Method for judging wettability of reservoir rock

Abstract

The invention provides a method for judging the wettability of a reservoir rock. The method comprises the following steps of: measuring free relaxation time of oil and water respectively; measuring transverse relaxation time of the oil and the water in saturated states respectively; measuring a nuclear magnetic resonance signal of the reservoir rock in the co-presence of an oil phase and a water phase by using nuclear magnetic resonance technology and recording an oil saturation value and a water saturation value in the co-presence of the oil phase and the water phase; dipping the rock core of the reservoir rock in the co-presence of the oil phase and the water phase in more than or equal to 20,000 ppm paramagnetic solution, waiting for at least 48 hours and separating the nuclear magnetic resonance signal of the reservoir rock in the co-presence of the oil phase and the water phase to obtain the transverse relaxation time of the oil and the water reflecting the size of an oil wet area and a water wet area; and calculating a wettability index in the co-presence of the oil phase and the water phase according to the free relaxation time of the oil and the water, the transverse relaxation time of the oil and the water in the saturated states, the transverse relaxation time of the oil and the water, the oil saturation value and the water saturation value so as to judge the wettability of the reservoir rock.

Description

technical field [0001] The invention relates to petroleum exploration technology, in particular to a method for judging the wettability of reservoir rocks. Background technique [0002] Wettability is a property that exists on the surface of solids and liquids. When immiscible two-phase fluids (oil and water or water and gas) come into contact with the solid phase of rock, one of the fluid phases along the surface of the rock The phenomenon of spreading is wetting phenomenon, and the wettability of rocks is generally divided into three categories: oil wet, water wet and intermediate wet. Reservoir wettability controls the distribution of reservoir fluids and affects the conduction pathways of fluids. At the same saturation, the resistivity of an oil-wet reservoir will be higher than that of a water-wet reservoir. The wettability of reservoir rocks is mostly water-wet, which makes the Archie formula based on the water-wetness of reservoirs be able to identify oil layers and...

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Problems solved by technology

[0003] Previous studies on the wettability of reservoir rocks used methods such as contact angle measurement, Amott method (self-priming method) and USBM method (self-priming centrifugal displacement method). The operating procedures of these two methods are relatively complicated, especially The USBM method requires the use of an ultra-high-speed centrifuge designed for special cores, which is rarely used due to equipment constraints, so the above method is difficult to judge the wettability of reservoir rocks on well logging

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