ASSESSMENT OF FORMATION DAMAGE OF SANDSTONE RESERVOIRS IMPACT OF FINES MIGRATION AND SOLIDS PLUGGING ON SANDSTONES’ RESERVOIR QUALITY, SARIR

Abstract

Fundamental controls on formation damage and reservoir quality of Sarir Formation Sirt Basin Libya are authigenic clay mineral types and their distributions. However, petrologies investigation obtained from the study area in five wells and concentrated on main rock components and the parameters that may have impacts on reservoirs. The petrographic observation shows the main authigenic clay minerals are kaolinite and dickite, these investigations have confirmed by X.R.D analysis. Clay fraction. mainly kaolinite and dickite were extensively presented in all wells as high amounts. As well as traces of detrital semictite and less amounts of illitized mud-matrix can be seen using SEM. Thin layers of clay is also present as clay-grain coatings in local depth interpreted as remains of dissolved clay matrix which is partly transformed into kaolinite adjacent and towards pore throat. This also may have impacts on most of the pore throats of this sandstone which are open and relatively clean with some of fine material have been formed within these pores. This material is identified by EDS analysis to be collections of not only kaolinite booklets but also small disaggregated kaolinite platelets derived from the disaggregation of larger kaolinite booklets. These patches of kaolinite not only fill these pores, but also coat some of the surrounding framework grains. Quartz grains often enlarged by authigenic quartz overgrowths partially occlude and reduce porosity. Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) was conducted on the post-test samples to examine any mud filtrate particles that may be in the pore throats. Semi-qualitative elemental data on selected minerals observed during the SEM study were obtained through the use of an Energy Dispersive Spectroscopy (EDS) unit. The samples showed mostly clean open pore throats, with limited occlusion by kaolinite. The EDS analysis confirmed the identification of the fine grained disaggregated material as mainly kaolinite, though sample from well VV6-65 (8912.70 feet) did show some other very fine-grained elemental combinations (Si/Al/Na/Cl, Si/Al Ca/Cl/Ti, and Qtz/Ti).