comparison to one taken in water-base mud, this kick shows relatively small increases in annulus pressure and pit level as the gas is circulated to the surface. Solubility of the gas in the drilling mud is the key to understanding these measurements. Even though the formation permeability is the only adjustable parameter in the model, the calculated surface pressure is very close to the measured pressure throughout the slow-circulation phase.
Controlling Kicks in Ultradeep Wells and Comparison With Shallow Wells
Authors: Schöffmann F. , Economides M. J.
Published: December 2007

Kick control for ultradeep boreholes has certain important distinguishing features from the kick control for more "normal" depth wells. The annular pressure profile vs. time is different in the two cases because the initial shut-in pressure in the ultradeep holes is large and sometimes it is the largest during constant bottomhole pressure (CBHP) kick control, resulting in small gas expansion effects. In shallow holes, the lower initial shut-in pressure and low pressure level (compared to ultradeep borehole annular pressures) throughout the kick control operation results in significant gas expansion. Therefore the annular pressure during the kick control may be substantially higher than the shut-in pressure. Thus, the critical period between the two cases happens at a decidedly different time. Kick simulation for ultradeep holes is presented in this paper for different CBHP methods using waterbase muds in any borehole geometry. The worst case, that of a sudden influx of a gas slug is used. The results are profiles of surface annular pressures, identifying the largest pressure value at each depth during the kick circulation with the CBHP methods. This allows the quantification of the load on a borehole during controlled CBHP kick-killing-operations at any depth.
An Analysis of Relative Costs in Drilling Deep Wells
Authors: Andersen E. E. , Cooper G. A. , Maurer W. C. , Westcott P. A.
Published: December 2007

INTRODUCTION

The search for new sources of oil, and particularly gas, is leading the industry to drill ever deeper wells. A depth of 15,000 ft was first passed in 1938, 20, 000 ft was reached in 1939, followed by 25, 000 ft in 1958, and 30, 000 ft in 1972. The current US record depth is 31,441 ft. As the total depth increases, not only does the rock to be drilled become stronger, but increasing pressure and temperature induce plasticity and "chip hold-down" effects that make it more difficult to remove cuttings from the workfront. In addition to the reduction in rate of the drilling process itself, other activities become more complex and time-consuming, for example, tripping, running and cementing casing, and logging and coring activities.

We have analyzed the different tasks involved in drilling deep wells, in order to identify those activities that contribute most to the overall cost. These are therefore expected to be the activities where future efforts in research and development should provide the greatest reductions in total cost.

OVERALL EFFECTS OF INCREARTNR DRPTH

We have obtained information from a large drilling database that contains data on over 3000 wells, drilled in all parts of the world, both on land and offshore, during the period 1977-1988. The majority of these wells were for exploration rather than production. Some of the major findings include the following:
U.S. Petroleum Engineering Manpower Supply & Demand: A Reversal of Trends
Authors: Ghalambor A. , Miller M. A.
Published: December 2007

INTRODUCTION

The purpose of this paper is to report the results of the supply and demand surveys conducted annually by the SPE Manpower Committee1

As in previous years, the 1991 Demand Survey was sent to selected employers of petroleum engineering graduates, including major companies, independents, and service companies. A total of 33 companies responded to the survey. Twenty-eight were complete and usable.

Results of the survey indicated that total engineering employment in the upstream petroleum industry is expected to be essentially flat for the next couple of years, although there would appear to be a decline in the number of engineers employed by large producing companies, with corresponding increases by small producing companies and service companies. The supply/demand situation for new petroleum engineering graduates is expected to remain relatively steady.
Abnormal Permeability Behavior of a North Sea Sandstone Reservoir
Authors: Mikkelsen M. , Scheie Å. , Rong O. , de Boer E. T.
Published: December 2007

Special core analyses on sandstone samples from a North Sea oil reservoir showed unusually large variations in absolute and effective permeability. Abnormally high endpoint relative permeability to oil was observed during primary drainage oilfloods. Absolute air permeability was in many instances several times higher than the absolute water permeability. In order to improve the understanding of the causes for this particular behaviour, a comprehensive laboratory core study was carried out.

