Certificate of Fitness

The governments of the countries adjacent to the North Sea area which have drilling activity in their waters have made it a legal requirement that certain standards will be met before drilling operations can begin. The first government to require drillers to meet its safety and performance standards was the British Government through its Mineral Workings (Offshore Installations) Act 1971. This act authorized the establishment of regulations for the certification of drilling units. The Offshore...

Short Duration Diving

The term short-duration or bounce diving (sometimes called nonsaturated diving) simply means that a man is pressurized for a relatively short period of time (usually less than one hour) and then decompressed in a matter of hours. Due to the short exposure to the increased pressure gradient, the diver's body has absorbed a relatively small amount of gas and his decompression can usually be satisfactorily completed in less than 24 hours. The term nonsaturated is really technically incorrect. Some...

The Equipment Problem

The subsea drilling and production systems used by the offshore petroleum industry have been designed as diverless systems. However, provisions are usually made so that diveTS could be used in case of emergency. A great deal of effective work has been done in depths up to 300 feet, and operational 600-foot dives from drilling vessels are considered well within the state of the art today. Many of the bell diving systems presently in use are 600-foot systems. Successful subsea drilling operations...

Frank J Wetzel

Insurance and its relation to a company's operation is a complex subject. This section will deal primarily with the more specialized types of insurance for offshore drilling contractors operating in both national and international waters. Insurance is largely separated into two main areas. First, there is protection against loss of life and personal injury to employees and members of the public and their property. Members of drilling crews operate complex equipment in all corners of the world,...

Strength for Different Criteria

Figure 6-9 shows typical curves for varying criteria. Rig owners and contractors have been using data such as these although classification and certifying authorities have not (to oar knowledge) used them. However, several offshore mobile drilling units have been classed in recent years for more than one set of operating criteria. Certification for operation of an individual unit in new locations can be much quicker if the unit is classed for varying criteria or if different sets of criteria...

Summary

To summarize, a new testing system has been developed for conducting formation testing operations on offshore wells as shown in Figure 5-5, The principal flow control valves in this new string are operated by pump pressure applied from the surface. For this reason, it is ideally suited for conducting formation testing operations from a floating type vessel or in a highly deviated hole where controlled pipe string manipulation is very difficult or impossible. For optimum protection of personnel,...

T R Reinhart

Dynamic positioning, the concept of remaining in one spot at sea without anchors, was originally proposed for the National Science Foundation Project Mohole to drill through the earth's thinner mantle underlying ultra deep 20,000 foot water depths. Although Mohole was canceled, dynamic positioning was used for several small core boats because it provided deep water mobility. The use of dynamic positioning on the Glomar Challenger in deep ocean coring helped bring discoveries adding to man's...

The Compression Barrier

Even if adequate proven decompression tables existed, diving deeper than 600 feet is further complicated by what can be described as the compressionbarrier. A diver's body begins to absorb the inert gas he is breathing as soon as the pressure starts to increase. Therefore, his bottom time is considered to start when pressurization begins. Since his dive is limited to a specific total time, any reduction in compression time leaves more time for useful work on the bottom. We know from experience...

The Crossover Point

Diving to 1000 feet is not one of the industry's major problems at this time. Our biggest concern is the depth range between 450 and 700 feet. This is where most of the deeper activity will be during the next two or three years. As we have seen, diving in this range will require the use of decompression schedules which are not well tested, and which will undoubtedly produce a high incidence of bends until they are empirically modified through experience. Therefore, jobs calling for diving in...

The Decompression Problem

A diver must decompress from depth according to a predetermined schedule so that the inert gases i.e., nitrogen and or helium) which are absorbed in the body under pressure may be released from the body tissues without the bubble formation which would cause decompression sickness or bends. The quantity of inert gas absorbed during a dive is a function of pressure (or depth) and duration of exposure (or bottom time). The total decompression time varies with the quantity of absorbed gases and is...

Tom R Reinhart

Reinhart is Manager of Research and Development for the Baylor Company in Sugarland, Texas, where he is involved with offshore instrumentation projects, oceanographtc systems, variable voltage power systems, ballast control systems, and data gathering and reduction processes. He has worked with dynamic positioning on the vessel Eureka and served as Engineering Manager for the Tom R. Reinhart work on Sedco 445. Mr. Reinhart holds patents for electrical, mechanical, and instrumentation...

Vessel Heading Reference

In addition to a position reference, a vessel heading reference is necessary (Figure 1-111 . Fortunately, existing standard marine gyrocompass systems fulfill this need very well. A sine-cosine potentiometer is driven by a repeater from the main gyrocompass. The sine-cosine potentionmeter is used instead of a 0-360 degree potentiometer to eliminate the zero to 360 degree full scale jump in output that would occur when the vessel is heading yawed about a true north heading. The gyrocompass can...

Highest Wave Heights

SHORT TERM T AND H ARE CONSTANTS LONG TERM. TANO Hyj ARE VARIABLES phase angles, and directions. The procedure used to describe this principle is shown in Figure 1-50. This superimposing of waves is usually done in two steps. First waves with the same direction but of different frequencies, heights, and phases are superimposed. The result becomes an irregular wave system with infinitely long crests (long-crested sea). The next step is to sum up several such long-crested wave systems with...

