bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geology and Hydrocarbon Potential of Bombay Offshore Basin
Authors: Sahay B. 
Published: October 2008

ABSTRACT

DESCRIPTION :
The Western Continental Margin is a passive margin having six sedimentary basins namely Kutch, Saurashtra, Bombay Offshore, Konkan, Lakshadweep and Kerala. Out of the six basins Bombay Offshore is the biggest basin having an aerial extent of 1,20,000 Sq. Km. Bombay Offshore basin which is an intracratonic basin, is the southern extension of Cambay basin and encompasses the Gulf of Cambay and adjacent shelf part of the Arabian sea. It came into existence during Upper Cretaceous time as a result of faulting in the Deccan t['ap basement. This basin is divided into several tectonic units such as Cambay Gulf Shelf to the north followed to the south by Dahanu depression, Bombay Ratnagiri shelf occuyping central and southern part of the basin and Western clastic basin fringing Bombay Ratnagiri shelf.

RESULTS:
As a result of seismic surveys carried out five different reflectors have been met. They are H-1, H2, H-3, H-4 & H-5. Of these reflectors horizon-5 is confined only to the north and north Western region and probably marks the top of the basement. Geophysical surveys both reconnaissance, semi-detail or detailed carried out have helped in the delineation of big and small structures in the Bombay Offshore basin. The important structures delineated are Bombay High, Panna, Bassein, Dahanu, South Tapti, Heera, Ratna and other small structures indeed, area.
A full sedimentary section from Palaeocene to Recent of over 4 Km. resting on trappean basement has been met. In few places Pre-Cambrian basement instead of trappean basement also occurs. The oil and gas bearing horizons of Bombay Offshore basin, range in age from Middle Miocene to Early Eocene and are mostly wackstone/ mudstones. and chalky limestones.
Evaluation by drilling of important structures in Bombay Offshore Basin like Bombay High, Panna, Bassein, Heera, Ratna, South Tapti, etc., have resulted in the discovery of big and small oil and gas fields. Besides this oil and gas indications have also been met in several other structures, too.
The Bombay Offshore Basin has only Tertiary sediments with Eocene being absent in Bombay High. However, west of Bombay High the Palaeogene and Miocene are represented by a thick sequence of limestones and thin shales having poor source rock characteristics. In the south east, along the Panna-Bassein structural trend, Palaeogene consists of limestone and shale. In the north east, Palaeogene is represented by thick shales, which are considered to be source rock for Bombay High (Miocene oil accumulation), Panna, Heera and Ratna (Palaeogene oil accumulation).

SIGNIFICANCE OF SUBJECT MATTER :
This paper briefly gives the review of exploration activity in the Bombay Offshore basin, which has been a prolific hydrocarbon bearing province in the Offshore area of India and where big oil and gas fields have been already found.
Rov Involvement During Installation, Inspection, Maintenance,And Repair Of Offshore Structures
Authors: Watt A. , Smith G. , Goldberg L. 
Published: October 2008

ABSTRACT
This review paper addresses the role of the Remotely Operated Vehicle (ROV) during Installation, Maintenance and Repair of Offshore Structures. Tasks encountered by the ROV are discussed along with problem areas where some research and development is still required.- Two areas specifically discussed are the removal of marine growth for weld inspection and the bulk removal of marine growth in order to reduce structural weight and drag loadings.

INTRODUCTION:
The ROV is now well established as a viable tool for supporting drilling operation and conducting route and pipeline surveys. Personnel associated with offshore structure installation, repair and maintenance have been slower to accept the ROV. In many cases this is simply due to the unawareness of an individual as to the capability. It can also rightly be argued that the ROV is still very limited in some roles. It is the intention of this paper to highlight the tasks which an ROV can complete successfully and illustrate areas where the ROV is limited and the reasons why. Further research and development must be encouraged by the oil companies and research groups to overcome these shortcomings if the ROV is to be utilized to cut costs associated with installation, repair and maintenance of offshore structures. With successful research in the areas discussed another hurdle will be overcome in the history of the ROV resulting in significant cost savings to the end users ie the offshore structure owners and operators.

