The systems that ensure the retention of drilling ships at a given point in the ocean are described. Algorithms and programs for calculating the optimal ones, taking into account the statistical characteristics of disturbing influences in the conditions of the World Ocean, are presented.
The book is intended for engineers and scientists involved in the creation of means for the development of the oceans.
TABLE OF CONTENTS
Foreword
Chapter first. Problems of stabilizing the movement of ships of various types
§ one. Technical means mining of the oceans
§ 2. Basic types
§ 3. Forces generated by sea waves and dynamics of motion in the horizontal plane
§ 4. Forces generated by wind and current
Chapter two. Disturbance characteristics
§ 1. Statistical characteristics of random processes
§ 2. Correlation function
§ 3. Spectral power density
§ 4. Energy spectrum of sea waves and the problem of low frequencies
§ 5. Recommended analytical approximation of the energy spectrum of perturbations
Chapter three. Synthesis of Optimal Single-Connected Stabilization and Tracking Systems
§ 1. Algorithms for constructing optimal operators
§ 2. The problem of synthesis of optimal control systems and its solution
§ 3. Physical meaning of optimal control under random perturbing forces
§ 4. Comparison with traditional methods theories automatic control
§ 5. Behavior of controlled systems when parameters deviate from calculated values
§ 6. Ensuring stability under variations of parameters and additional technical requirements to the managed system
§ 7. Guaranteed regulators
§ eight. Optimal Control under restrictions on the modulus of the control action
§ 9. Management by compromise criteria
§ 10. On the compilation of equations of control systems; decomposition of systems; taking into account the constant component in the disturbing action
§ eleven. general characteristics synthesis techniques and critical applications
Chapter Four. Optimization of multiply connected control systems
§ 1. Mathematical models of multiply connected control systems
§ 2. Control of multidimensional systems. modal control
§ 3. The optimization problem for multidimensional linear systems
Chapter five. Calculation of optimal stabilization systems for drilling ships
§ 1. Splitting of a multidimensional control system into one-dimensional systems
§ 2. Movement of a drilling ship under various laws of stabilization
§ 3. Optimization according to various quality criteria
§ 4. Correction and implementation of regulators
Chapter six. Technical implementation of systems for stabilizing the position of drilling rigs
§ 1. Media of automatic stabilization systems
§ 2. Means of actively keeping drilling ships at a given point
§ 3. Structures of dynamic stabilization systems for drilling ships
§ 4. Coordinated control of the position of semi-submersible drilling rigs
Conclusion
Appendix
Literature index
The remoteness of drilling areas from coastal bases, the complexity and low speed of towing, as well as low autonomy reduce the efficiency of using semi-submersible drilling rigs . Therefore, for prospecting and exploration drilling in remote areas, drilling ships. (Fig. 11).
The main mode of operation of drilling ships is drilling a well (85-90% of the total time of operation of the vessel). Therefore, the shape of the hull and the ratio of the main dimensions are determined by the requirements of stability and ensuring parking with as little movement as possible. At the same time, the shape of the hull must correspond to the speed of the vessel's movement of 10-14 knots or more. A characteristic feature for drilling ships is a small ratio of width to draft, equal to 3-4.
| Rice. 11- Moored drilling vessel. |
Moreover, there is a tendency to reduce this ratio (for the ships "Pelikan", "Saipem II", etc.), which can be explained by the expansion of the areas of operation and the requirements to increase seaworthiness. The choice of the main dimensions of the vessel depends on the required carrying capacity, which is determined by the estimated depth of drilling of wells and the autonomy of the vessel.
In the practice of drilling exploratory wells at sea, single-hull and multi-hull self-propelled and non-self-propelled vessels are widely used. From the mid-1950s to the end of the 1970s, only vessels with anchor and specific gravity in the fleet of floating drilling rigs was 20-24%. The scope for drilling ships with an anchor stabilization system is limited to sea depths up to 300 m.
New prospects in the development of offshore fields opened up in 1970 thanks to the creation of a dynamic positioning system, the use of which made it possible to set a number of records in the depth of explored waters. Since that time there has been a relatively rapid growth in the global fleet of deep sea drilling vessels.
