10 August 2018, Volume 29 Issue 8
    

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    Natural Gas Geoscience. 2018, 29(8): 1-2.
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  • Feixianguan Formation lithofacies zoning and its geological significance of eastern side of Kaijiang-Liangping Trough，NE Sichuan Basin
    Jiang Yu-qiang, Gu Yi-fan, Xu Chang-hai, Zhang Jie-wei, Cheng Xiao-yan, Chen Hui
    Natural Gas Geoscience. 2018, 29(8): 1067-1077. https://doi.org/10.11764/j.issn.1672-1926.2018.06.008
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    The evolution of sedimentary facies has always been an important factor restricting the development and distribution of Permian-Triassic reef-shoal reservoirs around Kaijiang-Liangping Trough.Based on drilling and core data，it is demonstrated that the Lower Triassic Feixianguan Formation in the eastern side of the Trough is divided into two parts by Luojiazhai-Zhengba-Zhaojiawan.Lithofacies zoning is obvious in both northern and southern parts.The seismic amplitude attribute indicates that the line is a high and low transition zone of sedimentary geomorphology which is characterized by the high energy deposition combination of residual oolitic dolomite and bright crystal oolitic limestone.The north of the line is an evaporation lithofacies combination consisting of gypsum,gypsum-bearing dolomicrite and gypsum-bearing residual oolitic dolomite.The south is a low energy lithofacies combination consisting of micrite and muddy limestone.The middle-late stage of Changxing Formation is a LST deposition under sedimentary background of the gentle slope and open platform with rims and the early stage of Feixianguan 1st is TST on the basis of sedimentary paleogeomorphology of the Changxing Formation.Meanwhile the oolitic shoals which consist of gypsum-bearing residual oolitic dolomite concentrate in carbonate terrace such as Yuexi 1-Jinzhu 1-Gaozhang 1 well area.The late stage of Feixianguan 1st to Feixianguan 2nd  is the key stage of oolitic shoal reservoir development which is HST deposition of the gentle slope and restricted platform with rims.Under the jointly control of NW-trending basement fracture and NE-trending geomorphic highland，thick oolitic shoals of “U” shape develop along the platform margin.The north of the platform margin is the evaporation lagoon environment and the south is upper glacis sedimentary environment along Tiancheng 1-Mennan 1-Xinxing 1,and the southward transition to the lower glacis sedimentary environment.
  • Discovery of bioturbated thrombolites in the Lower Ordovician of Songzi area，Hubei Province
    Xiao Chuan-tao, Xiao Yun-peng, Song Zhen-yu, Huang Yun-fei, Dong Man
    Natural Gas Geoscience. 2018, 29(8): 1078-1084. https://doi.org/10.11764/j.issn.1672-1926.2018.06.001
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    It is the first time that bioturbated thrombolites was discovered from the Lower Ordovician in Songzi area of Hubei Province.This discovery not only fills gaps in the research field of the studying area，providing new material for the study of the genesis of thrombolites，but also has important theoretic meaning for exploring the relationship between the evolution of coagulation stone and the radiation of metazoan.According to the appearance and structure of the thrombolites，porphyritic，reticular and striped clotted limestone was recognized in this paper.Based on the detailed description of the sedimentary characteristics of each type of thrombolite，the sedimentary environment is analyzed.It is thought that the maculosus，striped clotted limestone may be formed in the restricted intertidal zone with certain energy，and the reticulated coagulation stone may be formed in the low energy environment of subtidal zone.Based on a number of drilling predation fossils of mollusks Ecculiomphalus found in leopard porphyritic，reticulated thrombolites and traces of bioturbation formed by the drilling animals，the authors suggest that both leopard porphyritic and reticulated coagulation stone are bioturbated thrombolites.The authors believe that the Ordovician thrombolites are decreasing with time，and there is a certain relationship between the decline of thrombolites and the increase of metazoan.The authors also believe that drilled predators not only chew up the bacteria and algae microbes forming thrombolites and stromatolites，resulting in the continuous reduction in the number of stromatolites，but also destroyed the growth state of the stromatolites，resulting in the formation of the unique characteristics of the bioturbation type of thrombolites.
