Generally, the most common reason for low productivity of gas wells in the offshore Mediterranean Sea operations of Egypt is near-wellbore formation damage. Near-wellbore formation damage, referred to as "skin" in petroleum engineering parlance, causes a huge reduction in native formation permeability, thus adversely affecting productivity. Skin damage can occur from one or more of the following reasons: mud and cement damage, mechanical damage from drilling, damage from perforating guns, scale deposition, paraffin and asphaltene depositions, water blocks, gas blocks, acid sludges, emulsions, etc. Dependent upon the type of damage, the stimulation technique will vary; however, the prevalent techniques available to stimulate damaged formations are hydraulic fracturing and matrix acid stimulation.
A new technique called "fluidic oscillation" was proposed to overcome many of the limitations of the previous two techniques. This technique would be especially applicable when there are uncertainties regarding rock mineralogy. In these instances the possibility of further damage exists if incompatible treatment fluids are pumped/"squeezed" into the formations. "Fluidic Oscillation" is primarily a mechanical, nonfluid invasive stimulation technique; (i.e., it is not essential to inject the treatment fluid into the reservoir to break down damage though it does not preclude its use in that manner). The damaged formations are stimulated by subjecting them to alternating bursts of pressure waves generated by pumping fluids through a fluidic oscillator. The treatment fluid can be plain water, diesel, or any other solvent that is desired to pass through the affected zones and be circulated out of the hole. The continuous cycling of these pressure waves causes the skin damage to reach its fatigue failure point. After this, a small amount of acid/solvent blend can be pumped to wash the damaging materials out of the well bore. The fluidic oscillator can be positioned against the zones of interest by using coiled tubing.
The fluidic oscillation technique was used in Egypt on two gas wells (until the writing of this paper) for this operator. In the first well, it is believed that there was heavy formation damage caused while drilling the well. After the stimulation treatment the gas production of the well was increased by 325%. In the second well, the post-stimulation gas production rate was increased by 40%. From IPR curves of the two wells, before and after stimulation, it was found that the absolute open flow (AOF) potential of each well was highly increased after stimulation. Compared to the results obtained from previous treatments, it was found that this technique was successful in stimulating gas wells in Egypt. The main objective of this paper is to evaluate this technique through actual case studies.