After several years of operation in a gas-rich environment of Egypt, engineers started noticing productivity declines in wells. In some cases, productivity was down more than 16 percent, which was a considerable loss for the company. Testing showed what engineers suspected was the problem — fines migration.
Formation damage from fines migration is an expensive problem in the oil industry around the world. When fines migrate, they tend to build up in the near-wellbore area over a period of time, reducing productivity. So what can oil producers do?
Fines are loose or unconfined, fine particles, usually smaller than 40 microns, in the pore spaces of sandstone. They can be clays, feldspars, micas, plagioclase, or similar materials. And they’re present in every hydrocarbon formation. These tiny particles cause big problems in wells.
Hard to See Evidence
When fine migration starts, it’s hard to see the evidence. Well operators might notice a slow decline in productivity over a period of months, or sometimes over just weeks. In wells with fine migration problems, core flood tests have shown that the particles reduced the permeability of the formation by up to 22 percent. But the only symptom of the damage that’s occurring underground is a slow decline in productivity.
Particles on the Move
Though fines are present in every hydrocarbon formation, it is what’s happening in the well that causes them to start moving. Evidence suggests that fine migration happens when low salinity (less than 2 percent) or high pH (more than 9 percent) fluids are introduced into a water-sensitive formation. Fines migration also happens when there are high flow rates near the wellbore area. The now-mobile fines strain thin pores, and that leads to permeability decline.
Stop the Damage
There’s no preventing fines because they’re already present, and there’s no way to really stop them from migrating because that’s part of the production process. But there are successful treatments to stop the damage and restore well productivity. With fines-stabilizing chemicals and mud-acid treatments, well operations have successfully gotten their wells back to their previous high performance.
In the well in Egypt, operators used an organic clay acid treatment. The well went from being down more than 16 percent from its original base effective permeability to nearly 1.5 percent above that base rate. Fines don’t have to be a death sentence for your production well, or cause costly damage. A call to ChemFlo will get your well back or better than before.