石油实验地质

2016, 38(5): .

Abstract(324) PDF-CN(1071)

Abstract:

Lithofacies Palaeogeography of the Middle Ordovician in the eastern North China Platform

Lin Yuxiang, Zhu Chuanzhen, Zhao Chengjin, Wu Yuchen, Li Jia, Li Xiuqin

2016, 38(5): 559-568. doi: 10.11781/sysydz201605559

Abstract(948) PDF-CN(823)

Abstract:
We subdivided the Middle Ordovician in the eastern North China Platform into five level 3 sequences using sequence stratigraphic classification and correlation in order to determine clear sedimentary patterns and evolution characteristics. Sequence palaeogeographic maps of sedimentary facies were drawn, and the coastal evolutions were described using detailed sequence isochronism. Persistent transgression occurred in the eastern North China Platform during the Middle Ordovician. Lithofacies palaeogeography at five different stages of the Middle Ordovician took the appearance of some inherited features coexisting with significant evolution. Paleotopography of five stages kept on pre-senting higher in the north and south, and in central North China there developed a quite complete sedimentary sequence. The paleogeographical environment was influenced by tectonics and sea level changes and the distribution pattern of sedimentary facies in each phase was different. With the growing marine transgression, restricted platform and open platform were prominent. The north-south symmetry of sedimentary facies manifested as a restricted platform located on both sides of the open platform. Overall, it was the sensitive feedback to sea level change of the epicontinental sea coupled with crustal uplift, that controlled the sedimentary cyclicity and rhythmicity of lithologic associations, thus developing favorable source-reservoir-cap assemblages. It is worth mentioning, with beneficial Meso-Cenozoic preservation conditions, the Bohai Bay Basin is the most advantageous exploration area.

Problems with the fine description of reservoirs

Chen Huanqing, Shi Chengfang, Cao Chen

2016, 38(5): 569-576. doi: 10.11781/sysydz201605569

Abstract(799) PDF-CN(493)

Abstract:
The advantages and disadvantages of fine description of reservoirs in China and abroad were discussed and compared. Some problems in the fine description of reservoirs in China were pointed out, such as the multi-explanation of fracture systems, low accuracy of single sand body prediction, and poor prediction of residual oil distribution and reservoir development rules. Six countermeasures were proposed, including basic geologic experiments, reservoir geology origin analysis, new technique application, comprehensive analysis to reduce multi-explanation, reservoir fine description with dynamic thought, and information platform construction.

Three factors controlling petroleum migration pathways:A case study of XJZ oilfield in the Gaoyou Sag, North Jiangsu Basin

Li Heyong, Tian Kun, Qiu Xuming, Liu Qidong, Liu Zhen, Song Liyan

2016, 38(5): 577-583. doi: 10.11781/sysydz201605577

Abstract(784) PDF-CN(319)

Abstract:
The analysis of prevailingpetroleum migration pathways can help evaluate petroleum exploration targets. Three factors control migration pathways, including the heterogeneity of carrier beds, the attitude of migration pathways and fluid dynamic force. A case study was made in the XJZ oilfieldin the Gaoyou Sag, North Jiangsu Basin, to considerthe controlling effects on petroleum migration pathways. Fluid dynamic force plays a core role and controls the direction of petroleum migration. The attitude of pathways constrainsfluid dynamic force. The he-terogeneity of carrier beds determines whether petroleum can migrate and the velocity of migration. Petroleum migration pathways are determined bythe interaction of three factors.

