Lithologic Reservoirs

Taking the 8th sand group of the second member of Shahejie Formation in Shengtuo Oilfield as an example, this paper analyzed the configuration of braided river delta mouth bar by using physical simulation experiment and measurement result of modern sedimentation, and studied the ratio of length to width of mouth bar. The results of physical simulation experiment show that the length of mouth bar varies from 45 cm to 210 cm and the width of mouth bar ranges from 30 cm to 150 cm, the ratio of length to width of mouth bar shows some correlation, as the same with the result of modern sedimentation measurement. At last, the empirical formula of the ratio of length to width of single mouth bar was established with combination consideration of physical simulation of sedimentation and measurement result of modern sedimentation. This formula can guide the study of reservoir architecture of mouth bar and the boundary identification of single mouth bar, providing support for establishment of fine 3D model of mouth bar.

Carbonate facies and sedimentary evolution of Upper Devonian Tuqiaozi Formation in Ganxi section of Longmen Mountain

Li Fengjie， Qu Xuelin， Du Lingchun， Jing Xigui， Cheng Xiaoyu

2015, Vol.27(5): 6–12 Abstract ( 540 ) PDF (2758 KB) ( 397 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.002

Based on the data of cross sections, the Upper Devonian Tuqiaozi Formation in Ganxi section of the Longmen Mountain is considered to be carbonate ramp deposits. With the sea level of a brief fall in the middle sedimentary stage of Tuqiaozi Formation, the carbonate ramp transformed to carbonate platform, of which the most direct identification mark is the emergence of breccia and slump deposit in the front of reef. There are two types of subfacies including shallow ramp and deep water ramp in carbonate ramp and two types of subfacies including platform edge reef and beach and foreslope in carbonate platform. Two whole carbonate sedimentary cycles developed in Tuqiaozi Formation. There are different sedimentary features between the two sedimentary cycles with the changes of sea level rise and fall. The carbonate ramp of Tuqiaozi Formation in Ganxi section is characterized by rhythmite formed by micrite-marl.

Geological information extraction and analysis based on digital outcrop ：A case of Yangjiagou section of the Upper Triassic Yanchang Formation in Ordos Basin

Liu Xuefeng， Ma Yiyun， Zeng Qihong， Shao Yanlin， Zhang Youyan， Ye Yong

2015, Vol.27(5): 13–18 Abstract ( 945 ) PDF (1294 KB) ( 333 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.003

In order to improve the shortcomings of the traditional method of outcrop research and cognize geological information more objectively and comprehensively from outcrop, the laser radar technique was applied to the study of outcrop stratigraphic mapping. With the use of computer visualization, this paper constructed digital outcrop of Yangjiagou section of the Upper Triassic Yanchang Formation, Ordos Basin. Geological information extraction and analysis were carried out based on digital outcrop, such as the sequence stratigraphy, sedimentary cycle and sand body distribution of Chang 3 oil reservoir set of Yanchang Formation. Through establishing typical sequence boundary identification marks and combining with the theory of sequence stratigraphy, sequence boundary identifying and tracking on digital outcrop were conducted and a fourth-order sequence boundary was identified. A positive cycle and a reverse cycle were respectively developed above and below the boundary, and the location of the thickest sand body is corresponding to the fourth-order sequence boundary. Through establishing sedimentary cycle identification marks, tracing and contrasting sedimentary cycle interface on digital outcrop, three asymmetric short-term cycles were identified. These three short-term cycles can compose a fourth-order base level rising half cycle. It is a set of the overall upward trend of the fourth-order parasequence-set, with the trend of decreasing thickness upward of sand body. Through the establishment of sand body interpretation marks, typical channel sand body were respectively identified at the bottom of the fourth-order base level cycle and the top of the profile. And then, fine description and comparison of the internal layer of single sand body was made according to the outcrop anatomy. Comparison results show that the main lithology of the profile is fine sand and coarse silt, locally clipping dark mudstone or shale.

Formation mechanism and vertical distribution of velocity sensitivityeffect in reservoir: An example from Triassic sandstone reservoir in Jilake area, Tabei uplift

Han Denglin， Zhang Shuangyuan， Yuan Wenfang， Feng Zhichao，Ouyang Chuanxiang， Peng Shuqi

2015, Vol.27(5): 19–24 Abstract ( 900 ) PDF (1745 KB) ( 492 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.004

As a main production layer of Jilake area in Tabei uplift, the TII24 layer is subject to a considerable variety of velocity sensitivity. The higher values of the velocity sensitivity effect are concentrated in the upper part of the TⅡ24 layer（single sand layers of TⅡ24-1 and TⅡ24-2）, showing a marked vertical disparity. The formation mechanism of velocity sensitivity effect within the layer was thoroughly analyzed from macroscopic and microscopic perspective by means of observing thin section, analyzing the X-ray fluorescence spectra and measuring the capillary pressure curve. The result shows that high content of clay minerals and the remaining particles of dissolved volcanic grains constitute the main source of the transmittable particles within the layer. The pore throat structure parameters indicate pore throat connectivity is relatively poor. The two aspects mentioned above are the main controlling factors for the strong velocity sensitivity. Relatively high content of clay minerals and comparatively poor pore throat connectivity in the upper part of the TII24 layer are the key controlling factors for the vertical disparity of the velocity sensitivity damage.

Surface modeling method of digital outcrop of Yanchang Formation in Ordos Basin

Zeng Qihong， Ma Yiyun， Xie Xing， Zhang Youyan， Ye Yong， Liu Song

2015, Vol.27(5): 25–29 Abstract ( 509 ) PDF (1023 KB) ( 408 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.005

Combined with ground-based Lidar, high accuracy difference GPS and high precision digital image, this paper summarized field data acquisition scheme of digital outcrop, established the Lidar point cloud data splicing and coordinate conversion process, put forward triangular mesh modeling method based on optimal trend surface and optimization method of digital outcrop surface model. The surface modeling method of digital outcrop provides an effective basis for the outcrop fine quantitative study. Using this method, this paper established digital outcrop surface model of Tanjiahe outcrops of Yanchang Formation in Ordos Basin, and carried out outcrop sand body distribution and development analysis based on the digital outcrop model. Delta plain distributary channel sand body and delta front underwater distributary channel sand body were identified on the Tanjiahe digital outcrop model. The vertical overlap relationship of the former single channel sand body is isolated, and its width-thickness ratio is relatively small; the latter single channel sand body is multi period continuous stacking in the vertical direction, and its widththickness ratio is significantly larger. Analysis result of outcrop sandstone and mudstone distribution indicates that due to the development of sand bodies controlled by sedimentary environment, sand ratio of distributary channel and underwater distributary channel sand body development area was significantly larger. Sand ratio gradually increased from northeast to southwest, and it is basically consistent with the source direction of the study area.

