Table of Content

20 April 2009, Volume 23 Issue 2

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Engineering Geology and Environmental Geology

Tectonic Control on the Formation of High-deposition-rate Sediment Drift in the Northern Slope of the South China Sea

LUAN Ti-Wu BANG Hua-Chao QIU Yan

2009, 23(2):  183-199. 

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The northern slope of the South China Sea is one of the most active areas in the world oceans with modern sedimentary process. A high-deposition-rate sediment drift was found on the down slope of Dongsha islands. The material sources of this sediment drift were examined and discussed by several other papers, but not yet solved. Based on the multi-channel seismic data and the long term bottom current observation data, this paper finds a new source for this sediment drift. The seismic profiles show that a Miocene drape formation which was started from the end of Oligocene and ended to the Early Pliocene was very well and originally developed as a horizontal layer in the study area. Since about 3 Ma, the Miocene drape formation was uplifted and eroded along Dongsha area. The amount of the eroded materials from the Miocene drape formation could be as much as that from Pearl River and Hanjiang River to the northern South China Sea, and that from the rivers of southwest Taiwan to north South China Sea. The calculated result shows that a sediment rate of only 12 cm/ka could be reached if all the materials from Pearl River and Hanjiang River deposited on the northern slope of the South China Sea. So, it seems impossible that the sediments on the high-deposition-rate sediment drift are mainly from Pearl River and Hanjiang River. Considering the special oceanic current regime of the northern South China Sea and its adjacent areas, most part of the sediments from rivers of southwestern Taiwan was trapped in the area around Taiwan, and only small part could move far to and deposit on the high-deposition-rate sediment drift. Bottom current observation data show that the hydrodynamic environment of the northern South China Sea Shelf is powerful enough to erode the uplifted Miocene drape formation at the sea floor and transfers the eroded materials along the northern shelf of the South China Sea southward to the slope area, and these materials become the main source of the high-deposition-rate sediment drift.

The Significance of Protection of the Caofeidian Shoal Tidal Channel and  Comparison of the New Caofeidian Plan of Sea Reclamation Land to the Old One

YIN Yan-hong

2009, 23(2):  200-209. 

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       The Caofeidian plan of sea reclamation land is the top one project of sea reclamation land in China. The plan area of sea reclamation land is 310 km² and an industrial area will be set up there. Caofeidian sea area has a good condition of water depth with two harbor potential areas, and it is reasonable to set up an industrial area which needs the good capacity of port transportation. The main shortcomings of the old plan of sea reclamation land are: The area of the sea reclamation land is too large to get a good benefit; Large earthworks are difficult to get; Especially the Caofeidian shoal tidal channel was blocked. The Caofeidian shoal tidal channel is an important tidal channel in the shoal area, and it has a key role to maintain the Laolonggou harbor potential area and sea environments, and it should be kept. The suggestions from marine experts promoted the modification of the Caofeidian plan of sea reclamation land. Recently a new Caofeidian plan of sea reclamation land has unveiled, and some main modifications are: The Caofeidian shoal tidal channel will be reopened; the NEE shoal tidal system will be restored; a large port will be set up in Laolonggou area and the Laolonggou harbor potential areas can be protected and utilized; earthwork balance is improved; coastline is increased; and sea environment influences are reduced. Of course, further modifications of the new plan are needed. Tianjin-Tanggu-Caofeidian area is one of the two main ground subsidence areas in China. Preparation should be done to relieve the troubles which result from ground subsidence, ocean calamity and earthquakes. The area of the sea reclamation land should be controlled. The principles of less reclamation land from sea and more inspection of the sea environment should be followed. Sea reclamation land should be carried out step by step under the endurable situation of the sea environmental capacity.

Gas Hydrate Reservoir Characteristics of Shenhu Area, North Slope of the South China Sea

GONG Yue-hua YANG Sheng-xiong WANG Hong-bin LIANG Jin-qiang GUO Yi-qun WU Shi-gu

2009, 23(2):  210-216. 

