Finding repeats on sequences is of great interest in different areas such as biological sequences analysis or data compression (for instance). A lot of methods using suffix trees, suffix arrays or automata have been developed to perform the search of repeats. Here we present an algorithm (heuristic) to find repeats on very long sequences based on a factor oracle. Since it is a heuristic, some improvements are under study and give much better results (also presented). This algorithm leads to applications in bioinformatics and data compression.