Technical methods used to drill wellbores in the exploration and development of oil and natural gas. It mainly includes well design, selection of drill bits and mud, drill tool assembly, drilling parameter coordination, well inclination control, mud treatment, core taking, accident prevention and handling, etc. The characteristics of oil drilling technology are: deep wellbore, high pressure, high temperature, many influencing factors, etc. In the past, drilling mainly relied on experience. In the 1950s, research began on the factors affecting drilling speed and cost and their interrelationships. New drilling technologies and new theories are constantly emerging. The borehole direction must be controlled within the allowable range. According to the geological and geographical conditions and engineering needs of oil and gas exploration and development, they are divided into two categories: vertical wells and directional wells. The latter can be divided into general directional wells, horizontal wells, cluster wells, etc.
The vertical wellbore is drilled in the vertical direction and reaches the target layer within the specified range of inclination angle and azimuth angle. There are also certain restrictions on the curvature of the wellbore and the horizontal displacement of the well bottom relative to the wellhead. requirements (Figure 1). If the horizontal displacement of the bottom of the production well is too large, it will disrupt the well layout plan for oil field development; if the horizontal displacement of the bottom of the exploration well is too large, the expected target layer may not be drilled. Excessive well angle change rate will increase the difficulty of drilling and oil production operations and easily lead to downhole accidents. The factors that affect the well inclination and azimuth include: geological conditions, drilling tool assembly, drilling technical measures, operating technology and equipment installation quality, etc. In order to prevent the well inclination angle and wellbore curvature from being too large, a reasonable lower drilling tool assembly must be selected. Commonly used are rigid full-hole drill tool assembly (Figure 2) and pendulum drill tool assembly (Figure 3). The former can be drilled with a larger weight on bit, which is beneficial to increasing the drilling rate. The wellbore curvature is smaller, but it cannot correct the deviation. The latter requires controlling a certain pressure on bit and affecting the drilling speed, but it can be used to correct the deviation.
Directional wells are wells drilled along the pre-designed borehole direction (well inclination angle and azimuth angle) to reach the target layer. Mainly used for: ① restricted by ground terrain, such as oil fields buried under towns, mountains, lakes or fertile fields; ② offshore cluster drilling; ③ due to special geological structures (such as faults, fracture layers, or too large inclination of the formation, etc.) If necessary, drilling directional wells is conducive to the exploration and development of oil and gas reservoirs; ④ Handling underground accidents, such as sidetracking, rescue wells drilled to prevent blowouts and fires, etc.
The cross-section design of directional wells generally consists of a vertical well section, an inclination-building section, a stable inclination section and an inclination-reducing section. A deflection drilling tool composed of downhole power drilling tools (turbine drilling tools or screw drilling tools) and bent joints is commonly used in deflection and twisting azimuth well sections (Figure 4). When the inclination of the wellbore finally reaches or approaches horizontal, it is called a horizontal well. During directional drilling, the inclination and orientation of the wellbore must be constantly monitored, and the wellbore trajectory map must be drawn at any time for timely adjustment. Commonly used inclinometers include single-point, multi-point magnetic photographic inclinometers and gyro inclinometers. In recent years, inclinometers while drilling have also been used to know the inclination and orientation of the wellbore at any time without tripping. According to the signal transmission method, there are two types: wired and wireless. The former uses cables to transmit signals, and the latter uses mud pulses, Electromagnetic, sound waves, etc.
Cluster wells are also called intensive wells and group wells (Figure 5). Several to dozens of directional wells are drilled in different directions at a location and on a limited well pad, so that each well is drilled along the The respective designed wellbore axes can be drilled to reach the target layer respectively. They are usually used on offshore platforms or in areas such as cities, fertile fields, swamps, etc. It can save a lot of investment, occupy a small area, and facilitate centralized management.
In jet drilling, the high-pressure mud transported by the mud pump forms a high-speed impact jet (usually above m/s) through the drill bit nozzle, which directly acts on the bottom of the well, making full use of hydraulic energy (generally 50% of the pump water power) % or more acts on the bottom of the well), causing the cuttings to rush away from the bottom of the well in time or directly crushing the formation, which can greatly increase the drilling speed. A reasonable way to work is to use higher pump pressure, lower displacement and smaller drill nozzle diameter.