Basin structure and hydrocarbon accumulation conditions of the Weihe Basin

Liu Zhiwu, Bai Yong, Zhou Lifa

2016, 38(5): 584-591. doi: 10.11781/sysydz201605584

Abstract(1143) PDF-CN(131)

Abstract:
The Weihe Basin, which is located in the southern margin of the Ordos massif, is a Cenozoic fault basin. Understanding the basement structure and tectonic characteristics of this basin are pivotal to guide hydrocarbon exploration and resource potential evaluation. In this paper, the basement and tectonic style of the Weihe Basin is studied using regional structural analysis, with comprehensively field geology, drilling, test and geophysical data such as gravity, aeromagnetic, seismic etc. In turn, the hydrocarbon accumulation conditions of this basin are also discussed. The research results show that the pre-Cenozoic basement of the Weihe Basin is mainly composed of four different physical partitions. The tectonic style of the Lower Paleozoic basement is mainly strong fold deformation, which is separated by Cenozoic normal faults. The Cenozoic tectonic style of this basin is a half graben, which is controlled by normal faults. Both the pre-Cenozoic and the Cenozoic of the Weihe Basin have good natural gas reservoir forming conditions.

Re-recognition of hydrocarbon accumulation regularity based on oilfield development data:A case study of the Guantao Formation in NB35-2 oilfield, Bohai Bay Basin

Quan Honghui, Chen Jianbo, Bie Xuwei, Zhang Zhang, Zhang Zhenjie

2016, 38(5): 592-599. doi: 10.11781/sysydz201605592

Abstract(853) PDF-CN(99)

Abstract:
According to the contradiction between production and geological understanding of the NB35-2 Oilfield, Bohai Bay Basin, we re-analyzed paleostructure, depositional features and the reservoir forming model as well as resource potential based on drilling, logging, seismic and production performance data. Paleostructures controlled sedimentary facies and hydrocarbon accumulation in the Guantao Formation. (1) Petroleum migration and accumulation were controlled by palaeogeomorphology of the buried hill area in NB35-2 block, which is different from the previous research results that reservoirs were restricted by lithology rather than structure. (2) Braided river sedimentary facies are predominant in the Guantao Formation. Reservoirs mainly distribute over superimposed, linked areas of main stream channels, and the space distribution of sand bodies is controlled by the secondary accumulation and distribution of oil and gas to some extent. (3) In the NB35-2 oilfield, faults controlled hydrocarbon accumulation, and hydrocarbon mainly accumulated in deep strata and migrated to shallow strata. Boundary faults and unconformities worked as a "resource network" and allowed hydrocarbons to accumulate in the Guantao Formation. Secondary faults were active in the shallow formations during late stage, and made crude oil migrate to the Minghuazhen Formation and form secondary oil pools. The Guantao Formation in the NB35-2 oilfield has a great petroleum potential, and may be 3 times larger than the previous estimation.

Reservoir characteristics and genesis of slope fans in Dongying delta front

Wang Weifeng, Hu Yu, Yu Zhengjun, Chen Jie, Shan Chenchen, Zhang Xiaojie

2016, 38(5): 600-608. doi: 10.11781/sysydz201605600

Abstract(898) PDF-CN(179)

Abstract:
Slope fan refers to a sedimentary sand body which evolved from retransportation of delta or fan delta sand. It is caused by earthquakes and other factors and is transported in the form of slide, slump or debris flow. Based on core description, well logging and seismic data, combined with field investigation and sedimentation simulation, the reservoir characteristics and genesis were summarized. The lithology of a slope fan sand body is mainly fine sandstone and siltstone. Sedimentary structures are characterized by massive bedding, load cast and slump structures. It can be identified as a blocky or finger wireline log. The seismic facies is moundy or sphenoid shaped and the amplitude is moderate to strong. Slope fans are manifested as slide, slump and debris flow sand bodies. According to sedimentation simulation, 7 slope fan styles were differentiated. Combined with the geology of the Niuzhuang Subsag in the Dongying Sag, the distribution of slope fans was forecasted and two favorable prospecting target areas of slope fan were identified.

