Possible new method to discriminate effective source rocks in petroliferous basins: A case study in the Tazhong area, Tarim Basin

Abstract

Sediments with organic matter content (total organic carbon) TOC ≤ 0.5% which can act as effective source rocks are critical and challenging in the field of petroleum geology. A new method is proposed through a case study to identify and evaluate the effective source rocks, which is applied to study the changing characteristic of hydrocarbon-generation potential index with depth. The burial depth corresponding to the beginning of hydrocarbon-generation potential index reduction represents the hydrocarbon expulsion threshold in source rocks. Then, new identification standards are established for discrimination of effective source rocks of Middle–Upper Ordovician in Tarim Basin. The critical value of TOC for effective source rocks change with their burial depth: the TOC > 0.5% with source rock depth > 4000 m, TOC > 0.4% with depth >4500 m, TOC > 0.3% with depth > 5000 m, TOC > 0.2% with depth >5500 m. Based on the new criteria, effective source rocks in the Middle–Upper Ordovician are identified and their total potential hydrocarbon resources is evaluated, reaches 0.68 × 109 t in the Tazhong area, which is 65.4% higher than that of previous studies and consistent with the exploration result. Thus, this new method is of significance to resource evaluation and can be applied in the carbonate source rocks and mudstone source rocks with high degree of exploration.

Geochemical Evaluation of Paleocene Source Rocks in the Kohat Sub-Basin, Pakistan

“…A lower TOC (<0.5%) may produce and be a possible source rock and act as a secondary source rock. 61 Hangu formation having HI value less than 200 mostly falls in the category of Type III. Lockhart Limestone and Patala formation having HI values in the range of less than 100−250 fall in the category of Type-III kerogen.…”

“…The TOC values at present do not reflect the original or total organic matter because over time and with the increase in thermal maturity, kerogen is converted into hydrocarbons and the value of TOC decreases. A lower TOC (<0.5%) may produce and be a possible source rock and act as a secondary source rock …”

“…A lower TOC (<0.5%) may produce and be a possible source rock and act as a secondary source rock. 61 …”

Reservoir characteristics in the Cretaceous volcanic rocks of Songliao Basin, China: A case of dynamics and evolution of the volcano-porosity and diagenesis

“…In this study area, the lithology of the volcanic rocks includes basalt, andesite, dacite, rhyolite, tuff, and volcanic breccia (Wang et al., 2007) (Figure 2). Porosity was changed from 1.9% to 10.8%, while the permeability varied from 0.01 × 10 −3 μm 2 to 0.87 × 10 −3 μm 2 (Wang et al., 2008).…”

Hydrothermal injection breccia with organic carbon and nitrogen in the fossil hydrothermal system of Harghita Bãi, East Carpathians, Romania: an example of magmatic and non-magmatic element mobility in the upper continental crust

“…Thus, unexplained exotic hydrocarbon reservoirs have been found in volcanic rocks distributed along the Pacific Rim, Africa and Central Asia (Schutter, 2003b) in the last 20 years. According to Schutter (2003a), more than 100 volcanic gas fields with proven reserves have been found in various countries such as the United States (Gries et al 1997), Venezuela (Rohrman, 2007), Argentina (Sruoga & Rubinstein, 2007), Japan (Sakata et al 1997;Tomarua et al 2009) and China, where favourable targets for natural gas exploration were delimited in volcanic rocks from China (Feng, 2008;Wang et al 2008).…”