Optimized parameter drilling is based on the analysis of drilled data, using electronic computers as a means, and using optimization methods to combine various controllable factors that affect the drilling speed (such as drill bit type, bit weight, rotation speed , mud properties, hydraulic factors, etc.), establish a mathematical model based on the principle of lowest cost, and compile a calculation program. Optimal cooperation is carried out to achieve high-quality, fast and low-cost drilling work.
Formation pore pressure prediction and equilibrium pressure drilling use seismic, logging and drilling data (mechanical penetration rate, shale density, mud specific gravity, temperature, etc.) for comprehensive analysis to predict formation pore pressure and Determine possible abnormal pressure formations and take timely measures to prevent sudden blowouts, well leaks, well collapses and other complex underground situations. Based on the known formation pore pressure and formation fracture pressure, determine reasonable mud gravity and casing procedures.
Drilling under conditions where the mud column pressure and formation pore pressure in the well are approximately balanced is called balanced pressure drilling. It can significantly increase the drilling rate and is also beneficial to the discovery of oil and gas reservoirs.
Well control technology: When drilling into abnormally high-pressure formations and mud gas invasion or well kick occurs, calculation methods and appropriate technical measures are used to adjust the mud specific gravity and flow characteristics, and use hydraulic high-pressure blowout prevention equipment Control and eliminate well overflow to prevent blowouts.
Coring technology: Drill rock samples (cores) of required layers from underground according to design requirements to obtain primary data for the exploration and development of oil and gas reservoirs. Commonly used coring tools are mainly composed of core drill bits, core barrels, core grabs, joints and other components. During coring drilling, the drill bit continuously cuts the rock at the bottom of the well in an annular shape, so that the drilled columnar core continuously enters the core barrel. In order to meet special needs, there are also closed coring, pressure maintaining coring and coring tools (rubber sleeve coring tools) for extremely loose and broken formations.
The national 863 project "Research on Key Technologies of Rotary Steering Drilling Systems" undertaken by the Shengli Oilfield Drilling Institute, after nearly three years of research, was successfully tested on site in the Shengli Oilfield at the end of September, marking that the project Research has made breakthrough progress.
Rotary steerable drilling technology is a new automated drilling technology developed at the end of the last century. It is an effective technology for reducing oil and gas development costs and improving oil and gas recovery. It is said to represent the highest level of current drilling technology. The international research and development of rotary steerable drilling technology began in the early 1990s. More than 20 companies have been involved in the research and development of this technology. So far, only three of the world's largest technical service companies have formed on-site application capabilities.
In order to adapt to the needs of the oil and gas development situation, improve the level of domestic drilling technology and participate in the competition in the global drilling market, Shengli Drilling Institute began to conduct preliminary research on rotary steerable drilling technology in 1998, and entered the rotary steerable drilling system in 2002 Key technology research and prototype development stage. The rotary steering project team of the Drilling Institute and Xi'an Petroleum University established a joint development project team to achieve complementary technical advantages. The Drilling Institute and Xi'an Petroleum University have jointly carried out hundreds of design changes, dozens of indoor simulation tests of key units, researched and developed 3 sets of rotary steerable drilling downhole tool system prototypes, and carried out 4 rounds of more than 20 ground tests. , from August 22 to 23, 2006, the entire rotary steerable drilling system including the rotary steerable drilling downhole tool system, MWD measurement while drilling system, information uploading system and surface monitoring system was conducted on the Ying 12-Xie 225 well. The purpose of the joint field test is to test its function of maintaining the original orientation in the inclined wellbore to achieve deflection, to test the "measurement, control and storage" during deflection and to test the comprehensive performance of the mechanical structure.
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Offshore oil and gas development Offshore oil and gas development is not very different from that on land. It is just that the cost of building an oil production platform is much greater, so it affects the scope of the oil and gas fields. The evaluation work should be more cautious. It is necessary to carry out risk analysis and accurately select the platform location and construction scale. Avoid losses caused by unclear understanding of underground oil reservoirs or incorrect inferences. Since the 1960s, offshore oil development has developed greatly. The oil production from offshore oil fields has reached about 20% of the world's total oil production. A complete set of special equipment and technologies for offshore mining and gathering has been formed. The construction of the platform can withstand various disasters such as wind, waves, ice flows and earthquakes. The water depth of oil and gas fields has exceeded 200 meters.
