bluuebunny/crossref_metadata_2025 huggingface dataset:
The IPOD Geological/Geophysical Data Bank
Authors: Rabinowitz P.O. , Brenner Carl
Published: October 2008

The IPOD Data Bank has served the JOIDES community since 1975 by finding and collating existing marine geological/geophysical data in the vicinity of prospective IPOD drill sites or transects of sites, archiving all data collected under the auspices of the IPOD Site Survey program, providing folios of data to the designed co-chief scientists on D/V GLOMAR CHALLENGER (and on request to the various JOIDES subject panels), and supporting the JOIDES and DSDP Safety Panels by providing data packets to its members.

At the Data Bank, U.S. institutional site survey data is stored digitally in NGSCD "mergedmerged" format and is available either in the form of a magnetic tape or a computer plot of annotated geophysical (bathymetry, magnetics, and gravity) values along track. In addition, seismic profiles collected during the surveys are also archived. Contour maps, heat flow charts, bottom photographs, and other forms of data presentation compiled in the course of the production of a cruise report are also often archived.

INTRODUCTION

By the early 1960s, scientists at the major oceanographic institutions recognized that substantial advances in marine geoscience were within grasp. Up to that point, the only sampling of the deep-sea floor was in the form of dredge hauls and cores. Though these contributed greatly to our understanding of the geological history of the ocean floor, these methods only provided data from the upper 20 m of the ocean floor. The need to penetrate deeper stratigraphic sections (and later into the ocean crust) was obvious. Four of the major institutions - Lamont-Doherty Geological Observatory of Columbia University (L-DGO), Scripps Institution of Oceanography of the University of California at San Diego (SIO), Woods Hole Oceanographic Institution (WHOI), and Rosenstiel School of Marine and Atmospheric Science of the University of Miami (RSMAS) - decided to work together in developing a unified program of deep sediment coring. In 1964, these institutions signed a memorandum of agreement and inaugurated the Joint Oceanographic Institutions for Deep Earth Sampling JOIDES.

The initial effort of JOIDES was managed by L-DGO under the sponsorship of the National Science Foundation (NSF) and drilled several deep holes on the continental margin off northern Florida in the region of Blake Plateau. The drilling vessel was M/V CALDRILL I, a converted 54 meter AKL-type navy vessel equipped for rotary drilling. l The success of this effort provided the impetus and framework for a more ambitious drilling program. Under the sponsorship of NSF, SIO was designated the operating institution for what became known as the Deep Sea Drilling Project (DSDP) and a world-wide drilling program commenced in 1968. The operating vessel was D/V GLOMAR CHALLENGER; this arrangement is still in existence today.
Overall Dynamic Characteristics of Tension Leg Platforms
Authors: Oran Cenap
Published: October 2008

In TLP motion analysis, the problem is usually simplified by idealizing the tethers as weightless springs. While this approximation appears to be generally adequate for shallow waters, the relative tether/platform weight ratio increases very rapidly as the water depth increases, thus making it necessary to the at the TLP as a continuous system rater than as a rigid body with only six degrees of freedom. The purpose of this paper is to examine the variation of the overall dynamic response characteristics of a TLP as a function of the water depth, with particular emphasis on such important parameters as the tether/platform weight ratio, the periods of the "principal modes" (i.e., heave, pitch, roll, surge, sway and yaw) and the shapes and periods of the "secondary modes".

INTRODUCTION

Offshore platform technology for relatively shallow water (approximately less than 1000 feet) is well established. However, as the demand for oil continues to increase, the industry is gradually forced to move into more hostile environments, namely, deeper waters where conventional fixed platforms are no longer feasible and arctic regions where the engineers are faced with a variety of ice-related problems. Two principal concepts have thus far been advanced for oil product ion in deeper waters, namely, the "tension leg platform" which is usually referred to briefly as the TLP and the "guyed tower".

A central issue in the design of an offshore platform is the dynamic behavior of the platform under the action of wave, current and wind loads. The wave climate at a specific geographic location is usually represented by a "wave spectrum". A review of wave spectra representing the conditions at major offshore oi1 production areas of the world shows that the most critical wave period range is approximately 5 to 20 seconds. Accordingly, in order to avoid possible resonant behavior, platforms are designed in such a way as not to have a natural period within that particular critical range.

In the case of a fixed pl at form, the relevant vibration mode is the so-called "lowest mode", i.e. the mode that corresponds to the lowest frequency and, consequently, the largest period. It is clear that, if the largest natural period of the platform is kept below 5 seconds, the remaining natural periods will be even smaller so that one does not need to worry about them in the process of design. In the case of a tension leg platform, however, the situation is somewhat more complicated as wi11 be apparent in the following section.
Lena Guyed Tower Project Overview
Authors: Boening D.E. , Howell E.R.
Published: October 2008

The installation of the Lena guyed tower was one of the industry's most significant accomplishments of 1983. This paper serves as an introduction to a series of papers to be presented at the 1984 Offshore Technology Conference concerning the design, fabrication, and installation of the Lena guyed tower.