PLANNING INSTALLATION OF OFFSHORE STRUCTURES
When designing any offshore structure, the designer takes into consideration many factors. These include: method of installation, water depth (beyond diving range?) maintenance routines, repair techniques, expected structural life, etc. Likewise the ROV operator must consider which tasks have to be completed and choose the ROV best suited to the work. He can choose from his armory of:–Eyeball Class ROV's–Inspection Class ROV's–Workhorse Class ROV's
Eyeball Class: A small ROV which has limited capability but can adequately take still and video pictures. Some eyeballs can carry miniature manipulators and tools
Inspection Class: A slightly larger ROV with improved but limited manipulator capability. It also as a limited payload of 50 to 100 lbs.
Workhorse Class: A high powered ROV which can carry a payload in excess of 200 1bs and usually carries two full sized manipulators. It has the capability of interfacing many items of equipment, some of which can be custom designed for the application. This class is able to carry out the majority of the work tasks encountered offshore.

OFFSHORE STRUCTURE INSTALLATION PHASE
The offshore installation phase starts with the tow-out of the structure to the chosen site. Normal practice is to pre-lay a transponder network to allow accurate positioning of the structure relative to the seabed target area. The barge moves in and at this point the ROV can begin working.
Progress In Computer Simulations Of SPM Moored Vessels
Authors: Wichers J.E.W. 
Published: October 2008

ABSTRACT
In the last ten years computer simulation programs for SPM moored vessels have been developed by several authors. At present the application of such programs, if at all, is limited to some preliminary calculations in the very early design stage. The reasons for the reluctance to apply such computation methods in the more final stage of the design is clearly due to the failure of reliable input data and uncertainties concerning the procedures to describe the governing physical phenomena more accurately.
In this paper experimental and theoretical results for the input and the methodologies involved in simulations of the behaviour of and the mooring forces induced by a large tanker moored in wind, irregular waves and current will be presented.

INTRODUCTION
A vessel moored in the open sea can perform high and low frequency motions. The low frequency oscillations can be an important problem. The large horizontal excursions that occur can cause large forces in the mooring system.
As is schematically indicated in Fig. 1, in the computation procedure distinction can be made in a low frequency and a high frequency part of the equations of motion of a moored vessel. Nowadays reasonably reliable computations can be carried out concerning the high frequency input for the equations of motion. For the low frequency part, however, uncertainties exist concerning the input of the hydrodynamic reaction forces and the wave drift force excitation in current. Since, in general, an SPM system is a weakly damped system, reasonance peaks in the modes of motions in the horizontal plane can often be clearly distinguished. Therefore in order to predict the motion responses correctly, attention must be paid not only to the excitation but also to the damping.
In this paper results will be presented on input data and computation procedures in order to clarify the mentioned uncertain terms in the equations of motion of the low frequency part.
In order to obtain the low frequency hydrodynamic damping an extensive model test program has been carried out. .A review of the experiments is shown in Fig. 2. Some results will be given in this paper. To show the computation procedures examples for 1-DOF and 3-DOF will be highlighted.
For the 1-DOF of a linearly moored 200 kDWT tanker the following computation procedures will be dealt with:–wave drift force and wave drift damping in still water;–wave drift force and wave drift damping in current;–viscous surge damping in still water and in current;–solution of the equations of motion in the frequency domain.
For the 3-DOF case a formulation of the coupled equations of motion for tanker motions in the horizontal plane (in still water and in a current field) has been experimentally determined. In the past descriptions of the equations of motion for the low frequency tanker motions in the horizontal plane have been given by many authors, ref. [1] through [11].
Deepwater Mooring Operations In The Gulf Of Mexico
Authors: Zumwalt C.E. 
Published: October 2008

ABSTRACT
In the twelve years since exploratory drilling has begun on the Gulf of Mexico's continental slope, mobile offshore drilling units' mooring systems have become increasingly sophisticated and the technology for their design and use has become well established.
With the advent of sophisticated computer analysis software, improved weather forecasting, seafloor surveys, high holding capacity anchors, permanent chain chaser systems, upgraded anchor boats, Loran-C based rig positioning systems and effective planning and coordination, it is now possible to routinely moor a rig quickly and safely in from 600 to 2000 feet of water in the Gulf of Mexico.
There is increasing interest and competition in drilling on the Gulf of Mexico's continental slope. This paper reviews the new equipment and technology being used in the Gulf to safely and efficiently moor mobile offshore drilling units on the continental slope.

