Institute of Sedimentary Geology

Chengdu, China

Institute of Sedimentary Geology

Chengdu, China
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Cheng L.,Institute of Sedimentary Geology | Cheng L.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Cheng L.,Sinopec | Wang Y.,Institute of Sedimentary Geology | And 5 more authors.
Acta Petrologica Sinica | Year: 2013

Black shales within the Sinian (Ediacaran) to Early Paleozoic strata from Upper Yangtze region are the three high quality source rocks of Sinian to Early Paleozoic marine Lower Assemblage in South China, which are generally thought to be the result of deposition under stagnant and suboxic conditions. According to the information of sedimentary structure and biological, ecological patterns, the sedimentary environment and burial condition of these black shales are discussed. The benthonic organisms and abundant natant organisms indicate that there were, in the sedimentary environment of black shales, an oxic upper-water in where abundant organisms lived and repropagated to provide organic-rich matters for deposits, and a suboxic or dysoxic bottom-water in where the decomposition of organic-matters were weakened and/or baffled for the preservation of organic-rich matters. In addition, the sedimentary structures formed by water-energy (e. g. the ranking orientation of fossils and their fragments, the oblique bedding in nonblack-shale rocks intercalated in black shales) show that there were measure of water-energy or an periodic and intermittent hydroenergy in the bottom-water. The water-energy was able to promote the oxygenic diffusion in bottom-water for the benthonic organisms. With the increase of the water-rich muddy deposits, the oxygen-exchanging efficiency between the deposited water and sea-water was weakening to intensify the stagnation and reduction of the deposited water inner deposits. Simultaneously, the organic-rich matter (e. g. organismic corpses and excreta) buried by deposits were decaying and decomposing to advance the reduction around them, so that the organic-rich matter were preserved to form the black shales.


Chen H.,Chengdu University of Technology | Chen H.,Institute of Sedimentary Geology | Hu S.,Chengdu University of Technology | Hu S.,Institute of Sedimentary Geology | And 6 more authors.
Natural Gas Industry | Year: 2013

In addition to the successful exploration of carbonate karst reservoirs on the top of the Ordovician Majiagou Fm in the Ordos Basin, breakthroughs of gas exploration have also been made in non-karst dolomite reservoirs. Core observation, thin section authentication, physical property analysis and logging data were integrated to study the sedimentary microfacies of Ma5 5-Ma5 6 (the 5th and 6th intervals of the fifth member of the Ordovician Majiagou Fm) on the east side of the paleo-uplift of the Ordos Basin, and to analyze the features and major control factors of the non-karst dolomite reservoirs. The following findings were achieved. a. The reservoir rocks are dominated by dolarenite-dolorudites and crystalline dolomites. b. The types of reservoir space are mainly of residual intergranular pores, intercrystalline pores and dissolution pores, indicating low porosity and low permeability reservoirs with strong heterogeneity. c. Their depositional settings are restricted platform which can be further divided into several sedimentary microfacies such as tidal-front beach, dolomite-dominated tidal flat, dolomite-dominated lagoon, limestone-dominated lagoon and gypsum-dominated lagoon, etc. d. The distribution of reservoirs is significantly controlled by the tidal-front beach microfacies near the paleo-uplift and selective burial dolomitization. e. Various destructive diagenesis such as re-crystallization, cementation, compaction and pressure solution as well as filling led to the tightening of reservoirs. f. The development of fractures improves the physical properties of the dolomite reservoirs and connects the preserved isolated residual intergranular pores and dissolution pores. In summary, the burial dolomitization, along-bedding karstification and fracture modification in the tidal-front beach microfacies are the key factors controlling reservoir development, and are favorable for the development of relatively high quality dolomite reservoirs.


