7.: Waxes

Wax deposition is commonly induced as a result of temperature changes, when the wax, which is a component of the crude oil, begins to come out of solution because the temperature has dropped below the wax-appearance temperature. Many fields could therefore suffer wax-deposition problems in the production process as a result of the temperature drops. As far as water injection is concerned, wax-deposition problems can occur because the injection water is invariably colder than the reservoir temperature.

When the wax-appearance temperature is equal to the reservoir temperature, so that any reduction in temperature can begin to induce problems, wax deposition can occur in the near-wellbore region of injectors where the injection of cold water causes the deposition. Such deposition can block pore throats near the injector, thereby resulting in a significant reduction in injectivity. Alternatively, in heterogeneous reservoirs, the wax might preferentially plug lower-permeability intervals and thereby have a negative impact on sweep even if the injectivity is not affected.