FORMATION EVALUATION OF 'FEAW' SAND (MULTI LAYER RESERVOIR) TO FIND NEW INTERESTING ZONES IN MATURE FIELD, STUDY CASE: 'HATI' FIELD, CENTRAL SUMATRA BASIN

摘要

Hati field is the world largest steam flood and one of the mature fields in Central Sumatra Basin. The "FEAW" sand represents undeveloped reservoir in those field. This sand is considered as the shallowest reservoir in the Hati field (about xl20-x300 feet depth). Beside that, "FEAW" sand is considered water bearing zone because of the high water saturation. This assumption comes from the homogen reservoir model. Calculation of water saturation in "FEAW" sand was done using parameters generally used in this field. Beside that, all of "FEAW" sand zone from top to bottom were calculated using shaly sand method (Simanduox method). The result showed that water saturation is mostly high in "FEAW" sand. Rock properties of "FEAW" sand were not well identified and characterized previously. Logging in Hati field mostly just covered the productive reservoir, while "FEAW" sand was usually not logged and located behind the casing. Therefore logs data for the sand is limited. There is lack of information to determine reservoir potential, especially in calculating Original Oil in Place (OOIP). The purpose of this research is to give evidence that "FEAW" sand is a prospect reservoir to be developed using formation evaluation method.Formation evaluation study of "FEAW" sand in this paper was done the determine zone of new interest in a mature field by determining rock properties correctly. Firstly, a detail zoning were made on the interval "FEAW" sand. This step was then followed by new petrophysics properties determination like cementation exponent (m) and resistivity of water (Rw) of "FEAW'sand from water zone. Every zone used specific parameter to calculate water saturation (Sw) and used specific Sw equation for each kind of reservoir. After several logs were calculated, a table of interesting zone and mapping new interestingzone would be made. Finally, Original Oil in Place (OOIP) can be calculated.As a result of this research some interesting zones which have a potential to perforate were found. Every zone has a different petrophysic parameters. Resistivity of water (Rw) in those field ranges 1.655 - 1.806 and water saturation ranges 0.050 - 0.998. Beside that, cementation exponent adjusted is 2.4.