DEEP- WATER RESERVOIR APPRAISAL IN THE PHILIPPINES: AN INNOVATIVE EXTENDED TEST

Abstract

The extended test arrangement for the Galoc Field, offshore Philippines, consisted of a semi- submersible drilling rig having a conventional spread mooring to which was connected a storage tanker. The tanker was moored stern to the rig by a disconnectable hawser. At its bow, two anchor lines, also disconnectable, were laid in N/S quadrature symmetrically disposed about the NE/SW tanker orientation. The tanker was thus free to depart from the location, either to discharge its stored oil or to stand by/take cover in the event of heavy weather conditions exceeding the capacity to stay on location.

At each lifting, a bottom- hole flowing pressure survey was conducted immediately prior to shut- in. When the well was shut in to disconnect the tanker, the pressure survey incorporated the pressure build- up and subsequently, after reconnection, the pressure drawdown transients. The data batches were collected on digital tapes for analysis.

With only three wells in the structure proper, the geological complexity of the reservoir setting did not permit a definitive interpretation of reservoir behaviour during the extended test. However, the use of generic descriptions of submarine fan turbidite deposits, in com- bination with the results obtained from the three wells and history- matching attempts in reproducing the extended test behaviour, did result in a good level of confidence that we had derived an acceptable model of the Galoc Field. The forecast production profiles derived for the various development schemes were thus considered to be reliable enough for comparative economic analyses of the development options.