Abstract: Deploying horizontal wells across sealing faults is a development method that can effectively increase the producing reserves of single wells in complex fault-block oil fields and reduce the investment in drilling and completion. Compared with conventional horizontal wells, the productivity prediction and segment length optimization for cross-fault horizontal wells need to consider the influence of multiple factors such as differences in reservoir permeability and thickness in each fault block, sealing fault boundary and wellbore friction. To comprehensively consider the above factors, based on the principles of potential superposition and mirror image, this paper establishes a calculation model for two modes of radial flow distribution along the wellbore of horizontal wells across sealing faults, and obtains a productivity prediction method applicable for horizontal wells crossing sealing faults in complex fault block oilfields. On this basis, this study provides a reservoir engineering method for quickly optimizing the segment length of horizontal well across sealing faults in each fault block; the reliability and effectiveness of the model and method are verified by a case study of the complex deep-water fault-block oil field in West Africa. The research results show that under the condition that the physical properties of fault blocks and the length of horizontal wells are the same in each fault block, the radial flow distribution in horizontal wells across one sealing fault is generally approximately U-shaped, while for horizontal wells across two sealing faults, due to the influence of sealing fault boundary, the radial flow rate of the horizontal well section in the central fault block is significantly lower than that of the other two fault blocks on the right and left sides, and linear flow plays the main role in the central fault block. For complex fault block oil fields, the distance between the horizontal well and the fault boundary significantly affects its productivity. When the length of the horizontal well across faults is the same, the closer the heel and toe of horizontal well is to the fault boundary, the lower the productivity of the horizontal well is. However, it is difficult for the conventional productivity prediction methods of horizontal wells to consider the influence of sealing fault boundary, so the prediction results are a bit high.

Key words: horizontal wells across sealing faults, productivity prediction, segment length optimization, sealing fault boundary, radial flow distribution

摘要： 布署跨封堵断层水平井是一种有效提高复杂断块油田单井动用储量、减少钻完井投资的开发手段。与常规水平井相比，跨断层水平井的产能预测和分段长度优化需考虑各断块内储层渗透率及厚度差异、封闭断层边界和井筒摩阻等多因素的影响。为综合考虑上述因素，基于势的叠加原理和镜像原理，建立了2种模式下的跨封堵断层水平井沿井筒径向流量分布计算模型，得到了适用于复杂断块油田的跨断层水平井产能预测方法，在此基础上形成了一种快速优化跨封堵断层水平井在各断块分段长度的油藏工程方法，并通过西非复杂断块深水油田的实例验证了模型和方法的可靠性及有效性。研究结果表明：在断块物性和各断块内水平井长度相同的条件下，跨1条封堵断层水平井径向流量分布整体上近似"U"形，而对于跨2条封堵断层水平井，由于两侧封闭断层边界的影响中部断块水平井段的径向流量显著低于两侧断块，以线性流为主要特征；对于复杂断块油田，水平井与断层边界的距离显著影响其产能，跨断层水平井长度相同时，水平井跟端和趾端距离断层边界越近，水平井产能越低，而常规水平井产能预测方法难以考虑封闭断层边界的影响导致其预测结果偏高。

关键词: 跨封堵断层水平井, 产能预测, 分段长度优化, 封闭断层边界, 径向流量分布