• 5 hours Iraq Struggles To Replace Damaged Kirkuk Equipment As Output Falls
  • 10 hours British Utility Companies Brace For Major Reforms
  • 14 hours Montenegro A ‘Sweet Spot’ Of Untapped Oil, Gas In The Adriatic
  • 16 hours Rosneft CEO: Rising U.S. Shale A Downside Risk To Oil Prices
  • 17 hours Brazil Could Invite More Bids For Unsold Pre-Salt Oil Blocks
  • 18 hours OPEC/Non-OPEC Seek Consensus On Deal Before Nov Summit
  • 19 hours London Stock Exchange Boss Defends Push To Win Aramco IPO
  • 20 hours Rosneft Signs $400M Deal With Kurdistan
  • 22 hours Kinder Morgan Warns About Trans Mountain Delays
  • 1 day India, China, U.S., Complain Of Venezuelan Crude Oil Quality Issues
  • 1 day Kurdish Kirkuk-Ceyhan Crude Oil Flows Plunge To 225,000 Bpd
  • 2 days Russia, Saudis Team Up To Boost Fracking Tech
  • 2 days Conflicting News Spurs Doubt On Aramco IPO
  • 2 days Exxon Starts Production At New Refinery In Texas
  • 2 days Iraq Asks BP To Redevelop Kirkuk Oil Fields
  • 3 days Oil Prices Rise After U.S. API Reports Strong Crude Inventory Draw
  • 3 days Oil Gains Spur Growth In Canada’s Oil Cities
  • 3 days China To Take 5% Of Rosneft’s Output In New Deal
  • 3 days UAE Oil Giant Seeks Partnership For Possible IPO
  • 3 days Planting Trees Could Cut Emissions As Much As Quitting Oil
  • 3 days VW Fails To Secure Critical Commodity For EVs
  • 3 days Enbridge Pipeline Expansion Finally Approved
  • 3 days Iraqi Forces Seize Control Of North Oil Co Fields In Kirkuk
  • 3 days OPEC Oil Deal Compliance Falls To 86%
  • 4 days U.S. Oil Production To Increase in November As Rig Count Falls
  • 4 days Gazprom Neft Unhappy With OPEC-Russia Production Cut Deal
  • 4 days Disputed Venezuelan Vote Could Lead To More Sanctions, Clashes
  • 4 days EU Urges U.S. Congress To Protect Iran Nuclear Deal
  • 4 days Oil Rig Explosion In Louisiana Leaves 7 Injured, 1 Still Missing
  • 4 days Aramco Says No Plans To Shelve IPO
  • 6 days Trump Passes Iran Nuclear Deal Back to Congress
  • 7 days Texas Shutters More Coal-Fired Plants
  • 7 days Oil Trading Firm Expects Unprecedented U.S. Crude Exports
  • 7 days UK’s FCA Met With Aramco Prior To Proposing Listing Rule Change
  • 7 days Chevron Quits Australian Deepwater Oil Exploration
  • 7 days Europe Braces For End Of Iran Nuclear Deal
  • 7 days Renewable Energy Startup Powering Native American Protest Camp
  • 8 days Husky Energy Set To Restart Pipeline
  • 8 days Russia, Morocco Sign String Of Energy And Military Deals
  • 8 days Norway Looks To Cut Some Of Its Generous Tax Breaks For EVs
Alt Text

Is OPEC Considering Deeper Output Cuts?

You could argue OPEC and…

Alt Text

Why U.S. Crude Exports Are Booming

U.S. crude oil exports are…

Alt Text

Russia And China Continue To Boost Oil Ties

The Russia-China alliance is strengthening…

Brian Westenhaus

Brian Westenhaus

Brian is the editor of the popular energy technology site New Energy and Fuel. The site’s mission is to inform, stimulate, amuse and abuse the…

More Info

Chevron has Unveiled New Ship to Perform Dual Gradient Drilling

Chevron has Unveiled New Ship to Perform Dual Gradient Drilling

Chevron is about to put the first deepwater drillship designed with the capacity to perform ‘dual gradient drilling’ to work. The ship is a Samsung 12000 design capable of operating in 12,000 ft (3,658 m) water depth and is equipped for 40,000 ft (12,192 m) drilling depth.

Pacific Santa Ana Drillship
Chevron's Pacific Santa Ana Drillship.

Able to work in 2 1/3rd miles deep water and over seven miles into the earth the new ship is a world leader.  Named the Pacific Santa Ana the ship was built to Chevron’s specifications under a five-year contract with a subsidiary of Pacific Drilling S.A.  She’s headed for the Gulf of Mexico.  After additional equipment is installed and tested, Pacific Santa Ana will be used for exploratory and development drilling in the deepwater of the gulf.

Deepwater Drilling Pressures
Deepwater Drlling Pressures With and Without Dual Gradient Design.

