bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploration 3D: A New Tool Of Cost Effective Information For Offshore Prospects
Authors: Ritchie W. , Major J.T.
Published: October 2008

The present industry climate magnifies the need for lower finding and developing costs for new reserves. With most of the larger new non-OPEC reserves expected to be found offshore, involving high costs and heavy front end investment, improved information to reduce risk in the offshore arena is critical. The 3D seismic system has clearly demonstrated its value in the post-discovery stage. A cost-effective extension of this concept applicable to the pre-discovery stage is now available. The Exploration 3D method provides:–earlier, better quality information to locate potential reservoirs.–reduced cycle time to production–equivalent cost to alternative conventional seismic methods

The role of Exploration 3D is discussed for the Gulf of-Mexico environment.

INTRODUCTION

Over the last 15 years, the oil market has undergone, and continues to undergo, major structural changes. Worldwide oil demand has fallen from its 1919 peak of 51.2 million barrels per day (mbd) to 44.7 mbd in 1983. On the supply side, higher oil prices spurred non-OPEC production growth from 35% of worldwide production in 1973 to 56% in 1983.

The reserves from which non-OPEC production emanates have been found mainly offshore in the recent past and most experts believe the bulk of significant new non-OPEC reserves will continue to be found offshore.

Today, in the presence of severe price pressures and declining reserve bases, oil companies are thus faced with finding new reserves in a high cost, high risk offshore environment where 26% to 41% of future oil demand is projected to lie.

The costs at stake are significant in the offshore environment. Table 1 shows the cost relationships of the major expenditure segments. Drilling and structures account for approx 70% of total expenditures or $26 billion in 1984, projected to grow to $40 billion over the next three years. The U.S. share is projected to grow from 20% to 25% over this same time period.

The introduction of tools which have a direct impact on time and cost effective utilisation of drilling equipment and structures becomes, therefore, ever more important. We will discuss a new tool, Exploration 3D, which directly supports and expedites the decision processes by providing cost effective, timely quality information to the oil company at the stages when it can be of most value.

GULF OF MEXICO ENVIRONMENT

The brightest spot for increasing U.S. reserves is in the Gulf of Mexico. In addition to maturing areas offshore Louisiana and Texas, the flexure trend in the Gulf of Mexico's deeper waters is growing in attractiveness. The role and use of Exploration 3D will be illustrated in the Gulf of Mexico environment.

In the last five years, 3200 offshore tracts have been leased. With the advent of area-wide leasing in 1983, independents as well as the majors have participated in the Gulf of Mexico search.
Corrosion Reduction In Production Tubing With the Aid Of ,A Phase Equilibrium Model
Authors: Reinhardt J.R. , Powell T.S.
Published: October 2008

A model is described which predicts where the corrosion of production tubing, due to condensed water in gas condensate wells, is most likely to occur. The prediction is made by combining flash equations and thermodynamic equilibrium principles within a computer algorithm for use with a personal computer.

INTRODUCTION

Corrosion attack of the production tubing of a gas condensate well may cause the tubing to fail at an unexpected, early date. The tubing could then be replaced but at considerable expense due to the unscheduled workover and the loss of production.

One of the major factors-for corrosion is liquid water being in contact with the surface of the tubing (1). The liquid water allows small electrical circuits to be completed between small anodic and cathodic areas on the surface. The small anodic areas are the surface areas being dissolved (i.e., corroded) and this reduction of the thickness of the tubing wall leads to tubing rupture.

Many other factors are also important for corrosion to be possible. One factor is that some component, such as hydrogen sulfide, is reduced in the water to give an aqueous solution which can transport the electrical charge. Another would be the actual contact of the liquid water with the surface. The relative amount of condensed hydrocarbon may prevent the condensed water from effectively contacting the surface. A volume ratio of liquid water to liquid hydrocarbons of about 0.3 is believed necessary before the vertical tubing surface becomes sufficiently water-wet so that corrosion is possible (2).

The purpose of this paper is not to look at all the factors which contribute to corrosion, but to present a model which predicts where the tubing could become water-wet. Once this zone of tubing is identified, the corrosion engineer may decide what actions to use to reduce the potential for corrosion. Some suggested actions include:using a more corrosive resistant tubing through this zone,injecting an inhibitor below the zone to place a protective coating on the tubing surface, andinjecting an additive below the zone to change the phase equilibrium so that water-wetting is not possible.

