OIL&GAS GEOLOGY-2006, Volume 27 Issue 5

A study on the distribution of saline-deposit in southern China

Jin Zhijun, Long Shengxiang, Zhou Yan, Wo Yujin, Xiao Kaihua, Yang Zhiqiang, Yin Jinyin

2006, 27(5): 571-583,593. doi:10.11743/ogg20060501

Asbtract ( 1038 )

PDF (12019KB) ( 584 )

References | Related Articles | Metrics

Although accounting for a small proportion of the cap rocks all over the world,the saline deposit is of vital importance for accumulation and preservation of hydrocarbons,for it serves as seal to most of the discovered hydrocarbon reserves and is also the major cap rock in many huge and giant oil and gas fields.The close relationship between the Middle-Lower Triassic saline deposit cap rock and the distribution of natural gas in Sichuan basin suggests that distribution of saline deposit is crucial to the understanding and evaluation of the gas preserve conditions in southern China.Saline deposit forms mostly during the middle and late stages of basin development.In southern China,saline deposit cap rock are mainly developed in Middle-Lower Cambrian,Car-boniferous,Middle-Lower Triassic,and Cretaceous-Paleogene,but they are unevenly distributed and have different sealing importance.Under the influence of deposition,tectonic settings,and late destruction,the saline-deposit rock of Middle-Lower Cambrian mainly distribute in the eastern and southern parts of Sichuan basin and the northwestern part of Guizhou province;the Carboniferous saline deposit mainly distributed in the central of Hunan province,and the Cretaceous-Paleogene saline deposit mainly occurs in Jianghan basin.The Middle-Lower Triassic Saline-deposit,with the widest distribution and the biggest thickness,plays an important role in the sealing of natural gas in Sichuan basin,northern Guizhou Province,Chuxiong basin,and parts of the Middle-Lower Yangtze.

Hydrogeological and hydrogeochemical characteristics and hydrocarbon preservation conditions in marine strata in southern China

Lou Zhanghua, Zhu Rong

2006, 27(5): 584-593. doi:10.11743/ogg20060502

Asbtract ( 1306 )

PDF (9362KB) ( 635 )

References | Related Articles | Metrics

The hydrogeological and hydrogeochemical characteristics of ground water are closely related to hydrocarbon migration,accumulation,and preservation conditions.Ground water can be vertically divided into three zones:free exchanging zone,exchanging-retarded zone,and exchanging-stagnant zone.The exchanging-retarded zone is favorable to petroleum preservation because it is not influenced by surface water,while the free exchanging zone,strongly affected by long-time erosion and oxidation of surface water,offers a poor environment for petroleum preservation.Reconstructed by several tectonic activities,the preservation conditions for oil and gas reservoirs of marine strata in southern China is severely disturbed.Through analysis of the hydrogeological and hydrogeochemical characteristics and their relation with hydrocarbon preservation conditions in several exploration areas of southern China,the concept of preserved meteoric water is put forward and the formation of preserved meteoric water and its geochemical characteristics are discussed.The preserved meteoric water occurring near unconformities can be used as an indicator of poor preservation conditions.Based on the concept,a relatively systematic hydrogeochemical index system for distinguishing hydrocarbon preservation conditions is established for the marine strata in southern China.

A discussion on the relationship between tectonization and hydrocarbon accumulation and dissipation in the platform-basin transitional area of Tarim basin

Pang Xiongqi, Gao Jianbo, Meng Qingyang

2006, 27(5): 594-603. doi:10.11743/ogg20060503

Asbtract ( 827 )

PDF (10191KB) ( 494 )

References | Related Articles | Metrics

The effect of tectonization in different periods on the accumulation and dissipation of hydrocarbons in different reservoirs varies in different accumulation periods.The accumulation mechanism and distribution pattern of hydrocarbons also vary in different reservoirs in different accumulation periods.For the early primary Ordovician reservoirs formed in the second accumulation period,hydrocarbons were prone to accumulate in superimposed area of relatively weak tectonization with an average erosion rate of 2.5-3.5m/50Ma due to alternate differential subsidence and great erosion rate.For the late primary Carboniferous reservoirs formed in the third accumulation period,hydrocarbons were prone to accumulate in low uplift and slope zones with an average erosion rate of 1.0-2.5m/50Ma,rather than in structural high,due to multiple tectonization and erosion resulted from the successive paleohigh in the basin For the late primary Carboniferous reservoirs formed in the fourth accumulation period,some hydrocarbons accumulated in the structural high because of the existence of favorable migration pathways,such as the Donghe sandstone and unconformities,and some accumulated in the peripheral area of the depression without long migration because of late expulsion and lack of favorable migration pathways.

