PY-1 is one of the few fields in India producing hydrocarbons from Fractured Basement Reservoir. The field was developed with nine slot unmanned platform with gas exported through a 56 km 4" multiphase pipeline to landfall point at Pillaperumalnallur. Field was put on production in November 2009 with three extended reach wells.

The production performance of the field had some surprise and declined earlier than expected. As a result, based on the conclusions drawn from an integrated subsurface study, a two wells re-entry campaign to side track wells Mercury and Earth was planned to be executed in Q1 2018.

The objectives of this paper are twofold:

  1. Review the production performance of a granitic basement gas field and share learnings which may be useful for similar fields being developed elsewhere.

  2. Share the fit-for-purpose modelling workflow adopted to identify the opportunities and estimate reserves

Methods, procedures, process

The workflow consisted of following:

  1. Key uncertainties impacting GIIP and recovery were ascertained through subsurface and production data analysis

  2. Analytical reservoir engineering tools such as material balance was used to estimate GIIP from production and pressure analysis. Importance of having PDG installed in offshore wells with unmanned platforms are highlighted.

  3. The uncertain petrophysical parameters such as porosity and was constrained based on GIIP estimates from material balance

  4. Prosper models were used to understand and predict the well performance and optimal tubing size to avoid liquid loading

  5. Fit-for-purpose simulation models were constructed to quantify impact of key uncertainties on production forecast and recovery

In order to mitigate the operational risks, drilling services were outsourced as a turnkey project to an industry leading service provider.

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