There are still many areas in the world that have not yet been explored or fully explored. Oil and gas exploration in deep strata and deep-water parts of the ocean has just begun. More oil and gas reservoirs will be discovered. Applications in developed oil and gas reservoirs The amount of crude oil that can be extracted by enhanced oil recovery technology is also quite large; these indicate that the science and technology of oil and gas extraction will have greater development.
Petroleum is a fluid mineral buried deep underground. At first, people called the oily liquid minerals produced in nature petroleum, the combustible gases called natural gas, and the solid combustible minerals called asphalt. With the in-depth study of these minerals, it is realized that they are all hydrocarbon compounds in composition and are related to each other in origin, so they are collectively called petroleum. The 11th World Petroleum Conference in September 1983 proposed that petroleum is a complex mixture consisting of gaseous, liquid and solid hydrocarbon compounds existing in nature as well as a small amount of impurities. Therefore, oil extraction also includes natural gas extraction.
The role of petroleum in the national economy Petroleum is an important energy source. Compared with coal, it has high energy density (the combustion heat of petroleum of the same weight is 50% higher than that of standard coal), convenient transportation and storage, and good stability after combustion. The air pollution level is smaller and so on. Fuel oil extracted from petroleum is the main fuel for various kilns in transportation vehicles, power station boilers, metallurgical industry and building materials industry. Liquefied gas and pipeline gas based on petroleum are high-quality fuels used by urban residents. Planes, tanks, ships, rockets and other spacecraft also consume large amounts of petroleum fuel. Therefore, many countries have classified oil as a strategic material.
Since the 1970s, oil has surpassed coal and ranked first in the composition of world energy consumption. It accounted for 45% in 1979, and this situation is not expected to change significantly by the beginning of the 21st century. Petroleum products are also widely used as lubricants for various machinery. Asphalt is an important material for roads and construction. Petrochemical products are widely used in agriculture, light industry, textile industry, medicine and health and other sectors, such as synthetic fibers, plastics, and synthetic rubber products, which have become necessities in people's lives.
In 1982, world oil production was 2.644 billion tons and natural gas was 1.5829 billion cubic meters. Since 1973, three oil price increases and the oil price decrease in 1982 have caused major fluctuations in the world economy (see World Petroleum Industry).
Oil and gas accumulation and driving methods After oil and gas are generated in the earth's crust, they exist in a dispersed state in the oil and gas generating layers. After migration, they enter the reservoir and accumulate in geological traps with good preservation conditions to form Oil and gas reservoirs. There can be several oil and gas reservoirs within a geological structure, combined into oil and gas fields.
Reservoir is a rock formation with storage space that stores oil and gas and allows oil and gas flow to pass through it. The space in the reservoir includes pores between rock fragments, fissures in rock cracks, and cavities formed by dissolution. Porosity is generally related to sedimentation, fissures are mostly related to structural deformation, and voids are often related to ancient karst. The size, distribution and connectivity of voids affect the flow of oil and gas and determine the characteristics of oil and gas production (see Petroleum Development Geology).
Oil and gas driving method In the process of oil extraction, oil and gas flow from the reservoir to the bottom of the well, and then rise from the bottom of the well to the wellhead. Mainly include: ① water drive oil reservoir, the hydrostatic head formed by the surface water supply in the surrounding water body; ② elastic water drive, the elastic expansion effect of the surrounding closed water body and reservoir rock; ③ dissolved gas drive, the pressure reduction causes dissolution The expansion effect when the gas in the oil escapes; ④ gas cap drive, the expansion effect of the gas cap gas as the pressure decreases when there is a gas cap; ⑤ gravity drive, gravity oil drainage. When the above natural energy is sufficient, oil and gas can spray out of the wellhead; when the energy is insufficient, artificial lifting measures need to be taken to drive the oil flow out of the ground (see self-injection oil production method, artificial lift oil production method).
Compared with general solid mineral deposits, the characteristics of oil mining have three significant characteristics: ① The objects of mining are constantly flowing during the entire mining process, and the oil reservoir conditions are constantly changing. All measures must be aimed at this. Therefore, the entire process of oil and gas field mining is a process of continuous understanding and continuous improvement; ② Miners generally do not have direct contact with the ore body. The extraction of oil and gas, the understanding of the conditions in the oil and gas reservoirs, and the various measures to influence the oil and gas reservoirs must be carried out through special well logging; ③ Certain characteristics of the oil and gas reservoirs must be determined during the production process, and even in the number of wells. It is only later that it is realized that, therefore, the exploration and production phases are often intertwined with each other over time (see Oil and Gas Field Development Planning and Design).