THEORY

The first step in developing the model is to imagine that the entire length of the production tubing is divided into sections as seen in Figure 1. Each imaginary section is then considered to be an individual flash chamber. The entire length of production tubing is, thus, replaced by an imaginary string or stack of discrete flash chambers. The flow streams leaving each flash chamber are recombined into a single stream that becomes the feed stream for the next flash chamber. This system of separated and recombined streams continues up through the total stack of flash chambers. The stack of chambers could be extended to include the flash across the perforations at the bottom of the well and the primary separator at the surface.
Open-Sea Terminal In Hostile Environment
Authors: Koman B.
Published: October 2008

A ship loading terminal near Punta Arenas, the southernmost city of the world (53 ° -10'S, 70 ° -54'W) is described. Strong winds, choppy seas, frequent gales, rain and snow make it difficult to load ships at an offshore berth in this area. Detailed site investigations, including a wind recording program, supplied sufficient information for the analysis of operating conditions. The weather pattern of the entire region, including the predictability of gales, was utilized in the analysis. The results showed that a bulk loading terminal at this location is feasible, provided that the design takes into consideration the specific problems of the site. The final layout shows a terminal that can be approached from several different directions, depending on the direction of the wind. The mooring system-is arranged to allow alternative ways of attaching and casting off mooring lines and executing docking and departing maneuvers.

The berth is supported on piles and contains the minimum of structures, relying on a slewing ship loader to reach the ship in any position, with only limited fore and aft shifting of the vessel for loading the extreme hatches.

Results of wind recording, statistical analysis of wind and wave data, operating criteria and the results of berth availability analysis are included in the paper.

INTRODUCTION

Construction of a terminal capable of loading 3 million tons of coal per year into 60,000 DWT bulk carriers was a basic condition for opening the Pecket mine near the southernmost city of the world, Punta Arenas, Chile (Lat. 53 ° -10' South, Long. 71° -54' West). The only location close enough to the mine to allow economical transportation is on the eastern shore of Otway Sound, a large body of water accessible from both the Pacific and Atlantic Oceans via the Strait of Magellan and the Geronimo Channel (Fig. 1). This area is exposed to prevailing onshore winds that often reach gale force, generating choppy seas and heavy surf. Summer rainstorms and winter snowshowers occur with considerable frequency.

OCEANOGRAPHIC AND ATMOSPHERIC CONDITIONS

Otway Sound (Fig. 2) covers 2,750 square kilometers (800 square nautical miles). The fetch of open water over which waves can be generated by the prevailing westerly winds is approximately 37 kilometers (20 nautical miles).

The weather pattern of the region is dominated by the large Pacific Ocean air masses whose eastward flow is obstructed by the Andes mountain range. Being forced south, these masses burst through the Strait of Magellan area with explosive force. As a rule, gale or near-gale force winds blow for several days, followed by a calmer period before the next gale. During the Southern Hemisphere summer the gales occur with greater frequency than during the winter. The arrival of these strong winds can usually be predicted several days in advance, from simultaneous readings of the atmospheric pressure at two or more meteorological stations located hundreds of miles apart.
Reliability of TLP Tethers Under Maximum and Minimum Lifetime Loads
Authors: Harding S.J. , Banon H.
Published: October 2008

This paper describes reliability analyses which were performed to determine the adequacy of TLP tether maximum and minimum tension design criteria. Reliability analyses for other potential tether failure modes such as fatigue were not performed. The calculated reliabilities were compared to typical calculated reliability levels of steel piled jackets. The effect on tether loading of vertical wave impact on the underside of a TLP deck was also considered for the maximum tension case. Tether load analyses were performed using frequency domain analytical tools and reliability was calculated using the advanced, first order, second-moment analysis technique. A probabilistic methodology for combining time-variant and time-invariant tether load components was developed. The results of the study are limited by assumptions discussed in the paper.

INTRODUCTION

The present economic climate in the oil and gas industry encourages the search for low cost deepwater production systems. One of the challenges in the evaluation and development of such systems is establishing criteria which lead to safe, but not overly conservative designs. Since little or no actual service experience exists for new concepts, a probabilistic reliability analysis is a means of calibrating the design criteria. This is accomplished by comparing the calculated reliability of the new structure with that of conventional offshore structures which have demonstrated their safety over time.

The subject of this study is the Tension Leg Platform (TLP). The TLP, Figure 1, is a deepwater production system that has a semisubmersib1e type hull and integral deck permanently moored to the ocean floor by tethers which are kept in tension due to excess buoyancy of the hull. The tethers are the most novel and also the most critical feature of the structure.

There are several potential modes of tether failure. The two studied here are maximum tension in which the tensile capacity of the tethers is exceeded, and minimum tension, in which loss of tension leads to unacceptable stresses caused by retensioning or excessive tether bending. While the TLP can still function properly with a tether damaged or removed, it is not known how much damage a ruptured tether falling to the ocean floor could cause to risers, adjacent tethers or foundation and well templates. In this paper, failure of the TLP system is defined as failure of one tether. Reliability analyses for other failure modes such as fatigue, which was not critical for the Gulf of Mexico application being studied, were not performed.

