TABLE OF CONTENTS A typical gas well may have to flow against many flow restrictions in order for the produced gas to reach the surface separator. The gas must flow (1) through the reservoir rock matrix, (2) then through the perforations and possible gravel pack, (3) possibly through a bottomhole standing valve, (4) through the tubing, (5) possibly a subsurface safety valve, and (6) through the surface flowline and flowline choke to the separator. Each of these components will have a flow-dependent pressure loss. A change in any of the well restrictions will affect the well production rate. To determine overall well performance, all components of the well must be considered as a unit or total system.
One useful tool for analyzing well performance is Systems Nodal Analysis. Nodal Analysis divides the total well system into two subsystems at a specific location called the "nodal point." One subsystem considers the inflow from the reservoir, through possible pressure drop components, and to the nodal point. The other subsystem considers the outflow system from some pressure on the surface down to the nodal point. For each subsystem, the pressure at the nodal point is calculated and plotted as two separate, independent pressure-rate curves.
The curve from the reservoir to the nodal point is called the "inflow curve," and the curve from the separator down to the nodal point is called the "outflow curve." The intersection of the inflow and outflow curves is the predicted operating point where the flow rate and pressure from...
