Analysis of Rock Electrical Parameters of Complex Carbonate Reservoirs in Akruor Structural Belt, Kazakhstan

The pore-throat characteristics of porous carbonate rocks are one of the primary factors controlling reservoir productivity. Building on previous research analyzing carbonate rock pore-throat features, this study examines the relationship between petrophysical parameters and pore-throat characteristics in the complex carbonate reservoirs of the Akruor structural belt, along with the logging response signatures of different pore-throat types. Key findings include: ① Strong cementation in the study area's carbonate rocks results in abundant isolated pores. In low-porosity formations, the rigid rock framework exhibits high brittleness, making it prone to microfractures under tectonic stress. These micro fractures interconnect the formation, straighten current pathways, and reduce the cementation index (m). However, limited microfracture-enhanced type and isolated pores lead to highly heterogeneous fluid distribution, increasing the saturation index (n). ② High-porosity formations with weak cementation feature loosely packed pore spaces. Stress is released through particle rearrangement or pore compression rather than brittle fracturing, manifesting as plastic deformation. This suppresses fracture development while coexisting dissolution pores and cement-filled pores complicate pore geometry, raising the cementation index (m). Enhanced connectivity of dissolution pores improves fluid distribution uniformity, lowering the saturation index (n). ③ Isolated pores exhibit complex logging responses, with a distinct signature being significantly reduced acoustic transit time porosity compared to other porosity measurements. In this region, acoustic porosity decreases to approximately 65% of total porosity. This characteristic provides direct insights into pore connectivity and reservoir productivity evaluation, demonstrating effective application in the study area.