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       As a  type of  new  energy resource, gas hydrate  is drawing more and more attention for   its cleanness and potential huge energy reserves, whilst the research on hydrate has been developed. However, scientists pay less attention on gas hydrate formation mechanism because relative data are poor. The gas hydrate formation mechanism of Shenhu area, which had been surveyed for nearly four years by Guangzhou Marine Geological Survey, is discussed in this paper in the aspects of substance source, gas transporting conduit, conditions for formation etc. The results suggest that the huge source rocks formed in Paleocene period in Baiyun sag are the main substance source, and diapirs are the main conduit for fluid transportation upwards to form hydrates in the end, while the slip bodies developed broadly in Late Tertiary are the main spaces for gas hydrate accumulation. Finally, The conclusion is  drawn that Shenhu area is  a  better hydrate  prospecting area because of its  favorable conditions for gas hydrate  formation.

Relationship between the Sonic Logging Velocity and Saturation of Gas Hydrate in Shenhu Area, Northern Slope of South China Sea

LIANG Jin WANG Ming-jun WANG Hong-bin LU Jing-an LIANG Jin-qiang

2009, 23(2):  217-223. 

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The distributing features and change of sonic logging velocity and gas hydrate saturation in gas hydrate-bearing sediments were summarized with seismic and well logging data, furthermore, a comparative study was conducted between the theoretical calculation and in-situ measurement of gas hydrate saturation in site A, Shenhu area, northern slope of South China Sea. The relationship between sonic velocity and gas hydrate saturation in gas hydrate stability zone has been analyzed, too. The analysis results show that:(1)the thickness, sonic velocity, and gas hydrate saturation of gas hydrate-bearing zone are about 20 m, 1,873－2,226 m/s, 15.0%－47.3%, respectively;(2)the in-situ measurement of gas hydrate saturation which was derived from the field test of the chloride content in pore water is not direct proportion to sonic velocity for the influence of seafloor geological factors, but fluctuates according to sonic velocity with the range of 10%－20%, and generally increases with increasing sonic velocity;(3)the calculated value of gas hydrate aturation from velocity model of heat elasticity theory regularly rises with increasing velocity. The fit relationship between the theoretical calculation and in-situ value of gas hydrate saturation indicates that the established rock physics model is correct, and the selected parameters of model are reasonable. This method can be extended to the total study area to provide valuable data for resource evaluation of gas hydrate.

Study on Silicate Drilling Fluid for Drilling in Marine Gas Hydrate Bearing Sediments

TU Yun-zhong JIANG Guo-sheng ZHANG Hao NING Fu-long ZHANG Ling

2009, 23(2):  224-228. 

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         When drilling in the marine gas hydrate bearing sediment, the encountered problems include gas hydrate dissociation at the bottom of hole and reformation within the pipeline, as well as the instability of wellbore. A properly designed drilling fluid is a solution to these problems. After tremendous experiments, a formulation of silicate drilling fluid with the addition of inorganic salt and kinetic gas hydrate inhibitor was proposed, and its performance has been evaluated. Finally, it is suggested that the silicate drilling fluid can not only meet the requirements of transporting debris and cleaning hole, but also can effectively inhibit the hydration of wellbore formation and the dissociation of gas hydrate bearing sediments, and the reformation of gas hydrate as well, so the drilling fluid can ensure the safety and efficiency of drilling in marine gas hydrate bearing sediments.

Discussion on the Relationship between Carbonate Magnetic Susceptibility and Sequence Stratigraphy in Middle-Upper Ordovician  in Aksu Area,Xinjiang

WU Zhen-jie YAO Jian-xin CHEN Liu-qin LI Yan-jun LIU Ping-hua WANG Ting-ting

2009, 23(2):  229-237. 

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       Based on measurement and statistical data of 185 Middle-Upper Ordovician carbonate samples, miciofacies analysis of carbonate and sequence stratigraphy research, relationship between carbonate magnetic susceptibility and sedimentary setting, sequence boundaries, parasequence (sets) have been discussed. Results show that normally rocks such as calcareous mudstone, nodular limestone, argillaceous limestone, which were formed at deep water level where energy was low, have relatively low value of magnetic susceptibility, while rocks such as oolite-containing calcarenite, oolitic limestone have high value of magnetic susceptibility, which were formed at shallow water where energy was high. Magnetic susceptibility decreases greatly across submerged sequence boundary in carbonate rocks. Magnetic susceptibility of upper units of parasequence (sets) are bigger than those of lower ones, with a shape of high-frequency oscillation.

