Abstract

Traversing the tight unconventional shale reservoirs is an Engineering challenge. The paradigm shift from conventional to unconventional reservoir resource exploitation was endured upon with Well CS#A, the shale gas/oil Well in Cambay Basin. The domain expertise in conventional reservoirs was manoeuvred, redesigned and translated into successful Hydraulic fracturing execution in CS#A. Frac data was further analysed and assimilated to draw the characteristic frac behaviour of Indian Cambay Shale. Cambay shale is the main source rock, thermally well matured and falls within the oil window but have never been explored for production before.

Triaxial Compressive Strength Test with Acoustic Velocities and various lab tests were performed to determine shale rock mechanics and a suite of petrophysical properties. CBL-VDL-GR-CCL logs ensured good cementation. Specialised 3D model Simulator was used with the best input parameters to conceive the best and specific design for Cambay shale. Initially, slick water was used for Step Rate Test (SRT). MF analysis carried out to ascertain key informations and subsequently, changes were incorporated in Main frac design simulation. The frac fluid was exclusively designed and optimised through tests in Laboratories to give best results and to check the compatibility with Cambay Shale & post job flow back recovery. Closure analysis was done by the most reliable G Function time BHP analysis and the same was verified with Square root time plot. The real time pressure graph trend showed net pressure increase during proppant packing suggesting better frac behaviour and fracturing prospects. Post Job, the real time Net-Pressure match facilitated simulation of real time data to know the actual frac dimesions created after job, the frac profile, validate the permeability and stress, check the conductivity gain etc.

The extensive and exhaustive research, planning and execution of hydraulic fracturing job in CS#A proved the producibility and potentiality of Cambay Shale as the Well has produced Oil. The Geological data, the log data combined with the experience gained and data inferred by exploitation of this Cambay shale gas/oil Well "CS#A" through Hydraulic fracturing will be a boon for the E&P of Unconventional Shale in India.

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