Inflow Performance Relationships for Damaged Wells Producing by Solution-Gas Drive

Abstract

The dimensionless inflow performance relationship (IPR) for solution-gas drive wells presented by Vogel* is very useful in well producibility calculations. Well rates at various pressure drawdowns can be predicted easily by use of either his chart or his equation (his Fig. 5 and Eq. 1). A second use of his relationship, to be illustrated later, is as a means of averaging results of several rate tests on a given well. Vogel investigated effects of wellbore damage on the shape of IPR curves. He states that the effect of skin, or damage, is to cause a straightening of the IPR curve. The reference curve he presents, however, (his Fig. 5) essentially applies to wells without damage during their early life. My purpose here is to present a companion chart that can be used for calculations involving damaged wells. The chart is useful in predicting stimulation that might be accomplished, under predicting stimulation that might be accomplished, under given drawdowns, if the wellbore damage is changed from one value to some other value. Consider the pressure-distance profile of the positively damaged well illustrated in Fig. 1. The flow positively damaged well illustrated in Fig. 1. The flow efficiency, FE, of the well-formation system is given by the relationship(1) Graphically, this amounts to the distance (p - p' wf) divided by the distance (p - p wf). For a well draining a closed cylindrical volume, flow efficiency can also be expressed as (2) where s is the dimensionless skin factor. FE also expresses the ratio of the well's flow rate with damage to the flow rate without damage. P. 1399