I got a question about how an anticline gas cap can create the abnormal pressure. The anticline with gas cap can be the potential high pressurized zone. Because of reservoir connectivity between fluid underneath gas and gas reservoir, it can generate abnormal pressure. This example below demonstrates you how this situation could happen.
In some situation, where you drill with mud weight that is very close to balance condition (near formation pressure) and you don’t have much room to weight up due to fracture gradient limitation, from the well control perspective, you may need to drill one stand, then circulate bottom up and perform flow check. If everything is static, you can go ahead and drilling. Moreover, you need to look at the peak gas after going back to drill because it indicates how well of mud weight is. If you don’t see any gas peak, it means that your mud weight at the static condition is good. However, if you see any gas peak while drilling but it does not come from formations that you are drilling, this situation indicates that you don’t have or just enough mud weight to control the well in the static condition. You can check where the gas coming from by using a lag stroke calculation.
Trip margin is an increment of drilling mud density to provide overbalance so as to compensate the swabbing effect while pulling out of hole.
You can quickly calculate how much trip margin required by this following simple equation.
Trip Margin = Mud Yield Point ÷ [11.7 x (Hole diameter – Drill pipe diameter)]
You know how the maximum allowable shut in casing pressure (MASICP) from the leak off test data and your current mud weight in the well. Moreover, you can use the MASICP to determine the maximum influx height that you can be able to control in the well control situation.
The following formula shows how to determine the figure:
Influx Height = MASICP ÷ (current mud gradient – influx gradient)
The steps , called “3S” shut-in procedures, demonstrate how to properly shut the well in while drilling.
You can learn about it via this VDO
If you cannot see, please follow this link http://www.youtube.com/watch?v=FFNyG30xbqI
