This paper introduces the principles of waterflood induced fracture

clarifies their basic characteristics and proposes the methods to identify them.Then the waterflood induced fracture of Well A0 group of Chang 6 reservoir in W area in Ansai oilfield

Ordos Basin has been identified by these methods.With larger scale

long extension and high permeability

waterflood induced fracture are tension fractures which are not controlled by single stratum in vertical extension.Their trend direction are generally along the present maximum horizontal principal stress or the main seepage fracture direction.In a long term waterflooding process

the following are clear indications for the establishment of waterflood induced fracture between producer and injector wells:if the oil wells shows a gradually dominant direction of flooding

the water-cut curve presents step-type rise

well test interpretation has the character of fracture seepage

the water injection profile of the injection well gradually presents finger-like water absorption characteristics

inflection point appears in water injection index curve

tracer or water flooding front monitoring showed good connectivity between wells.