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    20 October 2009, Volume 23 Issue 5
    Engineering Geology and Environmental Geology
     Characteristics of Offshore Tidal Deposits in the Lower Tertiary Zhuhai Formation, Huizhou Depression, Pearl River Mouth Basin
    DENG Hong-wen ZHENG Wen-bo
    2009, 23(5):  767-775. 
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    Previous studies consider that Zhuhai Formation in southwestern Huizhou depression was formed in the braided delta environment, or dominated by delta front which experienced transgressive reworking. Based on the palaeogeographic background analysis,the detailed observation and description of cores, combined with the analysis of lithofacies, electro-facies and seismic facies, this study reveals that deposit of Zhuhai Formation rich-in sand supplied by the Pearl River delta experienced reworking of strong tides, and is dominated by tidal sedimentation. In this paper, tidal sedimentary structure, sedimentary sequence and facies succession of inter-tidal and supratidal facies have been detailly described. The regional distribution of depositional system in the study area has been revealed based on facies analysis of single well, combined with regional seismic facies analysis. This new understanding will be favorable for oil and gas exploration and development in this area.

    Sedimentary Facies Analysis and Lithologic Trap Prediction in Highresolution Sequence Framework of Qingshankou Formation, Dabusu Area, Southern Songliao Basin
    2009, 23(5):  776-782. 
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    Due to the slope background and delta front sandbodies, there are favourable conditions for lithologic trap in Qingshankou Formation of Dabusu area in Songliao Basin. Nine sand groups are divided in intended interval with the method of high-resolution sequence stratigraphy. Delta front, turbidite fan and semi-deep lake are recognized through facies analysis, which are further identified as distributary channel, mouth bar, sheet-like sand, turbidite channel, turbidite sheet-like sand and semi-deep lake mudstones. Constitution and distribution of sedimentary facies are analyzed in each sand group which are based on high-resolution sequence framework. As a result, there are more mouth bar in the sand groups which belong to base-level falling hemi-cycles, whereas more distributary channel in the sand groups which belong to base-level rising hemi-cycles. In studied section, the sandstones in middle and lower part are thicker than those in upper part. The sandbodies are distributed along SW-NE direction and mainly located at the south-western part of the study area. Laterally, the sandbodies turned to be thinner and extinguished to upper direction of NW slope. Based on sedimentary facies distribution and other oil and gas forming conditions, we can draw a conclusion that structure-lithologic trap which are formed due to combination of sandbody distribution and nose structures are the main plays; furthermore, three plays are predicted in Dabusu area, south of Songliao Basin.

    Sequence Stratigraphic Framework and Sedimentary Facies Distribution of the Lower Cretaceous in Chagan Depression,Inner Mongolia
    LI Ren-Fu, CHEN Qing-Tang, FAN Ying-Feng, WANG Shi-Kun, FENG Ru-Jin
    2009, 23(5):  783-790. 
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    Comprehensively using the lithologic association, drilling core, logging, geochemistry and palaeontology data, combining structural evolution and seismic reflection feature, 7 third-order sequence boundaries are identified and 6 sequences,16 system tracts are classified in Lower Cretaceous of Chagan depression. In the early phase, sequences in the south and west were thicker. Lately, the depocencer migrated to the north, and the sequences of the west and north were thicker. The sedimentary framework was different between the west and east in early phase because of the Maodun sub-arch, but subsea apron, fan delta and braid river delta were the main depositional system totally. Lately, Maodun sub-arch deposited to alluvial plain, bet lands, and fluvial facies. Three source rock-reservoir-cap rock assemblages in Lower Cretaceous  were developed. In the lower part, the reservoir of the LST was covered by the mudstone of the TST and the selfgeneration; selfreservation source rock-reservoir-cap rock assemblage was formed. In the middle part, the reservoir developed in the HST of the SQ2 and the LST of the SQ3. The reservoir  in the upper part consists of clastic rock of SQ4-SQ6 and volcanic rocks.

    Sequence Stratigraphy and Reservoir Prediction of Tidal Deposits in Zhuhai Formation of Block A, Huizhou Depression
    ZHENG Wen-Bei, ZHENG Hong-Wen
    2009, 23(5):  791-796. 
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     During the period of Zhuhai Formation deposition in Huizhou depression, marine transgression from the southwest seaway entered the depression. The sediments supplied by Paleo-Pearl River Delta from the northwest in this area were transformed by tidal current and then offshore tidal deposits were formed. Tidal flat sedimentation was dominated in  Block A of the study area. Using high-resolution sequence stratigraphy principle,medium-scale stratigraphic cycles which response to base-level cycles are recognized in Zhuhai Formation by the analysis of sedimentological and stratigraphic responses to A/S value changes based on cores and well logs. With the guidance of tidal deposition model, tidal reservoir sandstones are predicted in chronostratigraphic framework by using seismo-sedimentological analysis methods and stratigraphic slice technology,optimization of seismic attributes based on 3-D seismic data in the study area, which provides more evidences for oil and gas exploration and development in this Block.

