Two drill core samples from each of the four reservoir units in the Merrimelia Field, the Murta Member, Namur Sandstone Member, Hutton Sandstone and Nappamerri Formation, were examined to determine their petrological and porosity characteristics and their potential for suffering formation damage during drilling, completion, stimulation and production. Thin sections were prepared and used to establish mineral composition and visible porosity via point counting, to measure mean grain size and the degree of sediment sorting, to study the diagenetic changes which have occurred in the reservoir sandstones during burial and to assess their effect on porosity, and to assemble a set of illustrative photomicrographs of petrological features. X ray diffraction analysis was used to determine the clay mineralogy of the samples, and all samples were examined using scanning electron microscopy to provide additional information about rock textures, particularly the pore configuration and the distribution of clays and cementing minerals. The author concludes that variations in reservoir quality of all four reservoir intervals result mainly from the type and extent of diagenetic changes which have occurred in the rocks during burial. These changes are in turn partly controlled by textural and compositional characteristics of the sands as originally deposited. All formations are slightly hydrochloric acid sensitive due to the presence of siderite cement, and the Murta Member is also hydrofluoric acid sensitive due to its content of dolomite. The Murta, Namur and Hutton reservoirs are also slightly freshwater sensitive because of their content of swelling illite-smectite clays. Fines migration is likely to be the most serious potential problem during production as all the reservoirs contain abundant authigenic clay, particularly kaolinite and dickite which are readily dislodged during flow. The author provides some general recommendations for amending well treatment practices during the field development stage which are aimed at minimizing possible formation damage stemming from the above factors.