The declining production in many mature Adriatic fields is normally offset by drilling new deviated wells. Recent technology has shifted the focus from metric reservoirs to thinly laminated intervals (thin beds), which were, until now, not produced because of the difficulties in defining gas-bearing zones. The thin beds are challenging because the laminate is half an inch or less thick, far below the resolution capabilities of standard logging tools. Therefore, it is crucial that bottom hole cores are cut to assess the petrophysical and geomechanical rock characteristics.
The small diameter of the boreholes and the unconsolidated nature of those reservoirs make coring operations very challenging; recent attempts have met with very poor results and negligible recoveries.
A case history of an Adriatic well is presented in this paper, where nine meters of core were cut and successfully recovered (100%) from a 6-in. borehole.
The Low Invasion Core Gard technology was utilized in this job, and included a long shoe and modified hydraulic technologies that made minimizing fluid invasion around the core. The high-quality samples obtained will allow detailed laboratory analyses. The reduced uncertainties in reservoir properties (including porosities, saturations and permeabilities) will enhance future field development campaigns.
The new innovative coring approach described in this paper will certainly play a key role in optimal exploration of thin beds gas reserves.