Application of ΔlgR method in sequence stratigraphy analysis of deep-water sediments: A case study from Qingshankou Formation of Gu 57 well in Gulong Depression, Songliao Basin

Liu Cangyu, Xin Renchen

2015, Vol.27(5): 30–36 Abstract ( 885 ) PDF (1050 KB) ( 446 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.04.006

In order to discuss the method of identifying and classifying sequence boundary and system tract in deep-water sedimen-tary system, this paper calculated the values of TOCR of Qingshankou Formation with ΔlgR method on the basis of resistivity and sonic logging data of Gu 57 well in Songliao Basin. With the curve of TOCR, the variation characteristics of TOCR correlate well with the development of sequence stratigraphy units during the sea level change cycle. 4 third-order sequences and 9 fourth-order sequences were recognized in Qingshankou Formation of Gu 57 well, and they were further divided into transgression and highstand system tracts. The result shows that the values of TOCR gradually increase during the TST period and the maximum value is in the maximum flooding surface, and that they gradually decrease during the HST period and the minimal value is in the forth-order and third-order sequence boundaries.

Accumulation conditions and exploration potential of Exmouth Plateau in North Carnarvon Basin

Wang Bo， Zhang Yingbo， Yang Xianghua， Hu Xiaolin， Xu Xiaoming

2015, Vol.27(5): 37–44 Abstract ( 531 ) PDF (3587 KB) ( 394 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.007

In recent years, some breakthroughs has been made in the exploration of deep-water areas in Exmouth Plateau, North Carnarvon Basin. The dark mudstone and thin coal strata of the giant shallow water braided fluvial delta of Mungaroo Formation are the main high-quality hydrocarbon source rocks during the Middle and Upper Trassic（the mean TOC is 4.61% and Ro is from 0.46% to 1.89%）. The kerogen type is from Ⅱ2to Ⅲ, which has superior hydrocarbonoffering capability. The high-quality reservoir of Mungaroo Formation developed in the Emouth Plateau because of the overlying strata of Jurassic and Lower Cretaceous are thin and the compaction is not strong. The beach-bar of Oxfordian Jansz sandstone and the Barrow delta are also good reservoirs from Late Jurassic to Early Cretaceous. The Exmouth Plateau developed two types of play: self-generation and self-storage, below-generation and above-storage. The exploration potential of the self-generation and self-storage is the best with channel sand body of Mungaroo Formation as the reservoir and dark mudstone of Mungaroo Formation as the source rock or the seal. In terms of the hydrocarbon source rock, reservoir and hydrocarbon generation and storage pattern, combined with the distribution of oil and gas leakage system, the favorable prospect areas should be mainly located in the east and southwest of Exmouth Plateau.

Characteristics and genetic mechanism of “ sweet spots ” of Shahejie Formation in BZ-A-1 well field, Huanghekou Sag

Wang Wei，Zhang Yingbo，Yang Xianghua，Wang Qingbin，Zhu Hongtao

2015, Vol.27(5): 45–52 Abstract ( 504 ) PDF (5075 KB) ( 479 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.008

The tight reservoir of Shahejie Formation in BZ-A-1 well field in Huanghekou Sag is mainly due to carbonate cementation. However, there are relatively high quality reservoirs developed in low porosity and low permeability sandstones. The characteristics, genetic mechanism and controlling factors of the high quality reservoirs in the first and second members of Shahejie Formation were studied by the means of backscatter, energy spectrum,cathodeluminescence, X-ray diffraction and SEM. The results show that high quality reservoirs of the second member of Shahejie Formation are the sandstones with dolomite membrane. The membrane can effectively inhibit the pressure solution of the quartz and the growth of secondary quartz edge. The burial dolomitization and the dissolution by acid fluid in the late stage played an positive role in reservoir development. The evaporitic environment of semi-closed water in the early stage of the first member of Shahejie Formation led to the development of biodetritus beach in the high part. Together with the impacts of both the alkaline water and terrigenous fresh water, three kinds of high quality reservoirs deposited, including bioclastic dolostones, hunji rocks with bioclast and micrite dolomitic fine sandstones.Dolomization and dissolution are the main causes of pore development.

Sedimentary characteristics of Late Cretaceous and Paleogene in northern Junggar Basin

Deng Yuan,Chen Shi yue,Yang Jinglin,Wang Yue

2015, Vol.27(5): 53–59 Abstract ( 1085 ) PDF (1777 KB) ( 490 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.009

There are controversies about stratigraphic classification and distribution of Late Cretaceous and Paleogene in northern Junggar Basin. The researches on sedimentary characteristics and evolution are relatively weak. Through detailed measurement, observation and description about the outcrops in northern Junggar Basin, the sedimentology theory was used to study the stratigraphic characteristics, sedimentary facies types and sedimentary evolution. The results show that the strata of Late Cretaceous and Paleogene in northern Junggar Basin were divided into four formations, including Ailikehu Formation, Honglishan Formation, Wulunguhe Formation and Suosuoquan Formation.Four kinds of sedimentary facies were identified: alluvial fan facies, braided river facies, lake facies and aeolian facies.Climate was heat and drought during the depositional period of Ailikehu Formation and Honglishan Formation, and braided river, alluvial fan and lake facies were developed. The climate became warm and wet during the depositional period of Wulunguhe Formation and the lower part of Suosuoquan Formation, and braided river was generally distributed. The climate became drought and aeolian deposition was developed during the depositional period of the upper part of Suosuoquan Formation.