Subdivision and Geological Age of Pingshui Group in Zhejiang,China

GONG Ri-xiang YAN Tie-zeng YU Xin-qi HUA Xi-hong ZHANG Zhi-fang

2009, 23(2):  238-245. 

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        By studying the Mengshan section in Pujiang County, Zhejiang Province, this paper established two unit-stratotypes: Mengshan Formation and Chentangwu Formation. These two formations can be united into Pingshui Group, which is a former used lithostratigraphic unit and has been revised the meanings in this research. The lower part of Pingshui Group is Mengshan Formation (spilite-keratophyre formation) and the upper is Chentangwu Formation (marine facies sand-mudstone formation).Pingshui Group, representing the oldest basement in northwest Zhejiang, is conformably overlain by Shuangxiwu Group. Through study and argumentation of microflora and isotope age in the stratotype section, authors proposed that the geologic age of Pingshui Group belongs to the Meso-Neoproterozoic.

U-Pb Dating of Detrital Zircons from Late Triassic Wenbinshan Formation in Southwestern Fujian and Its Geological Significance

WANG Guo-sheng HE Fu-bing ZHU Wei-ping MA Wen-pu

2009, 23(2):  246-255. 

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       Increasing data indicate that the SE coastal region of China mainland is not a post-Caledonian platform but a amalgamation of different massives. The Late Triassic Wenbinshan Formation in southwestern Fujian Province is characterized by quasi-mollasse. The U-Pb dating on detrital zircons is employed in this research to a better understanding of the varied provenances and the regional tectonic evolution. The morphological observations of detrital zircons and the U-Pb age dating results reveal four points regarding to the tectonic evolution in southwestern Fujian Province as follows: (1) Late Triassic Wenbinshan Formation has a complicated provenances but mainly derived from northwestern Fujian uplift. (2) Late Triassic sedimentation has an Archaean provenance older than 2.5 Ga which indicates distribution of Archean continent relics on Cathaysia region or another previously unrevealed Archean basement in southeast China. (3) 980-1,190 Ma detrital zircons imply that a Grenville age block served as a provenance area during Late Triassic sedimentation. This block collided with Cathaysia block as a result of the closing of Paleo-Tethys ocean during Late Triassic. (4) The Indosinian magmatic rocks belt in the region formed another part of the provenance during the Late Triassic sedimentation of Wenbinshan Formation.
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Zircon U-Pb Age of Siliceous Rock from the Central Jilin and Its Geological Significance

ZHANG Chun-yan ZHANG Xing-zhou XIA Qing-he

2009, 23(2):  256-261. 

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The siliceous rock zone in Yantong mountain area,central Jilin Province,is the key region for studying the paleoAsian ocean tectonic evolution. The predecessors confirm that piedmontite siliceous rock exists in this area, and combining with the research of peripheral rock characteristics, the paper suggests that this area should be the site of the final closing of the paleo-Asian ocean. According to the lithochemical analysis, the authors find the parent rocks of silicalite are volcanos. In the zircons CL image, the rhythm annulus structure of ziron is obvious,which shows that they are the earlier magma rock zircons. LA-ICP-MS single-zircon U-Pb isotopic age dating indicates the siliceous rock deformation and metamorphism took place at (239±11)Ma.Combining with the metamorphism age of Hulan Group, the authors confirm that the final closing of the paleo-Asian ocean took place in the Mesozoic(Triassic).

Re-Os Isotopic Chronology of Molybdenite from the Taipinggou Porphyry-type Molybdenum Deposit in Inner Mongolia and Its Geological Significance

ZHAI De-gao LIU Jia-jun WANG Jian-ping PENG Run-min WANG Shou-guang CHANG Zhong-

2009, 23(2):  262-268. 

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The Taipinggou porphyrytype molybdenum deposit in Inner Mongolia is located in the north of the well-known Da Hinggan Ling metallogenic belt in China. It lies in the superimposed part of the circum Pacific metallogenic province and the Paleo-Asian Oceanic metallogenic province. Re-Os dating of molybdenite from the Taipinggou porphyry-type deposit gives an isochron age of (130.1±1.3)Ma, and the ore-forming epoch belongs to the Yanshanian mineralization episodes. The Taipinggou molybdenum deposit is formed by the eastern China magmatic activities in late Mesozoic. The metallogenic geodynamics of the deposit is viewed that the lithosphere of east China is under the environment of lithospheric extension and thinning. The Re contents of the Taipinggou molybdenum deposit range from (9.9±0.085)×10^-6  to (69.185±0.616)×10^-6 , which equals to the Re contents of crust-mantle magmatic mixing. It also identifies that the sources of ore-forming materials come from the deep mixing of crust and mantle.

