7.10: Summary and Final Tasks

Summary

In this lesson, we discussed five key design aspects for oil and gas wells considered by production engineers:

• well orientation
• well completion
• tubing size
• well stimulation
• artificial lift

In addition, we discussed two common problems with well production: sand production from unconsolidated reservoir formations and production of unwanted fluids. The sources of unwanted fluid production are:

• lateral fluid migration through the reservoir
• downward coning of gas from a primary or secondary gas cap or upward coning of water from a bottom-water reservoir
• injection from offset injection wells

We also saw that we could mitigate these two problems (sand production and unwanted fluid production) with proper well completions. For sand production, the most commonly used completion involves some form of a gravel pack where the gravel acts as a filter against the sand production. For unwanted fluid production, we build zonal isolation into our well completion designs. For these wells, we can use cased and perforated completions, along with systems of packers, bridge plugs, and sliding sleeves to provide zonal isolation to prevent production of unwanted fluids.

For determining the proper tubing size to use in a well, we plotted the Inflow Performance Relationship and the Tubing Performance Curve on the same graph. The intersection of these curves represents the operating point of the well. By testing multiple tubing strings, we can evaluate the impact of tubing size on the operating point of the well and determine those tubing strings that meet our economic hurdles.

Finally, we discussed well stimulation and artificial lift. We saw that the same analysis method could be used for these aspects of the well design. When evaluating well stimulation, we modified the Inflow Performance Relationship with simple skin models to evaluate the impact on the operating point; while for artificial lift, we saw that pump or gas lift devices had to be incorporated into the well hydraulics model to generate the appropriate Tubing Performance Curves for evaluation and optimization in our analyses.

Final Tasks