  • Analysis on the controlling factors of tight gas “sweet spot” of Shan2 sub-member in Wushenzhao area，Ordos Basin
    Zhu Li-wen, Wang Zhen-liang, Zhang Hong-hui
    Natural Gas Geoscience. 2018, 29(8): 1085-1093. https://doi.org/10.11764/j.issn.1672-1926.2018.06.019
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    It is found that there is a typical low-amplitude structural trap and it has obvious controlling effect on the distribution of gas and water in Shan2 sub-member during the process of exploration and development in Wushenzhao area in the eastern Sulige Gasfield.In order to further clarify the controlling factors of gas accumulation of Shan2 sub-member in this area，the characteristics of reservoir，trap types and accumulation rule of gas reservoir are discussed on the basis of the analysis of the experimental data，such as thin section，physical property，mercury injection，SEM and NMR.The results showed that the lithology of Shan2 sub-member in the study area is mainly quartz sandstone，the porosity is mainly 5%-10% and the permeability is mainly (0.1-10)×103μm2，which belongs to extra-low porosity and extra-low permeability and even ultra-low permeability reservoirs.The connectivity of pore throats is fairly good and the seepage ability is relatively good，too.The type of gas reservoir trap is a structural-lithologic trap with a shape of quasi-domed.The distribution of gas reservoirs in the trap is continuous，and the high part of the trap is filled with gas and the low part is water.The geological structure does have obvious controlling effect on the accumulation of natural gas in the Shan2 sub-member.The accumulation and preservation of natural gas are controlled by both low-amplitude structures and sand bodies.
  • Characteristic of provenance and its impact on reservoir quality of Upper Shihezi Formation,L block,Ordos Basin
    Liu Qin-qin, Chen Gui-hua, Chen Xiao-zhi, Zhu Yan-he, Yang Xiao-feng
    Natural Gas Geoscience. 2018, 29(8): 1094-1101. https://doi.org/10.11764/j.issn.1672-1926.2018.05.007
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    Based on the data of lithic fragment,heavy mineral，rare earth element,the provenance of clastic particles of Upper Shihezi Formation is analyzed in the study area．The research showed that the clastic particles mainly came from the Yinshan mountain ranges which mostly consisted of metamorphic rock of Precambrian．It was also controlled by the granodiorite，intrusive body of Archaeozoic and Proterozoic,which was from Inner Mongolia orogenic belt．Under the joint influence of the two parent rock origins，clastic particles in Upper Shihezi Formation had the characteristic with high debris composition and more feldspar.The dissolution under the provenance control was the main mechanism to control the reservoir quality，which was influenced by the distribution of soluble minerals such as feldspar，rock debris，volcanic tuff and so on.On the other hand， different kinds of sedimentary facies signs were analyzed，identifying the major microfacies type and its distribution characteristic of Upper Shihezi Formation in the study area．It was determined that it mainly developed delta front deposits,and the underwater distributary channel was the skeleton sand body．On the whole，the reservoir properties of Upper Shihezi Formation are influenced by the provenance and sedimentary facies controlled by it，and its reservoir performance has comparative advantage in Upper Paleozoic strata.
  • Caprocks characteristics and their control on hydrocarbon accumulation of bedrock gas reservoirs in eastern segment of Alkin Piedmont，Qaidam Basin
    Li Hong-zhe, Ma Feng, Xie Mei, Yang Wei, Zhang Cheng-juan, Wang Pu, Zhao Jian
    Natural Gas Geoscience. 2018, 29(8): 1102-1110. https://doi.org/10.11764/j.issn.1672-1926.2018.05.014
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    Based on the analysis of core facies，logging facies and seismic facies of Paleogenlulehee in the eastern part of Alkin Piedmont，it is found that regional gypsum-salt cap rocks developed in the Early Paleogene.The lithology was mainly gypsum mudstone and creaming mudstone，and with little gyprock.The gypsum-salt rocks mainly developed in the bottom of Lulehe Formation in vertical，and formed 4 areas with largest thickness in horizon，including northern Jiandingshan，western Dongping，Dongping and Niuzhong，and thinned gradually from west to east.In the study area，the formation and distribution of gypsum-salt rocks was jointly controlled by palaeogeomorphology，paleoclimate and sediment supply before the Paleogene deposits.A well match between development degree of gypsum-salt rocks and hydrocarbon distribution was proved:Gypsum-salt rocks with lager thickness formed structural，lithologic and stratigraphic reservoirs in underlying bed rocks，with well hydrocarbon preserving and accumulative conditions；and those with less gypsum-salt rocks formed regional cap rocks and structural reservoirs with multiple layers.Above all，the gypsum-salt cap rocks developed in Lulehe Formation in the eastern part of Alkin Piedmont controlled natural gas enrichment effectually，pointing out a direction for predicting favorable areas of coal-type gas in Qaidam Basin.