    Research on High-resolution Sequence Stratigraphy and Prediction to Lithologic Traps of the Qingshankou Formation in Yueliangpao Area of the Southern Songliao Basin
    TANG Zhen-Xin, SONG Lei, YANG Guang, XU Fei-Long, JING Xiao-Feng
    2009, 23(5):  797-802. 
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    Yueliangpao area is located in the delta front of western slope in southern Songliao Basin.  Under the influence of slope and provenance, stratigraphic correlation, sedimentary facies recognition and lithologic trap exploration are hard to perform. By establishing high-resolution isochronous stratigraphic framework and re-analyzing regional sedimentary evolution model, several sets of updip pinchout seismic reflection axis are identified in the interior of Qing 1st and Qing 2nd sequence, and Qing 3rd sequence. Further research proved that these seismic reflections are responses of multiplestage overlay delta front deposition of Gaotaizi oil reservoir in Yueliangpao area, where stratigraphic overlap trap are well developed. Therefore, the 3-D seismic technology can be used to describe the distribution form and range of lithologic trap. The theory of highresolution sequence stratigraphy plays an important guiding part in the exploration of the lithologic oil reservoir in Yueliangpao area.

    Sequence Stratigraphic Framework and Sedimentary Facies of Yanchang Formation, Triassic System in Ordos Basin
    WANG Ji-Feng, GUO Yan-Ru, ZHANG Yan-Ling, LIU Hao-Wei, MA De-Bo
    2009, 23(5):  803-808. 
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    In terms of the principle of high resolution sequence stratigraphy, sequence boundary marks are determined and two kinds of sequence boundaries of unconformity and shift surface of deposition are identified according to outcrop, core, logging and seismic data in Yanchang Formation, Upper Triassic System in Ordos Basin. There are seven sequence boundaries which classify six long-term base level cycles further in the basin. Based on stacking modes of short-term to medium-term base-level cycles, stratum mode of sequence SQ1 to the rising stage of sequence SQ3 is mainly composed of rising stage of long-term base level cycles which composed rising asymmetry cycle configuration. Stratum mode of the falling stage of sequence SQ3 to sequence SQ6 is mainly composed of falling stage of long-term base level cycles which composed falling asymmetry cycle configuration. Sedimentary facies and its distribution are mainly controlled by the change of base level. Sedimentary micro-facies are mainly composed of (braided) river and distributary channel of delta front. Favorable sandbo- dies are mainly distributed in the lower to middle stage of longterm base level rising cycles and the middle to upper stage of long-term base level falling cycles.

    Stratigraphic Sequence Division and the Characteristics of Sedimentary System of Lower Cretaceous in Yinger Depression, Jiuquan Basin
    HOU Xiu-Lin, GU Li-Bing
    2009, 23(5):  809-815. 
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    Guided by the methods of sequence stratigraphy and based on the seismic data, drilling and well logging data, other people's research on the sequence stratigraphy in Jiuquan basin, this paper analyzes the characteristics of the third-order sequence well logging, and recognizes the criterion of the third-order sequence boundary in seismic section, such as local truncation, onlap, and so on. From all this study above, the sequence boundary can be identified, and we recognize 1 first-order sequence, 3 second-order sequences, 7 third-order sequences and 18 system tracts. According to the sequence stratigraphy study, we conclude that the Xiagou Formation of the Lower Cretaceous in Yinger depression has the characteristics of near more provenances, rapid subsidence, and rapid deposition. The mild slope of the depression develops large scale fan deltas, and the steep slope develops nearshore subaqueous fans. Among these, the nearshore subaqueous fan in the south steep slope should be a favorable exploration target.

    Downfaulted Sequence Stratigraphy and Hydrocarbon Reservoir Forming Characteristics of Wunan Sub-depression in the Hailaer Basin
    WEN Wu, DENG Hai, GONG Yong-Jie, WEI Guo-Qing
    2009, 23(5):  816-821. 
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    We analyzed the sequence stratigraphic framework, internal sedimentary characteristics and its controlling factors in Wunan sub-depression based on sequence stratigraphy principle. There are three third-order sequences in Wunan sub-depression during rift period. Each sequence is integrated in the sag and is denudated partially in Wudong ramp region, and the distribution range is controlled by faulted slope-break belt. Hydrocarbon source rock consists of high system tract and half deep lake facies in depressed stage. Main reservoir consists of the sand body of fan delta front and braided stream delta front which is present in high system tract or low system tract in lower part of Nantun Formation. The enriching belts of structural-lithological reservoir in Wanan sub-depression are due to the effective matching between source rock and reservoir. Hydrocarbon distribution shows zonation. The middle slope break is a main enrichment zone, and lower part of Nantun Formation is the main oil concentration area, which is a primary exploration area.

