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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.

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.

Zhang Y.,China University of Geosciences | Jia C.,Chinese Petroleum Society | Zhao Z.,Chinese Petroleum Society | Jiang Z.,China University of Geosciences | Xu J.,China University of Geosciences
Acta Geologica Sinica | Year: 2012

The Liangshan and Qixia formations in the Sichuan Basin of central China were formed in the earlier middle Permian. Based on outcrop observation of the Changjianggou section at Shangsi, Guangyuan region and 3 rd-order sequence division in typical drillings, one-dimensional spectrum analysis has been used to choose the better curve between the natural gamma ray spectrometry log(ln (Th/K)) in Well-Long17 and the gamma ray log(GR) in Well-Wujia1, respectively, for identifying Milankovitch cycles in Sequence PSQ1 which comprises the Liangshan and Qixia formations, and then to identify the variation in the Milankovitch cycle sequences. On this basis, the system tract and 4 th-order sequence interfaces in Sequence PSQ1 were found via two-dimensional spectral analysis and digital filtering. Finally, a high-frequency sequence division program was established. Among these cycles, long eccentricity (413.0 ka) and short eccentricity (123.0 ka) are the most unambiguous, and they are separately the major control factors in forming 4 th-order (parasequence sets) and 5 th-order (parasequences) sequences, with the average thicknesses corresponding to the main cycles being 11.47 m and 3.32 m in Well-Long17, and 14.21 m and 3.79 m in Well-Wujia1, respectively. In other words, the deposition rate in the beach subfacies is faster than that of the inner ramp facies. The ln(Th/K) curve is more sensitive than the GR as the index of relatively ancient water depth in carbonate deposition. One-dimensional spectrum analysis of ln(Th/K) curve could distinguish the Milankovitch cycle sequences that arose from the Precession cycle (20.90 ka), with a much higher credibility. Sequence PSQ1 in Well-Long17 contains 10 4 th-order sequences, and the growth span of Sequence PSQ1 consisting of the Liangshan and Qixia formations is about 4.13 Ma. The single deposition thickness of the long eccentricity cycle sequence has the characteristics of thinning and then thickening in the two-dimensional spectrum, which could be used to identify the system tract interface of the 3 rd-order sequence. The precession sequence thickness remains stationary. As a result, the early deposition rate in the mid-Permian of the Sichuan basin was very slow, remaining nearly stationary, and this reflects a sustained depositional environment. Whole-rock carbon and oxygen isotope curves could also prove this point Milankovitch cycle sequence studies provide a basis for paleoenvironmental analysis and, as such, can be used to analyze ancient climate change, calculate deposition rate and deposition time, and carry out fine isochronous stratigraphic correlation. © 2012 Geological Society of China.

Zhao Z.,Chinese Petroleum Society | Zhao Z.,Petrochina | Luo J.,402 Geological Team | Zhang Y.,China University of Geosciences | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2011

Through sedimentary facies observations on coring and outcrop samples, seismic sequence interpretations and seismic facies analyses, the present paper, integrated regional geological data of ophiolite-melange belts with those of plate tectonic evolution, firstly compiled 4 lithofacies paleogeography maps of Cambrian sequences in the Tarim Basin under the third sequences stratigraphic framework. We discovered 3 Cambrian isolated carbonate platforms (the western Tarim platform, western Lop Nor platform and Kuruktag platform) and some inter-platform deepwater depositional regions within the Tarim plate and suggested that Cambrian deepwater basinal-facies depositional regions distributed in southwestern Tarim might be chief source rocks of marine oil-gas reservoirs represented by the Hetianhe gas field, this point of view is very important to marine oil & gas exploration in the Tarim Basin, especially in the SW Tarim area. The continental riftogenesis of the northern margin of the Tarim plate occurred initially in Early Sinian and Early Cambrian, and the Sinian-Cambrian pull-apart structural condition controlled the formation of several isolated carbonate platforms and inter-platform deepwater depositional areas within the Tarim plate. From Early Cambrian to Late Cambrian, these isolated carbonate platforms represented by the western Tarim platform expanded universally due to progradation and aggradation though the paleogeographic framework as a whole did not change much within the Tarim plate, meanwhile, changes occurred in types and superimposition patterns of platform margins in different time-space domains, namely ramp to feebly rimmed platform margins were dominant in Early Cambrian, while feebly rimmed to rimmed platform margins became dominant in Middle-Late Cambrian.

