Page 264 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

248 Gas Wettability of Reservoir Rock Surfaces with Porous Media

experimental results illustrate that the concentration of degreaser is
15%. When the dosage is greater than 3750 ppm, oil degradation
reaches 95% and above, and the oil content of cuttings is lower than
1%, featuring good oil degradation effect.

6.4.2.3.2 Biodegradability Evaluation of Degreaser
Biodegradability refers to the ability to degrade under natural conditions. BC
value (namely BOD 5 / COD value) is commonly used internationally as an
index to determine the biodegradability grade. The relationship of BC value
and biodegradability (grading standard of biodegradability) is: BC $ 25, easy
to degrade, and BC 5 15B25, degradable. BC 5 5B15, a little difficult to
degrade, and BC , 5, difficult to degrade.

The BC value was calculated by measuring BOD 5 and COD values of efficient
and degradable degreaser solution at certain concentration, and the perfor-
mance of degradability was correspondingly obtained.
Experimental Method The measurement method of COD refers to GB11914-
89 Water Quality-Determination of the Chemical Oxygen Demand-Dichromate
Method, and that of BOD 5 refers to HJ 505-2009 Water Quality-Determination of
Biochemical Oxygen Demand after 5 Days (BOD5) for Dilution and Seeding
Method. BOD tester and COD determinator are used to measure BOD 5 and
COD values, respectively, of 1000 mg/L degreaser water solution.
Experimental Results and Analysis The experimental results are shown in
Table 6.25. It can be seen from Table 6.25 that COD of 1000 mg/L degreaser
water solution is 1150.67 mg/L, BOD 5 is 207.67 mg/L, and BC value is
18.05%. The biodegradability is good and environment-friendly.

6.4.2.3.3 Pollutant Analysis of Treated Oily Cuttings
The heavy metal content of treated cuttings was measured. The measured
results are as shown in Table 6.26. It is clear that the oil and heavy metal con-
tent of treated cuttings all meet the discharge requirement.

Table 6.25 Experimental Results of Biodegradability of Degreaser
Water Solution
Group Test COD BOD 5 BC Biodegradability
Concentration (mg/L) (mg/L) Value
(mg/L) (%)

1 1000 1115 210 18.83 Degradable
2 1000 1100 197 17.91 Degradable
3 1000 1237 216 17.46 Degradable
Average 1000 1150.67 207.67 18.05 Degradable
value