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Continuous Pigging Multiphase Flow Concept

IP.com Disclosure Number: IPCOM000240213D
Publication Date: 2015-Jan-13
Document File: 3 page(s) / 289K

Publishing Venue

The IP.com Prior Art Database

Abstract

Oil and gas production in deep water marine environments around the world require some method of transferring produced fluids to centralized production facilities that separate oil, gas, and water – i.e., the fluids that are often produced together from an oil reservoir. One method of transfer is through offshore multiphase flow lines usually laid on the sea floor over some distance. These lines operate at high pressures and fluids in them tend to cool from the reservoir temperature to the ambient seawater temperature as they move because of heat loss. This cooling can result in the production of hydrates and the precipitation of waxes. All of these events can lead to flow assurance issues and ultimately to loss of production as complete or partial flow line blockage may occur. Current practices to limit these flow assurance problems include minimizing heat loss by using sophisticated insulation / heating systems, minimizing the length of flow lines, injecting chemicals into the flow line to control hydrate and wax formation, and providing dual flow lines to allow round-trip pigging from a surface platform. An alternative method to resolve these flow assurance issues may be to use a continuous pigging system in either a dual or single flow line system.

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Continuous Pigging Multiphase Flow Concept

Oil and gas production in deep water marine environments around the world require some method of transferring produced fluids to centralized production facilities that separate oil, gas, and water - i.e., the fluids that are often produced together from an oil reservoir. One method of transfer is through offshore multiphase flow lines usually laid on the sea floor over some distance. These lines operate at high pressures and fluids in them tend to cool from the reservoir temperature to the ambient seawater temperature as they move because of heat loss. This cooling can result in the production of hydrates and the precipitation of waxes. All of these events can lead to flow assurance issues and ultimately to loss of production as complete or partial flow line blockage may occur. Current practices to limit these flow assurance problems include minimizing heat loss by using sophisticated insulation / heating systems, minimizing the length of flow lines, injecting chemicals into the flow line to control hydrate and wax formation, and providing dual flow lines to allow round-trip pigging from a surface platform.

Concept Description

An alternative method to resolve these flow assurance issues may be to use a continuous pigging system in either a dual or single flow line system. One option for a dual flow line system allows the pig to make a round-trip down one flow line and back up the other (see Figure 1). Once it makes a complete trip, the pig reverses direction and flows back the other way. The pig itself is constructed and operated differently than current pigging operations.

Instead of being powered by pressurized fluids on one side of the pig, the concept utilizes a pig that is moved by a long cable. The cable is connected to a motor system on the production platform, connects to both sides of the pig, and forms a complete loop inside the dual flow line system. This will allow a motor on the platform to pull the pig in two directions allowing the pig to be pulled down one flow line to a subsea well manifold location and then back up the other flow line to the platform. Pulling on the other side of the pig allows the reverse course to the well manifold and back to the platform.

The pig itself requires a valve system that opens when the pig is moving from the platform to the well manifold along either flow line. If the pig is traveling toward the producing wells/manifold, the open valve system keeps the pig from building pressure in front...