TLP TETHER LOADS AND DESIGN CRITERIA

TLP Description

The TLP analyzed in this study was designed for 762-meters (2500-feet) of water in the Gulf of Mexico. It has a square, four-column, symmetric conf1guration with circular columns and square pontoons. The pontoons have rounded edges. The displacement is 52200 mt (57540 st) and the platform weight is 34330 mt (37840 st). The column center-to-center span is 62.8 meters (206 feet),
New Global Earth Model and Seafloor Gravity Analysis for Offshore Exploration
Authors: Kim V.E.
Published: October 2008

An improved seafloor gravity analysis for offshore exploration is developed using a new global Earth model (NEWGEM) based on exact solutions of the ellipsoidal layer model of the rotating Earth with local and global corrections. The new analysis is expected to be capable of extracting more reliable in situ mass-density profiles under the seafloor since it uses many available geophysical data such as sea surface gravity and seismic surveys as well as seafloor gravity and bathymetric surveys.

INTRODUCTION

Presently, it is customary to select offshore exploration drilling sites based mostly on seismic data analysis. Gravity surveys are not used as extensively as seismic surveys, primarily because gravity analysis is not developed to its full capabilities and sensitivities. In this report, a new gravity analysis method is described to remedy the above situation.

The new analysis method is a hybrid interactive method involving both partial inversions of gravity survey data and forward modeling of density profiles and uses interactive graphics and expert systems. The new method is complementary to the existing seismic analysis methods, since it uses the results of the seismic and geological surveys. The new analysis is expected to give an improved in situ mass density profile under the seafloor from seafloor gravity surveys and other surveys. In particular, it will be extremely useful when a choice for the final site is to be made from several potential sites determined from seismic and other surveys.

NEW GLOBAL EARTH MODEL (NEWGEM)

Some knowledge of the mass distribution in the interior of the Earth is emerging from seismic studies4,5 and rather detailed knowledge of the Earth's crust and surface is becoming increasingly available in many places. Therefore it is desirable to introduce a new physical representation of the mass distribution for the entire Earth which can be refined to accommodate new and more accurate data as it becomes available and which can describe many different component properties and processes of the entire Earth system on both global and regional bases. A new global Earth model (NEWGEM)1.3 has been recently proposed to provide a unified description of the Earth's gravity field inside, on, and outside the Earth's surface using the Earth's mass density profile as deduced from (1) seismic studies,. (2) elevation and bathymetic information, and (3) local and global gravity data. Using NEWGEM, it is possible to determine the constraints on the mass distribution of the Earth imposed by gravity, topography, and seismic data. Seismic studies indicate that the Earth has a concentric shell structure with deeper shells having larger mass densities. This structure of the Earth is summarized in the Preliminary Reference Earth Model (PREM).4 PREM defines the Earth as consisting of eight principal layers. It specifies the thickness of each of these layers and give polynomial expressions for calculating, as a function of radius, the density in each layer.
An Analysis of Piles in Marine Clay Under Cyclic Axial Loading
Authors: Wathugala G.W. , Desai C.S.
Published: October 2008

A finite element procedure based on the Biot's theory for dynamics of porous media is developed to analyze nonlinear soil-structure interaction problems including pile foundations. The method is verified by back predicting field behavior of cyclic axially loaded instrumented pile segments, tested in a saturated marine clay, near Sabine Pass, Texas, in collaboration with Earth Technology Corporation (ERTEC), Long Beach and Houston. .'A new and advanced anisotropic hardening constitutive model is' developed based on laboratory tests on undisturbed samples from the site. For the preliminary analysis presented here, a simplified, associative version of the model is used.

INTRODUCTION

Pile foundations are common in offshore structures. Wave forces on these structures create cyclic axial, lateral loadings and moments. Proper understanding of the soil-pile interaction under these loadings is important for the safe and economical design of foundations for these structures. In this paper, the case of only axial cyclic loading is considered.

Most of the available methods for analysis of pile-soil interaction problems under cyclic loading are based on highly simplified (often one-dimensional) idealizations, and similar simulations for soil behavior; popular semi-empirical methods such as the t-z curve approach are among these methods. These methods may not provide an insight into the soil behavior, and pore water pressure development around the pile.

A finite element procedure based on the theory of dynamics of porous media is developed and verified by backpredicting the field behavior of an instrumented pile segment under cyclic axial loading. The proposed procedure allows for axisymmetric idealization including coupled soil-fluid interaction and a new and generalized constitutive model for soils and interfaces. It allows for spatial and time dependent computation of displacements, stresses and pore water pressures around the pile. The proposed procedure can provide enhanced understanding of the response of the pile problem, and can lead to improved procedures for analysis and design of such soil-structure interaction problems involving dynamic loading.' This research is unique in the sense that it integrates modeling, laboratory tests for soil behavior and field verification.

DYNAMICS OF NONLINEAR POROUS MEDIA

Deformation of saturatl3d soil s under dynamic loading consists of deformation of soil grains, deformation of the soil skeleton, compression of water and movement of water through pores. The main contribution to the overall deformation is from the soil skeleton, and due to the movement of water through pores. Deformation of the soil skeleton is governed by effective stresses and is modeled using a new plasticity based constitutive model. Movement of water through pores is modeled using the well-known Darcy's law.