    Petrofacies Palaeogeography and Evolution of Ordovician  of Qilian Sea Area in Ordos Basin
    HAN Pin-Long, ZHANG Ru-Qiao, FENG Qiao3, GAO Jian-Rong, ZHANG Man-Sha,WANG Hong
    2009, 23(5):  822-827. 
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     Based on the investigation results of outcrop, especially considering the  universal existence of Pingliang Formation shale in western and southern Ordos Basin, combined with the outcrop and well information, this paper systemically studies the sedimentary environment of Qilian Sea of Ordos Basin in Early Paleozoic Ordovician, and lithofacies palaeogeography of every sedimentary period is reconstructed. Affected by the formation of the central paleo up-lift and Qilian Sea's invading gradually toward east, the lithofacies paleogeographic framework of Ordos Basin totally showed that open-sea platform, limited sea platform and evaporating platforms were successively distributed during Majiagou age 1, Majiagou age 2 and Majiagou age 3. During Majiagou age 4 and Majiagou age 5, shallow-water carbonate facies, especially edge slope facies and shoal reef facies, were developed and they will be the potential reservoirs. During Majiagou age 6 and Pingliang age, the maximum regression occurred, and open-sea facies and deep-sea basin facies were developed. The graptolite shale of Pingliang Formation is good source rock. The study of the lithofacies paleogeography of Ordovician in Ordos Basin has important significances in both geological theory and production.

    Analysis on Main Diagenesises and Controlling Factors of Carboniferous Carbonate Reservoirs in the Eastern Margin of Pre-Caspian Basin
    DIAO Zhong-Beng, MAO Xiao-Qing, CHEN Li
    2009, 23(5):  828-834. 
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    The Pre-Caspian basin is one of the largest oil and gas bearing basins in the world, and the Carboniferous Carbonate reservoirs in the eastern margin are favorable hydrocarbon reservoirs. Based on study of main diagenesises and controlling factors of Carboniferous carbonate reservoirs of  Kenjiyak and the central block of Zananor oil field, the paper showed that the dorag dolomitization is one of the most important and common genetic types of dolomite, and dolomite formed by dorag dolomitization is the most favorable reservoir. Dolomitization is closely related to the sedimentary environment,  and to some degree, the distribution of dolomite may be regarded as an indicator for microfacies. The mobility of the pore water is different in each depositional environment and facies zone, so diagenesis has different influence on the development and evolution of porosity in each facies zone. Sedimentation is the determinative factor which affects the quality of reservoir and different diagenesises is in connection with the distribution of sedimentary microfacies. The closer to the Carboniferous unconformity surface, the more  favorable diagenesis and tectonizations will take place.  As a result,  the upper Carboniferous carbonate reservoir of the margin of the Pre-Caspian basin is the most promising hydrocarbon reservoir and it is expected to find more oil and gas reserves there.

    Characteristics and Physical Property Evaluation of Shoreline-Tidal Depositional Reservoirs of Lower Zhujiang Member and Zhuhai Formation in Block A of Huizhou Depression, Pearl River Mouth Basin
    ZHAO Ning, DENG Hong-Wen
    2009, 23(5):  835-842. 
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    Based on sedimentology and high resolution sequence stratigraphy, lithology and physical property characteristics of shoreline-tidal reservoirs of Lower Zhujiang Member and Zhuhai Formation in block A of Huizhou depression, Pearl River Mouth Basin, were discussed by the observation of thin sections and SEM, the analysis of logging and geochemistry, and so on. Most of deposits of Zhuhai Formation are formed in tidal environment, and the main rock type is lithic subarkose; most of deposits of Lower Zhujiang Member are formed in shoreline environment, and the main rocks type is lithic arkose, and shoreline deposits with less mud, were well developed in western area; tidal deposits with more mud, were well developed in the eastern area. According to the observation of thin sections and SEM, and experimental analyzing data, primary intergranular pores are the major pore types in reservoirs. The ratio of primary pores in the west is higher than that in the east, the physical property in the west is better than that in the east, and the physical property of shoreline deposits in Lower Zhujiang Member are better than that of tidal deposits in Zhuhai Formation. With the analysis of digenesis, it is regarded that depositional environments, controlled by base level cycle frameworks, is a major controlling factor in reservoir physical properties. Meanwhile, for the depositional system of shoreline and tide, the physical property, from foreshore-lower shorefaceupper shoreface-intertidal sand flat-subtidal channel-intertidal mixed flat-intertidal channel-subtidal sand bar to supratidal mud flat, gradually becomes worse, and the physical property of shoreline sands is superior than that of tidal sands.
                 

    Palaeostress Judgement of Tectonic Fractures  in Chang 61 Low Permeable Reservoir in Yanhewan Area, Ordos Basin in Main Forming Period
    ZHOU Xin-Gui,ZHANG Lin-Yan, HUANG Chen-Jun, LIU Ge-Yun, WAN Xiao-Long,YAN Xi-Li
    2009, 23(5):  843-851. 
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    It must be definitely replied to the forming time of tectonic fracture in reservoirs and the state of palaeostress in estimating and predicting work. According to the method of acoustic emission(AE) palaeostress measurement, the effective percentage of the maximum principal stress can be concluded  in the history of palaeo- structure.The AE measurements reveal that  the corresponding maximum principal stress is in the range of 80 to 98 MPa in Chang 61 low permeable reservoir of Upper Triassic in Yanhewan area, Ordos Basin.Based on the result of palaeostress stage,the thermometry measurement of fracture filling inclusion and the evolution characteristics of regional stress field, it can be confirmed that the tectonic fractures form at Yanshanian movement.By the measurement of the strain of the conjugated fissures located in the outcrop area or the overlay area, the triaxial stress state in Yanshanian is resumed in this area.The direction of the maximum principal stress is NW-SE direction, predominant direction is 129°∠10°, the predominant direction of the minimum principal stress is 36°∠7°, the intermediate principal stress is approximate vertical.Those results can provide some references for prediction of tectonic fracture in low permeability reservoirs.

