Petroleum Production Operations Multiple Choice Questions on “Sandstone Acidizing”.
1. What is the primary reason to acidize the sandstone wells?
a) To increase the permeability
b) To decrease the permeability
c) To decrease the flow rate
d) To create fracture
Answer: a
Clarification: The primary reason to acidize the sandstone wells is to increase the permeability by dissolving the clays near the wellbore. If carbonates are present in sandstone then it must be removed with HCl prior to treating with HF.
2. What is the percentage of Carbonate in sandstone more than which if present, should be acidized with HCl only?
a) 5%
b) 10%
c) 20%
d) 30%
Answer: c
Clarification: If carbonates are present in sandstone then it must be removed with HCl prior to treating with HF. If more than 20% of carbonate is present in sandstone then it should be treated with Hydrochloric acid (HCl) only.
3. What is the basic combination of acids used in Hydrofluoric acid treatment?
a) 13% HF + 12% HCl
b) 13% HF + 12% HCl
c) 12% HF + 3% HCl
d) 3% HF + 12% HCl
Answer: d
Clarification: The basic combination of acids used in the Hydrofluoric acid treatment is 3% HF + 12% HCl. The chemical formula of Hydrofluoric acid is HF and the chemical formula of Hydrochloric acid is HCl.
4. To avoid CaF2 precipitation, HCl precipitation is needed in sandstone acidizing.
a) True
b) False
Answer: a
Clarification: The statement is true. To avoid CaF2 precipitation, HCl precipitation is needed in sandstone acidizing. The pre-flush of HCl is mainly used to dissolve any carbonates present with the sandstone.
5. Diversion agents are the chemical agent used in stimulation jobs to ensure uniform injection.
a) True
b) False
Answer: a
Clarification: The statement is true. Diversion agents are type of chemical that are used in the petroleum industry to improve the fluid injectivity. Now-a-days it is extensively used in petroleum industry for the improvement purpose.