Page Title

Page Title

		Date of Patent: Sep. 4, 2018
		Issued by: United States Patent and Trademark Office

		Title: TUBULAR CONNECTION ASSEMBLY FOR IMPROVED FATIGUE PERFORMANCE OF
		METALLIC RISERS

		Description: A flared and thickened tubular end assembly to improve the fatigue
		performance and increase the fatigue life of tubular connections subjected to cyclic loading such as connections encountered in but not limited to offshore steel catenary risers (SCRs) and steel lazy wave risers (SLWRs)

EPC (European Patent Convention) Patent: Approved, Number Pending

BENEFITS

		Overcomes the limitation of traditional upset ends imposed by increasing the wall
		thickness only (keeping the same internal diameter of the pipe) vis-à-vis welding

		Eliminates weld qualification of excessive wall thickness using traditional upset ends
		and associated risk, time, and cost

Reduces offshore welding time and cost

Provides an alternative to using costlier materials such as titanium

		Provides an alternative to using non-established connections for steel catenary risers
		(SCRs) and steel lazy wave risers (SLWR) such as flanged or threaded connections

BENEFITS COMPARED TO STEEL LAZY WAVE RISERS (SLWRS)

		Significantly simpler to analyze and design—eliminates the effort and time required to
		establish the proper configuration of SLWRs and changes in configuration as a function of contents and floater offsets

		Eliminate the high cost of buoyancy modules (several million US dollars), installation
		complexity, limitation on choice of installation methods and vessels, and associated cost impact

		No gaps in strakes in the "hog bend" section of the riser (section with buoyancy
		modules)

		Better short- and long-term integrity—no buoyancy modules to worry about especially
		for insulated risers and straked risers

Eliminate the environmental impact of buoyancy modules’ fabrication and disposal

FABRICATION

Can be fabricated either as a separate forging or integral with the pipe

		Fabrication as separate forgings requires WPQ, fatigue testing, and AUT
		qualification/validation of the

		Pipe-to-forging welds
		Forging-to-forging welds

		Fabrication integral with the pipe requires WPQ, fatigue testing, and AUT
		qualification/validation of the

		Flared and Thickened End-to-Flared and Thickened End welds
		This would likely eliminate the WPQ, fatigue testing, and AUT
		qualification/validation of the SCR pipe welds—would definitely eliminate it for thickness of the integral flared and thickened ends within certain code limits of the SCR pipe thickness

EXAMPLE

In this example, the SCR pipe is 7.25in ID X 1.75in WT. The fatigue life is low and flared and
thickened ends are needed to provide a factor of 4 in order to meet the design life.

		Keeping the same pipe ID (traditional upset ends) requires a 7.25in ID X 2.3in
		WT upset end--this thickness is excessive vis-à-vis welding
		Keeping the same pipe wall thickness requires an 8.997in ID X 1.75in WT flared
		end--this increase in ID is probably excessive
		Alternative Flared and Thickened Ends are

		8.469in ID X 1.90in WT--this increase in ID is more reasonable
		8.139in ID X 2.00in WT--this increase in ID is yet more reasonable and
		the increase in WT is also reasonable vis-à-vis welding

Other Flared and Thickened End configurations are also possible as desired

FLOW VELOCITY

		*Q = V1 A1 = V1’ * A1’ => V1’ = V1 * (A1/A1’) = V1 * (D1/D1’)**^2
		I.e. as the diameter increases, the velocity decreases

Example

		SCR pipe: 7.25in ID X 1.75in WT
		Flared & Thickened Ends: 8.139in ID X 2.00in WT
		V1’ = 0.79 V1

FLOW PRESSURE

		P1 + ρ g h1 + ½ ρ V1^2 = P1’ + ρ g h1’ + ½ ρ V1’^2 (Bernoulli’s Eqn.) =>
		P1’ = P1 + ρ g (h1 – h1’) + ½ ρ (V1^2 - V1’^2)
		I.e. as the diameter increases, the pressure increases

Example

		SCR pipe: 7.25in ID X 1.75in WT
		Flared & Thickened Ends: 8.139in ID X 2.00in WT
		ρ = 1.71 lb.sec^2/ft^4 (55 pcf oil)
		P1 = 10 ksi
		h1 – h1’ = ~ 2.5ft Length of Flared & Thickened Ends
		V1 = 11.33 ft/sec (corresponds to production of 50 Mbbpd)
		V1’ = 8.95 ft/sec
		P1’ = 10.0012ksi

POTENTIAL EROSION

		Potential Erosion on Transition from Flared & Thickened Ends-to-Pipe
		From DNVGL-RP-O501

Example

		SCR pipe: 7.25in ID X 1.75in WT
		Flared & Thickened Ends: 8.139in ID X 2.00in WT
		ρm = 881 kg/m^3 (55 pcf Oil)
		ρt = 7800 kg/m^3 (487 pcf , Steel pipe)
		P1 = 10 ksi
		V1 = 11.33 ft/sec (3.45 m/sec, corresponds to production of 50 Mbpd)
		V1’ = 8.95 ft/sec (2.73 m/sec), V1 is used conservatively
		mp = 0.015 kg/sec (0.033 lb/sec, Mass rate of sand)
		dp = 0.0005 m (0.5mm, ~20 mils, Sand particle diameter)
		As Velocity increases, measures to control mass rate of sand increase
		The transition thickness can be increased to accommodate potential
		erosion (e.g. 0.29mm for 30-yr riser life and 1:4 transition slope)
		Erosion is not an issue for export SCRs
		CFD analysis can be performed for better prediction of potential erosion

PATENTS

ARTIFEX ENGINEERING, INC. HAS THE FOLLOWING PATENT