Evolution of completion techniques in the Haynesville Shale has increased the estimated ultimate recovery (EUR) on new wells by almost double compared to the average EUR of wells completed earlier in the reservoirs' development. Because of inadequate early-time completions, large amounts of reserves were bypassed. Refracturing methodology requires reevaluation, given the large inventory of understimulated wells and the potential EUR uplift.
Refracturing methods in the Haynesville Shale have been performed primarily by degradable particulate diversion using a bullhead treatment or, more recently, by cementing a smaller casing liner inside the existing wellbore. The ability to add additional stimulated reservoir volume and restore conductivity requires overcoming the primary challenges of depletion and discrete zonal isolation along the wellbore. The procedures used in both methods to address such challenges and achieve these goals can be analyzed, and the effectiveness of each approach can be measured using production data.
While both methods mentioned have experienced successful results, when evaluating the effectiveness of the treatment, the potential EUR uplift has to be considered since the two methodologies can vary greatly in cost. Certain cases might even require the mechanical isolation method instead of a bullhead method if the integrity of the existing tubulars cannot withstand pressure experienced during a refracturing treatment. The current dataset suggests that the total volume of reserves added from mechanically reworking the wellbore is generally larger than the particulate-diversion method. However, the cost to rework the wellbore and the volume of the refracturing treatment is also generally larger. The refracturing candidate well should be carefully analyzed to determine which type of treatment to apply.
A dataset of more than 40 wells, inclusive of wells restimulated by both techniques, is analyzed to assess the effectiveness of each refracturing technique. The production results were examined along with the original stimulation and restimulation treatments to determine the consistency and viability of the different techniques.