Examples of foreign ships with a dynamic stabilization system are the Pelican (up to a sea depth of 350 m), Sedko-445 (up to 1070 m), Discoverer Seven Seas (up to 2440 m), Pelerin (up to 1000 m the first and up to 3000 m of the second generation), "Glomar Challenger" (up to 6000 m, the depth of the sea is actually conquered 7044 m), "Sedko-471" (up to 8235 m).
Self-propelled drilling ships There are single-hull and double-hull (catamarans). In domestic production organizations, predominantly single-hull ones are used. This is due to lower capital costs for their manufacture, since they were created on the basis of ready-made projects for the hulls of fishing vessels.
Single-hull drilling vessels of the "Diorit", "Diabaz", "Charoit", "Kimberlit" types, operated in the production expeditions of VMNPO "Soyuzmorinzhgeologiya", are equipped with an anchor stabilization system, spindle-type drilling rigs and technological equipment for carrying out engineering and geological surveys at a water depth of 15 to 100 m.
The experience of drilling from these vessels revealed a number of their design shortcomings, the main of which are an unreliable stabilization system at the well, small dimensions of the drilling site and a limited number of seats due to the use of serial hulls of fishing vessels, the impossibility of transferring the necessary axial load to the bottomhole when drilling with spindle type without compensators for vertical movements of the drill string, the impossibility of carrying out a complex of borehole geotechnical surveys and the selection of monoliths by indentation due to the use of a drill string of a geological exploration assortment with a diameter of 0.050 - 0.064 m. The only type of borehole surveys that can be performed from these vessels is pressuremetry.
The technological complex of each vessel consists of a drilling rig, a system for borehole geotechnological surveys (static sounding and sampling) and a bottom penetration unit. The use of a drilling conductor (riser) on these vessels is not provided. The drive of the main drilling mechanisms is hydraulic, hoisting operations are mechanized.
There are currently no specialized vessels for drilling exploratory wells at depths of more than 300 m in Russia.
A more promising type of vessels for drilling exploratory wells are catamarans. Compared to single-hull vessels of the same displacement, they have a number of advantages: higher stability (the rolling amplitude of a catamaran is 2-3 times less than that of single-hull vessels), which allows you to work in best conditions in heavy seas (the working time factor of double-hulled ships is greater than that of single-hulled ones by at least 25%); more convenient for work in shape and significantly larger (by 50%) usable deck area (since the space between the hulls is used), which makes it possible to place the required amount of heavy drilling equipment on the deck; shallow draft and high maneuverability (each hull is equipped with a lead screw), which facilitates their use in shallow water shelf conditions. The cost of building a single-hull vessel with a comparable working deck area is 20 - 30% higher than the cost of a catamaran vessel.
 |
| Rice. 12- Drilling ship "Catamaran". |
The American company "Reading and Bates" built the drilling ship "Catamaran", consisting of two barges fastened with nine beam trusses (Fig. 12). The length of the vessel is 79.25 m, the width is 38.1 m. It is possible to drill wells up to 6000 m deep from it at any depth of the sea. The vessel is equipped with: a drilling rig 43.25 m high with a lifting force of 4500 kN; rotor; double-drum winch driven by two diesel engines; two mud pumps driven by two other diesels; cementing unit; mud tanks; eight anchor winches with electric drive from two diesel generators of alternating current with a capacity of 350 kW each; living quarters for 110 people.
Of the catamaran drilling ships with significantly smaller geometric and energy parameters, it should be noted the domestic catamarans "Geologist-1" and "Geologist of Primorye", the technical characteristics of which are given below.
"Geologist-1" "Geologist of Primorye"
Displacement, t...................... 330 791
Length, m ....................................... 24 35.1
Width, m ............................... 14 18.2
Draft without load, m...................... 1.5 3.26
Freeboard, m 1.7 4.47
Power of diesel generators,
main .............................. 2x106.7 2x225
auxiliary .................. 2x50 2x50
Travel speed, knots .................... 8 9
Seaworthiness, points .............. 6 8
Working conditions:
distance from the coast, km.......... Up to 3 Up to 360
minimum depth
rya, m .............................. 2 5
sea roughness, points .............. 3 4
The minimum sea depth at which drilling from a catamaran is possible is determined by its draft, the maximum - by the length of the anchor cables. Possible well drilling depths depend on the type of drilling rigs installed on the catamarans.
