Microseismic monitoring of a hydraulic-fracturing operation in a CBM reservoir: Case study in the Cerrejón Formation, Cesar-Ranchería Basin, Colombia

Abstract

Passive-seismic monitoring techniques were implemented for source characterization of microseismic events generated during a hydraulic-fracturing operation in a coalbed-methane (CBM) reservoir in Colombia. Hydraulic fracturing is a common stimulation technique performed to increase the permeability and productivity of conventional and unconventional reservoirs. Its use has increased in the last decade in several countries, including Colombia, and it is expected to keep rising in the following years. The success of a hydraulic-fracturing operation can be assessed in different ways, of which microseismic monitoring is the most common technique. This method can be implemented using surface or downhole seismometers and allows the characterization of microseismic events associated with the fractures generated. A workflow for passive-seismic data analysis was developed to characterize microseismic events (i.e., hypocenter location and source-mechanism analysis) from data acquired with surface stations and to obtain important parameters for a hydraulic-fracturing design such as the stimulated reservoir volume (SRV), orientation, and anisotropy of horizontal stresses and a discrete fracture network (DFN). This workflow was implemented in a case study in Colombia in which a coalbed-methane reservoir in Cesar-Ranchería Basin was stimulated by hydraulic fracturing. Surface seismometers were deployed around the wellhead to monitor the microseismicity generated and to estimate all the design parameters of the stimulation.