Lithofacies and reservoir characteristics of subaqueous fan: A case from Yan 227 blok in Yanjia Oilfield

Dong Yue， Hou Jiagen， Cao Gang， Liu Yuming， Wang Ziyuan， Li Jing

2015, Vol.27(5): 60–66 Abstract ( 519 ) PDF (1207 KB) ( 533 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.010

A full understanding of the internal architecture and quality of subaqueous fan reservoir is significant for remaining oil tapping and development plan adjustment. Taking Yan 227 block in Yanjia Oilfield as an example, this paper summarized 6 types of core lithofacies based on core observation, and analyzed their sedimentary characteristics and origins. Because of the discrepancy of scale and resolution between core data and well log data or seismic data, in consideration of the necessity and possibility of quantitative classification of lithofacies by using well log data, the 6 types of core lithofacies were classified into 4 patterns, including mudstone facies, pebbly sandstone facies, gravel sandstone facies and conglomerate facies, and the classification criterion for each pattern was determined. And then, based on lab analysis data, the reservoir quality of each pattern was summarized: gravel sandstone facies mainly has residual pore between grains, the physical properties and oil-bearing character are the best, which makes it the first rank reservoir; pebbly sandstone facies has pores between grains and intragranular dissolved pores, the properties and oil-bearing character are medium and it is the second rank reservoir; conglomerate facies mainly has residual pores between grains but the physical properties and oil-bearing character are relative poor, so it is the third rank reservoir; the physical properties of mudstone facies is the worst, and it is nearly oil-free, so it is non-reservoir in the study area. On this basis, seismic inversion of acoustic impedance was applied to analyze the lithofacies distribution. The result shows that in vertical range, the conglomerate facies is well developed at the bottom of E2s4, which is the deposit of or between the main channel in inner fan; the sandstone facies （including pebbly sandstone facies and gravel sandstone facies） is well developed in the middle of E2s4, which is the complex deposit of multi-stage braided channel in middle fan; the mudstone facies is well developed at the top, and in all the formation shows normal cycle. In horizontal range, the conglomerate facies is ribbon-like and orients northeast-southwest, and the sandstone facies is sheet-like.

Internal structure and development model of intra-platform reef and shoal of Changxing Formation in Huayingshan area, eastern Sichuan

Hu Zhonggui， Li Rong， Hu Mingyi， Xiang Xiaoling， Qin Peng， Sun Yuedong

2015, Vol.27(5): 67–72 Abstract ( 864 ) PDF (1966 KB) ( 359 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.011

Reef and shoal facies is favorable sedimentary facies about carbonate rock oil and gas exploration. Clarifying the distribution and evolution of intra-platform reef and shoal facies is important for oil and gas exploration in intraplatform. Through a fine realistic and detailed profile study of reef of Changxing Formation in Jianshuigou section, Tianchi of Huayingshan area, this paper studied the characteristics of reef and shoal, depicted the internal structure and the development model of reef and shoal, and pointed out the distribution of favorable reservoir inside the reef. Three stages of growth cycles identified in profile are made up of reef base and baffling reef or reef skeleton deposited by grain debris beach, respectively corresponding to three upward shallowing parasequence groups, and they constituted aggradation-progradation reef. The second stage of reef is the most developed. The dolomitization of reef and shoal complex is strong in the top of growth cycle phases, and it is favorable for the reservoir formation.

Sand injectites of Paleogene and its geological significance in Xihu Sag, East China Sea

Huang Lingyu， Zhang Changmin， Liu Jiangyan， Xiang Xiaoling， Xu Fa， Hou Guowei

2015, Vol.27(5): 74–80 Abstract ( 810 ) PDF (2097 KB) ( 392 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.012

Based on foreign literature and reports, sand injectites were recognized in the Xihu Sag of East China Sea through an analytical comparison of regional tectonic settings and cores. These sand injectites are characterized by abundant of mudstone debris, liquefied sandstone dyke, water escape structure（dish-and-pillar structure）, liquefied fold deformation structure, load cast and flame structure, as well as ball and pillow structure. The formation mechanism, core characteristics and geological significance of sand injectites were simply discussed from the aspect of sedimentology. The intrusion of sand can form intrusive traps and improve the porosity and permeability of reservoirs obviously at the same time, and then improve reservoir properties. So it is very important for lithologic reservoir exploration and development to correctly understand and further research the sand injectites.

Sedimentary model of braided river delta of the Jurassic in Heshituoluogai Basin

Wang Yue， Chen Shiyue， Liang Huiyuan， Deng Yuan

2015, Vol.27(5): 81–86 Abstract ( 972 ) PDF (1966 KB) ( 489 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.013

The braided river delta sand body is favorable oil and gas reservoir sand body, and the study of its sedimentary characteristics and sedimentary sequence has important guiding significance for the oil and gas exploration. Based on the field measurement of the braided river delta outcrop of Jurassic Sangonghe Formation in Heshituoluogai Basin, by analyzing the sedimentary characteristics of various microfacies and the types of lithofacies, this paper established sedimentary sequence and sedimentary model of the braided river delta. The results show that progradational braided river delta developed, prodelta, delta front and delta plain of the braided river delta successively developed upwards, which can be subdivided into distal bar, mouth bar, underwater distributary channel, distributary channel and swamp microfacies. Eight types of lithofacies can be identified in the braided river delta, including graded bedding conglomerate facies, lag conglomerate facies, less obvious parallel bedding conglomerate facies, parallel bedding sandstone facies, massive sandstone facies, horizontal bedding siltstone facies, horizontal bedding mudstone facies and horizontal bedding carbonaceous mudstone facies. During the sedimentary period of Sangonghe Formation, the sediment accumulation rate is greater than the basin subsidence rate, and braided river delta fan advanced towards the basin direction and superimposed on the distal side, showing coarsening upwards sedimentary characteristics.

Application of multiple-point geostatistics method to structure modeling of alluvial fan

Wu Xiaojun， Li Xiaomei， Xie Dan， Sun Guoqiang

2015, Vol.27(5): 87–92 Abstract ( 434 ) PDF (911 KB) ( 478 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.014

Through scaning training image, multiple-point geostatistics can obtain the correlation of multiple points and can well describe reservoir distribution form and regularity. It has better practicability than traditional two-point geostatistics that describe the correlation of two points with variogram. The paper introduced the algorithm theory of multiple-point geostatistics and applied this method in structure modeling of middle fan subfacies of alluvial fan of Lower Karamay Formation of a certain block in Karamay Oilfield. Through the algorithm, the 3D simulation result of structure modeling well performed the distributional pattern of the structure and touch relationship of all kinds of structures in horizontal and vertical.

