bluuebunny/crossref_metadata_2025 huggingface dataset:
Safety Performance of the Global E&P Industry 2001
Authors: Smith Don
Published: October 2008

Since 1985 the International Association of Oil and Gasb Producersa (OGP) has been collecting, analysing and reporting safety performance data on behalf of the global E&P industry. For 2001, OGP received almost 2,000 million workhours of E&P safety performance data, submitted by 41 companies, from their operations in 73 countries.

The paper presents the results from the analysis of the 2001 dataset. The 2001 statistics are compared to those of the proceeding 10 year period.

Analysis of the data shows that over the period 1991-2001 the industry has achieved a considerable improvement in its Lost Time Injury Frequency (LTIF), however little improvement is seen in Fatal Accident Rate (FAR) or Total Recordable Incident Rate (TRIR). For 2001, all these high level indicators were reported at their lowest values on record. In common with previous years, the most common types of incident leading to fatalities were vehicle related incidents, and persons being struck by moving or falling objects.

Introduction

The International Association of Oil and Gas Producers (OGP) has, since 1985, been collecting and reporting data relating to the safety performance of the global upstream oil and gas industry. This it has done through a series of annual publications, the latest of which is 'Safety Performance of the Global E&P Industry' [1]. These reports serve a range of purposes. Firstly, they present to the widest audience possible how the industry has performed, year on year, on a range of key safety measures. Secondly, it allows E&P organisations to benchmark their performance against that of their peers. Thirdly, it assists the industry to identify areas where it may need to concentrate effort. Most recently this has led to the formation of an OGP Land Transportation Task Force, the aim of which is to identify initiatives that may help to reduce the number of vehicle related incidents.

This paper presents the results of the analysis of the 2001 dataset. Industry recognised safety performance indicators are presented; Fatal Accident Rate (FAR), Fatal Incident Rate (FIR), Lost Time Injury Frequency (LTIF) and Total Recordable Incident Rate (TRIR). The 2001 data are compared with data from the proceeding 10 year period. The performance of both company and contractor personnel are compared, as are onshore and offshore performance indicators.

In addition to occupation injury data, the industry provides occupational illness data to OGP for analysis and reporting. However this paper is limited to a review of the occupational injury data. A review of the occupational illness data submitted to OGP for 2001 is available within a separate publication [2].

The paper provides a summary of the key features of 2001 safety performance statistics. The full analysis, including descriptions of each fatal incident and descriptions of significant incidents reported to OGP, is available within the annual report [1].
Mooring Design for Directional Spar Hull VIV
Authors: Magee Allan , Sablok Anil , Gebara Joe
Published: October 2008

Key issues for design of Spar mooring systems in the presence of VIV are discussed. The need to consider interactions between the directional effects of the Spar mooring and VIV response, together with the directional distribution of the loop current environment, is highlighted. For instance, the combination of current speed and varying sway natural periods for environment directions between and in-line with mooring groups give rise to variations in reduced velocity. Furthermore, the Spar response itself could be directional due in part to unsymmetric coverage of the VIV suppression strakes and other appurtenances located on the outside of the Spar. Directional stiffness and drag augmentation due to VIV may also affect maximum offsets and mooring line loads.

Two analysis methods are presented to determine governing mooring loads in the presence of Spar hull VIV. The first, called DRIVESIM, forces the motion of the hull in a pre - determined Figure-of-eight shape with given amplitude. Mooring loads consistent with measured drag loads are achieved by iteration on the effective hull drag coefficients. In the second method, called FORCE-IT, an applied force on the hull is used to achieve the required VIV amplitude, thereby allowing the mooring system non-linearities to achieve dynamic equilibrium. The second method shows a more realistic trajectory.

Description of Spar Hull and Mooring

Currently there are three Spar hull configurations that are installed or under design and construction: Classic Spar, Truss Spar and Cell Spar. The Classic and Truss Spar configurations are described in [1]. The Classic Spar has a circular cross section along its entire length. The Truss Spar hull consists of a hard tank, which has a circular cross section similar to Classic Spar, a truss structure with heave plates, and a soft tank which provides buoyancy during horizontal tow-out and holds fixed ballast in the in-place condition. The Cell Spar [2] has multiple circular cylinders joined together in contrast to a uniform circular section of the Classic and Truss Spar hull.

