  Ultra-long Gamma-Ray Bursts (ulGRBs) are Gamma-Ray Bursts (GRBs) with an
unusually long emission in X and gamma rays, reaching durations of thousands of
seconds. They could form a specific class of high-energy transient events,
whose origin is still under discussion. The current sample of known ulGRBs
consists of a few tens of events which have been detected so far by the Burst
Alert Telescope (BAT) aboard the Neil Gehrels Swift Observatory and some other
instruments. The SVOM mission which is scheduled to begin operations after 2021
could help to detect and observe more ulGRBs thanks to its soft gamma-ray
telescope ECLAIRs. After an introduction on ulGRBs and the SVOM mission, we
present the results of our simulations on the capabilities of ECLAIRs to detect
ulGRBs. First we use the sample of ulGRBs detected by Swift/BAT and simulate
these events through a model of the instrument and the prototype trigger
software that will be implemented onboard ECLAIRs. Then we present a study of
the ECLAIRs capabilities to detect a synthetic population of ulGRBs built by
transporting the ulGRBs detected by Swift/BAT to higher redshifts. Finally we
give an estimate of the ulGRB rate expected to be detected by ECLAIRs and show
that ECLAIRs can detect at least as much ulGRBs as BAT.
