bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Gas Dispersion and Explosions in Offshore Modules
Authors: Johnson D.M. , Cleaver R.P. , Puttock J.S. , Van Wingerden C.J.M.
Published: October 2008

There has been considerable progress over the last decade in validating models to predict the loading resulting from an explosion in an offshore module. However, much of the experimental work that provided the validation of the models has involved using idealized gas clouds, generally natural gas or methane at a single concentration throughout the whole volume. This paper describes an experimental project and modeling work undertaken to provide a more realistic representation of the risks posed by gas explosions in offshore platforms. The project involved laboratory, medium and large scale experiments, examining the effects of realistic fuel mixtures, realistic gas release conditions and nonhomogeneous gas clouds filling only a portion of the module. Comparison with gas dispersion and explosion models was also carried out.

Background

The Blast & Fire Engineering Project for Topside Structures [1] was initiated in May 1990 to study the special explosion and fire hazards facing offshore operators. The objective of Phase 1 of this joint industry project (JIP) was to provide interim guidance to designers and operators to reduce the potential for a major disaster offshore as happened on the Piper alpha platform in 1988. In addition to providing this interim guidance, this project recognised that there was a need to obtain data on these hazards from full-scale experiments. Therefore, as part of the follow-on Phase 2 project, a series of experiments was undertaken to obtain quantitative data on the explosion hazard in full-scale geometries truly representative of the offshore environment [2].

The results of this project indicated that high explosion overpressures could be generated and that water sprays activated prior to ignition could significantly reduce these overpressures. As a consequence of these findings, the UK Health & Safety Executive (HSE) commissioned a further project, known as Phase 3A [3], in which experiments were undertaken to identify methods of reducing the severity of explosions.

The Phase 2 and Phase 3A projects showed that it is generally not practical to design an offshore platform against the ‘worst case’ explosion. Therefore, a risk based approach for design against explosion hazards is needed in which the risks are reduced to as low as reasonably practicable. In taking a risk-based approach, it is important that the full spectrum of possibilities is adequately understood. This includes scenarios involving ignition of a non-homogeneous gas cloud occupying only part of the module. The Phase 2 and 3A projects had, however, been conducted with homogeneous gas clouds throughout the full module, and in most cases the mixture had been at a stoichiometric concentration. This was appropriate at the time, as it was necessary to understand of the scope of the explosion hazard and to provide well defined experiments against which explosion models could be validated. However, there was a clear need to investigate more realistic conditions.
The Discovery of U-166: Rewriting History with New Technology
Authors: Church Robert A. , Warren Daniel J. , Hill Andrew W. , Smith Jonathan S.
Published: October 2008

During World War II, Hitler sent several of Germany's Uboats to the Gulf of Mexico to conduct warfare on merchant shipping and halt petroleum shipments. In less than a year, fifty-six merchant vessels were sunk and several others were severely damaged. During that entire operation only one Uboat was lost in the Gulf of Mexico. That U-boat was the U- 166. Since 1942 the U-166 was thought to have been sunk by the U.S. Coast Guard south of Isle Dernieres, Louisiana in the South Timbalier Area. Numerous surveys have crossed the area, but no trace of the U-166 was ever identified until recently.

In 2001, C & C Technologies, Inc. (C & C) began using the HUGIN 3000 AUV for offshore oil and gas surveys in the Gulf of Mexico. While conducting a pipeline survey for BP Exploration and Production Inc. (BP) and Shell International (Shell), C & C's marine archaeologists identified a sonar target in the vicinity of the shipwreck, Robert E. Lee, which they thought might be the long sought after German U-boat, U-166. The oil companies approved further investigation with the HUGIN 3000, which revealed spectacular sonar and multibeam bathymetry images lending further evidence to the U-boat hypothesis. On May 31 a research team from C & C, the Minerals Management Service, BP, and Shell conducted an ROV investigation of the site confirming the identity and location of U-166 and its last victim, the Robert E. Lee.

Introduction

In January 2001, BP and Shell contracted C & C to survey a route for the Okeanos pipeline. In doing so BP and Shell supported the use of a newly developed deepwater survey vehicle. C & C would use their new HUGIN 3000 AUV, a state of the art deep-water survey vehicle. This AUV carries a full array of survey instruments and is capable of faster and more accurate surveys than conventional deep-tow systems. The oil companies willingness to take advantage of this new technology lead to an astounding discovery that helped solve a captivating historical mystery in the Gulf of Mexico.

