A novel expandable drilling conductor is designed to enhance the bearing capacity and stability of subsea oil and gas wellheads in deep-water. The basic structure is the annular expandable materials installed on the surface of the conductor, which changes the interaction between cylinder foundation and surrounding soil, and the annular expandable materials are connected with the conductor to form a similar variable section rack structure, which increases the occlusive effect between the conductor and the stratum. This study proposes the method of combining theoretical models with laboratory experiment and field test for analysis. A new model of expandable conductor and soil strata is presented. Results show that the novel expandable conductor can significantly increase the vertical bearing capacity of the foundation, the end of the annular material area (the thickness of the material), the length of the annular material, and the distance of ring material are the main factors affecting the vertical flexural bearing capacity, and the distance and the thickness of the material and the shear strength of soil are closely related. This kind of variable section pipe can be used as a new type of pile foundation structure to effectively increase the stability of the foundation.
Structural casing jetting operations have become commonplace in deep-water environments. Having originated in the Gulf of Mexico (GOM), the structural casing is now jetted in most deep-water basins in the world (Akers, 2008). Very little literature has been published regarding jetting practices. The lack of published literature, combined with the complex mechanics and hydraulics of the process and the lack of detailed soil data at most locations, results in an operation that is heavily dependent on the experience and expertise of the rig-site team.
The deep-water drilling conductor is an important bearing device, and the bearing capacity generated between conductor and soil is used to carry the wet weight of wellhead, mud mat, cam-actuated drill-ahead (CADA), etc. There are usually three methods of conductor installation: jetting, drilling, and hammering (Yang et al., 2010; Pereira, M. F. et al., 2013; Roy et al., 2018). In recent years, the conductor anchor node (CAN) has been developed and successfully applied as an emerging technology (Sivertsen et al., 2011; Kan et al., 2018). In contrast, the jetting method is most mature and has been widely used in the Gulf of Mexico (GOM), West Africa, Southeast Asia, and South China Sea (Jeanjean, 2002; Mackenzie et al., 2012; Prasertamporn, 2016; Wei et al.,2019). In this paper, we focus on the jetting method.