Architecture characterization of alluvial fan reservoir of Lower Karamay Formation in east district 7（1） of Karamay Oilfield

Chen Yukun， Wang Yanjie， Zhu Yating， Liu Hongxian， Zhou Yuhui， Yan Jianing

2015, Vol.27(5): 92–97 Abstract ( 519 ) PDF (2134 KB) ( 419 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.015

1. Research Institute of Exploration and Development ， PetroChina Xinjiang Oilfield Company ， Karamay 834000 ， Xinjiang ， China ；2. Department of Petroleum Engineering ， Karamay Vocational & Technical College ， Karamay 834000 ， Xinjiang ， China ；3. College of Geophysics and Information Engineering ， China University of Petroleum ， Beijing 102200 ， China

Comprehensive evaluation of geological sweet point of tight gas of Shahezi Formation in Xujiaweizi fault depression

Zhang Dazhi， Zhang Xiaodong， Yang Buzeng

2015, Vol.27(5): 98–103 Abstract ( 482 ) PDF (1146 KB) ( 383 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.016

The tight sandstone gas prospecting is a key area of unconventional oil and gas exploration. Shahezi Formation in Xujiaweizi fault depression possesses a geological condition for forming large-area tight gas reservoir. The Shahezi Formation developed in faulted basin, and it is close to the source with features of fast phase change and strong heterogeneity. The following comprehensive evaluation methods for tight gas sweet point were formed preliminarily: sequence study determines its prospective, source rock fixes its potential, reservoir study identifies grade, comprehensive study confirms zone, and sweet point study makes well location. It is considered that Anda area is the preferred favorable zone. The facies such as underwater distributary channel and sheet sand of fan delta front, and underwater distributary channel and channel mouth bar of braided river delta front are favorable development zone for reservoirs. Combined fine seismic interpretation with prestack inversion, 12 sweet point bodies were forecasted in Anda area, which provides an effective guidance for exploration and deployment, and makes breakthrough of tight gas exploration of Shahezi Formation.

A new method of determining grain size based on rock section image

Yuan Rui， Zhu Rui， Qu Jianhua， Sun Yuqiu， Tang Yong， Pan Jin

2015, Vol.27(5): 104–107 Abstract ( 534 ) PDF (496 KB) ( 1954 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.017

Despite technological advances in lab instruments, grain-size analysis has many limitations, such as low speed. A theoretical method of determining grain size based on spatial autocorrelation coefficient of simulated rock section was proposed. Firstly, spatial autocorrelation coefficient was obtained from a group of known distribution grain size of rock section. Secondly, an unknown distribution grain size of rock section was used to calculate spatial autocorrelation coefficient. Finally, linear least squares method about spatial autocorrelation coefficient was solved with constrains. In order to show the feasibility and availability of this method, a serial theoretical rock sections were simulated by random ellipse process. Relationship between spatial autocorrelation coefficient and grain size of simulated rock section was analyzed. With the decrease of offset or increase of grain size of rock section, spatial autocorrelation coefficient is increasing. Grain size distribution of simulated rock section was determined accurately. For example, gritstone was separated into 0.5～1.0 mm, 1.0～1.5 mm and 1.5～2.0 mm, whose computed percentages are respectively 55.8%, 24.6% and 20.2% by the proposed method, closing to the actual values, and the variation trend is same as the actual.

3D geologic modeling technology based on digital outcrop: A case study of reef-shoal body of Yijianfang Formation in Yijianfang outcrop, Tarim Basin

Zheng Jianfeng， Shen Anjiang， Qiao Zhanfeng

2015, Vol.27(5): 108–115 Abstract ( 1034 ) PDF (2580 KB) ( 422 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.018

The 2D models which is based on the traditional outcrop modeling method are conceptual models, andthey cannot meet the production requirements at present. 3D geologic modeling technology based on digital outcrop is more advanced overseas, but it still stays in the start stage in the domestic. Taking the reef-shoal body of Yijianfang Formation in Yijianfang outcrop as an example, this paper measured nine sections, divided into ten stratigraphic units and recognized ten types of microfacies. According to the conventional petrophysical properties, it was found that the development of reservoir is controlled by microfacies, and reef base is advantageous to the development of pores, followed by platformmargin shoal, reef flat and reef frank. Reef core and moderate-high energy shoal are relatively poor, but there are almost no pores in moderate-low energy shoal and interbank sea. Used Lidar to scan the outcrop, and then constructed the digital outcrop by interpreting the stratigraphic boundary and loading the geological information in the laser point cloud. Based on facies-restrained stochastic modeling method, used GoCAD to build up 3D facies model, 3D porosity model and 3D permeability model. These models clearly reflect the distribution of microfacies, porosity and permeability in 3D space, they also can be compared with the underground and can effectively guide the exploration and development of reef-shoal reservoirs in Lianglitage Formation of Tazhong area.

Application of seismic sedimentology to prediction of interbeds in dolomite reservoir: A case study of Penglaiba Formation in Yingmai 32 block of Tarim Basin

Xiong Ran， Yang Cun， Luo Xianying， Qiao Zhanfeng， Cao Peng

2015, Vol.27(5): 116–121 Abstract ( 590 ) PDF (2050 KB) ( 678 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.019

The widely development of interbeds in dolomite reservoir of Penglaiba Formation increased the difficulty of remaining oil mining in Yingmai 32 block in Tarim Basin. Due to the small thickness of the interbed and the unclear distribution regularities, it is difficult to predict the interbed distribution in the study area. Under the guidance of seismic sedimentology theory, techniques such as 90° phase convert after spectrum inversion and strata slice in outcrop modeling were used to predict the distribution rule of interbeds in high frequency sequence stratigraphic framework. The result shows that spectrum inversion can improve the ability of thin layer resolution, and there is a better corresponding relation between seismic event and thin layer. The outcrop modeling determines the distribution rule of interbeds, and there is a better corresponding relation with well data, which can guide the prediction of interbed distribution. The prediction result shows that the interbeds distributed in the northeast of the study area, and they control the distribution of remaining oil. Finally, by well data verification, it proves that the interlayer distribution predicted by this method is accurate and reasonable.

