As commodity prices have declined, refracturing has given operators an alternative way to obtain positive returns with lower investment under constrained capital markets. A major operator in the Haynesville shale was interested in determining the optimum method to refracture several laterals located directly offset to each other. In this case, a four-well pad was initially drilled to drain the section. The viability and optimum sequence/design of refracturing this four-well pad was unknown. There were many uncertainties around refracturing this pad including refracturing approach/method, refracture timing, refracture sequence (well order), refracture job size, and number of wells to refracture to obtain the greatest return on investment.
In this paper, an integrated refracturing workflow was created and applied to determine the optimum refracturing strategy for this four-well pad. This comprehensive workflow represents a multidisciplinary approach that integrates complex hydraulic fracture models, geomechanical models, and multiwell production simulation. The unique approach in this workflow was the ability to couple simulated 3D reservoir pressure with a geomechanical finite-element model (FEM) to quantify the changes to the magnitude and azimuth of the in-situ stresses from the depletion. Then, the altered stress field was utilized as the input for modeling the new fracture system created by the refracturing treatment. A separate refracturing workflow was developed to calibrate the proposed four-well refracture study by fracture modeling and production history matching of a previously refractured well a few miles away, and it was also applied to run sensitivities on modeling the proposed refracture treatments on the four-well pad.
This new unique approach to studying pad refracturing was beneficial to understanding the viability of refracturing this four-well pad in the Haynesville shale and the influence of refracturing on the existing fracture networks. The optimized completion strategy and workflow can help operators calibrate expectations and optimize the refracturing process for pad wells to obtain the best return on investment.
The Haynesville shale is a unique dry gas formation located in northeast Texas/northwest Louisiana with high reservoir pressure, gradients of 0.85 to 0.9 psi/ft (Fan et al. 2010; Thompson et al. 2010). The higher reservoir pressure and clay content cause the play to be prone to creep, which causes severe permeability reduction as wells are produced with high drawdowns (Thompson et al. 2010; Okouma Mangha et al. 2011; Indras and Blankenship 2015). By controlling the severe production drawdown, existing fracture networks were maintained for longer periods of time (Baihly et al. 2015).
