Drill-in fluid is the first fluid that contacts the reservoir zone and thus has the first scope of causing severe formation damage if not designed properly by considering all the factors that play a major role in causing near wellbore formation damaged.One of the major factors that mitigate DIF induced formation damage is its particle size distribution that matches the pore size distribution of reservoir rocks.That’s why drill-in fluid is designed using sized bridging materials(SBMs)that have size distribution similar to the size of pore size distribution of reservoir rock.If for any reason,the size distribution is not maintained in the DIF, the drill-in fluid will lose the bridging capability leading to deep penetration of fines,mud spurt and mud filtrate and thus can create severe formation damage. Typically calcium carbonate or sized salts are used as the bridging materials due to their easy removal by acidization or dissolution after completing a well.The performance of calcium carbonate-based SBMs is highly dependent on the quality of the product i.e.material toughness and attrition resistance of the materials.Hence,selection of high quality sized bridging materials that have high attrition resistance is very important to minimize size degradation due to the hydro-mechanical action of drilling mud,mud motors,drill pipe,drill bit,etc.This paper describes the application of a fit for purpose laboratory method in characterizing calcium carbonate-based SBMs available from different sources and vendors to dem-onstrate the effect of poor quality SBMs in causing formation damage while drilling.Experimental results indicate serious size degradation of bad quality SBM products under the attrition effect of free rotating solid cylinder in a test cell.The results demonstrate the importance of evaluating the SBMs using a fit-for-purpose test method to select the best and reject the inferior.
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