Characteristics and controlling factors of Jurassic reservoirs in Chepaizi area, western Junggar Basin

Cao Yingchang, Jiang Wei, Wang Yanzhong, Jin Jiehua, Xu Tao, Xi Kelai, Chen Lin

2016, 38(5): 609-618. doi: 10.11781/sysydz201605609

Abstract(934) PDF-CN(149)

Abstract:
We analyzed the characteristics of Jurassic reservoirs in the Chepaizi area in the western Junggar Basin using thin section microscopy, core description and physical property analysis. Combined with the study of petrophy-sical parameter cutoffs, we summarized the controlling factors of reservoirs, and divided reservoirs among types. The results showed that reservoirs in the study area mainly develop five lithofacies including matrix-supported conglomerate facies, particle-supported conglomerate facies, conglomeratic sandstone facies, sandstone facies and siltstone facies. The conglomerate reservoirs had limited reservoir space with very-low porosity and ultra-low permeability. The sandstone reservoirs develop comparatively more reservoir space, mainly primary pores, and show the characteristics of middle to high porosity and permeability. By the quantitative evaluation of diagenesis, we identified 11 diagenetic facies. The properties of reservoirs are mainly controlled by lithofacies, and diagenesis promoted the differentiation of reservoirs. Combined with petrophysical parameter cutoff and reservoir properties, three reservoir types are identified in this area. Type Ⅰ reservoirs are the combinations of (conglomeratic) sandstone facies and medium to strong dissolution diagenetic facies, and the reservoir properties are best. Type Ⅱ reservoirs are the combinations of siltstone facies and weak cementation, weak dissolution diagenetic facies, and the reservoir properties are poorer than type I. Type Ⅲ reservoirs are the combinations of conglomerate or sandstone facies and medium to strong cementation, dissolution diagenetic facies, and the reservoir properties are poorest.

Formation conditions and development model of stratigraphic-lithologic traps in shelf break zone, Pearl River Mouth Basin:Zhujiang Formation as an example

Chen Weitao, Shi Hesheng, Du Jiayuan, He Min

2016, 38(5): 619-627. doi: 10.11781/sysydz201605619

Abstract(778) PDF-CN(122)

Abstract:
The shelf break zone in the south of Panyu Low Uplift and on the northern slope of Baiyun Sag since the Pearl River Mouth Basin came into the post-rifting stage in the Neogene. As the primary gas-producing layer, the Zhujiang Formation was favorable for the formation of stratigraphic-lithologic traps. Stratigraphic and sedimentary facies analyses were made based on 2D and 3D seismic data and drilling information. (1) The paleo Pearl River featured a wide drainage area and abundant detrital material of terrigenous origin. (2) The land surface material of the paleo Pearl River flow domain became loose and activated due to multiple tectonic movements. (3) The paleo Pearl River delta prograded to the shelf break belt because of extensive sea level fall. Due to the influences of these three factors, the paleo Pearl River carried abundant coarse clastic debris to the southern area of Panyu Low Uplift and the northern slope of Baiyun Sag. This clastic debris formed two favorable reservoir-seal assemblages and many kinds of sedimentary bodies at the shelf break zone which had a special palaeogeomorphologic background, and thus provided favorable conditions to the development of stratigraphic-lithologic traps. The stratigraphic-lithologic traps located in the shelf edge delta of a forced regressive system tract and which formed in the slope fan and basin fan of a lowstand system tract are most advantageous for oil and gas accumulation. The stratigraphic-lithologic traps in the transgressive and highstand system tracts have poor conditions.

Segmentation characteristics and evolution of Xinanzhuang fault in Nanpu Sag, Bohai Bay Basin

Sun Simin, Ji Hancheng, Wang Jianwei, Zhang Hui, Chen Liang

2016, 38(5): 628-634. doi: 10.11781/sysydz201605628

Abstract(913) PDF-CN(385)

