No abstract

Whether the emplacement of petroleum in sandstone reservoirs can preserve porosity during burial remains controversial. In the Kessog Field, UK Central North Sea, average porosities of the crestal sections of the fluvial-deltaic Pentland Formation reservoir can exceed 25 % despite burial to 4 km or more. The predicted porosity for the reservoir at this depth is only around 14 % based on regional data. Oil saturation data, thin-section point counts, grain-size and sorting measurements, reservoir pressure, and SEM images were combined to analyze the cause of the high reservoir porosity. Petroleum emplacement preventing cementation is the most likely mechanism for porosity preservation. Facies variation is not responsible, as the high-porosity sandstones from the crestal well are, in terms of average grain-size (fine-grained) and sorting coefficient (moderately well-sorted), nearly the same as the lower porosity sandstones from the flanks of the field (average porosity 13 -15%). Other potential porosity-preservation mechanisms, such as overpressure, grain-coats and feldspar dissolution can be discounted. The sandstones with high oil saturations are characterized by: 1) most porosity being primary as opposed to secondary; 2) there being 2 -5 % less quartz cement than in the water-saturated sandstones; 3) there being 2 -3 % more Kfeldspar and 2 -6 % less kaolin than the water-saturated counterparts. This study demonstrates that petroleum emplacement can effectively inhibit quartz cementation and K-feldspar transformation to kaolin in sandstone reservoirs.

Carbon dioxide (CO2) emissions from China’s cement production process have increased rapidly in recent decades, comprising the second-largest source of CO2 emissions in the country, next only to fossil fuel combustion. However, there used to lack high-quality data to estimate provincial process-related CO2 emissions from the cement industry of China. It has been recognised that many previous publications have adopted cement-based accounting methods or national average emission factors to estimate them. This study assembles fundamental provincial clinker production data and provincial clinker emission factors from multiple official statistics sources, following the Intergovernmental Panel on Climate Change (IPCC) methodology (A clinker-based estimation methodology), to develop a high-quality panel dataset of China’s provincial process-related cement emissions during 1993–2019. In 2019, the gross cement process emissions of China amounted to 818.2 Mt CO2, and the cumulative emissions between 1993–2019 were estimated to be approximately 12.5 Gt CO2. There are significant differences in provincial process-related CO2 emissions. The dataset is crucial to provincial cement process emission characterisation and emissions reduction policy-making in China.