Paleozoic Carrier system in platform-basin transitional area of Tarim basin and future exploration

Zhang Dajing, Wang Yingming, Xiao Zhigao, Wu Maobing, Zheng Menglin, Zhang Weibiao

2006, 27(5): 604-613. doi:10.11743/ogg20060504

Asbtract ( 815 )

PDF (9589KB) ( 519 )

References | Related Articles | Metrics

The Paleozoic is the main exploration target in Tarim basin.An analyze on the distribtuion of the hydrocarbon carrier beds,unconformity surfaces,and conductive faults in the Paleozoic,shows that a good carrier system is formed in the platform-basin transitional area by the Ordovician carbonate carrier bed,Devonian sandstone bed,and the Caledonian and Hercynian unconformity surfaces and faults.The units of hydrocarbon migration and accumulation are also recognized on top of the Middle-Lower Ordovician for the main reservoiring period in the late Hercynian.Based on the spatial arrangement of the migration and accumulation units,the carrier system and the thermal evolution of effective source rocks,a comprehensive evaluation is carried out on the migration and accumulation efficiency of the units.It is further proposed that the Shaxi-Akekule swell,Taozhong I fault zone,and area surrounding well Taozhong-10 and Tazhong-1,be the future exploration targets in the platform-basin transitional area,and three areas,namely the two plunges of the central uplift,the Manxi area,and the northern Awati depression,be worth of much attention during the exploration.

A study on petrophysical parameters for hydrocarbon detection of Jurassic reservoirs in Junggar basin

Ma Lijuan, Zheng Herong

2006, 27(5): 614-619. doi:10.11743/ogg20060505

Asbtract ( 770 )

PDF (5799KB) ( 651 )

References | Related Articles | Metrics

Based on core test data obtained from simulation of formation pressure and temperature,and in combination with multi-wave logging data,the petrophysical parameters for seismic prediction of Jurassic reservoir and hydrocarbon detection in the central of Junggar basin are studied.It is believed that there are some limitations for prediction of lithology with seismic attribute alone,and hydrocarbon detection is infeasible with traditional seismic attributes.Difficulties for reservoir prediction and hydrocarbon detection with traditional compressional wave impedance technology are discussed.It is suggested that a combination of AVO and elastic wave inversion method be used to effectively improve reservoir prediction and hydrocarbon detection.The results of the study are of practical significance for seismic in prediction of reservoir and hydrocarbon diction in the central of Junggar basin.

Research on pattern of reservoiring dynamics in sand lens reservoirs in Dongying sag

Zhuo Qingong, Jiang Youlu, Sui Fenggui

2006, 27(5): 620-629. doi:10.11743/ogg20060506

Asbtract ( 858 )

PDF (10503KB) ( 510 )

References | Related Articles | Metrics

Based on research of the palaeogeothermal,palaeopressure,and palaeostress during large scale hydrocarbon accumulation in Dongying sag,the dynamic hydrocarbon accumulation in sand lens reservoirs is analyzed by applying the theory of reservoiring dynamics.The results show that resevoring dynamics run through the whole process of hydrocarbon accumulation and the overpressure of fluids in source rocks is the primitive drive for hydrocarbon migration and accumulation.According to the research,the main factors that control hydrocarbon accumulation are source rock,carrier system and reservoiring dynamics,and the pattern of reservoiring dynamics is dual control of stress and pressure,duplex conduction,and episodic replacement.

Range of hydrocarbon expulsion from the Tertiary source rocks and hydrocarbon migration boundary in Subei basin

Chen Anding

2006, 27(5): 630-636. doi:10.11743/ogg20060507

Asbtract ( 862 )

PDF (6164KB) ( 705 )

