Lower Cretaceous sandstones of the Qishn Formation have been studied by integrating sedimentological, petrological and petrophysical analyses from wells in the Masila oilfields of eastern Yemen. These analyses were used to define the origin, type of diagenesis and its relation to reservoir quality. The sandstones of the Qishn Formation are predominately quartz arenite to subarkose arenite with sublitharenite and quartz wackes displaying a range of porosities, averaging 22.33%. Permeability is likewise variable with an average of 2844.2 mD. Cementation coupled with compaction had an important effect on porosity destruction after sedimentation and burial. The widespread occurrence of early calcite cement suggests that the sandstones of the Qishn Formation lost significant primary porosity at an early stage of its diagenetic history. In addition to poikilotopic calcite, several different cements including kaolinite, illite, chlorite and minor illite–smectite occur as pore‐filling and pore‐lining cements, which were either accompanied by or followed the development of the early calcite cement. Secondary porosity development occurred due to partial to complete dissolution of early calcite cements and feldspar grains. The new data presented in this paper suggest the reservoir quality of Qishn sandstones is strongly linked to their diagenetic history; hence, the reservoir quality is reduced by clay minerals, calcite and silica cements but is enhanced by the dissolution of the unstable grains, in addition to partial or complete dissolution of calcite cements and unstable grains. Copyright © 2015 John Wiley & Sons, Ltd.

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Improved methods of analysis and quantification of heavy mineral assemblages in Cambrian to Early Cretaceous sandstones of southwest Sinai have revealed successive changes in provenance that reflect both rejuvenation of the Arabian Shield and changes in the topographic configuration of the source area. Three mineral units have been identified in the Cambrian succession, at least three in the Carboniferous and three in the Cretaceous. It is predicted that the genetic units defined by these successive changes in mineralogy will be of regional extent and thus assist in elucidating the history of uplift of the Arabian-Nubian Shield and provide a better means of correlating sandstone units into adjacent areas. Variation in the abundance of apatite in the Cambrian succession is independent of provenance signature and is interpreted as reflecting alternating dry and humid climatic conditions.

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