On November 2, Changqing Oilfield successfully completed its first field geophysical experimental well following the completion of the final logging operation. The well is also one of three field geophysical experimental wells planned by CNPC for 2026. Its completion marks phased progress in logging evaluation technology for complex reservoirs in the Ordos Basin and provides essential data for more detailed multi-layer reservoir evaluation and future exploration planning.

The Ordos Basin contains multiple types of complex reservoirs, including coal-bearing formations, shale, and carbonate rocks. Logging responses vary significantly across these formations. Engineering challenges include wellbore instability in coal seams and borehole diameter reduction in gypsum-salt formations. In addition, extensive fractures can compromise logging data quality. For years, systematic field data have been insufficient to establish reliable correlations among the four key reservoir properties: lithology, physical properties, oil-bearing characteristics, and electrical properties. As a result, the applicability of logging interpretation models across different formations has been difficult to validate consistently.

The primary objective of this experimental well was to provide field support for comparative logging measurements, reservoir modeling, and evaluation technology development across multiple formations. It is particularly important for calibrating and evaluating the four key reservoir properties of coal-bearing, shale, and carbonate reservoirs in the Ordos Basin.

Rather than contributing directly to production, the well was designed to establish a reusable field calibration benchmark. Through systematic core acquisition and comparative testing using multiple logging methods, the project aimed to identify the response characteristics and application limits of different logging technologies in various reservoir types.

Since the beginning of the year, Changqing Oilfield has followed an integrated development approach centered on reserves, mining rights, and full-chain management, under the guidance of major CNPC research initiatives. It has strengthened top-level planning and established a cross-organizational operating mechanism integrating research projects, exploration teams, and field support. Research and field personnel worked closely through a dedicated project team, focusing on the development of an integrated core-and-logging calibration well for coal-bearing and carbonate formations. Technical, management, and operational resources were coordinated to clarify reservoir distribution patterns, optimize engineering measures, and accelerate the development of specialized technologies and operating models.

During drilling operations, the team addressed challenges including coal seam collapse, borehole shrinkage in gypsum-salt formations, and fracture-related lost circulation. By maintaining strict safety standards and controlling operational quality and progress, the team successfully completed more than 1,000 meters of continuous coring, ensuring the accuracy and reliability of the collected data.

Meanwhile, 39 logging technology experiments were conducted under different salinity conditions using saltwater- and freshwater-based drilling fluid systems. The tests covered instrument parameter comparisons, rock-electrical calibration, regional standard development, and validation of new technologies and instruments. The results provide systematic experimental evidence to support research and exploration activities in the Ordos Basin.

From the completion of the final logging run to the implementation of 39 experiments, and from core acquisition to the establishment of a calibration well, the project has produced more than drilling footage: it has established a potential technical benchmark for Changqing's complex reservoir evaluation.

The project team has identified its next research priorities, including further investigation of logging response mechanisms in complex reservoirs, improvement of multi-layer logging acquisition programs and interpretation standards, and the application of experimental results to regional exploration activities.

The value of this field geophysical experimental well lies in bridging the gap between laboratory models and actual downhole conditions. Logging evaluation of coal-bearing, shale, and carbonate reservoirs in the Ordos Basin faces distinct technical challenges. Coal seams are prone to collapse, resulting in poor borehole conditions and difficulties in maintaining close contact between logging instruments and the borehole wall. In shale formations, the combined effects of organic matter and clay minerals on electrical responses create considerable uncertainty in hydrocarbon evaluation. Carbonate reservoirs, characterized by highly heterogeneous fracture- and vug-dominated structures, are difficult to characterize accurately using conventional logging methods.

By completing more than 1,000 meters of continuous coring and 39 logging experiments under different fluid salinity conditions in a single well, the project has established a unified field calibration reference for these three reservoir types, providing a more reliable basis for logging interpretation in subsequent regional wells.

From an operational perspective, the integrated mechanism combining research projects, exploration teams, and field support has brought research design, field operations, and data evaluation into a coordinated workflow. This reduces information loss between research and execution teams and was instrumental in completing the well from deployment to final testing within the year.

In the longer term, the Changqing calibration benchmark offers a replicable approach. Given the Ordos Basin's vertically stacked formations and diverse reservoir types, standardized calibration well construction methods and optimized logging programs could significantly improve reservoir evaluation efficiency in future exploration blocks, providing direct support for exploration in deeper formations and new stratigraphic intervals.