Ultrasonics Television Photography

From a technological standpoint, all of these services are well advanced and are far more valuable than many people realize. They extend the eyes of the diver to the topside engineer, technician or supervisor. Permanent records can be obtained and kept for later comparisons or documented evidence. Underwater application of ultrasonics is a proven means of nondestructive testing. Wall thicknesses can be measured to determine the degree of corrosion. Critical welds can be checked for cracks and...

Saturation Diving

The concept of saturation diving was introduced to the offshore oil industry in 1966. It was originally conceived to provide a more reasonable ratio of bottom working time to decompression time. For any given depth there is a maximum time beyond which the inert gas effectively saturates the body tis sues. Decompression time becomes a function of depth only. Saturation diving differs from short-duration by the fact that there are no decompression penalties for greatly extended bottom times. This...

Recommended subsurface equipment

Other factors which can govern the choice of testing equipment are the size and type of rig or platform on which the equipment will be located. Equipment such as burners is rigged differently on jack-ups as opposed to semisubmersibles or drill-ships, and domestic equipment is usually different from large capacity international testing apparatuses. Normally, for Texas and Louisiana Gulf Coast testing, a three to four thousand barrel per day fluid capacity and ten to twenty million cubic foot gas...

William L Clark

Clark is Product Manager of Drilling Tools for Hydril Company in Houston and is responsible for the market application of existing and new Hydril drilling tools and new product development. He has over ten years of experience in the application and design of drilling equipment. Mr. Clark has also served as an Instrumentation and Control Systems Engineer in the research laboratories at Stanford University. He is a member of SPE, AIME, and the Nomads and is a lecturer for training...

History of Diving

The story of hyperbaric diving begins with the first prehistoric breath-hold divers. The first recorded event took place in 415 B.C., when Greek warrior-divers destroyed a harbor boom at Syracuse. History indicates that open-bottom diving bells were also in use in the fourth century B.C. Interest in diving began to increase in the 1500's when diving systems of different types and of varying degrees of practicality were designed and constructed. Some were used to carry out surprisingly complex...

Air Diving Equipment

Self-Contained Underwater Breathing Apparatus (SCUBAJ Scuba equipment utilizes high pressure cylinders to store compressed breathing air. The air is supplied to the diver by means of a demand regulator which delivers the air at a pressure equal to the surrounding wateT pressure. The diver's exhalation is exhausted into the water. The advantages of scuba are horizontal mobility (because the system does not require any connections to the surface), portability as a result of its small size and wei...

Ralph G Mctaggart

McTaggart is President of ETA Offshore Seminars, Inc. and is Vice President, Naval Architecture, of FTA Engineers, Inc. in Houston, Texas. He has been working in the offshore industry since 1954 and has been involved in the design, analysis, certification, and construction of offshore drilling and production units. Mr. McTaggart is on the Special Committee on Offshore Mobile Drilling Units of the American Bureau of Shipping and is a member of the Society of Naval Architects and Marine...

Burners

Pollution Control International, or PCI, Inc., has developed a super oil burner. Along with Baker John Zinc burners designed in England, and the Flopetrol (subsidiary of Schlumberger) giant burner developed in France, it is designed to test wells without retentive storage and eliminate pollution. Basically, burners involve atomization and air mixtures to obtain, hopefully, 100 combustion. Designs and specifications vary for smokeless burns, and for volumes anticipated. The burners currently...

Offshore Drilling Support

In all probability, the one area where the contribution of the diver is most significant is in support of offshore drilling operations utilizing subsea completion equipment. This is especially true for foreign exploration operations, which are often done in remote or isolated locations. To a large extent, the diver can be compared with a local fireman. You hope you never need him, but when you do, you really need him. Basically, divers are utilized for the following tasks Check bottom and...

Darrell G Foreman

Darrell Foreman

Foreman serves as the Worldwide Sales Manager for Subsea Equipment with the Stewart and Stevenson Oilfield Division in Houston. He worked on the world's first deep water unit operating in 1,400 foot depths off California. Mr. Foreman also served as the Project Manager for the first acoustic blowout preventer system. Peter M. Lovie is President and co-founder of Engineering Technology Analysts, Inc. and is Senior Vice President of ETA Engineers, Inc. In Houston. He has experience in...

Pump and Separator Subsystem

This subsystem is designed to input energy into the produced liquid stream to improve flow rate and ultimate recovery from the reservoir. Figure 4-21 shows a model of this unit. The separator is a gas-liquid separator and no effort is made to separate the produced water from the oil in this process. The produced liquids provide a flooded suction for a bank of multi-staged centrifugal pumps. The pump discharge flows to the surface processing facility with a portion of the stream returned to the...

Tools and Special Equipment

The real value of the diver is shown in his ability to perform useful work underwater. Most of the diver's tools are the same as topside tools, with certain modifications to render some of them watertight. Pneumatic tools, saws, drills, jackhammers, rivet busters, and impact wrenches are commonly used. In addition to the equipment mentioned above, some of the more common diver tools are underwater cutting and welding gear, underwater lights, still and movie cameras, ramset tools, jetting...

Emergency Proceduresblowouts And Fires

In the case of an oil or gas well blowout, action should be designed to protect human life and control the disaster as rapidly as possible. Very often these catastrophic blowouts are accompanied by fire because ignition sources abound around a drilling floor. Secondary fire problems are caused by the use of ordinary combustibles on drilling rigs and or platforms. If a drilling rig is on location, all engines must be shut down and all feeder lines into the installation must be shut in. All...

