Production Enhancement Through Profile Modification (PM) of Injection Water Using Deep Penetrating Cross-Linked Polymer Gel in a Mature Carbonate Field in Offshore India - A Success Story

India's most gigantic oil field Mumbai High (MH) is an offshore mature carbonate field situated North West of Mumbai city in the Arabian sea of Western India. The field has a vast production history and is currently in mature stage of production with increasing water production. Several steps were taken to reduce the water cut and increase production for maximizing recovery from this mature carbonate field mainly driven by water injection. Most prominent reason for increasing water cut is presence of active high permeability conduits causing premature breakthrough of injection water. The early water breakthrough via matrix/dual porosity pathways from injectors is leading to water recycling between injectors and producers leading to unwanted high water production. Moreover most of these injectors are completed in multiple layers with very limited PLT/ILT data. To cater to this problem Profile Modification (PM) technology with deep penetrating polymer gel system was adopted on a large scale in a unique manner to improve the sweep efficiency and enhance production. This involved comprehensive analysis of performance of injectors and their nearby producers coupled with extensive laboratory studies to optimize the chemical formulation to come up with a tailored made chemical formulation best suited for the target reservoir. To ensure best results in terms of reducing the quantum of produced water, each job plan has been customized depending on reservoir parameters such as temperature, salinity, injectivity, injection history, depth of the target zone and permeability. Jobs were executed successfully in 31 injectors in a specific sequence targeting both the high permeable channels as well as the matrix/medium permeability zones so as to achieve uniform sweep across all layers. This approach resulted in substantial incremental oil gain and reduction in water cut in offset producers. This paper summarizes the candidate selection, chemical optimization studies, execution methodology, production response pre and post job and lessons learnt. This water management practice can be considered as one of the most efficient methods for addressing the problem of increasing water production from mature offshore carbonate fields under water injection in India and globally.