Detailed review of the theory or dynamics of porous media is beyond the scope of this paper; references present this theory, and reviews of relevant developments and applications.
Post Driving Prediction of Pile Capacity
Authors: Porter B.W. , Ingram W.B.
Published: October 2008

Because soil is a heterogeneous media, pile installation response does not always proceed according to plan. When driving performance variability occur, the capacity of the piling must be determined and the cause of these discrepancies analyzed. Procedures for evaluating available soil borings, geophysical information and pile driving records to determine pile capacity are detailed.

BACKGROUND

During installation of a four pile jacket in the East Cameron area of the Gulf of Mexico, difficulties were encountered in reaching the design penetration of 323 feet. Piles 1 and 4 reached refusal after the final section was added when driving with a Menck 3000 hammer. A Menck 7000 hammer was tried on pile 4 and also met refusal. The typical definition for refusal used by installation contractors for a Menck hammer is 150 blows per foot for five feet or 250 blows per foot for restarting a pile. This definition differs form the API RP 2A(Ref. 1) recommendation of 300 blows per foot for five consecutive feet or 800 blows for one foot of penetration. This lower blow count for refusal is favored to prevent damage to the hammer which can be caused by excessive pounding with the hammer. In this paper the former definition for refusal was used.

Adding the final section and driving to refusal gained less than 10 feet of additional penetration and left a weld joint at a poor location for proper connection to the jacket. It was decided to drive piles 2 and 3 and to terminate pile driving after installation of the fourth section at a penetration of about 258 feet. This final penetration would leave the heavy wall pile section high in the profile, but in an acceptable location to provide the design lateral support because of proper underdrive design. The predicted pile capacity based on the nearby boring provided a capacity of about 5400 kips. This capacity of 5400 kips was sufficient for minimum design requirements but a determination of the as installed capacity consistent with normal design procedures was required to determine maximum allowable loading conditions. Final pile penetrations (measured from the seafloor) for piles 1,2,3 and 4 were 268.5, 259, 258.5 and 263.5 feet respectively.

QUESTIONS TO BE ANSWERED

The difficulties during installation on this project raised several questions on the design and installation of a jacket. The questions that were asked of Seafloor Engineers as geotechnical consultants and are addressed in this paper are as follows:What is the pile capacity of the piles in their as built condition?Based on a review of the boring log near the location, no driving problems were anticipated. Why did driving problems occur?
FulI-Scale Load Test of Pile Gripper for Bullwinkle
Authors: Digre K.A. , Kenney J.J. , Simic R.A.
Published: October 2008

A full scale load test was required on a prototype pile gripper as part of its performance specifications. The test was conducted on a fully instrumented 84 inch diameter by 2.25 inch wall thickness, A572 - Grade 50 steel pile held in place by the gripper. Loading was increased in steps to a value of 7,50O kips. The test was successful and the prototype unit (one of four) was installed on the 1363 feet water depth Bullwinkle jacket. The four units were utilized during the platform installation, securing and stabilizing the jacket before grouting the "pin" piles and further pile driving.

INTRODUCTION

Pile grippers are constructed similar to grout packers. Each unit contains two inflatable inflatable actuation elements (nylon-reinforced rubber bladders) which force independent sets of flexural gripping members (steel fingers with machined teeth) against the surface of the pile. The entire unit is enclosed by an external steel containment cylinder. Grippers are usually mounted on %p of corner pile sleeves and serve as temporary structure to pile connections. Normally only used on an all skirt pilled jacket, their primary purposes are to provide some level of early resistance to storm loading and to prevent relative movement between the pile sleeves and piles during the time the permanent jacket to pile connection, consisting of grout, is setting and gaining its initial strength. A secondary purpose of the units comes in to action if a structure is set down or loaded such that it becomes out of tolerance with respect to levelness, Specific corners can be secured to a pile after adjustments are made and before installation of the other piles.

As platforms were located in progressively deeper water, it became desirable to develop a fast method of attaching "pin" piles to help the temporary foundations (mudmats) in resisting loadings during installation. Attachment of piles penetrating only under their own weight would even be of great assistance. In the extreme, with as little few as one pile driven to adequate penetration at each corner, design events could be tolerated, reducing risk,

In the design of the Bullwinkle platform, reduction of installation risk was a prime concern. A two-piece jacket was even considered (Ref. 1). The planned June installation could not be assured five years in advance, Early analyses indicated the jacket with no conductors installed, most legs still buoyant and no deck loading could safely survive major hurricane waves with only one pile driven to design penetration at each corner. The maximum pile load which could be resisted immediately after driving (50% of the design ultimate) was predicted as 7,600 kips compression or 5,000 hips tension.

Shell had experience using grippers on two projects, platform Eureka a 700 feet water depth structure installed offshore California and the Boxer platform (Ref. 2) installed in the Gulf of Mexico in 750 feet of water. Eureka had four 1,000 ton units for 60 inch diameter piles.
An Alternative FPS Concept for Offshore Oil Production
Authors: de Paiva Leite A.J. , de Freitas J.F. , Correa da Silva R.M.
Published: October 2008

The discovery of giant deep water fields in Campos Basin pushed Petrobras towards seeking solutions which, in a simple and economically feasible way, would enable their exploitation.

