An oft-occurring outcome of modern fractured horizontal well production systems is considerable interactions between adjacent hydraulic fractures; in the same well (intra-well), or in offset wells (inter-well). An unwanted consequence of these interactions is production interference. Inter-well interactions can cause production re-routing from one well into the adjacent well, and occasionally even short-term loss of production from one of the wells. Effects of intra-well fracture interactions may include production re-distribution within the created fractures, and, patchy depletion of the reservoir surrounding the horizontal well.
Causes of intra-well interactions include stress shadowing and Dynamic Active Fracture Interactions (DAFI). Under common fracturing practices these can cause unpredictable deviations in fracture growth path which can even lead to coalescence of some fractures and non-uniform production from individual fractures. Another important outcome of these interactions is differences in created fracture lengths, with some fractures extending a long distance into the reservoir. Recent trends towards larger size treatments and shorter spacing between individual fractures are intensifying these effects.
Inter-well interactions include frac-to-frac connections that hydraulically link the two wells together; either temporary (while fracturing only), or long term with conductive links. The latter can cause immediate production interference. Another less severe type of interaction is fracture shadowing, which may cause delayed production interference.
Paper discusses how these interactions are influenced by the stress environment, formation mechanical properties, type of completion (openhole liner, cemented liner, single fractures vs. multiple fractures), fracture orientation and spacing, well spacing, and perforation schemes. It presents completion steps that reduce the uncertainty in fracture growth path and location of longer fractures. It also shows how and why combining these steps with simultaneous and zipper fracturing can reduce damage to the wellbores and the extent of production interference.
On the positive side, analysis of fracture interactions can also provide valuable information about fracture characteristics; including estimates of length, orientation and conductivity, etc. With proper preparation, the information can also be used for real-time evaluation of the created fractures and treatment modifications to reduce severity of production interference.