Depletion Drive Reservoirs

Introduction

Often called “solution gas drive“ or “internal gas drive”.

Oil expansion for when P > Pb, and oil/gas expansion for P < Pb.

Initial reservoir pressure is greater than bubble point (refer to Undersaturated vs Saturated )

Basic Characteristics

1. Rapid pressure decline

2. Water-free oil production. The interstitial or irreducible water saturation (Sw or Swirr) will not be produced as it is already at minimum water saturation

3. Rapidly increasing GOR after bubble point is reached

4. Low ultimate recovery.

   1. Usually the least efficient method of recovery (5 to 25%?)

   2. Relative permeability and viscosity play an important role in recovery

References:

• T. A. Blasingame, PETE 663: Introduction to Reservoir Engineering, Texas A&M Course Notes, 2014

• PETE 2320: Reservoir Engineering, Northern Alberta Institute of Technology (NAIT) Course Notes, 2019.