  • Studies on the reservoir characteristics and the fluid flow in Jianquanzi member of the Jiuxi Basin，northwest China
    Zhang Shi-ming, Wang Jian-gong, Zhang Xiao-jun, Zhang Ting-jing, Cao Zhi-qiang, Yang Lin-ke
    Natural Gas Geoscience. 2018, 29(8): 1111-1119. https://doi.org/10.11764/j.issn.1672-1926.2018.06.017
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    Based on the thin sections observation，capillary pressure testing，relative permeability measuring and other experimental methods，distributed rules and flow characteristics of fluid in reservoirs of Jianqauanzi member，Jiuxi Basin，were studied.The results show that according to features of pore structure the pores can be divided into three kinds.I class has relatively good reservoir property，the capillary curves have significant platforms，and positive skewness.The samples with high oil saturation have the characteristics of thicker maximal radius and median radius，more positive skewness，lower entry pressure.Oil-water relative permeability of high permeability samples changes fast，the oil displacement efficiency of high permeability samples is high.Compared with oil-water relative permeability curves，the oil-nitrogen relative permeability curves have lower residual oil saturation and wider common permeable region.The wet ability，pore structure and contents of clay minerals are three key factors affecting fluid flow in reservoirs.The samples with high proportion of crude pore，low contents of clay minerals have good percolation condition，which conforms to Dercy’s law.The reservoirs have the typical features of water-wet reservoirs.Nitrogen displacement efficiency was more efficient than water displacement efficiency，especially for the low permeability samples.
  • Development model of sedimentary system and reservoir under valley-monadnock paleotopography during buried stage of paleouplift:Case study of 1st member of K1q  in Shinan area,hinterland of Junggar Basin
    Gao Chong-long, Ji You-liang, Jin Jun, Wang Jian, Ren Ying, Zeng Li, Wang Dao-wei, Zhang Hao, Li Jin-jie
    Natural Gas Geoscience. 2018, 29(8): 1120-1137. https://doi.org/10.11764/j.issn.1672-1926.2018.06.014
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    Lower Cretaceous Qingshuihe Formation (K1q) within hinterland area of Junggar Basin is a distinctive sedimentary sequence developed during the buried stage of large-scale Chemo paleouplift.In addition to Jurassic and Triassic,K1q  becomes another favorable target for hydrocarbon exploration within the basin.However,the geomorphic evolution during the buried stage of paleouplift is not fully taken into account in previous researches about sedimentary system and reservoir types of K1q,leading to the restriction of effective hydrocarbon exploration and development.Thus,using core,logging,3-D seismic data,field outcrop and assay data,this research rebuilds palaeogeomorphology of the study area based on the sequence stratigraphic classification and illustrates the sedimentary facies and distribution of depositional systems.Meanwhile,in combination with previous research results,the evolutionary model of paleogeomorphy and sedimentary system during the buried stage of paleouplift is established and its control on reservoir types is analyzed.The results show that:K1q is a whole third order sedimentary sequence,and 1st member of K1q  can be classified into LST and TST,while 2nd member of K1q is HST.Controlled by the distinctive valley-monadnockpalaeogeomorphology,LST gravelly braided rivers were confined within the valleys,moreover,slump debris flow deposits could occur around the edges of monadnocks.During the early period of TST,sedimentary system changed into shallow-water braided delta front in study area,however,shallow to semi-deep lacustrine covered the whole area in late period.Regionally,the paleouplift existed as an intrabasinal source area during the Late Jurassic due to the continuous and differential dynamics of weathering and river incision,and gradually turned into different scales of valleys and monadnocks.Whereas the intrabasinal source system of paleouplift disappeared since Early Cretaceous.During the deposition period of K1q,the paleouplift zone gradually buried and the peneplanation processes of palaeogeomorphology along with subsidence eventually turned the hinterland area into depocenter of the basin.Controlled by the valley-monadnockpalaeogeomorphology,reservoir types within the paleouplift area can be classified into monadnock reservoirs of Jurassic and stratigraphic overlap and structural reservoirs of K1q.