Comparative studies on several suites of parallel samples showed that air permeability and primary drainage endpoint oil permeability were strongly dependent on experimental procedures. Miscible cleaning and critical point drying are preferred to conventional methods. Establishment of initial water saturation by oil flooding gave less change in permeability than centrifuge and porous plate methods. Water permeability was less sensitive to experimental procedures, but significant changes were still observed. A reversibility in permeability was noted with many samples; decreases were often observed when going from air or oil saturated plugs to water saturated plugs, whilst increases occured when going the opposite way.

The rock material was characterized with respect to mineralogy, morphology and pore size distribution. The study showed that the permeability effects seem to be dependent on the content of filamentous illite. Analyses of fluid effluents showed significant particle migration only in cases of two-phase flow.

The study demonstrated that control over experimental effects is important and demanding, but still achievable, for this type of sensitive rock. It contributed to an improved data basis for further reservoir evaluation and better understanding and procedures for future core analysis on this rock type.
European Innovation and Technology Development
Authors: Johnson R. W.
Published: December 2007

The promotion of technological innovation by European national governments and the EC in pursuit of both increased recovery and the anchoring of technology in supply, manufacturing and service sector companies has been a feature of the strategic involvement by European states in exploration and production research and development. This paper summarises past trends in this activity and reviews the targets for future industry innovation which will enable European (primarily the North Sea) production to be sustained for a further generation.
A Theoretical Analysis of Vertical Flow Equilibrium
Authors: Yortsos Y. C.
Published: December 2007

The assumption of Vertical Flow Equilibrium (VFE) and of parallel flow conditions, in general, is often applied to the modeling of flow and displacement in natural porous media. However, the methodology for the development of the various models is rather intuitive, and no rigorous method is currently available. In this paper, we develop an asymptotic theory using as parameter the variable RL=LHkVkH It is rigorously shown that present models represent the leading order term of an asymptotic expansion with respect to 1/RL2 Although this was numerically suspected, it is the first time that it is theoretically proved. Based on the general formulation, a series of models are subsequently obtained. In the absence of strong gravity effects, they generalize previous works by Zapata and Lake (1981), Yokoyama and Lake (1981) and Lake and Hirasaki (1981), on immiscible and miscible displacements. In the limit of gravity-segregated flow, we prove conditions for the fluids to be segregated and derive the Dupuit and Dietz (1953) approximations. Finally, we also discuss effects of capillarity and transverse dispersion.
Experimental Testing of Mobility Predictions in Averaged Models of Viscous Fingering
Authors: Sorbie K. S. , Tsibuklis N. B. , Dwebi A.
Published: December 2007

Averaged empirical models of viscous fingering are frequently used in order to incorporate the effects of miscible viscous instability into coarse grid simulations of processes involving adverse mobility ratio displacements. However, in order to evaluate these models, it is not sufficient to compare the predictions which they make with effluent profiles in 1D displacement experiments since this only tests the transport properties of the model. It is also necessary to compare the predictions of effective mobility of these models with experiment in order to evaluate their use for application in the modelling of multidimensional displacements. The effective mobility can only be assessed directly when the pressure drops are measured along the fingering zone in miscible unstable displacements and such experiments have not previously been reported. In this paper, miscible viscous fingering results have been presented for "2D linear" displacement experiments at mobility ratios of approximately M = 4, 11 and 30. Both effluent profiles (recoveries) and pressure drops along the fingers have been measured and the reproducibility of these in each of the experimental cycles in repacked beds is very good. The effluent and pressure behaviour has been modelled using direct fine grid numerical simulation and a number of averaged models of viscous fingering have been evaluated using the experimental pressure data including the Koval, Todd and Longstaff, Fayers and the Odeh and Cohen models. It has been found that direct numerical simulation reproduces both the experimental effluent concentration profiles and the observed pressure drop behaviour very well. However, of the averaged model approaches, the Todd and Longstaff and an equivalent mixing model give the most satisfactory agreement with the observed effective in situ mobilities (pressure drops) in the fingering zone. Both the original Koval model and the modification proposed by Odeh and Cohen do not give good agreement with experimental pressure drop measurements. The approach of Fayers also has some shortcomings in that it predicts a viscosity in the finger zone that is too low (i.e. effective mobility is too high) due to the presence of an unphysical shock front behaviour which this model exhibits.
Steam-Foam Diversion Process Developed To Overcome Steam Override in Athabasca
Authors: Sander P. R. , Clark G. J. , Lau E. C.
Published: December 2007

