Analysis and optimization of multiple factors influencing fracturing induced stress field

Abstract

The induced stress field caused by hydraulic fracturing plays a key role in controlling the formation characteristics of fractures and is the essential prerequisite for optimal design of fracturing parameters. In order to determine the disturbance range of induced stress field on fracture morphology, the multiple factors analysis and optimization are an important inspect. Setting the induced stress control range (ISCR) as the evaluation objective, it can be defined as the combined response of the peak value of induced stress difference and stress steering distance, taking them as double evaluation indexes. Six uncertain fracture parameters with a reasonable range are used to fit the response of evaluation indexes. Through the finite element numerical simulation method, the induced stress field around the fractures can be calculated and the evaluation indexes are described quantitatively. Applying the multi-factor orthogonal test method, combined the matrix analysis model with the fuzzy comprehensive evaluation model, these fracture parameters are evaluated and optimized. The results show that the influence factors on the ISCR in the descending order are determined as follows: fracture height, fracture net pressure, Poisson’s ratio, maximum and minimum horizontal stress ratio, fracture spacing and its number. According to the multi-factors sensitivity analysis results, the selected levels of different factors are optimized and the combination of parameters optimization is screened out. It provides a theoretical basis to control the reservoir stress field for the optimization of the field fracturing treatment.