Essential Factors and Model for Prediction of Jingtieshan-type Copper Deposits in the Western Segment of the North Qilian Mountains

YANG He-qun ZHAO Dong-hong WANG Yong-he TAN Wen-juan YU Pu-sheng

2009, 23(2):  269-276. 

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Altered rock type copper deposits of fracture zone connected with banded ferruginous formation of Mesoproterozoic group were found recently in Jingtishan area of North Qilian Mountains, for example,Huashugou and Liugouxia copper deposits. The essential factors were discussed in this paper. It is considered that the cupreous banded iron formation was source bed； pervasive fractures were favorable to mineral activities； the heat source was crustal magma activities； and structural fracture altered zone was ore-contained structure. The formula for quantitative forecast of Jingtieshan-type copper ore is built in this paper.The value of representative to the resource potential of copper,weight of ironstone,growth degree of pervasive fractures and thermal parameter are disscused. According to the aforementioned formula, the copper resource potential of Jingtieshan-type may be 1.473×10⁶ tons in the western segment of North Qilian including up to 1.25×10⁶ tons in the Jingtieshan ore field. The new favorable districts are discovered in our inspection, so the prospecting is necessary to continue in this area.

Geochemical Characteristics and Genesis of the Laowan Gold Deposit in Henan Province

CHEN Liang DAI Li-jun WANG Tie-jun LUO Ping XIA Guo-ti

2009, 23(2):  277-284. 

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          On the basis of detailed investigation of geological setting and ore deposit geologic features, this study analyses quartz-hosted fluid inclusions and oxygen and hydrogen isotope composition of quartz, as well as sulfur and lead isotope composition of sulfides from the Laowan gold deposit in Henan Province. The ore-forming fluid of the Laowan gold deposit is of the CO² -rich ^K+-Na⁺-Cl--SO₂^-4 system with middle-low temperature and low salinity. Oxygen and hydrogen isotope analyses show that  δ¹⁸O and δD values range from -5.25‰ to +5.37‰ and-67‰ to -76‰, respectively, which indicates that the ore-forming fluid of the Laowan gold deposit is derived from magmatic and meteoric water. The δ³⁴S values of sulfides associated with gold mineralization range from -0.1‰ to+5.3‰ with a mean of +3.98‰, indicating typical signature of deep source sulfur. The characteristics of lead isotope indicate that it was mainly derived from the mantle, partly from the crust. Comprehensive research shows that Laowan gold deposit is a mesothermal-epithermal tectonic altered type gold deposit controlled by ductile shear zone.

Geochemistry Constraint on the Ore-forming Materials of the Chengchao Iron Deposit，Hubei Provinc

XIA Jin-long HU Ming-an XU Bo-jun ZHANG Wang-sheng YANG Zhen WANG Lei

2009, 23(2):  285-291. 

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The magmatic activity could be divided to two stages in Chengchao ore district,Hubei：diorite in the early stage and granite in the latter stage．The magma intruded in the mid-late Yanshanian period．The correlation between the magma and mineralization is consanguineous and the Yanshanian magma is the source of ore-forming materials．The mineralization period could also be divided to two stages：magnetite ore in the early stage and metal sulfide ore in the latter stage. Magnetite stage is the main stage for mineralization．The contents of rare earth elements indicate that the chondritenormalized REE and LREE patterns of diorite have the strong reversed change with that of magnetite ore．Such a case also occurs between granite and metal sulfide ore．The moderate-strong depletion of Eu in granite and metal sulfide ore is the result of the crystallization of diorite and the mineralization of magnetite．In addition，the contents of trace elements indicate that in diorite it is rich in Cr，which belongs to chalcophile elements，and this is because of the mineralization of magnetite ore and the separation of Fe ³⁺ in the early period；it is rich in Co,Ni in granite，belonging to siderophile elements，which is related to the mineralization of metal sulfide ore．We could draw the conclusion that the metallogenic elements are mainly derived from diorite magma，which is consistent with the other skarn type iron deposits in southeast Hubei Province．This research may play an important role in summarizing the metallogeny in the area of southeast Hubei Province．  

The Carrying Capability of Western Margin Faults of JZS Oilfield and Their Controls on Hydrocarbon Accumulation in Liaodong Bay

LI Wei-lian LIU Zhen DAI Chun-meng LIU Jun-bang XIA Qing-long ZHOU Xin-huai

2009, 23(2):  292-298. 