Sup Joint Safety Valve Slip Joint

REVERSE CIRCULATION VALVE OPENED BY INTERNAL PRESSURE REVERSE CIRCULATION VALVE OPENED BY ROTATION CUSHION DISPLACEMENT VALVE PRESSURE CONTROLLED TESTET PCT WITH OPTIONAL OVER-PRESSURE CLOSURE - HYDROSTATIC REFERENCE TDOL -PRESSURE REFERENCE ALVE -FLOW CONTROL VALVE -8Y-P4SS VALVE 16. At least 2,000 lbs, of collars between slip joint and slip joint safety valve, 17. Break-off type reverse circulation valve.

Stability during

Wind Overturning Arm

This is expressed graphically in Figure 6-6. The unit must have an adequate inherent tendency to right itself in the water whenever it is heeled over by an external overturning affect. This is expressed in terms of a righting arm, GZ. Counteracting this internal self-righting effect are the external overturning effects acting 011 the unit, which typically are dominated by the wind heeling effect. The two rules of thumb used to ensure adequate stability are shown in Figure 6-6, as well as the...

The Analog System

The Caldrill

The first dynamic positioning controller, used in the Eureka, is shown in Figure 1-114, Since the loss of a core hole could be accepted from time to time, this first system had no redundancy or backup of any kind. The joy-stick in the foreground is used to directly control the surge and sway position when in a manual mode of control. When on automatic control, the joy-stick is not in the circuit and the set points in the three turn counting dials determine the position held. Separate three mode...

Flowline Pullin

Pull Bullnose Assembly

The unique LPS diverless flow-line pull-in system is a significant part of the entire program as flow-line installation is usually expensive and subsea connections normally require diver assistance. As pointed out earlier, the original flow-line connection for Shell Oil Company wets accomplished using a preformed line with external TFL loops pulled by a winch within the service capsule. With the horizontal wellhead cellar design, the flow line approaches the cellar from the ocean floor and is...

Mike Hughes and Larry Cushman

Diving can be defined as a method of transportation that allows a man to perform work in the ocean, or on the ocean floor. There are two basic ways men can work underwater. The first is pressurized or hyperbaric diving. With this method the man goes directly into the ocean, and is therefore continuously subjected to the increasing pressures of depth. The second method of diving is unpressurized or isobaric diving in which the man goes under water in an unpressurized sealed diving bell,...

Indications Of Blowouts

Drilling is usually accomplished with the imposition of a positive hydrostatic head larger than the formation pressure. A number of situations may be encountered which can alter this balance, as when the drilling mud weight is too low and formation fluids can flow into the wellbore. An abnormal pore pressure gradient, greater than the pressure of the mud being circulated, would likewise result in an upward flow. Drilling operations involving the raising and lowering of packed drill strings and...

Surface Support Vessel

Skirt Support Vessel

Work on the ocean floor would be impossible without support from the surface. The LPS surface vessel Figure 4-17 provides the power, life support, and communications needed to safely operate far beneath the sea. One of the support vessel's prime functions is to launch and recover the service capsule. Since the capsule is buoyant, it operates independently once it is in the water, using its built-in winch and the haul-down cable. When surfaced, however, it Fig. 4-17 Lockheed's surface equipment....

Template

Subsea Production Template

The template Figure 4-22 is the large tubular structure used to carry all of the subsea equipment to the seabed and to provide the alignment for connecting the wells and pipelines to the manifold. The template is designed to permit the subsea equipment to be preassembled and debugged on land before installation and then to be installed as a unit. The structure has sufficient strength and displacement to contain the preassembled equipment while being launched from a large barge, being...

Penetrator Valves

The heavier components of the Xmas tree, along with the disassembled parts of the TFL loops, are stored in the wellhead cellar during the setting operation so that these large items will not have to be handled in the service capsule, c Role of the Wellhead Cellar The wellhead cellar's primary function is to provide protection for the Xmas tree, its associated valves, and the well controls against the hostile environment of the ocean floor. It provides a one-atmosphere habitat for these...

Mais Direction Of Shortcrested Wave System

Offshore Drilling Rigs

The directionality function provides information on the dispersion of energy in the different long-crested wave systems used in simulating the short-crested wave system. The function normally used at DnV, shown in Figure 1-53, is defined by the following equation r, A basic assumption must be made in order to proceed using statistical tools. The response amplitudes to a wave system which may be described as a sum of a great numbeT of regular harmonic components are the sum of the responses for...

Response Ampl Wave Ampl

By applying H 2 instead of 5 in Equation 20 , we get The parameter, E, is related to the area beneath the wave spectrum curve by the following equation It may be easily shown that the following equation yields Fig. 1-55 Rayleigh distribution function. The distribution function may then be written The most probable largest wave height during the time interval, t, may then be calculated as

Exxons Submerged Production System

Exxon Company U.S.A. has developed a submerged production system SPS which has undergone extensive land testing. It is currently in the submerged test phase under 170 feet of water in the Gulf of Mexico 27 miles southeast of Grand Isle, Louisiana. The SPS consists of a massive template which supports a number of subsystems. Each subsystem is designed to perform a given function in the production of oil and gas from offshore fields. The system is capable of deep water operation and can be...

