页岩油不同类型甜点对水平井压裂产能影响规律

Effects of different types of sweet spots on fracturing and productivity of horizontal wells in shale oil reservoirs

非常规油藏开发已成全球能源开发的热点,但非常规储层尤其页岩储层物性差,经水力压裂后的水平井产能差异大,严重制约着页岩油的高效开发。本文系统分析了吉木萨尔页岩油不同类型甜点下的油井产能特征,并提出了基于甜点分布的页岩油压裂新思路。通过建立物性甜点及工程甜点模型,将储层品质划分为Ⅰ、Ⅱ、Ⅲ类。根据不同的甜点类型组合,结合油井生产动态,总结了3类水平井生产特征。通过压裂模拟及数值模拟优化,得到了3类压裂模式。结果表明:当水平井主要钻遇Ⅰ类物性甜点及Ⅰ类工程甜点时,则生产效果好(Ⅰ类井),且可采用较大的压裂规模,追求经济效益最大化(模式1);当水平井主要钻遇Ⅰ类物性甜点及Ⅱ/Ⅲ类工程甜点组合时,其生产效果较Ⅰ类井稍差(Ⅱ类井),压裂规模应适中,追求一定的产能和经济效益(模式2);当水平井主要钻遇Ⅱ/Ⅲ类物性甜点及Ⅰ/Ⅱ类工程甜点组合时,生产效果最差(Ⅲ类井),需采用小规模压裂,获得一定的产能,不追求经济效益(模式3)。该压裂思路对页岩油的开发具有一定的指导意义。

The development of unconventional reservoirs has become a hot issue in global energy field. However, due to the poor physical property of unconventional reservoirs, especially shale oil reservoirs, the productivity of hydraulically fractured horizontal wells varies greatly, which seriously restricts the efficient development of shale oil. In this paper, the productivity characteristics of fracturing wells under different types of sweet spots in Jimsar shale oil block is analyzed, and a new idea of shale oil fracturing based on the distribution of sweet spots is proposed. Firstly, the reservoir quality is classified into Ⅰ, Ⅱ, and Ⅲ types by establishing geological and engineering sweet spot models. Then, three kinds of horizontal well production characteristics are summarized according to the sweet spot types and oil production performance. Finally, three types of fracturing modes are determined through fracturing simulation and numerical reservoir simulation and optimization. Results show that if type Ⅰ geological sweet spots and type Ⅰ engineering sweet spots are drilled, horizontal wells will have a good performance in oil production which we call Type Ⅰ well. In this case, a large fracturing scale can be used to maximize economic benefits, which is referred to as Mode Ⅰ. If type Ⅰ geological sweet spots and type Ⅱ/Ⅲ engineering sweet spots are drilled, the production performance is slightly worse than that of Type Ⅰ well, which is called Type Ⅱ well. Correspondingly, the fracturing scale should be moderate to pursue certain oil production and economic benefits(Mode Ⅱ). If type Ⅱ/Ⅲ geological sweet spots and type Ⅰ/Ⅱ engineering sweet spots are drilled, the production performance is the worst(Type Ⅲ well). In this case, small fracturing scale is required to achieve a certain oil production without pursuing economic benefits(Mode Ⅲ). The fracturing idea has certain guiding significance for shale oil development.