Abstract:
The vertical displacement of boundary faults along strike during different geologic stages was studied using seismic data as well as tectonic and stratigraphic thickness maps for the Xinanzhuang Fault in the Nanpu Sag of the Bohai Bay Basin. The segmentation and evolution of boundary faults were studied and their controls on sediments were analyzed. During the deposition of the third member of Shahejie Formation, the Xinanzhuang Fault was divided into three individual fault segments from east to west, and relay ramps developed where fault segments overlapped. When the first member of Shahejie Formation was deposited, these individual fault segments were linked, and the fault segment to the north of Gaoliu Fault began to be abandoned. At the end of Dongying period, a unified fault was formed, yet still showed segmentation features. Some transverse folds appeared on hanging wall. The fault segment to the north of Gaoliu Fault was abandoned. Coarse sediments migrated into the basin through transverse folds and relay ramps, resulting in favorable reservoir development.

Petoleum geology features and accumulation controls for ultra-deep oil and gas reservoirs

Huang Juan, Ye Deliao, Han Yu

2016, 38(5): 635-640. doi: 10.11781/sysydz201605635

Abstract(914) PDF-CN(287)

Abstract:
According to previous studies and specific geological settings of different regions, ultra-deep reservoirs have been defined as being 6 km. Petroleum geology studies of ultra-deep reservoirs have been made, including considerations of source rock, reservoir, cap rock and trap. Compared to conventional source rocks, the source rocks in ultra-deep reservoirs entered the mature stage later and have a higher maturity. Hydrocarbon generation was controlled by temperature, time and pressure. Overpressure strongly restricted the thermal evolution of orga-nic matter and hydrocarbon generation. Secondary pores with an older age worked as the main reservoir space. Carbonate rocks account for 33% of reservoir. Cap rocks are dominated by evaporites and mudrocks. The major traps are structural, lithological, reef and combination traps. The formation of ultra-deep reservoirs was controlled by abnormal pressure and temperature. It is suggested that ultra-deep oil and gas exploration in China should focus on the areas with lower geothermal gradients, stratigraphic intervals with secondary porosity and well-developed overpressures, deeply-buried carbonate rocks, sub-salt sequences and East China's deep offshore areas.

Thermal evolution modeling of Neopaleozoic source rocks in Hangjinqi region, Ordos Basin

Zhao Guiping

2016, 38(5): 641-646. doi: 10.11781/sysydz201605641

Abstract(828) PDF-CN(252)

Abstract:
Taking the measured R_o values which reflected the characteristics of thermal evolution degree of source rocks as calibration, the thermal evolution history of source rocks of the Taiyuan Formation and members 1 and 2 of the Shanxi Formation in Neopaleozoic was modeled through erosion thickness restoration and the selection of ancient heat flow. We analyzed well logging data of different strata from more than 70 wells, and established a corresponding geological model. Source rocks reached the threshold of hydrocarbon generation (R_o>0.65%) during the mid-late stage of Late Triassic in Xinzhao, Shilijiahan, Azhen and Haoraozhao areas in the western and southern Hangjinqi region and during the early stage of Early Jurassic in Gongkahan and Shiguhao areas in the northern Hangjinqi region. The thermal evolution degree of source rocks decreases from southwest to northeast in the study area. The maximum R_o values in Xinzhao and southern Shilijiahan are 1.43% and 1.46% respectively, reaching the over-mature stage of evolution. However, the R_o values in Shiguhao and Azhen areas in the northern and eastern Hangjinqi region range from 0.85%-1.0%, showing that the source rocks are still in the early stage of hydrocarbon generation peak.

Geochemical characteristics and significance of bitumen of Ordovician outcrops at the southern margin of Ordos Basin

Jin Xiaohui, Sun Runxuan, Chen Xia, Sun Yipu, Zhang Juntao, Li Shujun

2016, 38(5): 647-651. doi: 10.11781/sysydz201605647

Abstract(608) PDF-CN(261)

