Well and Reservoir Surveillance to Improve Geological Understanding and Optimize Field Development. Examples from the Piltun Development

Piltun forms the northernmost part of the larger Piltun-Astokhoye oil, gas and condensate field, located in shallow offshore waters off the north-eastern shores of Sakhalin Island. The development targets multiple stacked oil rim accumulations within an asymmetrical anticlinal structure. The primary reservoirs are shallow marine clastic deposits of the Upper Miocene Lower Nutovsky Formation. Whilst the original Piltun-Astokh appraisal campaigns addressed the first-order field uncertainties by defining the stratigraphy, structure, reservoir distribution and quality, fluid fill and short term well in-flow performance, significant second-order uncertainties remained unresolved. Information on mid- to longer term reservoir performance was generally lacking as the development concept for the field was defined. This required planning for the acquisition of such data early on in the implementation phase. This paper explains how Well and Reservoir Surveillance data was acquired, interpreted and used to drive business decisions in the Initial, Interim and Current phases of the development.