Intra-Well Frac-Driven Interactions FDIs: Types, Causes, Consequences and Diagnostic Value Learnt from Actual BH Data

Abstract

Abstract Frac-Driven Interactions (FDI)s are the most pressing topic of discussion within the fracturing community at the present time. The findings of this paper are based on review of BH pressure and temperature data collected in multiple wells during active fracturing operations. Detailed examination of the data revealed similarities between inter- and intra-well interactions, including presence of fracture shadowing as well as temporary and long term frac/frac connections. The cause of most frac/frac connections was poor cement quality that resulted in migration of some of the injected fluid into the passive well segment. In many such cases the volume of migrated fluid was small with minor effect on fracturing results. In some others the migrated fluid rate was high enough to cause reactivation of one or more passive fractures. The surprising results included fluid migration from the active fracture into the passive well segment that started and stopped abruptly while active fracturing was still in progress. This unusual behavior, called reverse screen-out and reported for the first time in fracturing literature, appears to be caused by near wellbore blockage of sand which was being carried by the migrating fluid towards the passive well segment. These events were associated with build-up of sand plugs inside the passive well segment caused by sand flowback during the shut-in period. The paper shows how even a very small volume of sand can cause formation of a sand plug. Frequency of reverse screen-out was about 20% of the nearly 300 frac stages in the three wells reviewed for this paper. Paper also shows how analysis of intra-well FDIs can be used as a diagnostic tool for determination of the effectiveness of the individual stages of the created fractures. This feature allows faster evaluation of the effectiveness of new materials and techniques by comparing the differences in adjacent fracture stages performed with and without the changes.