Publications

Hydrocarbon identification in oil and gas fields located in Mahakam area is challenging due to varying formation water salinity both vertically as well as laterally. In the same field, the vertical variation of formation water salinity is much wider than lateral variation, which is in the range of 1 to 35 kppm. The water salinity value directly affects the formation resistivity measurement, the lower salinity resulting in higher resistivity values. Hydrocarbon identification is commonly performed by using single resistivity cut-off. If formation resistivity is higher than cut-off, it is indicative of a hydrocarbon-bearing zone. This simple method works well in a field with low variation of formation water salinity, but in the fields in Mahakam area this method results in hydrocarbon misidentification due to the wide range of formation water salinity. For proper fluid identification, a high number of wireline fluid analysis tools per well is routinely run in Mahakam fields. A new interpretation technique, referred to as Auto Fluid, has been developed, the technique of which is based on the evaluation of all past fluid analyses results of all existing wells in order to get more precise fluid identification, and with the ultimate aim to optimize the number of fluid analysis points to be acquired in new wells. Fluid interpretation is generated automatically by applying a resistivity baseline curve varying with depth. The method has been blindly-tested in a number of recently drilled wells and the results are matching with Fluid analysis acquisition and perforation results. This paper details the method of this technique and its application in Mahakam fields, East Kalimantan, and further provides a new alternative powerful tool to be applied in mature fields in other areas outside Mahakam.