Which of the following lists five causes of positive skin?

Which of the following lists five causes of positive skin?

• A. Partial completion, inadequate perforations, phase changes(relative permeability reduction to the main fluid), turbulence, and damage to the natural reservoir permeability
• B. Water injection, fracturing, polymer flooding, steam injection
• C. Partial completion, formation compaction, chemical reaction, sand production
• D. Gas seepage, mud loss, closed perforations, rock dissolution

Answer: (A)

Positive skin means an extra pressure drop is required to push fluid into or out of the reservoir, caused by restrictions or damage in the near-wellbore region. The best answer collects five common mechanisms that create this additional resistance: partial completion reduces the effective flow area around the well; inadequate perforations leave chokepoints between the formation and the wellbore; phase changes can lower the main fluid’s relative permeability to flow in the near-well region, increasing flow resistance; turbulence near the wellbore adds frictional losses as the fluid transitions from the formation into the production string; and damage to the natural reservoir permeability around the well (from drilling fluids, fines migration, or formation damage) lowers near-well permeability. These factors together explain why the skin factor becomes positive. Other options either describe stimulation methods or omit key near-wellbore damage mechanisms, so they don’t cover the full set of five causes.

Positive skin means an extra pressure drop is required to push fluid into or out of the reservoir, caused by restrictions or damage in the near-wellbore region. The best answer collects five common mechanisms that create this additional resistance: partial completion reduces the effective flow area around the well; inadequate perforations leave chokepoints between the formation and the wellbore; phase changes can lower the main fluid’s relative permeability to flow in the near-well region, increasing flow resistance; turbulence near the wellbore adds frictional losses as the fluid transitions from the formation into the production string; and damage to the natural reservoir permeability around the well (from drilling fluids, fines migration, or formation damage) lowers near-well permeability. These factors together explain why the skin factor becomes positive. Other options either describe stimulation methods or omit key near-wellbore damage mechanisms, so they don’t cover the full set of five causes.