INTRODUCTION
The Gulf of Mexico's continental slope begins at the 600 feet of water depth line where the continental shelf ends and extends out to over 10,000 feet of water. Only depths to just under 3,000 feet have been drilled from moored, mobile offshore drilling units (rigs).
The continental slope from Texas' southern border to southern Florida is under the dominion of the united States government which has divided it into 12 lease areas each of which is subdivided into many approximately 3 mile square lease "blocks"1. These lease blocks are shown in Figure 1. With the exception of the Destin Dane area, Florida's continental shelf area is not a promising area for future drilling and, for this reason, these lease areas are not designated in the figure.
Of the over 280 exploratory wells drilled on the continental slope from moored rigs, the majority have been drilled in the Mississippi and Green Canyon areas as tabulated below 2
Particularly since the 1983 federal lease sale in these areas, exploratory wells are being drilled in increasingly deeper water as shown in Figure 2. Note that most of the wells were drilled from chain moored rigs even in the deeper water areas. This is due to several factors.
One factor is that the majority (65%) of rigs are chained moored vs a combination of wire rope and chain and that most of the rigs available in the Gulf of Mexico are also chain moored3 .Another factor is the introduction in recent years of higher strength chain commonly designated Super Oil Rig Quality or K4 chain which allows chain moored rigs to safely drill in over 2000 feet of water under most environmental conditions.
With the increasing rig competition the emphasis on efficient and safe mooring operations has intensified. In these deeper waters large amounts of mooring equipment must be recovered, stored and redeployed each time the rig is moved. To improve mooring efficiency and safety several trends have developed in the industry.
Wave Dynamics Of Jackup Rigs
Authors: Grenda K.G. 
Published: October 2008

ABSTRACT
A study was conducted to investigate the dynamic response to wave loading of a typical mid-sized jack-up drilling rig in the elevated position. Results of the study revealed the potential for significant dynamic amplification of wave loads in water depths exceeding about the 150 ft range. Major parameters studied were water depth, damping ratio, and current velocity. The increase in wave-induced leg stresses due to the inclusion of dynamic effects was calculated to be on the order of 20% and 150% for the subject rig in 150 and 300 ft of water, respectively. Sensitivity to damping ratio was found to be quite high, while the effect of currents was minimal.
The dynamic analysis procedure used in the study incorporated a time domain simulation method with a simplified wave-load model. This procedure allowed for explicit treatment of wave-load nonlinearities while maintaining reasonable computer costs. The simulation results were cast in the form of probability distributions from which extreme dynamic response parameter were evaluated. These extreme response parameters were then used to define dynamic amplification factors which were easily incorporated into structural evaluations of the jack-up rig.

INTRODUCTION
Recent structural assessments of several jack-up rigs demonstrated the potential for significant dynamic amplification of wave loads in water depths exceeding about the 150 ft range. Incorporation of the wave dynamic effects into structural analyses resulted in substantial reductions in calculated limiting environmental conditions for the rigs in the 150 to 200 ft water depth range. Had the effects of dynamics been ignored in the structural analyses of these rigs, different conclusions would have been reached regarding the structural suitability of several of the rigs at the proposed drilling sites.
Because of these findings, a study was initiated to investigate the potential impact of dynamic effects in even deeper water. A single jack-up rig, selected as typical of the mid-sized jack-up rig fleet, was chosen for analysis in this study. The major parameters studied were water depth, current velocity, damping ratio and degree of spud can fixity. These latter two parameters were included since there exists considerable discrepancy in the offshore industry as to what levels of damping and what degree of spud can fixity are appropriate for dynamic analyses of jack-up rigs.
The purpose of this paper is to present the findings of this parameter study by, first, presenting results in terms of base shear and overturning moment dynamic amplification factors (DAF?s) and, secondly, by presenting the effects of a given DAF on the limiting environmental conditions calculated for the rig.

DESCRIPTION OF ANALYSIS RIG
The rig analyzed in this study is a typical mid-sized, three-legged, independent leg jack-up rig capable of operating in water depths of 300+ ft. The specific rig details are not of consequence to dynamic amplification except as they affect the fundamental natural period of the rig.
Concrete Hulls For Tension Leg Platforms
Authors: de Oliveira J. , Fjeld S. 
Published: October 2008

ABSTRACT
This paper describes the main features of a concrete hull TLP concept developed for the Heidrun Field. The hydrodynamic response and the methods adopted to optimise the hull dimensions are first discussed, as well as the mooring system and the hull mechanical outfitting. The construction methods and possible transportation and installation scenarios are presented. The subjects of inspection, maintenance and repair are also briefly addressed. Finally the advantages of the concrete hull TLP concept are summarised, including it's adaptability to a large range of design requirement, its insensitivity to moderate design changes, and its low cost and short construction time. This paper shows how the concrete hull TLP can offer a very cost efficient solution for the development of deep water fields.