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         JZS oilfield, which is located in the middle-northern part of Liaoxi lower uplift, is bounded by  Liaoxi No.1 and Liaoxi No.2 faults in the west. Whether hydrocarbons generated in Liaoxi depression could migrate to Liaoxi lower uplift was directly determined by the carrying capabilities of the two margin faults. So, research on the carrying capabilities of the margin faults is of magnitude significance for understanding hydrocarbon accumulations and making wise decisions for exploration in the region. In this paper, based on the well and 3D seismic data of JZS structure, the history of faulting movement, transversal and vertical sealing abilities during the period of JZS hydrocarbon accumulation of the two margin faults were studied by employing technologies such as tectonic evolution sections, mudstone smearing factors and pressure analysis on fault plane. Research results showed that, during the period of JZS hydrocarbon accumulation which was the final stage of the 1st member of Dongying Formation, Liaoxi No.1 and Liaoxi No.2 faults were active, opened traversely in the 3rd member of Shahejie Formation and vertically above 1,800 m, so they served as a migration conduit system for hydrocarbons generated in Liaoxi depression and migrating to Liaoxi lower uplift. 

The Influence on Natural Gas’s Enrichment from Configuration of Ancient Valleys and Fractures in Jingbian Gasfield, Ordos Basin

XU Bo SUN Wei YAN Ning-ping TANG Tie-zhu

2009, 23(2):  299-304. 

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         It is important to study the natural gas’s enrichment of well Shaan 200 area in Jingbian gasfield, Ordos Basin, which has potential gas reserves. The configuration of ancient valleys and fractures has different influence on natural gas’s enrichment.The natural gas from the Upper Paleozoic migrates into the Lower Paleozoic vertically through the ancient valleys,and into the fifth member of Majiagou Formation laterally through its fractures. The more ancient valleys or/and fractures develop,the more natural gas enrich. The gas saturations of Ma_5(1) and Ma_5(2) formations are greater than that of Ma_5(4-1) with only fractures for their dual-action of ancient valleys and fractures.

Relationship between the Characteristic of Lithology-lithofacies and Distribution of Fractures in Carboniferous Reservoirs, Northwest Margin of Junggar Basin

CHEN Qing ZHANG Li-xin

2009, 23(2):  305-312. 

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        The interactive formation of Carboniferous volcanic rock and sedimentary rock set is widely developed in the northwest margin of Junggar Basin. The profile vertical sequence is made up of several sets of volcanic rocks and sedimentary rocks. This paper takes Carboniferous volcanic rocks and sedimentary rocks of the zones Six, Seven, Nine of Karamay oilfield for examples. We use the actual data of seismic, borehole, drilling core, electrical property, and try to put forward a method of stratigraphic division in Carboniferous formation,northwest margin of Junggar Basin. We first divide the stages of volcanic rock and sedimentary rock, build the distribution mode of the multiple stages of volcanic rock and sedimentary rock lithofacies, quantitatively describe the developed extent of different lithological fractures, and discuss the relationship among lithology, lithofacies, fractures and the forming of reservoir.The Carboniferous fracture developed range of the zones Six, Seven, Nine are determined and this can provide a scientific basis for the successive exploration and development in this area. 

Background for Oil and Gas Accumulation of Es₄ Sub-salt Reservoir in Dongying Sag,Shandong

WANG Ju-feng

2009, 23(2):  313-318. 