Submarine hydrocarbon seepage and deep oil and gas properties in northern depression, South Yellow Sea Basin

Wang Jianqiang， Li Shuanglin， Sun Jing， Dong Heping， Zhao Qingfang

2015, Vol.27(5): 122–127 Abstract ( 446 ) PDF (1135 KB) ( 370 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.020

Side scan sonar and high-resolution seismic methods were used to analyze the geophysical characteristics of hydrocarbon seepage in the northern depression of the South Yellow Sea Basin, and the acoustic characteristics related to submarine hydrocarbon seepage were discovered, including hemp pit, submarine dome reflector and columnar disturbance. The acidolysis hydrocarbon in the seepage zone of the northern depression was analyzed. The result shows that hydrocarbon gases mainly belong to thermogenic gas. The faults developed in subbottom close to or direct to the seabed provide seepage migration channel and path, and the gas gathering and seepage are resulted from the upward migration of pore fluid in deep formation.

Hydrocarbon accumulation characteristics and main controlling factors in eastern Baiyun Sag, Pearl River Mouth Basin

Xu Hui，Zhang Zhongtao，Li Ruibiao，Liu Baojun，Yan Hui，Yuan Cai

2015, Vol.27(5): 128–134 Abstract ( 464 ) PDF (1786 KB) ( 347 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.021

The hydrocarbon distribution in eastern Baiyun Sag is complex and variable. The hydrocarbon reservoirs in eastern Baiyun Sag own the characteristics of both generation of oil and gas, lower part generating and upper part accumulating; hydrocarbon accumulating in later stage, oil generating in early stage and gas generating in later stage, differential accumulation, as well as oil in the inner and gas in the outer. The main controlling factors for hydrocarbon accumulation are as follows: （1） hydrocarbon-generation depressions are the material basis for the formation of large oil and gas fields, and the activity of detachment faults with low angles in the early stage（rifted period） controls the basin development and the source rock scale; （2） effective traps and favorable migration pathways are two essential conditions for hydrocarbon accumulation, combined together, the inherited fractures and tectonic ridges in the later stage can control the traps and the hydrocarbon migration, and the favorable convergent nose-shaped tectonic ridges are excellent areas for oil and gas migration and accumulation; （3） the development degree of high-quality reservoirs is a critical factor influencing the hydrocarbon accumulation in Lower Zhujiang Formation, and controlled by the migration of short-term cycles of shelf slope break and sedimentary microreliefs, the high-quality sand bodies in multi-period shelf margin delta-deep water fan system with well developed sedimentation are important reservoirs and carrier beds. There are good oil and gas accumulation conditions in eastern Baiyun Sag, so to clarify hydrocarbon accumulation characteristics and main controlling factors is of certain guiding significance for hydrocarbon exploration in this area and adjacent areas.

Tectonic-lithofacies palaeogeography characteristics of Cambrian deep dolomite and exploration prospects in northern Tarim Basin

Ni Xinfeng， Chen Yongquan， Zhu Yongjin， Yang Pengfei， Xiong Ran

2015, Vol.27(5): 135–143 Abstract ( 910 ) PDF (4433 KB) ( 408 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.022

Limited by lacking data points, effective reconstruction of lithofacies palaeogeography becomes one of the critical factors for exploration zone optimization of Cambrian deep dolomite in northern Tarim Basin. The data from 14 drilling wells and 4 outcrops as well as seismic data were applied to discuss the lithofacies palaeogeography characteristics of Cambrian deep dolomite, describe platform margin characteristics and try to clarify facies differentiation inside the platform. The results show that the Cambrian platform margin in the northern Tarim Basin could be divided into Lunnan fault-controlled steep slope type and northern sedimentary type with gentle slope, the sedimentary differentiation is obvious inside the platform, and main sedimentary units such as intraplatform shoal, gypsum-bearing dolomitite flat, gypsum-salt lake and depression can be well recognized. Reservoir-seal assemblage in the Cambrian dolomite is controlled by the characteristics of platform margin and sedimentary differentiation inside the platform, so it is considered that the favorable reservoir-seal assemblages are platform margin reef-shoal, back-reef shoal dolomite and gypsum-salt rock and argillaceous dolomite developed under long-term inherited palaeohigh. The reef-shoal located behind the platform margin belt and near the sea side of the lagoon are favorable reservoirs with caprock of tight carbonate, which can form good reservoir-seal assemblages. Platform margin belt in gentle slope in northern Tarim Basin is a set of dolomite reservoir for algal mound and reef-bank complex with caprock of Middle-Lower Cambrian dolomicrite, gypsum dolomite and mud dolomite and such dense layers, of which the reservoir-seal assemblage is superior to that in Lunnan area and has better exploration prospects.

Distribution characteristics of branch channel of shallow delta in Poyang Lake

Sun Tingbin， Guo Dianbin， Li Zhongchao， Wang Ling， Yin Nanxin， Li Shengyu

2015, Vol.27(5): 144–148 Abstract ( 875 ) PDF (1017 KB) ( 512 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.023

Contemporary delta in Poyang Lake was preferred to quantitatively characterize the sand body distribution rule of branch channel of shallow delta. The branching angle, branching frequency and bending of channel were measured by high-definition satellite pictures. The width variation of the branch channel was studied by intensive sampling on the base of a series of parallel curved profiles vertical to the provenance direction. The result shows that the channel is a dendritic shape with the branching angle being about 30°, and the branching frequency decreases with the advancing of the delta. The channel width has a decreasing tendency with the advancing of the river, and the variation is serious influenced by the branching process. The channel width decreasing rate decreases with the decreasing of the branching frequency; around the branching location, the channel width increases about 108% in average; the branch channel decreases about 49% compared to the width of pre-branching channel.