Xu S.L.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Xu S.L.,Institute of Sedimentary Geology | Hou M.C.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Hou M.C.,Institute of Sedimentary Geology | And 7 more authors.
Acta Petrologica Sinica | Year: 2011

In order to knowing the relationship between the uplifting of Longmenshan Orogen and the filling characteristics of western Sichuan foreland basin during Jurassic, this article detailed studied the tectonic sequence filling characteristics in western Sichuan foreland basin. According to the characteristics of three tectonic sequences with obvious deposited structures and sediment, founding that Longmenshan Qrogen segmental uplifted during Jurassic. During the stage of TSlBE, alluvial fan and delta developed in the north and south part of western Sichuan foreland basin, braided river delta developed in the middle part of western Sichuan foreland basin, this situation reflected the tectonic movement of Longmenshan Orogen was different, the south part and north part might be hard, the middle part might be kind. During the stage of TSlBW, delta and lake was the mainly setting of western Sichuan foreland basin, and the tectonic movement of Longmenshan Orogen might be kind, too. During the stage of TS2BW, alluvial fan developed in the north part and south part of western Sichuan foreland basin again, and delta developed in the middle part, showing the tectonic movement of Longmenshan Orogen reactive, the north and the south hard again, the middle relative quiet During the stage of TS2BW, the tectonic sequence filling characteristics of western Sichuan foreland basin reflected the tectonic movement of the north part and the south part peaceful, but the south part might be serious. Like the stage of TSlBE, TS2BE, during the stage of TS3BE, alluvial fan was the main setting of the north part and the south part of western Sichuan foreland bsin, delta-lake was the main setting of the middle part, showing the tectonic movement of the north part and the south part of Longmenshan Orogen severe, the middle part was quiet During the stage of TS3BW, the tectonic movement of the north part and the middle part of Longmenshan was kind, the south part, alluvial fan sediments found in the Lushan-Lianghekou district.


Zhao J.X.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Zhao J.X.,Institute of Sedimentary Geology | Shen Z.J.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Shen Z.J.,Institute of Sedimentary Geology | And 7 more authors.
Acta Petrologica Sinica | Year: 2011

The development of sequence stratigraphy in recent years provides new approach for us to perform basin analysis. We divided the Yanchang Formation of Late Triassic in Ordos basin into 4 long-term and 22 medium-term base level cycles using sedimentology and high-resolution sequence stratigraphy methods. In Yanchang Stage, the deposit-sequence-structure evolution of Ordos basin can be summarized as the following; the structure subsided initially in LSCl and lakes were formed; the lake basins downwarped quickly in LSC2 and was most active in the late period; in LSC3 the circumjacent structures tended to be stable, with basin filling commenced and the lakes became shallow; in LSC4 fluvial deposition increased, and the basin turned into extracompensation stage, with the lakes silted and turned into residual lacustrine deposit This paper also put forward and defined the concept of sequence structure dynamics, which is considered as a subject that researches on the control and effect of tectonic movement, sea level fluctuation, source supply, climate and sedimentation on sequence structure development and its distribution laws during sequence filling process. Based on the comprehensive division of the Yanchang Formation sequence stratrigraphy, the sequence structure was classified into 5 types (A, Bl, B2, B3 and C) according to the sequence structure variation features formed in a datum variation cycle. Then we detailedly analyzed the sequence filling structure features, structure types, sequence filling dynamics process, developing types of sequence structure and filling process with respect of various locations and deposit system units of the Yanchang Formation, Ordos basin, and discussed the sequence structure dynamics characteristics of large continental depressed lake basins. Then we brought forward the "sequence structure distribution laws" for the first time, and constructed the sequence structure distribution pattern of large continental depressed lake basins of Yangchang formation, Ordos basin. It was considered that without important structural event or paroxysmal deposit event, only the type of adjacent sequence structures may distributed with superimposition.


Meng W.B.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Meng W.B.,Institute of Sedimentary Geology | Lu Z.X.,Sinopec | Liu J.D.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | And 2 more authors.
Acta Petrologica Sinica | Year: 2011

