Experimental Study on Sensitivity of Complex Lithology Reservoirs

The Huhehu Depression in the Hailaer Oilfield is a low-permeability reservoir with complex lithology, and the reservoir sensitivity has a great influence on the reservoir performance. The sensitivity of the reservoir may cause permanent and irreversible damage of the formation in the course of different stages of production, like drilling, completion, well stimulation, downhole operation, water injection, and oil recovery. Therefore, the study on the reservoir sensitivity is important for prevention of damage and developing a reasonable performance program. In this study we investigated the characteristics and sensitivity of the reservoir based on the summarized results of the core and assay analysis, core CT scan observation, physical properties, X-ray diffraction, pore structure, and sensitivity measurements. The results showed that the formation type in the study area was dominated by illite/smectite minerals (30%), followed by illite (56.67%), kaolinite (14.5%), and chlorite (5.5%). The sensitivity flow experiments showed that the reservoir demonstrated a moderately strong alkali sensitivity and moderately weak water and salt sensitivity. The reservoir sensitivity is mainly determined by the type of clay minerals in the reservoir and the pore structure of the reservoir. Based on the study results, we suggest that in oil and gas exploration and development, the effort should be focused on prevention and control of alkali sensitivity, water sensitivity and salt sensitivity, and the targeted measures to protect the reservoir.