Chapter 1: Rig Types

Transcription

1 Chapter 1: Rig Types Contents Objectives Fundamentals Types of Rigs Land rigs Offshore Rigs Floating Rigs Drillship Semisubmersibles Stationary Rigs Fixed Platforms Platform Tenders Jack-ups...11 Submerssible...12 Objectives The main objective of this chapter is to introduce the types of rigs both onshore and offshore to the trainees. It will also let them know the components of the rig and the layout as well as basic areas of the offshore rigs. 1.1 Fundamentals A drilling rig is a device used to drill, case and cement water, oil and gas wells. The correct procedure for selecting and sizing a drilling rig is as follows: 1. Design the well 2. Establish the various loads to be expected during drilling and testing and use the highest. This point establishes the DEPTH RATING OF THE RIG. 3. Compare the rating of existing rigs with the design loads 4. Select the appropriate rig and its components. 1.2 Types of Rigs 1

2 Drilling rigs are designed to meet specific operational requirements; therefore, different rigs have different capabilities. All offshore rigs, however, perform the basic function of drilling a hole or well in submerged lands by means of rotary drilling. This procedure provides a method of exploring for or producing oil and/or gas from earth formations. Drilling rigs are classified as Land rigs Offshore rigs 1.3 Land rigs Fig. 1 Land rig 1. Crown Block and Water Table 2. Catline Boom and Hoist Line 3. Drilling Line 4. Monkeyboard 5. Traveling Block 6. Top Drive 2

3 7. Mast 8. Drill Pipe 9. Doghouse 10. Blowout Preventer 11. Water Tank 12. Electric Cable Tray 13. Engine Generator Sets 14. Engine Generator Sets 15. Fuel Tank 16. Electrical Control House 17. Mud Pumps 18. Bulk Mud Component Tanks 19. Mud Tanks (Pits) 20. Reserve Pit 21. Mud-Gas Separator 22. Shale Shakers 23. Choke Manifold 24. Pipe Ramp 25. Pipe Racks 26. Accumulator 1.4 Offshore Rigs The first successful attempts at offshore drilling occurred between 1910 and In the 1920's, the Southern California coast experienced significant offshore drilling activity. At that time, rigs were often mounted on piers that extended out into the water. The late 1930's saw the beginning of oil activity in the Gulf of Mexico; at the present time, the Gulf is the most active offshore drilling area in the United States. The majority of offshore drilling activity has taken place since the mid 1950's. As oilmen reached farther out from the shoreline in search of oil, more advanced drilling techniques and machinery were developed; this advancement continues in today's oil industry. The first "submersible" drilling rig, the Brenton 40, was basically a drilling platform mounted on a pontoon stabilized barge. Built in 1949, this rig operated in the Gulf of Mexico in water depths of up to 22 feet and had a drilling capability of about 10,000 feet. Approximately twenty of this type of submersible rig were built between 1949 and Following the second World War, Navy surplus barges were utilized and developed as drillships. Jack-up drilling rigs were introduced in the early 1950's. Modern-type semi-submersible drilling rigs were not developed until quite recently, Fig. 2. Fig 2 The Cuss I (circa 1960) Converted from a Navy vessel, its design was based on research methods and exploratory techniques developed by the Cuss Group," a joint venture of four oil companies. Global Marine Drilling Company owns and operates a diversified fleet of offshore drilling rigs. The services of these rigs are leased, for a fee, to clients-usually oil and gas companies. The contracting company determines where the well will be drilled 3

4 and the depth of the hole. Having a diversified fleet enables us to offer prospective customers a rig which will conform to their operational needs. The purpose of this text is to provide you, the employee, with a general knowledge of: drilling rigs departmental responsibilities drilling operations the drilling department crew emergency procedures, and your duties as they relate to offshore drilling operations. In order for you to effectively perform your duties. an understanding of some marine terminology must be obtained. Fig. 3 will assist in acquainting you with some general nautical terminology. Fig. 3 Nautical terminology for direction and movement. Offshore drilling rigs can be classified into two basic groups: floating and stationary. Fig. 4 provides illustration of the major types of offshore rigs. 1. Floating rigs 1. Semisubmersible 2. Drillships 2. Bottom-supported rigs: There are three types: 1. Jack-ups 4