The Classic Spar hull and the hard tank of the Truss Spar hull are fitted with helical strakes to minimize hull VIV motion due to current. The Cell Spar similarly has strakes along its length. Due to construction and transportation considerations, the strakes on Truss Spars built to date do not provide full coverage, but are truncated or have reduced height along one side, as shown in Figure 1. This allows the hull to be built close to the ground and helps with transport and float-off from the transport vessel. It also eliminates the need to rotate the hull for adding strake sections after offloading from the Heavy Lift Vessel. Therefore, the strakes, on the Truss Spars to date do not provide full coverage. On the other hand, Classic Spars built to date were rotated after offloading and the strakes completed. Furthermore, there are holes in the strakes for the mooring chains to pass through that make the strakes un-symmetric for Truss Spars and even for Classic Spars.
Mitigating The Shallow Water Flow Risk At Mississippi Canyon 849: A Team Approach
Authors: Bruce Robert , McKeown James , Sargent Tim , Garrett Randal
Published: October 2008

Wells drilled near the Mars, Ursa and Europa Basins within the Mississippi Canyon Area, Gulf of Mexico, have experienced varying degrees of shallow water flow problems. Two wells drilled in Mississippi Canyon Block 849 (MC 849) penetrated overpressured sands within the shallow section causing catastrophic shallow water flow (SWF). Both wells were subsequently abandoned. A team of geohazards specialists, geologists, geophysicists and engineers worked together to identify and mitigate this SWF, and successfully drilled the exploration well (Slam Dunk) in MC 849.

Figure 1: Seafloor Rendering Showing Mississippi Canyon and MC Block 849.(AVAILABLE IN FULL PAPER)

Introduction

Mississippi Canyon Block 849 is located 145 miles southeast of New Orleans, LA, in about 3600 feet of water (Figure1). The Pliocene target of the two wells previously drilled on the block, the Norcen #1 (Norcen) and UPRC #2 (UPRC), is a well-defined series of vertically stacked amplitudes within a thickening wedge of seismic reflectors. These amplitudes are stratigraphically trapped on the flank of a large salt ridge, which separates the prospect from the Mars basin to the east. While attempting to drill this prospect both wells were lost due to SWF. A seafloor amplitude map generated from a subsequent TGS 3D geophysical survey over MC 849 showed areas of high seafloor amplitude around the Norcen and UPRC wells, which were interpreted to represent sand "mined" by the SWF. These areas are not visible in the original 3D seismic data acquired by Western Geophysical (Figures 2 and 3). The SWF encountered at the Norcen and UPRC wells was so severe that during the planning of the Figure 2: Seafloor Amplitudes Showing AmplitudeAnomalies at the Norcen and UPRC Wellsites Interpreted as â??Minedâ?? Sand from SWF. Figure 3: Seafloor Amplitude Map Prior to Drilling of Norcen and UPRC Wells.(AVAILABLE IN FULL IN PAPER) Slam Dunk prospect, it was debated if drilling a successful well was feasible.

SWF is defined as water or, sand and water flowing within and around the outside of structural well casing to the seafloor (Alberty and others, 1997). Isolating the specific stratigraphic interval where SWF was previously reported, and delineating the extent and distribution of the potential SWF sands were key factors in reducing the risk of encountering SWF at the Slam Dunk prospect.

Data Sets

The geohazards investigation was based on interpretation of reprocessed 3D seismic exploration data acquired by TGS. The 3D data cube contains 2-millisecond sample rate data to a record length of 3.5 seconds TWT below sea surface (BSS). The exploration data has been reprocessed with spectral whitening to enhance the higher frequencies in the tophole section. The dominant frequency of the 3D seismic data set is estimated to be about 50 Hz in the shallow section, which corresponds to a limit of separability of approximately 27.5 ft, assuming an average velocity of 5,500 ft/sec for the shallow sediments.
Role and Contribution of Pressure Regime Evaluation in Well Planning and Formation Evaluation Process, Zeit Bay Field - Gulf of Suez, Egypt
Authors: Selim Saber Moustafa , Badawy Bassem El-Sayed , Abdullah Khaled Mohamed , Khorshid Mohamed Ayman
Published: October 2008

The study aims to construct a simple and effective pressure regime model for Zeit Bay Field which can assist the well planner to predict the pore pressure for the upcoming wells to be drill in the field. It aims also to find out the relationship between the constructed pressure regime model and the geological setting of the field.

Introduction:

An adequate prediction of the Pore Pressure and better understanding for the Pressure Regime Model of any area are very important prior drilling any well. They can play a vital role at several stages of Exploration and Development Process. ? In Exploration Phase, they help in:-Providing calibration to Basin Modeling.Mapping Hydrocarbon Migration Pathways.Assessing the "Seal" effectiveness.Analyzing the "Trap" configuration and geometry for a Prospective Basin. In Development Phase, they help in:-Anticipating the location and potential magnitude of possible formation pressure problems.Providing suitable casing and mud program designs leading to Minimize Drilling Cost.Avoiding Environmental Pollution, Loss of Reserve, Loss of Human Life...etc). But it is worth mentioning that, it is very important to recognize and evaluate any changes in the Estimated Pore Pressure data during the drilling of a new well. The updated information can be used to implement the new well proposal.

General Outline about Zeit Bay Field:

Zeit Bay field is an oil field located in the southwestern offshore part of the Gulf of Suez, some 65 km north of Hurghada and 85 km south of Ras Gharib. The field extends to the onshore and is combined with General Petroleum Company's Bahar North -East field. (fig.1)

The field was discovered in June 1981 through the drilling of the Exploratory well "QQ 89-1" which was drilled in the crestal part of the structure and considered as gas producer well. In October, 1981 another well "QQ 89-2" was drilled 2 km south and down dip from well QQ 89-1. This well recorded the underlying oil-leg with an oil water contact at 4850 feet sub-sea.