The purpose of the paper is to provide an overview of the entire project, including the evolution of the guyed tower concept and the extent to which this concept may be applicable to other prospects. The most important design features of the Lena guyed tower are briefly discussed in order to prepare the reader for the more detailed treatment provided by the other papers in this series.

Particular attention is focused on project management, primarily from the perspective of manpower usage, schedule control, and cost management. Successful techniques that may be of value in the management of future projects are identified.

INTRODUCTION

Guyed Tower Development

Since the offshore petroleum industry began in the 1940's, an economical means of developing reserves in progressively deeper water has been pursued. As water depths of interest increased, the size and cost of conventional, pile-founded, steel-jacket platforms increased at a much greater rate.

One approach to the problem of disproportionate increases in the size of the deepwater structures has been the use of guying systems. Exxon Production Research Company first considered the guyed tower in 1965. In 1975 Exxon and 12 other companies built a one-fifth scale model of a tower designed for use in 1500 feet of water. The unmanned, heavily instrumented test tower was installed in 300 feet of water in the Gulf of Mexico near Grand Isle, Louisiana. The foot-square tower had eight 3/4-inch guylines that modeled a full-scale system.

Test data from the tower confirmed that the basic guyed tower concept was sound. During 3 1/2 years of operation, the test tower experienced a number of waves that, in full scale, approximated or exceeded North Sea design conditions. Maximum measured guyline tensions and tower .motions matched well with predicted maximum tension and motions.

Lena Guyed Tower

In mid-1978, a decision was made to design a guyed tower specifically for the 1000-foot. Wterdepth at the Lena Prospect in the Gulf of Mexico. As shown in Figure 1, the Lena Prospect straddles the 1000-foot water depth contour line and consists of four tracts, all of which are in the Mississippi Canyon area.

The design of the Lena guyed over. Differed significantly from the test tower con. The use of a spud-can foundation was located to favor of eight centralized main piles to prevent settlement. Torsion piles were added at each of the four corners of the jacket to resist base torque and shear loads.
Time-Domain Model for TLP Surge Response in Extreme Sea States
Authors: Finnigan T.D. , Petrauskas C.D. , Botelho D.L.R.
Published: October 2008

A time-domain model is presented and evaluated for the prediction of the surge response of a tension leg platform (TLP) will regular and random waves, in the presence of a current. The wave force equation in the model is a modification of the Morison equation. Wave diffraction effects are incorporated in an approximate manner.

The time-domain model is evaluated on the basis of experimental tests that were performed on a 1: 60 scale model of a TLP. The tests were specially designed to investigate the effect of combined waves and current on surge response. The tests were conducted in regular, random and grouped waves. Current was simulated by towing the model.

Two different forms of linear wave theory based on stretching and extrapolating wave particle kinematics from Airy wave theory up to the free surface are investigated. The maximum surge response is predicted well by the time-domain model, provided the extrapolation of Airy wave theory is used.

INTRODUCTION

The tension leg platform (TLP) is a compliant structure In order to design the TLP tendon and riser subsystems, the maximum offset the TLP will experience in extreme sea states must be accurately determined.

In such sea states, large offsets due to nonlinear wave-current interaction and free surface effects can occur. Methods for predicting the surge response must therefore account for these effects. Although frequency-domain methods are available for predicting the TLP surge response, 1,2 time-domain methods can more accurately account for the nonlinearities.

In this paper, a time-domain model to predict the surge response in extreme sea states is presented and evaluated. Its primary purpose is for final design verification. A secondary purpose is to develop response amplitude operators (RAO's) for frequency domain procedures. 1 The time-domain model is based on a modification of the Morison wave force equation in which forces are integrated up to the free surface. The modifications include a representation of a) the drag forces using relative velocities including current, and b) the inertia forces corrected to match MacCamy and Fuchs' closed form diffraction solution. 3 With these modifications, the time-domain model is able to depict the surge response at the wave periods (primary response), and at periods much longer than the wave periods (secondary response or slowly-varying drift). Although the TLP can respond at its natural period, no distinct response occurs there because of the high damping due to current.

Time-domain models have been developed by Hsu and Blenkarn, 4 Paulling, 5 Salvesen, 6 Morgan7 and others. The time-domain model in this paper differs due to the manner in which diffraction effects have been incorporated. Also the paper evaluates alternative wave theories. The results of this paper are expected to contribute further to the understanding of time-domain predictions of TLP surge motion.