    Analysis of the Lower-Middle Ordovician Reservoir Tectonic Stress Field Using FMI Data in the South of Tahe Oilfield
    DING Wen-Long, QI Li-Xin, LV Hai-Tao, YANG Guo-Qing
    2009, 23(5):  852-859. 
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    The drilling result shows the distribution and quality of Lower-Middle Ordovician carbonate reservoirs overlaid by Upper Ordovician in the south of Tahe Oilfield are mainly controlled by faults and fractures, with structural open fractures predominantly, drilling-induced fractures secondly.The fracture orientation is closely related to paleotectonic stress field.This paper employs a large amount of FMI drilling data to recognize and analyzes fractures orientation and their origin. It shows that drilling-induced fractures are controlled by present stress field, while the structural open fractures are controlled by paleotectonic stress field.The orientation of fractures is consistent with the maximum principal stress.The predominant orientation of drilling-induced fractures in the south part of Tahe Oilfield is northeast trend, present maximum principal stress is northeast trend, while the structural fractures predominant trend in north-northeast direction and north-east-east direction.Some of north-north-east trend fractures were filled, suggesting they formed earlier than north-east-east fractures and their forming time is corresponding to middle-Caledonian and early Hercynian paleo stress field respectively.

    Fault Nature of NorthWest Fault Zone in Yitong Basin and Its Relation with Reservoir Accumulation
    JIANG Tao,QIU Yu-Chao,SONG Li-Bin,MIAO Hong-Bo,YANG Shan-Min,ZHANG Kun-Peng
    2009, 23(5):  860-864. 
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    The fault nature of north-west area in Yitong Graben used to be obscure,which heavily impedes the oil prospecting works in this area. By using outcrop, core,geophysical data, it is concluded that north-west fault zone in Yitong Basin is compressive and reversed faults which are well developed. A lot of fold structures are shaped at geological outcrops in north-west area of the basin. In prospecting wells near north-west boundary core data show that strata tilted at a large angle, and some even turn perpendicular. Gravity, magnetic and geo-electrical data also show that north-west area in Yitong Graben exits compressive phenomena. Fault composite characteristics are interpreted from high resolution 3D seismic. Fault nature and its characteristics are favorable for reservoir accumulation in the area. This study greatly guides oil exploration of north-west area in Yitong Graben, and also has a guiding meaning to oil prospecting vista of the entire Tancheng-Lujiang fault zone.

    Methods and Application of Paleo-geomorphologies Rebuilding:An Example of the Second Member of Shahejie Formation, Zhuangxi Area, Jiyang Depression
    JIANG Zheng-Long, DENG Hong-Wen, LIN Hui-Xi, WANG Lin
    2009, 23(5):  865-871. 
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    This study applied the principle and methods of compaction restoration for reconstructing paleo-geomorphology of the Second Member of Shahejie Formation in Zhuangxi area of Jiyang Depression. The analyzing processes include four steps: (1) correcting of apparent thickness; (2) establishing of compaction equations;(3) restoring compaction of formations in each single drilling well; (4) composing maps of thickness of original layer and paleogeomorphology. As a result, the minimum value of correction coefficient for the real thickness was calculated as 0.83, based on structural map of the top of the Second Member of Shahejie Formation. The compaction rates are generally higher than 30%. Furthermore, the paleo-geomorphological maps of the Second Member of Shahejie Formation during uplift and subsidence sedimentary periods in Zhuangxi area were compiled. One highland in the middle and two sags in the eastern and the western sides of the Zhuangxi area were recognized from the maps. Beach bars occurred mainly along the two sides of Gubei paleo-uplift, suggesting the formation and development of beaches were clearly controlled by paleo-morphological uplift.

    Characteristic, Geologic Meaning and Forming Mechanisms of the Structrual Accommodation Zones in Wuerxun-Beier Depression
    QIN Yan-Qun, DENG Hong-Wen, DING Han-Sheng
    2009, 23(5):  872-879. 
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    After setting up recognition marks and boundary confirmation, two first-order and eighteen second-order structural accommodation zones can be identified by using seismic and well data and analysis of fault chara cteristics in K1n stage of the Wuerxun-Beier depression. Four types were determined, including transverse accommodation zones, synthetic overlapping, synthetic approaching, antithetic paralleling. This study results show that along the strike of tensional faults, structural accommodation zones which developed on the weakness zones of the basement, were caused by regional disharmonic extension strain and the model of lateral fault developed. The  “S” plane distribution and structural pattern, migration of subsidence center and thickness of sediments were controlled by structural accommodation zones, most of which are advantageous zones for oil and gas accumulation. Directions of provenance system in secondary depression were controlled by the model of lateral fault, strike ramp, vertical uplift and double direction accommodation.

