IADC’s new Dual Gradient Drilling (DGD) Subcommittee will work to develop best practices and strive to build interest in the technology, said subcommittee chairman John Cohen of AGR Subsea. The subcommittee, organized under the auspices of the IADC Underbalanced Operations & Managed Pressure Committee, also seeks to improve understanding of various DGD methods and their limitations and benefits, and serve as a forum for information exchange.
“As we expand development into deeper water, DGD will become a very important technology,” Mr Cohen said. “The DGD Subcommittee, like its parent, the IADC UBO & MPD Committee, will first work to facilitate the safe exploitation of hydrocarbons. Unlike the UBO & MPD Committee, the new subcommittee will focus on the offshore environment.”
Kristin Falk, Ocean Riser Systems, is the group’s vice chair and agrees that improved safety is an important benefit of dual-gradient drilling. “DG systems are particularly beneficial for several reasons related to well control and well integrity,” she said.
In particular, Ms Falk added, DG systems improve safety margins while drilling, kick and loss detection, and kick margins. Further, DG systems, she said, are more likely to achieve a riser margin. Further, it is possible to circulate out minor influxes without closing a BOP element. Other benefits include improved cementing, and barrier and well integrity improvements by using fewer common barrier elements. Finally, she said, DG systems are partially or even completely self-regulating regarding inflow and kicks.
“Drilling with heavier mud weights requires that new well control procedures and equipment for managing hydrocarbon influxes be developed,” she added. “Implementing new guidelines for this is one of the long-term goals of the subcommittee.”
The 2011 IADC Dual Gradient Drilling Workshop, 5 May at the Omni Houston Westside Hotel, will examine the types, challenges and benefits of DGD, emphasizing well control and testing the concept.
“Application of DGD,” Mr Cohen said, “will allow drilling of wells that currently are undrillable, deepening of casing setting points, elimination of liners and close fits between liners and casings, faster kick detection and lower well costs.”
DGD is a form of managed pressure drilling that is particularly suitable to floating drilling rigs. Using two fluids of different densities, DGD matches the well pressure gradient to the natural pore and fracture pressure gradients of the formations. This is increasingly difficult in conventional drilling as water and well depth increase.
Applications include high pressure combined with narrow drilling windows in deep and medium-deep water, high equivalent circulation density combined with narrow drilling windows, lower formation pressures, and uncertainty formation pressure and strength, and drilling salt sections.
Contact Ken Fischer for more information on the DGD Subcommittee or the UBO & MPD Committee.