Lithologic Reservoirs

In order to promote the seismic reservoir，it is necessary to further expound its concept，contents，key techniques，background and the relations with other related subjects．Seismic reservoir is an interdisciplinary which combines seismics and geology and just in an embryonic stage，and it is applicable for every stages of exploration and development as a subdiscipline of reservoir geology．On the basis of inheriting the thoughts of seismic stratigraphy， sequence stratigraphy and seismic sedimentology，seismic reservoir has more profound connotation and more comprehensive denotation．It uses seismic and geologic data to research the lithology，spatial configuration，space， properties and fluids contained in the reservoir and to describe 3D reservoir space features semiquantitatively and quantitatively，which makes the description of reservoir heterogeneity and reservoir space features more precise． Seismic reservoir will be continuously developed and improved with the fast developing of geophysical techniques．

Application of seismic reservoir to volcanic reservoir exploration in Wuxia area of Junggar Basin

XU Duonian，PAN Jianguo，CHEN Yongbo，HUANG Linjun，WANG Bin，WANG Yanju

2010, Vol.22(3): 5–8 Abstract ( 484 ) PDF (654 KB) ( 500 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.002

Based on th e theory and technology of seismic reservoir,the Permian volcanic reservoir in Wuxia area in northwestern margin ofJunggar Basin is researched．The result shows that the volcanic rock(lava tuff breccia)is resulted from the fissure volcanic eruption，the distribution is mainly controlled by the early crater and the paleogeomorphology before volcanic eruption，and the reservoir space is mainly air hole．By using the technology of the coherence analysis and the paleogeomorphology recovery，the characteristics of the crater and paleogeomorphology before volcanic eruption are identified．The technology of logging and geophysics are applied to predict the favorable lithologies，the forecasting technique for fissure volcanic reservoir is formed and good results have been achieved．

Radiaxial fibrous cement of reefal framestone of Permian Changxing Formation in northeastern Sichuan Basin

HUANG Sijing,WANG Chunmei,TONG Hongpeng,HUANG Keke

2010, Vol.22(3): 9–15 Abstract ( 505 ) PDF (1239 KB) ( 480 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.003

adiaxial fibrous cement(RFC)developed in reefal framestone of Late Permian isolated carbonate platform in northeastern Sichuan Basin．Although the RFC has completely dolomitized，it still presents the typical characteristics of curved twin planes，undulose extinction and distal convergence，and also has the geochemical characteristics of high strontium and high natrium content and dark cathodoluminescence，showing marine fluid environment，as well as laminated cement an d internal deposition in cement．High magnesian calcite deposited in marine environment is the primary mineral of RFC，indicating that spongy reefs of Perm ian Changxing Form ation in northeastern Sichuan Basin developed in a steep platform margin，an d contacted with seawater for tens of millions of years．The internal deposition in RFC indicates that the process of cementation lasted very long and breaked in a short period．This depositional break is relevant to sea level drop in a short period，but as to the RFC development process，the sea level is rising，and the rate of organic reefs iS in accordan t with the rising amplitude of sea level．

Three types of sediment gravity flows and their petroliferous features of Yanchang Formation in Ordos Basin

LI Xiangbo,CHEN Qi,lin,LIU Huaqing,WAN Yanrong,MU Jingkui,LIAO Jianbo,WEI Lihua

2010, Vol.22(3): 16–21 Abstract ( 568 ) PDF (866 KB) ( 713 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.004

Based on cores，outcrop observation and analysis test data,，three types of sediment gravity flows aye identified in the sixth member of Yanchang Formation in the deep water area of lake center in Ordos Basin，including sandy debris flow，classic turbidity current and slump．Sandy debris flow is a new-discovered sandy in the continental petroliferous basin and comes under laminar flow，turbidite formed by turbidity current is turbulent flow，and slump are slumping deformable bodies caused by sliding or slumping in the deep water environment．These three types of gravity flows have essential distinction in the rheological features．In the past，the deposition of turbulent flow was dominant in the research of deep water sedimentation in Yanchang Formation．Three of them are attached in space and transform ed in time．From sandy debris flow to slump，the petroliferous property is weakened，and the A section of classic turbidity is moderate．The further study shows that sandy debris flow is the main contributor for the production in the deep water area of lake center,and its plane distribution controls the accumulation an d high production of the reservoir．

Characteristics and genetic mechanism of volcanic dissolved pore in northwestern margin of Junggar Basin

