Trapped Gas in Horizontal Wells: What You Need to Know
In horizontal wells, gas can sometimes become trapped in pockets within the wellbore. Due to buoyancy, gas tends to rise and gather on the high side of the hole when circulation slows or stops. This gas can remain in these pockets, such as washouts, when circulation resumes at a slow rate.
In wells that are deviated at more than 90 degrees, gas might even migrate toward the bottom (toe) of the well. Unfortunately, these gas pockets can be difficult to remove when circulating at low rates, and they may only become dislodged later during drilling when pump rates resume to normal.
To avoid these problems, it’s often recommended to use the Driller’s Method for well control in high-angle or extended-reach wells. This method involves starting the first circulation at a kill rate close to the normal drilling rate. This helps dislodge the trapped gas into the vertical section, preventing it from becoming an issue later on. By circulating at a higher rate initially, you can ensure that all the gas is safely evacuated.
For more detailed information on trapped gas in horizontal wells,see my Well Control Manual V2.6 at: https://learn-well-control.com/product/well-control-manual-by-edwin-ritchie/