The Middle Jurassic in western Sichuan is typically a red clastic bed without hydrocarbon generation capacity. Composed by four sandstones of Js 2 1 , Js2 2, Js2 3 and Js2 4 from top to bottom, the reservoir of the Upper Shaximiao Formation in Xingchang gas field is tight sandstone reservoir with average porosity of 9. 6% and average permeability of 0. 177 ×10 μm . The source rock of the gas pool is 1000 ∼ 3000m underlain Xujiahe Formation, which makes the Upper Shaximiao Formation a distal gas pool. Secondary porosity that was created dominantly by the dissolution of feldspar grains was markedly developed in the reservoir sandstone and has gready enhanced the tight sandstone reservoir property. Secondary porosity made much higher contribution to reservoir than primary porosity. It accounts for proximately 60% of thin-section point counted porosity. Several lines of evidence from bitumen occurrence and dissolved minerals of the sandstone, the distribution of kaolinite, the composition of formation water, and component of hydrocarbon inclusions in authigenic minerals suggest that the second porosity of the Upper Shaximiao Formation tight sandstone was created by the dissolution of organic acid from three sources. The first source of organic acid is from the underlain Xujiahe Formation consists of very thick organic-rich coal beds with III-type kerogen that expelled organic acid during hydrocarbon generation which was transported upwards through faults and fractures. The second source is a result of reaction of oxidant in the reservoir sandstone with hydrocarbon transported from deep beds, and the less important third source comes from dehydration process of the mudrock of the Shaximiao Formation. The first two sources of organic acid are responsible for most of the secondary porosity formation, while those created by organic acid from the third source are trivial due to their very small amount and failure in preservation. Regional water potential difference in the fifth member of the Xujiahe Formation during Jurassic and faults and fractures provide the conditions needed for organic acid transportation from the underlain Xujiahe Formation up into the Shaximiao Formation. The content of soluble components of the sandstone, paleotectonic location of the reservoir, and the degree of fault and fracture development and their distribution are major controlling factors for the forming and distribution of dissolved porosities.


Su Z.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Su Z.,Institute of Sedimentary Geology | Chen H.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Chen H.,Institute of Sedimentary Geology | And 6 more authors.
Acta Petrologica Sinica | Year: 2011

The types and genetic mechanism of the Majiagou dolomite in Ordos basin are investigated using petrological analysis and geochemical methods. The results show that dolostones in Majigou Formation mainly consist of dolomicrite and crystalline dolostone. Dolomicrite often associates with gypsum or halite, with medium jacinth light in cathoduluinescence observation, lower degree of order, and high content of Sr and Na It provides similar δ 13C and REE distribution pattern with micrite. The value of Sr isotope is close to that of sea water in the same period, and fluid-inclusion homogenization tempetrature approximate to earths surface. These suggest that dolomitization fluid is high salinity fluid that closely related with sea water, considered as penecontemporaneous dolomitization which can be explained by evaporation pump mode. Crystalline dolostone contains little associated minerals, only pyrite observed occasionally. This crystal structure is usually xenomorphic curve. Crystalline dolostone shows medium-weak jacinth light in cathoduluinescence, whith high degree of order and low content of Sr, while Na and Mn content is close to that of dolomicrite. REE distribution pattern is similar with dolomicrite and close to micrite. The distribution of δ 13C is also corresponding to micrite, and fluidinclusion homogenization tempetrature is hight. These indicate that dolomitization fluid of crystalline dolostone is similar with that of dolomicrite. Crystalline dolostone is buried dolomitisation, where continuous compaction from overlying deposits urges the sealed brine to flow laterally, thus supplies unfailing Me 2+ for dolomitisation.


Lin L.B.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Lin L.B.,Institute of Sedimentary Geology | Chen Y.Q.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Chen Y.Q.,Institute of Sedimentary Geology | And 6 more authors.
Acta Petrologica Sinica | Year: 2011

Arguments on whether An tian tectonic movement existed or not and on how widely its influence might range during Norian Period and Rhaetian Period of Late Triassic ( between the 3rd and 4th member of Xujiahe Formation) in Sichuan basin have existed for long time. This study, for the first time, found the sedimentary bauxite layer on the top of the 3rd member of Xujiahe Formation (between the 3rd and 4th member of Xujiahe Formation) in the northeast of Sichuan basin. On the basis of thin section, geochemical characteristics, electronic probe, SEM and X-ray etc. , the bauxite mainly occurred as pisolitic with both pisolitic structure and block structure. The main components of interstitial matter among pisolites are tremelloses and vermicular kaolinites. Also, clean bright radial and sphaerolitic siderite is probed in small quantities with limonite dissemination and occasional sphalerite. The main pisolitic bauxite has 3 shapes, microgranular, flaky and floccus-like, Among these, crystalline and flaky bauxites are colorless, median processus, obvious cleavage under plane-polarized light. Under cross-polarized light, they bear second-order blue interference color. Combined with X-ray analysis, we define them diasporite (α-AlO(OH)) and the Al2O3 content of them is 85.022% ∼ 87. 763%. The logging curve shows that natural gamma increases abnormally and when the density curve is on the verge of 3g • cm-3, the neutron porosity is relatively high. The findings support the argument that there was a long sedimentary intermission between the 3rd and 4th member of Xujiahe Formation and give evidence for the existence of the Anidan tectonic movement. Moreover, the study also points out that the influenced area by the An tian tectonic movement is far beyond the Longmenshan front area, it turns into the interior of the basin, even affects the whole Sichuan basin.