The HUGIN 3000 AUV (High Precision Untethered Geosurvey and Inspection System, Autonomous Underwater Vehicle) is a third generation AUV by Kongsberg Simrad and the first commercially operated AUV capable of surveying to 3000 meters water depth. The HUGIN 3000 is the result of the cooperative efforts of C & C and Simrad, and was developed out of a commitment from BP for next generation survey technology.1 This AUV is integrated with a multiinstrument survey payload consisting of a Simrad EM 2000 (200 kHz) swath bathymetry system, dual frequency Edgetech Chirp side scan sonar (120 kHz and 410 kHz), and an Edgetech Chirp subbottom profiler. Because it is an untethered system, running on internal power, it can operate even in rough seas at faster speeds with greater mobility and accuracy than conventional towed arrays.
Thales GeoSolutions AUV Sensor Integration
Authors: Cannon Stewart
Published: October 2008

Traditional AUV development has involved designing a vehicle, making it operational and then fitting available sensors to it. The Thales approach has been to integrate the vehicle and sensor systems during the design stage. This has produced a highly integrated system that is smaller and lighter than contemporary designs. This paper describes the results of this integration and the performance of the vehicle and sensors produced by the design.

Introduction

AUV's have caught the offshore industry's imagination and are being billed as the weapon we will be doing battle with in the future. A quick survey of AUV's currently operating or in late stages of development for commercial operations shows an amazing range of sizes and shapes and very few design trends. On the one hand are very large vehicles that are designed to operate at speeds up to eight knots and at the other extreme are small vehicles designed to operate at more limited speeds with multiple vehicles. We at Thales GeoSolutions have chosen the latter approach.

From personal experience with AUV's dating back a number of years it appears that many designs have evolved from a generic AUV into a survey tool merely by adapting sensors to an existing vehicle design. With the Sea Oracle we have had the luxury of designing a vehicle around a sensor. One area of agreement there seems to be in the commercial AUV marketplace is that multibeam echo sounder data collection is the most important task for AUV's. Therefore the Sea Oracle AUV has been designed around a multibeam echo sounder system.

The Thales GeoSolutions Sea Oracle AUV is based on the third generation Odyssey class vehicle designed by Bluefin Robotics. Bluefin are a spin-off from MIT's Sea Grant AUV lab and produce military vehicles and science vehicles along with survey vehicles in commercial partnership with Thales GeoSolutions. The MIT lab's Odyssey II class vehicles developed many new AUV technologies such as a monocoque hull. The main feature of the Odyssey II class AUV of interest to Thales GeoSolutions was its simplicity. Since they didn't have hovering thrusters and were capable of simple mission profiles they were able to focus on the problems specific to AUV's and were able to gain valuable experience an a large number of dives.

Figure 1. Odyssey II Class AUV.(Available in full paper)

Bluefin, in conjunction with the Monterey Bay Aquarium Research Institute (MBARI) then produced a design for an Odyssey III class vehicle that would be configurable for different missions. The resulted in a vehicle that was tubular, 21 inches in diameter and had three or more separate sections. The key to the design was a common tail section that contained the propulsion, control, main vehicle computer, navigation system and communications. Essentially the tail section was the AUV.
An Introduction to Marine Electrical Methods: Towed Resistivity & Towed Induced Polarization Applied to Marine Geotechnical Problems
Authors: Graham Richard F.
Published: October 2008

The geoelectric methods of DC resistivity and induced polarization (IP) have had a long history as complementary geophysical tools with which to remotely explore the earth. Pioneering work on both techniques dates to earliest part of the last century. Resistivity had gained industry acceptance well before the middle of last century; while due to its more sophisticated hardware requirements, IP's commercial establishment lagged until the later half of the last century. The ability of marine towed resistivity systems to quickly and effectively categorize sediments in the near subbottom has been commercially demonstrated in the telecommunications industry. The application of DC resistivity to other geotechnical problems is discussed. Also discussed are the limitations of DC resistivity and the application of marine towed IP to problems where DC resistivity falls short.

Introduction

Williamson & Associates has figured prominently in the relatively brief history of the application of electrical methods to marine geophysical survey. First, in the early 1990's, in partnership with Cable & Wireless Marine, Ltd. (now Global Marine Systems, Ltd.), Williamson & Associates launched the first commercial foray into marine resistivity with the commissioning of two C-BASS (Cable Burial Assessment Survey System) sleds. The C-BASS program was followed by second partnership, this time with Sage Engineering, Ltd., (now Thales, Inc) leading to the development of two deeptowed ReDAS (Resistivity Data Acquisition System) systems.

Both the C-BASS and ReDAS survey platforms are bottom-towed sleds capable of taking continuous multielectrode, resistivity measurements of the top few meters of seafloor while working in water depths exceeding 2000m.

The C-BASS weighs approximately 1ton and when compared to ReDAS, is a more fully instrumented platform incorporating a sub-bottom profiler, lights and a video camera, a CTD and a mini-CPT (Cone Penetrometer). ReDAS is primarily a resistivity data collection system, and is smaller and lighter than the C-BASS, weighing approximately 1/2ton. Both are easily deployed from survey-class vessels using standard "deep-tow" oceanographic winches and A-frames.

