砂页互层是中国陆相页岩油藏的一个显著地质特征。由于不同层内的孔渗和力学性质差异巨大,二维模型无法为页岩油藏开发提供准确的指导。本文针对中国陆相页岩油储层纵向多砂页互层特点,建立多压裂水平井三维流固耦合数学模型,并分别考虑地层非均质引起不同层内的应力敏感效应,通过数值模拟研究页岩油储层内单井和多井生产过程中的应力场演化规律。结果表明,当已钻井需要关井进行重复压裂时,重复压裂的位置应当选择水平井筒中部位置,重复压裂最优井段的长度也与生产时间有关,生产时间越长,最优复压井段越短;当以储层的总体开发效率为目标时,应当在不同小层内进行井位设计,如此可以在避免井间干扰的情况下减小井距,增大储层整体动用程度;在进行空间布井的时候也要考虑不同层内的井在水平面上具有一定井间距(大于300 m),且不同层内的井间距不同,如此才能使得页岩油藏达到较好的整体开发效果。本文建立模型可为页岩油立体布井、加密井及重复压裂提供技术支持。
Sand-shale interbedding is a significant geology feature of continental shale reservoirs in China. Due to the great difference of porosity, permeability and mechanical properties among different layers, the two-dimensional model cannot provide accurate guidance for shale reservoir development. According to the geology feature of continental shale reservoirs, a fully coupled mathematic model coupling solid deformation and fluid flow is proposed. The difference of stress sensitivity among different layers is also considered in this model. The stress evolution in a single well and multi-wells production process is investigated through numerical simulation. The simulation results show that: when refracturing is needed for the production well, the optimal refracturing locations are at the middle of the horizontal wellbore. The length of the optimal well section for refracturing should is related to the production time. With the longer production time, the length of optimal well section for refracturing is shorter. When taking the overall development efficiency of the reservoir as the goal, the well location should be designed in different layers, so that the well spacing can be reduced and the overall oil recovery of the reservoir can be increased without the interference between wells. To achieve better overall exploitation efficiency, when we design the well locations in different layers, there should be a specified horizontal distance among different wells, and the specified horizontal distance is different in different layers. The model established in this paper provides technical support for the design of three-dimensional well distribution, infill well and refracturing of shale oil reservoirs.
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