Zhong Y.J.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Zhong Y.J.,Institute of Sedimentary Geology | Chen H.D.,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation | Chen H.D.,Institute of Sedimentary Geology | And 9 more authors.
Acta Petrologica Sinica | Year: 2011

The hydrocarbon breakthrough in the 4 th member of the Leikoupo Formation shows important geological significance for petroleum exploration. Through comprehensive analysis of drilling cores, thin section, well logging data, fluid inclusion, carbon, oxygen and strontium isotope, three types of paleokarstification, including syndepositional, epigenic, and buried ones, are identified in the residual deposits under the unconformity surface at the top of Leikoupo Formation. They are considered as the key factors that control the reservoir formation of the 4 th member of the Liekoupo Formation. The distribution of the reservoirs formed in the early stage is controlled by syndepositional paleokarstification. These reservoirs are limited in lateral by distribution of high-energy beach facies. Epigenesis paleokarstification is a critical geologic event that leads to the formation of the reservoir. The related reservoirs are vertically limited within 90m below the unconformity surface. Based on vertical and lateral distribution patterns of weathering karstification, it is suggested that karst-related reservoirs are commonly occurred vertically in debris-support breccia limestones and dolostones that distributed within surface karst area, or along half-filling high-angle dissolved seams and in small to medium-sized solutional pores in the vertical direction, and half-filling small to medium-sized solutional pores, dissolved seam, broken crack in the cave top and river breccia. Laterally, these reservoirs generally developed at karst slope, and karst hammock are found as the most advantageous geomorphic units for the formation of reservoirs. Burial karstification is related with dissolution of barbonte minerals resulted from hydrothermal fluids and organic acid, and it is considered as the key factor for reservoir optimization.


Yang X.-Y.,Institute of Sedimentary Geology | Yang X.-Y.,Southwest Petroleum University | Bao H.-P.,Petrochina | Ren J.-F.,Petrochina | Ma Z.-R.,Petrochina
Natural Gas Geoscience | Year: 2015

The types of dolomites from the Ma 55 sub-member of Ordovician Majiagou Formation in Ordos Basin are micrite, siltcrystal-micrite and siltcrystal dolostones based on petrological analysis and geochemical methods. The results show that micrite dolostone is formed in ungated-restricted environment with high salinity by penecontemporaneous dolomitization, with micrite texture, garnet light in cathoduluinescence observation, lower degree of order. The average value of δ13C, δ18O and 87Sr/86Sr are -1.23‰, -7.59‰ and 0.70981, respectively. Siltcrystal-micrite dolostone is formed by many dolomitization for penecontemporaneous dolomitization of the micritic dolomite and reflux seepage dolomitization of the siltrystal dolomite in which are many lime-mud or dolomite-mud, whit siltcrystal-fine micrite texture, dirtier, no or extreme dark light in cathoduluinescence, 0.75 of degree of order. The average value of δ13C, δ18O and 87Sr/86Sr are -0.43‰, -7.29‰ and 0.70936, respectively. Siltcrystal dolostone shows the same as siltcrystal-micrite dolostone in cathoduluinescence, but the degree of order is 0.81. The average value of δ13C, δ18O and 87Sr/86Sr are -0.65‰,-6.46‰ and 0.70967, respectively. These indicate that siltcrystal dolostone is due to buried dolomitization with varying degrees of superimposed dolomitization. ©, 2015, Science Press. All right reserved.

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