Schlumberger

Case Study: Optimized Bit Selection in Wapiti Field Saves 120 h and USD 360,000

Challenge: Drill an 8 3/4-in vertical interval of 2,196 m in length interbedded with layers of high and low compressive strength formations, with only two bit runs.

Solution: Run two different 8 3/4-in bits: a FH TCI tungsten carbide insert drill bit (model FHi18 447X) and an ARCS alternating radius curvature stabilized PDC drill bit with ONYX premium PDC cutters (model MASi513).

Result: The entire interval was drilled in two runs, saving 120 h of rig time and USD 360,000.

Drilling performance driving a reduction in operating costs

In the course of drilling a well in Alberta, Canada’s Wapiti field, an operator experienced unsatisfactory bit performance. The well had a horizontal profile and was drilled in the lower Nikanassin formation, which is composed of sandstone and grey shale with carbonaceous shales and small carbonaceous streaks. Additionally, the section drilled by the operator was interbedded and consisted of many lithological layers, with high and low compressive strengths. For a second well, the operator was scheduled to drill an 8 3/4-in interval of a well from surface casing to kickoff point (KOP), with planned depth of 2,196 m, in this same area. Completing this new section meant drilling through conglomerate and coarse grained sandstone, which are composed of chert and quartzite cemented with silica.

To avoid the expense of numerous bit runs—experienced in the most recent effort—the operator sought to reduce costs by using information collected from previous wells to optimize bit runs in the Wapiti field. The operator worked with the Smith Bits’ advanced services engineering (ASE) group and the drilling crew to investigate opportunities that would improve drilling. Their investigation included researching DRS drilling records system to collect offset information from the Wapiti field.

Optimized selection of bits and drilling parameters

After analysis, using IDEAS integrated drillbit design platform, Smith Bits’ Advanced Services Engineering (ASE) group recommended that the operator use two different 8 3/4-in bits: a FH TCI tungsten carbide insert drill bit (model FHi18 447X) to drill the upper part of the vertical section and an alternating radius curvature stabilized (ARCS) PDC drill bit with ONYX premium PDC cutters (model MASi513) to drill the lower part of the section. In addition to bit selection, the engineering group created a drilling parameter roadmap using DBOS drill bit optimization system. With the target section being extremely interbedded with many layers of varying formation strengths, optimized drilling parameters were essential to maximizing bit performance To ensure this, the drilling engineer, superintendent, well supervisor, and the ASE group identified the most effective drilling parameters, which included adjustments to weight on bit (WOB) and rpm throughout the section.

USD 360,000 and 120 h saved

After the FHi18 447X roller cone bit drilled the upper interval of the section, a planned bit trip was made to pick up the MASi513 PDC bit to complete the lower interval of the section. From a depth of 1,437 m, the 8 3/4-in PDC drilled 1,374 m to a total depth of 2,811 m. That resulted in completion of the entire 2,196-m, vertical interval in 108.75 hours at a rate of 12.6 m/h. The one-run performance of the MASi513 PDC bit eliminated the need for a typical third run. By achieving the total depth in two runs, the operator saved USD 360,000 and an estimated 120 h of rig time.


Download: Optimized Bit Selection in Wapiti Field Saves 120 h and USD 360,000 (0.65 MB PDF)

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