References | Related Articles | Metrics

Based on the analysis of index correlativity,the lower limit of hydrocarbon expulsion indexes(R_o≥0.6%,SM≥0.10,C₂₉Mor/C₂₉Hop≤0.45,and CPI≤1.3)are selected through the study of shows at various levels.The indexes are used as the threshold values of hydrocarbon expulsion from source rocks in the Paleogene and Taizhou Formation in Subei basin to define the expulsion range of each set of source rocks.In Jinhu sag, the source rocks capable of expulsion in the fourth Member of Funing Formation are mainly distributed inSanhe, Longgang,and Chaxi sub-sags;and that in the second Member pf Funing Formation are also mainly located in the above-mentioned three sub-sags and their inner slopes.While in Gaoyou sag,source rocks capable of expulsion in the fourth Member of Funing Formation are mainly limited within the deep o fGaoyou sag,Liulushe subsag,and the inner slope,and that in the second Member of Funing Formation are extensively distributed in all areas but the Zheduo swell.Methods such as fluorescence thin section,hydrocarbon inclusion analysis,and oilsource correlation and tracing are employed to explore the oil and gas migration boundary in the basin.According to the research,hydrocarbons from Gaoyou and Linze sags have accumulated in Zheduo swell after a long distance migration.The analysis shows that the oil in Taizhou Formation in Well XC 1 might come from the Linze sag.The phenomenon that hydrocarbons generated by the upper source rocks accumulate in the lower reservoirs is largely the result of consequent normal fault adjustment; while the oil in the first Member of Funing Formation in Well XC1 might come from the mature source rocks in the Taizhou Formation in eastern Gaoyou sag after a long distance migration(about 20 km)resulted from antithetic normal fault adjustment(hydrocarbons generated from the lower source rocks accumualate in the upper reservoirs).

Discovery and timing of major thrustbelt in Jiamusi-Yitong fault zone

Sun Xiaomeng, Long Shengxiang, Zhang Meisheng, Liu Xiaoyan, Hao Fujiang

2006, 27(5): 637-643. doi:10.11743/ogg20060508

Asbtract ( 758 )

PDF (6520KB) ( 825 )

References | Related Articles | Metrics

The newly discovered major thrustbelt in the Jiamusi-Yitong fault zone in Siping city of Jilin province has well developed thrusts,cataclasite,and folds.In areas near the eastern and western main boundary faults, secondary faults are distributed intensively,and folds are dominated by closed vertical bends,while in the central part of the thrustbelt,the strata occurrence is gentle with few faults and folds,indicating that the main boundary faults are the area of compressive stress concentration.Most of the faults thrust towards the 110°-130° irection.According to the relationship of cutting and overlaying between the thrusts and the Mesozoic-Cenozoic strata,the Jiamusi-Yitong fault zone is considered to have experienced at least two periods of strong obduction since the Cretaceous:the first occurred in late Late Cretaceous,when the major thrustbelt was formed;and the second occurred at the end of Oligocene.According to field survey results and basin data,the formation and evolution of Jiamusi-Yitong fault zone can be divided into five stages:namely sinistral strike-slip(early K₁),regional stretch(later K₁-early K₂),compressive and thrusting(late K₂),fault depression(E),and compressive inversion(the end of E₃).

Sealing ability of lithology and high pressure fluid in carboniferous gas pools in eastern Sichuan

Xu Guosheng, Li Jianlin, Peng Dajun, Li Zhongdong

2006, 27(5): 644-651,659. doi:10.11743/ogg20060509

Asbtract ( 794 )

PDF (7835KB) ( 482 )

References | Related Articles | Metrics

Eastern Sichuan region,the relatively active belt between the stable massifs in Sichuan basin,harbors ten rows of high and steep structural zones where a great breakthrough has been made in the exploration of Carboniferous gas pools since the 1990s.The Liangshang Formation mudstone is the direct cap rock of the Carboniferous gas pools.Judging from the permeability and median pore throat radius,its sealing ability is poor,while in terms of porosity and breakthrough pressure,its sealing ability is relatively good.This single sealing ability,however,is insufficient to hold the abundant Carboniferous gas pools with high gas saturation in the study area according to the mechanism of pressure sealing,the premise for an overlying layer to seal gas accumulation in an underlying layer is the original pressure and pressure coefficient of the former is higher than that of the later.The overlying Permian Yangxin Series with abnormal high porefluid pressure serve as a high quality seal for the underlying Carboniferous gas pools.The reverse faults that extend to the surface in some high and steep structural zones can cause pressure release and hydrocarbon emission.The research results and exploration data show that the pressure coefficient of 1.30 for Permian Yangxin Series can be used as the critical value of pressure seal.When the pressure coefficient surpasses the value,the Carboniferous gas pools would be safely sealed.

Characteristics of heterogeneous 3-D model of sandstone reservoirs in different development stages

Yang Shaochun, Wang Ruili

2006, 27(5): 652-659. doi:10.11743/ogg20060510

Asbtract ( 1077 )

PDF (7374KB) ( 534 )

