Effect of salinity degree of injected water on oil recovery from carbonate reservoir

32-37Water injection is considered the most successful and widespread secondary recovery method. Low salinity water injections is a well-established and proved technique for water flooding application in sandstone rocks to enhance the recovery efficiency; where the water salinity is adapted to a certain degree to extract the highest amount of oil from a reservoir. Reserve-estimation statistics show the significance of oil reserves in carbonate reservoirs, hence this work deals with the carbonate rocks where water flooding may fail due to many reasons, and the most common one is fractures existence in the carbonate rocks. This work applied the water injection for six carbonate (limestone) core samples from Belayim Formation of Middle Miocene age that extracted from an Egyptian offshore oil field in the Gulf of Suez. This carbonate facies is hard, vuggy, fragmented, dolomitic, and highly saturated with oil and considered a good reservoir. Relative permeability test was carried out to investigate the reservoir response in terms of recovery efficiency hence residual oil saturation, when flooding the reservoir with waters having different salinity ratios. Results showed an increase in recovery efficiency for all the tested samples, on applying the low salinity water injection, where all the relative permeability curves displayed wettability modification/alteration toward water wetness properties

Miocene reservoir rocks: pore throat size distribution as a strong controller on petrophysical attributes is a reflection of facies change

Abstract Pore throat size distribution (PSD) is considered a finger print for each rock type and has strong effects on many petrophysical parameters, so a comparative study was done on irregular subsurface rock samples that belong to Kareem and Rudeis Formations of middle and early Miocene, respectively. These samples were collected from San El-Hagar-1 well which is located to the East of the Nile Delta to show the effect of the different lithologies on pore throat size distribution and hence many related reservoir parameters such as displacement pressure, macroporosity, microporosity, mean hydraulic radius and permeability distribution function (PDF). For achieving the previous purpose, helium porosity and capillary pressure by mercury injection were carried out. Permeability measurements were canceled due to the non-cylindrical irregular nature of the tested samples. Porosity showed a great difference between the results of the samples of the two formations. Capillary pressure results showed the presence of characterized pore throat size distribution and hence capillary pressure-derived parameters for samples of each formation. PDF showed that samples of Kareem Fm. have better reservoir flow properties (permeability) in contrast to those of Rudeis Fm. which have tight reservoir flow properties. In addition, petrographical study through thin sections and scanning electron microscope displayed the presence of two facies which are feldspathic quartz wacke (sandstone facies) of Kareem Fm. and bioclastic sandy wackestone (calcareous facies) of Rudeis Fm. All results were consistent and confirmed the influence of facies change on PSD and hence the reservoir parameters

Lower Paleozoic reservoir zonation into different flow units using turbulence factor and their relations to diagenesis

Abstract Surface Lower Paleozoic sandstone samples were collected from southeast central Sinai. These samples subjected to petrophysical measurements which are porosity and permeability. It is known that turbulence factor (β) is a good tool to describe turbulent flow level, hence it was used to detect the flow properties distribution that corresponds to the nature of the pore system, so turbulence factor (β) was correlated with porosity, permeability, and reservoir quality index using many equations, where porosity correlation shows the presence of three groups having same porosity ranges but correspond to different values of turbulence factor, this refers to the presence of different flow zones. Porosity–permeability relation confirmed also the presence of similar three groups, where there are nearly same porosity ranges but with different permeability values. Consequently, samples with nearly same porosity values and representing the three groups were selected for capillary pressure by mercury injection to reveal the flow properties that characterize each group. Capillary pressure results confirmed that each group has their own pore system and flow regime. Petrography was done by optical polarizing microscope (OPM) through thin sections. The results indicated that the studied sandstone is composed mainly of quartz arenite microfacies of fine, angular to subrounded, moderately well sorted monocrystalline quartz grains. There are several features indicating that the investigated sandstones have been subjected to diagenesis processes. Diagenetic events identified in these sandstones include considerable compaction during burial diagenesis at higher temperatures and low flow rates, cementation by clay minerals and iron oxides, dissolution and alteration of unstable clastic grains, and tectonically induced grain fracturing. Unstable clastic grains like feldspars suffered considerable alteration to kaolinite when exposed to meteoric water of low ionic strength near the surface. The distribution of this kaolinite rather than the post-depositional iron oxides in pores of the studied sandstone leaded to differentiating these sandstones into three different flow units. This zonation indicates that the turbulence properties are proportional to the diagenetic effects inside the pores

