Diversion Techniques Applications in Unconventional Resources Fields

Abstract

Saudi Aramco has made substantial progress in developing its unconventional gas resources with Plug and Perf (PnP) completions and multistage slickwater fracturing, with optimal production performance. Wells in Jafurah basin are generally completed with 5,000 feet horizontal lateral and up to 33 stages with 4 to 5 clusters per stage. Increasing the number of clusters per stage in such completions could lead to cost and efficiency optimization, but also increases the risk of having non-stimulated clusters, considering geomechanical heterogeneity, and without providing sufficient pumping rate. Thus introducing diversion techniques becomes a necessity in this unconventional play to optimize cluster efficiency, improve operational efficiency, and thus reduce cost. Near wellbore chemical particulates and intra-well perforation mechanical diversion techniques from degradable materials found their wide application in different unconventional assets. A mega-diversion experiment with both techniques took place in one of the wells, where a damaged section of the lateral did not allow regular PnP operations at the toe. Laboratory tests before operation ensured degradation of the material is within operational thresholds for positive isolation. The lateral section below the casing deformation (1,200 ft in the toe section) was planned with 30 clusters in one single stage, with the intrawell diversion technique. Another eight stages in 1,200 feet were attempted with a standard five cluster stages as a baseline. The remaining 2,400 feet of the lateral were stimulated with eight stages, 10 clusters per stage, and sequential application of both intrawell mechanical and near wellbore diversion technologies. Other wells in the area, which had damage in the casing, were also completed with mechanical diverters. The 1,200 ft lateral section was successfully stimulated without additional well intervention operations with a selected diversion technique. Proppant placement challenges were encountered in the regular five cluster stages with significant improvement in the subsequent 10 cluster stages introducing diversion. Positive diversion indication was confirmed by surface pressure observations and mainly proppant placement success. Multiple instances of non-typical pressure behavior were observed during placement of the mega-diversion stages. This pressure behavior is the subject of technical analysis and results will feed into the future design strategy. The intrawell mechanical diversion technique showed positive diversion indications in different wells in Saudi Arabia, with good repeatability of slickwater propped fracturing treatment success. This technique could be utilized whenever wellbore accessibility challenges are encountered, or during refracturing application cases. Both diversion technques could be used efficiently to stimulate the clusters and optimize well intervention operations, by minimizing the number of stages per well without compromising stimulated reservoir volume.