A new thermocycling column heat exchanger system installed on gas-producing platforms can cool a 50 million SCFD gas flow from 300°F to 160°F at a low cost of approximately $500,000 or less.
Conventional heat exchanger installations using power generation or transmission range in cost from $2,000,000 to in excess of $5,000,000.
The new system, the Aqua-Gas Exchanger, requires no external power source and has no mechanical moving parts. It is virtually maintenance free, allowing unmanned operation for long periods of time. Plus, little or no platform deck space is needed to install the system.
EDG Inc. was recently awarded a patent for the system.
The problem of handling hot gasses and condensate became increasingly difficult as offshore wells are drilled into deeper and deeper formations. The production from these formations is hot enough to boil seawater and will cause rapid corrosion of ordinary pipe and fittings.
One method of addressing the problem is to make the line pipe of exotic metals such as titanium. This has been determined to be prohibitively expensive.
Others have approached the problem by seeking methods of reducing the temperature of the produced gas. The most common method is a fin-fan cooling system in which blowers are used to force air over a series of fin tubes to cool the gas as it flows through the system, much like the radiator in the cooling system of an automobile.
The fans have considerable power requirements and supplying the energy to run them often requires a separate electrical generation system or supply wires strung between platforms.
This system is heavy, very large and takes up an inordinate amount of space on a production platform. It also has many moving parts that must be serviced periodically.
The Aqua-Gas Exchanger system employs sea water percolating naturally around a bundle of one-half to one-inch cooling tubes to reduce the temperature of the produced gases. The tube bundle is enclosed in a caisson-like pipe.
The exchanger is attached to a leg of the production platform with its top at or just below the surface of the surrounding water.
The produced gas is piped from the well head to an entry tube at the top of the heat exchanger. Seawater enters the exchanger through ports at the bottom of the caisson and completely immerses the tubing bundle.
As the water rises inside the caisson, heat from the produced gas raises its temperature to the boiling point. The heated water rises naturally and exits the exchanger through ports at the top of the caisson, creating a continuous flow.
Each Aqua-Gas Exchanger is custom-designed to suit the specific requirements of an installation. The typical length of the exchanger is approximately 50 feet, although designs for greater or lesser water depths can be created.
The overall diameter of the enclosing caisson can be varied to suit the volume of water needed to cool the produced gasses.
While most installations will use a simple vertical configuration, the exchanger can be configured with a horizontal section or even in a U-shape to accommodate the requirements of the installation.
The heat exchanger can be used to cool sweet or sour hot gasses or condensate. The principles of the system remain the same for any produced hydrocarbon. The cooling tubes may be made of any material that can resist the pressures and corrosive effects of the produced gases.
© 2001 Mena Report (www.menareport.com)