Skin Factor: Relationships, Conclusions and the Formula for the Key Hydrodynamic Parameters

R. S. Mufazalov, NPF Timurneftegaz, City of Oktyabrskiy, Bashkortostan

The area near the wellbore of an oil and gas formation is a very active and unstable zone. During the process of drilling the first well into the payzone, well completion, and the operations that take place during this process, the natural energy- and mechanical equilibrium of the formation is upset. The near-wellbore area goes through physio-mechanical and hydro-thermodynamic changes of the rock property and characteristic, changes of the formation fluid, and physiochemical, chemical-biological transformation take place, including deposits of asphalt, resin and paraffin, hydrate build-up, swelling of clayeous minerals and reservoir breakdown, as well as microbiological and gas blockage of the inflow. The electromagnetic equilibrium of the formation is upset, and, because of this, hydrogen bonds are formed within the hydrocarbon systems (up to 40 kJ/mol). These form in the capillaries and fractures of the near-wall area of the wellbore, and the bond energy – determined by van der Waals forces – is redistributed. All of these factors, and many more which have not been mentioned here, considerably upset the permeability and porosity of the near-wellbore area, forming the non-uniform permeable and porous skin zone and lead to reduced flowrate to the well bore…

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