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ABSTRACT: Residual Oil Determination by Doping Drilling Mud with MnNa2EDTA (Minas Field Case Study)

Poernomo, Bambang1 and James P. Logan2 , PT Caltex Pacific Indonesia, Pekanbaru - Riau , Minas, Indonesia 

In Minas field, the residual oil to waterflood is a critical parameter for reservoir characterization and planning secondary and tertiary recovery projects. There are a number of methods for calculating the residual oil saturation to water flood (Sorw) by using well logs and core data. Examples are: log-inject log, calculating Sorw from C/O logs and dielectric logs, determining Sorw from measured porosity and resistivity logs, interpreting diffusion response from magnetic resonance tools, and laboratory evaluation of core floods. The results of the log derived techniques have not always agreed with results obtained from the Sorw measurements made under laboratory conditions.

As is often the case with oil field algorithms, there is some uncertainty with the parameters selected, and the utilization of these parameters across a range of potentially variant geologic, and petrophysical facies. In order to improve our confidence in these measurements and lower uncertainty in Sorw many of these techniques have been applied in Minas field. Recently, a direct measure of the Sorw in the swept zone was made by doping the mud system with the paramagnetic compound MnNa2EDTA and then running NMR logs. The MnNa2EDTA was chosen as an inhibiting agent due to the presence of clay minerals. The inhibiting agent is soluable in water but not soluable in oil which allows for a direct measurement of remaining oil. The result was compared to other more conventional methods for obtaining Sorw with data from the same well set.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia