Identifying the flow dimension in fractured rock using an interference test

The actual flow dimension in fractured rock may be between 2-D cylindrical flow and 1-D linear flow. This paper demonstrated the importance of the method used to identify the flow dimension in fractured rock correctly. A case study of a long-duration interference test was presented to illustrate the application of Barker’s type curves and to identify a flow dimension in fractured rock. It was difficult to judge the flow dimension based solely on the type-curve matching. Both geological and production data could also be taken into account to help select the appropriate flow dimension. To investigate the sensitivities to pumping time for each observation well, the σ function was defined for an observation well equals the sum of the square relative-errors between the observed and predicted drawdowns. For a long-duration interference test with sufficient pumping time, the  function of an observation well is sensitive to the flow dimension. An empirical rule,  (dimensionless time) > 100, was developed for estimating the minimum pumping time required in an interference test to identify the flow dimension between the production well and an observation well in fractured rock.   Key words: Interference test, fractured rock, flow dimension.