Source: Science and Technology Daily

Ultra-High-Temperature and Ultra-High-Pressure Logging Equipment Sets Multiple World Records

  “Domestic ‘Wise Eye’” Peers into the Deep Earth at 10,000 Meters

  “Please listen: this audio was synthesized by matching the waveform of acoustic wave recordings from strata at depths of 9,000 to 14,000 meters to frequencies audible to the human ear. This marks the first time in China that the mysteries of the Earth dating back more than 500 million years have been unveiled,” a guide explained recently at the logging exhibition hall of China National Petroleum Corporation Logging Co., Ltd. (hereinafter referred to as “CNPC Logging”).

  In February of this year, China’s first ultra-deep exploration well exceeding 10,000 meters—Well Tako-1 in the Deep Earth Project—was successfully completed at a depth of 10,910 meters, setting multiple new world records. The CPLog ultra-high-temperature and ultra-high-pressure logging suite, independently developed by CNPC Logging, was successfully deployed in this well, thereby filling the gap in domestically produced high-end logging equipment for operations at depths over 10,000 meters.

  Exploring the “New Battlefield” Below 10,000 Meters

  As China’s oil and gas exploration continues to push deeper into the Earth’s interior, formations below 10,000 meters have emerged as a new frontier for safeguarding national energy security. However, the extreme conditions of ultra-deep formations make well-logging at depths exceeding 10,000 meters as challenging as lunar exploration. Until recently, well-logging equipment capable of operating reliably under such extreme conditions had long been monopolized by major international oilfield service companies, with critical core technologies tightly sealed off from transfer.

  CNPC Logging has launched an assault on this “bottleneck” challenge.

  In the critical field of high-temperature and corrosion-resistant sealing materials, a research team has integrated knowledge from materials science, structural mechanics, and other disciplines to successfully develop a new generation of sealing materials based on non-crystalline perfluorinated chemistry, ceramic molecular materials, and organic polymer materials. These materials exhibit temperature and pressure resistance as well as corrosion resistance that are at the international leading level. In the key manufacturing process of pressure-rated vacuum flasks, the team has innovatively developed an ultra-high-temperature titanium alloy welding process by starting with material selection and connection techniques, thereby significantly enhancing the reliability and service life of pressure-bearing components.

  Signal transmission distortion in 10,000-meter-class cables represents the “last-mile” bottleneck that limits the accuracy of deep-well logging. In response, a research team conducted an in-depth investigation into 12 core parameters—including cable reactance characteristics, transmission rate, and signal-to-noise ratio—and innovatively developed a high-frequency signal-loss correction technique based on an adaptive signal-compensation algorithm. Building on this, they independently achieved breakthroughs in key technologies such as clock synchronization and frequency-band shifting, and designed a highly efficient π-type filter circuit. These advances enable high-fidelity, lossless signal transmission over ultra-long 13,000-meter cables, thereby fully establishing the “lifeline” for data upload.

  After countless rounds of design, simulation, testing, and iteration, the prototype of ultra-high-temperature, ultra-high-pressure logging equipment has finally been completed. In the complex test environment of the pilot well, the prototype operates stably at 230°C, with pressure resistance exceeding 170 MPa, and can maintain continuous operation for more than 7 hours under extreme conditions.

   Software Algorithms Build the “Most Powerful Brain”

  “Breakthroughs in hardware lay the foundation. But to enable equipment to ‘see clearly’ and ‘identify accurately’ in the complex and ever-changing deep subsurface environment, it must be equipped with a powerful ‘brain,’” said Yao Genhu, a senior engineer at the Software Development Institute of CNPC Logging.

  To address the challenge of accurately identifying stratigraphic abrupt changes, the team simulated spectral data under various wellbore annulus conditions and innovatively integrated Kalman filtering with least-squares estimation for spectral inversion, thereby significantly enhancing the accuracy of data interpretation. In addition, by optimizing the acoustic slowness-time coherence algorithm, the team substantially improved its operational efficiency, stability, and computational accuracy under high-temperature and high-pressure conditions, ensuring real-time and precise detection of subtle acoustic travel-time variations in special formations such as soft formations and gas-bearing formations.

  To eliminate the distortion of logging curves caused by complex wellbore environments, the research team leveraged a backpropagation neural network algorithm to compress the massive dataset of array lateral environmental correction charts by more than a thousandfold, enabling real-time processing of instrument eccentricity correction. They also pioneered novel data inversion algorithms and adaptive deviated-well correction methods, significantly enhancing the instrument’s adaptability in challenging well conditions. Addressing the persistent challenge of blurred microresistivity imaging in high-salinity mud sections, they developed an acceleration correction technique combined with a downhole small-signal averaging and phase-sensitive detection algorithm, further improving image clarity.

  More than ten core algorithms have been optimized and innovated, embodying the collective wisdom of the R&D team and endowing this “national strategic instrument” with a powerful “intelligent brain.” As a result, it can continue to deliver high-precision, highly stable critical geological data even in extremely complex deep-well environments.

  From Pilot Wells to Large-Scale Deployment

  This equipment has not only delivered outstanding performance in national key ultra-deep well projects such as Well Tako-1 and Well Chuanke-1, but has also been rapidly deployed across the country. To date, it has successfully completed logging operations on 44 wells in multiple oil and gas fields, including those in Qinghai, Jilin, and North China.

  “This series of equipment has been successfully deployed in eight countries, including Niger and Chad, and in 2023 alone it supported nearly 300 commercial well operations, earning the trust of the international market,” said Li Qian, head of the Market Development Department at CNPC Logging International.

  To establish a comprehensive, integrated technical service capability for “well logging plus perforating” in ultra-deep wells, the research team proactively advanced, in parallel, the development of supporting technologies for post-casing perforation under ultra-high temperature and pressure conditions. This effort achieved “segmented, multi-stage, and progressive” acceleration of the jet, significantly enhancing penetration depth. By precisely optimizing the formulation of the explosive charges, a special high-temperature perforating charge was successfully developed. Target-test results are highly encouraging: the average casing hole diameter reached 6.62 mm, with an average penetration depth of 662.5 mm. This milestone marks the completion of the final piece in the “10,000-meter well-logging” technology system.

  Through extensive field applications across multiple locations, environments, and well types, the research team has continuously optimized the logging equipment. Leveraging physical modeling and numerical simulation, they have developed a suite of auxiliary tools for logging instruments and integrated high-precision instrument calibration systems and environmental simulation devices. At the same time, by fully capitalizing on the advantages of intelligent manufacturing lines, they have established a five-category industrialization standard documentation system covering ten types of instruments, thereby achieving initial batch trial production and deployment of six conventional logging instruments and two imaging logging instruments. This has propelled China’s ultra-deep well logging technology into a phase of rapid development.

  “The successful R&D and mass production of the CPLog ultra-high-temperature, ultra-high-pressure logging suite mark a historic leap for China in the field of extreme-environment logging—from trailing behind to taking a leading role in certain areas—thereby equipping deep-earth exploration at depths of over 10,000 meters with a reliable ‘domestically developed intelligent eye,’” said Zhang Bingjun, Chief Expert at CNPC Logging. “We will continue to focus on the nation’s deep-Earth strategic needs, aiming to develop even more advanced, reliable, and intelligent domestically produced logging equipment to provide robust support for the country’s energy exploration and development as it makes bold strides into ultra-deep formations.”