During hydraulic fracturing, very small seismic events (microseisms) are generated due to high-pressure fluid injection. These events occur when increased pore pressure causes small natural fractures in the rock to slip. Although these microearthquakes are too small to be felt, they can be detected using specialized seismic sensors.
Microseismic monitoring is used to map fracture growth by locating these events in space and time. The recorded data provide information about fracture geometry, including fracture length, height, and orientation. This helps engineers understand how fractures propagate within the reservoir.
Data are collected using arrays of sensors placed either in nearby monitoring wells or at the surface. Advanced processing techniques are then used to determine event locations and characteristics such as magnitude and seismic moment.
Fractures typically propagate in the direction of maximum stress. However, in formations with low stress contrast, fracture patterns can become complex. Microseismic monitoring helps identify whether fractures are simple or complex and can distinguish between hydraulic fractures and reactivated natural fractures.
This technique is also important for field development planning, such as optimizing well spacing, stage design, and injection parameters.
