Diagenetic controls on reservoir quality of tight sandstone: A case study of the Upper Triassic Yanchang formation Chang 7 sandstones, Ordos Basin, China

Abstract

Through a range of petrological techniques, the petrology, diagenesis, pore characteristics, and controlling factors on the regional variations of reservoir quality of the Chang 7 sandstones were studied. These sandstones, mainly arkoses, lithic arkoses, and feldspathic litharenites, were deposited in a delta front and turbidites in semi-deep to deep lacustrine. The detrital constituents were controlled by the provenance and sedimentary condition, which resulted in a spatially variable composition; e.g., high biotite and feldspar contents in the northeast (NE) of the study area, and high contents of rock fragments, especially dolomite, matrix, and quartz in the southwest (SW). Diagenesis includes intense mechanical compaction, cementation, and dissolution of unstable minerals. Diagenetic minerals which were derived internally include quartz, ankerite, ferrous calcite, albite, illite, kaolinite, and chlorite. Thus the original sandstone composition hadfirm control over the development and distribution of cement. Mechanical compaction and late-stage cementations contribute to the porosity loss of sandstones of Chang7 member. The dissolution porosity in major sandstone, slightly higher than primary porosity is principally dependent on the accessibility of acid fluid. The high content of plastic component facilitated the reduction of primary porosity and limited the mineral dissolution. The best reservoir sandstones are found in W, and partly from NE, M districts, with porosity are primary. The relatively high textural maturity of these sandstones reduces the impact of compaction on primary pores, and commonly existed chlorite rims limited the precipitation of pore filling quartz and carbonate cementation in late stage. A través de una gama de técnicas petrológicas se estudió la petrología, la diagénesis, las características de poro y los factores que controlan las variaciones regionales de la calidad del yacimiento de las areniscas Chang 7. Estas areniscas, principalmente arcosas, arcosas líticas y arenitas líticas feldespáticas, se depositaron en un frente deltáico mientras las turbiditas se depositaron en ambientes lacustres profundos y semi-profundos. Los componentes detríticos dependen de la procedencia y la condición sedimentaria, lo que resultó en una composición variable en el espacio; por ejemplo, altos contenidos de biotita y feldespato en el noreste (NE) del área de estudio, y altos contenidos de fragmentos de roca, especialmente dolomita, matriz y cuarzo en el suroeste (SW). La diagénesis incluye compactación mecánica intensa, cementación y disolución de minerales inestables. Los minerales diagenéticos que se derivaron internamente incluyen cuarzo, ankerita, calcita ferrosa, albita, illita, caolinita y clorita. Por lo tanto, la composición original de arenisca tenía un firme control sobre el desarrollo y la distribución del cemento. La compactación mecánica y las cementaciones de la última etapa contribuyen a la pérdida de porosidad de las areniscas del miembro Chang7. La porosidad de disolución en la pi...

Isorhamnetin in Tsoong blocks Hsp70 expression to promote apoptosis of colon cancer cells

“…The chemical reference standards were purchased from BioBioPha and the American-based Sigma-Aldrich Corporation, and are dissolved in either dimethyl sulfoxide (DMSO) or methanol and stored at −20 °C before use. The working standards of the reference standards were diluted to different concentration gradients with 70% methanol before use for mass spectrometry analysis (Zhu et al, 2018, Alvi et al, 2018).…”