Once the attributes of the rock units intersected by the well are figured out using one of the interpretation methods we discussed, geologists and engineers can move on to the most important phase of formation evaluation – the determination of a well’s production potential.
Most important to the production potential of a well is the presence of economically recoverable hydrocarbons. Well logging methods that tell us something about the hydrocarbon saturation are valuable. Mud logging results showing oil and gas in rock cuttings are even more valuable. Perhaps the most valuable of all are drill stem tests (DST), as previously discussed. These DSTs show not only that the hydrocarbons are present but that they are under pressure and able to flow through the formation rocks and into the well.
In addition to making sure the well will produce hydrocarbons, formation evaluation can help operators predict areas that might present problems during production. These areas include poorly consolidated sandstones that might produce sand or be prone to washout and also zones that might be prone to collapsed casing issues.
Finally, formation evaluation provides operators a better understanding of the pressure requirements for stimulation treatments, how rocks will respond to these treatments, and what types of oil and gas processing equipment will be required on the surface to meet the specifications of the sales contract.
Based on all the conclusions we just discussed, operators will perform an economic analysis to decide whether the well should be plugged and abandoned or completed and prepared for production.
Images: “Lower 48 States Shale Plays” by U.S. Energy Information Administration