Near Wellbore Damage and Types of Skin Depending on Mechanism of Damage

Abstract Near wellbore damage has been a topic of great attention over last many decades. Typical measures of formation damage is skin factor (S) which is a hydrodynamic parameter characterizing additional resistance to flow of fluids in the near borehole zone of the reservoir, leading to reduced production (yield) compared to the perfect (ideal) wells. This has been a great attention of topic because it directly effects on formation fluid productivity from the concerning well. Reasons behind formation of this damage can be combinations of several mechanisms are clay particle swelling, fluid loss or change in formation water saturation, wettability reversal, Emulsion blockage, Mutual precipitation of soluble salts in wellbore-fluid filtrate and formation water, Deposition of paraffins or asphaltenes, Fines migration etc. Operations which are usually leads to those mechanisms to happen are drilling, cementing, well completion, work-over operations, production of fluids, injection of fluids and Operations to isolate water production etc. This paper describes mechanisms of the formation damage. And introduces types of skins depending on the mechanism of damage and source operation, and Types of skin are The mechanical or formation damage skin factors (Sd)Completion pseudo skin factor (Sp)Partial penetration skin factor (Spp)-Geometrical pseudo skin factor (Sg)Multiphase pseudo skin factor (Sm)Non-Darcy flow or Rate-dependent high velocity or turbulent flow pseudoskin factor (Sturb) This paper also describes all type of skin in detail with mathematical models given to calculate the skin individually as well as effective skin.