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         Dongying Sag is one of the major hydrocarbon bearing sags in Bohaibay Basin. After 40-year exploration and development, the upper part of the fourth section of Shahejie Formation (Es₄) as well as those above the sequence have been highly explored. To ensure the sustainable development of Shengli oilfield, it is very urgent to explore favorable prospects. The article analyzed the background for oil and gas accumulation in Es₄ sub-salt reservoir by the tests of geochemistry targets and organic inclusion homogenization temperature, combined with the study of the reservoir capability controls of sedimentary facies, diagenetic facies and high-pressure sealed boxes.It is indicated that in the northern slope belt of Dongying Sag, the lower part of Es₄ develops semi-deep lake facies to intermittent brine lake facies, leading to thick glutenite and dark mudstone deposit in and below evaporate layers, among which the dark mudstone has experienced high-degree organic matter evolution and can yield large amounts of hydrocarbon. Evaporate layers may act as a favorable barrier bed for sub-salt layers to form independent hydrocarbon bearing system which is mainly self-generating and self-storage lithologic hydrocarbon reservoir. The sedimentary facies, diagenesis and high-pressure sealed boxes control the generation of hydrocarbon reservoir,and especially sub-salt high-pressure sealed boxes may slow down the process of hydrocarbon and diagenetic evolution as well as may provide conditions for the preservation of primary pore and fracture, which are in favor of hydrocarbon generation, migration and preservation.

Sedimentary Micro-facies and Oil-bearing Probability of Ⅲ5-6-Ⅳ1-3 of Block 1 in Jinglou Oilfield,Henan

TIAN Ji-jun

2009, 23(2):  319-325. 

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In order to solve the problem of the serious steam channeling in the development of steam huff and puff  and low reserve tapping efficiency of low permeability reservoir of Block 1 in Jinglou oilfield of Henan Province，high-resolution sequence stratigraphic classification and correlation are made for the Ⅲ5-6-Ⅳ1-3 of Hetaoyuan Formation of Block 1 in Jinglou oilfield based on the theory of high-resolution sequence stratigraphy.Ⅲ5-6-Ⅳ1-3 can be divided into 3 middle-term,10 short-term, 25 super short-term cyclic sequences according to boundaries. Fan-delta front,prodelta, subwater distributary channels and their flanks, subwater interdistributary bay,and far bars can be identified by fully applying the core,drilling,logging data. The oil reservoir type is mainly controlled by tectonics and lithology.This paper provides a new thought for broad exploration fields. The remaining oil distribution is also discussed, and the results can provide an important geological foundation for development adjustment of Jinglou oilfield.

The Technique of Multiple Removal under High Impedance Layers Based on Forward Modeling

YANG Chun-feng DUAN Hong-you LIAO Ren LU Jia-lan SHANG Jian-li

2009, 23(2):  326-332. 

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With the improvement of the exploration degree，exploration target of old oil fields towards the deep and shallow is one of the development directions in East China. Dolomite deposition of lateral stable spread not only shields the effective downwards propagation of the seismic signal, but also generates multiples in Biyang deep area. The speed and density of sand and shale are similar and the difference between their impedances is small in deep series of strata formation after intense compaction, so low SNR is caused,which affects the structure explanation and reservoir prediction. Based on forward modleling result of multiple asympatotic ray of model, the paper states the kinematic characteristics of multiples and provides bases for the choice of the methods of multiple suppression. The paper puts forwards a correlative processing method to improve the processing technology of the deep seismic reflecting quality at high impedance of dolomite in deep depression. Multiple removal and energy compensation by deletion fitting method are used in Biyang deep depression, which improves the SNR and resolution of the deep seismic processing data and gets a good exploration effect.

Study on Geologic Condition Optimization of Raising Withdrawal Rates at the Late Stage of Oilfield Development

YANG Yong-li HUO Chun-liang

2009, 23(2):  333-336. 

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It is an important way to improve discharge capability of an injection-production system by increasing drawdown pressure in old wells. By analyzing water injectivity and production capacity in main microfacies sandbodies, it is concluded that the distributary channel and the mouth bar have more production capability than the front sheet sand has at the late stage of oilfield development. The sheet sand has too poor water injectivity to make up the shortage of pressure caused by raising withdrawal rate, while the distributary channel and the mouth bar have enough water injectivity to reach injection-production balance and to ensure oil well’s sustainable discharge. According to the drilling status, numerical simulation and water-drive performance curve of new wells, residual oil distribution is studied at the late stage of oilfield development. It is concluded that residual oil produced by hydrodynamic methods is rich in distributary channel. So the wells for raising withdrawal rates should be chosen in the distributary channel at the late stage of development in Shuanghe oilfield. Practical result also shows that wells in distributary channel chosen for raising withdrawal rates have an apparent effect on stabilizing oil output and controlling water.

