A rapid evaluation method for changing the wettability of core by nanofluid

Abstract

The present invention relates to a rapid evaluation method for rock core wettability change caused by a nanometer fluid, wherein the T2 relaxation times of water before and after treatment of rock core with a nanometer fluid are tested by using special rock core nuclear magnetic resonance equipment, and the T2 cutoff value and the change thereof are determined so as to rapidly determine the rock core wettability change. The concrete method comprises: saturating rock core with water, and testing a T2 relaxation spectrum; removing movable water from the rock core through a centrifugal method and a gas flooding method, testing the T2 relaxation spectrum of pore wall bound water, and respectively accumulating the two T2 relaxation times to obtain the T2 spectrum accumulation curve of the saturated water and the T2 spectrum accumulation curve of the bound water; making a straight line parallel to the horizontal axis by using the maximum value of the T2 spectrum accumulation curve of the bound water, and making the straight line and the T2 spectrum accumulation curve of the saturated water intersect to obtain a T2 cutoff value; and determining the rock core wettability change through the change of the T2 cutoff value. According to the present invention, the process is simple, the evaluation is rapid, the injection of crude oil during the detection process is not required, and the secondary use of the rock core is not affected.

Description

technical field [0001] The invention relates to a rapid evaluation method for changing the wettability of rock cores by nanofluids, which uses low-field nuclear magnetic resonance relaxation spectrum to study the wettability and changes of rock cores, and belongs to the technical fields of petroleum engineering enhanced oil recovery technology and spectroscopy. Background technique [0002] Core wettability is an important parameter for evaluating reservoir recovery and numerical simulation, and it is also an important factor that must be considered in the study of seepage mechanics from a microscopic perspective in recent years. At present, the conventional method for evaluating the wettability of cores recognized in the petroleum development field is the core wettability index method. Complete the wetness index test. Not only is the test method complex, highly specialized, and the test period is long, but also crude oil needs to be injected during the test process, which ...

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Problems solved by technology

Nanofluid can reduce the water flow resistance or improve the effect of water displacement by changing the wettability of the core. If the core index method is used, the test workload will increase significantly, and it is actually difficult to meet the requirements of the same core because of the need to inject crude oil. The requirements of wettability index before and after the test, usually use two similar cores for test comparison, which reduces the comparability of wettability index method results

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