Petrographical studies can be undertaken to investigate the effects of production operations on sandstone reservoirs and to identify the nature of any rock-fluid interaction. In combination with diagenetic models the results may be employed to predict the effects of field development programmes on reservoir mineralogy, and to avoid costly damage to the reservoir's permeability. Acidization to remove drilling mud from Reservoir A samples was undertaken in two stages to avoid adverse rock-fluid interaction. HCl dissolved siderite and chlorite but did not increase permeability. This is because the dissolved siderite released previously cemented clay particles into the pore space. A subsequent mixture of HCl and HF dissolved all the clays present in the treated area including the drilling mud, but also etched the quartz cement. Permeability increased significantly but the rock's strength decreased. This could cause an influx of loose sand during hydrocarbon production. Water injection into Reservoir B samples caused a variety of rock-fluid interactions. In finer-grained samples movement of siderite rhombs as well as clay particles blocked pores, and changes in porewater composition caused smectite to swell. Both effects caused permeability to decline. In the coarser-grained siderite-free samples, permeability improved after oil and clay particles had been displaced. In the reservoir these effects would combine to exacerbate the effects of the existing reservoir heterogeneity. Steam injection into Reservoir C samples caused mineralogical reactions. Amounts of dolomite and kaolinite decreased, and smectite and calcite were generated. This may affect the permeability of the reservoir and will determine whether oil can be produced through the affected sediment.