  • Paleoenvironment of organic-rich shale from the Lucaogou Fromation in the Fukang Sag,Junggar Basin,China
    Shi Jun, Zou Yan-rong, Yu Jiang, Liu Jia-jing
    Natural Gas Geoscience. 2018, 29(8): 1138-1150. https://doi.org/10.11764/j.issn.1672-1926.2018.06.016
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    The Junggar Basin is a large oil-gas-bearingbasin in China,the Fukang Sag is located in the edge of the southeast of the Junggar Basin and on the north of the Bogda Mountain,which is the secondary sag in the east of the basin.We choose the Lucaogou Formation as the object that is near the Sigonghe River in the Fukang Sag to reveal the level of enrichment of the organic matter and sedimentary environment characteristics in study area.The content of organic matter in vertical profile ranged from 3.67% to 16.0% with an average of 8.5%,showing that the shale is rich in organic matter.Trace element plays a key role in unlocking paleoenvironments because of its stability.We explore the paleoenvironment through investigating paleosality,aleoclimate,paleoredox,paleoproductivity,paleo-water-depth,and paleoproductivity.Results suggest that the shale was deposited in the anoxic-suboxic,semi-arid and warm-humid,weak hydrodynamic,and fresh and semi-saline continental deep lake.High TOC in the shale is mainly caused by the primary productivity,and the paleoenvironment has a positive influence on the accumulation of organic carbon.
  • Analysis on favorable geologic conditions for water-soluble gas formation and degassing in central Sichuan Basin
    Qin Sheng-fei, Li Jin-shan, Li Wei, Zhou Guo-xiao, Li Yong-xin
    Natural Gas Geoscience. 2018, 29(8): 1151-1162. https://doi.org/10.11764/j.issn.1672-1926.2018.06.005
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    In this paper，though according to the fact that the gas generation intensity of the Xujiahe coal measure source rocks in the middle of Sichuan Basin is relatively low，still a series of large gas fields (reservoirs) have been proved.Aiming at the problems existing in the study of reservoir formation，the geochemical analysis is used on the natural gas and formation water for a detailed study.Based on the geological background，the geological conditions for the formation of water-soluble gas in the Xujiahe Formation in central Sichuan Basin were analyzed in detail.The study shows that the Xujiahe Formation water in the middle Sichuan Basin is much developed，and the multi-layered coal-bed source rocks and multiple sets of sandstones are superimposed on each other.The Xujiahe Formation has good conditions for the forming of water-soluble gas.The formation water in Xujiahe Formation is CaCl2 type，with high salinity.The H and O isotope value are far away from the atmospheric precipitation line，indicating that the formation water has been well preserved.The dissolved natural gas in water can be well preserved together with the formation water.The tectonic movement of the Himalayan period has caused a significant uplift in the central Sichuan area，and the big erosion of the overlying strata.The decompression of the formation water caused the gas releasing from water.The released gas can either add additional natural gas to the existing gas reservoir，or form a free gas pool itself at higher site in the reservoir.After calculation，one cubic meter of formation water can probably release 2.4m3 of methane during Xujiahe Formation uplift.