TAN Kaijun,ZHANG Fan,ZHAO Yingcheng,PAN Jianguo,YIN Lu

2010, Vol.22(3): 22–25 Abstract ( 459 ) PDF (261 KB) ( 499 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.005

Based on core observation，combined with rock section，cast thin section and scanning electronic microscope，the characteristics and genetic mechanism of volcanic dissolved pore in the northwestern margin of Junggar Basin are studied．It is considered that volcanic dissolved pores developed in this area，including dissolved pore in amygdaloidal filling hole，matrix dissolved pore，phenocrysts and breccia dissolved pore，dissolved pore in filling cracks and intergranular diss0lved pore．The phenocryst in the lava，the plagioclase debris contained in pyroclastic rock and the zeolite formed bv matrix and pozzolanic hydration occurred corrosion partly or completely in an acidic medium，which is the internal cause of dissolved pores。while the acidic solution and the channel for fluid media are the external cause． The interaction intema1 and external causes result in the poor dissolution of effusive facies and strong dissolution of explosive facies．

The relationship of heterogeneity and oil-bearing property of Chang 6 reservoir at H area in Ansai Oilfield

GUAN Liqun， QU Hongjun， HU Chunhua， FAN Yuhai， LEI Lu

2010, Vol.22(3): 26–30 Abstract ( 479 ) PDF (725 KB) ( 657 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.006

Based on core observation, testing and logging data of Chang 6 reservoir at H area in Ansai Oilfield, the heterogeneities of Chang 6 1- 2, Chang 6 2-1 and Chang 6 2- 2 sublayers are studied, and the effect and control action of the heterogeneities on oil-bearing property are analyzed. The result shows that there are strong interlayer heterogeneity and strong in-layer heterogeneity, but weak planar heterogeneity of Chang 6 reservoir in the study area. The rhythmicity of grain size in vertical direction and the stratification features are important factors for the hydrocarbon distribution. The in-layer permeability heterogeneity and the difference of stratification coefficient between each sublayer play a weak role in controlling the hydrocarbon distribution. The difference of sand density also controls the hydrocarbon distribution, but not the main controlling factor. The oil-bearing properties are mainly controlled by the sand body distribution and reservoir properties, and the microscopic heterogeneity in pore structure controls the full degree of hydrocarbon entering into the reservoirs.

Organic geochemical characteristics of Paleozoic marine source rocks in northern margin of Upper Yangtze Platform

GONG Daxing，LIN Jinhui，TANG Yunfeng，WU Chihua，SONG Huaying

2010, Vol.22(3): 31–37 Abstract ( 512 ) PDF (724 KB) ( 544 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.007

In Paleozoic, it widely deposited a set ofmarine carbonatite and pelite rocks in the northern margin of Upper Yangtze Platform. By means of systematic sampling among 16 sedimentary sections in this area, combined with organic geochemical analysis, it confirms that the effective source rocks mainly developed in Lower Permian, Lower Silurian, Upper Ordovician and Lower Cambrian. The types of the source rocks are Ⅰ and Ⅱ1, which have good capability of hydrocarbon generation, and still have the capacity of gas production. It is concluded that the main source rocks are from Lower Cambrian and Lower Permian，and maybe there are some good source enrichment layers in parts of Lower Silurian and Upper Ordovician.

Reservoir diagenesis of Badaowan Formation in Kekeya structure of Taibei Sag

ZHONG Jinyin,DAI Hongming,WANG Man

2010, Vol.22(3): 38–42 Abstract ( 436 ) PDF (967 KB) ( 333 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.008

The sandstone of Badaowan Formation developed in Kekeya structure of Taibei Sag under braided delta is mainly composed offeldspathic lithie sandstone and lithic sandstone．By means of thin slices，cast section and scanning electron microscopy observation as well as X-ray diffraction analysis，the petrologic characteristics，diagenesis stage division，diagenesis type and the influence on pore of Badaowan Formation aye studied．The results show that the sandstone developed in study area is in late diagenesis A2 stage，and experienced compaction，chlorite formation，quartz secondary enlargement，calcite precipitation，cementation and feldspar denudation．Compaction and cementation aye the main destructive diagenesis，while denudation is the main constructive diagenesis．Especially，the feldspar denudation is the significant factors favorable for reservoir．

Sequence stratigraphy and sedimentary facies of Yan’an Formation in Mahuangshan area of Ordos Basin

