Introduction to oil exploitation and exploitation technology

intro

Oil is a fluid mineral buried deep in the ground. At first, the oily liquid mineral produced in nature was called petroleum, the combustible gas was called natural gas, and the solid combustible oil mineral was called asphalt. With the in-depth study of these minerals, it is realized that they are hydrocarbon compounds in composition and are related to each other in genesis, so they are collectively called petroleum. In September 1983, the 11th World Petroleum Congress proposed that petroleum is a complex mixture consisting of gaseous, liquid and solid hydrocarbons that exist in nature, as well as a small amount of impurities. So oil extraction also includes gas extraction.

The role of oil in the national economy oil is an important energy, compared with coal, has the advantages of high energy density (the combustion heat of equal weight oil is 50% higher than that of standard coal), convenient transportation and storage, and less pollution to the atmosphere after combustion. Fuel oil derived from petroleum is the main fuel for various kilns in transport vehicles, power station boilers, the metallurgical industry and the building materials industry. Liquefied gas (LPG) and pipeline gas (PIped gas) with petroleum as raw materials are high quality fuels used in urban life. Aircraft, tanks, ships, rockets and other spacecraft also consume large amounts of petroleum fuel. Therefore, many countries have listed oil as a strategic material.

Since the 1970s, oil has surpassed coal in the composition of world energy consumption. In 1979, it accounted for 45 percent, and this situation is not expected to change much by the early 21st century. Petroleum products are also widely used as lubricants for various machinery. Asphalt is an important material for roads and buildings. Petrochemical products are widely used in agriculture, light industry, textile industry, medicine and health and other sectors, such as synthetic fiber, plastic, synthetic rubber products, has become a necessity for people's life.

In 1982, world oil production was 2,644 million tons and natural gas 1,582.9 billion cubic meters. Since 1973, three oil price increases and the 1982 oil price collapse have caused great fluctuations in the world economy (see World Oil Industry).

Oil and gas accumulation and driving mode After forming in the crust, oil and gas exist in the source gas in a dispersed state, and after migrating into the reservoir, it accumulates in the geological trap with good preservation conditions to form oil and gas reservoirs. There can be several oil and gas reservoirs in a geological structure, combined into oil and gas fields.

A rock formation with reservoir space that holds oil and gas and allows the flow of oil through it. The space in the reservoir contains the pores between the rock fragments, the cracks in the rock cracks, and the holes formed by dissolution. The pores are generally related to sedimentation, the cracks are mostly related to tectonic deformation, and the holes are often related to paleokarst. The size, distribution and connectivity of voids affect the flow of oil and gas and determine the characteristics of oil and gas exploitation (see petroleum Development Geology).

In the process of oil production, 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. There are mainly: (1) hydrostatic head formed by surface water recharge in water drive reservoir; (2) elastic water drive, the elastic expansion of surrounding closed water and reservoir rocks; (3) Dissolved gas drive, the expansion of the gas dissolved in the oil when the pressure is reduced; (4) Gas cap drive, when there is a gas cap, the expansion of gas cap gas with the reduction of pressure; ⑤ Gravity drive, gravity oil discharge. When the above natural energy is sufficient, oil and gas can be ejected from the wellhead. When the energy is insufficient, artificial lifting measures are needed to drive the oil flow out of the ground (see spontaneous injection oil production method, artificial lift oil production method).

Compared with the general solid mineral deposits, the characteristics of oil exploitation have three significant characteristics: (1) The object of exploitation continues to flow throughout the process of exploitation, the reservoir situation is constantly changing, all measures must be carried out in response to this situation, therefore, the entire process of oil and gas field exploitation is a process of continuous understanding and continuous improvement; ② The miner does not have direct contact with the ore body under normal circumstances. The exploitation of oil and gas, the understanding of the situation in the oil and gas reservoir and the various measures to exert influence on the oil and gas reservoir must be carried out by special logging. Some characteristics of a reservoir must be recognized during production, or even after a large number of Wells have been drilled, so exploration and production phases are often intertwined over a period of time (see field development planning and design).

In order to develop the reservoir well, it is necessary to have a comprehensive understanding of it, drill a certain number of exploratory Wells, and determine various boundaries of the reservoir (oil-water boundary, oil-gas boundary, segmentation fault, pinch-out line, etc.) with geophysical exploration data. It is necessary to drill a certain number of appraisal Wells to understand the properties of the oil and gas reservoir (generally, core is taken), including the changes in the thickness of the oil and gas reservoir, the physical properties of the reservoir, the reservoir fluid and its properties, the distribution of the temperature and pressure of the reservoir, etc., to conduct comprehensive research, so as to obtain a more comprehensive understanding of the oil and gas reservoir. The reservoir itself should not be studied, but the adjacent aquifer and the connection between them should be studied at the same time (see reservoir physics).

In the process of exploitation, it is also necessary to exploit, observe and control the oil and gas reservoirs through production Wells, injection Wells and observation Wells. The flow of oil and gas has three interrelated processes: (1) Oil and gas flow from the reservoir to the bottom of the well; ② From the bottom of the well to the top of the well; (3) From the wellhead flows into the oil gathering station, after separation and dehydration treatment, flows into the oil and gas transport terminal, and then exports to the mining area (see reservoir engineering).