    Closure Property and Evolution of Faults in Fuyu Reservoir in Chaochang Area of Daqing Oilfield
    ZHOU Yong-Bing, WANG Xiu-Juan, SHEN Xu-You, WANG Hai-Qiao, GUO Yan-Ping
    2009, 23(5):  880-886. 
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     Using Allan graphic method, shale smear factor method and fault gouge ratio method, this paper studied the lateral sealing characteristics of 8 faults in Fuyu reservoir in Chaochang area, Daqing oilfield. By use of the normal pressure of fault section and the intensity limit of plastic deformation of mudstone, the vertical sealing characteristics of these faults are studied. The lateral and vertical sealing degrees of these faults are identified in Nenjiang stage, later Mingshui stage and nowadays. Except fault No.6, other faults were opening in later Nenjiang stage, so it is easy to delivery oil and gas from Qingshankou source rock, and the nearby region of fault No.6 is lack of oil sources. Up to present, except fault No.5, other faults are sealed, these sealed faults play a role of barrier to hydrocarbon migration from the already existing reservoir. Because fault No.5 is lack of effective blocking for hydrocarbon migration in three periods, so it basically serves as a channel.

    Forming and Distribution Regularity of the Structural-lithologic Composite Traps in the Shinan Steep Slope Zone, Bozhong Sag
    XU Chang-Gui, ZHOU Xin-Huai, YANG Bo, WANG Xin
    2009, 23(5):  887-893. 
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    The steep slope zone is an important structural belt for hydrocarbon exploration in half graben-like sag, and the structural-lithologic composite traps are developed in this zone. These  traps are important prospecting areas. However, it is very complex in structure, sedimentary facies and control factors on distribution of the structural-lithologic composite traps in this zone. Taking Shinan steep slope of Bozhong sag as an example, this paper focuses on the genesis and distribution regularity of the structural-lithologic composite traps in the steep slope zone. There are four types of structurallithologic composite traps developing in the Shinan steep slope zone, and they are updip punch-out trap, downdip punch-out trap, lateral punchout trap and physical property sealing trap. The distribution are controlled by the types and location of slope break zones, collocation relations of direction of drainage system and palaeogeomorphology, and as well as base level change. The steep slope break zone showing corner-like in plane is the most optimal field of the hydrocarbon exploration of the structural-lithologic composite trap. The structural-lithologic composite traps, which develop in the various series of strata and are distributed widely, are helpful to supplement shortages of the singular structural trap slope zone and reduce the exploration risk of the Shinan steep slope zone.   The thinking of the structural-lithologic composite trap exploration should be built in the early exploration phase in the Shinan steep slope zone.

    Hydrocarbon Migration and Accumulation Direction and Distribution of Linnan Sag in Jiyang Depression
    LIU Hui-Min
    2009, 23(5):  894-901. 
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    Research results of the impact of tectonic stress field, fluid potential, fault plane morphology and its matching relation with attitude of carrier bed to hydrocarbon migration and accumulation show that, dominant migration hydrocarbon direction in Linnan sag, Jiyang depression is chiefly from generating sag to the surrounding, mainly NS direction. To Linshang and Xiakou fault zones, fault concave surface of hanging wall, fault convex ridge, convex surface of hanging wall and the ridge formed by carrier bed and fault surface became the dominant migration pathway and direction of hydrocarbon migration and accumulation; The overall performance of oil and gas reservoirs distribution is along the dominant migration pathway and direction as “fruits along the vines”, “flowers along the sticks”; The lateral sealing of fault led to oil-bearing differences in different locations, structural styles differences led to different accumulation modes in different basin structural units

    Prediction of the Deep Natural Gas Potential of Changling Fault Depression,Songliao Basin
    YAN Wei-Feng, LI Jian-Zhong, WANG Li-Wu, ZHANG Qiang-Chun1, Yang-Tao1, Ma-Yan,
    2009, 23(5):  902-907. 
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    The deep beds of Changling fault depression is characterized by rich natural gas which can reach from 1.14×1012  to 1.71×1012 m3(the average value is 1.42×1012 m3) according to the results of petroleum system simulation. The hydrocarbon gases and CO2 are distributed in different areas: the east part of the depression is rich in hydrocarbon gases; the west part is rich in CO2; the middle part is rich in the both kinds of gases. The distribution of hydrocarbon gases are controlled by source rocks, while the CO2is closely related to the volcanic rocks and major basement faults. The comprehensive evaluations show five favorable regions, among which one is belong to typeⅠ, three belong to type Ⅱ, one belong to type Ⅲ. The typeⅠand type Ⅱ are the favorable regions to explore for the next step.

