The Research On The Safe Water Injection Pressure Of Bohai Offshore Oil Field

The effect of water injection would be smaller if the bottomhole pressure is much higher or lower than formation fraction pressure.During the daily injection or profile,flooding and other productions,the production would be less when water injection pressure is lower than formation fraction pressure;while when water injection pressure is higher than formation fraction pressure,the bottomhole pressure would be higher than it,too.That would cause the formation of micro cracks and water flows along the cracks and in the end the casing would be damaged.In this article,with sufficient investigation of bottomhole pressure calculation method,empirical formulations and numerical simulation are used to study the injection pressure calculation.Refined management of wellhead injection pressure is easy to be realized.And the pressure is mainly related to formation fraction pressure,pressure-loss of string and choke.Models for pressure-loss calculation are established in case of different injection technics.Then based on theory of fluid mechanics,pressure-loss of string is got using the formulations.The flow through choke is seen as small orifice constant outflow,and the pressure-loss calculation formula of choke is got.A safe injection pressure calculation software is programmed in Visual Basic used for different injection technics,different layers and different injection rate.To verify the results of VB software,we use the software of Fluent to establish finite element models for 4 types of wells.And the pressure-loss of string and choke is got.Comparing the results from VB software and Fluent software,we conclude that the results of VB software is reliable.On the base of the knowledge about emergency plan's characteristics,formation procedure and norms,the emergency of casing damage is established,which is used to guide the emergency action.The research results provide theoretical foundation for wellhead safe injection pressure calculation and refined management and offer the guide for oilfield injection.