Hmi H Voil Vf

The average apparent wave period, T, is usually determined so as to give the most unfavorable response with due regard to obtaining reasonable wave steepness. This parameter is the most difficult to choose, and for the investigations performed so far it has been determined according to the above criteria. According to additional investigations now being performed, it seems that the period chosen is not as critical for this procedure as it might be when using a design wave. Long Term Statistics...

Offshore Mobile Drilling Units

Offshore mobile drilling units as we know them today are sophisticated pieces of machinery. However, this was not always the case. The original units were simply land rigs taken into shallow waters and placed on a structure for drilling. The same drilling techniques that had been developed on land were used on the first offshore rigs. These techniques worked for some time, but the need to drill in deeper waters created a new type of engineer the offshore structural design engineer. And along...

Stability and Moving

Jack Rig Spudcan Information

Stability is simply the ability of a rig to remain afloat. The subject of stability is further divided under the two headings of a Intact Stability and b Damaged Stability. For every rig, the designer or builder should furnish the rig owner with a Stability Booklet which, at a very minimum, should contain a Hydrostatic Properties , b Cross Curves of Stability, c Statical Stability Curves, and d Dynamic Stability Curves, Items c and d should be sufficient to cover the normal operating range of...

Chronology Of Submersible Rigs

Bethlahelm Jackup Rig

CHRONOLOGY OF JACKUP RIGS, 1953-1969 In 1955, the first 3-legged jack-up appeared on the scene Figure 1-6 . The rig was the R. G. LeTourneau jack-up, the Scorpion, for Zapata Offshore Company. The Scorpion, an independent leg jack-up, used a rack and pinion elevating system on a truss framed leg. The rig worked very successfully for several years but was lost during a move in the Gulf of Mexico. The Scorpion was closely followed by The Offshore Company Rig No. 54. For Rig No. 54, however, a...

Multiple Well Man foldProduction Station

Subsea Pile Template

The station consists of three basic hardware components the base, the wellhead connector assembly, and the subsea work enclosure. It also includes a number of associated supporting subsystems. A full-scale prototype has been constructed and tested. The prototype base Figure 4-6 is composed of structural piping and is about 50 feet square, 26 feet high. It weighs approximately 140 tons in air, with positive buoyancy in water with pipes unflooded. A circular base was designed to serve as a...

A Wave Length L Characteristic Length

Waves Length

Fig. 1-48 Yaw transfer functions, Aker H-3, HeadingJi 45 a Stationary Conditions Short term Statistics Stationary conditions do not imply that the ocean surface is constant or repeats itself, but rather that the statistical parameters are constant. An irregular sea such as that shown in Figure 1-49 may be described by linearly superimposing a gTeat number of regular waves with different frequencies, H WAVE HEIGHT T ZERO UPCROSSING PERIOD H. SIGNIFICANT WAVE HEIGHT- T AVERAGE APPARENT ZERO...

Submersible Work Vehicles

There are a number of small submarines on the market today. Depending upon the job, they can be very useful and effective. Most are expensive, but under certain circumstances they can provide the most economical means of accomplishing a task. Beyond diver depths, subs can be extremely valuable. Subs are used for salvage work, inspections, surveys and scientific assignments. 1. Dobbins, P., Undersea Operations ant Equipment, School of Offshore Operations Presentation, Houston, Texas 1972. 2....

The Manifold Center

Oilfield Flow Lines And Manifolds

The manifold center is designed to commingle production from several subsea wells, each in an LPS wellhead cellar, and deliver the mixed flow stream through a single pipeline to a nearby production platform or shore base. It serves the same purposes as a land-type production manifold as it permits study of an individual well's producing characteristics. It also provides the means to use TFL tools on any of the completions connected to the manifold. The prototype manifold center Figure 4-14 is...

Info

Particle Velocity Wave Equation

Fig. 1-57 Weibull distributions of visual wave heights. In determining the total wave forces on fixed offshore structures, the force on long, slender, cylindrical elements of arbitrary cross-section form is of great interest to the designer. The wave and current forces on these elements for in- PROBABILITY OF EXCEEDANCE Q l-P H PROBABILITY OF EXCEEDANCE Q l-P H Fig. 1-58 Predicted long term distributions of wave heights. stance, piles may be reasonably well predicted by applying the Morison...

Well Completion

The wells are designed to permit drilling, landing the tree, and completion using a conventional floating drilling rig. Tub-ingless completions are a part of the prototype SPS, as this design fits the requirements of the system. The wells will have the capability of vertical reentry workover if necessary. Control of valves and other parts of the SPS is through a closed hydraulic system as a basic power source. The pressure in the system is subsea-generated with all equipment mounted on a...

Underwater Welding and Habitats

Hot taps, pipeline repairs and structural repairs can be performed with a high degree of effectiveness. A habitat which is large enough to accommodate two diver-welders and the structural member to be repaired is lowered to the work site, sealed around the pipeline, and then dewatered with compressed air or some other inert atmosphere. The two most common welding techniques are known as TIG and MIG and require both training and skill to achieve code grade results. In addition, special equipment...

Background And History

Voith Thrusters

Dynamic positioning is a technique of automatically maintaining the position of a floating, unanchored vessel within a specified tolerance by using generated thrust vectors to counter the forces of wind, wave, and current forces tending to move the vessel away from the desired location. Design evolution and improvements in reliability allow station keeping by dynamic positioning for extended periods. Increases in available power and advances in sophistication of control equipment allow station...