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.

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.

Wei X.,Petrochina | Jia C.,Chinese Petroleum Society | Zhu Y.,Petrochina | Guo Q.,Petrochina | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2010

The aborted oceanic basin is a special basin generated during basin evolution from epicontinental rift to ocean basin. This kind of basin is characterized by formation of the oceanic basement, which stopped expanding later and switched to depression. The tectonic evolution period of this type basin includes 3 stages of epicontinental fault subsidence, oceanic basement expanding and depression. The formation generated during the period of epicontinental fault subsidence belongs to the continental facies distributed near the margin of the basin. The formation formed during the period of oceanic basement expanding belongs to the hemipelagic or pelagic deposit, which passively overlapped upon the prior layer from the brim to expending center of the basin. The formation formed during the period of depression belongs to deep-sea plain deposit and deep-sea mudstone. The aborted oceanic basin has higher geothermal heat flow and gradient, which are favorable to the organic material thermal evolution and result in the smaller hydrocarbon-generating threshold value. The aborted oceanic basin might become significant province of deep-water hydrocarbon exploration activity, because of good matching of source rock, reservoir bed and capping formation.

Zheng M.,Petrochina | Jia C.,Chinese Petroleum Society | Feng Z.,PetroChina Daqing Oilfield Company Ltd | Li X.,Petrochina | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2010

The foreland basins of the central and western region of China are rich in oil and gas resources, so strengthen the research on the new exploration regions of foreland basin is important. Oil and gas exploration in foreland basins is more concentrated in six districts of the extrusion anticline structure, lithologic traps, reef, drape anticline, stratigraphic traps and fault traps. The extrusion anticline structure is the major style, but its exploration is more and more difficult. Reference to the important great discoveries in global exploration and combined with the new trend of exploration breakthrough in foreland basins domain of China, this paper brings forward three potential replacement regions of hydrocarbon reserves, which is "the concealed sequences" under the metamorphic rock thrust nappe of orogenic belt, "the footwall thrust clamping piece structures" of the foreland thrust belts, the deep formation of the foreland depression. The three potential replacement regions of hydrocarbon reserves have biggish hydrocarbon exploration potential and have the same petroleum geological conditions to the foreland depression sequences. "The concealed sequences" under the metamorphic rock thrust nappe of orogenic belt developed the basin-forming period sedimentary sequence. "The footwall thrust clamping piece structures" of the foreland thrust belts have favorable reservoir and seal condition. The deep formation of the foreland depression provided high quality source rock and reservoir. Exploration practices approved that these three potential replacement regions of hydrocarbon reserves have widely exploration prospect.

Wang X.,China University of Petroleum - Beijing | Wang X.,Petrochina | Jia C.,Chinese Petroleum Society | Meng Q.,Petrochina | Zhang G.,Petrochina
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2011

On the basis of seismic, drilling, logging and lab analysis data of the Tanan Sag, Tamsag Basin, analyses of main controlling factors of the formation and distribution of Nantun Formation lithologic reservoirs in its abrupt slope zone indicated that premium source rocks of the Nantun Formation developed in the TST during the primary rifting phase controlled oil-bearing intervals of lithologic reservoirs that were readily formed both in LST sandstones developed beneath the source rock and in TST sandstones developed synchronously with the source rock. The abrupt slope zone of the Tanan Sag obviously showed a character of "a sedimentary source controlled by cleughs" and "a sand distribution controlled by ramps", namely multi-orientation cleughs formed during activities of the synsedimentary fault system dominated the source of sediments as well as the strike of fans, while the ramp system formed by the combination of various synsedimentary faults controlled the spreading pattern of fans as well as the distribution of sand bodies. The combination was characterized by comb-like and parallel scattering structures on a plane and fault-cliff and fault-terrace structures in a profile. The mid-fan sub-facies of nearshore subaqueous fans showed a good reservoir potential and sandstones in sedimentary microfacies of braided channels were the most advantageous to oil accumulations. Secondary pores formed by dissolution of tuffaceous components in reservoir rocks could effectively improve the storage of reservoir sandstones.

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.

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