Petroleum production in the Rio del Rey Basin,which is an extension of the Niger Delta of Nigeria into Cameroon,has been limited to the Tertiary offshore portion since the late 1970s.Owing to dedlining reserves in thi...Petroleum production in the Rio del Rey Basin,which is an extension of the Niger Delta of Nigeria into Cameroon,has been limited to the Tertiary offshore portion since the late 1970s.Owing to dedlining reserves in this offshore portion,the onshore Cretaceous portion of the basin attracted significant attention in the last decade.In the present study.shales from outcrops in the onshore portion of the basin were analyzed to evaluate their potential as source rocks,assess hydrocarbon generation,and highlight their signifcance for exploration.Outcrop observations,total organic carbon(TOC)measure-ments,and Rock Eval pyrolysis were used to generate data for these investigations.Rock-eval S2 values(0.42-3 mg HC/g rock)based on measured present-day TOC values(0.58-2.44 wtx)of the shales studied signify poor to fair source rock potentials,whereas calculated S2 values(1.74-8.19 mg HC/g rock)based on estimated original TOC values(0.67-2.87 wt%)produced fair to good source rocks containing Type Ⅱ/Ⅲ kerogen,which were transformed by maturity to the present-day Type Ⅲ/Ⅳ kerogen.Maturity of the samples based on Tmax values varying between 439 and 471℃are equivalent to maturity values ranging between 0.74% R_(r) and 1.32% R_(r), and these represent the peak oil to condensate/wet gas zones of hy-drocarbon generation.These results demonstrate that mature source rocks are present in the onshore part of the Rio del Rey Basin,and thus,it is suitable for petroleum exploration.展开更多
As a new technology of analyzing crude oils, comprehensive two-dimensional gas chromatography cou- pled with time-of-flight mass spectrometry （GCxGC- TOFMS） has received much research attention. Here we present a ca...As a new technology of analyzing crude oils, comprehensive two-dimensional gas chromatography cou- pled with time-of-flight mass spectrometry （GCxGC- TOFMS） has received much research attention. Here we present a case study in the Junggar Basin of NW China. Results show that the hydrocarbons, including saturates and aromatics, were all well-separated without large co- elution, which cannot be realized by conventional one-dimensional GC-MS. The GC×GC technique is especially effective for analyzing aromatics and low-to-middle- molecular-weight hydrocarbons, such as diamondoids. The geochemical characteristics of crude oils in the study area were investigated through geochemical parameters extracted by GC×GC-TOFMS, improving upon the understanding obtained by GC-MS. Thus, the work here represents a new successful application of GC×GC- TOFMS, showing its broad usefulness in petroleum geochemistry.展开更多
The central region of the southern Junggar basin （Northwest China） is a key exploration target in this petroliferous basin. As there are four sets of potential source rocks （e.g., Permian, Jurassic, Cretaceous and ...The central region of the southern Junggar basin （Northwest China） is a key exploration target in this petroliferous basin. As there are four sets of potential source rocks （e.g., Permian, Jurassic, Cretaceous and Paleogene sequences）, petroleum migration and accumulation are likely complex. This study represents an attempt to understand this complexity in order to provide fundamental information for future regional petroleum exploration and geological studies. Based on petroleum geology and geochemistry, it is implied that there are mainly three types of hydrocarbons, including Cretaceous- and Paleogene-sourced oils （with the former being dominant） and Jurassic-sourced gas. The petroleum migration and accumulation mainly cover three stages. The first stage is the late period of the Early Pleistocene, in which the Cretaceous-sourced oils migrate and accumulate. Then, in the second stage （from the late period of the Middle Pleistocene to the early period of the Late Pleistocene）, the Cretaceous- sourced oils, together with the Paleogene-sourced oils, participate in the migration and accumulation. At last, in the end of the Late Pleistocene, large quantities of oils remigrate and accumulate, with gas （especially Jurassic- sourced gas） migrating along faults to accumulate. Thus, petroleum charge events in the area are complex, reflecting the control of complex tectonic evolution on petroleum migration and accumulation.展开更多