Abstract:
Outcrop bitumen occurs in the limestone cracks in the Lower Ordovician Liangjiashan Formation at the southern margin of Ordos Basin. The cracks are nearly vertical. The bitumen zone is about 75 m high and 1-44 cm wide, and is wide at the bottom and narrow on the top. The carbon isotope value of the bitumen is -28‰. Equivalent bitumen vitrinite reflectance ranges from 1.829%-1.965%. The bitumen and the source rocks in the Upper Ordovician Beiguoshan Formation have low Pr/Ph values and high C₂₄ tetracyclic terpane biomarker concentrations. Bitumen samples with C₂₉ sterane predominance and low gammacerane index reveal that hydrocarbon parent materials were formed in a low-brackish water environment from marine plankton. The composition of steroids is "V" type, and the biomar-kers such as C₂₄ tetracyclic terpanes/C₂₆ tricyclic terpanes and Tm/Ts are similar, indicating a genetic relationship. The geochemical characteristics and significance of bitumen of the Ordovician outcrops at the southern margin of Ordos Basin have helpful for the evaluation of the Lower Paleozoic carbonate source rocks.

Stable carbon isotope distribution patterns of kerogen and its derived hydrocarbons constrained by primary biomass

Liu Hu, Liao Zewen, Qi Minghui, Zhang Haizu, Du Junyan, Yang Shan

2016, 38(5): 652-658. doi: 10.11781/sysydz201605652

Abstract(816) PDF-CN(106)

Abstract:
There exists a stable carbon isotope reversal between crude oils and kerogens from the Cambrian-Lower Ordovician source rocks of the Tarim Basin, NW China. To verify the inverse carbon isotopic pattern and probe the possible mechanism, three shale samples with low thermal maturity were used for thermal simulation experiments, two of which were taken from the Neoproterozoic Xiamaling Formation in Xiahuayuan region, North China (one from argil-laceous shale and the other from calcareous shale) and the third one was from the Permian Lucaogou Formation in Santanghu Basin, Northwest China (argillaceous shale). A reversed carbon isotope distribution pattern between kerogen residue and its pyrolysates was observed for the Xiamaling calcareous shale, which was not found for the Xiamaling argillaceous shale or Lucaogou argillaceous shale. A stronger carbon isotope fractionation was found for the pyrolysates from Xiamaling calcareous shale kerogen than those from argillaceous shale kerogens, and then accordingly a weaker carbon isotope fractionation was determined for the pyrolyzed residues from Xiamaling calcareous shale kerogen. Combined with organic petrology and thermal simulation experiments, the “Xiahuayuan algal relic” from Xiamaling calcareous shale was supposed to have a lower hydrocarbon generation capacity than the mineral bituminous matrix from Xiamaling argillaceous shale and the laminated algae from Lucaogou argillaceous shale. Combined with biomarker distribution features, it was suggested that the reversed carbon isotope pattern, between kerogen residue and its pyrolysates, may be ascribed to the contribution of some special biomass (primarily constituted by n-alkanes) of early life, or the isoprenoid compounds were less preserved in the process of biomass sedimentation.

Near-surface geochemical exploration in the Changde inorganic gas reservoir, Songliao Basin

Chen Yinjie, Tang Yuping, Huang Xin

2016, 38(5): 659-664. doi: 10.11781/sysydz201605659

Abstract(714) PDF-CN(52)

Abstract:
The Changde gas reservoir in the Songliao Basin is the only inorganic gas reservoir in the world which mainly produces alkane gas with a full geochemical complement. Therefore, the study of Changde inorganic gas reservoir has a great significance for the development of China's natural gas exploration. We designed a geochemical profile crossing wells Fangshen1 and Fangshen2 above the Changde gas reservoir, studied the near-surface display of different geochemical indicators, and selected effective geochemical methods and abnormal indicators. The analysis of methane carbon isotopes can help judge the inorganic origin of the reservoir.

