Cryogenic drilling rig solid control system is to ensure efficient separation of solid phases and stabilisation of mud performance under low temperature conditions through multi-module synergy, while special measures are taken to adapt to the low temperature environment to ensure normal operation of the system under low temperature conditions.
In the field of oil and gas exploration and development, with the growth of global energy demand, more and more drilling operations are expanding to low-temperature regions such as polar regions and high latitudes. The low-temperature environment brings many challenges to drilling operations. First of all, we have to know that in the low-temperature environment, the viscosity of the drilling fluid will increase significantly, and the fluidity will become poor, which not only affects the circulation of the drilling fluid in the well and reduces the rock-carrying capacity, but also may lead to higher pump pressure, increase the load on the equipment, and even cause equipment failures. At the same time, the low temperature may make the performance of some additives in the drilling fluid decline, affecting its stabilising effect on the formation and lubricating effect on the drilling tools.
Low temperature will make the physical properties of metal materials change, such as reduced toughness and increased brittleness, resulting in the structural parts of the equipment, pipelines and other more likely to rupture. In addition, low temperatures can affect the sealing performance of equipment, causing drilling fluid leakage. For some equipment relying on hydraulic drive, low temperature will make the hydraulic oil viscosity increase, poor fluidity, resulting in equipment slow action, or even can not work properly.
At low temperatures, solid-phase particles in the drilling fluid are more likely to gather, increasing the difficulty of solid-control equipment to separate the solid phase. Moreover, some key components in the solid control equipment, such as the screen mesh of vibrating screen, are less flexible in low temperature and easily damaged, which affects the solid control effect. As a key equipment to ensure the stable performance of drilling fluid and realise efficient drilling, the importance of low-temperature drilling rig solid-control system is self-evident. In this article, we will discuss the working principle, equipment composition, technical difficulties and other aspects of the cryogenic rig solid control system to bring you a comprehensive understanding of this drilling equipment that plays an important role in the extreme cold environment.
一.Working Principle of Cryogenic Rig Solid Control System
The core task of cryogenic drilling rig solid control system is to effectively control and separate solid-phase particles in the drilling fluid under low temperature environment, to maintain the good performance of the drilling fluid and to ensure the smooth operation of drilling. Its working principle is based on a variety of physical and chemical methods, mainly including sieving, centrifugal separation, gravity separation and so on.
Vibrating screen, as the first-level equipment of the solid control system, separates solid-phase substances such as rock chips with larger particles from the drilling fluid through high-frequency vibration and the use of screen mesh. The desander, on the other hand, makes use of the cyclone principle, under the action of centrifugal force, to make the heavier solid-phase particles in the drilling fluid, such as sand particles, spiral downward along the inner wall of the cyclone, and discharge from the bottom, while the purified drilling fluid flows out from the overflow port at the top. The working principle of the desludger is similar to that of the desander, except that it handles particles of smaller size. The centrifuge, on the other hand, further separates the very fine solid-phase particles in the drilling fluid by rotating at high speed to improve the degree of purification of the drilling fluid.
In order to ensure the proper functioning of these devices at low temperatures, solid control systems are usually equipped with auxiliary systems such as insulation and heating. For example, circulating tanks and pipelines are insulated to reduce heat loss; heating devices, such as steam heaters and electric heaters, are installed in the tanks or key parts of the equipment to maintain the temperature of the equipment and drilling fluid within a suitable range, so as to ensure the normal operation of the equipment in the solidification control system and the effect of solidification control.
二.System components of cryogenic drilling rig solid control system
1.Main processing equipment
Cryogenic vibrating screen
The screen box is made of low-temperature-resistant material, equipped with low-temperature lubrication system and anti-freezing motor.
The design of the screen takes into account the water permeability and frost resistance under low temperature to prevent the mud from freezing and clogging.
Low Temperature Desludger
The cyclone is made of wear-resistant and low-temperature-resistant alloy materials and equipped with low-temperature seals.
The slurry feed pump is equipped with electric heat tracing or hot water jacket to avoid the slurry from solidifying in the pipeline.
Low temperature centrifuge
The drum and screw conveyor are made of cryogenic alloy to prevent cold brittle cracking.
Integrated heating system (e.g. hot oil circulation) to maintain slurry fluidity and avoid viscosity surge at low temperature.
2.Auxiliary Systems
Heating and Insulation Systems
Electric heat tracing / vapour jackets: cover pipework, tanks and equipment surfaces to maintain slurry temperatures above 0°C.
Insulation: Tank and key components are insulated with polyurethane foam or rock wool to reduce heat loss.
