The horizontal section of China Petroleum's terrestrial shale oil has a length of 1500-2500 meters, with the longest exceeding 5000 meters (HuaH90-3 well, 5060 meters). More than 50% of the 1500 meter long horizontal section can be drilled in one go, and some wells can achieve a drilling depth of up to 3000 meters in one go.As shown in Table 1, the horizontal wells of Longdong shale oil and Gulong shale oil are comparable to North America in terms of horizontal section length and mechanical drilling speed; The horizontal drilling of shale oil in Jimsar is limited by complex geological conditions, inadequate drilling speed technology, and other factors, resulting in a gap in overall drilling indicators compared to North America.

The domestic onshore shale oil drilling indicators are the optimal years for each block: Longdong shale oil is in 2021, Jimusaer shale oil is in 2023, and Gulong shale oil is in 2022. The drilling cycle is the total time from the first start of drilling to completion (the end of the entire drilling phase).

2.1.2 Typical Block Benchmarking

As shown in Table 2, the burial depth, temperature and pressure characteristics of Longdong shale oil are similar to those of North American Permian shale oil, and the drilling cycle is basically the same. However, more than 50% of wells with Permian shale oil horizontal segments longer than 3000 meters have been drilled, and the average horizontal segment length difference of Longdong shale oil is 1000 meters; The drilling capacity and mechanical drilling speed of Longdong shale oil are only 50% of those of Permian shale oil. At present, Longdong shale oil is developing towards a low-cost and efficient well factory development model, and there is still potential for improvement in the proportion of "one trip drilling" and mechanical drilling speed.

2.2 Key Drilling Technology Benchmarking

2.2.1 Well layout and wellbore structure

The domestic shale oil single-layer platform layout mainly consists of 4-6 wells, while the double-layer platform layout mainly consists of 8-10 wells, with a maximum of 31 wells; The length of the horizontal section is mainly 1500-2500 meters; The overall wellbore structure is mainly composed of a three opening to a two opening wellbore structure.Foreign shale oil is developed in a three-dimensional manner with small well spacing of 4 to 5 layers, with 16 wells per platform becoming the norm, up to a maximum of 5 layers/64 wells; The wellbore structure is a two or three opening wellbore structure; Ultra long horizontal wells with a length greater than 3000 meters have become the mainstream development model for shale oil in North America.In recent years, in order to further reduce development costs and increase single well production, North American shale oil has innovatively formed "U-shaped" and "W-shaped" horizontal section wells, as shown in Figure 5.In 2020, the first "U-shaped" horizontal section well was implemented by Chesapeake Energy in the Eagle Ford block, using screws, drilling tools, and hydraulic oscillators.

The development of shale oil in China is mainly based on platform drilling, and the drilling method and wellbore structure are basically similar to those in foreign countries. However, due to various factors such as geological conditions, there is still a gap between the platform scale, horizontal section length, and complex horizontal section trajectory design and those in North America.

2.2.2 Geological Engineering Integration and Guidance Technology

According to the integration of geological engineering, extensive applications have been made in well deployment, drilling design, geological guidance, geomechanical modeling, and other aspects, achieving preliminary results. An integrated software platform for interdisciplinary collaborative research and work has not yet been developed. The integrated and collaborative mechanism of geological engineering, including geophysical exploration, drilling, completion, logging, and logging, needs to be further improved. The domestic and international benchmarking situation is shown in Table 3.

In terms of rotational geological guidance, most domestic related products are primary products or prototypes, with only a few having the ability to promote and apply them. There is still a significant gap compared to the internationally leading third-generation intelligent rotary geological guidance system, as it does not yet possess cutting-edge core technologies such as high-precision geological parameter integrated measurement, drill bit forward exploration, high-speed remote transmission, and intelligent decision-making.

2.2.3 Supporting technologies for drilling speed increase

There is a gap between the wear resistance, impact resistance, and directional control ability of drill bits and foreign countries. The single pass footage and service life of horizontal sections need to be further improved, which cannot fully meet the drilling requirements of "one pass drilling" in ultra long horizontal sections.There is a gap in processing technology and rubber technology between high torque and long-life screw drilling tools, with low output torque and short service life. In recent years, major shale oil fields in China have upgraded their ground equipment by adopting the "three highs and two big" drilling parameters of "high drilling pressure, high rotation speed, high pump pressure, large displacement, and large torque". The acceleration effect is significant, but the application proportion is small and the persistence is not enough.Compared with foreign drilling parameters, the overall drilling pressure, rotation speed, and displacement are relatively low, which restricts the improvement of mechanical drilling speed, especially in the horizontal section where there is a significant difference in mechanical drilling speed.In terms of intelligent drilling and completion technology, a remote support center for drilling and completion has been established, and professional software for drilling design and collaborative acceleration has been developed, forming a scientific drilling model of "professional software modeling+expert remote support". However, intelligent drilling and completion technology is still in the early stage of single technology development, and there is still a certain gap in the intelligence level of equipment and tools compared to foreign countries.The benchmarking situation is shown in Table 4.