GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 71-4
Presentation Time: 2:30 PM


GONG, Shuangyi1, JIANG, Fujie2, WANG, Tao1 and ZHAO, Zhao1, (1)College of Geosciences, China University of Petroleum (Beijing), Beijing, 102249, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102249, China, (2)College of Geosciences , China University of Petroleum, Beijing, State Key Laboratory of Petroleum Resources and Prospecting, Beijing, 102249, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102249, China

Mesozoic-Cenozoic Salt Lake basins are widely developed in China, and saliferous shale strata rich in organic matter is abundant. The study area Dongpu depression in Bohai bay basin is a typical terrestrial saline lacustrine depression in China. Previous exploration practice showed the important controlling effect of saliferous shale on the source rock distribution and characteristics (compared with general shale strata, saliferous shale strata is characterized by higher organic matter abundance and oil-prone organic matter). However, studies on the pore characteristics and controlling factors under the participation of evaporite minerals in saliferous shale strata are still lacking.

In the study, 9 samples with different contents of evaporate minerals were selected from Es3 member in Dongpu depression. Geochemical experiments and pore structures were investigated using argon milling FE-SEM observations and N2 adsorption analysis. The results show that TOC contents of saliferous shale range from 0.10 % to 7.78 % and their Ro values are between 0.41% and 2.67%. All the samples are clay rich, ranging from 24%-64.9%, quartz, feldspar and carbonate are well developed, evaporate minerals including halite, gypsum and anhydrite can also be found in the samples, ranging from 0.6% to 7.2%, 2.52 % in average. Interparticle, intraparticle and OM pores are well developed with pore sizes ranging from several to several hundred nanometers, and micron meter microfractures can also be found.

The specific surface area (SSA) varies from 4.035 m2/g to 28.598 m2/g, and pore volume (PV) is from 0.05 cm3/g to 0.062 cm3/g. TOC, carbonate and brittle mineral content is negatively correlated with SSA, while RO and clay mineral content is positively correlated with SSA. TOC and carbonate mineral content have a positive relationship with PV, while a negative correlation exists between RO, brittle mineral contents, clay mineral contents and PV. When content of evaporite is less than 3%, evaporite has a good positive correlation with SSA and PV. However, when the content of evaporate is larger than 3%, it may constrain the development of pores. More work needs to be done when sample capacity gets larger and quantitative correlation should be studied.

Key words: Dongpu depression; Saliferous shale;Pore characteristics; Controlling factors