Production Risers

On fixed production platforms the tubes running from the platform deck to each subsea wellhead are called connectors. After the oil runs up the connectors and thcough the processing equipment, it is then pumped from the deck down to the marine pipeline through the production riser. The three basic types of production risers are the J tube, the reverse J, and the bending shoe methods. The production riser actually contains a bundle of pipes. These individual pipes include the production,...

Lockheed Petroleum Services System

Well Control System Offshore

The subsea oil and gas production system developed by Lockheed Petroleum Services Ltd. LPS consists of three basic parts the wellhead cellar, the manifold center, and the service capsule. The system is completely diverless and all components are maintained at one atmosphere of pressure. It is fully automated for remote operation, is capable of through-flow-line TFL tool operation, and can be designed for any water depth. The first system was installed in the Gulf of Mexico in Main Pass Block...

Strength on Location

Offshore Drilling Parts

A typical stress range curve for one location at a joint on a jack-up leg is shown in Figure 6-8. Two requirements must be Fig. 6-8 Typical effects of static and fatigue loading on structure of mobile offshore drilling units. Fig. 6-8 Typical effects of static and fatigue loading on structure of mobile offshore drilling units. satisfied for North Sea operation static and fatigue criteria. Static criteria are well understood and have been used in the design of units for many parts of the world....

Space Out and Landing Procedure with Posi Test Packer

During the test, the length of hoth the major and minor pipe strings are subject to change. These lengths can either increase or decrease, depending on the changes in temperature and pressure. A minimum of two 2 slip joints are run between the two strings to allow for this expansion or contraction. One slip joint, provided with a safety valve, is installed on the lower end of the major pipe string. The other slip joint is installed on the upper end of the minor string. One 1 drill collar is run...

Unitized Blowout Preventer Stacks

Blowout Preventer

Depending on the casing program and expected drilling conditions, marine drilling operations can be carried out by using two separate riser sizes and corresponding blowout preventer stacks, or by using one single riser size and blowout preventer stack. When using two risers and two blowout preventer stacks, the system consists normally of a 24 inch riser and 20 inch blowout preventer stack. This blowout preventer stack is installed on the 20 inch surface casing. After a 17V2 inch hole has been...

PCT Testing String

For a better understanding of the new testing system. Figure 5-3 illustrates the relative location of each component in the string. Starting at the lower end, the string is composed of 2. Perforated or slotted tail pipe. 9. At least 90 feet of drill collars for sand which may settle from produced fluid. 10. Cushion displacement valve for spotting cushion. 11. Rotary type reverse circulation valve, 12. Pressure internal actuated reverse circulation valve. 13. Minor string collar weight required...

The Seal Systems

Buoyancy Support Riser

Subsea Equipment Associates, Limited SEAL is an international consortium owned by British Petroleum, Compagnie Fran aise des Petroles, Groupe Deep, Westinghouse Electric, and Mobil Oil Company. The consortium has developed two subsea production systems the SEAL Single-Well Completion and the Multiple-Well Manifold Production Station. The single-well system is designed for individual wells drilled vertically with production rates ranging to 10,000 barrels day. It is suitable for step-out wells...

Basic Test System

The principal objective of the formation test is the same, whether it is conducted from a floating vessel or a stationary rig. The test, however, is performed with different techniques and tool systems for the two types of rigs. When conducting testing operations on a stationary rig such as a jack-up, platform, or land type rig Figure 5-1 there is no relative motion between the rig and the well in a vertical direction. On this type of rig, conventional testing systems which are STATIONARY RIG...

Annular Blowout Preventers

Purpose Of Annular Blowout Preventers The annular blowout preventer BOP is the most widely used blowout preventer in the oilwell drilling industry. The purpose of BOP's in general is to close the well bore in the event that the well starts a kick. Ram preventers historically are limited to either blind rams which are closed to control the well provided no tools are in the well bore and to a specific pipe size, if pipe is in the hole. This normally precludes closing on tool joints, kellys, etc....

Note Annual Preventers

Annular Preventer

ARE 5000 PSI WORKING PRESSURE RATING FOR IS 3 4 Zl- 1 4 SUES Fig. 3-11 Subsea blowout preventer stack. 16 - 3 4 - 5000 18-3 4 amp 21-1 4 10000 16 - 3 4 - 5000 18-3 4 amp 21-1 4 10000 Fig. 3-11A Subsea blowout preventer stack. Fig. 3-11A Subsea blowout preventer stack. only one annular preventer. The redundancy of this system is obviously inferior to the arrangement in Figure 3-11. Figure 3-12 has an identical annular preventer arrangement to Figure 3-11. Here, however, the annular preventers...

Basic Components Of An Exploratory Riser System

Drilling Risers Choke Line

Figure 2-10 illustrates the arrangement of the riser system. It is important to note that the riser is not a simple piece of equipment but rather a complex system of component parts. A list of the sources foT components of basic riser equipment and the manufacturers of each component has been prepared Table 2-1 . Many manufacturers produce individual parts of the sub-sea riser system but only a very few supply the entire equipment package. Table 2-1 was compiled from the 1974 Composite Cataiog...

