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Why perforate?

DYNAWELL is one of the world’s leading suppliers of oilfield-related perforation products. However, you may well be asking yourself why perforation products are needed in the first place. Surely you just drill a well and the oil starts flowing because the pressure underground is higher than on the surface. Unfortunately, oil production is not quite as simple as that.

A common misconception is that an oil field is like a huge lake of water where you simply need to pipe off as much as you want. Oil is actually stored in porous reservoir rock formations. After hydrocarbons have been found through seismic prospecting (for more details refer to http://en.wikipedia.org/wiki/Reflection_seismology), an exploration well will be drilled. If the find is commercially viable, a confirmation well will then be drilled and the oil field goes on stream. However, to stabilise the borehole a casing (or pipe) has to be cemented into place. And this is where perforation comes into play.

What is perforation?

In the context of oil wells, perforation involves punching holes into the casing of the borehole to connect it to the reservoir. The final stage of completion of a well involves running in perforating guns down to the desired depth and firing them to perforate the casing and create a flow path in the reservoir rock formation. Perforating guns consist of a carrier (Hollow Carrier Gun System), shaped charges, detonating cord and an initiator. A typical perforating gun will carry many dozens of charges.

Usually, electrical signals from the surface are used to fire perforating guns. This is referred to as running the guns on an E-line. More recent technologies allow the guns to be run on a so-called slickline. In contrast to E-line where communication with the surface is possible, a slickline firing system works through a mechanism on the gun that arms the charges once they reach a certain temperature and pressure before a timer fires them at a set interval.

Benefits of perforation

Perforation allows an operator to control a well better. Casing the bottom of the borehole allows a well to be completed without having to worry about reservoir fluids. It also allows the production points in the reservoir rock formation to be precisely selected and can be used to seal off perforations that are no longer productive through cementing or straddling. The disadvantage is that perforation can result in debris from the perforations reducing the productivity of the well. This problem can be mitigated through so-called underbalanced perforating, where a lower pressure in the borehole causes an insurge of fluids at the point of perforation. Ideally, that insurge will carry the debris with it. Other methods of stimulating the flow of oil include acidising and proppant fracturing, both of which aim to overcome debris damage and bring a well back to its full potential. An even more sophisticated solution to the problem of well debris is DYNAWELL’s No Debris Gun System.

Economics of oil production

The question of whether a well is commercially viable or not is largely dependent on the price of oil. As we are all very much aware, the price of oil has rocketed up in recent times. Although the knock-on effects of this huge price hike have had negative effects on many aspects of our lives, the high price does mean that oil companies can afford to spend significant sums on exploring for new oil fields and producing oil from fields that were not commercially viable only a few years ago. In view of the world economy’s dependence on oil and the finite nature of fossil fuels, maximising exploitation of the available resources certainly makes sense. For more information on oil price developments see http://www.oilnergy.com/1opost.htm