To develop an oil and gas reservoir well, it is necessary to have a comprehensive understanding of it, drill a certain number of edge wells, and use geophysical exploration data to determine the various boundaries of the oil and gas reservoir (oil-water boundary, oil and gas boundary, segmentation faults, pinch-out lines, etc.); a certain number of evaluation wells must be drilled to understand the properties of the oil and gas layers (generally cores must be taken), including thickness changes of the oil and gas layers, physical properties of the reservoir, reservoir fluids and their properties, and characteristics of the reservoir. Characteristics such as temperature and pressure distribution can be comprehensively studied to obtain a more comprehensive understanding of oil and gas reservoirs. In the study of oil and gas reservoirs, we cannot only study the oil and gas reservoir itself, but also study the adjacent aquifers and their connectivity (see Reservoir Physics).
During the production process, oil and gas reservoirs also need to be mined, observed and controlled through production wells, injection wells and observation wells.
The flow of oil and gas has three interconnected processes: ① oil and gas flow from the oil layer to the bottom of the well; ② rise from the bottom of the well to the wellhead; ③ flow from the wellhead into the oil gathering station, and after separation and dehydration, flow into the oil and gas terminal. Transfer to the mining area (see Reservoir Engineering).
Petroleum Extraction Technology
Well logging engineering applies geophysical methods in the wellbore to record the original conditions and changed information in the drilled rock formations and oil and gas reservoirs, especially oil, Information on the distribution and changes of gas and water in the reservoir is transmitted to the surface through cables, based on which comprehensive judgments are made to determine the technical measures that should be taken (see engineering logging, production logging, saturation logging).
Drilling engineering plays a very important role in the development of oil and gas fields. In the construction of an oil and gas field, drilling engineering often accounts for more than 50% of the total investment. The development of an oil and gas field often requires drilling hundreds or even thousands or more wells. There are different technical requirements for wells used for different purposes such as production, observation and control (such as production wells, injection wells, observation wells and inspection wells designed to check the effect of water washing oil, etc.). It should be ensured that the drilled well has the least pollution to the oil and gas formation, has high cementing quality, and can withstand the impact of various underground operations during decades of mining. Improving drilling technology and management and increasing drilling speed are the keys to reducing drilling costs (see drilling methods, drilling technology, completion).
Oil production engineering is the entire process of lifting oil and gas in oil wells from the bottom to the wellhead. The rise of oil and gas can rely on the energy of the formation to eject itself, or it can rely on artificially added energy such as oil pumps and gas lift. Various effective well workover measures can eliminate wax formation, water production, sand production and other failures that often occur in oil wells, and ensure normal production of oil wells. Production stimulation measures such as hydraulic fracturing or acidification can increase the production capacity that is reduced due to low permeability of the oil layer or improper drilling techniques that contaminate or damage the oil and gas layer. For injection wells, it is to improve the injection capacity (see oil production methods, gas production technology, layered production technology, oil and gas well stimulation technology).
The oil and gas gathering and transportation project is a complete process technology for the collection, separation, processing, measurement, storage and transportation of oil and gas in the oil field. The mixed fluids such as oil, gas and water extracted from the well are separated and initially processed in the mine to obtain as much oil and gas products as possible. Water can be reinjected or used to prevent environmental contamination. Reduce ineffective losses (see oilfield oil and gas gathering and transportation).
The relationship between various disciplines and engineering technology in petroleum extraction is shown in the figure.
Petroleum Extraction
The Development of Petroleum Extraction Technology The large-scale exploitation and application of oil and natural gas took place in the past century. The United States and Russia began their respective modern oil and gas extraction industries in the 1850s. Other countries are a little later. The development of oil extraction technology is closely related to the development of mathematics, mechanics, geology, physics, mechanical engineering, electronics and other disciplines. It can be roughly divided into three stages:
The initial stage is from the end of the 19th century to the 1930s. With the emergence of internal combustion engines, urgent requirements have been placed on oil. The main technical sign of this stage is the use of natural energy mining. The average oil recovery rate is only 15 to 20%, the drilling depth is not large, and the only means of observing the oil reservoir are simple thermometers and pressure gauges.
