Abstract: Due to good vertical interconnection in the ultra-deep fault-karst reservoirs, oil and gas under the well bottom can easily flow to the well bottom along the fractured channel with high conductivity in oil well production. In order to identify the production depth of oil wells, Well W9 well in Z Oilfield was taken as an example to compare and analyze the characteristics of flow temperature and static temperature of ultra-deep fault-karst reservoirss, and establish the calculation method of oil well production depth with different temperature-depth relationships based on temperature characteristics. It was found in the study that the flow temperature at the same depth was greater than the static temperature, which had nothing to do with the nozzle diameter; when the depth was constant, the larger the nozzle diameter, the higher the flow temperature; as the depth increased, the difference between the flow temperature and the static temperature generally decreased, and the flow temperature gradient was low near the well bottom; the temperature characteristics of the ultra-deep fault-karst reservoirs were affected by heat loss, oil well production depth and heat transfer mode; the production depth of Well W9 was about 52 to 62 m under the current production conditions with Ф4.5 mm nozzle. This study can provide a basis for the judgment of oil column height, reserve calculation and formulation of reasonable production systems for ultra-deep fault-karst reservoirs.

Key words: ultra-deep oil reservoir, fault-karst reservoirs, production depth, flow temperature, static temperature, oil column height