Abstract
Oil viscosities of about 2 cP and above (under downhole conditions) are common and often exhibit poor end-point mobility ratios when displaced by water in fields under waterflood or with active aquifers. This causes a triple hit on the recovery factor:
Poor displacement efficiency
Poor areal sweep
Poor vertical sweep
This is made worse by reservoir heterogeneity.
The commonly used concepts of productivity index (PI) and injectivity index (II) are not particularly useful when the mobility ratio is high since they require the use of a nominal drainage radius, whereas a two-fluid system with a moving fluid is more appropriate.
The novel concept of the injectivity productivity index (IPI) has been developed to consider a pair of wells comprising an injector and producer, and replaces the use of II and PI. The IPI method helps to quantify waterflood issues in the presence of poor mobility.
This paper will cover three main areas:
The simple background theory of IPI.
The consequences of IPI for breakthrough, sweep, and even sanding.
The implication of IPI for an example waterflood field, Casabe, which has these challenges and required a new understanding of the waterflood.
