A Novel Installation Method for Deepwater Well Conductors
Presented at PECOM - Villahermosa, Mexico - April 8-10, 2014
Conductors for deepwater wells are traditionally installed from drilling rigs using connectors and multiple pieces of pipe. In this method, a subsea jet flushes out the soil and creates a cavity for the conductor to be installed. Jetting disturbs the soil and for this reason, it can increase the setup time before the conductor is ready for the drilling operations. In addition, the holding capacities of the conductors installed using this method are unknown because reconsolidation rates fluctuate widely in various soil types and water depths. The conductor is held in place by the rig while the soil reconsolidates (i.e. 6-30 hours rig time) and even so, many times the conductors have marginal holding capacities when the next phase of the well installation begins. Problems that sometimes can occur include not meeting the verticality tolerance requirements. Due to poor visibility and the difficulty of knowing how deep the jetting head is disturbing the soil during the jetting process, the final length of the installed conductor protruding from the seafloor (i.e. “stick up length”) is often very difficult to control with precision. Some installations require greater accuracy for these “as-installed” parameters than can be achieved using traditional methods.
One alternative installation method that has emerged since 2007 is driving the conductors using
a one-piece welded conductor
small installation asset (i.e. Anchor Handling Vessel = Lower cost vessel)
ocean going barge with a hydraulic shuttle launch system
subsea hydraulic hammer
This method has been utilized in three major projects in South America, all of which were executed successfully according to client specifications. In this presentation, we will describe the most recent successful project which was a conductor installation for well first phase of the Tension Leg Well-head Platform (TLWP, P-61) in Brazil with stringent performance requirements by the clients. We will present the installation methodology, summarize the obstacles and lessons learned during the application of this technology, and describe the final installed conditions of the conductors for this project. Both photos and video will be used to illustrate what happened during the operations and how the work was safely and effectively carried out.
Conclusions drawn in this presentation may include the following:
Well-suited applications for this technology are TLWPs or fixed unit installations due to the quantity of wells and the opportunity for batch setting
Driven conductors give geotechnical engineers on the project “as-installed” holding capacity for the conductor in real time
Precise positioning (i.e. x-, y- location) of the risers can be achieved using the driven pile method
Driving instead of jetting allows precise control of the final “as-installed” conductor height above the sea floor for drilling riser designs and affords better verticality control
Client can start to work on all subsea infrastructure as soon as the conductor installation phase is completed
Cost savings can be achieved using this method by taking the conductor installation off the critical path of the drilling rig and batch setting multiple conductors on a single mobilization.