1.0 Introduction ADMA-OPCO is the pioneering offshore Oil and Gas Producer in Abu Dhabi, UAE dating back to the 1950s. ADMA-OPCO operates more than 1500 km of sub sea pipeline network, built over the years as part of the progressive development in Umm Shaif and Zakum fields. ADMA-OPCO vision is to work effectively as one integrated team to produce hydrocarbons from offshore areas aspiring to excellence in all aspects of the business. This paper identifies ADMA-OPCO current key challenges being faced in and around existing developments, "Brownfields" considering the additional challenges imposed by the extensively busy oil & gas market. The paper is aiming to conclude and recommend best practices, key success parameters and lessons learnt which shall provide significant values to future projects of same nature. Conclusions and recommendations were extracted through professional coverage of ADMA-OPCO Water Injection Pipelines Replacement Projects started in year 2000 and are anticipated to be complete by 2015 in a phased manner. It is worth mentioning that all executed phases have been completed with great success, ahead of schedule and below allocated budget. 2.0 ADMA-OPCO Replacement Strategy 2.1 Main Objective of the Replacement Strategy Replacement of existing water injection pipeline systems in Zakum and Umm Shaif offshore fields to enhance the capacity of the current system and ensure un-interrupted safe supply of water injection.