The commercial field production has been started in December 1983 with average daily rate 20000 BOPD.

Structurally, Zeit Bay field is interpreted as a NW-SEbasement relief like anticline feature. This anticlinal feature is however, dissected into several fault block panels by two main fault systems. A set of NW-SE trending faults affecting the western and eastern flanks. Another set of W-NW/E-SE trending fault system affecting the northeast flank. Some of these faults die out at/ or near top Belayim except the extreme bounding faults. In addition to the northeast and southwest blocks there are a parallel narrow elongated rectangular high blocks down stepping away from the above triangular horst blocks. (fig.2)
How Water Depth Affects Extended Reach Drilling
Authors: Rocha Luiz Alberto S. , Andrade Renata , Soffried Klaus
Published: October 2008

Over the last years, the drilling of extended reach wells (ERW) has become almost common practice in the oil industry. Although it still poses many technical challenges, successful applications such as the ones at Witch Farm, UK or in the South China Sea spurred the interest in ERW by the operators. In parallel, with the push for even further lateral displacement of wells, another technology frontier emerged for drillers: Extended reach wells in deepwater.

The majority of the extended reach wells are drilled from onshore sites to reservoirs that are situated under sensible locations like preserved nature or urbanized areas. Extended reach wells drilled from fixed platform installations in shallow water usually are aimed to reach outer parts of reservoirs that otherwise could not be developed economically. In deepwater, ERW allows the use of dry completion platforms such as TLP or SPAR. It improves flow assurance and reduces the cost of the well and the future interventions.

The paper at hand gives an overview on the effects of water depth on extended reach drilling (ERD) and has been divided in two sections. The first section is aimed to provide a general overview and examine the direct impact of water depth and pressure gradients on great displacement wells. It presents a number of ideas and practices currently used by operators. It also discusses applied solutions obtained from the associated literature and from interviews with experts in several service companies. Among others, new technology related to hole cleaning, torque and drag reduction and ECD management are discussed.

The second section of this paper will look at possible solutions to the engineering challenges based on analytical methods. Tools such as rotary steerable technology, LWD, high torque drillpipe, non-rotating stabilizers and drillpipe protectors, hydraulic by pass subs and others are analyzed as part of an integrated planning approach. Several effects that different water depths scenarios have on ECD, torque, drag and formation pressure gradients are simulated, and discussed.

Introduction

It is common to think about ERW as directional wells that have the displacements much higher than the total vertical depth (TVD). It is also acceptable to use the ratio between horizontal displacement and TVD (DTVD) to classify directional wells. According to this relation, wells could be classified as follows
1500 hp AC Drive Motor Design for Oil Field Drilling Operations
Authors: Al Akayshee Qasim , Williams Kevin
Published: October 2008

The paper describes the design and testing of an induction motor. The design for this machine, which is to produce 1500 hp continuously, was first calculated using a conventional equivalent circuit with analytically derived parameters. 2D finite element analysis was then used to obtain an optimum result. A thermal lumped circuit program was also employed to predict the temperature of the winding. Experimental results are given to validate the work.

Introduction

The AC drive system has been designed to meet the rugged demands of marine and drilling applications, the system replaces an earlier DC machine drive and employs the OEMV3000 [1] - Active Energy Management Drive to give virtually zero harmonic distortion of supply current and unity power factor.

Many things can affect the smooth running of a process and produce adverse process conditions. In the past, the self-protection philosophy of variable speed drives resulted in drive tripping or shutting down. The level of intelligence and protection in the OEMV3000 means that these self-protecting trips are no longer necessary. This new drive system (Fig. 1.) can take intelligent action in the event of adverse process conditions, resulting in higher plant availability and warning of process problems before they occur.

Motor Construction

The machine has 6 poles. The double layer 10/12 corded stator winding is accommodated in 72 slots. The stator laminations are made from Losil material. Class H inverter grade wire is used so as to withstand the sharp impulse repetitive waveforms produced from the switching process at high frequencies. The rotor has 84 slots and carries copper bars.

Fig. 1 The AC drive system(AVAIALBLE IN FULL PAPER)

Design Strategy.

This depends on the iteration between the electromagnetic equivalent circuit algorithm and the lumped circuit thermal design algorithm. These two packages are based on analytical methods and enable many design ideas to be examined in a short period of time. The aim is to try to optimise the overall design. The electromagnetic and thermal designs need to be considered at the same time because they are interdependent; the losses being dependent upon the temperature and the temperature on the losses.