With regard to their resistivity measurement systems, though different in detail, C-BASS and ReDAS have very similar performance characteristics. This is due largely the fact that both systems were targeted at the telecommunications industry and were therefore tuned to requirements of the cable burial assessment (BAS) surveys.

Towed Direct Current (TDC) Method.

Both C-BASS and ReDAS can be considered marine Towed Direct Current systems and are treated the same for purposes of this discussion-in the details of the systems lie subtle differences.

Land-based towed array resistivity systems have been available for some time. However, the performance of these land-based systems is often quite poor, with the data quality being limited due to inadequate coupling of the electrodes to the ground.
Seeing Through Crude Oil- Results from Demonstrator
Authors: Hother John A. , Cockshott Robert A.
Published: October 2008

Results from a development model downhole video imager operating in crude oil are presented. Pictures of representative items captured at the video output show that the system provides high quality images of objects immersed in crude oil.

Introduction

Proneta has identified, and patented, a way to see through crude oil, which will have a range of applications in the oil and gas industry. The first application we have explored is a new form of downhole video that requires no preparation of the well, saving time and cost in interventions. The previous paper SPE 71465 [1] reported the results of the successful feasibility study. This paper presents the results from the demonstrator, the first phase of the current operator-sponsored Joint Industry Project.

Demonstrator imager

The demonstrator tool comprises a self-contained imaging and illumination system in a cylindrical housing, which is sealed to withstand immersion in crude oil. Two versions were assembled and tested: one downwards-looking (figure 1) and the other sideways-looking (figure 2). While not engineered to withstand full down-hole conditions, both configurations are representative of practical tools and all the necessary optics and electronics have been accommodated within the space constraints of a deployable system.

Test set-up

Crude oil was placed in a steel tube large enough to contain the imager and target objects. The imager was mounted on a moveable frame above the tube, and could be lowered in and out of the oil and moved sideways in two axes. Figure 3 shows the moveable frame and the imager in the oil-filled tube.

Crude oil samples were obtained from various North Sea fields, including Scott (Amerada Hess), Fulmar (Shell) and Banff (Conoco), and a pumping system allowed the tube to be filled and drained during the tests. Water droplets and gas bubbles could also be introduced into the oil to investigate imaging through water and gas.

The output from the tool was connected to an image capture system, allowing video and still pictures to be displayed and stored. All images presented in this paper are stills taken from the imager's video output.
Osprey Project: Design and Installation of a Novel Platform in Cook Inlet, Alaska
Authors: Visser Robert C. , Carlson Gary E.
Published: October 2008

The paper describes the design, fabrication and installation of a novel self-erecting platform in Cook Inlet, Alaska. The platform project was completed by Forest Oil Corporation at a fraction of the cost of a conventional platform, thereby allowing exploration and subsequent development of a hitherto noncommercial oil field discovery dating back to 1969. This was accomplished despite the fact that Cook Inlet is one of the most inhospitable offshore areas in the world; there are thirtyfoot tides, moving ice floes in the winter and there are no derrick barges. The platform was assembled in a floating floatover operation in a deep-water bay in lower Cook Inlet. The assembled platform, supported on a barge, was towed to location in upper Cook Inlet and held in place at high tide with several tugs. As the tide ran out the legs reached bottom and the barge was removed. Foundation piles were driven using the pre-installed platform cranes.

Introduction

The Redoubt Shoal field in Cook Inlet, Alaska, see Figures 1 and 2, was discovered by Amoco (then PanAm) in 1969, but was not deemed commercial at the time. Forest Oil Corporation (then Forcenergy) took over the acreage in 1996 and, following a 3D seismic survey, concluded that the field could be commercial. To confirm this, however, required the drilling of at least two and possibly four appraisal wells.

Confirming the commerciality of an offshore prospect is usually done by drilling one or more expendable appraisal wells with a mobile drilling unit. For remote Cook Inlet this method is cost prohibitive, because the equipment has to be mobilized from out-of-state and a single appraisal well was estimated to cost some $25 to 30 million in 1997. Installing a platform in Cook Inlet the "conventional" way is also cost prohibitive, because there is no longer any heavy lifting equipment available on the West Coast and such a platform was estimated to cost $ 60 to 80 million.

As an alternative Forest decided to investigate the possibility of installing an "exploratory" drilling structure. Requirements for a minimum structure were:capability to support a 20,000-foot modular drilling rig,installation without heavy lifting equipment,feasibility to be converted into a permanent platform,easy removal in case the prospect did not pan out, andrelocatable to another Cook Inlet location.

