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To make its operations cheaper and more effective, Shell Petroleum Development Company of Nigeria Limited (SPDC) has introduced nitrogen to produce waxy wells, as a method of solving problems in oil production.

To make its operations cheaper and more effective, Shell Petroleum Development Company of Nigeria Limited (SPDC) has introduced nitrogen to produce waxy wells, as a method of solving problems in oil production.

The gas was used to prevent build-up in two wells in the Northern Swamp Area-Egwa-32 and Odidi-5 and succeeded in increasing the flow temperature and ensuring unhindered production from the well to the surface. Apart from freeing up the flow route of wax, the pioneering use of nitrogen added a sustained production of more than 1,5000 barrels per day.

SPDC’s Asset Development Planner, Mr. Tope Tunde, said: “This break-through makes well prove to be the answer to our wax problems and its cheap, convenient and effective. We do not need to import nitrogen; the gas constitutes 79 per cent of the atmosphere.”

The wax, according to him, “is formed when the temperature of crude oil falls as it flows from the reservoir to surface,’’ explaining that “the oil losses temperature to the surrounding environment as it gets up the tubing to surface and this is accelerated by the properties of completion fluid brine, a sodium chloride solution with high thermal conductivity.”

As the temperature level dropped below cloud pint, he said that the wax would begin to form, blocking the flow route and stopping crude production. He stressed that on normal situation, the substance would be removed by conventional de-waxing methods, which would not only cost huge sums of money, but it would also interrupt production.

Tunde explained: “After exhaustive study in which we discounted other insulating media, we settled on the use of nitrogen in Egwa-32 and Odidi-5, two wells which have suffered greatly from wax problems. For instance, Odidi-5 was found waxed-up in September in 1988 and required biannual wax cutting thereafter to sustain production.

“The new process was relatively simple. We displaced 5,000ft of completion borne to nitrogen by introducing the gas from tanks at high pressure into the casing. Because nitrogen has low thermal conductivity, it helped the crude stream to retain its heat as it flowed up. The flowing tubing head temperature of Odidi-5 showed a rise from 68 degrees Fahrenheit to 82 degrees and sustained production at 800 barrels of oil per day.

“At Egwa-32, the temperature gain was from 65oF to 86oF at a production level of 791 barrels of oil per day. What is more, when we returned to both wells we found no wax,” he added.

The breakthrough attracted attention in the Gulf of Mexico where wax problems had dogged oil production deep offshore. With help from SPDC, the production team there applied nitrogen in six wells with astounding success. In some wells, the temperature and production gains nearly doubled.

Source : www.independentng.com

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