Micro‐ and Nanopores in Tight Zechstein 2 Carbonate Facies From the Southern Permian Basin, Nw Europe

Abstract

The study evaluates pore systems in samples of tight Upper Permian Zechstein 2 Carbonate (Z2C) facies from widely dispersed locations in the eastern and western parts of the Southern Permian Basin, NW Europe. Samples of Z2C drill cores comprising platform to shallow‐basin deposits were examined by petrographic techniques, porosity measurement and SEM analysis, in order to acquire a better understanding of porosity development and pore microstructure. Four carbonate lithofacies were identified by core‐scale and thin‐section analyses: subtidal / intertidal planar stromatolites and thrombolites; slope facies (laminated dolo‐ and lime‐mudstones and grain‐dominated turbidites); toe‐of‐slope / lower slope facies (laminated lime mudstones with turbidite beds); and shallow‐basin (embayment) facies (laminated lime mudstones and hemipelagic deposits). Porosity ranges from 0.08% to 9.6% and is lowest in the subtidal / intertidal planar and columnar stromatolites. The highest porosities, in the slope and shallow‐basin (embayment) lithofacies, probably resulted from catagenetic processes and microbial activity. High porosity in subtidal thrombolites is related to the original pore network. SEM analyses showed that pores are present within organic matter, pyrite framboids and microfossils, and between crystals. Subtidal / intertidal planar and columnar stromatolites and thrombolites have a high proportion of nanopores, probably resulting from microbial activity. Although porosity development is a combined function of the presence of organic matter and mineral components, together with sediment fabric and fractures, it is mostly a result of the early diagenetic transformation of mineral phases, microbial activity, and evaporite and carbonate dissolution.

Surfactant-Augmented Functional Silica Nanoparticle Based Nanofluid for Enhanced Oil Recovery at High Temperature and Salinity

“…15,16 Therefore, developing suitable EOR fluids that can successfully penetrate into rocks and effectively displace oil being locked in micro-and nanopores becomes an urgent mission. 17,18 EOR, also known as tertiary recovery, mainly includes three technologies, that is, gas, thermal, and chemical injection. All of them have the capability to reduce residual oil saturation.…”

“…Global demand for oil and natural gas is increasing because of the rapid economic development worldwide. − In addition to discovering new reservoirs, enhanced oil recovery (EOR) technologies aiming at extracting more oil and gas from the known reservoirs after the primary recovery are of great importance. − In fact, EOR is more crucial in some known unconventional tight reservoirs because the current horizontal drilling and multistage hydraulic fracturing technologies can only obtain a small portion (5–10%) of the existing oil/gas . What is worse, harsh reservoir conditions including extreme temperature, pressure, and salinity bring additional challenges. , Therefore, developing suitable EOR fluids that can successfully penetrate into rocks and effectively displace oil being locked in micro- and nanopores becomes an urgent mission. , …”

Nano- to Millimeter Scale Morphology of Connected and Isolated Porosity in the Permo-Triassic Khuff Formation of Oman

“…Mercury injection capillary pressure (MICP) is a technique which determines petrophysical parameters such as porosity and pore-throat size-distribution through measuring of the intruded mercury under increasing pressures [10,11]. The advantage of MICP is its large resolution of 400 µm down to 3 nm but cannot provide any information about isolated pores.…”

Sedimentary structures of microbial carbonates in the fourth member of the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China

“…The diagenesis of microbial carbonates is closely related to their sedimentary structures. On the one hand, the sedimentary structure of microbial carbonates indicates different sedimentary environments, and the sedimentary environment and sedimentary geomorphology not only affect the types of microbial structures and the distribution scale of microbial carbonate rocks 30,34,35 , but also determine the diagenetic environment of microbial carbonates in the early diagenetic stage. It will affect the formation, transformation, scale and distribution of pores [36][37][38][39] .…”