As a key channel for the transportation of offshore oil and gas resources, submarine oil pipelines have a complex and high cost structure. Compared with onshore and general offshore oil pipelines, submarine oil pipelines face many challenges in construction, operation and maintenance due to their special submarine environment, which leads to unique characteristics in cost. The following is a detailed analysis of the cost of submarine oil pipelines.

1. Construction cost

(I) Preliminary planning and design cost

Detailed geological survey: Due to the complex and changeable geological conditions of the submarine, it is necessary to use advanced multi-beam depth sounders, shallow layer profilers, geological drilling equipment and other equipment to accurately detect information such as submarine topography, geological structure, soil type and properties. For example, in deep-sea areas, in order to obtain accurate geological data, professional marine survey ships equipped with high-precision detection instruments are required. The survey cycle is long and the cost is high. The cost of a single survey can reach tens of millions of yuan.

Complex environment assessment: Long-term monitoring and analysis of the marine hydrological environment, such as tides, waves, currents, seawater temperature and salinity, to assess their impact on pipeline construction and operation. At the same time, the seabed ecological environment must also be considered to avoid damage to marine habitats, coral reefs, etc. This involves a professional ecological assessment team and a complex assessment process, and the cost is usually in the millions to tens of millions of yuan.

Customized design: Based on the survey and assessment results, a pipeline solution that adapts to the special environment of the seabed is designed. Including pipeline strength design, it is necessary to consider factors such as uneven seabed settlement and seismic activity; anti-corrosion design, formulate special anti-corrosion measures for the strong corrosiveness of seawater; stability design, to ensure that the pipeline will not be displaced or damaged on the seabed due to water flow, seabed movement, etc. The design process requires a professional marine engineering design team, using advanced design software and simulation technology. The design fee generally accounts for 5% - 10% of the total construction cost of the project. For large-scale submarine oil pipeline projects, the design fee may be as high as hundreds of millions of yuan.

(II) Material cost

High-performance pipeline materials: In order to withstand seawater corrosion, high pressure and complex geological stress on the seabed, high-strength, corrosion-resistant alloy steels are usually used, such as X65, X80 and other steel grade pipeline steels. Compared with ordinary carbon steel, these alloy steels are several times more expensive. The diameter and wall thickness of the pipeline also have a significant impact on the cost. The manufacturing process of large-diameter and thick-walled steel pipes is complex, and the materials used are more, which greatly increases the cost. For example, the price per ton of high-strength alloy steel pipes with a diameter of 1200mm and a wall thickness of 25mm is thousands of yuan higher than that of ordinary steel pipes with a diameter of 600mm and a wall thickness of 15mm.

Multi-layer anti-corrosion materials: To prevent seawater corrosion, steel pipes need to be subjected to multiple anti-corrosion treatments. Common anti-corrosion coatings include three-layer polyethylene (3PE), fused epoxy powder (FBE), etc., and the cost per square meter can reach hundreds of yuan. In some areas with particularly harsh corrosion environments, additional cathodic protection systems are required, including sacrificial anode materials (such as zinc alloys, aluminum alloys), reference electrodes, test piles, etc., which further increase material costs.

Special pipe fittings and connection materials: elbows, tees, reducers and other pipe fittings are used to change the direction of the pipeline and connect pipelines of different diameters. Since the submarine environment has extremely high requirements for the strength, sealing and corrosion resistance of pipe fittings, pipe fittings made of the same material as the pipeline are usually used, and their manufacturing process is complex and the cost is high. Pipe fittings of special specifications and shapes, such as large-angle elbows and high-pressure tees, are more expensive, and the price of a single pipe fitting can reach tens of thousands of yuan or even higher. In terms of connection materials, in order to ensure the reliability and sealing of the connection, high-strength, corrosion-resistant stainless steel flanges, alloy bolts, and oil-resistant and seawater-resistant rubber or metal spiral wound gaskets are required, and the cost is relatively high.

Insulation and counterweight materials: When transporting high-freezing point crude oil or low-temperature natural gas, the pipeline needs to be insulated. Commonly used insulation materials at sea include polyurethane foam, glass fiber, etc. Polyurethane foam has good insulation performance, but the price is relatively high, about several thousand yuan per cubic meter. In order to ensure the stability of the pipeline on the seabed and prevent displacement or floating due to water flow, waves, etc., a counterweight layer needs to be added to the outer surface of the pipeline. Commonly used counterweight materials include concrete and asphalt sand. The cost of concrete counterweight is relatively low, but the construction process is complicated; asphalt sand counterweight is easy to construct, but the price is high.