HAN Meimei，LI Zhongdong，FENG Yibo，XIE Shiwen

2010, Vol.22(3): 43–48 Abstract ( 402 ) PDF (589 KB) ( 544 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.009

Yan’an Formation has great potential for oil and gas exploration in Mahuangshan area of western Ordos Basin．Based on the analysis of seismic data，well cores，well logging and cast slice，it is believed that Yan’an Formation experiences evolvement of incised valley filling,delta plain，prodelta，and delta plain-meandering river,so it is a whole transgression and regression cycle．Low system tract is composed of filling sandstones of incised valley，of which the distribution is controlled by Early Jurassic palaeogeomorphology，and the sandstone deposited in lower places． Transgressive system tract consists of delta plain，and maximum flooding surface lies in black mudstones of prodeha．High system tract is composed of delta plain and meandering river． Outside．source play and distal-source play are distinguished by maximum flooding surface．Filling sandstones of incised valley of low system tract have thick sandstones，high reservoirs，near resources and plentiful traps，so outside—source can trap petroleum easily ． However, distal-source plays BYe secondary reservoirs which form in high system tract and are estroyed from outside-source play.

Characteristics of Chang 6 reservoir in Zhengzhuang oil region of Ordos Basin

WANG Yang,WANG Guicheng,WANG Yujun,JIA Wei

2010, Vol.22(3): 48–52 Abstract ( 446 ) PDF (673 KB) ( 572 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.010

Based on the core analysis and microscopic observation，it is believed that the rocks of Chang 6 reservoir are mainly composed of arkose with lOW compositional maturity and medium texture maturity．Reservoir properties are mainly low porosity and low-super low permeability．The reservoir distribution is mainly controlled by sedimentary facies．The sedimentation type is mainly delta front subfacies．Subaqueous distributary channel and mouth bar sand bodies are the main reservoirs．The denudation of laumontite developed well in Chang 6 reservoir，which plays a key role to the reservoir improvement．

Sedimentary characteristics of sublacustrine fan of Middle Triassic Zhongyou Formation in AT1 area，Tahe Oilfield

MA Hongtao,CAI Yue,FU Guomin

2010, Vol.22(3): 53–58 Abstract ( 459 ) PDF (1012 KB) ( 582 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.011

Middle Triassic Zhongyou Formation in A T1 area of southern Tahe Oilfield is an important oil and gas． beating layer，of which the sedimentary type，sand body distribution，reservoir control and other kinds of geological issues are paid much attention to．Based on seismic inversion，core description and logging analysis，combined with cast thin section and grain size analysis，the sedimentary facies and characteristics are studied．The result shows that Middle Triassic Zhongyou Form ation in AT1 area of Tahe Oilfield belongs to sublacustrine fan deposits，and AA and AB type non—typical Bouma sequence are widely developed．Meanwhile，Zhongyou Formation of AT1 area mainly developed middle fan subfacies，among which braided channel，interchannel overflow，non-channel sand sheet are identified．The main reservoir sand is middle fan—braided channel．Based on the regional geologic setting，the genetic mechanism of turbidite fan is discussed and corresponding sedimentary model is established．

Liuhua organic reef and reservoir characteristics of Zhujiang Formation in Pearl River Mouth Basin

HU Cheng，ZHENG Rongcai，DAI Chaocheng

2010, Vol.22(3): 59–65 Abstract ( 492 ) PDF (1379 KB) ( 536 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.012

Liuhua organic reef of Zhujiang Formation is located in the tertiary structure named Dongsha uplift which lies in Pearl River Mouth Basin．It is composed of rhodolite reef limestone，coralline framework reef,reef brecciola and bioclastic limestone．It can be divided into four types of intrafaeies and microfaeies，including reef core，reef base，reef fiat and reef front．It possesses the sedimentation model of platform edge moundy organic reef．The effectively accumulation spaces mainly are organic framework，primary intergranular pores，followed by different dissolved pores． The reservoir behavior is controlled by sedimentary microfaeies and diagenesis．The reef limestone of reef core microfacies is most favorable for the reservoir development，followed by bioclastic limestones of core base and reef flat microfacies．

Origin and distribution of interbeds and the influence on oil-water layer：An example from Mosuowan area in the hinterland of Junggar Basin

ZOU Zhiwen,SI Chunsong,YANG Mengyun

2010, Vol.22(3): 66–70 Abstract ( 498 ) PDF (674 KB) ( 679 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.013

