Summary

The debonding of cementing interfaces caused by perforation will increase the possibility of microannuli/microcrack propagation during hydraulic fracturing. This phenomenon will pose a threat to well integrity not only with stimulation operations but also subsequent long-term production. The objective of this work is to quantitatively investigate the debonding degree of cementing interfaces after perforation. A numerical model was used to simulate the process of the wellbore being penetrated by the perforating gun. Then, a real dimensional perforation experiment was conducted with a circular target specimen. The numerical debonding area of the casing/cement interface was verified by this experiment with the method of computerized tomography (CT).

The numerical-simulation and experiment results show that the cementing-interface debonding is mainly caused by the displacement difference between the casing, cement sheath, and formation during perforation. The debonding area and the microannuli of the casing/cement interface are larger than those of the cement/formation interface. Sensitivity analysis reveals that the debonding area of the cementing interface shows a positive relationship with the hexogen explosive (RDX) load and the elastic modulus of casing. Therefore, the casing with lower elastic modulus should be preferred to reduce the debonding area of the cementing interface caused by perforation if the principal casing-design criteria were met.

概要

由射孔引起的胶结界面剥离将增加水力压裂过程中微环隙/微裂纹扩展的可能性。这种现象不仅会对增产作业造成威胁，而且还会对后续的长期生产造成威胁。这项工作的目的是定量研究射孔后胶结界面的剥离强度。使用数值模型来模拟射孔枪穿透井眼的过程。然后，用圆形靶标本进行了实际尺寸的穿孔实验。通过计算机断层扫描（CT）方法，通过该实验验证了套管/水泥界面的数字剥离面积。

数值模拟和实验结果表明，固井界面脱胶主要是由于套管，水泥护套和射孔过程中地层之间的位移差异引起的。套管/水泥界面的剥离面积和微环隙大于水泥/地层界面的剥离面积和微环。敏感性分析表明，固井界面的脱胶面积与正己烷炸药（RDX）载荷和套管的弹性模量呈正相关关系。因此，如果满足主要的套管设计标准，则应首选弹性模量较低的套管，以减少由穿孔引起的胶结界面的剥离面积。