Petrov stabilization systems for drilling ships. Petrov, Yuri Petrovich - stabilization systems for drilling ships. Approximate word search
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 of the 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 efforts 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 ship's hull. The change in the size and directions of the stops is carried out by adjusting the pitch of the propellers at the command of the 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.
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
§ 1. Technical means of extraction of minerals of the World Ocean
§ 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 of automatic control theory
§ 5. Behavior of controlled systems when parameters deviate from calculated values
§ 6. Ensuring stability with variations in parameters and additional technical requirements for a controlled system
§ 7. Guaranteed regulators
§ 8. 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
§ 11. General characteristics of the synthesis technique and the most important 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
Application
Literature index
Technically complex, very expensive and associated with a significant risk, operations for the development of oil and gas fields in the shelf zones of the seas and oceans include a whole range of interrelated stages.
Exploration work. Conducted in order to determine the location of geological structures in which accumulation of oil and gas is possible, exploration work is carried out in three phases:
Regional studies in order to highlight promising geological information;
Studying the general features of the geological structure, assessing the prospects for oil and gas potential and preparing areas by geological and geophysical methods for exploratory drilling;
Preparation of deposits (deposits) for development with calculation of reserves by industrial categories.
In the first phase, methods of gravimetric and magnetic reconnaissance are used, including photographing the Earth's surface from satellites and measurements using infrared technology.
In the second phase, search and detailed geological and geophysical work. For these purposes, other exploration methods are used - seismic surveys, the study of samples taken from the bottom of the sea. The second phase also includes structural and parametric drilling.
The third phase of exploration is the final one and leads to the discovery of the deposit (deep exploration drilling). At the same time, the field is delineated, wells are tested and oil and gas reserves are calculated.
Elements of the hydrogeological regime
The development of offshore oil and gas fields is fundamentally different from exploration and development on land. The great complexity and specific features of carrying out these works at sea are determined by the environment, engineering and geological surveys, the high cost and uniqueness of technical means, medical and biological problems caused by the need to perform work under water, the technology and organization of the construction and operation of facilities at sea, maintenance of works etc.
A feature of the continental shelf of our country is that 75% of the water areas are located in the northern and arctic regions, which are covered with ice for a long time, and this creates additional difficulties in industrial development. The environment is characterized by hydrometeorological factors that determine the conditions for carrying out work at sea, the possibility of building and operating oilfield facilities and technical equipment.
The main ones are:
water level
sea ice cover
chemical composition of water, etc.
temperature conditions
unrest
Accounting for these factors makes it possible to assess their impact on the economic performance of exploration and offshore oil and gas production. The construction of offshore oilfield facilities requires engineering and geological surveys of the seabed. When designing the foundations of oilfield facilities, special attention is paid to the completeness and quality of engineering and geological surveys of soils on site and in laboratories. Reliability and completeness of data largely determine the safety of operation of the facility and the cost-effectiveness of the project.
With the increase in the depths of the sea, the cost of developing deposits increases sharply. At a depth of 30 m, the cost of development is 3 times higher than on land, at a depth of 60 m - 6 times and at a depth of 300 m - 12 times.
In recent years, large-scale research work and pilot operation have been carried out, both of individual units and of entire complexes of equipment for underwater well operation. The underwater exploitation of offshore fields in ice conditions deserves special attention. This is due to the elimination of possible effects of ice on technical equipment, navigational hazard, fire hazard are reduced, and the economic development of the field is ensured.
The problem so far is the laying and especially the inspection and repair of underwater pipelines during the inter-ice period. The operation of marine technical facilities, and mainly equipment for underwater development methods, requires the safe conduct of underwater technical work during the repair and inspection of the underwater part of floating facilities and hydraulic structures. Along with the solution of technical issues, it is necessary to solve a number of tasks for the medical and biological support of human life, including in extreme conditions, as well as the tasks of medical and technical aspects of the thermal protection of human life during work under water.
Exploration and development of offshore oil and gas fields are technically complex operations, very costly and associated with significant risk. The main problems in the development of these deposits are the problems of engineering and technology for the production of these works.