Electromagnetic finite element analysis is used to fine-tune the design. It enables the precise flux distribution and saturation levels to be determined and improves the accuracy of the predicted performance. A photograph of this new motor is shown in Fig.2.
Otter: The World's Longest Subsea Tie-Back With Dual ESP
Authors: Horn Mark , Coudeville Frederic , Bespalov Eugene , Butcher Howard
Published: October 2008

The Otter field in the Northern North Sea has been developed using three subsea production wells each equipped with dual electric submersible pumps (ESP). Dual ESP were selected as they will maximise well availability and minimise operating costs associated with workovers. The field is located 21 kilometres from the host platform, making this development the longest subsea tie-back with ESP completed to date.

The equipment selected for the ESP system is described, including downhole, subsea and the topsides equipment. A rigorous testing programme was performed to prove that over such a distance from the variable frequency drives ESP could be successfully operated, controlled and data received.

The experience gained during the development will serve as a guide to future long step-out or deep-water subsea developments by identifying critical components and the operational philosophy developed for the Otter field. Factors limiting the development of fields at greater step-out are discussed.

Conclusions can be drawn on the steps required to implement a successful development and some of the pit falls to be avoided.

Introduction

The Otter field lies in the Northern area of the Northern North Sea on the edge of the Viking Graben area (see Figure 1). The field is operated by TotalFinaElf exploration UK plc on behalf of the joint venture partners Dana Petroleum (E & P) Ltd, Esso Exploration and Production UK Ltd and Shell UK Ltd.

The field was discovered in 1978 by Phillips Petroleum, however the field remained undeveloped until 2002 due to the limited size of the discovery and technical challenges. Operatorship of the field was acquired by Fina Exploration in 1997 and at this time interest in developing the field was renewed. To prove reserves and well deliverability a delineation well, 210/15a-5, was drilled and tested in 1998. The results of this well were encouraging and a development screening study was launched. A further delineation well was drilled in 2000 to confirm a field extension to the North prior to the launch of the development project.

The hydrocarbon reserves in the Otter field are found in faulted compartments of the Middle Jurassic Brent sequence, with the top reservoir at around 2000m below sea-level. The reservoir has good porosity and excellent permeability, with horizontal wells able to produce in the range 15-20,000 bbl/d. The reservoir fluid was under saturated at initial conditions with a gas/oil ratio of 450 scf/bbl, and contains low levels (<0.3%mol) of carbon dioxide and traces of hydrogen sulphide. The reservoir was initially normally pressured, approximately 62 bar above the bubble point. Wells flow during initial stage of production, but require artificial lift once water cut increases or the pressure depletion occurs.

Development Strategy

The development consists of three production wells each equipped with dual ESP and two water injection wells to provide pressure support. A full description of the Otter development can be found in Ref 1.
Prediction of the long term behavior of synthetic mooring lines
Authors: Davies Peter , Chailleux Emmanuel , Bunsell Anthony , Grosjean Francois , Francois Michel
Published: October 2008

The stiffness and short term behavior of polyester mooring lines are now reasonably well understood and these materials are finding many applications offshore. Much less is known about the long term behavior of this and other synthetic materials (aramids, HMPE). This paper presents results from creep and cyclic loading tests on these three materials at different scales, from single fiber up to ropes. The behavior of aramid and polyester is compared with the predictions of a viscoelastic-viscoplastic model which includes bedding-in effects. For HMPE lines it is creep which dominates line design, and data are compared to an existing creep model. New material developments which significantly improve creep performance of HMPE-based ropes are presented.

Introduction

The last five years have seen much development of synthetic ropes for deep sea mooring lines. Polyester has been extensively used offshore Brazil 1. Other installations off West Africa, and more recently the first applications in the Gulf of Mexico, have confirmed the potential of this material.

Permanent moorings require a guaranteed lifetime of at least 20 years, so an in-depth understanding of the long term behavior of the polymer fibers which make up the synthetic components is essential. The loading types of interest are creep (long term constant load), recovery (response after unloading), and cyclic loading at periods in the range from 5 to 500 seconds.

The factors which determine the lifetime of a synthetic rope are the global response, the strain level achieved at a given time and its magnitude with respect to failure strain, and local response due to factors such as abrasion, fatigue, accidental damage and defects. This paper will concentrate on the global response, and the development of models which allow global strain to be determined at any time as a function of loading history will first be discussed. Some recent material improvements will then be presented. The paper concludes with some discussion of local failure mechanisms and work currently underway.

Materials

There are two materials currently attracting interest for deep sea mooring lines, polyester and HMPE (high modulus polyethylene). However, ropes based on several other fibers also offer attractive properties, including aramids (Kevlar, Twaron), improved polyesters (Pentex) and liquid crystal polymers such as Vectran and PBO. Although the latter are relatively expensive at present compared to polyester the material costs may only represent a small part of the overall costs to be considered in the installation and operation of a floating platform. It was therefore considered premature to exclude technically interesting fibers, and Table 1 shows the materials which have been examined in the current study.
Use of Enhanced ATS Pictures for Gulf-Storm Researches
Authors: Fujita T. Theodore , Tecson Jaime J.
Published: October 2008

Hurricanes cause severe damage along the Gulf Coast almost annually. Since two intense hurricanes, Camille and Celia, resulted in severe damage, it became necessary to predict possible damage based on satellite pictures long before ground-based radar is capable of detecting hurricane structure. Presented in this paper is an example of enhanced satellite picture and the extent of hurricane damage assessed by the damaging wind scale proposed by Fujita.