(III) Construction cost

Professional pipe-laying vessel rental: Pipe-laying vessels are the core equipment for laying submarine oil pipelines. According to different pipe-laying methods (such as S-type pipe-laying, J-type pipe-laying, reel-type pipe-laying, etc.) and pipe diameter and water depth requirements, the specifications and performance of pipe-laying vessels vary greatly, and the rental costs also vary greatly. The daily rental of large pipe-laying vessels can reach hundreds of thousands or even millions of yuan, and the rental period is usually long, ranging from several months to several years, which makes the rental cost of pipe-laying vessels an important part of the construction cost. For example, laying large-diameter pipelines in deep-sea areas requires large pipe-laying vessels equipped with advanced dynamic positioning systems and high-precision pipe-laying equipment, and their rental costs are extremely high.

Lifting and diving equipment investment: Crane vessels are used to lift pipelines, pipe fittings and install other submarine facilities. The lifting capacity of crane vessels is different, and the rental fee also varies greatly. Large crane vessels with a lifting capacity of more than 1,000 tons can be rented for tens of thousands to hundreds of thousands of yuan per day. In complex construction environments, multiple crane vessels may be required to work together, further increasing the rental cost. At the same time, diving equipment is used for underwater pipeline connection, inspection and maintenance. Divers have a high salary level, and the cost of each diving operation can reach tens of thousands of yuan. The purchase and maintenance costs of diving equipment cannot be ignored.

Offshore construction auxiliary engineering: During the construction process, temporary offshore platforms need to be built to facilitate equipment parking, material stacking and personnel operations. The construction cost of temporary offshore platforms depends on the scale, structural form and service life of the platform. Simple floating platforms have relatively low costs, but poor stability; fixed platforms have good stability, but high construction costs, which may cost millions to tens of millions of yuan. In addition, construction ships consume a lot of fuel during operations, and fluctuations in fuel prices have a greater impact on construction costs. The daily fuel consumption cost of a large pipe-laying ship can reach tens of thousands of yuan, and the accumulated fuel costs of the entire construction period are a considerable expense.

Cost of high-difficulty construction technology: The construction of submarine oil pipelines often faces complex submarine terrain and harsh marine environment, and special construction technology is required. For example, when laying pipelines on deep-sea soft soil foundations, pre-pressing treatment, pile foundation support and other technologies may be required, which increases the construction cost. In narrow straits or areas close to the coast, construction also needs to consider the mutual influence with other offshore facilities and take corresponding protection and coordination measures, which will also lead to rising costs.

(IV) Equipment procurement cost

Advanced detection equipment: To ensure the safe operation of submarine oil pipelines, advanced pipeline detection equipment such as magnetic flux leakage detection equipment, ultrasonic detection equipment, and intelligent pipe cleaners are required. These equipment are expensive. The price of an advanced magnetic flux leakage detection equipment can reach millions of yuan, and the unit price of an intelligent pipe cleaner is also around hundreds of thousands of yuan. Due to the complex submarine environment, higher reliability and adaptability requirements are required for detection equipment, which further increases the equipment procurement cost.

Automated monitoring and control system: including pressure sensors, temperature sensors, flow sensors, data acquisition and transmission systems, remote monitoring center equipment, etc., which are used to monitor the operating parameters of pipelines in real time and realize automated control of pipelines. The cost of monitoring and control system equipment depends on the scale, technological advancement and brand of the system. The purchase cost of a complete set of submarine oil pipeline monitoring and control system equipment may be as high as tens of millions of yuan. In the submarine environment, the equipment must also have good waterproof and anti-corrosion properties, which will also increase the purchase cost of the equipment.

Emergency treatment equipment: such as offshore oil spill emergency recovery equipment, underwater welding equipment, emergency shut-off devices, etc. These equipment are important guarantees for dealing with emergencies and have high purchase costs. The price of a large offshore oil spill emergency recovery ship can reach tens of millions of yuan. The purchase cost of underwater welding equipment and emergency shut-off devices also varies according to their performance and specifications, usually ranging from several million yuan to tens of millions of yuan.

2. Operating costs

(I) Energy consumption cost

Pump unit and compressor unit energy consumption: In order to overcome the transportation resistance of crude oil or natural gas in the pipeline and maintain a certain transportation pressure and flow, pump units and compressor units are required. The power depends on factors such as the length of the pipeline, the diameter of the pipe, the nature of the conveying medium and the conveying volume. Since submarine oil pipelines are usually long and the transportation conditions are complex, the operation time of pump units and compressor units is long, and the total energy consumption is large. For example, a 200-kilometer-long, 1,000-mm-diameter submarine crude oil pipeline can consume millions of kWh of electricity per year for its pump unit. According to local electricity prices, the electricity bill is considerable. When transporting natural gas, the energy consumption of the compressor unit is even higher. The power of a large natural gas compressor unit can reach several megawatts, and the annual energy consumption cost can reach tens of millions of yuan.