Evaluation of the shale beds within Alam El Bueib Formation as an unconventional reservoir, Western Desert, Egypt

Abstract Within Alam El Bueib Formation (AEB), thin sandstone beds of approximately 15.24 m (~50 ft) total thickness, are considered to be the main conventional hydrocarbon-producing zone in the Western Desert. However, the shale intervals within the AEB can be an unconventional reservoir target. In this study, we focus on evaluating these shale units through geochemical analysis, to determine the total carbon, total sulfur, total organic carbon (TOC), and Rock–Eval pyrolysis. TOC is an essential property needed to determine the productive shale gas play. Total organic carbon combined with other geochemical data is important in evaluating the potential of shale gas reservoirs as it is related to the amount of kerogen, the produced hydrocarbon content. The TOC in the studied samples indicates poor to very good organic continent, while the hydrocarbon potentiality (S1 and S2) indicates poor source potential. The hydrogen index reflected kerogen type III/II. These data indicate that AEB Formation may be considered as a good source for generating hydrocarbons (mainly gas with minor amount of oil). The maturation evaluated by using “Tmax” indicates immature to marginally mature source rock, and production index ‘‘PI” represents oil and gas production in case of maturation

Petrography, mineralogy and calcareous nanofossils of Shepses po ptah tomb, Titi and Unis pyramids building stones

907-915Petrographical, mineralogical, calcareous nanofossil studies have been achieved to through light on the geologic sources and unit age of the sarcophagus rock and the burial chamber casing wall rock of Shepses po ptah tomb and correlate them with rock samples from Titi and Unis pyramids in the Saqqara area of Egypt, which are hewn within Upper Eocene (Maadi Formation) sediments. The samples were analyzed by polarizing microscope, X-rays diffraction (XRD) techniques; along with calcareous nanofossil were examined using the microscope. The studies reveal that the quality of the sarcophagus and the burial chamber casing wall rock in Shepses po ptah tomb is particularly good pure limestone. The sarcophagus is composed of slightly dolomitic wackestone microfacies while the burial chamber casing wall and Titi pyramid are of grainstone microfacies. On the other hand Unis building stones composed mainly of sandy wackestone types. The XRD analysis of indicate that these rocks composed mainly of calcite in addition to little dolomite. The rock texture, mineralogical composition and diagenetic processes contribute, to a great extent, to source rock composition. The composition of the studied rocks do not show clear interaction between the exogenic (surrounding climate) and endogenic (related to the nature of the rock types) conditions.over the thousands of years since their construction. The calcareous nanofossil of sarcophagus, burial chamber casing wall and Titi pyramid show (NP16),which is assigned Middle Eocene (Lutetian )with age about 41.94 (ma), while Unis pyramid building stones show.(NP11) which is assigned to Early Eocene (ypresian) with age 54.17(ma)

Upper Cretaceous Duwi Formation shale’s oil potentiality Safaga-Quseir, Red Sea, Egypt

Duwi Formation shale deposits at Safaga – Quseir area were assessed by rock eval pyrolysis for its shale oil potentiality. The studied shale’s organic matter are mainly of type I, type II, mixed type I/II in addition to some of type III. The studied shale is described as very good source rock with total organic carbon (TOC > 2 wt%). The kerogen maturation in the studied samples is immature according to PI and Tmax. Extracted shale oil from the studied samples as bitumen was fractionated by liquid chromatography (LG) into saturated hydrocarbon, aromatic hydrocarbon, resin and asphaltene. The saturated hydrocarbon was described by gas chromatography (GC), the pristane/phytane, isoprenoids/n-alkane and CPI ratios show that, samples were deposited in marine environment with some input of terrestrial environment and are characterized by immature level.The X-Ray Diffraction (XRD) analysis for the studied shale samples show their bulk minerals are mainly quartz, calcite, dolomite, gypsum, hematite and pyrite in addition to apatite and fluorapatite. While their clay minerals are mainly smectite and kaolinite. The chemical composition of the studied samples showed high concentration of trace elements such as Co, Cr, Cu, Ni, V and Zn which in turn through more lights on the depositional environment of the organic matter. Keywords: Safaga, Quseir, Duwi Formation, Oil shale, Rock-Eval pyrolysis, Gas chromatograph