Optimize cement properties for reliable zonal isolation.
Published: 04/01/2003
Published: 04/01/2003
Comparing the 26-well 2001 drilling program in White River Dome field, Colorado, with the 2002 14-well program shows that coordinated well design significantly improves drilling performance. Less wellbore washout, improved cementing practices, and increased bit performance reduced costs from USD 77.54 per ft in 2001 to USD 69.56 per ft in 2002, resulting in a savings of USD 810,000 for the 2002 drilling program. Use of a wellbore stabilization additive, in conjunction with a 30% reduction in circulation rate, reduced hole enlargement by an average of 14% for the interval drilled. Consisting of a reactive potassium silicate solution, the additive reduces wellbore enlargement by precipitating out of solution onto the wellbore walls. This reduced average wellbore diameter for the interval from 10.3 in to 9.3 in. Cement volumes were reduced by 899 ft3 per well. Improving cementing practices using a lightweight cementing system along with a more effective lost circulation additive increased cementing success from 40% to 75%. The cementing improvements complemented the improvement in hole caliper and eliminated additional costs from two-stage cementing. Bit performance was improved from an average of 4.2 bits per well to 3.1 bits per well through use of a rate-of-penetration (ROP) additive in the drilling fluid. The ROP additive (a proprietary complex ester) enhanced performance when drilling bentonite stringers that had previously caused bit balling and loss of drilling rate with PDC bits.