Causes Of Blowouts

Good planning, execution, and analysis will reduce frequency and severity of kicks, while a true commitment to understanding kicks will eliminate loss of wells resulting from blowouts and stuck pipe. Nevertheless, kicks can occur in any drilling operation conducted with a view towards attaining maximum effectiveness, These relatively infrequent kicks need not be unduly dangerous nor time-consuming when proper and prompt action is taken. Pressure unbalance leading to a kick may result from one...

Strength during

Figure 6-7 illustrates the effect of roll on the stresses which occur in the legs of a jack-up during ocean tow. Similarly, the flexure of the structure of a semisubmersible cannot exceed the allowable stress values. Several accidents have occurred with jack-up units during tow in rough seas, in which the legs have been damaged or even lost. The units must therefore be designed to withstand these stresses. Based partly on theory and partly on practical experience, the criterion of a 20 off...

Wireline Tensioner Ton Cycle Calculation

Western Gear Riser Tensioner

Sheaves to form a loop around the cylinder. Expansion force of the compression loaded cylinder or retraction force of the tension loaded cylinder attempts to expand the wireline loop. Thus, the force develops a pull or tension in the wire rope. One end of the wireline is connected to the tensioner or rig and the other end is reeved across an idler diverter sheave and to the top of the marine riser Figure 2-7 . Force in the cylinder is thus translated to wireline tension and then to tension in...

Reverse Circulation

After the test and prior to pulling the tools from the hole, all recovered formation fluids must be removed from the string and replaced with mud for safety and prevention of pollution. This can be done either during or after the final shut-in period. It is preferable to reverse circulate during the final shut-in period since valuable rig time is saved and sand produced into the pipe string will be kept in motion and not allowed to settle out during this period. The reverse circulating valve...

Governmental Regulatory Agencies

Most nations have an arm of the government such as the U.S. Coast Guard, the U.K. Department of Energy, and the Norwegian Maritime Directorate which is responsible for the safety of ships and offshore drilling units operating in their waters. While the classification societies are concerned mainly with the structural integrity and seaworthiness of the vessel, the governmental bodies are concerned primarily with the safety of the people on board and, increasingly, with environmental concerns....

Application to Platform Risers

Lockheed One Atmosphere Chamber

The LPS dry flow-line pull-in technique has been adapted to large-diameter pipelines used to move oil from a production platform. In this application, the platform riser pipe is equipped with a connector chamber, or pressure hull, having a top flange which will mate with the LPS service capsule Figure 4-19A . The riser pipe penetrates the wall of the pressure hull and is welded to a larger-diameter pipe section. This in turn is flanged to the bullnose penetrator. At the time of installation, a...

Considerations for Marine Risers

All Types Drilling Operation Sub Sea

Maini A riser can be simply described as a conduit from the platform to the ocean floor which transmits the drilling mud and serves as a guide for the drill string. There are two broad classes of risers, those used for exploratory drilling operations and those used for production operations. In exploratory drilling, the riser tube running from the vessel down to the wellhead is normally called a riser while the fust casing joint running from the wellhead slightly...

Techniques To Control Catastrophic Blowouts

Gas Well Blowout Offshore Libya

Control over a catastrophic blowout can be gained by any technique that blocks the escaping reservoir fluid either in the wellbore or in the formation. The method most frequently used is wellbore blockage, i.e., the recapping of a wild well. Relief well techniques, although more expensive to implement, have popular support because water pollution can be minimized by allowing the flowing wells to burn. Relief wells are sometimes drilled to establish direct connection with the wild-well bore...

Mark A Childers

Childers is Supervising Engineer with Ocean Drilling and Exploration Company Odeco in New Orleans, Louisiana. He has worked in many phases of production and drilling and has specialized in the development of subsea drilling equipment and the design and analysis of floating drilling units. Mr. Childers is a member of the American Petroleum Institute's Task Group on Mooring Gear for Floating Structures, He holds several patents, is a registered Professional Engineer in Texas and...

Thrust Signals Turning Error Only

TL RN1NG ERROR PLUS TURNING ERROR PLUS LONGITUDINAL ERROR LONGITUDINAL ERROR PLUS LATERAL ERROR Fig. 1-112 Vector diagrams for position keeping, 2 Thruster-Four degrees of freedom. thruster freedom represent many possible arrangements. Some of the thruster logic arrangements were straightforward and simple such as the statement that those transverse thrusters operating out of 11 total are to equally share in the sway thrust assignment and when both main screws are operating they shall equally...

Submersible S Under Construction Today

Glomar Challenger

10 12 14 10 18 20 2 2 24 26 28 PERIOD OF SEAS SECONDS time if mobility is required. Jn 1974 a large semisubmersible crossed the Atlantic in a record-breaking 21 days. The published data quote an average speed of 9.72 knots for the unit. This, of course, meant a considerable reduction in moving cost and a fair increase in productive time. On the other band, considering that once a unit has reached location it is generally in that area for a long time, propulsion units are not only unnecessary...

Analytical Review Of Exploratory Riser Systems

Deepwater Riser Diameter Water Depth

Analyses for exploratory riser design must include a large number of variables. The combined stress in the riser is due to both axial and hoop or circumferential stress. Hoop stress is caused by internal pressure of the mud column and pressure with kicks. External forces on the riser result from hydrostatic pressure which is calculated for the given water depth. The total axis stress is due to the tensioner load, riser buoyancy, riser weight, mud weight, current forces, and wave forces. With...

