Abstract:

This paper presents the lithology, physical properties, and pore structure of the Huagang reservoir based on a large experimental dataset of thin-section, granularity, mercury injection and gas-water phase permeability. The study shows that lithology of the Huagang Formation is dominated by fine sandstone with diverse pore types and poor pore structure, which constitutes a (ultra-)low-permeability reservoir. Based on the reservoir features, we focus on the use of reservoir dynamic permeability and flow unit index to categorize the reservoir capacity. Seven types of reservoir parameters are selected, and the reservoirs are divided into four categories, including Class I and II (with natural production capacity), Class III (need to be fractured), and Class IV (ineffective reservoir). Practical application shows that the Huagang reservoir classification scheme proposed is consistent with the actual test results, and has good application potential.

Key words: Xihu Depression, Huagang Formation, dynamic permeability, flow zone, reservoir classification