The limitations of the bi-center tools are unpredictable directional control behavior, high fluctuating torque, irregular hole size, limited life and ROP in medium to hard formations and inability to drill the cement inside the casing. For these reasons both under-reamer and bi-center tools discourage the wide application of RCCP.

The EWD & ES tools were designed to overcome the limitations of the under-reamer and the bi-center tools with the belief that their application will encourage the wider use of RCCP and hence reduce the overall well costs.

RCCP ADVANTAGES 

Figure 2 is a scale drawing comparing RCCP to CCP for a 16,000 ft well in 3000 ft water depth in Green Canyon. We used a computer spreadsheet to calculate volumes of hole, costs of mud, cement, and casing for both RCCP and CCP well designs. Following is a summary of the savings in million of dollars:

RCCP CCP Savings
Casing 1.02 1.76 0.74
Mud 0.90 1.30 0.40
Cuttings Handling 0.02 0.03 0.10
Cement 0.06 0.08 0.20
Drl.& Cemt. Tools 1.10 1.20 0.10
Rig cost 6.00 7.00 1.00
Total Savings $2.44

These figures assume minor mud losses and two sections of the well drilled with synthetic or oil based mud.

Other important benefits of RCCP are:

  • One 18 5/8" sub sea stack and riser will be sufficient for the RCCP wells.

  • The use of  9 5/8" liner with tie back permits the 65/8" drill pipe to be used to drill to the production casing point. A 6 5/8" x 4 1/2" tapered drilling string can be used for drilling the last section of the RCCP well instead of a 6 5/8" x 3 1/2" which must be used for CCP well.

  • A 7 5/8"  instead of 7" production liner.