Abstract: A method of drilling a well by utilizing AE/MA measurement which has the steps of monitoring an AE wave emitted at the periphery of the well, and drilling the well without lost circulation by providing lost circulation preventing means in the well if the energy of the AE wave emitted at the periphery of the well increases. Thus, the method can confirm a lost circulation layer, i.e., the size, the place and the direction of the underground crack to further determine whether further drilling is necessary or not.

Abstract: A method of collecting geothermal steam using Acoustic Emission Microseismic Activity (AE/MA) measurement includes the steps of (a) surveying an AE wave emitted in subsurface cracks to obtain the size of a water permeable geothermal reservoir by analyzing the AE wave, (b) further surveying the AE wave emitted in and around the periphery of the geothermal reservoir, (c) operating the wellhead valve of the geothermal well connected with the geothermal reservoir, thereby extending or preventing the extension of the geothermal reservoir in accordance with the information obtained in step (a) and/or step (b), thereby stably obtaining a predetermined quantity of steam of high quality. Thus, the method can stably obtain geothermal steam of high quality by accurately surveying or monitoring subsurface cracks by an AE measurement technique and propagating the subsurface cracks or suppressing the propagation of the cracks.