Ali Teimouri Yadkuri - N.I.S.O.C.(National Iranian South oil company)

formation damage is a condittion which occurs when barriers flow develop in the near wellbore region to give rise to a lower than expected production rata from or injection rate into a hydrocarbon bearing zone this problem can occur during any phase of well development (drilling, well completion, well stimulation, workover/well servicing), or reservoir exploitation (DST, primary production, and supplemental fluid injection). Damage could result from solids plugging and/or from adverse fluid-fluid and fluid-rock interactions. most fluids introduced in the wellbore during various downhole operations are usually laden with solids to increase the weight the wellbore fluid and thus control any encountered reservoir pressure. Reservoir pores and pore throats in close proximity to the wellbore are susceptible to blockage by these extraneous solids. invasionof solids into the reservoir rock occur when solid particle size distribution in the wellbore fluids are not matched properly with the pore size distribution of the reservoir rock. solids invasion are normally limited to a feet around the wellbore. Between the factors can cause a severe damage, the most important factor is the invasion of solids and filtrate into formation due to overbalance drilling process. the entrainment of fines is highly increased in extremely permeable zones. understanding of formation damage mechanisms is very important for reservoir engineer, who would like to remove partially or completely.

formation damage, productivity, permeability, under balanced drilling