References | Related Articles | Metrics

The calculation of heterogeneous aggregative index,together with its function and significance,is briefed based on the data acquired from the Block Ⅱof Shengtuo oilfield.The 3-D modeling of heterogeneous aggregative index by employing the reservoir stochastic method includes the following five stages:preparation of reservoir data,construction of model,analysis of heterogeneous aggregative index,construction of heterogeneous model,and display of modeling results.The spatial heterogeneity of reservoir is vividly characterized by the model.An analyze of the variation function and 3-D model characteristics of heterogeneous aggregative index of sandstone in the Third Member of Dongying Formation in its earlier,middle,and later stages of development reveals the changing pattern of reservoir heterogeneity at different development phases.According to the results, the range of influence(a)decreases with waterflooding,while the sill value(c_o+c)increases and nugget value(c_o)remains zero.The initial,middle and late development stages are characterized by moderate,moderate to relatively strong,and strong reservoir heterogeneities,respectively.Vertically,the heterogeneous aggregative index varies greatly in the upper part of the reservoir and is more constant in the lower part.Vertical interformational and intra-formational heterogeneities are stronger than lateral heterogeneity.Water injection intensifies the heterogeneity of reservoirs.

Technology of effectively enhancing recovery efficiency in thin-interbedding reservoirs of low-permeability sandstone

Wang Wenhuan

2006, 27(5): 660-667,674. doi:10.11743/ogg20060511

Asbtract ( 1579 )

PDF (7964KB) ( 484 )

References | Related Articles | Metrics

Taking an interbedded thin sandstone reservoir with low permeability in Chun-41 block in the fourth member of the Shabejie Formation as an example,the factors that affect the development of low-permeability oilfields are analyzed based on their percolation mechanism.Inappropriate well spacing,poor matching of well pattern with fractures,improper timing of waterflooding,and low awareness of reservoir protection,are all considered to be factors contributing to the poor performance of low permeability oilfields.Based on study of percolation mechanism and distribution of earth stress field,several corresponding measures have been proposed to deal with the problem.And the results of field implementation of the measures shows that the daily oil production,oil recovery rate,and daily injection rate of the field are evidently increased and the water cut and injection pressure are lowered.The recovery efficiency is also estimated to be raised by 5.23 %,showing that the measures can effectively improve the performance of low permeability reservoirs.

The microscopic features of pore structure in Gaotaizi oil layer of Daqingzijing area

Zhang Dawei, Chen Fajing, Cheng Gang

2006, 27(5): 668-674. doi:10.11743/ogg20060512

Asbtract ( 1391 )

PDF (6064KB) ( 559 )

References | Related Articles | Metrics

Rock pore structure is a main factor affecting oil and gas recovery and fluid(oil,gas and water)storage capacity of reservoirs.Therefore,understanding the features of pore structure is crucial for improving productivity and recovery factor.The pore structure in Gaotaizi oil layer of low permeability in the Lower Cretaceous Qingshankou Formation in Daqingzijing area are studied comprehensively by utilizing several analytical methods such as core,cast thin section and petrographic images,especially laser scanning confocal microscopic 3-D image. Three topics concerning the issue are discussed here:(1)relationship between porosity and permeability;(2)influence of pore structure upon porosity and permeability;and(3)factors affecting the capacity of a reservoir.

Interfering factors in oil and gas geochemical exploration

Deng Guorong

2006, 27(5): 675-681. doi:10.11743/ogg20060513

Asbtract ( 746 )

PDF (7083KB) ( 482 )

References | Related Articles | Metrics

Using the understanding of interference in geophysical exploration for reference,the concept of interference in oil & gas geochemical exploration is proposed and also expounded with the theory of vertical micromigration of hydrocarbon and the working principle of geochemical exploration.There are four basic types of interference sources in oil and gas geochemical exploration: syngenetic process,biochemical gas effect,sample quality difference,and pollution from human activities.The first three types are the main interfering factors; while the last one maybe limited to some individual sampling spots.An analysis is carried out to evaluate the degree of interference based on the study of field exploration cases and results of simulation test.Corresponding measures are proposed to suppress interference in different stages of geochemical exploration,including selection of proper method combination,standardization of the media difference,and accurate anomaly separation and identification.The relationship between anomaly and background shows that the interference is universal in terms of background can occur in any survey areas,while the real interference in terms of anomaly just exists in limited survey areas,and can be suppressed to some extent with proper methods.

Characteristics of surface hydrocarbon anomalies in Shiwu faulted depression in southern Songliao basin and their significance as an oil/gas indicator

Xia Xianghua, Hu Kai, Qin Jianzhong

2006, 27(5): 682-688. doi:10.11743/ogg20060514

Asbtract ( 685 )

PDF (5804KB) ( 423 )

References | Related Articles | Metrics

For more than 70 years,surface geochemical exploration technology has been applied in the prediction of deep oil and gas reservoirs through observing anomalous surface expression of hydrocarbon microseepage.It is generally accepted that hydrocarbon may leak from reservoirs through microseepage,but the complex relationship between surface geochemical anomaly and deep hydrocarbon accumulation has not yet been proven.Hydrocarbon microseepage detection in the known oil and gas accumulation in Shiwu faulted depression shows that all of the geochemical indicators in this area are characterized’by heterogeneous geochemical field with low background value,and the concentration of hydrocarbons in the anomalous area is relatively high.The anomalies related to oil and gas accumulation are annular or complex annular while the anomalies caused by a fault or cap rock are banded or block-shaped.The microseepage anomaly in a gas field has different features with that in an oil and gas field.The former is low in intensity and simply annular in shape,while the latter is complicated annular in shape,with some anomalous indicators occurring within the ring.