Among several alternatives, a semi-submersiblebased system using rigid risers and dry production trees stands out, combining the simplicity of a semi-submersible with the advantages of a TLP.

The concept is developed bearing in mind the mild environmental conditions encountered off the Brazilian Coast and incorporates several original features. Amongst others, the modular deck arrangement, in addition to the unit's dimensional limitations, allow it to be fully built in a Brazilian dry-dock, reducing construction costs and schedule.

INTRODUCTION

In the wake of the first oil crisis in 1974, many countries were motivated to increase domestic production in order to diminish the amount of imported oil. Within a short time, some fields which before were not economically feasible, became attractive as the international price of crude peaked up.

In Brazil, the need for hard currency reinforced this tendency as it became of utmost importance to substitute domestic production for imported oil in the shortest time. The Early Production System (EPS) alternative fulfilled these demands quite well.

In august 1977, the EPS "Enchova I" started producing oil in 125 m water depth. Installed on a SEDCO 135 type semi-submersible, the system started with 10,000 bopd from one well, flaring the gas (see figure 1). At that time, some principles of the concept presented in this paper (from now on referred to as "Minimum Heave" concept) were applied, as the well was produced through a rigid riser (marine riser), although using a marine BOP and a flow head connected directly to the travelling block. This system allowed a 18 feet vertical displacement and was kept active for 3 years.

Other EPS's that came after "Enchova I" also had one well producing through a rigid riser. The longest record for this kind of system was the well RJS-218, Parati /Anequim field, in 107 m water depth, with 5 years of continuous operation. During this time, no marine riser disconnection caused by bad weather has been registered in any of these EPS's.

These historical records form a base upon which the minimum heave concept can rely, as they attest the mildness of the environmental conditions in Campos showing that a semi-submersible with dry production trees is perfectly feasible for the area, from a technical point of view. More than that, they suggest that the size of such a unit could lie in a range well under the size of similar ones for the North Sea or the Gulf of Mexico, where environmental conditions are quite harsher.

Provided that the size of the platform is kept within certain limits, the technical and economical advantages of the concept are evident and one of the company's goals at the moment is namely to design one tailor-made for the Brazilian conditions.
New Mechanism in Drillstring Vibration
Authors: Lin Yao Qun , Wang Yu Hwa
Published: October 2008

In deep well drilling for oil and gas, it has been observed and recorded that severe vibrations build up and die down periodically. The beating phenomenon is a frequent occurrence, particularly, during all startup tests and on most of those exhibiting the low frequency torsional vibration. This paper interpreters the field data of beating like phenomenon and reveals a new mechanism, namely stick-slip vibration, which may initiate three-lobe pattern at the hole bottom. The possible self-excited vibration without sticking is also explored in this paper.

INTRODUCTION

The external excitation on the drill bit is usually regarded as the sole cause of the vibration of the drillstrinq. Paslay and Bogy considered the vibration due to the intermittent contact of the bit and the hole bottom in 1963 [1]. Huang and Dareing discussed the buckling and lateral vibration induced by the drill fluid in 1968 [2]. Bogdanoff and Goldberg presented a random model to explain the breakage of drill pipe in 1961 [3]. However severe vibration was usually attributed to the bit's running over the three-lobe bottom pattern at a constant speed, although the cause of the formation of the three-lobe bottom pattern was not understood [4,5,6]. Based on this attribution, Dareing and Live say successfully explained the longitudinal and torsional vibrations with triple rotary frequency in 1968 [5]. Dareing further indicated the possibility of eliminating the three-lobe bottom pattern by controlling the rotary speed in 1983 [7]. He also explored the self-excited vibration initiated by a small vertical harmonic motion of the bit [8]. Eronini et al investigated the interaction between the bit and rock and presented a dynamic vibration model in 1982 [9]. In analyzing field data, Dawson, Lin and Spanos postulated in 1987 that the drillstring vibration was a stick slip motion [10J; this was followed in a study by Kyllinstad and Halsey in 1987 [11]. By examining the beating phenomenon in oil well drilling, Lin and Wang demonstrated that the vibratory phenomenon of beating was a stick-slip motion. The effects of viscous damping, rotary speed and natural frequency of the drillstring on stick-slip vibration were also discussed [12].

This paper re-iteratesthat beating in drilling is induced by the nonlinearity of the total resistance to the drillstring (dry friction, viscous damping and torque on bit). This is done by further examining Denison's data and theory [13]. The formation of three-lobe pattern at the hal e bottom and self-excited vibration without the bit being stuck are also explored.

Summary OF PREVIOUS WORK

Our previous work was first concentrated on the large amplitude torsional vibration of the drillstring with bit off the bottom. The drill string was modeled as a one-degree-of-freedom torsional pendulum which has the following equation of motion

(MATHEMATICAL EQUATION IS AVAILABLE IN FULL PAPER)
New Approach for Installing Welded Conductors on Platforms Without Interrupting Adjacent Drilling and Production Operations
Authors: Lace N. , Fahrmeier C.F.
Published: October 2008

This paper describes the equipment and procedures used to install welded conductors on Shell U.K. Exploration and Production's Tern Platform located in 550 feet of water in the North Sea. The equipment and procedures which were used allowed conductors to be installed without interrupting drilling and producing operations. This method of installing conductors is more economical than conventional methods and allows conductors to be installed at a schedule dictated by the progress and success of the drilling program.

