As of November 28, Changqing Oilfield has drilled 1,720 large-inclination wells in the Longdong area of Gansu, with an average daily oil output of 3.2 tonnes per well and an annual oil production exceeding 800,000 tonnes. This marks the establishment of PetroChina’s first million-ton-level development zone based on large-inclination wells, providing a replicable and scalable technological model for efficient development of multi-thin-layer tight oil reservoirs in China.

Huacheng and Xifeng oilfields—key areas for reserve growth and production enhancement—began large-scale development in the early 2000s. However, as development progressed, targets shifted from high-quality main sand bodies to tighter, more complex marginal reservoirs.

These tight reservoirs held abundant resources but were difficult to efficiently tap. “In the early days we mainly used conventional directional wells, but single-well output was low and economic returns were poor. When we attempted horizontal wells, the multiple thin layers made vertical reservoir utilization very low—like using a cannon to shoot mosquitoes,” said Liu Jian of the Exploration & Development Research Institute.

A turning point came in 2019. Changqing’s technical team shifted strategy and pushed forward, determined to break through the development bottleneck. By intensifying the use of 3D seismic and integrating geology, geophysics, and logging, they developed a precise sweet-spot evaluation system. “It’s like performing CT scans and pathology analysis on the subsurface,” Liu noted. Through this multidisciplinary approach, the team identified previously overlooked favorable development zones in Huacheng and Xifeng.

With clear targets established, the team advanced further. After extensive study and field validation, they developed and standardized an effective development model: “large-inclination wells + five-spot well pattern + early water injection.” Large-inclination wells, characterized by steep deviation and long reservoir contact, are well suited to Longdong’s multi-thin-layer reservoirs, achieving both precise penetration and broad drainage.

Refined geological characterization was essential for accelerating application. Changqing Oilfield intensively examined vertical variations in physical properties and oil content across multiple layers, and accurately mapped the thickness and distribution of interlayers. Based on these insights—combined with overall reservoir properties, vertical heterogeneity, and stress differences between reservoir and barriers—the field achieved simultaneous, efficient development of multiple key layers.

At the same time, efforts to innovate fracturing technologies were strengthened. Reservoir-engineering integrated “dual sweet-spot” evaluation was deepened, and a multilayer, multistage fracturing model tailored for large-inclination wells was established, featuring hydraulic jetting, fine-scale multistage fracturing, and interference fracturing. With the goal of “vertical multilevel stimulation and interwell fracture networking,” this approach maximizes and three-dimensionally enhances reservoir stimulation. Vertical recovery efficiency—which had long been difficult to improve—has now risen to above 80%, laying a solid technical foundation for efficient tight-oil development.