Hydrocarbon generation potential under different experimental conditions and its petroleum geology significance

Zhang Caiming, Zheng Lunju, Xu Jin

2016, 38(5): 665-671. doi: 10.11781/sysydz201605665

Abstract(599) PDF-CN(242)

Abstract:
Hydrocarbon generation rate and process and the geochemical characteristics of experimental products were compared between formation porosity thermocompression simulation and conventional autoclave simulation of hydrocarbon generation and expulsion. Different experimental conditions of the two methods resulted in various discrepancies of pyrolysis analysis data. At the same temperature, the oil and gas production rate of formation porosity thermocompression simulation is twice of that of the conventional autoclave simulation. Free hydrocarbon (S₁), hydrocarbon generation potential (S₂) and hydrogen index (I_H) of solid products of the thermocompression experiment are higher than those of the autoclave experiment. In a conventional autoclave experiment, high temperature not only accelerates C-C bond cleavage to form hydrocarbon, but also generates bitumen, CO₂ and H₂, which deviates from the natural evolution of source rocks. The experimental conditions (higher fluid pressure, smaller hydrocarbon generation room filled with liquid water) in the formation porosity experiment are more similar to the conditions of real geological evolution. Experimental data show that gas and oil yield is much larger than hydrocarbon potential in the thermocompression experiment, and the solid products after the experiment still have a high hydrogen index. As a result, hydrogen index and hydrocarbon yield in laboratory experiments fail to estimate the real hydrocarbon potential of source rocks. Accordingly, an Oil and Gas Index (OGI) is proposed to estimate the maximum hydrocarbon potential of source rocks.

Features and significance of rearranged hopanes in pyrolyzates of hydrocarbon source rocks

Chen Julin, Zhang Min

2016, 38(5): 672-678. doi: 10.11781/sysydz201605672

Abstract(919) PDF-CN(84)

Abstract:
Pyrolysis experiments were conducted on immature hydrocarbon source rocks from the well PL-1 in the Bohai Bay Basin to study the influence of thermal evolution on the formation of rearranged hopanes as well as the relationships among rearranged hopane parameters and thermal evolution. The experimental results showed that rearranged hopanes displayed various characteristics during different thermal evolution stages. The absolute concentration of rearranged hopanes in pyrolysis at 250℃ increased relative to that of the original sample, and it gradually reduced as experimental temperature increased from 250℃ to 400℃. The higher the degree of thermal evolution was, the greater the proportion of absolute concentration of rearranged hopanes decreased. When the experimental temperature was between 300-400℃, the reduced proportions of the absolute concentration of compounds showed a pattern of 17α(H)-hopane>18α(H)-neohopane>17α(H)-diahopane. In addition, the rearranged hopane parameters (17α(H)-diahopane/17α(H)-hopane) were nearly unchanged at the stage of low mature to mature, nevertheless it gradually increased at the stage of mature to highly mature. The immature to low mature stage is the main stage of the formation of rearranged hopanes. Higher thermal evolution has an influence on the formation of rearranged hopanes to some degree. Moreover, rearranged hopane parameters can be used as an effective maturity index in the stage of mature to highly mature.

Aromatic parameter reconstruction of crude oil maturity and its application in Hala'alate area

Guo Ruichao, Sui Fenggui, Zeng Zhiping, Wang Chao

2016, 38(5): 679-684. doi: 10.11781/sysydz201605679

Abstract(803) PDF-CN(274)

Abstract:
As no experimental method can be adopted to directly measure crude oil maturity, biomarker parameters are usually used as proxies. Common biomarker parameters are mostly applied to make a qualitative analyses, but they may not be applicable to measure high maturity crude oil. High temperature thermal simulation experiments were conducted on low maturity source rock samples to analyze features of liquid aromatic products at different stages of thermal evolution. The relationship between various aromatic parameters and thermal maturity was explored. Experimental results showed that methylphenanthrene and trimethyl naphthalene have significant correlations with thermal maturity. On this basis, some equations for extrapolating various parameters to thermal maturity were established. Thermal maturity of oil sand samples from the Hala'alate area was determined and showed that the Permian, Triassic, and Jurassic crude oil has a lower maturity, while the Cretaceous crude oil has a high maturity.