1. Introduction

Applications Technology Satellites (ATS) located 22,500 miles above the equator have been taking pictures of the earth at frequent intervals. Since the orbital period of ATS is selected to be the sidereal rotation period of the earth, it is feasible to monitor development of storms continuously during sun-lit hours. An operational satellite SMS/GOES to be launched late in 1973 will carry an infrared sensor, permitting us to monitor severe storms 24 hours a day.

To make the most use of satellite data, pictures can be enhanced so as to depict detailed structure of storms for their prediction and subsequent disaster preparedness.

It is the purpose of this paper to review potential values of geostationary satellite data and to present a method of storm damage assessment based on the F-scale damage categories.

2. Values Of Geostationary Satellites

In Monitoring Gulf Storms

ATS III, located above the equator south of the United States, is sending pictures back to the earth for every 10 to 30 minutes, depending upon storm situations. These pictures have been put together operationally into time-lapse movies by National Hurricane Center at Miami, National Severe Storms Forecast Center at Kansas City, and National Environmental Satellite Service at Suitland, Md. Basic research on the operational application of satellite data has been conducted by SMRP, Satellite and Micrometeorology Research Project, at the University of Chicago in an attempt to solve problems of storm identification and prediction.

Shown in Fig. 1 is a picture of hurricane Camille shortly before her landing near Gulfport, Miss., causing tremendous wind and water damage. As has been well known, the top of a hurricane is covered with a thick cirrus shield which often appears to be a white disc in satellite pictures. Taking place beneath this white disc are high winds and waves coupled with heavy precipitation, resulting sometimes in practically zero visibility.

Thanks for the development of geostationary satellites capable of looking down upon the earth to scan cloud patterns with 2.5-mile resolution at the sub point. We can now trace back all hurricanes to their spawning ground which may be in the Caribbean or the Atlantic or even in West America. The eggs of potential hurricanes can thus be monitored all-the-way to their hatching ground.
The Appraisal and Development Plan for the Heavy Oil Jubarte Field, Deepwater Campos Basin, Brazil
Authors: Bezerra Marcio  F.C. , Pedroso Carlos , Pinto Antonio C.C. , Bruhn Carlos H.L.
Published: October 2008

Heavy oil production from the deepwater Campos Basin, southeastern Brazil, has comprised a new challenge for Petrobras (Pedroso et al., 2003; Pinto et al., 2003a, 2003b; Bruhn et al., 2003). One of the most recent discoveries in the Campos Basin is the Jubarte oilfield, located off the Espirito Santo State, under water depths between 1,000 and 1,500 m, and containing reserves of about 600 million bbl of 17.1° API oil.

Jubarte field was discovered in January 2001, when a vertical well found 40 m of oil-saturated, Maastrichtian turbidite reservoirs underlain by a thick aquifer. The well was cased and tested, but the recorded PI showed to be insufficient to guarantee commercial oil production.

In order to investigate the actual production potential, the drilling and testing of a 1,076 m-long horizontal well was approved, based on the "Value of Information" approach. The horizontal well recorded a PI 12 times the PI of the vertical well; this proved that it would be possible to produce the Jubarte field heavy oil at commercial flow rates. The appraisal of the area was completed with the additional drilling of two wells. With the same approach, an Extended Well Test, with the horizontal well flowing to an FPSO, was proposed and started operation in October 2002. Again, the obtained production rate was better than the predicted, and the commerciality of the field was declared in December 2002. Based on well log data, core samples, seismic data and interpretation of the extended well test data, stratigraphic and structural analysis were performed, resulting in a complete 3D geological model. Multiphase flow studies and a full field flow model were built, which allowed the forecasting of the field behavior.

With a reliable flow model, supported by a complete uncertainty analysis, the development plan for the whole field was defined. To mitigate the production uncertainties, the first phase will consist of 4 wells only, with different lift systems, connected to a FPSO with a processing capacity of 60,000 bopd.

In this paper we describe the whole process of the discovery, test, appraisal and definition of the strategy to develop the Jubarte Field. Special emphasis is given on the technological challenges that must be overcome to make possible the development of the oil field containing the heaviest oil ever produced from the deepwater Campos Basin.

Introduction

Jubarte Field, discovered in January 2001, is located 77 km off the Espirito Santo State coast, southeastern Brazil, under water depths between 1,000 and 1,500 m (Fig. 1). It contains 17.1°API oil, with viscosity of 14.5 cP at the saturation pressure of 183.5 kgf/cm2. The dead oil viscosity at 20 °C is about 3,000 cP, being the most viscous oil at surface conditions ever produced in Brazil through a wet completion system.
A New Approach to High Accuracy Ranging with Microwaves
Authors: Ragan Lawrence
Published: October 2008

Describes the design, development, installation and operation of a microwave ranging system for use in offshore pipe laying operations. Discusses error causes and correction methods, system design and mechanical design. Maximum non-correctable error due to equipment variations is 0.25 meter. Analysis shows up to 1 meter error due to propagation effects.