Increased energy consumption under special circumstances: The ambient temperature on the seabed is low. In order to prevent the solidification of crude oil or the formation of natural gas hydrates, the transport medium may need to be heated or insulated, which will further increase the energy consumption cost. In addition, in order to deal with possible blockages and leaks in submarine pipelines, some auxiliary equipment such as pig launchers and online monitoring systems also need to consume energy continuously.

(II) Maintenance and repair costs

Regular inspections and monitoring: Regular inspections of pipelines are carried out by divers, underwater robots (ROVs) or aerial inspections to check the corrosion of pipelines, structural integrity, and the operating status of ancillary facilities. Diver inspections are expensive, and each diving operation can cost tens of thousands of yuan; underwater robot inspections are relatively inexpensive, but equipment purchase and maintenance costs also require a certain amount of investment. Aerial inspections can quickly cover large areas, but are subject to greater restrictions on weather conditions and have higher flight costs. At the same time, it is also necessary to regularly inspect and maintain the anti-corrosion coatings and cathodic protection systems of pipelines, and the costs are related to the degree of corrosion of the pipelines, the life of the anti-corrosion coatings, and the maintenance process. Generally speaking, the annual anti-corrosion maintenance costs of submarine oil pipelines account for a certain proportion of the pipeline construction costs. As the service life of the pipelines increases, the anti-corrosion maintenance costs are on the rise.

Equipment maintenance and repair: Regular maintenance of equipment such as pump units, compressor units, valves, and instruments, including replacement of lubricating oil, filters, and wearing parts, to ensure the normal operation of the equipment. Equipment maintenance costs are related to the number, type, and frequency of use of the equipment, and the maintenance costs of large equipment are relatively high. When a pipeline or equipment fails, the maintenance work is difficult and risky, and requires a lot of manpower, material, and financial resources. During the maintenance process, it may be necessary to use professional emergency repair equipment, such as underwater welding equipment, plugging equipment, etc. At the same time, it is necessary to organize emergency rescue teams and coordinate offshore operating resources. Emergency repair costs are often difficult to estimate. The cost of emergency repairs for a serious pipeline accident may be as high as tens of millions or even hundreds of millions of yuan.

(III) Personnel costs

Salary of professional operation and management personnel: including offshore platform operators, pipeline monitoring center staff, maintenance technicians, managers, etc. These personnel must have professional knowledge and skills and be familiar with the operation and management process of submarine oil pipelines. The salary level of operation and management personnel varies according to their position, experience and skill level, and the overall salary level is relatively high. For example, the monthly salary of senior operators on offshore platforms can reach tens of thousands of yuan, and the annual salary of managers can reach hundreds of thousands of yuan. Due to the harsh working environment, additional sea subsidies and insurance costs must be paid, which further increases labor costs.

Continuous training costs: In order to improve the professional quality and skill level of employees and ensure that they can master equipment operation and emergency response methods, regular training is required. The training content includes safety production knowledge, equipment operating procedures, new technology applications, etc. Training costs include training instructor fees, training material fees, employee wages and benefits during training, etc. The annual training costs also account for a certain proportion of personnel costs.

(IV) Safety and environmental protection costs

Strengthen investment in safety facilities: In order to timely discover safety hazards of pipelines, it is necessary to continuously upgrade and improve the safety monitoring system, such as installing more advanced leak detection sensors, stress monitoring equipment, etc. The upgrade cost of the safety monitoring system depends on the purchase cost of the equipment, the installation and commissioning costs, and the subsequent maintenance costs, which usually require a large amount of money. Regularly update and maintain emergency rescue equipment to ensure that it can be used normally at critical moments. The update cycle of emergency rescue equipment is generally several years, and the cost of each update depends on the type and quantity of equipment, which may cost millions to tens of millions of yuan. Organize employees to conduct safety training and emergency drills to improve their safety awareness and emergency response capabilities. The cost of safety training and drills includes training instructor fees, drill material fees, site rental fees, etc., and the annual cost expenditure cannot be ignored.

Strict environmental protection costs: Regularly monitor the marine environment around the submarine oil pipeline, including water quality, biodiversity, marine ecology, etc. Marine environmental monitoring requires professional monitoring equipment and technicians, and the monitoring costs are high, which can reach millions of yuan per year. Pollutants such as sewage, waste gas, and waste residue generated during pipeline operation are treated to ensure that they meet emission standards. Sewage treatment requires the construction of special sewage treatment facilities, waste gas treatment requires the use of desulfurization, denitrification, dust removal and other equipment, and waste residue treatment requires classified collection, transportation and disposal. The cost of pollutant treatment is related to the amount of pollutants generated, the treatment process and the emission standards, and is usually a considerable expense. If the construction and operation of submarine oil pipelines cause certain damage to the marine ecological environment, ecological compensation fees may need to be paid for ecological restoration and protection. The specific amount of ecological compensation fees depends on the degree of ecological damage and the provisions of relevant laws and regulations, and may involve tens of millions of yuan or even more.