The main sedimentary facies type of J1s2 is delta front subfacies in northern Mosuowan area of Junggar Basin，where developed three types of interbeds：muddy，calcareous and physical，with various origins and controlling factors．According to logging response characteristics，the calcareous and muddy interbeds can be identified．The main interbed in this area is muddy interbed with some calcareous interbed，and it is mainly controlled by sedimentary facies， as well as the later diagenesis and faulted structure．The low porosity and permeability and sealing efect of interbeds control the oil-water distribution in the formation，which easily causes oil-water layer phenomenon．

Refined reservoir evaluation of the second member of Shanxi Formation in mid-eastern Ordos Basin

ZHANG Manlang，LI Xizhe，GU Jiangrui，XIE Wuren

2010, Vol.22(3): 71–77 Abstract ( 391 ) PDF (585 KB) ( 548 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.014

Shanxi Formation in mid-eastern Ordos Basin can be divided into three sedimentary sequences．SQ8 (the second member of Shanxi Formation)can be divided into lowstand system tract，transgression system tract and highstand system tract，with the main sand body developed in lowstand system tract．SQ8一LST can be subdivided into three progradational parasequence sets，which prograded into the lake．They are L1，L2 and L3 from below to top with the thickness varying from thin to thick and the distribution area from small to large．In L1 parasequence set，only one main sandstone belt deposited in the study area，which extends nearly north-southward with the length of 100 km，10~15 km in wide，and with the sandstone thickness of 2～ 10 m．In L2 and L3 parasequence sets。the sandst0ne distribution are very similar,developed 5～6 north-southward and north-eastward sandstone belts，which are 10~25 km in wide，200~230 km in length，with the sandstone thickness of 4~20 m．L1 parasequence set is initial filling deposition after large scale marine regression．Its sandstone composition is complicated with poor sorting and the reservoir property is relatively poor．But up to the parasequence sets of I22 and L3，the reservoir properties becon1e better obviously．Favorable reservoir sandstones developed in sedimentary facies of distributary channel in delta plain，subaqueous distributary channel and mouth bar in deha front，which mainly distributed in middle-upper part of the lowstand system tract．The reservoir property of delta front sand body is better than that of delta plain sand body，while point bar sand body is poorer in reservoir property．

Differential tectonic movement of Yanchang Formation in southwestern margin of Ordos Basin and its geologic significance

ZHANG Xuefeng，ZHAO Yande，ZHANG Mingji

2010, Vol.22(3): 78–82 Abstract ( 433 ) PDF (579 KB) ( 475 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.015

Huanxian- Zhenyuan area is one of the major exploration areas in southwestern margin of Ordos Basin in recent years. Some new geology phenomenons appeared and were cared in the exploration. Based on the analysis of tuff, seismites and limestone gravel in Chang 7 to Chang 6 reservoir and thicken layers in Chang 7 to Chang 1 reservoir, it is believed that areal tectonic setting during Chang 7 to Chang 6 depositional stage is different from that during Chang 9 to Chang 8 depositional stage, which results in different formations, different sequence, different sedimentary settings, different lithologies and different reservoir properties. Different exploration methods are proposed for different layers and different reservoirs.

Study and application of seismic technologies for key exploration fields

WANG Xiwen，YONG Xueshan，WANG Yuchao，GAO Jianhu，WANG Xiaowei，HU Ziduo，LIU Weifang，TAO Yunguang

2010, Vol.22(3): 83–90 Abstract ( 472 ) PDF (756 KB) ( 566 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.016

The procedures of seismic data processing,favorable reservoir prediction and hydrocarbon detection are studied for key exploration basins and fields such as lithologic reservoir seismic exploration in the southwest of Qaidam Basin，carbonate fracture-cavity reservoir exploration in Tarim Basin，high-steep structure exploration in Sichuan Basin and Tuha Basin and salt dome and subsah imaging in Pre-Caspian Basin．So many technologies are developed，including static correction technology with multiple information restrictions and combination of many methods，surface consistence processing technology，pre-stack fidelity and noise elimination technology，anisotropic floating datum pre-stack imaging technology and wave equation pre-stack depth migration technology，forward modeling and multi-attribute semi-quantitative fracture-cavity reservoir prediction technology，3D fracture-cavity system quantitative description and fluid detection technology．Meanwhile，some associated technologies are also developed，including 3D seismic data joint integration processing interpretation technology，semi-quantitative and quantitative description technology of carbonate fracture-cavity reservoirs and complex surface and high-steep structure imaging and subsalt imaging technology．The significant exploration results are obtained from the application of these technologies in some key exploration basins and fields．