The second stage, from the late 1930s to the late 1950s, was marked by the establishment of a theoretical system for oil field development. The main contents are: ① The formation of rock mechanics as the theoretical basis of drilling engineering; ② The reservoir physics and seepage mechanics system are basically established, and water injection production technology that artificially increases reservoir energy is widely used. In the Soviet Union, the technology of early water injection to maintain formation pressure was widely used, which increased the ultimate oil recovery rate from 15 to 20% in the 1930s to more than 30%. Logging technology centered on electrical logging methods and drilling 4500 Drilling technology for ultra-deep wells over 1 meter. Petroleum stabilization technology based on oil and gas phase equilibrium theory is widely used in the mine gathering and transportation process. The applied science and engineering technology system related to oil and gas field development and extraction has been basically established.
The third stage began in the 1960s, marked by the widespread use of electronic computers and modern science and technology in oil and gas field development, and the rapid development of development technology.
The main aspects are: ① The established sedimentary facies model of various oil layers improves the ability to predict the heterogeneity and continuity of oil storage sand bodies, thereby enabling more economical and effective well location and development work; ② Integrating modern Nuclear technology in physics is applied to well logging to form radioactive logging technology. Together with the original electrical logging technology, plus the new production logging series, it can be used to directly measure the distribution of oil, gas, and water in the reservoir. More effective measures can be taken at different development stages; ③ Have a deeper understanding of the surface phenomena inside the oil and gas reservoir that play a role in the oil and gas production process and the rules of multiphase seepage in porous media, and based on physical Models and mathematical models have moved from qualitative to quantitative explanations of these phenomena (see numerical simulation of oil reservoirs), and new technologies for improving oil recovery besides water injection have been tested and developed; ④ Optimized drilling technology based on jet drilling and balanced drilling has rapidly develop. Drilling speed has been greatly improved. Various special types of wells can be drilled, including cluster wells, directional wells, and even horizontal wells. The addition of high-quality mud can minimize the pollution of the oil layer during the drilling process; ⑤ The application of large-scale acid fracturing technology has enabled many people who did not have the ability to drill in the past. Economically valuable oil and gas reservoirs, especially tight gas reservoirs, can be put into development, greatly increasing the utilization of natural resources. The difficulties caused by sand production, wax formation and high water content in oil wells have been solved to a large extent (see heavy oil production, oil well wax prevention and wax removal, oil well sand control and sand removal, water-oil ratio control); ⑥ Injecting steam into oil layers and the application of thermal recovery technology have enabled many heavy oil reservoirs to be developed; ⑦ The automation and electronic monitoring of oil and gas separation technology and gas processing technology have reduced the losses in oil and gas gathering and transportation in mines to a very low level. lower and provide higher quality products.
A method of lifting oil from the bottom of the well to the surface by relying on the oil reservoir itself or using artificially supplied energy. In the late 1850s, oil wells specialized in extracting oil appeared. In the early days, oil wells were very shallow and were pumped with buckets. Later, as the well depth increased, the oil production methods gradually became more complicated, which were divided into two categories: self-injection oil production method and artificial lift oil production method. The latter includes gas lift oil production method and pump oil production method (also known as deep well pump oil production method).
Self-injection oil production method: When the reservoir pressure is higher than the pressure of the fluid column in the well, the oil in the reservoir is lifted to the outside of the well through the oil pipe and the Christmas tree. The large amount of associated natural gas in oil can reduce the proportion of fluid in the well and reduce the fluid column pressure, making the oil well more likely to blow out. Reservoir pressure and gas-to-oil ratio (known as oil-to-gas ratio in Chinese petroleum mines) are the two main indicators of the spontaneous blowout capability of oil wells.
Oil and gas flow upward along the tubing in the well at the same time, and their energy is mainly consumed by gravity and friction. Under certain reservoir pressure and oil-gas ratio conditions, when the tubing size and depth in each well remain unchanged, there is an optimal flow rate range that fully utilizes energy, that is, the optimal daily production range. It is necessary to select a reasonable tubing size and adjust the size of the wellhead choke (often called a nozzle) to match the output of the self-blowout well with the oil supply capacity of the oil layer to ensure that the self-blowout well produces within the optimal production range.
In order to seal the wellhead and facilitate well repair and replacement of damaged parts, a special oil production device, called a Christmas tree (see color picture), is installed at the wellhead of the self-blowout well. The well structure of the self-flow well is shown in the figure. Spouting wells are easy to manage, have high production capacity and low consumption. They are an ideal oil production method. Many oil fields adopt early water injection and gas injection (see water injection production) measures to maintain reservoir pressure and extend the spontaneous eruption period of oil wells.
