Technical Note: An inversion algorithm to estimate maximum and minimum horizontal stress based on field test data for sleeve fracturing

摘要

An algorithm is developed to estimate maximum and minimum horizontal stress using experimental data from sleeve fracturing experiments. The algorithm is developed by analyzing the crack initiation, propagation and interaction behavior between primary and secondary cracks based on the Finite Element Method with Cohesive Zone elements. Five key quantities can be obtained from data curves and comprise the basis of the algorithm in a manner consistent with an approximate model based on stress analysis around the borehole. The algorithm has been validated by 100 synthetic data cases covering various parameter combinations. Moreover, quantifying the degree of uncertainty in the stress prediction indicates strongest dependence on detecting when the borehole deformation from the first fracture(s) is impacted by growth of secondary fracture(s). Validity based on simulated data motivates new methods for high resolution strain sensing during sleeve fracturing especially for the purpose of accurately detecting secondary fracture initiation.