| Popis: |
A clastic heterogeneous reservoir at onshore India which consists of fine grained sandstone and siltstone along with interbedded shales make the reservoir tight and low permeable. Production though self-flow from wells in the area is unsustainable, reservoir drainage by vertical wells did not appear to be efficient. In order to exploit this reservoir better, geomechanical guidance was considered, so that drilling of horizontal wells and multi-stage hydraulic fracturing can be evaluated for enhanced reservoir contact in four wells. This paper discusses how geomechanics influenced optimization of well delivery that resulted in enhanced production. Considering the complexities associated with this reservoir and its development, the need for extended reservoir contact was recognized by multi-stage fracturing over a horizontal well. However, absence of horizontal or highly deviated wells around area in the past made well placement, wellbore stability management and effectiveness / suitability of well completion more challenging task. As this is a major investment decision, a thorough geomechanical study was proposed. With all available data from offset wells and field measurements robustly calibrated geomechanical model was generated that described in-situ stress regime, reservoir pressure and rock mechanical properties. The geomechanical model identified potential intervals for well placement and also recommended minimum required mud weight to drill the planned wells. Upon optimizing well planning with geomechanics, the wells were drilled with real-time geomechanics support. Geomechanics acted as a decision support tool from well planning through drilling to stimulation. Appropriate decisions were taken to improve the well plans during operations based on borehole condition for wellbore instability. Real-time geomechanical monitoring helped to deliver horizontal wells timely with good hole geometry. As having a good quality hole is essential for successful casing run, cementation, perforation and fracture propagation, drilling of these wells with correct mud weight as per the model is essential. Achieved quality borehole and then further improved the model with subsequent drilling of wells. In addition, geomechanical models also helped to develop appropriate strategy for multi-stage fracturing. Planned horizontal wells were drilled with recommended mud weight towards minimum horizontal stress (Shmin) direction to perform multi-stage fracturing. Some wells have exhibited production around 4 times higher than average production from a vertical well. Actual production rates also appeared closer to conservative prognosis case. While geomechanics play vital role at different stages of reservoir development, appropriate application of this science has guided number of timely decisions step by step. As a result, informed decisions were taken during operations which resulted in obtaining enhanced production from a challenging reservoir. This methodology not only explored opportunities for production enhancement, but also set a real example for successful implementation of geomechanics for well placement and fracturing. |