The catamaran "Geologist-1" (Fig. 13) was built specifically for engineering and geological surveys in the coastal waters of the Black Sea.
Mounted on the catamaran: UGB-50M rig with electric drive for drilling wells up to 30 m deep in rocks by impact, core and auger methods; underwater penetration and logging station PSPK-69 for studying the physical and mechanical properties of soft soils and establishing the lithological structure of the seabed; seismoacoustic station "Grunt" for continuous profiling in order to obtain information about the lithological structure of the seabed throughout the area between the reference wells. At the survey point, "Geologist-1" is fixed with four anchors, and at sea depths of up to 7 m - additionally with two 8-meter-long spike piles.
Non-self-propelled floating drilling rigs they create, using as a base, non-self-propelled vessels (barges, scows, scows), wooden rafts or metal pontoons specially made for drilling, catamarans and trimarans not intended for drilling.
Of non-self-propelled ships, barges are most often used. Of the variety of types of barges, not all are suitable for offshore drilling. The most convenient dry-cargo barge has hatches opening in the bottom, so that the drilling rig can be installed in the center of the barge. Before the production of work, the barge is loaded with ballast to give it greater stability.
Sometimes two barges of the same type are used for drilling, paired with transverse bars. A catamaran is formed with a gap between the barges, in which the wellhead is located. Pairing barges allows the use of heavy drilling rigs and drilling in adverse hydrodynamic conditions of the sea.
Drilling rafts are the most affordable to manufacture. Heavy rafts are deeply submerged in water. This increases their stability, but increases the draft and does not exclude the overwhelm of the equipment even by a small wave. Over time, the rafts lose their buoyancy, and their service life is relatively short.
According to displacement, drilling metal pontoons are divided into light ones with an area of 30-40 m 2 and heavy ones with an area of 60-70 m 2. The stability of pontoons is low, and they are used mainly in closed water areas with sea waves up to 2 points.
In Russia, when drilling on the shelf of the Far Eastern seas, catamarans of the "Amur" type and trimarans of the "Primorets" type, which are vessels of a small size fleet with a sailing restriction on the wave state of the sea up to 5 points, are widely used. The first non-self-propelled. The latter can move independently at a speed of up to 4 knots in calm weather for short distances within the explored bay. However, they are also classified as non-self-propelled, since the working conditions in the overwhelming majority of cases force the use of auxiliary vessels for towing them. These catamarans and trimarans were developed by the SLE JSC "Dalmorgeologiya" for drilling by percussion and rotary methods of exploration wells of specific parameters and have the following technical characteristics:
Catamaran Trimaran
"Amur" "Primorets"
Length, m ....................................... 13.6 18.60
Width, m .............................. 9.0 11.80
Board height, m ........................ 1.5 1.85
Draft, m................................... 0.8 0.95
Displacement, t...................... 40 65
Number and weight (kg) of anchors.......... 4x150 4x250
The lifting force of the drill
howl of the tower, kN .............................. 200 300
Well parameters, m:
water depth ................... 25 50
depth by rocks .............. 25 50
Maximum diameter according to
casing string ............... 0.146/0.166 0.219/0.243
Rice. 14- Floating drilling rigs of JSC "Dalmorgeologiya":
a- PBU "Amur": 1 - anchor winch 2 - cabin, 3 - drawworks, 4 - drilling rig; b- PBU "Primorets": 1 - superstructure, 2 - drilling rig 3 - drawworks, 4 - traveling winch, 5 - vibrator, 6 - rotator
Trimaran "Primorets" - MODU with three hulls of serial vessels connected by a flat bridge made of rolled steel (Fig. 14, b). The propulsion engine and propeller-rudder device are located in the middle hull, shifted aft relative to the side ones. The diesel generator and flushing pump are located in two parallel side hulls of the trimaran. On the deck in the aft part of the installation there is a superstructure for household and office space, in the bow - drilling equipment is placed, containing an L-shaped drilling derrick, a winch for percussive drilling, a traveling equipment and a winch for lifting pipes, a rotator and a vibrator.
