Finding oil in the "underground Mount Everest"! How did the Tarim Oilfield successfully develop an ultra-deep oil and gas field at a depth of 8,000 meters?

On October 24, 2024, Liu Jun, deputy manager and associate researcher of the Science and Technology Management Department of the Northwest Oilfield Branch of China Petroleum & Chemical Corporation, delivered a speech entitled "The Power of Petroleum Technology in the Deep Desert" at the Science Popularization China Starry Sky Forum with the theme of "Inheriting the Spirit of Scientists and Let the Desert Bloom with the Light of Life".

In recent years, during the continuous exploration and development process in the Tarim Basin, we have discovered two important types of oil and gas reservoirs: one is the fracture-cave oil and gas reservoir controlled by large-scale karst karstification, and the other is the fracture-cave oil and gas reservoir controlled by large-scale strike-slip faults. These discoveries provide rich reserves for the exploitation of oil and gas resources.

At present, the deepest oil and gas resources that can be developed in the Tarim Basin are hidden at a depth of about 7,000 to 9,000 meters underground. These oil and gas resources are distributed in a series of long and varying sizes of fault zones, like apple trees. The difficulty of exploring and developing such oil and gas reservoirs is like standing on sea level to pick apples located at the height of Mount Everest underground. It is a world-class problem.

In order to extract oil from a depth of 8,000 meters underground, people have long faced the problem of "not being able to see clearly, not being able to determine accurately, not being able to hit, and not being able to extract well". Our scientific and technological innovation team has formed a series of supporting exploration and development engineering technology sequences through independent research and development and joint efforts of industry, academia and research. Many of these technologies are at the leading level in China and even in the world, creating a technological miracle in the depths of the desert.

Below I list two key technologies.

The first is the ultra-deep seismic exploration technology in the desert area, which is to "take a CT scan" of the earth in the heart of the desert and draw an underground treasure map of Mount Everest oil and gas. First, a large collection network is designed in the heart of the desert, and signal excitation and receiving devices are arranged at different points. Then, the excitation signal is transmitted to the deep layer, and the signal carrying the underground stratum, structure, fault and cave information is received back; finally, through the analysis, processing and interpretation of the seismic wave signal, the mysterious underground treasure map is restored.

In this process, ultra-deep reservoir stereo imaging technology and fracture-cavity fine carving technology were developed, which increased the fault identification accuracy of 8,000 meters underground from 30 meters to 15 meters. At the same time, these technologies can also perform 360-degree scanning of underground strata, allowing oil and gas reservoirs at a depth of more than 8,000 meters to be "clearly seen, accurately described, and accurately determined", realizing the transformation from "feeling and striking" to "looking and striking".

The second is ultra-deep, high-quality and fast drilling technology. It is like a key to the deep earth, building an oil and gas highway. It has three innovations. The first is to "adjust the route" for drilling. There are many obstacles such as volcanic rocks, cracks, and high-pressure water layers on the treasure hunting road of more than 8,000 meters. If you are not careful, all your efforts will be wasted. Through the integration of geological engineering and multidisciplinary joint operations, the dynamic correction technology of seismic profiles has been developed, which can predict the spatial position of obstacles on the drilling path, adjust the drilling route in advance, and minimize drilling risks and maximize benefits.

The second is to "change weapons" for the drill rod. Faced with the difficult problems of high hardness and strength of ultra-deep rocks and low rock breaking efficiency, we have developed a hybrid drill bit that combines the advantages of roller drill bits and diamond drill bits, as well as the country's first set of high-precision downhole measurement instruments that can withstand temperatures of 200 degrees Celsius and pressures of more than 200 MPa, to achieve the goal of efficient rock breaking and rapid drilling.

Third, the drill bit is equipped with eyes. In order to accurately find oil and gas in the "deep and dark" underground, the research team uses ultra-deep high-temperature and high-efficiency directional technology, and uses a high-precision drilling control system to transmit signals from deep underground to the surface in real time, so that the drill bit can adjust its trajectory at any time. These drilling technology and equipment innovations have achieved a leapfrog breakthrough in halving the drilling cycle.

After drilling the well, it is time to extract the oil. Just like drinking milk with a straw, an oil pipe must be placed in the wellbore to connect the ground and the oil and gas reservoir. In the early stage, the energy of the oil and gas reservoir is sufficient, and it is mainly self-flowing; in the middle and late stages, the energy of the oil and gas reservoir becomes weaker, and a special pumping unit is needed to assist in extraction. The old-fashioned pumping unit is also called a "kowtow machine". Its shape is a bit like the "water pressure well" used in rural areas in the early years. It can pump water up from underground with a strong pressure. The same principle applies to the pumping unit, but the suction force is stronger and can suck oil up from thousands of meters underground.

The yellow-green oil in the picture below is condensate oil. The condensate oil in Shunbei Oil and Gas Field is mainly in gaseous state at 160 degrees Celsius more than 8,000 meters underground, which is called condensate gas reservoir. It will change a lot like Sun Wukong, which is very magical. The first change is the phase change. The temperature continues to drop from underground to the surface, and part of the condensate gas gradually condenses into liquid; the second change is the color change. This bottle of condensate oil is fluorescent green when it is just produced. After being stored for a certain period of time, the trace elements gradually become light yellow after oxidation, forming a change from Mei Nian to orange juice; the third change is the value change, with very few impurities, which is the highest quality refining material and can also produce many chemical materials with high economic value.

The 70-year development history of China's petroleum and petrochemical industry is nearly a hundred years behind the history of the world's petroleum industry, but it has created many miracles that have attracted worldwide attention. Look up to the highest point of the starry sky and take root in the deepest part of the desert. Through the struggles of generation after generation and the perseverance of one group after another, the desert oil workers have formed a series of unique cultures such as "there is only a desolate desert, but not a desolate life", "the desert is barren but the ambition is not barren, the wind and sand are greater but the determination is even greater", "dare to be the first and keep innovating", etc., which support them to stand firm like poplars and contribute their light and heat to the development of the western region and energy construction of the country.