A number of alternative platform concepts were developed by Redondo Beach, California consultant Belmar Engineering and further investigated for feasibility by Brown & Root in Houston. The selected concept requires no heavy lifting equipment and uses the tide to install the platform. To keep costs down, the platform, which was named Osprey, is located in 45 feet MLLW about two miles from shore rather than in much deeper water, four miles from shore, where the Redoubt Shoal field is located. The lower platform and future pipeline costs offset the increased extended reach drilling costs.
Synthetic Mooring Lines for Depths to 3000 Meters
Authors: Davies Peter , François Michel , Grosjean Francois , Baron Patrice , Salomon Karine , Trassoudaine Damien
Published: October 2008

This paper presents a study of the use of synthetic fibre mooring lines for deep-sea applications. Three materials are considered: polyester, aramid and HMPE. First, results from a test program completed recently are described. These tests on full size ropes, which include novel extensometric methods based on image analysis, have enabled the influence of mean load, load range and loading frequency on stiffness to be determined for the three materials. Ropes up to 750 tons MBL (minimum break load) have been tested. A comprehensive data set of this type has not been available previously. These data are then used in mooring system analyses, to evaluate a number of design cases for the station keeping of exploration and production platforms. This has allowed a better understanding of the domains of application of these different materials and of related issues for design. Materials research needs have also been clarified. The minimum tension criterion for HMPE and aramid fibre ropes is shown to be one of the critical technical parameters that should be further investigated in order to extend the further application of these materials for taut mooring systems design. Attention should also be given to fatigue analysis for the aramid and HMPE lines.

Introduction

As water depth increases, synthetic fibre ropes become increasingly attractive candidates for station keeping. In spite of some initial difficulties with aramid ropes 20 years ago1, over the last five years polyester has become an accepted alternative to steel for this application. The extensive studies and pioneering applications of Petrobras have led to increased confidence 2–4 and this is the preferred option for depths down to 1500 meters. However, with the numerous discoveries of large reserves in deeper water the question of whether polyester ropes can be used at all depths has been raised. Recently polyester was used in field trials down to 1900 meters depth5 but there are few guidelines concerning alternative materials. Chaplin & Del Vecchio compared polyester ropes to steel at depths of 500, 1000 and 2000 meters6. Cloos & Bosman compared nylon, polyester, and aramid ropes at depths to 3000 meters and concluded that there is a minimum depth for each material, that for aramid being 1000 meters7.

One aspect to be considered is the size and weight of large polyester ropes, and the implications for handling equipment and installation procedures. Figure 1 shows a comparison of rope sizes as a function of MBL (minimum break load). A 1000 ton MBL polyester rope has a diameter around 200 mm, and, with the several kilometer lengths to be deployed, this may exceed the storage capacity of anchor handling vessels. Figure 1 also shows that aramid and HMPE ropes are much closer to traditional steel wire in diameter. The equivalent polyester line will require two to three times the storage capacity that is needed for the other materials.
Economic Impact of Slimbore and Drill Through Xmas Trees on Deepwater Subsea Developments
Authors: Harrold David
Published: October 2008

This paper demonstrates cost savings that can be gained by selecting either slimbore or drill through Xmas Tree types to develop deepwater subsea fields. Field data and a computer model were used to quantify the CAPEX, OPEX and NPV life cycle cost savings these tree types can provide when compared to conventional vertical dual bore and horizontal Xmas Tree designs. The paper considers applications in depths from 2,000 to 10,000 feet.

Introduction

As operators embark upon development of deepwater subsea fields, long duration drilling, completion and workover cycles are encountered. The CAPEX and OPEX expended on these fields is largely governed by the cost to charter drilling rigs as opposed to the cost of the subsea hardware itself. However, the Xmas Tree type selected does have a major influence upon drilling, completion and workover durations and drilling rig selection. It is therefore imperative that the most suitable Xmas Tree is selected for any given application to minimize installation and workover durations whilst maximizing use of lower cost drilling and completion rigs.

Slimbore and drill through Xmas Trees were compared against standard fullbore vertical and horizontal Xmas Trees currently being installed in deep water. This paper is limited to comparing CAPEX and OPEX variances between the systems. Other technical merits or the relative risks associated with each system are not addressed or discussed. The ability of slimbore systems to utilize lower cost MSV vessels for installation and workover activities is examined and discussed. Time estimates and associated costs are presented for installation, tubing access workover, tubing retrieval workover, tree retrieval, well sidetrack and decompletion for each Xmas Tree. These costs were used to generate a financial model to compare the NPV life cycle costs associated with each system.

This paper is written assuming that readers have a fundamental understanding of subsea well completion operations and associated Xmas Tree hardware.

Xmas Tree Definitions

A brief description of each Xmas Tree type compared in this study is provided below. All Xmas Tree types are guidelineless (GLL) configurations, which are either currently in use or are being proposed for use in deep water field developments. The associated installation and intervention tools, which are used with each system, are also described. To the knowledge of the author, no subsea wells have been completed at water depths exceeding 7,500 feet and some technology development is ongoing to extend well completions to ultra deepwater. This fact will also impact Xmas Tree selection criteria, at least in the near term.