In this paper, the theory used in the time-domain model is presented.
Produced Water Discharges into Marine Ecosystems
Authors: Pitre R.L.
Published: October 2008

Formation waters which are produced in conjunction with oil or gas are discharged into offshore areas throughout the world. The produced water volume in petroleum production can vary from 20% to 150% of the oil production volume. Salinities of produced water can vary from 1,000 to 250,000 ppm. Before prod used waters are discharged to the ocean, they are passed through oil-water separators to reduce the oil content to acceptable levels. Temperatures of the produced water stream are normally about 45° C. The small amounts of oil released in prod used water discharges will either evaporate to the atmosphere or be degraded by marine organisms. Biodegradation can be enhanced with the addition of nutrients. Within the OCS of the United States, produced waters are regulated by NPDES permits issued by the U.S. Environmental Protection Agency. Produced waters from a Cities Service platform located in an area of coral reefs offshore of the Philippine Islands have been discharged to the surrounding seas for several years with no environmental harm. Environmental impacts from produced water discharges into marine waters are very minimal and have never caused a problem. Therefore, there is no precedent for stricter governmental regulation of produced water discharges into marine ecosystems.

INTRODUCTION

Produced water is formation water which is produced in association with oil and gas from the producing formation. Formation waters have existed for a very long time in the formation, usually under conditions of high temperature and pressure. Because this water contacts the minerals and crude oil in the rock formation, the water becomes saturated with the particular minerals present and with the soluble fractions of the untapped crude oil, especially the low molecular weight hydrocarbon gases and naphthenic acids. Why the water exists in the oil and gas reservoir and why its chemical characteristics vary as they do has not been shown through any accepted theories1 Most research assumes the water was deposited with sedimentary formations. The deeper, older formation waters are generally more saline; however, there are many exceptions to this rule depending on the composition of overlying formations. Other assumptions are that this formation water may have stayed where it was deposited, or it may have migrated into the oil and gas reservoirs.

Oil or gas and water, in the reservoir, exist separately in equilibrium. When formation water reaches the surface, where the surrounding pressure is much less than that in the formation, some amounts of the dissolved gases flash-off, and they are extracted. The characteristics of produced water from different offshore production areas are shown in Table 1. The produced water volume in petroleum production can vary from 20% to 150% of the oil production volume. Salinities of produced waters can vary from 1,000 ppm to 250,000 ppm1
Wave Runup and Overtopping: A Review and Recommendations
Authors: Gadd P.E. , Potter R.E. , Safaie B. , Resio D.
Published: October 2008

It is not always feasible to design a coastal structure high enough to completely prevent wave overtopping by the maximum incident wave. Structures which are designed against lesser waves, such as the significant wave, will be overtopped under the design storm condition because the incident irregular wave train contains waves which exceed the significant wave height. When the purpose of a structure is to protect sensitive facilities whose failure could result in major environmental as well as economic losses, the rate of overtopping anticipated under the design condition must be predicted with reliable accuracy.

The study being reported in this paper evaluates the degree to which wave overtopping can be accurately predicted for a coastal structure in the Arctic environment. In support of this endeavor, an extensive search and review of literature was performed, including reports and papers originating in Japan where the study of wave overtopping has been pursued for a number of years. The study has led to recommended design procedures as the most practical solution available from the current state of knowledge. Discussions on research needs to improve the design procedures are also presented.

OVERVIEW

Goda (1970) proposed a scaling factor to describe various levels of overtopping intensity, as follows:(Mathematical equation available in full paper) which in this paper will be called the "overtopping index". "Q" is defined as the overtopping volume per wave per unit width of crest, and (HoLo) is the mass transport during the forward orbital motion of a sinusoidal wave in deep water. The overtopping index is non-dimensional.

According to Goda (1970), the overtopping index remains in the range of between zero and 10–4 when the overtopping consists only of wave spray. When the overtopping involves wave splash as well as spray, the index will rise to as much as 5 × 10–3. The next higher level of overtopping intensity, consisting of the leading edge of the wave run-up going over the crest of the slope, will raise the index to 10–2 The most severe overtopping situation, in which the wave itself plunges across the crest of the slope, will bring the index to a high of 10−1 Actual overtopping rates may be readily found from the overtopping index assuming a hypothetical storm wave of, say, Ho = 12 feet and T = 10 sec. The overtopping rates {in cubic feet/sec/foot of wave crest) corresponding to the upper limit for each class of overtopping intensity are: 0.01 cfs/ft for spray overtopping, 0.5 cfs/ft for overtopping by wave splash, 1.0 cfs/ft for overtopping by the leading edge of the run-up, and 10 cfs/ft for overtopping by the wave itself. It is obvious that even wave splash could pose a threat of localized flooding, depending upon incident wave characteristics.
A Review of the Geology and Petroleum Possibilities of the Continental Margins of India
Authors: Sahay B.
Published: October 2008

Continental margins which flank western and eastern limits of India are broadly divided into West and East Coast. The width of the eastern Continental Shelf varies from 300 km near Bombay to approximately 80 kms near Porbandar, narrowing further towards south to 60 kms near Cochin. The Eastern Continental Shelf which extends from Cape Comorin to Calcutta, has the width varying from 2.5 km, about 150 kms south of i1adras to 2JO kms up to Ganges river delta, near Calcutta.

