Heera field is located 70kms south-west of Mumbai city and 140 kms south-east of Mumbai High at an average water depth of about 50m. The field was put on production in November ’84. The oil production is mainly from Bassein, Mukta (carbonates) and Panna (basal clastics) formations. The general dip of the field is towards west. The field produced under depletion drive for about six years till Sept. 90. By this time the reservoir pressure dropped to 1300psi from 2150psi and the field experienced sharp decline in production. Water flooding in Bassein formation started in September ’90. The production stabilized for some time and then again started declining with a sharp rise in water cut. Current average oil rate from the field is 55,892 bopd with water cut of 56% and GOR 145 v/v through 152 producing strings. The average water injection is 1,36,800 bwpd.

The present study aims to identify injection water breakthrough patterns in the producers of Bassein formation of Heera field. The study area is the upper part of mid-Heera field comprising of wells of platforms HD, HQ, HR and HA. The sudden rise in high water content could be due to the breakthrough of injection water in to the producers. Spider diagrams and contour maps were used to interpret the injection water breakthrough patterns in the study area.

Areal distribution pattern as indicated by contour maps of different ions in the study area suggest that there is more influx of injection water in the wells lying on the rising flank of the basin. In the down dip effect of injection water is less. Wells of HA and HD lying on the eastern side are more affected by influx of injection water than wells of platform HR and HQ.

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