The PFA service is a coiled-tubing deployed, single-trip, rigless intervention service that requires no isolation packers. Time and costs are lower than conventional workovers. The service treats the existing proppant in the near-wellbore region with a coating. After coating the grains, a consolidating agent forms a tacky film that creates bonds between grains that cure with time and temperature. Minimal conductivity loss is experienced. Curing of this one-component resin takes place slowly, which aids placement. The PFA service is implemented with pulsing technology, either fluidic oscillation or low-frequency pulsing, to enhance fluid flow and ensure penetration into the proppant pack.

The five wells in the 2006 program that XTO described had been requiring frequent wellbore cleanouts, costing $15,000 or more per cleanout. PFA treatments were performed in early 2006. Proppant flowback with associated production declines and down time has not been a problem since. Projected value added from reduced workover-cleanout expense and/or increased production varied from $210,000 to $400,000 per well per year.

The complex geology, dipping formation beds and fractured formations of the western Piceance Basin leads to "crooked hole" and "lost circulation" problems when drilling the surface hole. Surface casing is typically targeted at about 3,100 depth. Conventional drilling uses mud motors and low weight on bit. After drilling, hole conditions that can prevent getting surface casing to the desired depth can be encountered. Poor hole conditions also lead to poor cement jobs, requiring remedial workovers to achieve the cement return required by the Bureau of Land Management.

Sandridge Energy selected Weatherford's DwC (Drilling with Casing) service, combined with stage cementing of the surface casing. Results for a seven-well program were reported in this article, plus extended detail on some of the procedures involved. Bottom-line overall results were impressive compared to data evaluated for five wells that had been conventionally drilled. Documented improvements include:

• Reduced average overall drilling time by 2.72 days per well (21%),

• Reduced average surface-hole nonproductive time by three days per well (47%),

• Significantly reduced fluid loss with documented savings of $40,000 for one well,

• Reached desired surface casing depth in ALL WELLS,

• Achieved cement returns in ALL WELLS, and

• Reduced average deviation by 44%.

Coiled tubing (CT) drilling has been common in Canada, particularly at shallower depths. That experience is moving south to the U.S. Xtreme Coil Drilling Corp., with its Coil Over Top Drive rig, has been a driving force in the U.S. growth. Experience by multiple operators in multiple basins is building. Much of that experience is in deeper wells, which are made possible with Xtreme's rigs and the larger 3-1/2-inch CT developed for them by Tenaris Coiled Tubes. Further advancements may lead to even larger CT, which would further increase depths.

Following are some of the recent records with Xtreme rigs:

• Record depth: drilling for Encana in DJ Basin's Wattenberg field by XTC 200DT rig using 3-1/2-inch CT to depth of 8,125 ft

• Record drilling time: drilling for Anadarko in DJ Basin's Wattenberg Field by XTC 200DT rig—3.4 days spud to total depth; move to rig release 4.8 days

• Longest S Curve well: drilling for Encana in Piceance Basin reaching length of roughly 6,000 ft

Most recently, Xtreme delivered its first XTC 400 rig, operating for Encana in the Piceance Basin. This is a hybrid CT plus conventional drilling rig that has the same capabilities as a fit-for-purpose 14,000 ft conventional rig. CT can drill to near 10,000 feet, then one can use jointed drillpipe to approach 14,000.

Xtreme plans continued rapid growth, anticipating a fleet of 18 CT rigs by early 2008 with most scheduled for U.S. delivery.