Introduction

The placement of conductors into offshore platforms can be divided into three separate operations defined as follows: 'Installation' refers to placement of the conductor down to a penetration in the sea-bed achieved by the conductor's own weight. 'Drive' refers to achieving further penetration by means of an impact or vibratory hammer. 'Drill/drive' refers to achieving further penetration by using a combination of drilling a lead hole and driving with an impact or vibratory hammer. This paper focuses on the equipment and procedures used in the 'installation' of conductors in the Tern platform, that is, to a penetration achieved by the conductor's own weight.

The placement of conductors in offshore platforms is typically accomplished with a crane barge during the installation of the platform, with the drilling rig as part of the drilling program, or with a combination of the two approaches. The choice as to which method to use is influenced by several factors:Cost of crane barge or drill rig spread vs. speed of installation. While crane barges typically have a higher day rate than drilling rigs, they can install several conductor strings simultaneously and can handle longer section lengths than a drilling rig.If the drilling and completion program is more successful than planned, several unused, but paid for, conductors which were installed by the crane barge will be left stockpiled in the platform.By making conductor installation part of the drilling program, the conductors can be installed in an "as-needed" basis, thus, there is no stockpiling of conductors in the platform.The increased speed of conductor installation by crane barges allows wells to be brought on-line sooner.

Conductors for the Tern platform were installed by using a conductor jacking spread provided by Marine Contractor Services, Inc. in conjunction with Varco-BJ Ltd. and adapted for use on the Tern platform by the operators Shell Expro, the Shell/Esso U.K. North Sea joint venture.

On the platform, the conductor jack was set up adjacent to the drilling rig as shown in Figs. 4 and 5. Because this equipment can operate independently of the rig, conductors were installed while drilling operations were ongoing.
A Practical 3-D Seafloor and Sub-Bottom Mapping System
Authors: Matthias P.K. , Newton F.L.
Published: October 2008

A new technique of applying three-dimensional rendering to an integrated product of side scan sonar, bathymetry and sub-bottom data has been developed. The computer generated products are displayed in stereo 3-D. The virtual product supports geologic interpretation, ROV operations and ocean engineering.

INTRODUCTION

The ocean sciences have been dramatically impacted over recent years by improvements in computer technology. High speed dedicated processors allow modelers to process comparatively large databases in a short amount of time. Large capacity data storage with fast access speeds support model interaction and revision. One major current challenge is to provide a user interface which supports interpretation through visualization.

Visualization allows modelers to view and manipulate data in spatial rather than numerical format and infer patterns and relationships based on the brain's interpretation.

This study culminated in the application of high speed computers and visualization software to display virtual products of side scan sonar imagery, bathymetry and sub-bottom data.

Side scan sonar's have been used to provide sonographs of the ocean floor since the early 1960's. This remote sensing device is subject to many radiometric and geometric distortions common to satellite remote sensing. Many of the same techniques are used for preprocessing to correct these distortions.

Manufacturers of side scan sonar have made gains toward correcting the radiometric distortions. The bulk of the geometric corrections and image extraction tools require coupling the sonar with a powerful top-side processor. Post-processing techniques used on the USGS MIPS system and Triton Technology's QMIPSTM have been described in the literature 1,2. Fig. 1 is a "typical" analog hardcopy of a sonograph over aircraft wreckage while Fig. 2 depicts a sonograph generated by Q-MIPS. Fig. 2 is an image of a PB4Y-2 aircraft imaged by International Deep Sea Survey with Triton Technology's Q-MIPS and the AMS-120 side scan sonar in Lake Washington, Seattle.

The lower third of Fig. 2 is a copy of the Q-MIPS display of port and starboard channels. After drawing a rubber rectangle around the aircraft, Q-MIPS zooms the boxed region to fullscreen. A color lookup table (LUT) and associated histogram are displayed across the top.

The Q-MIPS sonar image processing system digitizes the analog signal at up to 750 kHz. Slant range correction and water column removal are performed in real time. The data is stored on high density 1.25 GByte write Once Read Many (WORM) optical disks while it is displayed on the screen. Q-MIPS data format includes the storage of 1024 8-bit or 16-bit pixels per channel per sonar "ping".
Driven Model Piles Tested in Calcareous Sand in a Large Calibration Chamber
Authors: Parkin A.K. , Yee Y.W. , Tan C.P. , Willoughby D.R.
Published: October 2008

Model pile tests have been conducted in samples of calcareous sand, derived from both on and off shore sources in Australia. Samples 1.2 m diameter by 1.8 m high were formed and saturated in a large calibration chamber, modified to allow three piles to be driven into each sample. The silty fines created unique problems in sample formation and in creating a realistic test environment. Results of initial pull testing are discussed and compared with the CPT test.

