Spontaneous imbibition (SI) plays a key role in production mechanism of unconventional reservoirs. Trivially, with the goal of getting higher efficiency there always has been an incessantly research activities to develop the technology progressively. In this regard, thermodynamic variables (i.e. pressure and temperature) can directly influence the process performance of SI. Thus, numerous papers have been published by considering normal conditions (e.g. 20°C, 0.1MPa), high pressure (HP) or high temperature (HT). To bridge an existing gap in the literature, an inhouse built imbibition experimental setup was used to carry out the SI under high pressure-high temperature (HPHT) conditions (50°C, 10MPa). The core samples used in this study were tight sandstone taken from Yanchang formation, Ordos Basin. Experimental conditions were: 1) simulated formation conditions (50°C, 10MPa), 2) normal condition (20°C, 0.1MPa), 3) pulse imbibition (20°C, 8/4MPa in cyclic alteration) and 4) simulated formation conditions (50°C, 10MPa) for fractured cores (1/3 and 2/3 length). Moreover, NMR was employed to characterize the dynamic behavior of imbibition for each sample. It was found, samples tested under HPHT conditions yielded higher imbibition efficiency (average of 63.49%) compared to ambient conditions (27.31%). and imbibition efficiency of HPHTSI (max, 73.47%, min, 55.23% ) showed early imbibition with higher rate. Ultimately, micropores had the largest imbibition efficiency and matrix core samples exhibited lower recovery than fractured ones (74.6%). Collectively, this study presents the importance of fracture-matrix interaction in tight sandstones which is a crucial component for higher recovery rates.

自发吸水在非常规油藏生产机理中起着关键作用。琐碎地，为了获得更高的效率，一直在不断进行研究活动以逐步开发该技术。在这方面，热力学变量（即压力和温度）可以直接影响SI的工艺性能。因此，考虑正常条件（例如20°C，0.1MPa），高压（HP）或高温（HT），已经发表了许多论文。为了弥合文献中现有的差距，使用内部内置的吸水实验装置在高压-高温（HPHT）条件（50°C，10MPa）下进行SI。本研究使用的岩心样品是取自鄂尔多斯盆地延长组的致密砂岩。实验条件为：1）模拟地层条件（50°C，10MPa），2）正常条件（20°C，0.1MPa），3）脉冲吸收（20°C，8 / 4MPa周期性变化）和4）模拟地层条件（50 °C，10MPa）断裂的岩心（长度为1/3和2/3）。此外，使用NMR表征每个样品的吸收动力学行为。结果发现，与环境条件（27.31％）相比，在高温高压条件下测试的样品具有更高的吸收效率（平均63.49％）。HPHTSI的吸水率（最大值，73.47％，最小值，55.23％）表现为早期吸水，吸水率较高。最终，微孔的吸收效率最高，基质岩心样品的回收率低于裂隙（74.6％）。总的来说，