Desoto Guy, Yes they drilled down to 15,158 '. Close to 3 MILES deep! They actually drilled vertically down to around 10,500'-11,000'. The rest is the lateral (the horizontal) leg. They drill down this far because this is where the Haynesville Shale is. The fracs are normally on the lateral only for a HS well. That is one of the main reasons HS wells typically produce so well. The stimulated (fractured) area is much longer than a vertical well. Hope this helps.
GOI, O.K. here's a stab, but bear in mind I'm not in the E&P side of the business. Hopefully Les B can clear it up further if needed. The first info is when they spud the well. (Started drilling.) They set 10 3/4" casing to 1870'. Not sure what 735 SX is. The rest of the info pertains to the type and testing of the BOP. Blow Out (Off?) Preventer. BOP's keep the gas and pressure under control when working on the well bore. HS wells tend to produce at much higher pressures than vertical wells do.