Abstract

Re-evaluation of the Sangatta Field has been undertaken in order to learn if bypassed hydrocarbons remain. Drilling of new wells in this field has been severely restricted and in some cases prohibited since this field is located in the Kutei Forest National Park. New production from the field will almost entirely depend on increased production from reevaluation and workover of existing wells. Previous studies have located all the easily detectable hydrocarbons, leaving only thin zones and intervals with resistivities less than 10 ohms as possible targets. The reevaluation was conducted to evaluate and identify additional hydrocarbon zones within this mature field. These new zones would then be tested in order to confirm the analysis.

Studies of this type are composed of numerous steps and are carried out in the following manner:

All pertinent data is gathered and stored in a digital format.

Water analysis of all producing zones and locations is used to map the subsurface water salinities.

Whole cores, sidewall cores and cuttings are analyzed using XRD, SEM and petrographic techniques. The results of these measurements are used to control the petrophysical analysis.

Formation evaluation of all wells is performed utilizing the ELAN^# program.

All these results and other pertinent data are stored in a multi-well data base for easy access and management.

The initial results of this study established the following information. Water salinities vary both vertically and horizontally in a range of 2,000-18,000 ppm. These salinities have been mapped across the field for use in further studies and future wells. Core analysis gave a consistent elemental analysis to be used in the formation analysis. Constrained by core analysis, formation evaluation produced a consistent lithology and showed variations in the Cementation Factor m from zone to zone with a range from 1.6 to 2.2. Based on the new water saturations calculated during this study new zones in seven wells were selected for testing. Production results have proved the presence of additional reserves.