Page 247 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Application of Gas Wettability CHAPTER 6 231

6.4.1.3 CLEANING DRILLING CUTTINGS METHOD
Cleaning drilling cuttings methods include alkali wash, surfactant wash,
microemulsion wash, and extraction technology. The main principle is to
reduce the interfacial tension of the system, emulsify the oil in cuttings, and
change the wettability of cutting surfaces and other similar compatibility prin-
ciples [46,47].
The cleaning cuttings technology has the advantages of safer operation,
requirement of low-cost equipment for oil recovery, and is also economical.
There are, however, shortcomings such as strong handling of the agent, lack of
broad-spectrum treatment agent, and may carry secondary pollutants—oily
wastewater.
Supercritical CO 2 extraction technology is a newly developed cleaning drilling
cuttings method. It has become the new direction for processing oily cuttings,
but is limited to indoor research and has limited field applications and
practice.

6.4.1.4 CENTRIFUGAL SEPARATION TECHNOLOGY
The principle of centrifugal separation technology is simple. The centrifuge
can generate extremely high angular speed, and centrifugal forces are much
greater than gravity. Hence, for substances of different concentrations, the
velocities set are different for easy separation [48 55].
When the oily cuttings are processed by conventional separation devices, the
oil content of cuttings is only around 10%. However, when the oily cuttings
are processed with closed cutting liquid extracting centrifuge, the oil content
after treatment is as low as 2.5%, while the oil content after treatment with
oil-based drilling fluidis as low as 3%B5% [56 61].

6.4.1.5 BIOLOGICAL TREATMENT TECHNOLOGY
Biological treatment technology is used mainly to mix oily cuttings, water,
nutritional agents, degradation strains, and other surfactants; and to degrade
toxic petroleum pollutants into carbon dioxide and water, or other harmless
micromolecular substances, by making use of microorganism-based metabo-
lism at a certain temperature and pH value [57].

Biological treatment technology boasts of low cost, thorough treatment, is
eco-friendly, and has zero secondary pollution. The treatment cycle is, how-
ever, longer.

Recently, a different kind of harmless treatment technology is being researched
and developed, which integrates mechanical degreasing, chemical treatment of
degreaser, and, later, biological treatment technology to improve the overall
treatment results.