INTRODUCTION

Carbonate soils found in Bass Strait, a major hydrocarbon producing region off the southeast coast of Australia, generally provide relatively poor support for driven piles [1]. Drilled and grouted piles [2] which provide extremely high skin frictions, upwards of 400 kPa, are now the preferred solution, but are datively expensive. In an effort to improve the cost effectiveness of grouted pile foundations, Esso Australia Ltd. conducted an extensive experimental program in 1987 and 1988 which included tests of 100 mm and 150 mm driven piles and grouted piles in a modified laboratory calibration chamber at Monash University, Melbourne. The tests were performed in three incremented carbonate soils that ranged in grain size from a medium sand to a sandy silt.

This paper presents descriptions of test equipment, procedures, and results of driven pile and cone electrometer tests performed in two of these soils, designated A and C. These were medium and silky sands, respectively. Results obtained in the sandy silt are reported in a companion paper[3]. Soil A was recovered References and illustrations at end of pare by dredging from a site in Bass Strait, while Soil C was derived from an on-shorn Tertiary deposit in South Australia. In respect of their compressibility and fines content, these soils differ notably from the clean silica sands normally used in calibration chamber studies, introducing severe problems in handling and sample formation, as well as causing notable differences in pile behavior.

THE CALIBRATION CHAMBER AND ACCESSORIES

The Monash University calibration chamber was developed from the design of a small chamber described by Holden [4], and was constructed solely for the purpose of calibrating friction cone electrometers in sand.

It consists essentially of a large triaxial sample of sand, 1.2 m diameter and 1.8 m high, enclosed in rubber membranes and compressed by a lateral water jacket and a base piston (Fig. 1). The exterior cell wall is of cavity consummation to permit the imposition of Ko lateral constraint, and the base piston acts through a water cushion for the measurement of vertical stress. An overhead reaction frame provides restraint to hold the cell together, and also mounts the driving equipment for a standard cone electrometer on the sample axis. Further details are given by Chapman [5], Bellotti et al. [6] and others.
Development of a Backup Control System With a Serial Hydraulic Data Transmission System and a Subsea Multisensor System
Authors: Okamoto K. , Nakagawa O. , Himuro H. , Tsugaki S. , Ihara M.
Published: October 2008

A highly reliable control system for sub sea equipment had been jointly developed by Kawasaki Heavy Industries, Ltd. (KHI) and Japan National Oil Corporation (JNOC) from 1985 for 4 years. This system has a multiplexed electro-hydraulic system as a main control system and a serial hydraulic data transmission system as a backup control system.

This Prim presents the following two subsystems and a device as part of the developed total control system shown in Fig. 1.Serial hydraulic data transmission systemSub sea multi-sensor systemUnderwater power generating unit

INTRODUCTION

As a backup control sys tern, a direct hydraulic System and a sequential hydraulic System are very popular in the sub sea control system for an offshore oil production. However the reliabi1ity of data transmitting capabilities is very poor compared with a main control system such as a multiplexed electro-hydraulic system. To improve the capabi1ities a serial hydraulic data References and i 1lustrations at end of paper. transmission system had been developed, which is an application of pressure propagation in pipe lines with pulse code modulation.

A sub sea multi-sensor system had been developed by applying LAN(Lcml Area Network) technique and power 1ine carrier's technique. I t consists of analogue sensors, digital sensors, one loop data way (parallel two-core cable), inductive connectors and control unit,

An underwater power generating unit had been developed to supply electric power to control pods when main electric power fed from a surface platform failed. This unit is driven by hydraulic w fed by hydraulic pumps located on the surface platform,

The design conditions for this control follows, which are comparable to those offshore oi1 fields.Environmental conditionWater depth : 300mWater temperature : +0--35°CVibration : 2-13.2Hz ± 1m13.2--8OHZ 0,7GProduct ion conditionPressure :max.350kgf/cm2Temperature:0-100°CHydraulic fluidMaximum pressure : 210kgf/cfiWorking fluid : seawater based fluid or seawaterTemperature s ()-29°CElectric power in control podAC source : AC100V ± 15%, 60Hzf ± 10% 3 phase or single phaseDC source : DC 24V+20%-10%

SERIAL HYDRAULIC DATA TRANSMISSION SYSTEM

This hydraulic data transmission system was confirmed to lx applicable to a floating type production system by empirical tests with scale models.RequirementData transmitting between quite a distance is possible as several thousand inters via a hydraulic 1ine.Additional equipment and components are minimized in comparison with a sequential hydraulic SystemA Hydraulic power unit designed exclusively for operation of gate valves and choke valves can be uti1ized for generation of pressure waves without any modifications.
Takula Oil Field and the Greater Takula Area, Cabinda, Angola
Authors: Dale C.T. , Lopes J.R. , Abilio S.
Published: October 2008

The Greater Takula Area comprises four offshore fields, Takula, Wamba, Numbi, and Vuko that produce oil predominantly from Upper Cretaceous reservoirs. The fields are located approximately 40 kms west northwest of the Malongo terminal, in Cabinda, Angola in water depths of 50-75 m (150-220') (Figure 1). Current production levels are approximately 177,000 bpd of 34° API oil.