Conventional Dual Bore Vertical Tree (CXT).

The CXT is a dual bore configuration with an ROV installed, pressure containing tree cap. The tubing hanger is an 18-3/4" full bore design that is installed directly to the wellhead. The tubing hanger contains a hydraulically operated valve to provide annulus isolation.
An Earthquake/Wave Instrumentation System for Offshore Platforms
Authors: Titlow Joseph D.
Published: October 2008

The dynamic response of offshore drilling platforms during earthquakes and heavy sea conditions becomes increasingly important as water depth increases. Predicting the structural response of a platform depends upon the characteristics of the excitation and the dynamic properties of the platform. Recorded data on the behavior of full scale structuresduring earthquakes and heavy sea conditions is scarce. However, analytical methods have been developed recently which can be used to silll1late the dynamic response of deep water platforms. This paper describes an experimental program whose major objectives are (a) collection of data describing the characteristics of earthquake and wave excitations and the resulting structural response and (b) validation of analytical methods for predicting the dynamic response of platforms.

The Earthquake/Wave Instrumentation System was designed and installed on Platform Hope off carpinteria, California. The system measures and records accelerations, wave height profiles, and the accelerations of the platform during these events. This paper describes the innovations in the system that were required to meet the concepts and objectives of the experimental program.

Early results from operation of the system are reported. This includes analysis of ambient vibration tests which yield data on the fundamental natural frequency of the platform. Wave data from a moderately large storm is reported.

Basic System Concepts

There are three basic concepts which led to the development of the Earthquake/Wave Instrumentation System:the need for design tools which would provide better estimates of the dynamic behavior of platforms during earthquakesand heavy sea conditions,the need for strong-motion instrumentation on an offshore platform to supplement the onshore network, andthe need to delay large data handling expenditures until the value of the data could be determined.

These concepts formed the guidelines for decisions on the eventual system design and hardware.

Dynamic Behavior of Platforms

Offshore platforms, whose heights are less than 300 feet, can usually be designed using static methods only. These platforms exhibit essentially static behavior, since their natural frequencies are sufficiently separated from the frequency band associated with high-density wave energy. Platforms can be economically designed in the 300 foot to 600 foot range that are relatively stiff and have adequate frequency separation. However, above 600 feet the lowest frequencies approach the frequency band of maximum wave energy. This implies the structure will exhibit dynamic behavior and that it should be designed using methods which considers its dynamic properties and response characteristics. All deep water platforms in areas of high earthquake activity should be designed using dynamic methods.
Design of Piled Breakwater Structure for New Port of Manfredonia,Italy
Authors: Toppler J.F. , Harris Frederic R. , Maaten R.
Published: October 2008

This paper discusses the structural design of a breakwater ut1lizing steel bearing piles, concrete deck and concrete front wall.

To substantiate the design criteria, extensive model testing was performed with irregular waves simulating prototype wave energy spector. From the test it appeared that total forces over a limited length of breakwater, due to breaking waves, could be higher than those of the preliminary calculations based on theory. However, for a 100 meter long rigid "unit of breakwater, a reduction of at least 20% in the total forces due to spreading in time of local peak forces, was obtained from 3-dimensional tests. The influence of structural response was studied with the aid of an electronic analogue of the linear mass sprine system.

The model test showed that the configuration of the sea bottom, hence the width of scour protection affects the wave pressures on the breakwater. The experiments showed that this also holds for the overtopping rates, measured with two parapet shapes.

The resulting design showed that utilizing a batter pile type structure solution can be successfully employed as a breakwater construct ion in relatively deep water, where the conventional types of construction, due to the poor soils condition, would have been uneconomical.

INTRODUCTION

The township of Manfredonia is located on the Adriatic coast of Italy, north of Bari. '.the existing port of Manfredonia has very limited waterdepth. As a result of the new industrial expansion in the area, it was decided that the port facilities should be extended to be able to receive vessels up to 25,000 DWT carrying general cargo, bulk cargo and petroleum products. For ships of this size a minimum water depth of 11 m is required. Since the existing port could not be extended to accommodate these vessels due to the limited water depth available, the new port had to be located approximately 2 km offshore.

Due to the type of cargo to be handled, the port had to be protected from the seas. Detailed investigation of the sea and meteorological conditions was carried out to establish the extent of the protection required and the configuration of the new port. The requirements for initial throughputs dictated that the first phase of the development shallhave five berths. Allowance was made for construction of additional berths in the future.

In this paper no attempt was made to give a detailed account of the studies carried out and how the final configuration was established. A detailed description of the design -of the breakwater with special emphasis on the model testing, however., was presented.