 

The Calculating Method of Horizontal Wells with Hydraulic Fractures for Low Permeability Reservoirs

MU Zhen-bao YUAN Xiang-chun ZHU Xiao-min 

2009, 23(2):  337-340. 

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Based on the problem for the starting pressure gradient and strong stress sensitivity for the low permeability reservoirs,the paper has established the production formula for horizontal wells with hydraulic fractures in different circumstances.If horizontal wells with hydraulic fractures are not partially perforated,the established production formula will be an effective method,and if horizontal wells with hydraulic fractures are partially perforated,the Langzhaoxin production formula will be an effective method instead of other different methods for horizontal wells with hydraulic fractures.The established production formula of the horizontal wells with hydraulic fractures has an important theoretical and practical meanings for low permeability reservoirs.

Study of Flow Units in No.1 Sebei Gasfield of Qinghai Province

ZHAO Yan WU Sheng-he YUE Da-li XUE Yan-xia WEN Li-feng

2009, 23(2):  341-346. 

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Taking the No.1 Sebei gasfield in Qinghai Province as an example, this paper deals with flow units study of gas reservoir. According to the analysis of various reservoir parameters, the relative amplitudes of the SP and the GR curves are selected as the main parameters to separate the flow units into different types. Using those two parameters, the target formations in this zone are sorted into five types, in which, the reservoir qualities of the flow unit types I and II are the best and mainly developed in reefs with high energy;the reservoir quality of the flow unit type III is the better and can be mainly found in reefs with moderate energy; the reservoir quality of the flow unit type IV is the worst and its sedimentary back ground is the reefs with lowest energy; while the flow unit Ⅴ is mud layer and it can be a kind of seepage barrier.The distribution model of flow units and the control effect of fluid distribution system of the study area are made through the integrated analysis. 

Thoughts and Methods for Strengthening Coal Prospecting in the Eastern China

CAO Dai-yong LI Xiao-ming NING Shu-zheng LIN Zhong-yue

2009, 23(2):  347-352. 

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Based on the analysis of the features of coal resources and the difficulties and challenges which coal prospecting is being faced with in the Eastern China, the concepts of coal prospecting style and coal prospecting model have been discussed. By the study of distribution patterns of coal resources and the analysis of coal prospecting practices, three basic coal prospecting styles have been classed as following:(1)the area in the deep or periphery of old coal mines, (2)the area covered with huge Cenozoic strata or deep coal seam, and(3)the area with complicated geological condition. After analyzing the main characteristics of each coal prospecting style, the coal prospecting models in accord with each style have been established. The thought and method of strengthening coal prospecting have been proposed, among which the key is the study of the distribution patterns of coal resources and the technique of integration analysis of multivariate information.

Study of Comprehensive Evaluation of Coalbed Methane Zone in China

YAO Ji-ming YU Bing-song CHE Chang-bo YANG Hu-lin

2009, 23(2):  353-358. 

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Comprehensive evaluation of coalbed methane zone is a complex system，which is controlled by multi-factors and is difficult to estimate. This paper proposes an index system of evaluation based on correlated factors involved in coalbed methane zone and a comprehensive evaluation model that combines the advantages of the AHP and a grey clustering method to guarantee the accuracy and objectivity of weight coefficients. First, the weight of every index is confirmed using the AHP, then a comprehensive evaluation is done by a grey clustering method. In this way, it improves and generalizes some known evaluation methods. An example to illustrate the application of the theoretical results is given. The results show that the method is applicable and realistic with regard to the comprehensive evaluation.In 121 coalbed methane zones in China, Qinshui Basin and the east margin of Ordos Basin are most advantaged zones and the south margin of Ordos Basin,Ningwu, Anyang-Hebi, Songzao are comparatively advantaged zones.

Research of Geologic Storage of Carbon Dioxide Underground Disposal in the South of Jiangsu Province

ZHU Yan-ming ZHAO Wen ZHAO Wen-yong YAN Qing-lei LAN Xiao-dong

2009, 23(2):  359-364. 

