A new technique is presented which aids in maximizing water injection rates in wells recently converted to injection, thereby accelerating offset oil production response. This method is applicable to waterflood operations where injection wells are surface pressure controlled and where bottom-hole injection just below formation parting pressure (FPP) is desired.
Two plotting methods are shown to be instrumental in monitoring the acceleration of fill-up and average reservoir pressure growth in an actual field case. One is the Hall method1 : plotting a function of bottom-hole injection pressure versus cumulative water injection, and the other was Introduced by Hearn2 : plotting the inverse injec-tivity index versus cumulative water injection.
After initiating injection into several converted wells at pressure limits well below the average offset parting pressures, periodic surface pressure increases were made at each well over a period of several months. Monitoring the Hall and Hearn plots as the pressure and rates increased rendered qualitative interpretations of whether the rates were being maintained below FPP. Accelerated reservoir pressure growth was achieved which resulted in earlier than expected offset oil response.
Application of these plots also reduce, and sometimes eliminate, the need to perform periodic step-rate tests designed to determine FPP during the injection start-up period, thereby significantly reducing operating costs.