文摘Petroleum production in the Rio del Rey Basin,which is an extension of the Niger Delta of Nigeria into Cameroon,has been limited to the Tertiary offshore portion since the late 1970s.Owing to dedlining reserves in this offshore portion,the onshore Cretaceous portion of the basin attracted significant attention in the last decade.In the present study.shales from outcrops in the onshore portion of the basin were analyzed to evaluate their potential as source rocks,assess hydrocarbon generation,and highlight their signifcance for exploration.Outcrop observations,total organic carbon(TOC)measure-ments,and Rock Eval pyrolysis were used to generate data for these investigations.Rock-eval S2 values(0.42-3 mg HC/g rock)based on measured present-day TOC values(0.58-2.44 wtx)of the shales studied signify poor to fair source rock potentials,whereas calculated S2 values(1.74-8.19 mg HC/g rock)based on estimated original TOC values(0.67-2.87 wt%)produced fair to good source rocks containing Type Ⅱ/Ⅲ kerogen,which were transformed by maturity to the present-day Type Ⅲ/Ⅳ kerogen.Maturity of the samples based on Tmax values varying between 439 and 471℃are equivalent to maturity values ranging between 0.74% R_(r) and 1.32% R_(r), and these represent the peak oil to condensate/wet gas zones of hy-drocarbon generation.These results demonstrate that mature source rocks are present in the onshore part of the Rio del Rey Basin,and thus,it is suitable for petroleum exploration.
基金funded by the Major State Basic Research Development Program of China(973 project,Grant No.2012CB214803)National Science and Technology Major Project of China(Grant No. 2016ZX05003-005)National Natural Science Foundation of China(Grant Nos.41322017 and 41472100)
文摘As a new technology of analyzing crude oils, comprehensive two-dimensional gas chromatography cou- pled with time-of-flight mass spectrometry （GCxGC- TOFMS） has received much research attention. Here we present a case study in the Junggar Basin of NW China. Results show that the hydrocarbons, including saturates and aromatics, were all well-separated without large co- elution, which cannot be realized by conventional one-dimensional GC-MS. The GC×GC technique is especially effective for analyzing aromatics and low-to-middle- molecular-weight hydrocarbons, such as diamondoids. The geochemical characteristics of crude oils in the study area were investigated through geochemical parameters extracted by GC×GC-TOFMS, improving upon the understanding obtained by GC-MS. Thus, the work here represents a new successful application of GC×GC- TOFMS, showing its broad usefulness in petroleum geochemistry.
基金supported by the National Natural Science Foundation of China (Nos. 40602014, 40872086)
文摘The central region of the southern Junggar basin （Northwest China） is a key exploration target in this petroliferous basin. As there are four sets of potential source rocks （e.g., Permian, Jurassic, Cretaceous and Paleogene sequences）, petroleum migration and accumulation are likely complex. This study represents an attempt to understand this complexity in order to provide fundamental information for future regional petroleum exploration and geological studies. Based on petroleum geology and geochemistry, it is implied that there are mainly three types of hydrocarbons, including Cretaceous- and Paleogene-sourced oils （with the former being dominant） and Jurassic-sourced gas. The petroleum migration and accumulation mainly cover three stages. The first stage is the late period of the Early Pleistocene, in which the Cretaceous-sourced oils migrate and accumulate. Then, in the second stage （from the late period of the Middle Pleistocene to the early period of the Late Pleistocene）, the Cretaceous- sourced oils, together with the Paleogene-sourced oils, participate in the migration and accumulation. At last, in the end of the Late Pleistocene, large quantities of oils remigrate and accumulate, with gas （especially Jurassic- sourced gas） migrating along faults to accumulate. Thus, petroleum charge events in the area are complex, reflecting the control of complex tectonic evolution on petroleum migration and accumulation.
