Stress shadow effect during multi-stage hydraulic fracturing with different wellbore arrangements

Abstract

Abstract Multi-stage hydraulic fracturing was simulated using a two-dimensional universal distinct element code (UDEC). Five fracturing stages were considered along horizontally (i.e. parallel to the minor principal stress direction)- and diagonally (i.e. inclined to the minor principal stress direction)-positioned wellbores within the pay zone, where the spacing between wells was changed to 50 m and 100 m. Progressive fracture propagation and the evolution of stress shadow with sequential multi-stage fracturing were monitored. A marked stress shadow was observed for closer well spacings under both horizontal and diagonal well arrangements, leading to a significantly asymmetric fracture propagation about the wellbore. The diagonal well arrangement showed a nearly unidirectional fracture propagation after the first stage for the closer well spacing case. Fractures of sequential stages predominantly developed in alternating directions at greater well spacings irrespective of the wellbore arrangement. Progressive fracture development also showed that fractures created at earlier stages could further extend due to the stress shadow of later fracturing stages, and this effect is more pronounced for closer well spacings. After five stages, the overall fracture lengths indicate that a higher fractured area was created by horizontal well arrangement for any case of well spacing. Finally, the importance of optimizing the fractured area and fracture controllability to contain the fractures within the pay zone was highlighted.