The number of subsea wells has increased steadily and by the end of 2012 exceeded 5,500 (Infield 2013). These wells pose a number of challenges including generally lower recovery factors compared to wells with surface access. The high operating rates of rigs have had a natural damper on the incentive to increase recovery rates, as the balance between cost and revenue has been unfavorable—even with increasing oil and gas prices. However, this has also spurred the drive to develop alternative methods to enhance recovery and cope with the challenges of maturing fields and exploration under more difficult circumstances.
Adopting frequent lightweight well intervention has proven crucial for subsea operators to realize the potential of 50% oil recovery. Such operations are becoming more common, but there are increasing challenges and demands as development moves toward deeper waters. To reduce overall risks and use the natural resources more effectively, new technology and improved operational efficiency are required. The ability to carry out frequent, scheduled interventions as opposed to remedial interventions is fundamental to raising recovery rates.
Lightweight and riserless well intervention has proven its potential for driving improvement in recovery rates. The ability to substitute rigs with smaller, dynamically positioned light well intervention vessels has a major impact on cost and scheduling. Electric line (e-line) Riserless Light Well Intervention (RLWI) has demonstrated its value and the fact that it is an inherently safer method for intervening on subsea wells compared to conventional, heavier methods using a riser.
This paper gives a detailed account of the opportunities to improve recovery rates in subsea wells by having access enabled with this lighter, more efficient, and ultimately more productive intervention method. Several case histories and examples will be shown.