Stress sensitivity is the variation of rock petrophysical parameters resulting from changes in effective stress. In fractured reservoirs, experimental methods exhibit a certain amount of error in the quantitative analysis of reservoir rock stress sensitivity. In addition, fracture-bearing experimental rock samples are difficult to obtain and prepare. Therefore, in the present study, reservoir rock stress sensitivity in naturally fractured reservoirs was investigated based on geomechanical modeling using a case study of the Lower Cretaceous Xiagou Formation in the Qingxi Oilfield. The results indicate that the Xiagou fractured reservoir experiences strong stress sensitivity with a fracture permeability damage rate reaching 94.38%. Natural fractures influence reservoir rock stress sensitivity. The degree of filling and type of filled minerals within natural fractures have great effects on the permeability damage rate. A higher permeability damage rate suggests stronger rock stress sensitivity. Generally, I) for reservoir rocks with unfilled natural fractures, the permeability damage rate is extremely high; II) for reservoir rocks with partially filled natural fractures, the permeability damage rate is high, and if the minerals within the natural fractures are insoluble, the permeability damage rate is slightly higher than if the materials are soluble; III) for reservoir rocks with completely filled natural fractures, the permeability damage rate is extremely low if the minerals within the natural fractures are insoluble; however, if the materials are soluble, the permeability becomes slightly higher with the increase of effective stress. Most importantly, this study provides a practical method for analyzing stress sensitivity in naturally fractured reservoirs.

中文翻译：

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天然裂缝性储层的应力敏感性-以西北九溪盆地青溪油田下白垩统下沟组为例

应力敏感性是有效应力变化引起的岩石岩石物理参数的变化。在裂缝性储层中，实验方法在定量分析储层岩石应力敏感性方面表现出一定程度的误差。此外，含裂缝的实验岩石样品很难获得和制备。因此，本研究以青溪油田下白垩统下沟组为例，基于地质力学模型，对天然裂缝性储层的岩石应力敏感性进行了研究。结果表明，下沟裂缝性储层应力敏感性强，裂缝渗透率破坏率达94.38％。天然裂缝影响储层岩石应力敏感性。天然裂缝内的填充程度和填充矿物的类型对渗透率破坏率有很大影响。较高的渗透率破坏率表明较强的岩石应力敏感性。通常，I）对于天然裂缝未填充的储集岩，渗透率破坏率极高。II）对于天然裂缝部分充满的储集岩，渗透率破坏率高，如果天然裂缝内的矿物不溶，渗透率破坏率比材料可溶时略高。III）对于天然裂缝完全充满的储集岩，如果天然裂缝内的矿物不溶，渗透率破坏率极低；但是，如果材料可溶，渗透率随有效应力的增加而略有增加。最重要的是，这项研究为分析天然裂缝储层的应力敏感性提供了一种实用的方法。