6,800 meters deep! Conquering the “Mount Everest” of cementing for ultra-deep wells in the Hetao Basin.

At the start of the new year, China National Petroleum Bohai Drilling announced a major breakthrough in the Bayan market: The Guangming 5X ultra-deep exploratory well, drilled by the BHZ80002 drilling team, has successfully completed the cementing operation for its ultra-deep casing string at a depth of 6,799.87 meters. The cement slurry flowed smoothly back to the surface in one go, with zero errors or malfunctions throughout the entire process. This milestone marks another key technological breakthrough for China in the exploration and development of ultra-deep oil and gas resources in the Hetao Basin, paving the way for the efficient exploitation of this energy-rich "deep-earth" region.

At a well depth of 6,800 meters—equivalent to placing Mount Everest upside down underground—this location is not only a “no-go zone” for exploration and development but also a true “touchstone” for cementing technology. The geological environment faced by Well Guangming 5X can be described as extreme: the bottom-hole temperature soars above 170°C, resembling a scorching natural “furnace,” placing stringent demands on the high-temperature resistance of cementing materials. Even more challenging is that the deep strata are as fragile as “tofu dregs,” with an extremely narrow safe density window for drilling fluids. Any slight deviation in pressure control could trigger catastrophic risks such as well leakage or well collapse, leaving virtually zero room for error in the cementing operation.

“Cementing ultra-deep wells is the ‘lifeline’ of wellbore safety—every single step in the process allows for no room for even the slightest carelessness,” said the head of the Bohai Drilling Technology Team. To tackle this “Mount Everest"-level challenge underground, the company promptly established a joint task force composed of core personnel from various departments—including technology, engineering, and mud systems—and implemented an integrated “geology-engineering” collaborative mechanism. Through specialized seminars, the team meticulously broke down each technical difficulty, accurately assessed construction risks, and tailored a highly refined, end-to-end construction plan. Addressing the critical issue of cement slurry’s tendency to “flash set” under high-temperature conditions, the team conducted dozens of rounds of laboratory experiments and displacement volume simulations, ultimately selecting a specialized cement slurry formulation with exceptional temperature resistance and outstanding rheological properties, thereby establishing a robust quality safeguard at the very source of the well.

Before starting the作业, the construction team conducted a comprehensive “deep clean” of the wellbore in advance, fully activating solids-control equipment to remove harmful solid phases and meticulously adjusting the mud properties. While reducing the viscosity and yield stress of the drilling fluid, the team ensured the stability of the wellbore walls. To enhance the pressure-bearing capacity of fragile formations, the team innovatively adopted a combined process that includes thick-slurry encapsulation cleaning and staged pressure application via plug injection. Additionally, micro- and nano-sized sealing materials were added to successfully seal microfractures in the wellbore, fundamentally eliminating the risk of well leakage during cement slurry return caused by the “hydraulic wedging” effect.

During the cementing operation phase, the on-site team transformed into “precision underground operators,” meticulously adhering to the construction plan and carefully controlling every single detail. Relying on real-time monitoring data, the team innovatively adopted variable-displacement displacement technology, dynamically adjusting the displacement rate based on the rheological parameters of the cement slurry. This ensured that the equivalent circulating density (ECD) at the bottom of the well and the surface pressure remained essentially stable compared to those during drilling, effectively preventing pressure fluctuations from disturbing the fragile formation. Meanwhile, by intensifying inspections at key operational posts, increasing the frequency of density checks for the cement slurry entering the well, and assigning dedicated personnel to monitor the return flow in real time, the team established a comprehensive risk-warning system covering the entire process, ensuring that any abnormalities are detected and addressed promptly.

The successful completion of the cementing operation for the Guangming 5X ultra-deep well not only highlights Bohai Drilling’s core technological strengths in ultra-deep well cementing, but also provides a replicable and scalable technical model for the exploration and development of ultra-deep oil and gas resources in the Hetao Basin. As an important strategic reserve area for China’s energy supply, the Hetao Basin boasts enormous potential for ultra-deep oil and gas resources. This technological breakthrough will inject strong momentum into the region’s efforts to efficiently increase reserves and boost production, thereby solidifying the deep-earth technology foundation for safeguarding national energy security. (Source: Internet)