Sedimentary genesis of sand-conglomerate reservoir and its control effect on reservoir properties: A case study of the lower Urho Formation in Ma 2 well block of Mahu Depression

Pang Dexin

2015, Vol.27(5): 149–154 Abstract ( 870 ) PDF (2008 KB) ( 550 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.024

According to core observation, well logging, logging, casting thin sections and analysis assay data, this paper studied the sand-conglomerate reservoir characteristics of the lower Urho Formation in Ma 2 well block of Mahu Depression. The reservoir lithology could be divided into sand-conglomerate, conglomeratic sandstone, sandstone and shaly sandstones and so on. The sand-conglomerate could be further divided into traction current sand-conglomerate and gravity current sand-conglomerate by the genesis, and they have many obvious differences on the aspects of maturity, muddy matrix content, pore type and so on, which causes the huge differences of reservoir properties. The pore type of sand-conglomerate reservoir mainly is secondary porosity, belonging to low porosity and low permeability reservoir. Sedimentary environment（microfacies） has very obvious control effect on sand-conglomerate reservoir properties, among them, traction current sand-conglomerate of underwater distributary channel microfacies has the best reservoir properties, followed by stream channel microfacies, and the gravity current sand-conglomerate of debris flow and underwater debris flow microfacies has the poorest reservoir properties, which can form property interbeds.

Sequence architecture pattern and hydrocarbon accumulation model of Lower Cretaceous in Wuerxun-Beier Depression, Hailaer Basin

Wu Haibo， Li Junhui， Liu He

2015, Vol.27(5): 155–160 Abstract ( 498 ) PDF (1804 KB) ( 399 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.025

Favorable exploration areas and oil and gas reservoir can be predicted more accurately though the analysis of sequence architecture pattern in different tectonic settings. By the use of core, drilling, logging and seismic data, and accorded to sequence interface characteristics, the Lower Cretaceous in Wuerxun-Beier Depression was divided into 3 second-order sequences and 5 third-order sequences. According to the structural setting, Wuerxun-Beier Depression can be divided into fault controlled steep slope zone, gentle slope fault terrace zone and depression zone. Based on these tectonic units, different sequence architecture patterns were established such as fault controlled steep slope, gentle slope fault terrace and depression zone. Different sequence architecture patterns and sedimentary system tract lead to different hydrocarbon accumulation models. Fault-lithology reservoir and fault reservoir mainly developed in fault controlled steep slope zone, fault-lithology reservoir and stratigraphic overlap reservoir mainly developed in gentle slope fault terrace zone, and lens reservoir mainly developed in depression zone. Moreover, fault-lithology reservoir developed in marginal zone of depression.

Sedimentary microfacies of Neogene Guantao Formation and lower Minghuazhen Formation in L oilfield, Bohai Bay

Xu Zhongbo， Kang Kai， Shen Chunsheng， He Bin， Lin Guosong， Li Lin

2015, Vol.27(5): 161–166 Abstract ( 671 ) PDF (1791 KB) ( 424 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.026

The reservoir petrology and sedimentology of lower Minghuazhen Formation（N1m） and Guantao Formation （N1g） were comprehensively studied by detailed core observation, lab experiment data and geophysical data of 3 coring wells in L oilfield in Bohai Bay. The reservoirs are mainly composed of feldspar sandstone. The sandstone of lower N1m is mainly of medium sorting and subangular-subround roundness, while the sandstone of N1g is mainly of poor sorting and subangular roundness. The sandstone developed various sedimentary structures that can reflect river deposition, including low angle cross bedding, trough cross bedding, erosional surfaces and plant roots. Meanwhile, the variegated mudstone deposited also reflects a kind of shallow weak oxidation-reduction and oxidation environment. Accorded to grain size probability cumulative curves, C-M plot and logging characteristics, the lower N1m mainly developed meandering river deposits that can be divided into point bar, channel, abandoned channel, crevasse splay and floodplain microfacies; whereas, the N1g developed braided river deposits that can be divided into channel bar, braided channel, channel margin and interchannel microfacies.

Characteristics of fault and its controlling on deposition in Shabei structural zone of western Bohai Sea

Wang Mingchun， Li Deyu， Zhang Haiyi， Li Xinqi

2015, Vol.27(5): 167–171 Abstract ( 579 ) PDF (2286 KB) ( 305 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.027

Influenced by the Tang-Lu fault in NE trend and Zhang-Peng fault in NW trend, the most typical conjugate faults developed in Shabei structural zone of western Bohai Sea. Based on the study of the characteristics and evolution of the NE and NW faults, the controlling effect of fault on sedimentation was made clear. The conjugate faults in Shabei structural zone underwent two stages of activities since the Cenozoic: in the Paleogene period, the conjugate faults were strong tension with weak slip and controlled the Paleogene sedimentation; in the Neogene Period, the conjugate faults were strong slip with weak tension, and they did not control the deposition but complicated the structure. Controlling effect of faults on sedimentary filling and sand body distribution are mainly in three forms: fault scarp type, fault ramp type and lateral translocation of fault ramp type.

Hydrocarbon accumulation characteristics under the background of strike-slip faults in Shaleitian uplift, west Bohai Sea

Jiang Tao， Li Huiyong， Li Xinqi， Xu Peng， Hu Anwen

2015, Vol.27(5): 172–175 Abstract ( 548 ) PDF (947 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.028

Based on 3D high resolution seismic data, combined with actual drilling data, the fault characteristics, depositional system characteristics and hydrocarbon accumulation model in Shaleitian uplift were studied. The result indicates that multiple sets of NE striking-slip faults are developed in the study area, which gradually converge to the main strikeslip faults to the deep, and the vertical fault throw is smaller without obvious horizontal displacement showing negative flower structure on profile. Meanwhile, the location of the strike-slip faults corresponds to “groove”, which controls the structural framework of the basement and caprock. The NE trending striking-slip faults plays important controlling roles on the formation of structural trap, the deposition of fan bodies and hydrocarbon accumulation. Structure ridge is a favorable zone for oil and gas accumulation. Affected by strike-slip motion, the main hydrocarbon migration and accumulation model in the east is different from the west. In the east, the slipping is relatively weak, and the hydrocarbon migration type is “structural ridge-fault-sand body” model with traps developing between strike-slip faults. In the west, the slipping is relatively strong, and the lateral hydrocarbon migration type is “gully filling sand-strike slip fault system” model with traps developing attach to the strike-slip faults.