GENERAL BACKGROUND

At the commencement of the preliminary engineering, since no information was available on the existing soils condition a, the study of the breakwater was concentrated on the use of conventional type of construction.
Towed Vehicle for Constant Depth and Bottom Contouring Operations
Authors: Conti Ugo , Wilde Pat , Richards Tommy L.
Published: October 2008

A towed vehicle capable of constant depth operation and bottom contouring has been designed and built for'pol1uiion monitoring studies in estuarine and marine environments. The principal characteristics are:Length.... ........54 inchesWing Span .........39 inchesBody Diameter......9 inchesTowing Speed.......1-4knotsOperation Depth ... Surface to 100 feetOperating Modes ... Bottom Contouring Constant DepthBottom Contouring..10 to 30 feet above bottomWeight in Air......110 poundsBuoyancy.............6 poundTowing Cable Type...1/4 inch polypropylene ropeTowing Cable Length ... 100 - 300 feet

The basic configuration of the vehicle is that of an airplane with fixed forward wings and rear movable elevators. The elevators can assume two positions that correspond to (1) diving and (2) surfacing. The distance from the bottom is measured with an echo sounder and the depth with a pressure gage. The control system is of the, open loop type with a yes - no mode of operation. The most interesting characteristics found in the preliminary study and tests with a full size wooden model were that (1) the lift to drag ratio is relatively independent of the velocity for a constant elevator setting and (2) the response to a weaving force of 10 pounds with a period of × seconds is a displacement from the line of motion of approximately × feet.

Sea trials made in the San Francisco Bay showed that without automatic controls the vehicle reached a certain depth in about 20 seconds and maintained this depth within ± 6 inches. In the bottom contouring mode the vehicle followed the bottom with oscillations contained within 4 - 5 feet. In the constant depth mode, depth was maintained with oscillation contained within 5 - 5 feet.

INTRODUCTION

The most common systems used for gathering environmental data in marine waters can be grouped in two general cateogries.On station measurements or water sampling along the water column.Underway measurements using a submerged instrument housing or a submerged pump and inboard instrumentation.

Our particular problem was to measure a large number of environmental parameters in estuarine and coastal waters for pollution assessment. In this particular environment, because of the varying of the physical condition (currents, eddies, long shore drift, etc.) it is difficult to establish a clear picture of the distribution and concentration of pollutants unless a great amount of data is gathered in a relatively short time.

In designing an instrumentation system adequate for this problem, we also stressed low cost and simplicity of operation.

We chose to use a towed underwater vehicle housing the sensors, the data recording system and all the necessary power supplies, and capable of maintaining either a constant depth or a constant distance above the bottom, because a large number of continuously monitoring fixed stations is both very expensive and impractical in a marine environment.
The Influence Of Environment Condition On The Design Of Cathodic Protection Systems For Marine Structure
Authors: Davis Jack G. , Doremus G.L. , Graham F. Wayne
Published: October 2008

Environmental conditions should and definitely do influence the design of cathodic protection systems for corrosion mitigation on marine structures in all areas of the world. Selection of components of the corrosion mitigation systems are influenced by environmental conditions from both an electrochemical and mechanical standpoint.

Corrosion rates on metals are influenced by their environments, and there is quite often a definite relationship between the corrosion rate and the protective current density required to prevent corrosion.

A cathodic protection system designed for an offshore platform or drilling rig in the Gulf of Mexico may not operate with the desired results in the North Sea area. A cathodic protection system designed for corrosion prevention on a structure in straight sea water would not perform satisfactorily for the same structure in brackish or polluted waters.

Environmental conditions should and definitely do have an influence on the corrosion rates of submerged steel and the design of cathodic protection systems for corrosion mitigation on marine structures. In orderfor a cathodic protection system to perform properly and thus prevent corrosion, the environment in which the system must operate must be taken into account as a primary consideration.

There are two general types of cathodic protection systems: galvanic anode systems, employing sacrificial aluminum, zinc or magnesium anodes; and impressed current systems, employing rectifiers and semi-inert anodes. The selection of the type of cathodic protection system depends largely on the environment and its overall effect on the structure to be protected and on the protective system.

The effects of environment will be handled in two broad classifications, electrochemical and mechanical, and they will both be related in this discussion to the natural sea water offshore in the Gulf of Mexico as an average or "norm" for environmental conditions. It is logical to select the Gulf as an average of environments since it contains more offshore platforms and other related marine facilities than any other body of water in the world. It follows that experience withcorrosion and cathodic protection on steel structures in the Gulf is very extensive.