    Meso-Cenozoic Source Rock of Chelif Basin in Algeria
    ZHANG Chun-Shu,WANG Yue,ZHANG Yuan-Fu,GUO Ling, LU Yu
    2009, 23(5):  908-915. 
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     There was no breakthrough in exploration of Chelif Basin for nearly half a century, and whether effective source rocks existed or not had become the main factors of controlling exploration. According to the geochemical analysis of samples collected from outcrop and drilling core, characteristics and distribution of Meso-Cenozoic source rock were studied and forecasted. New technology to calculate TOC value by using ΔlogR could make up for the inadequacy of samples.As a superimposed basin of Meso-Cenozoic in the northwest of Algeria, Chelif Basin, at the passive continental margin in the period of Cretaceous, was in an extentional structural environment and was a marine facies basin. Chelif Basin evolved into inter-mountain basin in the period of Cenozoic, experiencing fault sag evolutionary process, and was characterized by fast-filling depositional features. The results show that: Upper Cretaceous, Lower Miocene and Upper Miocene source rocks developed, which were moderategood source rocks according to the abundance of organic matter. Type of organic matter was II kerogen, in low mature-mature phase. Upper Cretaceous marls were the main source rocks of Chelif Basin. Hydrocarbon resources were relatively rich, and the basin was a prospective area to explore in the next step.

    Geologic Characteristic of Hydrocarbon in the Passive ContinentalMarginal Basins of South America
    GUO Jian-Yu, HAO Hong-Wen, Li Xiao-Ping
    2009, 23(5):  916-922. 
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    The passive continental marginal basins of South America have developed into one of the most active regions for petroleum exploration. The passive continental marginal basins of South America formed in Late Jurassic-Early Cretaceous as Gondwana land splitting, underwent pre-rift stage, synrift stage, transitional period and drift episode, formed sets of generating rock and reservoir-cover rock compages. Lacustrine generating rock of synrift periods is the most important oil source rock. Salt rock of transitional period dominated hydrocarbon reservoirs generation. Almost major fields were found in recent years, situated in continental clastic container rock and lacustrine carbonate rock. The passive continental marginal basins of South America were classified into three levels by hydrocarbon potential. The largest petroleum accumulations are situated in central south offshore of Brazil. Along with exploration technical progress, it presents well feasibility in this area to prospect reservoirs.

    A Typical Case of Heavy Oil Pool with the Origin of CO2 Deasphaltizing
    GAO Jin-Yu,Shi Bu-Qiang,WANG Lin,DOU Li-Rong,CHENG Ding-Sheng,Pan Xiao-Hua
    2009, 23(5):  923-927. 
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    Gas deasphaltizing is one of the main factors to generate the asphalt mattress or to decrease oil API gravity in oil reservoir. Taking Palaeogene oil reservoir in ME basin of Sudan as an example, on the basis of analysis of the geologic characteristics of reservoir, physical properties and geochemical characteristics of crude oil, components of solution gas, this paper indicated the positive correlation betweenCO2content and API gravity of crude oil, and deduced that the lower API gravity of crude oil should be deasphaltized by CO2 washing or invasion, which was validated by Raman spectroscopy analysis of oilbearing inclusions;and the resource of biogeneticCO2could be derived from adjacent deep faults which penetrated lower crust or upper mantle.

    Amelioration of Seismic Impedance Inversion Methods and a Tentative Practice of Three Stages and Nine Steps Inversion Method
    WU Hai-Bo, WU He-Yong, ZHANG Yang, NIAN Jing-Bo
    2009, 23(5):  928-932. 
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     In recent years, seismic wave impedance inversion method plays an important role in reservoir prediction,which are the primary technology to ensure the proper integration of seismic data, well-logs, velocity and geological information. In this paper, we have overall analyzed and contrasted of the key technology and applicability of five types seismic wave impedance inversion methods commonly used in petroleum industry. Existing wave impedance inversion methods have different applicability, and there are the problems of seismic oil reservoir prediction due to the restriction of seismic data quality, geological condition, exploitation degree. These problems could not be preferably solved. Furthermore, we presented a thought for seismic inversion called three stages and nine steps inversion method. With this method, the good effects of appliance are acquired in exploration deployment and reserve evaluation of PTH oil layer in GLB of Songliao basin, and 1-2 m thin reservoir could be predicted. This method has some significances for reference to prediction of the thin reservoirs with similar geological conditions in China.

    Seismic Technique of Reservoir Prediction and Its Application in Bohai Offshore Area
    LAI Wei-Cheng,Song Zhang-Qiang,Zhou Xin-Fu,Li Jian-Ping,Teng Yu-Bo, Shen Zhan-Ho
    2009, 23(5):  933-939. 
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    It is necessary and important to use seismic data to predict reservoir in oil and gas exploration, especially for offshore exploration characterized by high investment, high risk and small number of drilled wells. The core of geology-seismic  technique of reservoir prediction is close combination of geology and seismic technology,which has experienced two steps from step of frame, description and analogy to that of precision, genesis and dynamics, corresponding to the exploration from structural hydrocarbon reservoir to subtle hydrocarbon reservoir. In the second step, emphasis must be basically paid on the acoustic impedance difference of mudstone and sandstone in different facies, and the further forward modeling to ascertain geological significance of various seismic attributes. Emphasis must also be paid on relationships among seismic characteristics of different stratigraphy tracts, A/S ratio and different types of modern deltas. Therefore, sand body characteristics can be accurately described through section and plane characteristics of seismic profiles with clue to find subtle trap. The application of stratigraphy to seismic sedimentology embodies the two steps of geology-seismic technique, which contributes a lot to fast increasing of reserve of Bohai in recent years, and also improves the study of sedimentology and reservoir.