1.0 Problem Definition

1.1 Offshore Pipe Locating

The equipment described here may have uses in other areas, but it was designed specifically for use in laying and servicing oil and gas pipelines on the ocean floor. These lines are used to gather and transport the products of offshore wells.

The pipe-laying operation is performed in several steps, as follows:An initial survey is made of the route to be followed. This includes study of other pipes, cables, etc., already in the area, as well as soundings to determine depths, measurements of currents, and in some cases inspection of certain areas by divers. An accurate route map is made; called a "preplot", showing where the pipe is to be laid.Where necessary, the ocean floor is smoothed by dragging, dredging or blasting.The pipe is welded together, wrapped at the joints, and laid on the ocean floor. This is done with a large barge which pulls tension on the pipe against anchors placed by tugboats. The barge has no propulsion system of its own.The position of the pipe is checked with a sonar by a survey vessel.The pipe is buried by another barge. This is done hydraulically, in most cases.

The entire operation is very expensive and down time is quite expensive as well. Hence, reliability and maintainability are very important.

Accuracy is required primarily to conserve pipe. Accurate positioning helps to conserve pipe in two ways. The most obvious, of course, is by laying it in a straight line. The other way is in preventing buckling. If the anchors begin to slip, the barge backs up, and the pipe may buckle. Accurate position measurement gives an early warning of, and evaluation of the extent of slippage. Repeatability is required to lay pipe on the prescribed course, to bury the pipe, and to locate it for later additions, service, or repairs.

Low frequency locating systems such as Loran and Decca not only fail to provide the required accuracy, but are virtually inoperable on a pipe-laying barge due to interference from the arc-welding and h.f. communication equipment.

1.2. Location by Triangulation

The approach taken then, is one of direct distance measurement using microwaves. The distance to two reference points is measured, and the vessel's location is then found by triangulation (fig. l.la). Extreme accuracy is needed when the subtended angle is quite small (fig. l.lb) or quite large (fig. l.lc) in order to accurately determine the vessel's position.

1.3 Previous Approach

Previous equipment designs to measure these distances compared the phase of the sinusoidal modulation waveforms of an outgoing and returning phase-modulated wave to determine the distance.
Planning and Design of Fixed Berth Structures For 300,000 to 500,000 DWT Tankers
Authors: Tappler J.F. , Weersma J.F.
Published: October 2008

The planning and design of berths for mammoth tankers completed during the past few years and now under construction, is reviewed. All these structures are of the fixed type and accommodate tankers larger than 300,000 DWT.

The range of ships to be accommodated predicates the number and spacing of the main structural components and influences the cost of the structure.

A tendency of increasing berthing energy capacity for a given size vessel is illustrated. The evaluation of mooring loads is commented on.

The cost of the structure as a proportion of the total cost of the installation has significantly changed for the recent projects, due to the increased loading rates and more extensive mechanical provisions.

INTRODUCTION

In the early sixties the first two facilities for tankers of 300,000 DWT were conceived. At that time the concept of transshipment terminals using very large vessels to shuttle between the Persian Gulf and the transshipment terminal was established. This concept set the stage for the development of a new generation of tankers, namely the mammoth tankers or as they are also known, the Bantry class tankers.

During the next few years the concept of transshipment was modified to include shipping directly to receiving ports. This in turn, prompted the construction of more of these vessels and the development of even larger tankers. In this paper reference is made to the planning and design of some of these facilities, starting with Bantry Bay and Kuwait.

No attempt was made to give a detailed description of any of the projects, because they have been described in technical publications or will be as soon as the construction is completed. An attempt was made however, to highlight aspects of the planning and design which require special attention.

Undoubtedly the design philosophy has changed somewhat since the first of these facilities were built. These changes were the result of the experience gained from the first projects and the data collected from investigations and tests. The two main design aspects are berthing energies and mooring loads, both of which need further study and experimentation. A brief summary of some of the approaches to establish berthing energy is included, while for mooring loads the necessity of model testing is advocated. Mention is also made of the high loading rates and the associated installations. The cost ratio between the main components of the structure and the mechanical installation is given, comparing the first projects against the recent installations. The basic layouts of several facilities which Harris planned and designed during the past years are used to illustrate how various solutions were found for facilities to serve 300,000 - 500,000 DWT tankers.

