Abstract

Steering acid fracturing is a new way which can significantly increase oil and gas production. However, it is still unknown how to appropriately use steering acid in carbonate reservoir. Therefore, four true tri-axial acid fracturing experiments were carried out to study fracture initiation and propagation during steering acid fracturing. The experimental results reveal the following. 1. The results of the acid fracturing are easily affected by natural vugs, which can change the direction of the acid-etched fracture propagation. When there are few vugs in the reservoir, the steering acid etches the surface of the acid-etched fractures and forms crowds of acid-etched vugs. 2. When using high pumping rate, it is easy for the steering acid to plug the top of the acid-etched fracture and force the fracture to change its propagation direction. 3. The acid will etch the fracture surface, which results in a strong conductivity. The acid-etching phenomenon is obvious in the area near the wellbore and the turning area. The steering acid etches multiple channels with high conductivities rather than etching the entire area of the fracture surface. 4. Acid fatigue fracturing can effectively reduce the fracturing pressure. However, when using this method, there will be few acid-etched vugs in the area far from the wellbore.

Article Highlights

When acid is used as fracturing fluid, it would react with the carbonate, and form complex fracture networks.

中文翻译：

---

不同工程地质条件下转向酸性裂缝起裂扩展机理研究

摘要

转向酸压裂是一种可以显着提高油气产量的新方法。然而，如何在碳酸盐岩油藏中合理使用转向酸仍是未知数。为此，开展了四次真三轴酸压裂实验，研究转向酸压裂过程中裂缝的起裂和扩展。实验结果揭示了以下内容。1、酸蚀结果易受天然孔洞影响，可改变酸蚀裂缝扩展方向。当储层孔洞较少时，转向酸腐蚀酸蚀裂缝表面，形成成群的酸蚀孔洞。2、当使用高抽速时，转向酸容易堵塞酸蚀裂缝顶部，迫使裂缝改变其扩展方向。3. 酸会腐蚀断口表面，从而产生很强的导电性。井筒附近及拐弯区酸蚀现象明显。转向酸蚀刻多个具有高导电性的通道，而不是蚀刻整个断裂表面区域。4、酸性疲劳压裂可有效降低压裂压力。但是，使用这种方法时，远离井筒的区域几乎不会有酸蚀孔洞。

文章亮点

当酸用作压裂液时，会与碳酸盐反应，形成复杂的裂缝网络。