Analysis of geological factors affecting propagation behavior of fracture during hydraulic fracturing shale formation

The complexity of hydraulic fracture network generation during the fracturing of shale reservoirs is a key indicator of the effectiveness of fracture stimulation. To obtain as large a reservoir stimulation volume as possible, this paper reviews articles on the study of hydraulic fracture propagation mechanism during hydraulic fracturing, analyses the factors affecting hydraulic fracture propagation, and classifies them into two categories: geological factors and engineering factors. In particular, the geological factors affecting hydraulic fracture propagation are classified into five categories: mineral composition of the shale, connections between mineral grains, defects in the shale, geostress, and temperature. Various influencing factors act together, resulting in the hydraulic fracture propagation path is difficult to predict. Therefore, this paper firstly explores the hydraulic fracture propagation pattern under the action of single geological factors and specifies its action mechanism; secondly, it also analyses the hydraulic fracture propagation pattern under the combined action of multiple geological factors and analyses its action mechanism. It is clear that relatively high brittle mineral content and temperature, low stress anisotropy and cementation strength, and a more developed natural fracture network are conducive to the generation of a complex fracture network. By analyzing the influence mechanism of single factors and multiple factors, the influence mechanism of geological factors on hydraulic fracture propagation is identified, guiding the optimal design of hydraulic fracturing.