Petroleum geological significance of physical absorption of hydrocarbon in surface soft

Li Guangzhi, Cheng Tongjin, Tang Yuping, Deng Tianlong

2006, 27(5): 689-695. doi:10.11743/ogg20060515

Asbtract ( 880 )

PDF (6490KB) ( 762 )

References | Related Articles | Metrics

During a mass and energy exchange between the light hydrocarbon in reservoirs and its environment, a dynamic equilibrium is formed by the light hydrocarbons of all states under the action of sediment surface.The light hydrocarbon physically absorbed by surface soil mainly comes from the reservoirs below and their composition and content can reflect the nature and features of the associated reservoirs.By tracing the composition and content of absorbed light hydrocarbons,the hydrocarbon source(i.e.reservoir)can be located and its quality and characteristics can be predicted.The technology of physical absorption of light hydrocarbon is to completely release the physically absorbed light hydrocarbons from soil samples in a vacuum state and qualitative and quantificational analyse the composition of released hydrocarbon with a gas-chromatogram,so as to predict the quality and characteristics of the reservoir through an observation of the concentration change.The application of the technology in the pilots in Xinchang gas field of Sichuan basin,in Zhenyuan-Jinchuan loess tableland of Ordos basin,and in Chaiwopu Gobi of Tarim basin both with complex surface and geologic conditions gains positive resuits and implies a bright future for its further application and development.

Comparative study of biomarkers and carbon isotopes of coal-measure source rock in Jiyang depression

Li Zheng, Li Juyuan, Xu Xingyou, Lin Wu, Wang Ru

2006, 27(5): 696-701. doi:10.11743/ogg20060516

Asbtract ( 1256 )

PDF (5421KB) ( 815 )

References | Related Articles | Metrics

A detaile comparative study is performed on the biomarkers and the carbon isotopes of two sets of coal-measure source rocks in Permo-Carboniferous and Mesozoic in Jiyang depression based on a systemic analysis of large amount of source rock data.Compared with the Mesozoic Fangzi Formation the coal measures source rock in Permo-Carboniferous is larger in stable carbon isotope of kerogen and group composition,higher in contents of gammacerane and C₂₇sterane,and lower in ratio of Pr/Ph,indicating a better environment for hydrocarbon generation,composition of parent materials,and preservation condition.

Petroleum geological characteristics of deep water deposits in Upper Permian-Lower Triassic trough in Sichuan basin and adjacent areas

Wang Yigang, Wen Yingchu, Hong Haitao, Xia Maolong, Zhan Jing, Song Shuyun, Liu Huayi

2006, 27(5): 702-714. doi:10.11743/ogg20060517

Asbtract ( 907 )

PDF (11648KB) ( 530 )

References | Related Articles | Metrics

Three troughs,namely Guangyuan-Wangcang,Chengkou-Exi,and Kaijiang-Liangping,in Sichuan basin and its adjacent areas,is filled with deep water carbonates of the Upper Permian-Lower Triassic of Feixianguan Formation.The Dalong Formation in the upper part of the Upper Permian in the area is a condensed succession of 12.5-29m in thickness deposited in the troughs in the chasmic stage.It is composed of silicalite, siliceous mudstone,and siliceous limestone,with fossils such as radiolarans and foram.While the lower part of the Triassic Feixianguan Formation is a filled succession of 50-300m in thickness deposited in the troughs in post-chasmic stage.It is deep water carbonates consisting of a pelagic melanic mudstone and microcrystalline calclithite,as well as turbidites and breccia limestone from gravity flow.The Dalong Formation was deposited at the end of the late Permian when the maximum flooding surface occurred in the trough area.And the deep water carbonates of Feixianguang Formation were deposited during slow regression.The Upper Permian-Lower Triassic Feixianguan Formation constitutes a complete third-order sequence.The deep water carbonates are source rocks of excellent quality with TOC up to 6.21%.But no organic reefs were developed in the Upper Permian and the Feixianguan Formation is lack of oolite.

Table of Content