Oil exploitation technology

Logging engineering applies geophysical methods in the wellbore. The information of the original condition and changes in the drilled rock strata and oil and gas reservoirs, especially the distribution of oil, gas and water in the reservoir and its changes, is transmitted to the surface through cables. Based on the comprehensive judgment, the technical measures to be taken are determined (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 hundreds or even thousands of Wells or more. There are different technical requirements for Wells used for different purposes of production, observation and control (e.g. production Wells, injection Wells, observation Wells and inspection Wells designed to check the effect of washing oil). The well should be drilled with minimal contamination to the reservoir, high cementing quality, and be able to withstand various downhole operations over several decades of production. Improving drilling technology and management and increasing drilling speed are key to reducing drilling costs (see Drilling Methods, Drilling Processes, completions).

Oil recovery engineering is the whole process technology of lifting oil and gas from the bottom of the well to the wellhead. The rise of oil and gas can depend on the energy injection from the formation, or on the artificial energy extraction such as pumping pump and gas lift. All kinds of effective workover measures can eliminate the frequent problems of wax formation, water discharge and sand production, and ensure the normal production of oil Wells. Stimulation, such as hydraulic fracturing or acidification, can increase production that has been reduced due to low reservoir permeability or improper drilling practices that contaminate and damage the reservoir. In the case of injection Wells, it is to improve the injection capacity (see oil production method, gas production technology, stratified production technology, oil and gas well stimulation technology).

Oil and gas gathering and transportation engineering is a technology to build a complete oil and gas collection, separation, treatment, measurement, storage and transportation in the oil field. The oil, gas, water and other mixed fluids produced in the well are separated and initially treated in the mine field to obtain as much oil and gas products as possible. Water can be reinjected or used to prevent pollution of the environment. Reduce ineffective losses (see oil and gas gathering in the field).

The relationship between various disciplines and engineering techniques in oil extraction is shown in the figure. The development of oil extraction technology The large-scale exploitation and application of oil and natural gas is a matter of nearly a hundred years. The United States and Russia began their modern oil and gas extraction industries in the 1850s. Other countries are a little later. The development of petroleum exploitation technology is closely related to the development of mathematics, mechanics, geology, physics, mechanical engineering, electronics and other disciplines. It can be divided into three stages:

The initial period was from the late 19th century to the 1930s. With the appearance of internal combustion engine, there is an urgent demand for oil. The main technical symbol of this stage is the exploitation of natural energy. The average recovery rate of oil is only 15-20%, the drilling depth is not large, and the means of observing the reservoir are only simple thermometers and pressure gauges.

The second stage, from the late 1930s to the late 1950s, was marked by the establishment of the theoretical system of oil field development. The main contents are: (1) Forming rock mechanics as the theoretical basis of drilling engineering; ② The reservoir physical and seepage mechanics system has been basically established, and the water injection production technology of artificially replenishing reservoir energy is generally adopted. In the Soviet Union, the technology of water injection to maintain formation pressure was widely used in the early stage, so that the ultimate oil recovery rate increased from 15 to 20% in the 1930s to more than 30%, and the development of logging technology centered on electrical measurement methods and drilling technology of ultra-deep Wells above 4500 meters. The oil stabilization technology based on the theory of oil and gas phase equilibrium has been widely used in the field gathering and transportation process. The applied science and engineering technology system related to the development and exploitation of oil and gas fields 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 the development of oil and gas fields, and the rapid development of development technology. The main aspects are as follows: (1) The establishment of sedimentary facies models of various oil formations improves the ability to predict the heterogeneity and continuity of oil reservoir sand bodies, so that well placement and development work can be more economical and effective; (2) The application of nuclear technology in modern physics to logging, the formation of radioactive logging technology, and the original electrical measurement technology, coupled with the new production logging series, can be used to directly determine the distribution of oil, gas and water in the reservoir, in different development stages can take more effective measures; (3) Have a deeper understanding of the surface phenomena that play a role in the process of oil and gas production and the law of multi-phase seepage in porous media, and based on physical and mathematical models to explain these phenomena from qualitative to quantitative (see reservoir numerical simulation), test and develop new technologies other than water injection to enhance oil recovery; (4) The optimized drilling technology based on jet drilling and balanced drilling has developed rapidly. The drilling rate has been greatly improved. Can be drilled a variety of special types of Wells, including cluster Wells, directional Wells, and even horizontal Wells, coupled with high-quality mud, so that the drilling process to minimize the pollution of the reservoir; ⑤ The application of large-scale acidizing fracturing technology has made many oil and gas reservoirs, especially tight gas reservoirs, which have no economic value in the past, 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 recovery, oil well wax prevention and wax removal, oil well sand control and sand removal, water to oil ratio control); The application of steam injection to the reservoir and thermal production technology has put many heavy oil reservoirs into development; The automation and electronic monitoring of oil and gas separation technology and gas treatment technology can reduce the loss of oil and gas gathering and transportation in the field to a very low level, and can provide higher quality products.

Offshore oil and gas development Offshore oil and gas development is not very different from that on land, except that the construction of the production platform is much more expensive, so the evaluation of the field scope is more careful. Risk analysis should be carried out to accurately select the platform location and construction scale. Avoid the loss caused by unclear understanding of underground reservoir or wrong inference. Since the 1960s, the prospect of the development of China's oilfield service industry and investment strategic planning offshore oil development has made great progress. Offshore oil production has reached about 20% of the world's total oil production. Formed a complete set of offshore mining and gathering and transportation of special equipment and technology. The construction of the platform has been able to withstand various disasters such as wind, waves, ice flow and earthquakes, and the water depth of the oil and gas fields has exceeded 200 meters.