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 Fossil energy resource is an important safeguard for rapid development of modern industry, but since the industrial revolution, the results of immoderately consuming of energy resource put a mass of greenhouse gases into the atmosphere and led to a series of environment problems, in which the warming global climate warming is the most fearful problem. Now, people have cognizance of this problem’s ponderance and make a move, and the geologic storage of carbon dioxide (CO₂) is an important project that can be taken to mitigate CO₂  emission to the atmosphere in response to climate change. Aiming at the reduce to the greenhouse gas emission to the atmosphere, this paper analyses detailly geologic storage of carbon dioxide and discusses the fashions of geologic storage in the south of Jiangsu Province. At a result that three candidate fashions have been identified, such as the CO₂ storage in oil and gas reservoirs of Subei oil company for enhancing the oil and gas recovery, CO₂  adsorption in thin coalbeds and in deep saline aquifers or poor oil and gas reservoirs of Jurong basin. Particularly, this paper points out that Jurong basin will be an important site for geologic storage of carbon dioxide, meanwhile the CO₂ geologic storage will include huge commercial opportunity.

Analysis and Fuzzy Comprehensive Assessment of Heavy Metal Contamination of Soil in Tuoketuo Area,Inner Mongolia

ZHU Yan WANG Xi-kuan MAO Xiao-chang LIU Yan-li

2009, 23(2):  365-371. 

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Hetao Plain is a typical kind of irrigated agriculture area in Inner Mongolia. This study focused on the Tuoketuo area located in the eastern part of Hetao Plain. Totally 1,564 samples of the surface soil were analyzed based on the GeoExpl system, and eight heavy metal elements including Cd, Hg, As, Cu, Pb, Cr, Zn and Ni in the top soil were analyzed. Among these heavy metal elements, the maximum of variable index is Hg and the minimum of it is Pb. The high concentration of these heavy metal elements has been found in the northwestern part of the study area. Based on these data, a fuzzy comprehensive assessment is carried out. The results can reasonably reflect the region’s soil quality. The paper concludes that the soil in the Tuoketuo area is not contaminated by heavy metals while it is high in some area, especially along the Heihe River area. Irrigation and the improper usage of pesticides and chemical fertilizers containing heavy metals are considered to be the cause of the heavy metal contamination in the soil.

The Study of Cadmium Assignment in Soil-Large Amount Crop and Its Environmental Significance

LIU Ying-ping KAN Ze-zhongJIN Li-xinLI Zhong-hui

2009, 23(2):  372-377. 

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Based on the Chengdu economic zone multi-purpose geochemical survey results,the content of the Cd element in the staple crops-rice, corn and wheat seed and the Cd in soil are discussed.The results showed that the contents of Cd in those are wheat>rice> corn. pH in soil has great influence on the transfer of Cd element in the soil and accumulation of Cd element in the staple crops. Cd element in acid soil is feasible to enter plants and accumultes there,so it is harmful to environmental ecology.

Pollution Level and Spatial Distribution of Polychlorinated Biphenyls  from Atmospheric Matter PM_2.5  in Beijing

SUN Jun-ling LIU Da-meng ZHANG Qing-hua YANG Xue

2009, 23(2):  378-384. 

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In January 2008, PM_2.5 was sampled concurrently at five contrasting sites: two urban sites (the east gate of China University of Geosciences(CUGB)and the roof of a testing building within CUGB), two industrial sites (coking plant of Capital Steel Plant and a thermoelectric plant), and a background site (Ming Tombs) in Beijing, China. The concentration and spatial distribution of 19 polychlorinated biphenyls (PCBs) congeners were analyzed with isotope dilution and high resolution gas chromatography/high resolution mass spectrometry (HRGS/HRMS) based on US EPA 1668A method. PM_2.5 concentrations were in the range of 101.85-145.57 μg/m³ with mean value of 119 μg/m³, which was 83% higher than the US daily average standard(65 μg/m³), suggesting the atmospheric PM_2.5 pollution is very serious in Beijing city. ∑19PCBs and ∑TEQ concentrations varied from 7.2-16.2 pg/m3 and 8.29-17.81 fgWHO-TEQ/m³, respectively, with an average concentration of 10.9 pg/m³ and 13.58 fgWHO-TEQ/m³.PCBs levels were lower in Beijing compared to other metropolises in the world. The highest PCBs concentration was observed in industrial sites followed by urban sites and background site, incomplete combustion of fossil fuel were main sources of PCBs in Beijing. The aim of this work was to better understand the overall PCBs levels, to identify the source of PCBs in Beijing city, and to provide the scientific foundation for preventing the atmospheric persistent organic pollutants (POPs) pollution. 