Artificial lift oil production method: A method of artificially adding energy to the bottom of the oil well to lift the oil in the reservoir to the wellhead. As the total amount of oil produced continues to increase, the pressure of the oil reservoir is decreasing day by day; in oil fields developed by water injection, the water production percentage of oil wells gradually increases, which increases the proportion of fluid. Both of these situations gradually weaken the self-blowing ability of oil wells. In order to increase production, artificial lift oil production (also known as mechanical oil production) needs to be adopted, which is the main method of oil field production. Especially in the later stage of oil field development, there are two methods: pump oil production method and gas lift oil production method.
Gas lift production method: Inject natural gas into the well from the casing annulus or the oil pipe to reduce the proportion of the fluid in the well, so that the pressure of the fluid column in the well is lower than the reduced oil layer pressure, thereby removing the fluid from the well. The tubing or casing annulus is led out of the well. There are two types: continuous gas lift and intermittent gas lift. In most cases, gas is injected from the casing annulus and oil is discharged from the tubing. Gas lift oil recovery requires a relatively sufficient source of natural gas; air cannot be used to avoid explosion. The starting pressure and working pressure of gas lift are quite different.
It is often necessary to install a special gas lift valve underground to reduce the starting pressure, so that the compressor can work at a lower pressure and improve its efficiency. The structure and working principle are shown in the figure. When the liquid level outside the oil pipe is pressed below the gas lift valve, air enters the oil pipe from hole A, causing the liquid in the pipe to mix with the air and spray out to the ground. When the pressure in the pipe drops to a certain level, the pressure difference between the inside and outside of the oil pipe causes the valve to close. The liquid level outside the tube can continue to drop. When the oil well is deep, several gas lift valves can be installed to lower the liquid level to the tubing shoe, thereby greatly reducing the starting pressure.
Gas lift oil production method:
After the oil and gas produced in the gas lift well are separated, the gas is concentrated to the mine compressor station, and is compressed and sent back to the wellhead. For some low-yield oil wells, the intermittent gas lift method can be used to save gas volume, and sometimes the piston gas lift method is also used cyclically.
The gas lift method has higher production capacity. The underground installation is simple and has no moving parts. The underground equipment has a long service life and is easy to manage. Although the one-time investment in building a compressor station and laying ground pipelines is high, the total investment and management costs are the lowest compared with pumping units, electric submersible pumps or hydraulic piston pumps. The gas lift method has a short application time, generally about 15 to 30%; the energy consumption per unit output is high and a large amount of natural gas is required; it is only suitable for high-yield oil wells and oil wells with a certain reservoir pressure in areas with natural gas sources and the above conditions. Directional wells are not suitable for use when the reservoir pressure drops to a certain minimum value; the efficiency is low.
Pump extraction oil production method: a type of artificial lift oil production method (see artificial lift oil production method). The method of lowering an oil pump into an oil well and pumping the liquid produced in the oil reservoir to the surface is referred to as the oil pumping method. The oil pumps used in this method are divided into rod and rodless categories according to the power transmission mode.
The rod pump is the most commonly used single-cylinder single-acting oil pump (Figure 1). Its oil discharge volume depends on the pump diameter and the stroke and number of strokes of the pump. There are two types of rod pumps: rod pumps and tube pumps. A complete rod pump unit includes a pumping unit, a rod string and a pump (Figure 2).
Pump extraction methodPump extraction method
The oil pumping unit mainly converts the circular motion of the power machine (usually an electric motor) into a reciprocating linear motion, driving the sucker rod and pump. There are two types of pumping units: beam type and beamless type. The former is the most commonly used, and the chain pumping units used in some mines in China belong to the latter type (see color picture). The sucker rod string is a long rod string that connects the oil pumping unit and the oil pump. It is more than a kilometer long. Due to the vibration and elastic deformation caused by alternating loads, the stroke of the suspension point of the sucker rod and the plunger stroke of the pump are relatively different. Big difference. The diameter, stroke, and number of strokes of the oil pump should be optimized through design calculations based on the production characteristics of each oil well. Install a gas separation device - an air anchor - at the inlet of the pump, or increase the depth of the pump to reduce the impact of the gas content in the fluid on the fullness of the oil pump (i.e. volumetric efficiency).