WEST COAST

The continental western margin has been divided into six sedimentary basins. They are Klitchasin, Saurashtra basin, Bombav Offshore Basin, Konkan basin, Laccadive basin, and Kerala basin. Surface geological exposures along the western margins of India are known in Kutch and Saurashtra Peninsula and in a thin strip along the coast near Cochin. These basins being graben type, the stratigraphy of the basins extending into the shelf is inferred mostly from the seismic data.

EAST COAST

The Eastern Continental margin of India has been also divided into six major sedimentary basins, which from South to North are Cauvery basin, Palar basin, Godavari-Krishna basin, Mahanadi basin, Benqa1 basin and Andaman-Nicobar basin. The surface geology of eastern continental margin is available near Cape Comorin, which is mostly Archaen rocks, with thick covering of Tertiary sediments, which are also found along the north western coast of Ceylon. Further north it consists of Cretaceous and Tertiary rocks overlain by Pleistocene and Recent sediments.

RESULTS

Reconnaissance and semi-detailed geophysical surveys have helped in delineation of big and small structures in western and Eastern margins of India. The first offshore exploratory work along the western continental margin. Was undertaken in the Bombay Offshore basin, which is a continuation of the Cambay basin on the land, where oil and gas fields were found earlier. Evaluation by drilling of important structures like Bombay High, Panna, Basseitn, Ratna, Heera, South Papti, etc. have resulted in the discovery of oil and gas fields. A full sedimentary section of more than 4 km. resting on Trappean/Pre-Cambrian basement has been met. Hydrocarbon bearing horizons range in are from middle Miocene-Eocene. Lot of facies variation has been noticed and which probably has been responsible for the hydro carbon accumulation/absence in a different structures in this basin. The other offshore basins, Kutch and Saurashtra are being evaluated as a result of the encouraging data obtained in the adjoining Bombay Offshore basin.

In the East Coast, big and small structures have also been delineated in the different sedimentary basins. Drilling carried out in the; Cauvery basin, Godavari, Bengal Offshore basins and Andaman and Nicobar islands has also indicated hydrocarbon shows both of smaller and bigger magnitude. These areas are now under active exploration for a thorough evaluation of their hydrocarbon potential in the prospective structures.
Finite Element Analysis of Bending in a Threaded Connector for a 5 1/2-in. Marine Riser
Authors: Allen M.B. , Eichberger L.C.
Published: October 2008

This paper describes the development of a new finite element modelling technique for performing nonlinear bending analysis of tubulars and its application to a threaded connector for a 5–1/2 inch production tubing marine riser.

A finite element technique has been developed for analyzing bending loads applied to an axisymmetric geometry. The method uses a Fourier series solution. The first two terms of the series are solved simultaneously, allowing nonlinearities to be included since the method does not use superposition, which normally requires linearity. Existing methods of analysis require either a linear elastic assumption and axisymmetric approximation of bending loads, or a full three dimensional analysis. The new technique includes nonlinearities in mechanical properties, gapping, and friction. It is more accurate than the method where axisymmetric loads are applied so that pipe OD stresses are the same as those that would result from bending. The model is considerably less complicated to use than a three dimensional model and is also considerably less expensive.

The method described above is applied to a 5-1/2 inch threaded connector. The connector is analyzed under make-up, tension, pressure, bending, and shear loads. Predictions include average and reversing stresses in the pin and box wall and at stress concentrations. These predictions can be used to evaluate the fatigue life of the connector.

Introduction

Fatigue analysis is important in determining the expected useful life of a marine riser. As with any tubular string, one of the weak links of the system is the joint connections. In the case of a marine riser, the connector is an area of complex stress distributions and stress concentrations. Full scale laboratory tests can go a long way towards determining the tensile strength and leak resistance of a threaded connector, but it is nearly impossible to measure stresses or strains at critical locations in the connector (at thread roots and seal ring grooves) or to test a connector until it falls in fatigue. However, fatigue calculations require that the connector stresses be computed.

Finite element analysis has been applied as a useful tool in connector design and evaluation. It is most useful in determining stresses and deformations that cannot be measured in the laboratory and in determining the effects of connector variables and loads that are not easily controlled in the lab. In this case, accurate stress values can only be obtained with a finite element analysis.