3. Other costs

(I) Financing costs

Huge loan interest: Subsea oil pipeline projects require huge investments, and companies usually need to raise funds through bank loans and other means. The level of loan interest depends on factors such as the loan amount, loan interest rate and loan term. At present, the loan amount of large-scale subsea oil pipeline projects can reach billions or even tens of billions of yuan. The loan interest rate generally refers to the market interest rate of the same period, and the loan term is relatively long, up to more than 10 years. Taking a loan amount of 5 billion yuan, an annual interest rate of 5%, and a loan term of 15 years as an example, the annual loan interest expenditure is as high as 250 million yuan.

Bond issuance-related costs: Some companies will raise funds by issuing bonds. During the bond issuance process, they need to pay a series of fees such as underwriting fees, rating fees, legal fees, and audit fees. Bond issuance costs generally account for a certain proportion of the bond issuance amount. The specific proportion depends on the size of the bond, credit rating, and market conditions, and is usually between 1% and 3%. For example, the issuance cost of a bond with a scale of 1 billion yuan may be between 10 million yuan and 30 million yuan.

(II) Insurance costs

High property insurance costs: In order to protect the property safety of submarine oil pipelines and related facilities when they are hit by natural disasters (such as typhoons, tsunamis, earthquakes, etc.) and accidents (such as collisions, fires, explosions, etc.), property insurance needs to be purchased. Since the insurance subject value of submarine oil pipeline projects is huge and the risks are high, the property insurance costs are relatively high. Generally speaking, the property insurance costs account for a certain proportion of the total project investment, about 0.5% - 1.5%. For example, for a submarine oil pipeline project with a total investment of 10 billion yuan, the annual property insurance costs may be between 50 million yuan and 150 million yuan.

Liability insurance costs: mainly include oil pollution liability insurance, third-party liability insurance, etc., which are used to bear the compensation liability for personal injury and property damage caused to third parties by accidents such as submarine oil pipeline leakage. Liability insurance costs are also related to risk assessment results and insurance terms, and there may be differences in quotations from different insurance companies. Liability insurance costs also account for a certain proportion of the entire insurance cost, and the specific value needs to be determined based on the actual situation of the project.

(III) Management costs

Project management costs: During the construction and operation of a project, a special project management team needs to be established to be responsible for the planning, organization, coordination and control of the project. Project management costs include salary and benefits of management personnel, office space rental, office equipment purchase, travel expenses, etc. The size and management complexity of the project management team vary from project to project. The project management costs of large submarine oil pipeline projects can reach tens of millions of yuan each year.

Administrative costs: The costs incurred by the corporate headquarters for administrative management of submarine oil pipeline projects, including the salaries of senior management personnel, office expenses of the administrative department, meeting expenses, etc. Administrative costs are generally allocated to each project in a certain proportion. Although the administrative costs allocated to a single project are relatively small, from the perspective of the company as a whole, it is also a cost that cannot be ignored.

(IV) Decommissioning costs

Complex pipeline dismantling costs: Subsea oil pipelines need to be dismantled after they reach the end of their service life. Pipeline dismantling is difficult and requires the use of professional dismantling equipment, such as cutting equipment and lifting equipment. At the same time, safety risks and environmental protection requirements during the dismantling process must also be considered. The cost of pipeline removal is related to the length, diameter, material and removal method of the pipeline. Generally speaking, the removal cost is high and may account for a certain proportion of the pipeline construction cost, about 20% - 50%. For example, the removal cost of an undersea oil pipeline with a construction cost of 1 billion yuan may be between 200 million yuan and 500 million yuan.

Comprehensive site cleaning and ecological restoration costs: After the pipeline is removed, the offshore platform, submarine foundation and other facilities need to be cleaned up to restore the marine ecological environment. Site cleaning costs include equipment transportation, waste disposal and other costs, and ecological restoration costs are used to repair the damage to the marine ecology caused by pipeline construction and operation, such as marine habitat restoration and beach restoration. Site cleaning and ecological restoration costs are difficult to accurately estimate. The specific amount depends on the scale of the project and the degree of ecological damage, and a large amount of funds may be required.

In summary, the cost structure of undersea oil pipelines is complex and high. In the process of project investment decision-making and cost control, it is necessary to fully consider various factors and formulate scientific and reasonable plans to ensure the smooth implementation of the project and the realization of economic benefits. At the same time, with the continuous advancement of technology and the improvement of management level, it is expected to reduce costs through innovation and improve the competitiveness of undersea oil pipeline projects.