DEVELOPMENT OF TANKERS

The phenomenal increase of tanker size in the 19601 s required a complete reevaluation of the design of facilities to handle the new generation vessels. The largest tanker in service in 1960 was 100,000 DWT, in 1970, 326,000 DWT and in 1973 it will be 500,000 DWT.
Engineering Properties of Marine Sediments-Gulf of Paria, Trinidad, W. I.
Authors: Gershowitz Robert , Liao John
Published: October 2008

The engineering properties of high plasticity marine sediments in the Gulf of Paria were investigated for the design of a five mile long submarine pipeline and marine structure at the request of Texaco Trinidad, West Indies. The strength-depth relationships determined by using hand vane shear tester and laboratory tests performed on undisturbed samples indicated linear variation to a depth of approximately 80 feet. Thereafter, the rate of strength increase reduced resulting in almost constant shear strength at the maximum depth explored -- 212 feet below sea bottom in 90 feet of water. Design charts determining the anticipated settlement of the submarine pipelines and foundation pile capacities were developed.

INTRODUCTION

The construction of engineering works on the sea bed requires knowledge of the physical properties of the bottom sediments to varying depths, depending upon the type of facility contemplated. Certain types of facilities are involved only with the shallow deposits, other types of facilities with both shallow and deep deposits. This paper is involved with both shallow and deep strata - the shallow for a submarine pipeline and the deep for the foundations for a platform and an anchorage for a Single Point Mooring (SPM).

The accurate determination of the physical properties of each sediment stratum is essential to the development of a sound engineering design. The accuracy with which these determinations can be made is intimately related to the ability to either obtain undisturbed samp1e which can be tested, or to perform in-situ tests. The problem is further compounded when operations have to be performed in exposed sea locations. Several approaches to in-situ testing have been attempted with only limited degrees of success, and only in relatively shallow penetrations of the bottom. This approach, therefore, still remains in the research and development stage and is not suitable for consideration in a production type of project. The use of undisturbed sampling currently affords the best opportunity for a successful program at moderate cost.

This project required operations in 90 feet of water and utilized the cased boring techniques with almost continuous thin wall tube sampling. Shear testing was performed on site by means of a small vane shear tester and compared with the results of laboratory unconfined compression and triaxial shear tests. A design chart was developed to determine the estimated settlements of the submarine pipeline as a function of pipe diameter and specific gravity. Another chart was developed to establish the pile capacities in tension and compression.
Big bore, high flowrate, deep water gas wells for Ormen Lange
Authors: Hartmann Robin A. , Vikeså Gerd Olaug , Kjærnes Per A.
Published: October 2008

Ormen Lange is Norway's second largest gas field located at a water depth of about 1000 meters, see Figure 1. The field development plan calls for a subsea solution with templates, manifolds and pipelines to be installed approximately 120 kilometers from shore. The development operator for Ormen Lange is Norsk Hydro, while A/S Norske Shell will take over operatorship at the start of production in October 2007. In addition, A/S Norske Shell will, after approval of the field development plan, be responsible for subsurface development, including drilling of the development wells. Ormen Lange's highly prolific reservoir capacity, in terms of permeability, size and pressure, presented the opportunity to consider big bore, high flowrate wells during the initial design concept.

Figure 1. Ormen Lange development area. (Available in full paper)

This paper describes the process of the big bore well concept selection for the Ormen Lange field, adding value to project economics, but within the boundaries of reservoir uncertainties and risks associated with each concept considered.

Introduction

The Ormen Lange field has a gas volume in place of about 528 GSm3, from which 397 GSm3 is recoverable (P50). The gas reserves cover a geographical area of approximately 340 km2, and the field is approximately 40 km long and 8 - 10 km wide. Norsk Hydro discovered the field in 1997. Five exploration and appraisal wells have been drilled on Ormen Lange.

Reservoir targets and template locations

Based on the results of the appraisal campaign, indicating a possibility for reservoir compartmentalization with partial sealing faults, the spreading of reservoir targets was concluded as the optimum reservoir drainage strategy. The target locations, as well as the appraisal targets (excluding appraisal location 6305/1-1, which is located further to the north outside the depicted area), are shown in Figure 2. To accommodate the spreading of the targets, the subsea development calls for two templates in the main production area (templates A and B), with a mutual distance of about 3 km. In addition, two more future templates are included (templates C and D). The well step-outs result in six wells with step-outs of less than 1.5 km from templates A and B and the remaining 18 wells with stepouts of maximum 2.5 km. The base case is 24 wells. See Figure 3 for template locations and well trajectories.

Reservoir properties

The main production area of the Ormen Lange field is at a water depth of 850 meter TVDMSL, and the single reservoir at 2705 m TVDMSL. The reservoir pressure is 289 bar while the reservoir temperature is 96 degrees Celsius. The depth reference to initial reservoir condition is 2,913 m TVDMSL. The temperature at the seabed is -2 degrees Celsius. The net reservoir height is 37.5 meters with around 500 mDarcy permeability, 27% porosity. The gas condensate ratio is 10,600 Sm3/Sm3 while the water gas ratio is 2.89 10−6. The net gross ration is 0.92.
Ocean Disposal of Copper Mining TaiIings
Authors: Kuo Chin Y.
Published: October 2008

Ocean disposal of copper mining tailings through an outfall is proposed on the south coast of Puerto Rico.