Rock physics for remaining oil distribution prediction in water flood field

LIU Wenlin

2010, Vol.22(3): 91–94 Abstract ( 481 ) PDF (347 KB) ( 502 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.017

The velocity contrast caused by the reservoir property variation in long period of water flood recovery in the old fields of eastern China is obviously greater than that caused by oil displacement water．So seismic data can be used to predict the remaining oil distribution．Time lapse seismic is applied to obtain the 3D seismic amplitude difference before and after water flood recovery．Because of the seismic response difference of fluids．it is more effective than conventional hydrocarbon detection technology to identify the remaining oil distribution．The model and application show that practicability of time lapse seismic for predicting remaining oil distribution．Finally an approach is proposed that using time lapse seismicis to carry out pre-stack.

Ground stress direction and fracture distribution law of Ordovician in Lunxi area

ZHAO Jun,WANG Miao,QI Xingzhong,FU Haicheng

2010, Vol.22(3): 95–99 Abstract ( 493 ) PDF (335 KB) ( 734 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.018

The research of fracture distribution direction is an important element for the development of fractured reservoirs．and it is directly related to well network deployment of reservoirs．The distribution of fracture direction is closely related to the stress field．By using of dipmeter and imaging logging data as well as the borehole stress analysis and borehole caving mechanism，the direction of ground stress of Ordovician carbonate rocks in Lunxi area is analyzed， and it is inferred that the distribution direction of structural fractures is NE-SW in the study area．It is man ifested that the direction of present-day ground stress and the effective fracture are the same direction or a slight angle oblique crossing．

Application of fine facies-constrained geological modeling technology in adjustment and tapping oil potential of old oilfields： An example from Suizhong 36-1 Oilfield

LV Zuobin，ZHAO Chunming，HUOChunliang，XUEYanxia，ZHANG Lan

2010, Vol.22(3): 100–105 Abstract ( 507 ) PDF (553 KB) ( 580 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.019

Firstly, based on the comprehensive research of seism, logging and geology prepared forgeological modeling, the modeling units are reasonably divided for the period I of Suizhong 36-1 Oilfield. According to the sedimentary microfacies interpretation results of single wells, combined with sedimentary microfacies assemblage of delta front, the sedimentarymicrofacies plan of each sedimentary unit is drawn up, underwhich the 3D sedimentarymicrofacies model is established. Secondly, on the basis of the facies-constrained stochastic simulation and the distribution feature of macrofacies property parameters, 3D porosity model is established by facies-constrained method. Finally, faciesconstrained method and co-simulation of porosity model are applied to establish the 3D permeability model. The dynamic data of newadjustment wells and old production wells showthat the numerical simulation result based on the geologicalmodel coincides well with the production performance of the oilfield．

A new method for single well controlled reserves by using pressure build up curve

LIU Pengchao，TANGHai，LV Dongliang，LIU Tiecheng，JIANG Zuoyan，WANG Didong，WANG Yong

2010, Vol.22(3): 106–109 Abstract ( 508 ) PDF (311 KB) ( 698 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.020

The methods for calculating the single well controlled reserves by pressure build up curve are mostly using time to calculate the single well drainage area, and then apply volumetric method to obtain single well controlled reserves. If the test data is undulatory or not determined, it will be hardly to get the single well controlled reserves. A new method forsingle well controlled reserves based on pressure is proposed, which can avoid the limits of the methods based on time. It uses Horner straight line to calculate the single well drainage area, and then obtain the single well controlled reserves. The practical application result proves the reliability and validity of this method.

Comparative analysis of elastic impedance

WANG Hao，LUO Bing，LI Ting

2010, Vol.22(3): 110–113 Abstract ( 532 ) PDF (348 KB) ( 594 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.021

Presently, there are variously methods for calculating elastic impedance by different seismic elastic impedance inversion softwares, and seismic elas tic impedance inversion were often simply applied though some requirements hadn’t been discussed in detail, which causes yield difficulties for actual productions. Therefore, based on four typical types of gas-bearing sandstone models, calculation accuracy of elastic impedance（EI）, reflected impedance（RI） and generalized elastic impedance （GEI） are analyzed and compared. Moreover, based on Biot-Gassman theory, fluid replacement is applied for gas-bearing sandstones model advanced by Ostrander, and the sensitivity to fluid of different elastic impedance is discussed when water saturation changed. The following conclusions can be obtained through the calculation of four types of gas-bearing sandstone models: As for Class Ⅰ and Class Ⅳ, Zoeppritz equations can be substituted forthe EI, RI and GEI when the incident angle is less than 40 ;As forClass Ⅱ, Zoppritz equations can also be substituted when the incident angle is less than 30 ; However, these three kinds of elastic impedance can not be applied for Class Ⅲ; The idea of the partial derivative is applied for the gas-bearing sandstone models advanced by Ostrander, the result shows that, RI is more sensitive to fluid than EI and GEI as incident angle is bigger.

