Abstract
To reach many of the world’s petroleum-rich formations, drilling must first penetrate challenging shale formations where wellbore instability frequently results in costly stuck pipe, lost circulation, non-productive time, and expensive sidetracks. One technology gaining traction through successful field usage is a wellbore stabilizing agent (WSA) to limit the invasion of drilling fluid and wellbore pressure into the formation. Using a WSA can assist in stabilizing shales, delivering trouble-free drilling, and reduce losses and non-productive time.
The drilling team was assigned a challenging well involving the Mutriba Formation, a shale-limestone formation notorious for stuck pipe and lost circulation. Focusing on wellbore stability and minimizing of the destabilizing nature of invasive drilling fluid and wellbore pressure, the team utilized a wellbore stabilizing agent to stop fluid invasion at the borehole wall. This barrier, or “shield”, minimize formation damage and mitigates fracture growth which can lead to destabilization of the wellbore.
Constant monitoring and additions of the wellbore stabilizing agent resulted in a thin, tight, flexible HTTP filter cake and wellbore stability while drilling this challenging formation. The entire section through the Mutriba Formation was drilled with 100% returns and later casing was run without problems. No adverse wellbore conditions were encountered while tripping or drilling, and no non-productive time was lost in stuck pipe or lost circulation events. When compared to the offset well, the successful well using the wellbore stabilizing agent came in 7 days ahead of schedule and with a cost savings of more than 21%for the Mutriba section.
Controlling wellbore instability, especially in shale and shale-composite formations, is a key element of successful drilling in many fields across the globe. Information on field-proven technologies, such as this wellbore stabilizing agent, is important to the continual improvement of drilling fluid to safely drill similar fields around the world.