Pump oil extraction method
The rod pump is a self-weight system. When the cross-section of the sucker rod increases, its load also increases. The sinking depth of sucker rods made of various materials has a limit. To increase the sinking depth of the pump, the material, heat treatment process and grade of the sucker rod must be changed. According to the elasticity of the sucker rod and the characteristics of the formation fluid, when selecting the working system, a favorable combination of stroke and number of strokes should be selected. The working depth of the rod pump has exceeded 3000m abroad, and the load of the pumping unit has exceeded 25t. The displacement of the pump is related to the well depth. The daily displacement of some shallow wells can be as high as 400m3, and generally the medium-deep wells can reach 200m3. However, the output of the oil well Mainly based on the production capacity of the oil reservoir. The main advantages of the pump unit of the rod pumping unit are simple structure, convenient maintenance and management. The efficiency of the pump in medium and deep wells is about 50%, and it is suitable for wells with medium and low production. At present, more than 85% of the world's oil wells are produced by mechanical oil production methods, and most of them use rod pumps.
Rodless pump is suitable for medium-deep wells or deep wells and inclined wells with large production. Electric submersible pumps, hydraulic piston pumps and hydraulic jet pumps are used in industry.
The electric submersible pump is a pump unit in which a multi-stage centrifugal pump and an electric motor are directly connected. The power cable sends electricity to the motor downhole to drive the centrifugal pump and pump the fluid in the well to the surface. Since the pump unit is used in the casing, the diameter of the pump is limited, so it adopts a slender shape (Figure 3 ). In order to prevent underground fluids (especially water) from entering the armature and causing the motor to fail, a special sealing device must be adopted and a protector must be installed at the connection between the pump and the motor. The displacement of the pump is limited by the size of the wellbore, and the lift is determined by the number of stages of the pump, both of which depend on the power of the motor.
Electric submersible pumps are suitable for oil wells with medium to high liquid production, thin oil or water-containing crude oil containing less gas and sand. Generally, when the daily displacement is 100~1000m3 and the head is within 2000m, the efficiency is high and it can be used in inclined wells. It is relatively simple to build a well, easy to manage, has a long maintenance-free period, and the pump efficiency is about 60%; but it is not suitable for wells with high gas content and wells with corrosive fluids. The displacement of the pump cannot be adjusted after going down the well, and the cost of the pump assembly It is relatively high, and the lifting and maintenance operations are more complicated.
Pump extraction oil method
Hydraulic piston pump uses a surface pump to inject liquid to drive an underground hydraulic motor to drive an underground pump to pump underground liquid out of the ground. The working principle of a hydraulic piston pump is similar to that of a rod pump, except that the reciprocating motion is achieved with a hydraulic motor and a reversing valve (Figure 4). There are two types of downhole hydraulic piston pumps: single-acting and double-acting. Surface pumps all use high-pressure plunger pumps. There are two types of processes: ①Open process. The single-pipe structure uses low-viscosity crude oil as the power fluid, which can not only reduce the friction resistance of the pipeline, but also reduce the viscosity of the pumped oil, and mix it with the produced fluid to extract the ground. ②Closed process. Use light oil or water as the power fluid. When using water, add lubricants and preservatives. It circulates automatically and does not mix with the produced liquid. Only a small amount of replenishment is required during the working process. Hydraulic piston pumps can be operated in a single well, or a pump group can be built for centralized management. The displacement range is wide, from dozens to thousands of cubic meters per day, and is suitable for deep wells, high-lift wells, heavy oil wells, and inclined wells. The advantage is that the displacement can be adjusted arbitrarily, the oil pipe does not need to be removed when starting and discharging the pump, and the operation and management are convenient. The pump efficiency can reach more than 85%. The disadvantage is that an extra high-pressure pipeline needs to be built on the ground and the power fluid needs to be processed, which increases the cost of well construction and management.
Pump oil extraction method
Hydraulic jet pump Oil pump with nozzle and diffuser (Figure 5). The hydraulic jet pump has no moving parts, has a simple structure, low cost, and is easy to manage. However, the efficiency is low, not higher than 30-35%. The resulting production pressure difference is too small, and it is only suitable for high-pressure and high-yield wells. Generally, the hydraulic piston pump is only used in the early stage of the oil well, when the pressure of the oil well is high and the displacement is large; when the pressure decreases and the displacement decreases, the hydraulic piston pump is used.