For steel structures in natural sea water there is an approximate equality between the corrosion rate, expressed in mils per year (mpy) and the amount of cathodic protection current (direct current), expressed in milli per sq. ft. of submerged steel area, required to prevent corrosion. In Gulf of Mexico water the value is 5, i.e., the corrosion rate on a continuously submerged steel structure is approximately 5 mpy (.005 inches year) and the cathodic protection current density for attainment of a minimum protective to-water potential indicative of complete corrosion control is 5 milliamperes anodic per sq. ft. of submerged steel area.
Simulation of Contaminants in Bays - Application to San Francisco Bay Complex
Authors: Theodore Louis
Published: October 2008

This is the first in a projected series of papers concerned with the development of a mathematical model to simulate the behavior of' a contaminant in a series of' bays. Although this general problem traditionally falls within the domain of the sanitary engineer, chemical engineering principles and techniques were successfully applied in this research effort. The contaminant-bay system is represented by the conceptually similar combination of a reactant in a series of continuously stirred tank reactors (CSTR).

Specifically, the model incorporates forward feed as well as bidirectional interchange (backmixing), recycle, first-order reaction and independent auxiliary inputs to each reactor. Although the analysis is presented for three reactors, an extension to a larger system is easily accomplished.

Analytical solutions are obtained for diverse variable feed concentration. An analog computer approach is also included. In addition, a general digital computer program is developed which uses the Runge-Kutta numerical integration technique to solve the general set of equations dictated by the model under various conditions. System conditions include time variable flow rate, feed concentration and reactor volume, auxiliary inputs and reaction rates.

After appropriate representation of the required parameters, the model is applied to the San Francisco Bay complex, and the resultant equations are solved using the general digital program. Tidal effects are simulated by using bidirectional feed interchange. The calculated results predicted daily concentration profiles in qualitative agreement with what one would expect. The monthly concentration profiles generated compared favorably with existing experimental data.

The results of this study suggest that modelling techniques may prove a valuable and effective tool in simulating other water contaminated and air-polluted systems.

Introduction

The problem of water pollution has demanded increasing attention in recent years. The challenge of' treating water contaminated with industrial and municipal wastes and the associated problem of treating wastes before they are deposited in waterways has not eceived the same attention by the engineering profession as other technological problems. The sanitary engineer has been traditionally concerned with this subject. The chemical engineer, aided by his background and training in reaction kinetics, unit operations and transport processes, has also contributed to the solution of this problem in recent years. Some of the research effort by the chemical engineer has been directed to the general area of mathematically describing the concentration and flow pattern of contaminants in bodies of water.

The purpose of this study is to apply chemical engineering principles and techniques to obtain a mathematical model describing the concentration and flow behavior of contaminants in a series of bays.
Brazilian Petroleum Exploration and Production: From Monopoly to Free Market
Authors: de Luca João Carlos
Published: October 2008

Four important phases are identified in the evolution of the Oil industry in Brazil.First phase: from the beginning of the industry up to the creation of the National Petroleum Council (CNP), in 1938.2. Second phase: from 1938 to 1953. The activities, exclusively onshore, were carried out by CNP, until the creation of PETROBRAS and the concept of the state monopoly.Third phase: from 1953 to 1998. Great development of the industry, supported by the monopoly, held by PETROBRAS. This phase shows two great E&P cycles: an onshore cycle, from 1953 to 1968, and a predominantly offshore cycle. This cycle is marked by great challenges and technological achievements, with the exploration activities in the Campos Basin progressing into even deeper waters as a consequence of the successive discoveries of large fields and substantial increments in the proven reserves, which in this phase reached 9 billion barrels and the production of 1 million BOPD.Fourth (current) phase: Began with the publication of Law 9.478 in August 1997, which eased the monopoly, opening the market to competitiveness and created the National Petroleum Agency (ANP). The private investors answered immediately and, after 4 successful bidding rounds, 38 new concessionaries are active in the Brazilian sedimentary basins. As a result, it is expected the discovery of part of the 25 billion oil barrels potential to even out the R/P ratio, unbalanced by a vigorous production growth which now reaches 1,5 MMBOPD, on the way to the country's self-sufficiency by 2005. The evolution of the E&P segment in this new phase has the strong effect of increasing the local industry of goods & services with the local generation of value, employment and tax profit. Its economic importance may be gauged by its direct contribution to the Gross Domestic Product (GDP) growth.

Introduction

The first initiative to find petroleum in Brazil dates back to 1897, when the farmer/landowner Eugênio Ferreira Camargo, after observing an oil seep on an area where he had an old concession for the exploration of coal, drilled the first well in Bofete, state of São Paulo. The well was drilled to a depth of 488 meters and yielded but two barrels of oil. With such a result and the high costs, the activities were discontinued. In 1908, I.C. White, an American geologist contracted by the Brazilian Government to assess the hydrocarbon potential of the Southern states, presented an unfavorable diagnostic due to the abundance of igneous rock.

