The team of the Institute of Acoustics of the Chinese Academy of Sciences continues to explore and develop transverse wave remote detection imaging logging technology

The team of the Institute of Acoustics of the Chinese Academy of Sciences continues to explore and develop transverse wave remote detection imaging logging technology

"Make B ultrasound" for the earth, use sound waves to find oil and gas

Reporter Wu Yuehui

From 2011 to 2021, China spent 10 years to implement the strategic action of prospecting breakthrough. During this period, a total of 17 billion-ton oilfields and 21 32 billion cubic meter atmospheric fields were discovered, <> new non-oil and gas mineral resource bases were formed, and the main mineral reserves generally increased.

Oil energy construction is of great significance to our country, China, as a manufacturing country, to develop the real economy, energy must be in its own hands. To secure the rice bowl of energy, we must play the role of the primary driving force of scientific and technological innovation, and solve major problems and challenges such as energy resource constraints, ecological environmental protection, and climate change through technological progress.

In recent years, the solid state acoustics and deep drilling team of the Ultrasound Laboratory of the Institute of Acoustics, Chinese Academy of Sciences, has been unremitting in exploring the core technology of using downhole sound waves to detect energy for decades, and has developed downhole acoustic detection instruments with better performance, which is of great significance to support China's deep exploration and ensure national energy security.

—Editor

What are the steps to find an oil and gas field?

"Looking, hearing and cutting" to determine the position, and the logging instrument as the "eye"

Oil and gas exploration is a complex and difficult task with great risks. So, what are the steps to find an oil and gas field?

Chen Dehua, a researcher at the Institute of Acoustics of the Chinese Academy of Sciences and director of the Ultrasound Laboratory, said: "The process of finding oil and gas fields can be summarized by the four words 'looking, hearing and asking' in traditional medicine. ”

First, geologists conduct an area overview to determine the areas and extent where oil and gas fields may be present. This step is equivalent to "looking" and "smelling" in "looking, hearing and asking"; Then conduct a regional census and use artificial seismic methods to infer the structure of underground rocks, which is equivalent to "asking", which can roughly determine which locations underground oil and gas reservoirs exist; Next, engineers drill the first well of a potential oil and gas field, a probe well, for an area stiny, which is equivalent to "cutting".

Chen Dehua said: "If you want to understand the specific location of the oil and gas layer and the value of oil and gas exploitation, the above 'look and smell' is not enough, but also need to combine some high-tech means, such as logging technology." ”

Well logging is called the "eye of the oil industry", because in the dark and hot underground, the formation rock information cannot be directly observed, and the data must be recorded and transmitted to the ground by the logging instrument, which is like the human eye receiving a light signal and processing it into an image for identification.

"By putting advanced logging instruments into the borehole, we can make fine detection of oil and gas layers thousands of meters underground with centimeter or higher accuracy. Through logging, the nature of the formation can be determined, and further accurate evaluation of the formation can be made to determine whether the formation contains oil and gas, how much oil and gas content, the thickness of the oil layer and the assessment of oil and gas recovery. "This process is like people 'doing ultrasound' during a physical examination in a hospital." ”

Well logging methods are usually divided into four types: acoustic method, electrical method, nuclear physics method and nuclear magnetic resonance method. Among them, the method of transmitting sound waves to the formation and receiving and processing the reflected or refracted sound waves to obtain formation information is called acoustic logging. "Compared with several other methods, acoustic logging is not only environmentally friendly, relatively low-cost, but more importantly, it can obtain many critical formation rock mechanical parameters." Chen Dehua said.

How is domestic high-end acoustic logging equipment developed?

"Start from scratch" to solve problems, trial and error and finally mass production

At the beginning of this century, the competition in the exploration and development of oil and gas resources around the world continued to escalate. "At that time, we lacked a self-developed dipole acoustic logging transducer, and it was difficult to promote the application of advanced technology of dipole shear wave logging on a large scale. This not only affects the localization of China's high-end acoustic logging equipment, but also seriously hinders and restricts the progress of China's oil and gas exploration and exploitation. Chen Dehua recalled.

Faced with thorny problems, the research team of the Institute of Acoustics of the Chinese Academy of Sciences rose to the challenge.

The research can be said to be "starting from scratch", and the team members can see the "look" of the transducer embedded in the instrument on the market and understand some basic functions that it can achieve, and the rest of the specific information such as materials, structure, parameters and so on is almost unknown.

After nearly 3 years of repeated exploration, experimentation, and hundreds of failures, the team finally developed the first samples of the transducer. Chen said: "However, once this batch of transducer samples were put into a high-temperature environment for testing, either cracked as a whole or the piezoelectric ceramics were broken, resulting in test failures again and again. ”

What went wrong? In the past 4 months, the team members have repeatedly studied material selection, changed more than a dozen batches of materials, and continuously improved the bonding process, and finally overcome the production problems of high-temperature and high-pressure acoustic logging transducers after hundreds of repeated tests, and developed finished products that have reached the international advanced level.

After the delivery of the domestic transducer, it was immediately put into practical application and carried out small-scale mass production.

How to overcome the "one-hole view" of logging technology?

Optimized design to "probe far" and stimulate sound sources to "hear clearly"

The detection range of conventional acoustic logging is often limited to a few centimeters to tens of centimeters around the well. It's like when two people are talking, the farther apart the two sides are, the harder it is to hear each other; And if you hide in a confined space to speak, the sound of outsiders will be smaller.

Because logging is carried out in very narrow boreholes, conventional logging techniques have a very limited detection range, so logging techniques are often described as "one-hole view".

How to "probe far" and "hear clearly"?

"For acoustic logging, this requires continuous optimization of the design of the excitation sound source, so that the sound wave not only travels farther, but also 'wears a scope', with the directionality of 'pointing and fighting'." Chen Dehua introduced.

Several generations of scientific and technological workers in the field of ultrasound in China have been exploring since the 80s of last century. After unremitting efforts, in recent years, the Ultrasound Laboratory of the Chinese Academy of Sciences has continuously developed low-frequency shear wave remote detection technology, and expanded the detection range of acoustic logging to tens of meters or even hundreds of meters around the well.

"The frequency range of sound sources for dipole shear wave remote detection is much lower than that of ordinary acoustic logging. Low-frequency sound waves have less attenuation, so longer lateral detection distances can be achieved. Chen Dehua said, "At the same time, the signal of the dipole sound source has azimuth difference, using multi-component sound wave transmission and reception, through signal processing can determine the direction of the sound wave reflector, which makes the sound wave have directionality." ”

In 2012, the Laboratory of Ultrasound of the Chinese Academy of Sciences successfully developed a dipole array acoustic logging instrument; In 2013, we began to develop the key core technology of transverse wave remote detection; At the end of 2021, the third-generation transverse wave remote detection imaging logging instrument achieved clear out-of-hole geological imaging and a detection record of 8340 meters depth in ultra-deep wells, setting a record for the depth detection of such domestic instruments, which is of great significance to ensuring national energy security. (People's Daily)