Due to the complex and nonlinear behavior of a threaded connector, existing finite element codes could not efficiently model a connector subjected to shear and bending loads. The objective of the work presented in this paper was to develop the capability to perform efficient nonlinear analysis of bending in tubulars, then apply the newly developed method to analyze a threaded connector for use in a marine riser.
Research and Development Project of Manganese Nodule Mining System in Japan
Authors: Takahara H. , Handa K. , Ishii K. , Kuboki E.
Published: October 2008

The Agency of Industrial Science and Technology, the Ministry of International Trade and Industry, Japan, started the large-Scale Project entitled, The Research and Development Project of Manganese Nodule Mining System in FY1981. The Project is scheduled to last until FY1989 with a total budget of about 20 billion Japanese Yen (about $85 million, U.S.). The mining system being researched and developed in the Project is a hydraulic mining system in which manganese nodules are collected a towed vehicle on the sea floor and are transported in a slurry of seawater and nodules through the lift system onto the mining ship.

In the Project, R&D of technology has been conducted to complete a highly effective, reliable and well-coordinated ocean mining system; furthermore the commercial feasibility has been evaluated. In the last stage of the Project, a pilot scale mining test is scheduled in the Pacific Ocean.

INTRODUCTION

Manganese nodules, which contain significant quantities of copper, nickel, cobalt and manganese, are considered to be an important future source of minerals which are crucial to Japanese industrial and national security interests. In other words, it is absolutely important for Japan to recover manganese nodules from the deep ocean floor since it will ensure a stable supply of four strategic metals as "quasi-domestic" sources for Japan, where these metals are in short supply and must be imported.

Entirely new technology, however, is required for recovering the nodules from the deep ocean floor. In addition, according to the new Law of the Sea Treaty adopted at the United Nations Conference on the Law of the Sea in 1982, those who would develop deep ocean manganese nodules would have to possess their own mining technology and would be required to transfer it to the international organization, or the Enterprise.

Under such circumstances, the Agency of Industrial Science and Technology (AIST) of the Ministry of International Trade and Industry (MITI) selected the Research and Development Project of Manganese Nodule Mining System as one of the National Research and Development Programs in FY1981. The Project is scheduled to last until FY1989 with a total budget of about 20 billion Yen (approx. $85 million, U.S.).

NATIONAL R&D PROGRAM

The National Research and Development Program (popularly known as the Large-Scale Project) has been conducted by the AIST since 1966. This is-a program for urgent, expensive, risky and long-term projects which it would be difficult for private firms to undertake alone. The AIST promotes such important projects as mentioned above under contract with industry.

Promotion of such technological development by the government will not only increase the sophistication and knowledge-intensiveness of the Japanese industrial structure, but will also help to expand the world's technological frontier, to revitalize the entire world economy and to contribute to international community.
Molikpaq: An Integrated Mobile Arctic Drilling Caisson
Authors: Hnatiuk J. , Felzien E.E.
Published: October 2008

The design, installation and performance of Molikpaq, an innovative mobile steel drilling caisson designed to cope with the severe ice conditions in the Beaufort Sea are summarized. The environmenta1 constraints and the rationale for choosing the unique design are briefly discussed. A sub sea berm was constructed and tested prior to placement of the caisson. The caisson was installed in September 1984 by ballasting it down onto the berm and subsequently filling the central core of the caisson with sand for stability against sea ice forces. In the interests of safety, the berm and caisson are instrumented and carefully monitored. The 95-foot high caisson is much higher than any used to date and is so designed to reduce the volume and cost of the sub sea berms. The design of the caisson permits its quick relocate on to a new dri11ing site during the short open water period in summer, since the drilling equipment and accommodation are an integral part of the unit. Molikpaq, the Inuit name for "great wave" can be utilized in water depths ranging from 50 to 130 feet by varying the sub sea berm height. It can be operated in a range of sea bottom conditions by appropriate preparation of the foundation. Since it is designed to withstand multi-year ice features, it is capable of year-round drilling. Valuable performance data being acquired will be very useful in the design of other exploratory drilling units or larger production platforms in the future.

INTRODUCTION

Permits were issued over the period 1963 to 1969 to explore for oi1 and gas on the majority of the Canadian continental shelf of the Beaufort Sea which extends some 75 to 100 miles to a water depth of 600 feet. Gulf Canada Resources Inc. operates 2.5 million acres mainly in the 60 to 140 ft. water depth range. The Geological Survey of Canada's average expectations of the hydrocarbon potential of the Beaufort Sea-Mackenzie Delta 8.5 billion bbl of oil and 66 TCF of gas till Although many encouraging discoveries have been made offshore, the commercial viability of the reserves will depend on many factors such as pay thickness and other reservoir characteristics, well productivities, reservoir depth, water depth, distance from shore, environmental forces, sea bottom conditions, capital and operating costs, crude oil prices and fiscal regime. Further deli neat ion dri11ing is required for several discoveries including Gulf's recent Amauligak major oil discovery.

