Study on acoustic emission response characteristics of sandstone directional fracturing under different filtration surfaces

Abstract

In order to study the influence of filtration on rock directional hydraulic fracturing under different filtration surfaces, 300 mm×300 mm×300 mm sandstone specimens with intermediate drilling holes and directional prefabricated fractures were selected, and the method of applying waterproofing agent on the specimen surface was used to control the fluid loss, and four groups of sandstone specimens with reduced filtration surface were made, including agent A without waterproofing, fracture surface coated with waterproofing agent B, hole wall coated with waterproofing agent C, fully coated with waterproofing agent sandstone specimen D. We carry out true triaxial directional hydraulic fracturing and real-time acoustic emission monitoring to analyze and study the acoustic emission energy rate, cumulative energy and fracture extension law of sandstone specimens under different filtration surfaces. The results show that with the increase of filtration surface, the peak value of acoustic emission energy rate of sandstone specimen decreases gradually, while the cumulative energy needed to complete the fracturing failure process of sandstone specimen increases gradually; in the process of fracture extension, with the increase of filtration surface, the greater the filtration loss, the faster the fracture deflects to the maximum principal stress σH; when the fracture deflects to the same deflection angle α, the fracture extension length L will gradually decrease.

Keywords

• directional hydraulic fracturing
• hard roof
• impact disaster
• filtration
• acoustic emission
• energy rate
• cumulative energy