Perforated Tail Pipe Pressure Recorder

Tail Pipe Petroleum

Fig. 5-1 Testing system for stationary rig. operated by the up and down motion of the pipe string are used with a high degree of success. On the other hand, when a well is being tested from a floating vessel there is a perpetual cyclic motion between the vessel and the well in a vertical direction due to wave and tide action. This motion can vary in degree depending on weather conditions. For this reason, it is evident that the conventional system which utilizes up and down pipe string motion...

Classification Societies

The offshore drilling industry has adopted the practices ofthe shipping industry in accepting the established authority ofthe classification societies as certifying organizations. The worldwide classification societies are American Bureau of Shipping U.S.A. , Bureau Veritas France , Det Norske Veritas Norway , Germanischer Lloyd Germany , Japanese Marine Corporation Nippon Kaiji Kyokai Japan , Lloyd's Register of Shipping U.K. , and Registro Italiano Italy . The classification societies...

Working With The Classification And Certifying Authorities

It has been our experience in dealing with the classification societies that they are practical, experienced, and reasonable. They work closely with the rig owners and designers and are willing to consider the merit of any proposed exceptions or changes. However, they do require solid engineering back-up to justify any variances in policy they are asked to make. It is recommended that several steps be taken as early as possible in the planning of an offshore mobile drilling unit 1. Get to know...

Pretensioning Moorings Offshore

Drilling Line Wire Rope

000 10,000 20,000 40,000 60,000 Fig, 1-76 Anchor holding power vs anchor dry weight forLWT and Stato type Offdrill II anchors, reasonably good indication of large anchor holding power. Where dynamic anchors do not perform acceptably, some contractors and operators have used piled type anchors with limited success. However, they are extremely expensive and time consuming to install. Explosive imbedding type anchors have never been used in floating drilling operations due to their limited...

Application To Fixed Offshore Structures

Inspecting Offshore Drilling Platforms

The wave loads on fixed offshore structures are normally evaluated by means of one of two basic methods a Design wave method Fig. 1-70 Jonswap and modified Pierson-Moskowitz wave spectra. Fig. 1-70 Jonswap and modified Pierson-Moskowitz wave spectra. The method to be used should be considered in each specific case with due regard to the design and purpose of calculation. Until now, most analysis regarding wave loads on fixed offshore structures has been based on a regular, sinusoidal design...

The Manifold

Production Manifold

This unit Figure 4-20 is the heart of the entire system. It is Production line Gas-injection fine Waterflaod and production line Pump-down toot Une Production line Gas-injection fine Waterflaod and production line Pump-down toot Une Fig. 4-20 Production manifold for Exxon SPS. amp made up of all the necessary piping to carry out the assignments of the SPS. It is rectangular shaped with well-rounded corners to allow use of pump-down tools. In the prototype, its shape is almost square because the...

Tow Line Mooring Tension

Swivel Fairlead

Fig. 1-88 Required pretension vs water depth for ' a rated break strength of 3 in. chain to occur at 6 displacement see note . The next step is to select a water depth s to analyze. Figure 1-89 shows restoring force both with and without the two 2 leeward lines slackened, high line tension most loaded mooring line , and the high line tension anchor load vs. beam direction horizontal displacement in 600 foot water depths. Once again, Figure 1-89 is only valid for the stated conditions. Note that...

Dual Automatic Station Keeping System For Sedco

Retractable Azimuth Thruster

Fig. 1-119 Dual digital dynamic positioning simplified schematic. Fig. 1-119 Dual digital dynamic positioning simplified schematic. dard, high quality, interchangeable, industrial three mode controllers. Standardizing the controls allows plugging one common spare into either the surge, sway, or yaw control channel after setting the proportional band, rate, and reset to the channel's known settings. The advent of the mini-computer has really launched the digital computer into the control field....

Test Procedure

Monobuoy Pipe Inspection

To complete the test phase now underway in the Gulf of Mexico, Exxon drilled three directional wells into a proven reservoir. The prototype unit was designed for only three wells, but the system can be expanded to as many as 40 wells according to Exxon engineers. The subsea test program culminates more than 300 man-years of research and development and represents an expenditure of more than 30 million. The overall program, visualized in Figure 4-24, involves tests of all the subsystems as well...

Direction Of Propagation

Jonswap Spectrum

Fig. 1-62 Variation of particle velocity with depth below sea surface. Fig. 1-62 Variation of particle velocity with depth below sea surface. Slender elements like those just considered do not influence the velocity and acceleration field around the structure. A large body e.g., oil storage tank will, however, reflect the waves producing disturbances to the velocity and acceleration field. An increase in velocities and accelerations around the body may result. Consider for instance the...

Dynamic Positioning Controller

Purity of Position Determining Signals Dynamic positioning is a basic control problem in three degrees of freedom. A free body has six degrees of freedom in motion surge, sway, heave, pitch, roll, and yaw. The dynamic positioning system will be concerned only with surge bow-stern translational motion , sway port-starboard translational motion , and yaw rotational motion about the vertical axis . No attempt will be made to control pitch, roll, or beave by the dynamic positioning system. A first...

