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Beijing, China

Xianying L.,Petrochina | Zongju Z.,Chinese Petroleum Society | Yuanlin M.,Northeast Petroleum University
Toxicological and Environmental Chemistry | Year: 2015

The composition and distribution of n-alkanes carbon numbers reflect the source of kerogenic organic matter, sedimentary environment, and maturity of the rocks. The comparison results of the n-alkanes GC (gas chromatography) chromatograms in the Tazhong Low Uplift show that the n-alkanes of the source rocks in Upper Ordovician display an odd carbon number predominance. At the same time, Cambrian–Lower Ordovician exhibit an even carbon number predominance. The correlation between oil and source rock illustrates that crude oils in the fields of well TZ10-12 and well TZ24 stem from the Upper Ordovician source rocks. The origins of the crude oils in the fields of well TZ161-162 and well TZ45 are Cambrian–Lower Ordovician. The strata corresponding to the crude oils with odd/even carbon number predominance match the oil–source rock correlation. Thus, the characteristics of odd/even carbon number predominance in n-alkane compounds are effective for oil–source rock correlation in the Tazhong Low Uplift, Tarim Basin. © 2015 Taylor & Francis. Source

Wang Y.,Peking University | Wang Y.,Petrochina | Liu J.,Peking University | Liu J.,Petrochina | And 7 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2015

Through massive cores and thin sections observation, and according to the types and content of interstitial materials, inter-layers of Donghe sandstone in Donghe1 reservoir were classified into three categories: calcareous inter-layer, mud-calcareous inter-layer and mud inter-layer. Calcareous inter-layer, mud-calcareous inter-layer are predominant while mud-calcareous inter-layers are less developed. The formation of inter-layers is primarily controlled by carbonate cementation in the early diagenetic stage. Carbonate cements include calcite, siderite, ferrocalcite and ferrodolomite. Four phases of carbonate cements with different causes and fluid sources were identified according to the different petrographical and cathode luminescence characteristics. The first-phase cements is inter-growth or coarse flaky, iron and magnesium free calcite with low content of Fe and Mn, formed under non buried or shallow buried open oxidizing environment which is connected with seawater. Calcium originates from seawater. The second-and third-phase cements are precipitated between point-line contacted particles. Mn content is increased significantly, formed under semi closed or closed diagenetic environment. Calcium fluid is sourced from the first-phase cements or syn-sedimentary dissolution of carbonate particles. The fourth phase cements were ferro-calcite and ferro-dolomite with replacing quartz and feldspar features. The content of Fe was much higher than that of Mn. It formed under relatively deep buried reducing environment, with relevance to the dissolution of feldspar. ©, 2015, Science Press. All right reserved. Source

Chen X.,Yangtze University | Zhao W.,Petrochina | Zhang L.,Yangtze University | Zhao Z.,Chinese Petroleum Society | And 3 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

Integrated with seismic profile interpretations, Petro-mineralogic observations and geochemical analyses, the present paper proposed that dolomites in the Middle Permian Qixia Formation-Maokou Formation of the central Sichuan Basin are of a structure-controlled hydrothermal origin. The characterization of the dolomites showed that: 1) they are relatively thicker in a single layer, commonly in lenticular form, poor in lateral continuity, sometimes accompanied with developed strike-slip faults and having a "concave-down" reflection in seismic sections corresponding to dolomite intervals concerned; 2) matrix dolomites composed mainly of meso- or macro-crystalline grains have the saddle-shaped dolomite with undulatory extinction stuffed in their fractures and vugs, where a large amount of breccias with white dolomites filled between them develops, forming zebralike fabrics; and 3) homogenization temperatures of matrix and interstitial saddle-shaped dolomites are commonly 5°C higher than those of strata during dolomitization, ranging between 105.8~159.6°C and 113.2~138.6°C, respectively. In addition, they show lighter oxygen isotopes (-7.64‰~-7.95‰) and higher 87Sr/ 86Sr ratios(0.708369~0.709684). The development and distribution of structure-controlled hydrothermal dolomites are dominated by strike-slip faults. There would be a good lithologic reservoir if hydrothermal dolomites combine well with overlying tight limestones. Source

