In oil and gas wells, sand plugs and wax buildup can obstruct flow and create operational challenges.
Sand Plug: This happens when formation sand or proppant from fracturing operations settles in the wellbore, restricting flow. It often occurs in high-rate production wells, horizontal wells, or after shut-ins when fines settle. If severe, it can trap pressure and require coil tubing cleanout or other interventions.
Wax Buildup: Wax (paraffin) forms when crude oil cools down, causing solid deposits inside the tubing. It can completely block production if not managed. Operators use chemical treatments, hot oiling, or mechanical scraping to remove it.

What Happened in This Case?
They encountered 1000 psi of trapped pressure while tripping pipe. This suggests a partial blockage in the wellbore, likely from sand plug or wax buildup. The crew realized the issue and had to switch to coil tubing cleanout to remove the obstruction and restore normal well conditions. The situation caused concern because trapped pressure poses a safety risk, requiring careful handling to avoid kicks or well control incidents.