Performance of Water Injection Wells - Chestnut Field

Water injectors are critical to the long-term success and reserves recovery of hydrocarbons production and reservoir management. Injectors are also critical to the pressure support of the reservoir that allows production and mechanical integrity of the rock. Lack of injection does, in many cases, lead to impaired production and changes in petro-physical properties at the wellbore and deep into the reservoir. Limited references are found in the literature in terms of design and performance management of water injectors. Our work describes in detail the design and performance processes for two (2) injection wells (wells 12 & 17) in the Chestnut field, located in block 22/2a in the UKCS of the North Sea. Producing from a shallow sandstone reservoir, the field is exploited using two (2) producers and two (2) injectors. All wells are subsea and an active sand and pore pressure management program has been in place for 6 years. The design rationale and parameters are presented and the results obtained discussed. Well performance is then analysed in terms of pressure support, injectivity and operational problems that lead to injectivity impairment and one well failure. The methodology for evaluation of reservoir performance is described; comparison between the typical analytical tools such as the Hall or the Impedance Methods is discussed including the results obtained. A performance comparison based on real-time data from the wells, to identify and predict events such as injectivity impairment, the need for intervention or remedial action, is presented.