    Seismic Reflection Configuration Characteristics and Reservoir Prediction in Rub Al’Khali Basin of Middle East Area
    YUAN Jing-Ju, WAN Xiao-Xun, Chen-Meng
    2009, 23(5):  940-946. 
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    According to the different seismic reflection configuration characteristics of delta and fluvial reservoirs, seismic data interpretation, and sedimentary and sequence stratigraphic technique are used to analyse and recognize good reservoirs synthetically.In the east part of Rub Al’Khali basin of Middle East area, there exist some typical seismic reflection characteristics of braided channel and delta front sandstone.Based on these characteristics two sandbody reservoirs are recognized in TS3 basic level cycle of Silurian strata in T structure trap area in the west part of Rub Al’Khali basin, which are predicted as braided channel and delta front sandstone respectively.Reservoir, hydrocarbon accumulation and trap conditions show that the Silurian trap of T structure is a potential exploration region.The proposed well location on T structure is accepted and the later drilling result has verified the predicted reservoir sandstones.

    Application of Spectrum Analysis and Reconstructive Logs Technique in the Reservoir Prediction in Kalashayi Formation of Tahe Oilfield,Tarim Basin
    ZHANG Hong-Zhen, Meng-En
    2009, 23(5):  947-951. 
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    Normal logs cannot solve special geological problems for the influence of different geological factors.In view of reservoir quality in block 3 of Kalashayi Formation of Tahe oilfield, normal logs is transferred to spectrum analysis curves using spectrum analysis technique, and stratigraphic correlations are made using spectrum analysis curves to ensure the accuracy of  correlations.Log constrained inversion is employed in predicting sand reservoirs  in Kalashayi Formation based on the results of stratigraphic correlations and reconstructive logs,the application result shows it is of great value to reservoir prediction.

    Analysis on logging attributes of Upper Palaeozoic Sandstone Reservoirs in Yanchang Gas Field, East of Northern Shaanxi
    HAN Pin-Long, Zhang Xiao-Li, Zhang-Li-Xin, Guo Lan,Sun Pei, Shen Yi-Bo
    2009, 23(5):  952-956. 
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    On the basis of core analysis,well logging interpretation and well test analysis, the characteristics of logging attributes of Upper Palaeozoic sandstone reservoirs are analyzed in Yanchang gas field,east of northern Shaanxi. There have two kinds of reservoirs: quartz sandstone and lithic sandstone. The reservoirs have different well logging attributes, different relations among their physical parameters and well logging interpretation models. The results show that the differential amplitude of overlap by acoustic curve and spontaneous potential curve and the differential amplitude of overlap by resistivity curves with different prospecting range can reveal the reservoir physical properties and their variation. Furthermore, the gasbearing characteristics of reservoirs and their logging attributes are analyzed.

    Application of Integrated Geological Modeling to the  Characterization of Neocene Reef Reservoir
    HU Guang-Yi,GU Li,SUN Li-Chun,ZHOU Jin,LI Jing-Gong,LUO Wen-Sheng,NI Jun-E
    2009, 23(5):  957-962. 
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    Taking LH Oilfield as an example, a method of integrated geological modeling, using seismic, log and geological data, was applied to the characterization of Neocene reef reservoir.The reservoir of LH Oilfield belongs to Neocene Zhujiang Formation, a typical Neocene fringing reef on the carbonate platform margin.In order to predict the complicated inner stratum frame, a workflow was put foreward.Based on incorporated analysis of 3D seismic data, cores and logs, the depositional and diagenetic process was figured out, and thus the inner frame of reef was worked out.Under the constraint of geological frame, logs and seismic attribution, a geological reservoir model was built up with stochastic modeling method.The prediction of reservoir characteristics in reef flat area,based on the study and geological model, has been proved by a new well.

    The Base Level Cycle Subdivision and Correlation of Fluvial Facies in the Phase of Reservoir Development
    LONG Guo-Qing, HAN Da-Kuang, TIAN Chang-Bing, LIU Zhuo, WANG Shou-Ze,DUAN
    2009, 23(5):  963-967. 
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     As one of the most foundational and important matters in the study of oil-gas reservoir development engineering, the high resolution sequence stratigrapy analysis is a key technique, and the division and correlation of fluvial stratum is one of the most difficult problems for the disturbing of autocyclicity. In this paper, the authors analyze the relationship between the composition elements of fluvial stratum and the processions of the cycle. Four identifying patterns of the base level cycle in fluvial facies are generalized, including the channel shape and overlying pattern, facies sequence and association, the feature of autocyclicity, the feature of fluvial plain. It has been suggested that the correlation of short-term cycle must be based on the tendency of the longterm cycle.  The authors also analyze the relationships among the overlying pattern, the retention grade of the sandbodies and the A/S in the processions of the cycle.