Dual Gradient Drilling (DGD) employs two weights of drilling fluid (link to a Chevron presentation pf file).  Conventional drilling on land and at sea uses a single drilling fluid weighted with additives in the borehole.  DGD uses two weights of drilling fluid – one above the seabed, another below. This allows drillers to more closely match the pressures presented by nature and effectively eliminates water depth as a consideration in well design. DGD also allows drillers to more quickly detect and appropriately react to downhole pressure changes, which can enhance the safety and efficiency of deepwater drilling operations.

Deepwater wells in the Gulf of Mexico and other parts of the world including West Africa and the Caspian Sea are challenging due to the narrow pore pressure/fracture gradient environment. The DGD system gives operators a tool to manage the downhole environment while drilling, resulting in longer casing strings and/or larger diameter completions. The DGD system increases drilling efficiency while lowering mechanical risk and well costs.

The Pacific Santa Ana is equipped with a DGD riser, a mud-lift pump handling system, six mud pumps – three for drilling fluid and three for seawater – extensive fluid management system enhancements and more than 72,000 feet of DGD-related cables.

GE Mud Lift Pump
Chevron's new GE Built Mud Lift Pump.

A key element of the system is the MaxLift 1800 mud-lift pump from GE. To achieve a dual gradient, flow from a well being drilled is diverted to the MaxLift 1800 pump, which is located above the blow out preventer and pumps the cuttings-laden mud back to the drilling vessel in an auxiliary line.

The riser is then filled with seawater density fluid, so the reservoir “feels” as if the rig is located on the seabed (that means essentially that the pressures are neutral at the seafloor taking out the pressure that causes a blowout to flow oil out to the environment) since the MaxLift pumps prevent the hydrostatic pressure of the mud from being transmitted back to the wellbore. The new GE pump can deliver up to 1,800 gpm at discharge pressures up to 6,600 psi and can handle solids up to 1.5 inches in diameter.

The consultation firm Stress Engineering Services report for the US Bureau of Ocean Energy Management, Regulation, and Enforcement in 2011 (a pdf download) explored the risk profile of DGD, noted that DGD is a variation and a subset of Managed Pressure Drilling (MPD), which is a drilling tool that is intended to resolve chronic drilling problems including well stability and well control incidents.  MPD is intended to mitigate the risks and costs associated with drilling wells that have narrow downhole environmental limits by proactively managing the annular hydraulic pressure profile.

In the executive summary of the Stress Engineering Services report the firm points out, “Prior to April 20, 2010 (the date of the BP Deepwater Horizon explosion), the question of a catastrophic event was not a matter of “if”, but “when”. Drilling operations in a deepwater environment is an expensive endeavor. It is expensive for a number of reasons, but the chief reasons are to protect human life, equipment, and the wellbore in a very inhospitable environment. In a single pressure gradient environment (conventional drilling), it is easy to depart from the drilling window because of the narrow drilling window between the pore pressure and the formation fracture pressure. The Dual Gradient Drilling System re-establishes a margin of safety not obtainable in a single gradient system. Even the popular variant of Managed Pressure Drilling called Constant Bottomhole Pressure falls short of providing all of the well control benefits associated with DGD.”

“The most impressive aspect of Dual Gradient Drilling is that it is as safe or safer than current conventional drilling techniques AND provides for full riser margin, where the well is fully controlled in the event of riser disconnect AND problem wells can be drilled and completed instead of abandoned either with cement plugs or in a file labelled “TOO RISKY TO DRILL – TECHNOLOGY NOT AVAILABLE”.”

“…While there are risks associated with any drilling operation, deepwater well control is enhanced with DGD. Environmental episodes are also minimized. In the event of an emergency disconnect from the wellhead, seawater or a similarly compatible fluid dissipates into the surrounding water AND the well is under control because the hole is full of properly weighted drilling mud. DGD is like having a rig on the seabed floor. The riser margin is intact. It does not matter if the water depth is 5,000 feet or 15,000 feet, should the riser become disconnected, the well will be dead.”

One has to give Chevron credit for raw courage, something not seen in big corporate environments.  It’s likely the commitment for the building of the Pacific Santa Ana predated the BP Deepwater Horizon event, still Chevron has pressed on and is still pressing on in the face of a government playing shiftlessly on permits and permissions going so far as to deny pipeline applications.  One cannot say with any honesty that the industry has held back on investing in producing oil.

Now, to rephrase the words of Stress Engineering, TECHNOLOGY IS AVAILABLE.  Chevron is first with the Pacific Santa Ana and there are more ships readied to drill more wells even deeper.

By. Brian Westenhaus

Source: Big Oil Chevron Ready to Drill Deeper and Safer Offshore

Back to homepage

Leave a comment

Leave a comment

Oilprice - The No. 1 Source for Oil & Energy News