According to Pavel and Grayson, closing the loop of fluids creates a circuit of incompressible drilling fluid that is capable of detecting a minute change in bottomhole pressure. Since the fluid cannot be compressed further, a small change in pressure—as little as a few gallons, from either an influx or loss—is transmitted through the fluid in seconds.
The fact that a closed-loop system gathers pressure and flow data in real time gives engineers a better understanding of what is taking place in the wellbore, improving traditional mitigation and MPD methods. Weatherford attains a high level of pressure control by using its Microflux control technology, which is an automated system that identifies pressure changes in real time and diagnoses the causes of those changes. Pavel and Grayson call this technique “fingerprinting.”
Through fingerprinting, the system can quickly differentiate between common activities like wellbore breathing and ballooning, and more serious situations like a kick or loss, and then make the proper response. By manipulating annular backpressure, the system lets drillers almost instantly change downhole pressure while simultaneously providing a faster way to detect a potential kick, which the system can then cycle out or, if necessary, alert the crew to a more serious well control situation. This allows rig crews to avoid spending too much time resolving minor issues, which can be quite valuable when using high-end deepwater rigs that regularly cost well over $500,000 per day.
WELL CONTAINMENT
In the year since the Deepwater Horizon caught fire and sank in the US Gulf of Mexico, the offshore oil and gas industry has placed an intense focus on developing a system dedicated to containing spills. One of the primary problems that led to millions of gallons of oil being released into the Gulf was the industry’s inability to cap and subsequently collect oil in a timely fashion.
In an attempt to prevent a situation similar to the Mancondo oil spill, when
BP was unable to cap the well for several months, the US Bureau of Ocean Energy Management, Regulation and Enforcement (B
OEMRE) issued new rules regarding containment. According to NTL 2010-N10, “For operations using subsea BOPs or surface BOPs on floating facilities, BOEMRE will evaluate whether each operator has submitted adequate information demonstrating that it has access to and can deploy surface and subsea containment resources that would be adequate to promptly respond to a blowout or other loss of well control. ... BOEMRE will evaluate whether each operator has provided adequate information in its current [oil spill response plan] describing the types and quantities of surface and subsea containment equipment that the operator can access in the event of a spill or threat of spill, and the deployment time for each.”
As a result, two companies have emerged with BOEMRE-approved solutions to possible future deepwater well containment emergencies: the Marine Well Containment Company (MWCC) and the Helix Well Containment Group (HWCG). Both firms are building off of the experience their constituent companies gained last year when they responded to the Macondo spill, although the two solutions have some differences.
Of the 10 deepwater drilling permits BOEMRE has issued since lifting the moratorium, six of the operators have chosen to sign on with Helix, while the remaining four operators have said they would use MWCC in the event of a spill.
Helix. HWCG is a consortium of 22 deepwater operators in the Gulf of Mexico, each of which has committed to a mutual aid agreement. The agreement allows any member to draw upon the collective technical expertise, assets and resources of the group in the event of an incident.
The two largest pieces of the Helix Fast Response System are well intervention vessel Q4000 and floating production unit (FPU) Helix Producer I, both of which are owned by Helix Energy Services and were put to use during the Macondo spill response. These vessels work in union with a crude tanker as well as a subsea cap and collection system, which are kept in the Gulf of Mexico region at all times.
The Q4000 is a dynamically positioned vessel specifically designed for well intervention and construction in extreme water depths. The ship is equipped with a multi-purpose derrick, two cranes with lifting capacities of up to 400 tons and seabed access to 10,000 ft, a 73⁄8-in. intervention riser system, two heavy-weather ROVs, an overall deck capacity of 4,400 tons, and a 39-ft 3 21-ft moonpool. In the case of an emergency, a well test skid and burner will be installed to burn 10,000 bpd of oil and 15 MMcfd of natural gas.
The Helix Producer I is a dynamically positioned FPU capable of processing 60,000 bpd and flaring 80 MMcfd. The vessel is able to rapidly disconnect from subsea facilities, allowing it to seek shelter from severe weather. It is equipped with facilities necessary to connect to a tanker for side offloading while providing a water curtain against heat radiation from continuous flaring.
Tied to the disconnectable transfer system on the Helix Producer I is a flexible 5-in. riser that departs from its buoy keel in a U-shape catenary configuration to connect to the Q4000 side offtake. It provides a conduit for transferring oil and gas from the Q4000 to the Helix Producer I. A 1,575-ft, 12-in. Manuli-type H3006 FF PU hose departs from the offloading skid on either side of the Helix Producer I and connects to the tanker’s side-loading skid for offloading.
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