After granting several individual exceptions, the US Minerals Management Service is establishing standard operating procedures for managed-pressure drilling (MPD) in the Gulf of Mexico.
With a shift toward deeper drilling, operators are examining all technologies to improve safety and control costs. Drillers need precise control over downhole pressures because of the narrowed window between downhole pore pressure and allowable hydrostatic pressure in the fluid column. Excess hydrostatic pressures can cause formation or “skin” damage, reduce productivity, and waste drilling fluids.
Operators say MPD facilitates exploration and development because it allows drilling not otherwise technically possible. MPD uses an equivalent mud weight that combines static mud weight, equivalent circulating density, and surface backpressure maintained at or generally above openhole pore pressure.
MPD allows controlled returns to surface. Proponents attest that the closed mud returns system is inherently safer than conventional systems that are open to the atmosphere. Closed, pressurized systems have become common on US land rigs.
There are several variations of MPD:
- Constant bottomhole pressure (BHP), in which the objective is to maintain a constant annular pressure profile, as covered in the proposed MMS guidelines.
- Pressurized mudcap drilling, used to prevent cross flow in fractured formations and lost-circulation zones.
- Dual-gradient MPD, in which a lighter fluid is injected into the annulus to change the hydrostatic head in part of the wellbore.
- Health, safety, and environment, in which the closed mud returns system prevents accidental exposure to hazardous gases.
Both underbalanced drilling and MPD are being implemented worldwide, as seen during 2 days of project reviews at the recent International Association of Drilling Contractors/Society of Petroleum Engineers Managed Pressure Drilling and Underbalanced Operations Conference in Galveston.
MMS notice
Fred Hefren of MMS gave an update on the proposed notice to lessees pertaining to MPD and discussed how permitting might be streamlined.
He said the MMS will continue to review MPD projects and use what it learns to establish policy, work with industry to develop standards and policies required to permit MPD, and continue to issue permits case by case until standards are approved.
Don Hannegan of Weatherford Controlled Pressure Drilling & Testing Services, SPE distinguished lecturer for 2006-07, told OGJ that the IADC MPD subcommittee and the Offshore Operators Committee (OOC) contributed materials to the MMS in an effort to avoid development of overly prescriptive regulations.”.
Mike Conner, MMS section chief, told OGJ on Apr. 30 that the draft of the notice to lessees discussed in Galveston is being reviewed in Washington, DC, and that he expects it to be issued in 2-3 months. “Basically, what was presented in the draft is what engineers will use for guidelines” in applications for drilling permits, he said. Permitting would not change dramatically under the MMS initiative, although familiarity should speed approvals. MPD guidelines will need to be incorporated into drilling regulations.
MMS last issued revised drilling regulations in March 2003.
Four operators have applied for permits to use MPD in the gulf. Conner said only two have gone forward. Unocal used the constant BHP variation from a production platform south of Galveston. Shell Exploration & Production used a dynamic annular pressure control system to produce a constant BHP while drilling the Mars A-14 sidetracks from a tension-leg platform. Shell discussed the project in Galveston, calling the system a “promising new tool” for drilling narrow pore-pressure and fracture-gradient windows.
Research projects
In 2004, the Drilling Engineers Association sponsored DEA 155, which attracted funding from the MMS and is also known as Technology Assessment and Research Project 582, “A Probabilistic Approach to Risk Assessment of Managed Pressure Drilling in Offshore Drilling Applications.”
Principal Investigator Ken Malloy of MOHR Engineering is leading this joint industry project involving operators, contractors, and regulatory bodies to develop cohesive MPD practices.
On Mar. 27, 2007, MMS issued a progress report for Project 582. Since the Houston kickoff meeting in May 2006, MOHR has listed and described MPD variations and has transferred MPD data from Gulf of Mexico drilling reports. MOHR is reviewing MPD drilling report data; writing risk-reliability practices; creating a common data exchange for consistency of various descriptions between operators; soliciting additional data; and creating a database.
Industry has embraced MPD and will benefit from MMS’s adoption of standard practices.