Exploration and development of offshore fields are usually carried out in two stages:
At the first stage, exploration work is carried out in the interglacial period, and in this case, it is possible to use equipment that works in temperate zones.
At the second stage, in the development of deposits, i.e. the extraction, preparation and transport of oil and gas, due to the continuous production cycle, in which the process must be carried out all year round, including in winter, when the sea is covered with ice, unique and reliable equipment is required, technical and technological parameters and design solutions of which are determined by the requirements of high reliability, durability, ensuring the safety of work in each specific area.
One of the main conditions for a successful solution of the problem of development is the availability of information about the environment sufficient in terms of volume and quality. The growth rate of observational data in the world's oceans is very high, which provides a doubling of the amount of accumulated information every 5-6 years. Due to the rapid development of space-based observational means, it is expected that in the near future the duration of the increase in information may be somewhat reduced.
Careful study of hydrometeorological conditions is most necessary in the development of oil and gas fields. This is due to the fact that hydraulic structures are built and operated in unprotected water areas in severe weather conditions. In extreme environmental conditions, the structures must withstand and not collapse from the effects of the elements and ensure reliability in operation for the entire period of operation of the field (25-30 years).
At different stages of designing the development of oil and gas fields, different volumes of hydrometeorological information are required.
At the stage of designing offshore oilfield facilities, more detailed and large volumes of data are required to determine the locations and layout of hydraulic structures on the field area and the degree of environmental impact on them. This includes the following inputs:
Maximum wave height and corresponding period;
Maximum values of wind speed and currents;
Extreme changes in water levels to account for tides and storm surges;
ice conditions;
Regime distributions of heights, periods and parameters of waves, waves by points, speed and direction of winds and currents;
Profiles of currents, spectrum of wind and waves, group properties of waves;
Variation of wind speed and wave parameters in typical and most severe storms.
The wind regime is the main meteorological factor affecting such hydrological elements as waves, currents, ice drift, etc. The strength of the wind and its influence on the hydrometeorological state of the water basin is usually determined by the Beaufort scale.
Sea currents - the forward movement of new land masses, etc. Sea currents, which have a great influence on atmospheric circulation and climate in various parts of the globe, are caused by wind friction on the sea surface, uneven distribution of salinity (and, consequently, density) of water, and changes in atmospheric pressure due to the inflow and outflow of sea water. Sea currents are distinguished according to the degree of stability: changeable, temporary, periodic (seasonal), stable; by location: deep surface, near-bottom; on physico-chemical and temperature properties.
A wave is the propagation of oscillations (disturbances) in any deformed medium. Of the many types of waves, wind and gravity waves play an important role. The most important parameters for calculations are their length, height and frequency.
Environmental studies are carried out according to special methods and recommendations developed by special organizations, societies and departments, taking into account the requirements of industries. Fundamental research is carried out by state organizations, associations, etc.
Test questions:
1. What is the complexity of offshore field development?
2. What characterizes the environment?
3. What is included in hydrometeorological factors?
4. What initial data is needed for the design of offshore oil and gas facilities?
5. Define the wind regime, sea currents and waves.
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 vessels "Pelikan", "Saipem II", etc.), which can be explained by the expansion of the areas of work 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 tie-in stabilization systems were used for drilling, their share 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 "Soyuzmorinzhgeologia", are equipped with an anchor stabilization system, spindle-type drilling rigs and technological equipment for engineering and geological surveys at water depth from 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 better conditions with strong sea waves (working time factor there are more double-hulled ships than 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.
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| 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 that open 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 vast majority of cases force the use of auxiliary vessels for towing them. These catamarans and trimarans were developed by 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 the 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 service premises, in the bow - drilling equipment is located, containing an L-shaped drilling derrick, a winch for percussive drilling, traveling equipment and a winch for lifting pipes, a rotator and a vibrator.
In the deck of the Amur and Primorets MODUs there are U-shaped cutouts for the unit 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 derrick, 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.
Test 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?