    Several Experiences that Can be Referenced in Indonesia Oil and Gas Development of CNPC
    ZHANG Ming, GENG Jun, JIA Chao-Hui, XIE Xiu-Feng, FAN Xiao-Feng
    2009, 23(5):  968-974. 
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    The main reason of the production increasing of gas and oil in Indonesia fields belonging to CNPC is that quite reasonable development strategy and technologies are adapted by Jabung Ltd.PetroChina and Research Institute of Petroleum Exploration and Development.Reservoir prediction technology based on seismic data and condensate-gas development strategy  are applied in condensate fields with quite complicated geology, and multidiscipline reservoir characterization methods are used to give detailed proposed well location in order to increase the success rate of drilling well and to fulfill highly effective development.For overlapped reservoir, detailed reservoir management technology, cycle injected gas in advance, and double-tubing string completion in separated layer development and horizontal wells in thin oil rim are used to improve old fields.For oil fields with low permeability and quite long production history, artificial lift and flooding methods are best choices.For newly founded oil and gas fields, everything is for highly development.Powerful technologies in different aspects are applied to ensure economically development, which can be referenced by others.

    Smart Well Designing Based on the Superposed Graph to Decrease the Petroleum Exploration and Exploitation Risk
    YIN Tai-Ju, ZHANG Chang-Min, GONG Fu-Hua, CHEN Cheng
    2009, 23(5):  975-980. 
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    Taking usage of superposed graph can increase the petroleum exploration and exploitation effect and decrease the risk. In the petroleum exploration, through the detailed facies analysis, microfacies distribution of each layer can be mapped. When the framework reservoir sandstones are determined, superposed map of the them can be drawn and the location of good reservoir can be analyzed to drill exploration wells. While in the petroleum exploitation, through the detailed microfacies analyzing  to determine the distribution of genetic sandstone, and combining with the development data, genetic sandbodies which are not well controled by production and water injection wells can be recognized. Superposing these genetic sandbodies may tell us the location for drilling smart wells which may produce more oil and less water.

    Application of High Resolution Sequence Stratigraphy to Oilfield Fine Development of Damintun Depression of Liaohe Oilfield
    SUN Hai-Lei, LIU Cheng-Zhi, LI Meng-Hui, LIU Hua-Ye, LI Jun-Hui, BI Dian-Hui
    2009, 23(5):  981-986. 
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    As a complicated fault-block reservoir, Shen 84-An 12 block in Damintun Depression of Liaohe Oilfield, has been at the late stage of development with high water content.Based on the drilling and logging data, and with the basic principles of high resolution sequence stratigraphy, the authors identified and compared base level cycles for Es33 semi-member of Shen 84-An12 block.It was analyzed that the base level cycles could control the sedimentary characteristics, reservoir properties and the distribution of residual oil.Then it was made sure that  residual oil had different enrichment features at different parts of the base level cycles, and they were: (1) late stage of base-level-dropping and early stage of base-level-rising, sand body has wide area, large thickness and good reservoir properties, and widely distributing residual oil is easy to develope; (2) early stage of base-level-dropping and late stage of base-level-rising,sand body has small area, little thickness, poor reservoir properties, and scattered residual oil is difficult to develope; (3) middle stage of base-level-dropping or rising, residual oil reserves is medium.So, the applications of highresolution sequence stratigraphy, are very useful in development of residual oil in the high water content stage.

    Preliminary Study of the Lithologic Identification Methods of the Inside of Sand-Gravel Rock Body Reservoirs: An Example from Sand-GravelRock Body of Yan 22 Block in Yanjia Oilfield of Dongying Sag
    YANG Yong, Niu Shuan-Wen, Meng En, Zhang Hong-Zhen
    2009, 23(5):  987-992. 
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    Sand-gravel rock body in Yanjia oilfield of Dongying sag is a kind of nearshore sub-sea apron deposit with characteristics of close source, quick accumulation, heavy thickness and rapid lateral variation. The technology for correct division and comparison of the strata was inadequate and immature in the past, the subdivision and comparison of the inside of the thick sand-gravel rock body is a difficulty for oil geologic research of such reservoirs. According to sedimentary characteristics of sand-gravel rock body of Yan 22 block in Yanjia oilfield, firstly, sand-gravel rock intervals and mudstone intervals are subdivided by logs reconstruction method, which can get rid of the sharp nonreservoirs. Secondly, lithologic constituent of sand-gravel rock intervals is identified by cluster analysis method. Compared with core and FMI, the match rate of the results of reconstructive logs and cluster analysis is 96.6% and 96.2% respectively, which provides a geologic foundation for the subdivision and comparison of such reservoirs.