Abstract

Open-hole log responses in an area with complex geology and a vast variety of reservoir rock and fluid properties are sometimes very difficult to use for fluid typing. The Reservoir characteristics of the multi-stacked hydrocarbon system commonly found in the Kutei Basin may vary from volcanic rich to highly bioturbated formations, from fresh to saline formation water, from low to high gravity hydrocarbon, from depletion to strong water drives and from low to high resistivity pays. The role of the formation tester is therefore very important. It is even more critical in mature fields such as Attaka or Sepinggan, where multiple-zone completions are normally applied in low resistivity and thinly bedded reservoirs. This practice may cause some problems in new wells where depleted versus normal pressured reservoirs have ambiguous log responses due to invasion. All of above conditions may result in the need for numerous fluid identifications to be performed and many pressure points to take for pressure monitoring.

Recently Unocal's drilling efficiency in East Kalimantan has improved dramatically. The wells are now drilled not only faster but also at lower cost without giving up borehole quality and safety for further evaluation. The demands of high drilling performance has a consequence of expensive rig rental cost. This factor provides a challenge in which well evaluation needs must be conducted effectively and efficiently. This can not be done only by reducing the amount of logging runs or the number of formation tester points. The subtasks of the approach are to improve the logging runs and the capability of the formation tester which can reduce the evaluation time and to utilize a well-integrated data base. Efficient logging jobs have been designed. A new generation formation tester is used to obtain a considerable amount of real-time fluid identifications. This tool utilizes a down-hole resistivity sensor, quartz gauge, optical gas detector, fluid spectrometer and multiple sample chambers. It also is capable of pumping formation fluid from the flowline to the borehole allowing better fluid identification and cleaner samples. These new capabilities allow the formation tester run to be completed in a much shorter time. The whole effort has saved Unocal millions of dollars, and many days of rig time.