Production of oil & gas has very big influence to mankind civilization but the excessive generation of produced water in mature fields as a by-product may have bad impact to environment. Pollution of surface water supplies or fresh water aquifers has become a serious concern in recent years. It is therefore an obligation upon the industry to handle the produced water and disposed it responsibly. This concern has focused attention on produced water re-injection into underground formation (whether it is virgin or depleted reservoir) as a promising method to discharge oilfield water without polluting potable water supplies.
As refer to regulatory guidelines, injection well for produced water disposal must be operated so that the pressure during injection does not initiate new fractures or propagate existing fractures in the confining zone adjacent to the sources of drinking water, which could damage the receiving layer or cap rock. In order to achieve that purpose, the paper describes evaluations and planning on operational aspects regarding daily activity/practical operation, which are essential to the successful of water injection project. Operational aspect especially includes working pressure along the injection system, estimated formation fluid pressure as function of cumulative injected water, estimated fracture pressure and its relation to proposed injection rate. Operational window for injection must be developed to determine the range of allowable injection pressure and its relationship with the proposed injection rate.
The paper also describe a method to determine the life time of each proposed injection well which is the compilation from the result of operational design analysis and reservoir pressure builds up data from simulation results. This study is very useful to make injection programs and scenarios to extent the injection lifetime (e.g. scenario to add new injector wells).