The Bombay High field is a giant offshore oil field in India. The field which is on oil production from 1976, contains two major reservoirs and is divided into Bombay High North and Bombay High South. L-III limestone is the main reservoir and produces oil from the entire field and L-II limestone produces oil from Bombay High North.
The heterogeneous nature of the L-III reservoir complicates the recovery process. The current development has resulted in over injection in certain regions/zones and under injection in other areas. Non-uniform movement of water, with considerable amount of oil left undrained is observed throughout the field. Poor primary cementation in certain wells further aggravates the problems due to the pre-mature break-through of water and gas.
A large proportion of the work-over jobs are done to contain the cusping of gas, cycling of excessive water and to repair the channels behind the casing. Conventional cement squeeze jobs have yielded moderate results and few gel treatments in production wells have not been successful.
The most successful results in recent times, in increasing oil production from sub-optimal producers, have come from Long Drift Side Track (LDST). In this operation, the well is sidetracked to some distance away from the original wellbore, to a relatively undrained area and recompleted with special attention on cementing operation. The present success ratio is high. LDST amounts to a new well in a relatively undrained area by utilizing the existing slot. This has been found to be a viable option for well production optimization. However, in future, as in the past, the decision on side-track needs to be made on well by well basis only.