They also were measured while stepping as far as they could in three directions: forward, to the side and backward (the maximal step length test).

These three kinds of techniques of well testing, step rate test and injection test at pre-fracturing are conducted to acquire formation parameters and applied in one CBM well successfully.

It first appeared in 1967, the "Berne Convention" Stockholm text, expressed as a result of the three conditions, so it is called three-step test.