  • Comparative study on porosity and permeability in net confining stress of three natural gases in coal series reservoirs in Guxian County，Qinshui Basin
    Cheng Ming, Fu Xue-hai, Zhang Miao, Cheng Wei-ping, Qu Li-zhen
    Natural Gas Geoscience. 2018, 29(8): 1163-1171. https://doi.org/10.11764/j.issn.1672-1926.2018.05.013
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    In order to reveal the characteristics of the difference in porosity and permeability of coal，shales and tight sandstones in coal series，2 coal samples，2 shale samples，and 4 sandstone samples were collected from the Guxian County，Qinshui Basin，Shanxi Province，and a comparative study of the net confining stress permeability was conducted.The results show that the porosity and permeability of three natural gases in coal series reservoirs increase exponentially with the increase of effective stress，and the ratio of porosity compressibility of coal reservoirs，shale reservoirs and sandstone reservoirs is 1∶1∶0.58，the permeability attenuation coefficient ratio is 1∶0.73∶0.78.The porosity and permeability stress damage rate of three natural gas reservoir increase with the increase of effective stress in the form of two-stage，and the effective stress is <4MPa.The porosity and permeability damage rate of three natural gases reservoir both follow the effective stress.The increase shows a rapid upward trend with an effective stress of >4MPa.With the increase of effective stress，the growing rate is gradually stable，and the stress sensitivity of coal reservoirs，shale reservoirs，and sandstone reservoirs decreases sequentially.The research results have theoretical and practical significance for the co-examination of the three natural gases in coal series.
  • Prediction of thin sandstone reservoirs of Wutonggou Formation in the DX178 well area of Xinjiang by using liquid mobility factor method
    Guo Xiao-long, Li Xuan, Li Bo, Yang Ya-di, Jiang Shu-li, Xu Jing
    Natural Gas Geoscience. 2018, 29(8): 1172-1180. https://doi.org/10.11764/j.issn.1672-1926.2018.07.001
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    The Wutonggou Formation in the DX178 well area develops two sets of upper and lower gas layers with natural gas geological reserves of 31.49×108m，which is a favorable area for the next step to development and production.However，the reservoir in the Wutonggou Formation is thin，and the frequency of existing seismic data is relatively low.The investment cost for exploration and development is high and the risk is large.Therefore，it is necessary to improve the sand drilling rate of horizontal well and study on the identification method of thin sand.The sandstone reservoirs with large thickness can be merely identified by conventional post-stack seismic inversion method.Owing to the limitation of seismic resolution for the thin sand，the prediction results cannot meet the needs of exploration and development.In this paper，the liquid mobility factor calculated by the high-precision seismic time-frequency analysis method can effectively characterize the sandstone reservoir and non-reservoir layers.According to the logging data，the fluid activity factor of the sandstone reservoir was calibrated by the liquid mobility factor，and the distribution area of sandstone can also be predicted.This method was used to predict the thin sandstone reservoirs of the Wutonggou Formation in DX178 wells area.The prediction results are in good agreement with the actual drilling results.During the implementation process of the four horizontal well drilling，the well trajectory was timely adjusted according to the prediction results，which effectively improved the sand drilling rate of horizontal well，and achieved good development results.
  • Study on the relationship of tortuosity with pore structure in micro-porous media
    Li Tao, Li Min, Zhang Lie-hui, Tian Shan-chuan, Zhao Xiao-yu, Zheng Ling-li
    Natural Gas Geoscience. 2018, 29(8): 1181-1189. https://doi.org/10.11764/j.issn.1672-1926.2018.06.013
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    Two-dimensional anisotropy, heterogeneity and different pore shape of micro-porous media were generated by adopting the quartet structure generation set (QSGS) method, randomly distributed particles method and random fracture generation method, while the improved QSGS method was utilized to generate two-dimensional fracture-pore dual media. By applying bounce-back wall boundary condition, a multi-relaxation-time lattice Boltzmann (MRT-LB) model was adopted to simulate fluid flow in porous media for analyzing the correlation of tortuosity with pore structure in micro-porous media. The simulation results show that porosity, anisotropy, heterogeneity, pore shape and fracture all affect tortuosity, while porosity, anisotropy, pore shapeand fracture play a more significant role. The tortuosity of the circular pore media is generally greater than that of the fractured porous media, while the tortuosity of the intergranular pore media is basically in the middle. The aperture and strike of fracture significantly affect the tortuosity of fracture-pore dual media. Meanwhile, the existing tortuosity models are not suitable for complex porous media. Finally, the relations of tortuosity with anisotropy and porosity are established respectively based on the simulation results.This workis helpful to further reveal the relationshipbetweentortuosity and pore structurein micro-porous media.
