This could be a shower curtain to buy off the shelf at a Target store, complete with floral patterns; it's not. It's a map of Lower Barnett shale HZ gas wells in Tarrant County, Texas, within the city limits of Fort Worth. The floral patterns are laterals from single well pads that extend out into a man-made lake in a very wealthy neighborhood south of downtown.

Early in this play wells cost $4-5MM to drill and complete and now cost $7-9MM per well, providing you can find a place to put one. They typically make 3 BCF each and produce 100-200 MCFPD, forever, with very low pressure. If you ever fly into DFW airport you can thousands and thousands of these gas wells in and around the airport.

So how in God's name does an operator drill these wells like the direction survey plot above without those wells banging into each other, rubbing on each other, cutting into other casing, etc. etc.?

If you look at the 3-D plot above, all the vertical sections of these wells go straight down before radiuses are built and the Lower Barnett formation is penetrated (penetration points/first take points) that comply with Texas rules for well spacing. That is a big bowl of pasta down there. How do they do that?

Magnetic ranging. Steel used in casing has a natural magnetic field around it. If I need to increase the magnetic values around multiple strings of casing stuffed into the ground in close proximity to each other, I can do that mechanically from the surface.

I can then put magnetometer tool (RWD, or ranging while drilling) in my measurement while drilling (MWD)/ bottom hole assembly (BHA) above my drill bit and measure magnetic intensity values from well bore to well bore, relative to my BHA. I can then create minimum standoff values and create azimuth angles (bearings) that allow me to steer thru that mess and avoid collisions. Piece of cake.

Above is a TRRC permit plat from one of these HZ wells drilled in Tarrant County. The surface locations are that jumbled up mess at the top of the plat and the correlative interval where radiuses merge is called a "twining widow." Once I steer my new well thru the twining window (intertwining?) without colliding with something, I am home free and clear to follow my azimuths to the lateral toe.

Magnetic ranging is also how my very famous engineer friend, John Wright, intersected the BP Macondo well in 2010 from his relief well location. He zeroed in on the magnetic field of the Macondo at 19,000 feet TVD and interested the exact well bore, at the shoe track, essentially, whereby he bottom-killed the well with cement plugs, etc. while Wild Well Control was doing the top kill from the surface.

Magnetic ranging is awesome.