BEAUFORT SEA ENVIRONMENTAL CONDITIONS

Sea ice is the most severe environmental constraint in the Beaufort Sea, with the area of interest usually ice-covered nine months of the year. This sea ice affects operations as well as design of platforms. Freeze-up usually commences in early October, with new ice formation beginning near shore and slowly progressing offshore.
Reading Micro-Stratigraphy From Seismic Reflection Data
Authors: Peña R.E.
Published: October 2008

A transfer-matrix description for the propagation of 3D acoustic waves in a randomly stratified medium is considered. A general condition for the acoustic resolution of distinct micro-stratigraphic configurations is found. The calculation is exact and is used to identify which manipulations of field data yield best indicators of subsurface microstratigraphy.

Assuming that subsurface parameters vary with depth alone, the original 3D problem may be mapped into a parameterized family of dynamically independent ID problems. Each of these is solved by standard Green's function methods in terms of transfer matrices describing propagation through each constituent micro-layer. A simple, suitably weighted, stack of raw data yields a trace corresponding to any desired ID subspace. Shot attributes may be removed statistically or by other methods. Simple relationships exist between the spectral properties of the remaining trace and the ordered product of transfer-matrices for propagation through the micro-layers. The zero and finite offset reflection and transmission characteristics of a stratified geologic bed may be determined. A limited discussion of the most pertinent literature is also included.

INTRODUCTION

The possibility of reading the microstratigraphic structure of the earth's subsurface using long wavelength probes, has entertained the curiosity of numerous investigators. The basic idea is that though the micro-structures are scaled by a length very much smaller than the probing length, when they are distributed over some macroscopic dimension it ought to be possible to extract information about their characteristic statistical properties. The goal is not, therefore, to resolve individual structures but rather to obtain information concerning the correlation functions which specify their distribution. Availability of this type of information could significantly influence the judgment of geologists searching for hydrocarbons.

The first papers published in Geophysics which directly address this subject, appear to have been by C.W. Horton1, 2 in 1955 and 1957. From a signal-processing point of view he studied the problem of reproducible 'noise' in field seismograms. On the assumption of a totally random distribution of identical subsurface scatterers, a relationship was established between the reflection characteristics of each individual scatterer and the statistical properties of the seismogram.

A 1969 paper of Mathieu and Rice3 introduced multivariate or discriminate analysis for the differentiation of subsurface types. This method is based on reading a set of 'indicator variables' from each of a statistically significant number of traces or sections. Two stages characterize its implementation. The first is a learning stage in which well understood case studies or forward modeled examples are used to establish the relative discriminating power of each pre-selected indicator variable. The information is obtained in the form of factors which fix the discriminant function's sensitivity to variations in their values.
A Multi-National Consortium Opportunity For Satellite Remote Sensing
Authors: Maughan P.M.
Published: October 2008

Satellite remote sensing is one of the evolving space based technologies that is providing a new perspective and dimension for managing the earth's resources. Data from Landsat has proven useful in studying crop production, disease, drought, land use, flooding, deforestation and oil and mineral prospecting, among many other applications.

We are now convinced that the market for space based economic intelligence is pervasive and significant. It is necessary only to come up with a remote sensing data product at an attractive price that is readily available and the "world will beat a path to your door". Sound familiar? It is easier said than done.

The U. S. Government has recently shown willingness to conduct a true commercial market test, through a joint venture of RCA Corporation and Hughes Aircraft Company called EOSAT, to see if a market for land remote sensing data really exists. The French Government, through a French "commercial" group called Spot Image, intends to carry out similar marketing plans. The plans of Japan, Germany, Brazil, India, ESA and others in this area are still unclear, but it is expected that over the next five years we will see a large investment in market development.

EOSAT and Spot Image represent slightly different approaches to developing the remote sensing data product market. EO SAT is focused on a higher resolution, multi-spectral data product. Spot Image is investing in higher resolution stereoimage data products. Each has begun to build a market presence with the available resources.

1. The multi-national consortium concept was developed in concert with Dr. John L. McLucas, 309 North Lee Street, Alexandria, VA 22314.

Which of these approaches will prevail? In my judgment, what we are seeing now is only the first of several "cards" to be played. The approaches--that is, the product/price/availability model--will change to reflect the developing market. The model that will ultimately succeed will probably require significantly higher quality data, both spatially and spectrally, than either EOSAT or Spot Image will initially offer. If this is the case, the group that is most adaptable will clearly have the business edge.

Providing better quality data will necessitate increasing spatial resolution to, say, three meters, an order of magnitude better than Landsat 5 TM data. This is less of a technical challenge than a political problem.

At this point, there probably would be an outcry by certain countries over marketing higher quality images of their territory to a third party. I believe that such concerns would lead to a demand for intergovernmental agreements with stipulations permitting the sensed country to, among other things:Have first access to the data;Have the right to censor the data to remove sensitive material;Have exclusive rights to the data;Have the right to levy a charge based on the amount of territory sensed;Have the right to perform all value-added processing of the data.
Efficient New Processing System for Water Deoxygenation
Authors: Henriksen N. , Nord L. , Kjøberg S.A.
Published: October 2008

A new concept for DEOXYGENATION has been developed based on the use of an inert gas, which is recirculated; a specially designed stripping chamber and a catalyst bed.