Clastic reservoir characteristics and oil-bearing properties within middle and small-sized basins in the central and western regions of China

Huang Junping， Yang Zhanlong， Liu Hongjun， Di Jun， Huang Yunfeng， Han Xiaofeng

2015, Vol.27(5): 176–182 Abstract ( 648 ) PDF (2338 KB) ( 368 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.029

The oil and gas shows are enriched in middle and small-sized basins in the central and western regions of China, but only few proven reserves were found with low exploration degree. Based on core observation, field outcrop data and experimental analysis, the clastic reservoir characteristics and the controlling factors of oil-bearing properties were analyzed. The results show that: （1） there are developed five sets of clastic reservoirs in the middle and smallsized basins, which are respectively in the Carboniferous-Permian and Triassic strata in transitional facies depositional environment, in the Jurassic coal-bearing strata and Cretaceous non-coal-bearing strata in continental depositional environment, and in the Tertiary strata in alluvial fan depositional environment; （2） the sandstone reservoirs are well developed, but they have poor properties with low porosity, low permeability and low hydrocarbon saturation; （3） the mineral compositions of sandstone reservoir are mainly quartz, feldspar, clay minerals, calcite and dolomite, and different tectonic setting and depositional environment affected mineral compositions of the reservoir; （4） the reservoir space types are rich, including intraparticle pores, interparticle pores, microcracks and organic-matter pores; （5） the oil-bearing properties of sandstone reservoirs are mainly affected by sedimentary facies, rock and mineral compositions, reservoir properties and reservoir space types and other factors.

Numerical simulation of sublacustrine fan deposition of lower Ed₂ Formation and its application in northern Liaozhong Depression

Wei Hongtao

2015, Vol.27(5): 183–188 Abstract ( 456 ) PDF (1814 KB) ( 395 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.030

Sublacustrine fan developed in lower Ed2 Formation in northern Liaozhong Depression of Bohai Bay, but its formation mechanism and space-time distribution rules were unclear. By the use of numerical simulation technology, deposition process and distribution of sublacustrine fan were studied based on the geological parameters including division period, relative lake level change curve and accommodate spatial change model, source supply and transport pattern. The simulation result shows that sublacustrine fan mainly developed in lake flooding system tract, it was formed by the together action of the early instability delta, strong hydrodynamic condition and sedimentary slope break belt, and it is characterized by multi period, double provenance and wide distribution features. Based on the simulation results, combined with macro seismic facies and seismic attributes analysis, plane sedimentary map was drawn, which provides favorable basis for fine reservoir description and prediction of sublacustrine fan.

Hydrocarbon reservoir distribution, accumulation models and main controlling factors in Lixian slope, North China

Zhang Feng， Li Shengli， Huang Jie， Liu Tengguo， Cui Gang， Ren Xiaojun

2015, Vol.27(5): 189–195 Abstract ( 1068 ) PDF (1246 KB) ( 711 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.031

Lixian slope is a structural-depositional slope in the western Raoyang Sag, and it is an important prolific zone for oil and gas accumulation. However, it has many practical problems, such as the variety of oil reservoir types and complexity of hydrocarbon accumulation mechanism. Based on recent petroleum exploration results in Lixian slope, under the guidance of the theories of petroleum accumulation, this paper analyzed the reservoir distribution rule and discussed the accumulation models and main controlling factors in the study area. Lixian slope can be divided into several blocks in SW direction and several belts in EW direction, in which hydrocarbon reservoirs have different distribution models. There are shallow reservoirs in the south with relatively simple types and focused distribution, while in the north, there are middle-deep buried reservoirs with multiple types and scattered distribution. Based on the hydrocarbon distribution rule in different zones and layers in Lixian slope, the various subtle reservoirs in the north and middle zone are the optimal target in the search of large scale reservoirs.

Formation mechanism of sand bodies of the eighth member of Shihezi Formation in northern Ordos Basin

Liu Xiaopeng， Zhao Xiaohui， Kang Rui， Qi Yaling

2015, Vol.27(5): 196–203 Abstract ( 801 ) PDF (2078 KB) ( 460 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.032

In order to clarify the formation mechanism of sand bodies in the eighth member of Permian Shihezi Formation in the northern Ordos Basin, the sedimentary palaeoenvironments including basin character, the connectivity of lake and the outside world, provenance supply and hydrodynamic force conditions were recovered on the base of the characteristics of sand body distribution. Combined with the sedimentary simulation, the sedimentary model of the eighth member of Shihezi Formation was established. The result shows that sufficient sediment supply, strong hydrodynamic force, abundant clastic supplying by several rivers, broad flat topography, stable and rapid basin subsidence and lake level fluctuate with large range are the main factors responsible for the large-area sand bodies of the eighth member of Shihezi Formation. The area from the north of L63 well, S318 well, Y101 well and Y112 well to south of Etuokeqianqi-Yulin area in Ordos Basin is the favorable target for exploration in the future.

Fan delta sedimentation and favorable reservoir distribution of the lower Urho Formation in Ma 2 well block of Mahu Depression

Zhang Youping， Sheng Shifeng， Gao Xianglu

2015, Vol.27(5): 204–210 Abstract ( 582 ) PDF (1810 KB) ( 553 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.033

Based on observation of cores and thin section and property analysis of typical samples, the sedimentary facies of the lower Urho Formation in Ma 2 well block was recognized again, and the development rule and distribution characteristics of favorable reservoirs were studied. The results show that the sedimentary facies of the lower Urho Formation is fan delta which formed as a set of alluvial fan prograded into a lake, not underwater fan deposition, and the sediments generally show an alternate deposition process of tractive current and gravity flow. The sedimentary facies can be divided into 3 subfacies of fan delta plain, fan delta front and predelta, and 10 microfacies of debris flow, sheetflood, stream channel, underwater distributary channel, clastic flow, interdistributay bay, mouth bar, distal bar, prodelta mud and slump, among which debris flow and underwater distributary channel deposition developed very well. The sedimentary microfacies have obvious controlling effect on the reservoir properties and oiliness. The glutenite reservoir developed in the stream channel and underwater distributary channel microfacies is favorable reservoir because of the low content of argillaceous matrix and good reservoir properties. So the glutenite of distributary channel and underwater distributary channel microfacies in each sedimentary period are the first target of oil and gas evaluation and development in the study area in the future.

