Abstract: The invention relates to oil-gas engineering, in particular to maintaining wells in the oil-gas industry and, more specifically the hydraulic fracturing seismic monitoring. A first method is carried out when a pulse amplitude is sufficient for opening a strike-slip fractures around a crack, wherein said crack is detectable with the aid of traditional means for passively recording seismic waves produced by acoustical events related to the opening of strike-slip fractures and by interpreting the position of the thus obtained events in the form of the events adjacent to the crack.

Abstract: A method and device for on-line foam quality acoustic monitoring are suggested. As per the invention, the method provides for the following: at least one emitter/receiver pair is placed in a close vicinity to the foam flow; at least one acoustic pulse is emitted; time, within which the acoustic pulse overcomes the way from the emitter to the receiver, is recorded; acoustic pulse speed (sound speed) is determined by analyzing an acoustic response of the receiver. After that, pressure in the foam in the area between the emitter and receiver is defined and the foam quality ? is calculated as per the equation: ? = 1 2 ± 1 4 - N ? fl ? p C fm 2 , where: Cfm—speed of sound in the foam, p—pressure, ?fl—fluid density, ?—foam quality, N—polytrophic expansion coefficient (N=1 for isothermal process; N=1.