The objective of this paper is to demonstrate the success of drilling and completing two subsea wells in the Mediterranean Sea including the first run in Eni of horizontal subsea X-Tree using a jack-up rig safely instead of Semi-Submersible rig without the need to reposition the rig during subsea XTree deployment which resulted in a significant high cost saving that affects positively the overall project economics.
All operational data including soil data, shallow gas hazard data, water depth limitation analysis, heavy lifting operations analysis and subsea equipment (ROV, High pressure riser and subsea wellhead & X-tree) placement on-board of the jack-up rig has been collected and studied in order to evaluate any possible associated operational risk and set in place the relevant mitigation plans to perform the drilling, completion and subsea horizontal X-Tree (72 tons) running operations safely, which resulted in achieving an estimated cost saving of 28 M$ in addition to around 6 days of gas production anticipation.
Such cost-effective alternative solution of performing subsea operations by jack-up rig is already suitable for acceptable water depth ranging from 80m to 100m due to jack-up leg limitations and has already been put in place in Egypt Mediterranean Sea, where it gives reliable results and performance that will affect the overall vision of the shallow water subsea operations. The main challenges in the project-planning and implementation phases are:
‐ Shallow gas hazard analysis
‐ Water depth limitation analysis for jack-up
‐ Soil data for punch-thru analysis
‐ High pressure riser on top of the BOP
‐ ROV placement on the rig
‐ X-Tree deployment including dedicated heavy lifting procedures by the jack-up
‐ Rig crew subsea operations background
‐ Weather conditions
All the above challenges and relevant risks had been evaluated and put in place a consolidated risks mitigation plan which allowed proper safe operations implementation to achieve all targets in terms of:
‐ Operational safety procedures
‐ Time and cost saving
The two wells have been done back to back and all the lessons learned in the first well has been taken into account in the planning and implementation of the second well.
In addition to all of this, the use of JU rig to perform such activities helped in anticipating the gas production by 6 days, which consequently will affect the overall production operation costs. The increasing need for operational efficiency and cost reduction can be compromised by finding an alternative solution to perform subsea drilling and completion operations using a J/U rig instead of Submersible rig in shallow water depth range (80m-100m). This paper described well the application and the benefits of such alternative solution to be used as reference successful case by other key players in the O&G market.