Analysis of organic acids in crude oil by comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry

Ma Yuanyuan, Jiang Qigui, Song Xiaoying, Qian Menhui, Liu Peng

2016, 38(5): 685-691. doi: 10.11781/sysydz201605685

Abstract(733) PDF-CN(237)

Abstract:
The composition of organic acids in crude oil samples was determined using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC-TOFMS) for the first time by analyzing the deviations of acidic components in crude oil. Aliphatic acids (straight chain monocarboxylic acid, isoprenoid acid, 2-ethyl alkanoic acid methyl esters and straight chain dicarboxylic acid) and naphthenic acids (monocyclic long chain aliphatic acid, 1,4-dimethoxyanthracene, dehydroabietic acid and steroid acid) were detected in crude oil. GC×GC-TOFMS provides a new high resolution geochemical analysis of petroleum acid compositions.

Determining the relative abundance of C₂₆-C₂₈ triaromatic steroids in crude oils and its application in petroleum geochemistry

Zhang Baoshou, Li Meijun, Zhao Qing, Wang Tieguan, Zhang Ke, Xiao Zhongyao, Huang Shaoying

2016, 38(5): 692-697. doi: 10.11781/sysydz201605692

Abstract(791) PDF-CN(253)

Abstract:
Triaromatic steroids (TAS) may be formed by the aromatization of regular steranes. C₂₆-C₂₈ TAS widely occur in crude oils and source rocks. The C₂₆20R and C₂₇20S TAS typically co-elute with each other in m/z 231 mass chromatograms of aromatic fractions. Therefore, the relative abundance of C₂₆, C₂₇ and C₂₈ TAS cannot be determined by routine GC-MS analysis. A ternary diagram similar to that of C₂₇-C₂₈-C₂₉ regular steranes cannot be established to classify oil families, which leads to the limited use of TAS in petroleum geochemistry. This paper proposed a simple method to estimate the relative abundance of homologues and isomers of TAS on the basis of the distribution patterns, origin and thermal evolution of TAS isomers. Taking representative Paleozoic oil samples from the tectonic region of the Tarim Basin as an example, this paper distinguished two petroleum populations on the ternary diagram of C₂₆-C₂₇-C₂₈ triaromatic steroids determined by routine GC-MS analysis. The oils from the Fushan Sag in the Beibuwan Basin (South China Sea) have different distribution patterns of TAS. The oil family classification is also consistent with that by other molecular markers. For their relatively higher thermal stabilities, triaromatic steroids are generally present in significant abundance in oils and condensates with high maturity. Therefore, this ternary diagram of aromatic steroids is a potential geochemical indicator for oil-to-oil correlation and oil family classification as a substitute for that of regular steranes.

Resource calculation methods for multilayer traps:Case study of two-layer traps

Yang Shuang, Yan Xiangbin, Liu Zhipeng, Cai Lixue, Ma Xiaojuan

2016, 38(5): 698-702. doi: 10.11781/sysydz201605698

Abstract(813) PDF-CN(206)

Abstract:
Volumetric method is a formal way to predict the in-place or recoverable resources of a play or trap, including deterministic and probabilistic methods. Probabilistic evaluation is an optimal way for the assessment of resources in tectonic traps, but the resource assessment of targets with multiple strata is usually calculated by directly and simply cumulating the resources of individual targets using given specified success probability weights. This prediction generally does not correctly reflect actual geological conditions. Taking into account the risk of each target stratum in the trap, we analyzed the geological correlation between each target, including non-correlation, partial and complete geological correlation, and calculated the probability of in-place resources under different conditions. Then the risked resource in-place is divided by the probability of hydrocarbons existing in at least one of the targets to obtain the resource volumes of multilayer traps.

Xu Kewei

2016, 38(5): 703-703.

Abstract(416) PDF-CN(333)

Abstract:

2016 Vol. 38, No. 5

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