Published: 03/01/2011
Published: 03/01/2011
An operator active in the Haynesville Shale (Texas and Louisiana) wanted to reduce the number of days and trips required to drill the 6 3/4-in production interval, by drilling both the curve and lateral sections in one run. Previous bit designs were aimed at either the curve or the lateral, necessitating a trip to change out the bit and adjust the bend angle. Bits that target the curve section have strong build tendencies and predictable toolface control, but often deliver low ROP in the lateral. Conversely, bits for the lateral section are built for aggressive, fast ROP but increase the risk of improper build rates in the curve section. The use of two bits and extra trips meant higher field development costs.
Engineers needed to design a PDC bit that could be efficiently run on a positive displacement motor (PDM) with a lower bend angle while achieving the desired build rates (8° to 14°/100 ft), ensure good directional control, and deliver high ROP in the lateral. Long lateral drilling in shale plays presents additional challenges such as cuttings accumulation at the bottom of the well, which impedes access to fresh rock and results in low ROP, packed blades, nozzle plugging, and stick/slip.
Smith Bits field engineers, design engineers, and hydraulics experts designed a bit that would achieve the primary goal of drilling the entire production interval in one run. The team had access to several proprietary modeling and database tools, including
The operator provided valuable BHA data, mud properties, and offset run information for focusing the design. Close cooperation between the various groups resulted in new PDC bit technology, the Spear 6 ¾-in SDi611 drill bit, which provides a good balance between superior directional control and fast ROP.
The new 6 3/4-in SDi611 bit has been run on steerable PDMs with the following operating parameters:
Spear 6 3/4-in SDi611 shale-optimized steel-body PDC bit, together with a 2° fixed-bend steerable motor, drilled the 6,063 ft of curve and horizontal intervals in one run, setting a new Haynesville horizontal ROP record of 49.7 ft/h. Although there are a few faster lateral runs, no other bit had drilled the entire curve and lateral sections at that high rate. The bullet-shaped steel body and various other design features effectively combat buildup of cuttings in front of the bit and the resulting adverse effects.
Based on comparisons with two direct offset wells, the total drilling time was reduced by 124 h. The improved performance saved the operator USD 365,000 in rig-time and bit costs and shortened time to production, allowing more wells to be drilled in a given period.
Challenge: Drill 6 3/4-in curve and lateral sections of a Haynesville Shale well in one run, with good directional control and high ROP.
Solution: Run innovative, application-specific Spear shale-optimized steel-body PDC drill bit.
Results: Saved 124 h of rig time and USD 365,000 by drilling both intervals in one run, with record horizontal ROP.
