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Spontaneous imbibition plays a critical role in two-phase flow within hydraulic fractures of tight reservoirs. Despite significant efforts to address this phenomenon, there are few studies that concentrate on tight glutenite reservoirs, an essential subset of tight reservoirs. As a result, the imbibition mechanism and its influencing factors remain unclear, with several key factors not being captured, and in-depth analyses missing in spontaneous imbibition for tight glutenite reservoirs. Given the existing knowledge gaps, this study performed a series of water imbibition experiments in conjunction with X-ray diffraction, thin section analysis, scanning electron microscope observations, and high-pressure mercury injection tests on tight glutenite cores exhibiting various petrophysical properties. The influences of mineral composition and content, concentration of particles with different sizes, pore type and structure on spontaneous imbibition were revealed. The main and secondary influencing factors were identified through grey relation analysis. The experimental results indicate that distinct microscopic characteristics of tight glutenites lead to significant variations in spontaneous imbibition patterns. Consequently, the experimental cores were categorized into two groups. For Group I, intergranular pores filled with water-wet quartz grains and illite, as well as gravel-edge fractures connected with pores, can significantly enhance imbibition recovery. Intragranular dissolved pores and medium-size sand are negative influencing factors. However, in Group II, intergranular pores and gravel-edge fractures are filled with oil-wet chlorites and matrix, respectively, which hinders water imbibition. The interconnected intragranular dissolved pores are the primary spaces for water imbibition. Micro and macropores can enhance water imbibition and oil drainage ability, respectively. Thus, their coordination facilitates spontaneous imbibition. Macropores and gravels are the primary influencing factors for Group I, whereas for Group II, the main influencing factors include medium-sized sand, intragranular dissolved pores, fractal dimensions, micropores, and intergranular pores. These observations enhance our comprehension of the unique imbibition mechanisms present in tight glutenite reservoirs.
| Country | China |
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