If the tailings are discharged at a great depth well below the mixing zone and at the head of Cuchara Canyon, which has a steep bottom slope and is V-shaped, the tailing water and solids would not appear on the sea surface and in the coastal areas.

SCOPE OF THE PROBLEM

A massive increase in the already growing level of ocean dumping has been warned. More attention has been given to banning the dumping of specific materials and transporting them to designated safe sites8.

Copper mining in Puerto Rico has been a big political, economic and environmental controversy for a long time 6. Several studies were made for this mining project. The results of the study on the proposed ocean disposal of mining tailings are summarized herein. This study illustrates the selection of a suitable site for the dumping of mine tailings and perhaps solid wastes as well.

The companies plan to extract the ore from Rico Vivi and Tanama deposits (Pig. 1). One concentrator will be built. The concentrates will be pumped to a smelter and. the tailings will be piped through an outfall to the southern coast to a point about 2 mile.3 offshore from Punta Cuchara just west of Ponce.

The ecological problems raised by the conservationists are not included here. Two technical questions are discussed regarding the potential movement of the discharged tailings in the marine environment. These are analyzed based on the data gathered from the companies, marine geological surveys and physical oceanographic records. The questions are (1) would the tailings, which might carry contaminates, be washed back to the coast by surface or deep sea currents, and (2) would the tailing solids substantially build up a shallow water zone that stops the function of the outfall?

ANALYSIS

Potentially, the tailings would be composed of very fine crushed solid particles (approximately 60 percent by weight with a specific gravity of 2.8) and 40 percent fresh water. The slurry-like mixture has a specific gravity of 2.08. When the tailing is discharged through the outfall into the receiving ocean body, the jet of the solid-water mixture diffuses horizontally. The suspended particles generate a density current. The fresh water entrains the sea water and rises like a buoyant plume that mayor may not be submerged below the sea surface, depending on the discharge rate of the tailing and the density field of the ocean.

To estimate the maximum height that the tailing would rise (on the conservative side), the maximum height of the rise of the fresh water should be found since the solid particles are heavier than the fresh water. This calculation would predict the depth of the hazard zone if any contaminating materials were carried by the tailing.

Estimated fresh-water requirement for the tailing disposal is 3,150 gal/min.2 The proposed location of the outfall is at a depth of 800 ft. Using the formula proposed by Brooks3 based on the analysis given by Moton.
Importance of Mass Transport Complexes in the Quaternary Development of the Nile Fan, Egypt
Authors: Newton C.S. , Shipp R.C. , Mosher D.C. , Wach G.D.
Published: October 2008

Mass transport complexes (MTCs) within the Quaternary section of the ultra-deep water Nile Fan, offshore Egypt, form a significant portion of the Quaternary sedimentary section. This indicates the importance of mass-failure processes in deep water fan progradation. Regional mapping within the western platform of the Nile Fan reveals MTCs generally comprise 30%, but locally up to 94% of the Quaternary sedimentary column. Interpretation of the Quaternary section (upper 1 km of sediment) of a recently acquired, large, 3D seismic survey on the Nile Fan reveals the presence of five large mass transport complexes (MTCs) on the mid-slope of the western platform of the Nile Fan. These MTCs are on average 150 ms thick, but can obtain thicknesses of up to 357 ms. One of the MTCs is 175 km in length from the upper to the lower slope and comprises approximately 670 km3 of sediment.

Introduction

Slope failure deposits are common features of continental margins around the world1. Despite the fact that they are considered destructive sedimentary processes, their relevance to margin progradation is becoming increasingly recognized. Margin progradation is perhaps best studied in areas where, it is accelerated in high sedimentation rate environments, such as the deep water fan systems. The Nile Fan is the one of the largest deep water fans in the world. In ultra-deep water, the Quaternary section is in excess of 1 km thick. It is the objective of this study to investigate the architecture of the Quaternary section of the deep water Nile fan, and to understand the role of mass transport processes in the construction and progradation of the fan system.

Slope failure is generally recognized by identifying escarpments, unconformities, and sedimentary deposits with certain characteristics suggesting mass transport (e.g., hummocky surfaces and incoherent internal reflections). Without referring to a specific physical process or depositional style, these deposits are referred to as mass transport complexes (MTCs). Large mass transport complexes are considered to be those that are generally greater that 2500 km2 in area and up to several hundreds of metres thick.

The deep water continental slope environment has been studied for some time, but it is only recently that the oil and gas industry has become interested in these areas for their enormous hydrocarbon potential. This interest, combined with seismic imaging improvements and widespread availability of 3D seismic data, has resulted in large 3D seismic surveys of continental slope margins worldwide. From an industry perspective, research conducted using these datasets, has greatly improved understanding of turbidite channel and levee systems. Other important elements of deep water depositional system, such as the role and significance of MTCs, have been overlooked. A large 3D seismic data set has been acquired over the Nile Fan (Figure 1) and will provide the foundation for this investigation.