The concept has been fully proven in a prototype unit handling 500 m3/hour sea water.

This unit is located on the Norwegian east coast and interested parties are welcome to inspect the installation. Long term development work will be carried out with this unit to assess its suitability for other applications and also to optimise mechanical and energy requirements.

The prototype has demonstrated the considerable advantages now available, when compared with conventional vacuum and gas stripping units.

Some of these advantages are particularly attractive for offshore operators viz:Substantial savings of space and weight.Very low levels of residual dissolved oxygen.The need for chemical scavengers can be eliminated.No large volumes of stripping gas requiring flaring - a major advantage over conventional gas stripping.Units will operate with unfiltered sea water without a build up of foulants.Units can be sited in platform legs thus saving deck space.Modular construction provides flexibility in performance.

The process comprises a stripping chamber in which nitrogen is used to remove dissolved oxygen from the liquid phase. Separated "gas" is thenpassed over a catalyst bed in the presence of a "reactant". Oxygen free gas is then returned to the stripping chamber for re-use.

Details of the process, laboratory studies and prototype operations are presented in this paper.

Introduction.

Sea water injection is widely used for enhanced oil recovery in offshore fields.

Removal of dissolved oxygen from sea water reduces the incidence of corrosion "pitting" of unprotected carbon steel equipment.

The elimination of corrosion is necessary to avoid "fouling" of flow lines or a build up of deposits at the well-bore face.

Current practice is to deoxygenate with large, packed towers, operating either under vacuum, or with natural gas as a stripping medium.

Such systems can reduce dissolved oxygen to very low levels, particularly gas stripping units, but the ratio of gas to water volume is very high and many governments have restricted the volume of gas which can be flared during normal operations. Conventional units must therefore be regarded as a compromise in terms of:SIZEWEIGHTCONFIGURATION (location)PROCESS RESTRICTIONS andPERFORMANCE

Residual dissolved oxygen levels of 50 to 100 ppb are obtained without theaddition of chemical scavenger.

Further reduction to less than 5 ppb O2 is achieved by the addition of a solution of either ammonium hydrogen sulphite or sodium hydrogen sulphite.

Large sea water injection systems consume substantial quantities of chemical oxygen scavenger. Such chemicals are not expensive in themselves but the logistics should be considered since bulk storage is often required both onshore and offshore, expensive travel tanks are required to satisfy IMCO standards (class I).
An Oil Pipeline Multiphase Pressure Drop Correlation
Authors: Ilic V. , Behnia M.
Published: October 2008

In their respective laboratories, the authors have begun an extensive experimental program of systematic, mu1tiphase (oil/water, water/gas and oil/water/gas) pressure drop and void fraction data generation in 25 mm and 100 mm bore inclined pipes. In conjunction with flow pattern transition boundaries records, this data will be used as a basis for establishing scaleup parameters when combined with the available field data.

The aim of the initial work reported here was to establish a basis for a simp1e-to-use mu1tiphase pressure drop correlation that could be applied to the design or assessment of pipelines with flows of mixtures of oil and gas phases.

189 field data points were selected from (1). Only fully documented data were used.

INTRODUCTION

A plethora of mu1tiphase pressure drop correlations exists that are currently used in the oil industry (2). A recent (3) evaluation of pressure drop and holdup correlations for gas/condensate pipelines showed that, while accuracy is better with the former, most of the correlations produce significantly large errors. A study of similar correlations with air/water mixtures (4) indicated increasing error with pipe diameter for currently used holdup and pressure drop correlations.

It has generally been the case that data best described by a given correlation usually originated with the author of the correlation. Because of the variety of field conditions under which pipelines operate, the designer usually has to select the most appropriate correlations and base his choice on the most conservative result to obtain the pipeline bore. The pipe diameter chosen in this way is invariably oversize, and therefore the installation excessively costly. With an average cost in Australia of an installed pipeline in the Vicinity of $US1000/mm km, a 100 km pipeline would cost $5 million more than it should if it was deliberately oversized by 50 mm. Improved and new multiphase pressure drop models and correlations will therefore be justified until the uncertainty in the design is significantly reduced.

Because data obtained in laboratory experiments are better controlled and generally more accurate than field data, they are amenable to systematic generation and modelling. However, because pipeline sizes and flowrates are considerably smaller under such conditions, data correlations based on laboratory experiments generally produce large errors when compared with field data (4). Accurate scale-up techniques therefore need to be developed to improve application of such correlations to field conditions. As a first step towards that end, a brief analysis of data from (1) was made and initial results are reported here.