Reservoir characteristics and controlling factors of deep diamictite in Yingxi area, Qaidam Basin

Chen Dengqian， Shen Xiaoshuang， Cui Jun， Lu Yanping， Huang Yao

2015, Vol.27(5): 211–217 Abstract ( 871 ) PDF (3036 KB) ( 415 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.034

Based on the classification method of diamictite proposed by Zhang Xionghua, the lithology of deep diamictite in Yingxi area of Qaidam Basin was classified simply into three types: carbonatite, mudstone and sandstone. The data of thin section, whole rock mineral analysis, nuclear magnetic resonance and core porosity were used to study the reservoir characteristics of deep diamictite in Yingxi area. The main rock type of the reservoir is micrite limestone（dolomite）, and the minerals include terrigenous minerals, carbonate minerals and clay minerals. The porosity ranges from 0.58% to 8.58%, with the average value of 2.69%, and the permeability ranges from 0.010 mD to 0.501 mD, with the average value of 0.053 mD. The reservoir has the characteristics of low porosity and low permeability, and the correlation between the two parameters is poor. The reservoir spaces mainly include intergranular pores and fractures, with fewer dissolved pores. The content of carbonate minerals and compaction are the main controlling factors for reservoir properties.

Research advances in deep water interaction deposition ： A case from the Pearl River Mouth Basin, northern South China Sea

Li Hua， He Youbin， Wang Yingmin， Pei Yu

2015, Vol.27(5): 218–224 Abstract ( 926 ) PDF (1637 KB) ( 447 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.035

There are complicated and various hydrodynamic forces in deep water zone, which result in abundant types of interaction depositions, such as gravity flow, contour current, internal wave and so on. Types, characteristics and sedimentary models of interaction deposition between gravity flow and contour current were studied in the Pearl River Mouth Basin by seismic data. Gravity flow and contour current are both well active in the study area, where interaction deposition between gravity flow and contour current developed well, including canyon, unidirectional migrating channel, giant elongated drift, confined drift, slope sheeted drift and so on. NE-migrating channel, giant elongated drift and some slope sheeted drift formed in the upper-middle slope, where the gravity flow and northeastward moving intermediate water were active. By contrast, SWW-migrating channel, lobe, channel-levee, giant elongated drift, confined drift and slope sheeted drift developed for gravity flow and deep water controlling in the middle-lower slope. The unidirectional migrating channel is the result from interaction between gravity flow and contour current, whose migrating direction represents the flow direction of contour current. Drift, deflected lobe and asymmetric levee formed by contour current carry, rework and redeposit of gravity flow sediment.

Reservoir property differences of Donghetang Formation in Bachu and Tazhong area

Liu Lu， Peng Jun， Wu Huiming， Zhang Hanbing

2015, Vol.27(5): 225–231 Abstract ( 819 ) PDF (1763 KB) ( 373 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.036

On the basis of rock thin section, cathodoluminescence and physical properties, the reservoir characteristics of Donghetang Formation in Tarim Basin were studied, and the reservoir property differences in Bachu and Tazhong area were analyzed. The reservoir properties in Tazhong area are better than that in Bachu area, and the reservoir is characterized by medium porosity and medium permeability, however the reservoir in Bachu area is tight. The differences are caused by sedimentation and diagenesis. The sedimentary facies in Bachu area is shoreface subfacies with weak hydrodynamic conditions and high content of clay. The Tazhong area developed foreshore subfacies which has strong hydrodynamic conditions and low content of clay. The content of quartz in Bachu area is less than that in Tazhong area, but the debris content is higher, so the reservoir properties are poor. Carbonate cementation in Bachu area is stronger than that in Tazhong area, but dissolution is weaker, and porosity and permeability is low. In Tazhong area, a lot of the early dissolution of carbonate cement formed intergranular dissolved pores, and fractures developed, which results in high porosity and good physical properties.

Geochemical characteristics and origin of Palaeozoic siliceous rocks in Lower Yangtze area

Li Hongjing， Lin Zhengliang， Xie Xinong

2015, Vol.27(5): 232–239 Abstract ( 795 ) PDF (1055 KB) ( 362 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.037

As regional source rocks, the Lower Cambrian, Middle Permian and Upper Permian in Lower Yangtze area developed bedded siliceous rocks. The analysis of geochemical characteristics and origin of the Palaeozoic siliceous rocks in Lower Yangtze area is very important for understanding sedimentary setting of source rocks. Based on the analysis of major elements and rare earth elements of the siliceous rocks from the four typical sections （Lower Cambrian Qingkeng section in Qingyang town, Pingdingshan section in Chaohu Lake, Majiashan section in Chaohu Lake and Changqiao section in Jing county） in Lower Yangtze Wuwei-Nanling area, the SiO2 content of the Lower Cambrian is a little higher than that of the Permian; the siliceous rocks of Lower Cambrian Huangpailing Formation, Middle Permian Gufeng Formation and Upper Permian Dalong Formation have weak negative Ce anomalies, but they have different Eu anomalies. Based on the MnO/TiO2 ratio of Paleozoic siliceous rock, the relation of Fe2O3/TiO2-Al2O3/（Al2O3+Fe2O3） and the rare earth element characteristics in the study area, it is concluded that the sedimentary setting of the siliceous rocks of Upper Permian Dalong Formation is neritic shelf facies. While the bedded siliceous rock of the Lower Cambrian and Middle Permian Gufeng Formation deposited on the marine basin, of which the depositional environment is more closely to the inner of basin compared to the siliceous rocks of Dalong Formation. According to Al/（Al+Fe+Mn） ratio of the bedded siliceous rocks of three layers, the triangular plots of Al-Fe-Mn and rare earth element characteristics, it is considered that the Lower Cambrian siliceous rock is hydrothermal genesis, the Upper Permian siliceous rock is typically biogenic genesis, and the siliceous rock of Middle Permian Gufeng Formation is biological and hydrothermal mixed genesis.

Sedimentary model of lowstand fan group in Lishui Sag

Hou Guowei， Liu Jinshui， Zhou Ruihua， Ye Fang， Li Shuai

2015, Vol.27(5): 240–244 Abstract ( 788 ) PDF (1572 KB) ( 385 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2015.05.038

Based on the analysis of core, tectonic evolvement and source, it is considered that lowstand fan group developed in marine sedimentary environment of lowstand system tract in lower part of Mingyuefeng Formation in Lishui Sag, East China Sea. The established sedimentary evolution model of lowstand fan group shows that the formation process was controlled by sedimentary environments, faulted slope break zone and sedimentary sequence. Oil and gas exploration potential was found in the lithologic reservoir which generated in lowstand fan, which shows the gas potential of Lishui Sag.