The first oil well in the area was drilled in 1971 on a seismically defined horst structure beneath a pervasive salt section that is associated with the opening of the South Atlantic. It flowed 5600 bopd from carbonates of Lower Cretaceous age. It was not until late in 1979, however, that a far more significant hydrocarbon accumulation was found in the Cenomanian sands of the Vermelha Formation. All four fields produce primarily from Vermelha sands deposited on a trend of structures whose genesis was controlled by listric normal faulting and salt movement. The total area of closure for these fields at the Vermelha level is approximately28,000 acres (114 sq km) with a maximum oil column of 440'.

To optimize the oil recovery from these fields a staged development project has been ongoing since 1980. It involves initial primary solution gas and/or gas cap expansion drive production, followed by a water flood pressure maintenance program for the major reservoirs. This project has been guided by a detailed reservoir analysis using 3-D seismic, core studies, wire line log analysis, reservoir mapping and simulation matched to production history. To date these fields have produced 300 MMSTB.

Exploration History

The Cabinda Gulf Oil Company started exploration activities in the then Portuguese administered province of Cabinda in 1954. On November 22, 1957 the original concession covering both onshore and offshore acreage was awarded. By the early seventies the concession had been renegotiated to the current 10,116 sq km with the relinquishment of the onshore and additional acreage offshore out to the 200 m isobaths. The present concess ion is divided into three areas - A, B, and C. All the current production comes from Area A fields. (Figure 1).

The first well was drilled offshore in 1966. The discoveries of the Malongo fields followed soon after. These successes focused exploration on the offshore. By today, 14 fields have been discovered and put into product ion, the 1argest of these fields being Takula.

Regional Setting

Angola lies midway along the length of the South Atlantic rift. The rift developed in late Mesozoic time as plate tectonic activity caused the separation of South America from Africa. The tectonic elements and sedimentary sequences observed along the margins resulted from the evolution of the rift. (e.g., Lehner P. and DeRuiter, P. A. C., 1977). A series of basins developed along the rift. The Cabinda concession is located in the Congo basin which is flanked to the north and south by the Gabon and Cuanza basins, respectively.
The Veslefrikk Transfer Systems
Authors: Bjelland O.
Published: October 2008

This paper is a description of the Veslefrikk transfer systems which are the connections between the permanently installed fixed wellhead platform and the floating production platform on the Veslefrikk field. The main elements in the system are a 40 m long telescopic bridge and a number of 150 m long free hanging flexible pipes and electrical cables transferring fluids, power and control signals. The transfer systems operational and design requirements are addressed as well as a general description of the system design and analysis.

INTRODUCTION

The Veslefrikk field development consists of a jacket wellhead platform (VFA) and a semisubmersible production and quarters platform (VFB). VFB is moored close to VFA and the normal operational distance between the two platforms is 36 m. The water depth at the Veslefrikk location is 174 m.

The major system split between the two platforms and location of main equipment are as follows:

VFB:Process facilitiesPower generationLiving quartersWater injection SystemGas export compressor systemCrude export pumping systemGas lift compressor systemMud pits and cleaning systemMud pumpsCement pumps VFA:Wellhead systems for production and water injection wellsmanifold systemDrilling derrickConnections for gas and crude export pipelinesPig launchersSale-shakers for primary mud-cleaning

Due to this system separation, a transfer system as shown in fig. 1 and fig. 2 is required between VFA and VFB compromising the following main elements:telescopic bridgeflexible pipe systemelectrical cable system The main function of the telescopic bridge 1S to connect VFA and VFB together for transfer of personnel working on VFA and support the connection lines for the utility systems on VFA supplied from VFB.

The flexible pipe system consists of pipes for transfer of production fluid from the wellhead and manifold system on VFA to the process facilities on VFB. Further, the system consists of pipes transferring produced oil and gas from VFB to VFA where the export pipelines for oil and gas are terminated. Gas lift and water injection are transferred from VFB to VFA through the system.

The mixing and pumping systems for mud and cement are located on VFB. Flexible pipes transfer mud and cement over to VFA and return mud back to VFB

The power generation plant and the main control centre are located on VFB. The electrical cable system transfers electrical power from VFB to VFA and control signals between the two platforms.

OPERATIONAL PHILOSOPHY AND REQUIREMENTS

Transfer system considerations Previous examples of floating platforms operating alongside fixed platforms were evaluated in the early Veslefrikk project study phase in 1986 to establish the feasibility of such a concept. The fixed/floater combination had been used on the Odin field in 1983 where a semisubmersible drilling rig provided drilling mud, casing, storage and extra accommodation facilities. Also a number of flotels had been in operation anchored close to a fixed platform to provide extra accommodation.