Anti-condensation and circulation system
Agitator: installed in the slurry tank to prevent solid phase precipitation and slurry coagulation.
Circulation pump: equipped with a standby pumping unit to ensure continuous circulation at low temperatures and avoid pipe clogging.
3.Power and energy system
Cold-resistant power equipment
Motor and hydraulic system adopt low temperature lubricant to ensure normal start-up under – 40℃.
Backup power supply (such as diesel generator) is equipped with low-temperature starting device to prevent shutdown.
High-efficiency heat exchange system
Heat exchanger recovers waste heat from the drilling rig to reduce energy consumption.
Fuel oil heating device (e.g. thermal oil furnace) provides stable heat source for mud.
三.Technical Difficulties of Solid Control System for Cryogenic Drilling Rigs
1.Adaptability of equipment to low temperature
Material selection: For the problem of reduced toughness and increased brittleness of metal materials in low temperature environment, low temperature resistant metal materials, such as low temperature alloy steel, etc., are used in the manufacture of equipment. For some key components, such as vibrating screen mesh, pipes, etc., special polymer materials or composite materials are used, which can still maintain good flexibility and mechanical properties at low temperatures.
Lubrication and sealing: choose lubricants with good low-temperature performance to ensure that the equipment can be properly lubricated at low temperatures and reduce wear and tear of the moving parts. At the same time, optimise the sealing structure of the equipment, use low temperature resistant sealing materials, such as fluorine rubber, etc., to improve the sealing performance of the equipment and prevent the leakage of drilling fluid and hydraulic oil.
Heating and heat preservation design: Reasonable design of the heating and heat preservation system to ensure that the equipment can be quickly warmed up and maintain a stable working temperature in a low-temperature environment. By accurately calculating the heat loss of the equipment, selecting the heating device with appropriate power, and adopting highly efficient heat preservation materials and structures to minimise heat dissipation.
2.Guarantee of solid control effect
Optimisation of equipment parameters: Under the low temperature environment, the working parameters of solid control equipment are optimised and adjusted according to the changes in drilling fluid performance. For example, appropriately increase the vibration frequency and amplitude of the vibrating screen to enhance the screening effect; adjust the inlet pressure and rotational speed of the desander, desilter and centrifuge to improve the solid-phase separation efficiency.
Increase the pre-treatment link: In order to reduce the workload of the solid control equipment, improve the solid control effect, you can increase the pre-treatment link in the front end of the solid control system. For example, the use of pre-settling devices, so that some of the larger solid-phase particles in the drilling fluid before entering the solid-control equipment for preliminary settlement and separation, to reduce the processing pressure of subsequent equipment.
Energy Reserve and Guarantee: Considering the possible difficulties of energy supply in low-temperature areas, sufficient energy reserve equipment is equipped, such as standby generators and oil storage tanks. At the same time, the establishment of a perfect energy management system, real-time monitoring and analysis of energy consumption, rational arrangement of energy use, to ensure that the solid control system in the case of unstable energy supply can still operate normally.
四.Main features of the cryogenic drilling rig solid control system in terms of design and production.
1.Adopting thermal insulation materials to wrap the equipment tanks, pipes, etc. to reduce heat dissipation, and setting up heating devices such as steam heating coils and electric heating elements inside the tanks to prevent freezing of drilling fluids. The system is also equipped with a heat preservation shed, and the internal temperature is not lower than 10℃；
2.Key components are made of low-temperature materials, using cold-resistant seals and low-temperature lubricants, which can operate normally at low temperatures, and all components can ensure normal operation at low temperatures of -40℃；
3.Redundant design of key components reduces maintenance downtime at low temperatures.
五.Cryogenic drilling rig solid control systems are mainly used in some of the following scenarios:
1.Polar region drilling: such as Antarctica, the North Pole and other polar environments；
2.Cold region drilling in high mountains and plateaus: some high altitude mountain ranges and plateau areas；
3.Onshore oil and gas drilling in cold climatic conditions: in some high latitude or inland cold areas；
4.Cold marine drilling: in high latitude marine areas.
As a key equipment to deal with drilling operations under extreme cold environment, cryogenic rig solid control system is of great significance to ensure stable performance of drilling fluid, improve drilling efficiency, reduce operation cost and protect the environment. As the exploration and development of oil and gas resources in low-temperature areas continue to deepen, the low-temperature drilling rig solid control system is facing more challenges and opportunities. By constantly overcoming technical problems and innovating development concepts, the cryogenic drilling rig solid control system will make greater breakthroughs in intelligence, energy saving and environmental protection, and equipment integration in the future.
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