5 2. Platform 3. submesrsible 4. Barge Fig. 4 Basic types of drilling rigs 1.5 Floating Rigs Drillship Drillships are normally used to drill single exploratory wells. The two basic types of drillships are the barge type and the self-propelled type. Barge type, or non-selfpropelled drillships must be towed into position above drilling sites. Self-propelled type drillships are capable of movement under their own power and do not require towing. Drillships have the advantage of deep water drilling capabilities. The operating depth is usually between 100 and 600 feet; however, several drilling operations have been conducted in water depths greater than 1,000 feet. Other advantages of drillship rigs include economical operation, large storage capacities, and rapid mobility between drilling locations, Fig. 5. Drillships employ two basic methods of station keeping to maintain their position above drilling sites, Drillships that employ a conventional anchoring system utilize a series of anchors that fan out from the bow and stern of the ship and are set into the sea floor, Fig. 6. Ships using this type of system are restricted to operating depths of 1,500 feet or less. Drillships that are dynamically positioned keep their position above the drill sites by using bow and stern thrusters that are computer controlled, These drillships are capable of operating in water depths of over 2,000 feet. Dynamically positioned drillships do not have to employ the conventional anchoring system, but do on occasion in order to achieve better performance. 5

6 Fig. 5 Drillship Fig. 6 Diagram of drillship showing basic areas Semisubmersibles Semis, as they are called, are also used to drill single exploratory wells. The majority of semis are towed to their drilling locations, although some of the more recent models are self-propelled. The basic deck configurations range from triangular to pentagonal and utilize anywhere from three to over ten legs for support. The legs are attached to hulls or pontoons that can be flooded. The primary advantage of semis 6

7 over drillships is their high degree of stability in rough weather. For instance, in swells of 15 feet, some large semis have experienced vertical movement of as little as 12 inches. Semis utilize a spread anchoring system of radially spaced anchors to hold their position, The spread of the anchors is dependent upon anticipated wind and sea conditions, This anchoring system restricts semis to water depths of 200 to 1,500 feet. Some semi-submersibles are capable of setting on the sea floor, in the same manner as submersibles, Figs. 7 and 8. Fig. 7 Semi-submerssible rig 1.6 Stationary Rigs Stationary drilling rigs, as defined by their name, are affixed to the ocean floor by means of some type of legs. Some stationary rigs are moveable; however, during drilling operations, they do not encounter the ocean's movement because their drilling platforms are' positioned above the water line. Stationary rigs are used both for exploration and production of oil and gas fields. 7

8 Fig. 8 Diagram for semi-submerssible 8

9 1.6.1 Fixed Platforms Fixed platforms are normally used in developmental drilling. The first platforms were constructed on top of jetties that extended out from the shore, with connecting roadways supporting the drilling operations. This type of structure is still used in many areas of the world. A large percentage of offshore oil is obtained from fixed platform drilling operations. Several wells can be drilled from the same platform through multiple conductors within the steel jacket that supports the platform. A template system is common procedure for drilling from multi-well platforms and the use of directional drilling methods is common. Presently, most fixed platform operations are conducted in water depths of 450 to 600 feet; however, a number of platforms in the Southern California coastal area are set in waters 800 feet deep, with plans for new structures to sit in water depths of 1,000 to 1,500 feet., Fig. 9 Fig. 9 Fixed platform Platform Tenders Platform tenders, as the name implies, serve to sup port a fixed platform drilling operation. Unlike a full scale platform operation, the support equipment such as the mud pumps, bulk material storage containers and crew quarters are located aboard the tender rather than mounted onboard the platform. Physical connection between the platform and the tender is maintained by means of a bow ramp. Tubular goods such as drill pipe and casing are stored aboard the tender and transferred as needed to the platform. Pedestal cranes are provided aboard the tender for this purpose as well as for personnel transfer. Particular attention and care by personnel working aboard platform tenders must be paid whenever moving from the tender to the platform because the bow ramp is constantly in motion due to the wave action. The bow ramp area is particularly hazardous during periods of rough weather or heavy sea conditions as the" movement of the ramp is greatly increased, Figs 10 and 11. 9

10 Fig. 10 Platform-tender Fig. 11 Diagram showing basic areas of a platform-tender 10

11 1.6.3 Jack-ups Normally, a jack-up drilling rig is used to drill single exploratory wells in waters from 50 to 350 feet deep. The water depth is dependent upon the specifications of each individual rig as well as the bottom conditions, Figs 12 ad 13. Fig. 12 Jack-up rig Fig. 13 Diagram showing basic areas of a jack-up rig 11

12 A jack-up rig provides a stable platform from which a well can be drilled, with the added advantage of mobility to new locations when desirable. Most jack-up rigs have the capability of skidding, or cantilevering the derrick structure away from the main vessel for workover capability. Submerssible Submesrssible rigs, also suitable for shallow water, are like jack-up rigs in that they come in contact with the ocean or lake floor, Fig. 14. These rigs consist of platforms with two hulls positioned on top of one another. The upper hull contains the living quarters for the crew, as well as the actual drilling platform. The lower hull works much like the outer hull in a submarine Fig 14 Submerssible 12