INTRODUCTION
The Tension Leg Platform (TLP) is a compliant offshore structure that offers great advantages for drilling and production operations, particularly in deep waters. The concept is now well known, given almost four years of successful operation of the Hutton TLP in the U.K. Sector of the North Sea. Efforts are now being made to improve the capabilities of such platforms, especially with regard to increased payload, more efficient methods of construction, simpler mooring systems and foundations. These efforts are leading to cost effective alternatives which will make the TLP concept a front runner for many offshore field developments. One such alternative is the concrete hull TLP, which is the subject of this paper.
By choosing concrete as the building material for the TLP hull it is possible to design the platform for topside loads of 50.000 t or more. Also, concrete offers many advantages, such as a relative insensitivity to fatigue and corrosion, minimum maintenance requirements and small loads on the mooring system and foundations. The construction period required for concrete is significantly shorter than for steel, and the associated costs are also expected to be lower. It is felt that the possibility of using concrete as a building material for the TLP hull brings a new dimension to the TLP concept, and makes it even more attractive in the development of large deep water offshore fields.
The present paper describes the main features of a concrete hull TLP conceptual design developed for the Heidrun Field, in the Haltenbanken area of the Norwegian sector of the North Sea. This concept has been adopted for the development of the Heidrun Field by Conoco Norway Inc. and its Co-licensees. A description of the concrete hull TLP is given, including the design basis and requirements, the platform dimensions and configuration, the hydrodynamic response, the hull structure, the mooring system, the mechanical outfitting, construction, transportation, installation and operation. Finally, the advantages of the concrete hull are discussed, and the most salient features of this concept are summarised.
Model Testing Of A Deepwater Salm/Tanker System
Authors: Watson G.D. , Koch S.P. , Watson M.J. 
Published: October 2008

ABSTRACT
The paper describes the results of physical model tests undertaken to investigate the performance of a deepwater SALM/tanker system in a wind, wave and current environment. The system tested is an element of the Esso Deepwater Integrated Production System (EDIPS), for which a conceptual design was completed in 1987 for Esso Exploration and Production UK Limited.
The testing program required development of several novel transducers which are described in the paper and necessitated hydroe1astic modelling of the SALM lower riser to ensure that accurate vibration response to wave and flow excitation was obtained. Tests were undertaken in a variety of conditions which included multidirectional waves and oblique wind directions. The test results demonstrate the increased loading and motions caused when the environmental loading is not collinear. The vibration response of the lower riser and the effect of an inertia skirt on the performance of the double articulated SALM are also described in the paper.

INTRODUCTION
An extensive matrix of wave tank model tests were carried out at the British Maritime Technology (BMT) on a model of a deepwater SALM/Tanker system. The work was funded jointly by Esso Exploration and Production UK Limited and the UK Department of Trade and Industry Marine Technology Committee, and was done under the technical stewardship and coordination of Esso's research affiliate, Exxon Production Research Company.
The model tests were conducted with two primary objectives:To act as a comparison for BMT's time domain computer simulation program BMTSPM.To study the dynamic behavior of the SALM/tanker system, which is an element of the Esso Deepwater Integrated Production System (EDIPS) (Reference 1).
The SALM system (Figure 1) consists of a buoy moored to the seabed by a single, tensioned riser. The system was designed to operate in a water depth of 610 meters and moor a storage tanker of approximately 250,000 deadweight tonnes capacity. The riser was pin-jointed at both the seabed and the connection with the lower buoy. A removable inertia skirt was fitted to the lower buoy to increase the local added mass and reduce the motions at the mid-water universal joint. The buoy was connected to the tanker by a rigid, pivoted yoke.
The SALM buoy, yoke, and tanker models were fabricated conventionally as rigid elements, and were fitted with lead weights to achieve the desired weight, center of gravity and radii of gyration. A flexible model of the riser was designed and built to have the proper scaled bending stiffness. This was a principal challenge of the program, and was done so that the riser's vibration response over the frequency range of predominant wave energy could be measured. Unlike the approach usually taken to model test shallow water SALM systems, the riser cannot be considered a rigid element in deep water systems.