Abstract:

In order to investigate the characteristics and degree of reservoir sensitivity of the lower Triassic Jiucaiyuanzi formation in the Fudong slope of Junggar basin, the fracturing technology and injection-production development measures have been timely updated. The sensitivity of the conglomerate reservoirs in the Jiucaiyuanzi formation and its controlling factors on the sensitivity were systematically evaluated based on the analysis of reservoir lithology, reservoir space, pore structure and physical properties, and the data of SEM and whole-rock X-ray diffraction in the study area. The studies show that acid sensitivity of the reservoir is the strongest, followed by medium-strong salinity sensitivity, and the last are water sensitivity and velocity sensitivity, generally medium to weak. The location and occurrence of clay minerals are key factors that determine the reservoir sensitivity. Filamentous and flocculent illite/smectite formation among grains is the primary cause for water sensitivity. Meanwhile, water sensitivity and velocity sensitivity are also affected by filamentous illite. The salinity sensitivity is mainly caused by worm-like kaolinite. Furthermore, interstitial fillings rich in zeolite, calcite cements and comb-shaped and leaf-shaped chlorite are the main reasons resulting in the strong acid sensitivity in the study area. The integrated sensitivity evaluation method of dynamic flow and static immersion established through static immersion comparative experiments is introduced, which can eliminate the difficulty in obtaining sensitivity evaluating parameters due to loose cementation, strong expansion and dense lithology. This method can reflect the sensitivity mechanism of the reservoir more intuitively, and provides a new way for sensitivity evaluation of similar reservoirs.

Key words: Junggar basin, Fudong slope, Jiucaiyuanzi formation, reservoir characteristic, sensitivity, microscopic characteristic, clay mineral, fluidity test, static immersion experiment