More serious endeavors on the part of Federal Government explore and produce petroleum in Brazil, in spite of little surface evidence of oil, ocurred as of the First World War (1914-18), with the creation of the Brazilian Geologic and Mineral Service (SGMB), of the Ministry of Agriculture.
Creating a Sustainable E&P Business in Brazil
Authors: Haney John , Koot Michiel
Published: October 2008

The exploration and production business has many stakeholders, including government, investors and contractors. There is a shared interest in generating maximum value from the oil and gas resources in the ground, and then findig a fair allocation of this value. The question that will be addressed in this paper is 'how do we create a viable and sustainable upstream industry in Brazil' that will achieve these aims? It is clear that is only possible with full participation and cooperation of all parties involved.

Introduction - What is at stake?

The Brazilian Government took the decision in 1996 to open the upstream sector to foreign investors in order to reduce oil imports, attract essential Direct Foreign Investment, and ensure performance through competiton.

Foreign investors (International Oil COmpanies) have responded by concluding partnership agreements with Petrobras in the initial phase and thereafter acquiring exploration acreage in the four bid rounds to date. Investments to date by these new players exceeds a billion US$ in exploration alone, with further invesments committed. These investments were being made based against the background of perceived high prospectivity of the acreage, and a belief that Government will remain committed to creating a viable business environment.

Local manufacturing and service companies see it as an opportunity to diversity their client base and grow their business. Other stakeholders see the opening up of the industry as an opportunity that will bring employment, development of local infrastructure and tax revenues - wihtout adverse impact on the environment.

The key point here is that many parties share an interest in the development of oil and gas resources in the ground - and must work together to create the right conditions for investment.

Taking Stock

Having completed the first exploration period of the first vintage of exploration blocks since the opening up of industry and nearing the end of two year Round 0 extensions, it is a good time to take stock of developments and achievements. Each investor does this regularly to see how actual performance compares to their expectations at the outset.

There is no doubt that the opening up of the upstream sector was successful. While Petrobras remains by far the largest player we now have more than 35 investor companies active. The Brazillian Petroleum Agency (ANP) has established itself as an effective regulator. Since its inception in 1997 it has made much progress in creating a regulatory framework and has received much credit for the transparent manner in which it has conducted its bid rounds.

Since 1998 some 320,000 km 2D and 120,000 km2 3D seismic has been acquired and evaluated and some 200 offshore exploration wells have been drilled including 45 by companies other than Petrobras.

However, the offshore exploration results since the opening of the sector have had mixed results. Some 110 technical discoveries have been reported but most are believed to be small to modest size accumulations of generally low gravity crude, or gas.
Canyon Express Subsea Multiphase Flow Metering System: Principles and Experience
Authors: Wallace Bryan K. , Gudimetla Ravi , Nelson Stuart G. , Hassold Thomas A.
Published: October 2008

As Canyon Express is a multi-field, multi-operator, deepwater subsea, gas development flowing into a common transport system, relatively accurate and reliable measurement of the produced fluids is essential to allocate hydrocarbon gas volumes per field and to estimate system water production. Thus, the metering principles and limitations must be understood to ensure that volumes are being calculated as accurate as possible. This paper describes the application, calibration testing, deepwater marinization program, and subsequent implementation of the subsea multiphase flowmeters used for the Canyon Express development in the Gulf of Mexico. This includes description of the meter theory, environmental condition development, and calibration. The overall objective of the metering will be discussed along with how the limitations of the meter affect the computation of the flow rates for the different phases of the produced fluid and the interrelationship of the engineering and testing results with the actual operation of the meter including the affect of liquid loading on the meter performance.

Successful demonstration and implementation of the subsea multiphase meter suitable for deepwater application allows for the measurement of hydrocarbon gas at the wellhead thus permitting the measured gas to flow into a common flowline to be commingled with other production streams for transportation to a host platform. This allows multiple marginal subsea fields, each with different owners, to be operated as a single economic development while maintaining acceptable gas measurement for allocation of hydrocarbon gas volumes. The Canyon Express team also utilized its meter development experience in managing the development of API Recommended Practice RP85 on "Subsea Wet Gas Meter Allocation Measurement".

Introduction

Canyon Express is a deepwater Gulf of Mexico (6450' to 7210'), multi-company (TotalFinaElf, BP, Marathon Oil, Pioneer Natural Resources, and Nippon Oil), ten (10) well, subsea completion, 500 MMSCFD natural gas gathering system with dual, common 12" flow lines to surface processing facilities at MP261. The operational and mechanical challenges for all related subsea facilities is significant as the 7210 foot water depth, at Camden Hills, represents a world record for subsea hydrocarbon production.

The initial (maximum) gas flow rates (per well) range from30-65 MMSCFD flowing at about 4200 psi (downstream of the choke) with an estimated condensate production up to 2.0 barrels/MMSCF. Initially, the water production expected is dry to low (less than 1 bbl/MMSCF) but is predicted to increase to 500 bbls for some wells later in field operations. The presence of the liquid phase in the predominantly gas production fluid must be considered when evaluating options for the measurement of the gas and liquid flow rates per well.