Controls of Acid-sensitive Minerals on Reservoir Sensitivity Testing: An Example from the Silurian Kepingtage Formation in Tazhong Area, Tarim Basin

摘要

The Silurian Kepingtage Formation in Tazhong area is regarded as an acid-sensitive hydrocarbon reservoir.However,formation mechanism of acid-sensitive of the reservoir cannot be interpreted by the existing acid-sensitive evaluation criterion based on damage rate.The contents of acid -sensitive minerals illustrated by bulk-rock XRD,scanning electron microscopy and clay mineral composition analysis exert the dominant control on acid-sensitive flow testing of the reservoir.The iron-bearing minerals (including pyrite cements and chlorite cements) mainly deteriorate reservoir quality,while the iron-free minerals (including calcite cements and dolomite cements) mainly improve permeability.The permeability variation of the tested samples is controlled by the relative content of two acid-sensitive minerals.On the basis of newly established sensitivity mechanism and its influence on permeability,the corresponding ion (Fe2+) stabilizer was added to the acidizing fluids during the acidification reconstruction,which inhibited the negative factors of acid-sensitive minerals and improved the target layer quality effectively.