The primary relief well is currently being drilled by the DD3, followed shortly by a back-up well being drilled by the sister-rig DD2. But, considering BP’s troubles in capping the well, how are they going to find and pierce, a 10″ pipe located 18,000 feet below the surface? Enter Vector Magnetics.
For what vector magnetics lacks in web design (their website, is terrible) they make up for in shear engineering know-how. Founded in 1985 and based out of Ithaca New York, they are inventors and developers of the electromagnetic downhole proximity measurement. These tools are basically metal detectors that attach behind the bit of a drill string.
So the plan works like this: The relief well is drilled parallel to the original well then, using directional drilling techniques, the drill bit is steered until it becomes perpendicularto the original well.
Then comes the difficult part. To assure they tap directly into the well, BP plans to overshoot the target, meaning they will aim to miss the well by as much as 50 feet and drill past its location. Once this happens the drill sting will be pulled back onto the rig and a magnetic sensor will be attached to the BHA (Bottom Hole Assembly). Then the drill string will be run again with the metal detector noting the point at which it passes the original well. With the precise location mapped the last section of the well will be re-drilled to directly intersect the original well, and a milling tool will be used to cut into the well’s steel lining.
Vector Magnetics gives us more information on the science behind their system:
The RMRS system has been used for over 200 successful intersections. RMRS is a robust and accurate system, giving precise target information at greater than 140 foot range.
A frequent application of the Rotating Magnet Ranging System is an intersection between a horizontal well and an existing well. The magnetic bit sub is located directly behind the drill bit and the receiver on wireline in the target well. Accurate position information can be acquired at more than 120 feet of lateral separation, allowing for significant trajectory correction prior to intersection.
Once the original well is pierced, heavyweight drilling fluid, known as “mud”, will be pumped down the relief well and into the original. The weight of this mud will prevent any oil or gas from surfacing and, in doing so, kill the well.