High efficiency downloading technology for deepwater drilling conductor in the Equatorial Guinea

The setting of the deepwater surface drilling conductor is difficult in the Equatorial Guinea Sea area.The jetting drilling technology was studied based on the soil characteristics of this sea area so as to provide the guidance for the safe and efficient setting of deepwater drilling conductors.Taking Well S-X in the Equatorial Guinea Sea area as an example, soil characteristics of this sea area was analyzed and the applicability of the jet-injection installation of deepwater drilling conductor was studied.The most dangerous condition of the injection was analyzed, and the maximum load under this condition was calculated.Combined with the real-time bearing capacity of the Ø914.4 mm drilling conductor, the minimum driving depth of drilling conductor by jetting was recommended.The bit stick-out was calculated by investigating the casing program and bottom hole assembly (BHA) of deepwater wells in the Equatorial Guinea Sea area.The minimum displacement that can meet the demand of rock carrying capacity while satisfying setting time efficiency and bearing capacity recovery was calculated.The initial weight on bit (WOB) during the drilling of drilling conductor was calculated based on the characteristics of pipe string and soil.Post-drilling evaluation was carried out on the designed bit stick-out, injection displacement and driving depth based on the on-site construction record.It is shown that the jetting operation range of drilling conductor in S Block of the Equatorial Guinea Sea area is 0-246 m below the mud line.To set the drilling conductor in Well S-X by jetting, it is recommended to set the minimum driving depth at 91.5 m, the bit stick-out at 127.0-152.4 mm, the displacement at 63 L/s and the initial WOB at 755 kN.The post-drilling evaluation analysis shows that the lower injection displacement is one of the important reasons for the difficult setting of the drilling conductor.In conclusion, the successful jetting operation of Well S-X in the Equatorial Guinea Sea area demonstrates that the recommended values of the jetting operation parameters are highly accordant with the actual values.And the good application of field practice indicates that the commercial application of the efficient setting technology of deepwater drilling conductor has entered a mature stage in China.