  • Research on rate decline analysis for horizontal well in triple-porosity composite reservoir
    Huang Yu，Li Xiao-ping，Tan Xiao-hua
    Natural Gas Geoscience. 2018, 29(8): 1190-1197. https://doi.org/10.11764/j.issn.1672-1926.2018.06.010
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    With the increase of energy demand，the exploration and development of carbonate reservoirs have attracted more attention from various countries.Carbonate reservoir is often regarded as the triple-porosity reservoirs (matrix pores，fractures and caves) in well test model.However，the current research on rate decline analysis of this type of reservoir is relatively few.Secondly，there is a difference in the properties of near wellbore area and the area far from the wellbore because of the formation acidizing，fracturing or the characteristics of the reservoir itself.This kind of reservoir is called composite gas reservoir.Therefore，an unsteady flow model for horizontal well with consideration of triple-porosity medium in composite gas reservoir is established.Using complex mathematical methods for instance:Laplace transformation，orthogonal transformation，the analytic solution of the proposed model is obtained.We also analyzed the effects of relevant parameters on rate decline type curve of horizontal wells in triple-porosity composite gas reservoir.This work enriched the relevant theories of this area，and it has important guidance for better understanding the percolation flow and the production performance of this typical reservoir.

  • Analysis of main controlling geological factors of production based on “three qualities” of CBM reservoir
    Guo Guang-shan, Xing Li-ren, Liao Xia, Jiang Rui
    Natural Gas Geoscience. 2018, 29(8): 1198-1204. https://doi.org/10.11764/j.issn.1672-1926.2018.06.004
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    The resources,reconstruction and recoverability of coal seams are the three key reservoir qualities (TKRQ) that affect the capacity of coalbed methane (CBM).By comparing the production data of 67 wells produced over three years in DJC area,the relationship between TKRQ and well productivity is analyzed in detail.Then,the main geological factors affecting TKRQ are analyzed as well.As the results showed,in this area:（1）The main controlling factor on CBM resources is gas content when the abundance of resources is greater than 1.2×108m/km2,the average daily gas production of CBM well is greater than 1 000m/d,and the thickness of No.3 coal seams is stable.（2）There are five fracturing curve types,where the decline-stable type and decline-wave type are better on gas production.The properties of fault,coal structure and crustal stress have combined influence on the reconstruction of coal seams.（3）The recoverability of CBM is due to the ratio of critical desorption pressure to reservoir pressure and permeability.The CBM well is easier to drainage and high production when the ratio is greater than 0.6 and the water production index per meter is greater than 0.8 m/(d·m·MPa).
     
  • Vertical fluid energy characteristics and orderly development suggestion in the southwestern region of Enhong Syncline in Yunnan
    Wu Cong-cong, Yang Zhao-biao, Sun Han-sen, Zhang Zheng-guang, Li Geng, Peng Hui
    Natural Gas Geoscience. 2018, 29(8): 1205-1214. https://doi.org/10.11764/j.issn.1672-1926.2018.05.003
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    Reservoir fluid energy is the main driving force for coalbed methane development，and it is the key factor to obtain high production.It is of great significance to identify the fluid energy characteristics of coal measures to optimize the favorable sections of coalbed methane.In this paper,take the southwestern of Enhong block as the research object，based on pumping test data and coalfield exploration data，the layer characteristics of vertical fluid energy in the study area were analyzed from three aspects of apparent reservoir pressure，hydrodynamic field and water chemical field.It is found that there are obvious differences in different layers.The coal-bearing strata generally belong to under-pressure state.The average pressure coefficient of middle section is 0.86，and the fluid energy is the highest.The hydrodynamic condition of upper section is obviously stronger than the middle and lower sections，and has strong hydraulic connection with the surrounding aquifers，which was conducive to the drainage and depressurization.The groundwater closeness index of the upper section is 11.96 on average，the type of water quality is mainly HCO-3-Ca2+ type，indicating weak closeness and relatively open water chemical environment.The gas content of each section is high and the difference was small，which does not constitute the restriction condition of constraint development.The 5 hydrogeological evaluation indexes，including apparent reservoir pressure coefficient，unit water inflow，permeability coefficient，influence radius and groundwater closeness index，are extracted，and the development potential of different coal bearing sections is preliminarily evaluated by using grey relational analysis method.It is considered that the upper section is the favorable development layer，and is recommended as the preferred layer.The progressive development order of each coal bearing section is:Upper section → middle section → lower section.
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