Requirements For C Las Si F Cat On And Certification

The first publication of rules pertaining to offshore mobile drilling units was the American Bureau of Shipping's Rules for Building and Classing Offshore Mobile Drilling Units in 1968. Since that time, the standards prescribed have been subjected to the test of actual application to a wide range of designs and a revised edition was published in 1973. Lloyd's Register published its Rules foT the Construction and Classification of Mobile Offshore Units in 1972. In 1973, Det Norske Veritas...

O I

Chain Mooring Torque Buoyancy Tank

Fig. 1-82 Required scope outboard of lower fairlead after pretensioning 3 in, chain-89.3 lb. ft. vs water depth as a function of maximum anticipated line tention. core, etc. Wire rope diameters up to 3Va inch have been used for mooring with the more common sizes being V-k to 3 inches. The wire rope should have an independent wire rope core IWRC center for crushing resistance and a zinc coating for corrosion protection since some of the wire rope will always be in the splash zone. Regular lay,...

Blowout Preventer Operating Procedures

Subsea Drilling Stack

The following covers the use of the blowout preventer BOP stacks and equipment used when drilling from a floating vessel. Figure 3-14 shows typical BOP stack with the major components normally used in a typical BOP stack. Though the size and pressure ratings may vary, all major BOP stacks in use for subsea drilling today contain the major components shown. These major components are 1 hydraulic wellhead connectors 2 ram type BOP's 3 annular type BOP's 4 hydraulic or elec-trohydraulic control...

Design And Water Depth Limitations

Most floating exploratory vessels are now outfitted with a riser system for a maximum water depth of about 1,200 ft. Four or five new drillships in operation or under construction will have riser systems for the extreme water depth of 3,000 ft. A design analysis has been performed on one particular advanced riser system for 6,000 ft. water depth. From that study it appears that 6,000-8,000 ft. of water is the practical limit for the conventional riser system. A drawback with risers for over...

Elements Of Dynamic Positioning

Dynamic Position

The three elements basic to dynamic positioning are 1 Position measurement or the continuous measurement of position with respect to ocean bottom borehole. 2 Control response or determination of correct thruster response from position measurement. 3 Thrust response or realizing body forces by expenditure of energy as a result of control command. Taut Line System for Position Measurement The Taut Line System uses a small diameter line attached to a weight on bottom. The weight is of such a size...

Subsea Production Systems

Evolutionary processes in the oil industry are slow since there is a natural resistance to change. But these processes are always at work and certain trends forecast the need or desire for subsea completions for oil and gas wells. As the potential for onshore oil and gas discoveries diminishes, oil operators and governments are moving offshore. Many countries with shorelines have already granted exploratory permits, and a large number of these have drilling and production concessions same as...

Tensioning Systems

Wireline Riser Tensioner System

A marine riser operating on a floating drill rig will fail collapse in water depths greater than 200 to 300 feet if it is not partially or completely supported. The marine riser is attached to the sea bottom via the blowout preventer BOP stack. Thus, it cannot be firmly attached to a floating drill rig. The support must come from axial tension applied to the top of the riser and or buoyancy along the length of the riser. Tension controls the stress level in the riser pipe and affects the riser...

Spread Mooring Systems

Spread Moored Anchor Pattern

In floating drilling, the purpose of the mooring system is to maintain the drilling vessel within certain horizontal limits of the centerline of the well so that drilling operations can be successfully carried out. This horizontal excursion during actual drilling operations is usually held to a maximum of 5 to 6 of water depth however, most drilling operations are carried out within 2 to 3 . These limits are controlled by the subsea drilling equipment such as stresses in the marine riser, angle...

Crown Mounted Compensator

Active Heave Compensated Drawworks

Wireline Motion Compensation-Logging A motion arrestor for nullifying vessel heave in wireline operations, especially in well logging operations, is available. This compensation device hangs below the hook and uses a working wireline reeved from the top of the riser pipe around the motion arrester working sheave, and to the drill floor. The logging sheave and working sheave are connected to the same yoke, which is suspended from the motion arrester by a pneumatic spring special tensioner . As...

Dr M D Reifel

Blowouts are of two types, surface blowouts and subsurface blowouts. Surface blowouts are possibly accompanied by fire, explosion, pollution, third party damage, and property damage to the drilling rig and platform. They also expose the company involved to potential unsatisfactory public opinion. If the blowout is uncontrolled, a valuable reservoir may be needlessly depleted. On the other hand, a subsurface blowout which leaves no impression on the surface can be equally devastating to a...

Voith Schneider

Taut Wire Dynamic Positioning

Fig. 1-104 Vital statistics of operational dynamic positioned ships. partial listing of the advantages and disadvantages of the taut line system follow. b Visible evidence of operation c All sophisticated equipment on deck f Immune from underwater noise a Mechanical taut line or tensioning system can fail b Large heading change must be made by stepping two units c Susceptible to error due to current drag Sample Tension Vs. Wire Line Size For Taut Line Unit Sample Tension Vs. Wire Line Size For...

Blowout Preventer Control Systems

Bop Control Systems

Foreman C. Jim Stewart amp Stevenson, Inc. Next to the blowout preventers, the most important component for well control in floating drilling is the system that monitors and controls the behavior of the subsea BOP s from the drilling rig. From 1955 to 1963, the control system design used in subsea drilling was basically a land rig or closed-type system. A hydraulic power unit provided fluid to a shipboard mounted control valve manifold. Hydraulic power lines were...