Microseismic Monitoring of Multistage Hydraulic Fracturing in Complex Reservoirs of the Volgo-Urals Region of Russia

Abstract

Abstract One of the most frequently used and efficient flow enhancement methods is creation of a wide network of induced formation fractures and activation of filtration in natural fractures with help of hydraulic fracturing. This technology is being actively used both worldwide and on the whole territory of Russia. Geomechanical properties of a formation, its structure, the direction of maximum horizontal stress play a critical role in application of the flow enhancement method with use of hydraulic fracturing. The majority of currently developed reservoirs have a complex, inhomogeneous structure; that is why adequate prediction of hydraulic fracturing outcome becomes a challenge. In addition, execution of such expensive and labor-consuming operations without painstaking planning and understanding of the final result, especially in case of massive hydraulic fracturing on the field, is practically impossible. In order to solve this task, a whole complex of solutions was developed, including microseismic monitoring - a passive seismic listening technique which enables mapping of the fracture network created during hydraulic fracturing, determining their principal orientation and evaluating the reservoir geomechanical properties. Microseismic monitoring of hydraulic fracturing is one of the most reliable means to map the fracture network formed as a result of hydraulic fracturing. Fractures often feature a rather complex structure that does not allow for modeling of hydraulic fracturing outcome with required precision based on reservoir geology and fluid dynamics model. This leads to low fracturing efficiency, significant time and money costs. This paper provides results of microseismic monitoring of hydraulic fracturing performed on the well of the oilfield of the Volgo-Urals region of Russia in 2014, demonstrates importance of comprehensive study of fracture space structure on the field for effective development. As a result of monitoring presence of two fractures systems different by directions were recognized, several conclusions regarding possible reasons of that were made and conclusions about the necessity of further investigations of reservoir properties, which is built with rocks of different structure. One of the most frequently used and efficient flow enhancement methods is creation of a wide network of induced formation fractures and activation of filtration in natural fractures with the help of hydraulic fracturing. This technology is being actively used both worldwide and throughout Russia. Geomechanical properties of a formation, its structure, the direction of maximum horizontal stress play a critical role in application of the flow enhancement method involving hydraulic fracturing. The majority of currently developed reservoirs have a complex, inhomogeneous structure; that is why adequate prediction of hydraulic fracturing outcome becomes a challenge. In addition, execution of such expensive and labor-consuming operations without painstaking planning and understanding of the final result, especially in the case of massive hydraulic fracturing in the field, is practically impossible. In order to solve this task, a whole complex of solutions was developed, including microseismic monitoring - a passive seismic listening technique which enables mapping of the fracture network created during hydraulic fracturing, determining their principal orientation and evaluating the reservoir geomechanical properties. Microseismic monitoring of hydraulic fracturing is one of the most reliable means to map the fracture network formed as a result of hydraulic fracturing. Fractures often feature a rather complex structure that does not allow for modeling of hydraulic fracturing outcome with required precision based on reservoir geology and fluid dynamics model. This leads to low fracturing efficiency, significant time and money costs. This paper provides results of microseismic monitoring of hydraulic fracturing performed in the well of an oilfield of the Volgo-Urals region of Russia in 2014, demonstrates importance of comprehensive study of fracture space structure in the field for effective development. As a result of monitoring, presence of two fracture systems different in directions were recognized, several conclusions regarding possible reasons for that were made as well as conclusions about the necessity of further investigation of properties of the reservoir composed of rocks with different structure.