Well Stimulation and WSVs

Well stimulation is a well intervention performed on an O & G well to increase production by improving the flow of hydrocarbons from the drainage area into the well bore. The assortment of drilling fluid pumped down the well during drilling and completion can often cause damage to the surrounding formation by entering the reservoir rock and blocking the pore throats (the channels in the rock throughout which the reservoir fluids flow). Similarly, the act of perforating can have a similar effect by jetting debris into the perforation channels. Both these situations reduce the permeability in the near well bore area and so reduce the flow of fluids into the well bore.

A simple and safe solution is to pump diluted acid mixtures from surface into the well to dissolve the offending material. Once dissolved, permeability should be restored and the reservoir fluids will flow into the well bore, cleaning up what is left of the damaging material. After initial completion, it is common to use minimal amounts of formic acid to clean up any mud and skin damage. In more serious cases, pumping from surface is insufficient as it does not target any particular location downhole and reduces the chances of the chemical retaining its effectiveness when it gets there. In these cases, it is necessary to spot the chemical directly at its target through the use of coiled tubing. Coiled tubing is run in hole with a jetting tool on the end. When the tool is at its target, the chemical is pumped through the pipe and is jetted directly onto the damaged area. This can be more effective than pumping from surface, though it is much more expensive, and accuracy is dependent on knowing the location of the damage.

Baker Hughes was the first service company to design and deliver ocean-going stimulation vessels and to receive the stringent Well Stimulation Vessel (WSV) classification in the Gulf of Mexico and Brazil. Its latest vessels have huge storage and pumping capacities, and advanced instrumentation and control systems, as well as redundant job- critical systems to reduce risks, costs and non-productive time, along with DP2 to guarantee vital station-keeping capabilities. Baker Hughes also has the majority of the well stimulation vessel market in Brazil and has three stimulation vessels under an exclusive contract to Petrobras, the Blue Shark, the Blue Angel and the Blue Marlin, all based in Rio de Janeiro. In Brazil pressure-pumping operations perform between 1200 and 1300 jobs a year, including cementing, stimulation, coiled tubing services, wellbore cleanup, casing running, completion tools, filtration fluids injection and chemical services.