The deck of the Amur and Primorets FDR has U-shaped cutouts for the rig to move away from the well without removing the casing during a storm, poor visibility or repair, and then approach the well to continue drilling. The unsinkability and stability of these installations are preserved when any one compartment is flooded.
Catamaran "Amur" - MODU with two parallel hulls of serial crab boats, connected in the upper part by a flat bridge made of rolled steel, forming a common deck (Fig. 14, a). The power and auxiliary equipment of the installation is located in the hulls of the catamaran, which increased the working area. An A-shaped drilling rig, a winch for percussive drilling, a vibrator, casing pipes, a working tool, a deckhouse, and four anchor winches are installed on the deck.
Main: 2. [74-77], 3.
Extras: 7.
Control questions:
1. For what and at what depths are BS intended?
2. The design of the drilling ship.
3. A distinctive feature in the design of the MODU from BS.
4. With the help of what are the BSs kept?
5. What can be attributed to the advantages of BS?
DRILLING VESSEL (a. drilling vessel; n. Bohrschiff; f. navire de forage; and. barco perforador) - a floating structure for offshore drilling of wells, equipped with a central slot in the hull, over which it is installed, and a system for holding the vessel above the wellhead.
For the first time, drilling using a drilling ship began in the Atlantic Ocean in 1968 (from the American ship Glomar Challenger). Modern drilling ships (Fig.), as a rule, are self-propelled, with an unlimited navigation area. The displacement of the drilling ship is 6-30 thousand tons, the deadweight is 3-8 thousand tons, the capacity of the power plant that provides drilling operations, positioning and movement of the vessel is up to 16 MW, the speed is up to 15 knots, autonomy in terms of reserves is 3 months. On a drilling ship, stabilizers are used, which allow drilling wells at a sea state of 5-6 points; at higher seas, drilling stops and the vessel is in a storm sludge with an offset from the well (distance up to 6-8% from the sea depth) or the drill string is disconnected from the wellhead. To keep the drilling vessel at a given drilling point within the limits allowed by the rigidity of the drill string, 2 positioning systems are used: static (using the anchoring of the vessel) and dynamic stabilization (using propellers and thrusters).
Anchor system is used for drilling ship at sea depth up to 300 m; includes cables and chains, special anchors weighing 9-13.5 tons (8-12 pieces), anchor winches with a force of 2MN, equipped with instrumentation. Anchor placement and their cleaning are carried out from auxiliary vessels. To increase maneuverability and reduce work time when leaving the drilling point, the so-called. anchor systems of circular orientation of the vessel (a turret specially built in the center of the vessel's hull with a platform on which the entire anchor device, including winches, is mounted). Holding a drilling ship in position using a dynamic stabilization system is used for ships of any class at a sea depth of more than 200 m and is carried out automatically (or manually) by means of measuring, information-command and propulsion-steering systems.
The measuring complex includes acoustic system devices that are used to stabilize the vessel in the drilling mode, when the vessel is brought to the well, to determine the position of the riser relative to the wellhead. The operation of the acoustic system is based on the registration of pulses sent from bottom beacons located near the wellhead, and their acceptance by hydrophones under the bottom of the vessel. An inclinometer is used as a backup system. The information and command complex includes 2 computers that simultaneously receive information about the position of the vessel and the state environment; while one of them operates in command mode, controlling the engines, the second (reserve) - automatically (if the first one fails). The propulsion and steering complex includes the main propellers of the vessel, thrusters and their control system. The forces of the longitudinal stop on the vessel are created by controllable pitch propellers, the transverse thrust is created by special controllable pitch propellers installed in the transverse tunnels in the vessel's hull. The change in the size and directions of the stops is carried out by adjusting the pitch of the screws on command computer or manually from the control panel of the propulsion system.
The drilling vessel is also equipped with a control panel, which is designed to control the position of the vessel and the riser in the automatic stabilization mode, and remote manual control when the vessel is positioned. A type of drilling ship - the so-called. umbilical vessels designed mainly for engineering and geological drilling at a depth of 200 meters at a sea depth of up to 600 meters. They are equipped with a dynamic stabilization system, a flexible umbilical, due to which the requirements for the displacement of the vessel relative to the wellhead are less stringent than when using drill pipes.
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