Zhao Z.,Chinese Petroleum Society | Zhou H.,Petrochina | Zhou H.,China National Petroleum Corporation | Chen X.,Yangtze University | And 4 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

Based on the sedimentological analysis of outcrops and drilling cores with seismic facies analysis, this study divided the Permian in Sichuan Basin and adjacent areas into five 3rd-order sequences, and prepared four maps of the Permian lithofacies paleogeography of Sichuan Basin and adjacent areas in the 3rd-order sequence stratigraphic framework, i.e., PSQ1(Guadalupian or Middle Permian Qixia Formation), PSQ2-PSQ3(Guadalupian Maokou Formation), PSQ4(Longtan/Wujiaping Formation, Wuchiapingian Stage of Lopingian or Upper Permian), and PSQ5(Changxing/Dalong Formation, Changhsingian Stage of Lopingian). These showed that the evolution of Permian lithofacies paleogeography in Sichuan Basin and adjacent areas was mainly controlled by the background of regional rifting tectonics and the activities of syndepositional normal faults with an overall increasing trend in the rifting activity. Carbonate ramps mainly occurred in the Guadalupian and evolved into rimmed platform in the Lopingian. The Emei mantle plume activity and basalt eruptions in the end of Guadalupian led to the formation of Kangdian oldland, which became the provenance of terrigenous clastic sediments in the southwestern Sichuan. Through the compilation of lithofacies paleogeography maps, a series of intra-platform reefs and shoals as well as intra-platform depressions was discovered. It further clarified the distribution of middle ramp facies and platform margin facies in the northern Sichuan Basin, and provided guidance for exploration of natural gas in the Permian in Sichuan Basin and adjacent areas. Based on the distribution of main hydrocarbon source rocks and the accumulation conditions, it was proposed that the favorable natural gas exploration zones of Permian carbonate reservoirs in Sichuan Basin included: (1) the dolomitized platform-margin reefs and shoals of the Lopingian around Kaijiang-Liangping basin facies; (2) the dolomitized platform margin reefs and shoals of the Lopingian along the southwest margin of Chengkou-E'xi basin facies; (3) the dolomitized middle-ramp reefs and shoals of the Guadalupian in the northern Sichuan Basin; (4) the weathering crust karst reservoirs of Maokou Formation; (5) the dolomitized intra-platform reefs and shoals of the Lopingian in Changxing Formation; and (6) the fractured hydrothermal dolomite reservoirs of the Guadalupian. Source

Wang H.,Petrochina | Chi Y.,Petrochina | Zhao Z.,Chinese Petroleum Society | Jiang Q.,Petrochina | Lu W.,Petrochina
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2013

In view of the incomplete understanding on the karst origin and distribution characteristics of paleo-landform of the Middle Permian Qixia Formation in the Sichuan Basin, we studied geological responses of its karst reservoirs thoroughly. The research indicated that Qixia interlayer karsts were formed due to the exposure and erosion of third-grade sequence boundaries and the transient exposure of high-frequency sequence interfaces of the highstand systems tract. Based on the isopach map, paleogeographic environment and hydrodynamic forces of the Qixia Formation, its top paleo-landform was divided into three second-grade geomorphic units, i.e. the middle ramp facies belt in western Sichuan, the inner-platform shoal facies belt in northeastern Sichuan and the Luzhou paleo-uplift in southern Sichuan. The sedimentary microtopographic high formed both in bioclastic beaches of the middle ramp of western Sichuan and in inner-platform shoals of northeastern Sichuan, along with the paleo-uplift and its slopes of southern Sichuan, is favorable for the development of karst reservoirs in the Qixia Formation. On the basis of this new understanding and characteristics of the hydrocarbon generating intensity of source rocks, four favorable zones were proposed for the exploration of karst reservoirs in the Qixia Formation. Source

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