Grain-coating clays control on reservoir quality of Miqrat Formation sandstones in Huqf region, Central Oman

The economy of the Sultanate of Oman is noticeably reliant on hydrocarbon revenues. The Paleozoic sandstone reservoirs in the Sultanate of Oman are important hydrocarbon-producing plays and hold commercial hydrocarbon accumulations. However, Miqrat Formation is considered one of the important Paleozoic hydrocarbon reservoirs in the Sultanate of Oman. The subsurface-equivalent Miqrat Formation is largely distributed throughout the Interior Oman Salt Basins, holding profitable hydrocarbon accumulations. The hydrocarbon initial in place (HIIP) and the recoverable amounts in Miqrat Formation sandstone reservoirs vary considerably from one to another field. Such variation is governed by the amount and distribution of porosity and permeability. However, the amount and distribution of porosity and permeability are mostly controlled by the type and distribution of diagenetic minerals. Among various types of diagenetic alterations, grain-coating clays are common in sandstones and have strong control on the quality of deeply-buried reservoirs. The proposed project, representing phase II, aims to study the control of grain-coating clays on the reservoir quality of the outcropped-equivalent Miqrat Formation sandstones in the Huqf region of Central Oman. The grain-coating clays are common diagenetic minerals in Miqrat reservoirs and have a profound control on porosity and permeability. Prediction of the types and distribution of grain-coating clays and their control on amounts and distributions of porosity and permeability will ultimately help in better planning for the efficient exploration, drilling, production, and enhanced recovery strategies. Such better planning will profoundly reduce the geologic and economic risk. It is reported that grain-coating clays can affect positively and negatively on reservoir quality. However, grain-coating clays usually prevent cementation by quartz and feldspar overgrowths. Inhibition of cementation by quartz and feldspar overgrowths helps in porosity preservation in deeply-buried sandstone reservoirs. The origin, type, texture, and distribution of the grain-coating clays and control on the porosity and permeability amounts and distribution of Miqrat reservoirs are still poorly explored. Therefore, in this project, we seek to test how the depositional process, notably tidal hydrodynamic pumps, in addition to grain size and climate condition, controls the clay incorporation into the sand and its type, texture, thickness, and distribution. The accessible Miqrat Formation outcrops in the Huqf region of Central Oman provide an excellent opportunity to carry out this project based on petrographical and mineralogical investigations using the conventional optical microscope, modal composition, Scanning Electron Microscope (SEM) equipped with a Dispersed Energy Spectrometer (EDS), and X-Ray Diffraction (XRD), micro-XRF mapping, and stable isotopes of the clay coats for constructing a predictive model for reservoir quality distribution.