The Grégoire Lake In-Situ Steam Pilot (GLISP) was the first steam foam flood performed in Athabasca. The recovery process developed at GLISP used inherent reservoir characteristics to advantage. Inter-well communication was established in an upper zone of low oil saturation. Steam diversion using in-situ foam was then used to successfully mitigate steam override to that zone. Foam injection improved oil production by as much as 100%. Additional testing was performed to optimize surfactant and steam injection rates. This paper presents results of the steam foam testing, and is a case history follow-up of SPE 19690. GLISP production, injection and reservoir temperature profiles are used to outline the results of the steam foam diversion process.
Observation of Foam/Oil Interactions in a New, High-Resolution Micromodel
Authors: Hornbrook J. W. , Castanier L. M. , Pettit P. A.
Published: December 2007

A new micromodel construction procedure has been developed as a tool to better understand and model pore level events in porous media. The construction procedure allows for the almost exact two-dimensional replication of any porous medium of interest. For the case presented here, a berea sandstone was chosen.

Starting with a thin section of the porous medium of interest, a two-dimensional replica of the flow path is etched into a silicon wafer to a prescribed depth. Bonding the etched pattern to a fiat glass plate isolates the flow path and allows the pore level flow events to be studied.

The high resolution micromodels constructed with the new procedure were used to study the effects of oil on the displacement characteristics of foam in a porous medium of intermediate wettability. A crude oil was injected into the micromodel, partially filling it. The oil was then produced under two different displacement schemes. First, a slug of surfactant was used. Second, foam generated in situ, far from the oil bank, was used to displace the oil.

Qualitative observations indicate significant differences at the interface between the oil and the displacing phase. When slug surfactant injection is used, the oil appears to wet the surface. The oil displacement process is efficient due to a large fractional production of oil from the large pores before the surfactant breaks through. When in-situ foam is the displacing phase, the foam is observed to break near the oil interface. The liquid phase in the foam becomes the wetting phase. It is observed to reside in the small pores and to coat most of the grain surfaces. Displacement of oil under this injection scheme is inefficient due to transfer of the surfactant along grain edges and subsequent early breakthrough of the surfactant.
Mechanisms of Miscible Oil Recovery: Effects of Pressure on Miscible and Near-Miscible Displacements of Oil by Carbon Dioxide
Authors: Shyeh-Yung J-G. J.
Published: December 2007

This paper presents results obtained in a laboratory study investigating incentives for near-miscible CO2 processes. Reservoir-condition corefloods were completed in both idealized and West Texas-type fluid/ rock systems at pressures above and below the minimum miscibility pressure (MMP). Coreflood oil recoveries and CO2 mobilities are presented to examine effects of pressure, initial saturation, and volume of CO2 injection.

Results show that decreases in tertiary oil recovery at pressures below the MMP are not as great as suggested by slim tube tests. The presence of water in the core apparently reduces the pressure sensitivity. In addition, it was found that CO2 mobility is reduced by the presence of a miscible flood residual oil saturation (Sorm), which increases as the pressure decreases. Both observations suggest that lower pressure (near-miscible) CO2 EOR processes have potential to economically recover oil.

Two oil recovery mechanisms, low interfacial tension (IFT) displacement and extraction of oil components, were found to be important. This is deduced from analyses of produced oil compositions. Lower IFT (higher pressure) and lower initial water saturation enhance displacement and reduce pore level bypassing. Extraction dominates after solvent breakthrough; extraction increases with pressure and decreases with water saturation.

The work suggests that, whenever possible, slim tube tests be replaced with reservoir-condition corefloods which provide more realistic data not only on pressure sensitivity, but also on miscible flood residual oil saturation and solvent mobility.
Pseudo-Steady-State Flow and the Transient Pressure Behavior of Fractured Wells: A New Analytical Technique for Complex Wellbore Configurations
Authors: Collins R. E.
Published: December 2007

An almost exact closed form analytical solution for the transient pressure behavior of a fractured well in an infinite domain is obtained by a new approximation technique of broad applicability. This solution is shown to yield a simple analytical expression for type curves which can be used to determine fracture length from a pressure build-up curve. It can also be used in a pressure interference test to determine fracture orientation. Most importantly, this paper is a tutorial for applying this solution technique to other well completion configurations.