The aim of this paper is to present results of this analysis in the form of a simp1e-to-use correlation for mu1tiphase pipeline pressure drop derived for a selected batch of 189 data points taken from (1). The basis for data inclusion was their completeness.
Acquisition and Processing of Shallow Water 3-D Seismic Surveys Over Producing Fields in the Northwest Niger Delta
Authors: Olofin D.K. , Will R.A.
Published: October 2008

Most of the fields operated by Gulf Nigeria on behalf of Nigerian National Petroleum Corp. (NNPC) and Gulf Joint Venture, lie in the shallow waters of the northwest Niger Delta. The techniques of radio-telemetric transmission of seismic data, shallow-draft seismic source vessels, and receiver swath survey methods have been used to gather data accurately and efficiently. Processing steps such as 3-D residual statics, dip move-out (DMO), and steep dip migration have been used to produce highly resolved images of the subsurface. The fields surveyed are mostly in mature stages of development and the 3-D data acquired in these surveys are better defined than the 2-D lines used for original mapping. Because of the new methods used to acquire and process the 3-D data, seismic interpreters have identified untested fault blocks, stratigraphic plays, and deeper pool potential. The fields can now be more completely and efficiently developed.

INTRODUCTION

Between 1984 and 1987, western Geophysical Company acquired and processed three 3-D seismic surveys for Gulf Oil Company in the following producing oil fields offshore northwest Niger Delta : Malu-Parabe, Okan, and Mina-Meren-Ewan (Fig. 1).

The first 3-D survey was conducted between August 1984 and March 1985 (processing inclusive) in Malu-Parabe fields using air gun sources and streamed cable. About 4266 mi (6,865 kID) of 4800% seismic data were acquired [equivalent to approximately 116 sq mi (300 sq kID)] in Malu-Parabe fields located in water depths varying between 20 and 100 ft (6.1 to 30.5 m). To date, a total of 61 wells have been spudded in these two adjoining fields which have been producing oil since 1971.

The second 3-D survey was carried out between December 1985 and January 1987 (processing inclusive) in Okan field located in 10 to 60 ft (3.1 to 18.3 m) water depth, using a radio telemetric acquisition system with airgun sources. Okan is a giant oilfield, and is the oldest field in Gulf's concession offshore Niger Delta. To date, 76 wells have been spudded in this field and it has been producing oil since 1965. The 3-D survey also encompassed parts of Mefa and Delta South fields which adjoin Okan field to the southwest and northeast respectively. The size of this survey was 96 sq mi (250 sq km) with a nominal fold of coverage of 4400%.

The third survey, which is the largest, embraced three field areas called Mina-Meren- Ewan. The water depth in Mina-Meren-Ewan area varies between 10 ft (3.1 m) and 80 ft (24.4 m). A similar but slightly modified radio telemetric shooting technique as was used in the Okan 3-D survey was applied to the Mina-Meren- Ewan area. About 154 sq mi (400 sq km) of 3-D data were successfully acquired in this area between November 1986 and May 1987 with 6000% multiplicity.
An Intercomparison of Measured Wave Grouping Parameters During a Storm
Authors: McCarthy T.J.
Published: October 2008

This paper describes the results of a wave measurement experiment carried out at the Kinsale Head Gas field, off the South coast of Ireland between 21 and 23 November, 1984. Simultaneous wave recordings, of length up to two and a half hours, were made using wave buoy and wave staff devices. These recordings include the growth, peak and decay of a severe winter storm.

A comparison is made between the wave parameters obtained from the two devices. This includes first order wave spectra and their derived height and period parameters as well as the most commonly used wave grouping parameters.

The characteristic wave height and periods show good correlation between the wave buoy and staff while the chief grouping parameters demonstrate weaker dependence. The spectral peakedness parameter gave the strongest correlation but the mean run lengths were virtually un-correlated between the two locations. Each system gave similar values for the auto-correlation between successive wave heights with a weak but significant relationship. The Funke and Mansardgroupiness factor 1showed an even weaker dependency. This was slightly improved by employing a new modified factor. The agreement between SIWEH spectra was dependent on the length of the wave record.

1. INTRODUCTION

With the development of compliant and floating oil production systems, wave groups are increasingly important to offshore engineers. Many authors have demonstrated the relationship between the slow drift motions of moored floating structures and the presence of wave modulation due to groups. Despite this relatively little is known about the occurrence of wave groups during storms.

Attempts have been made to characterize nonrandom behavior of waves under two broad categories. Firstly, wave groups have been described in terms of the dependency of successive wave heights. The second category is the study of low frequency modulations of the sea surface.

The former may be described as counting methods, wherein the wave heights are discretized and examined as a series of statistical events. The most common definition of a wave group is a run of consecutive waves whose heights exceed some threshold value. Figure 1 demonstrates this definition showing two wave, groups of length 3 and 4. Goda considers the mean run length of a record for threshold values of Hs ' the significant wave height, and Havg, the average wave height. Goda also demonstrated that the individual run containing the largest wave of the record is on average longer than other wave groups. This particular wave group is termed the "extreme wave group" (EWG) and has been proposed as a design criterion for capsize tests.