Influence of pore shape on AVO response

HU XiaoLi，TAN Dalong

2010, Vol.22(3): 114–117 Abstract ( 495 ) PDF (433 KB) ( 594 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.022

Reservoirs are multiphase medium composed by the matrixs of solid, pore and the fluid in the pore. The properties of the pore should not be overlooked in oil and gas exploration. In orderto analyze the influence of pore shape on AVO response, two sets of sand shale model are selected to classify the pores by the pore shape. The equivalent modulus of rock is obtained by using Kuster- Toksoz formula, and then Biot- Gassmann equation is applied for fluid substitution to obtain the equivalent modulus of saturated rock. Finally the reflection coefficient obtained by Aki- Richards formula is used to carry out the AVO forward modeling. The result shows that the pore shape has significant effects on AVO response, and the influence onAVOresponse of different types of fluid-saturated rocks is similar.

Application of multi-attribute and neural network method to hydrocarbon reservoir prediction

HOU Bin， GUIZhixian， XU Huiqun， HEJiacheng

2010, Vol.22(3): 118–120 Abstract ( 421 ) PDF (265 KB) ( 551 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.023

Seismic attributes contain abundant geophysical information. There are so many seismic attributes and the relationship between attributes and reservoir characteristics is complicated. Single attribute analysis cannot assure the prediction accuracy. Artificial neural network technology has strong nonlinearmapping ability, so it can be applied to improve hydrocarbon prediction accuracy. The gradient descent learning algorithm is used in neural network. It can avoid local minimum and effectively speed up the network convergence to achieve the global optimal network and improve its forecasting performance.

Moving boundary does not truly exist

LI Chuanliang

2010, Vol.22(3): 121–122 Abstract ( 504 ) PDF (281 KB) ( 431 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.024

Starting pressure gradient introduces a new concept-moving boundary-into the flow in porous media. In order to clarify the property of moving boundary, a theoretical study is conducted on the pressure propagation in reservoirwith starting pressure gradient. According to the study, a reservoir can be divided into two zones: flowing zone and non-flowing zone, while starting pressure gradient exists. The division between the two zones is called moving boundary. Howeverfromthe moving boundary, a paradox comes out that the fluid in non- flowing zone can flowand can not flowsimultaneously. Flow theory in porous media can not be self-consistent. Moving boundary comes fromstaring pressure gradient. But staring pressure gradient is not existing and just a misleading experimental phenomena. So moving boundary does not truly exist. Removal of moving boundary makes the theory of flow in porous media selfconsistent perfectly.

Gas hydrate forecasting model and its influencing factors

LIU Yun，LU Yuan，YI Xiangyi， ZHANG Junliang， ZHANG Jinliang，WANG Zhenxi

2010, Vol.22(3): 124–127 Abstract ( 497 ) PDF (393 KB) ( 1001 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.025

The generation of hydrate has brought a lot of difficulties in processes such as gas extraction, gas gathering and so on. The establishment of forecasting model is a puzzle in hydrate prevention and cure. The advantages and disadvantages of four commonly used forecasting model are summarized. The statistical thermodynamics principle is used to establish gas hydrate forecasting model, and five main factors that affect gas hydrate formation are analyzed, including the gas composition, temperature and pressure, ion concentration, acidic gas and inhibitor added. This forecasting model is applied in Luojiazhai gas reservoir, and the result shows that the predictive values are consistent with the experimental results. The establishment of gas hydrate forecasting model is significant for hydrate prevention and guiding gas production.

Influencing factors for displacement efficiency in the main reservoirs of H area

CHEN Zhaobing， ZHU Yushuang，WANG Pingping， LI Chao， ZHAO Xin， ZHANG Yang

2010, Vol.22(3): 128–132 Abstract ( 481 ) PDF (679 KB) ( 521 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.026

The main reservoirs of Triassic in H area of Ordos Basin are Chang 6, Chang 4+5 and Chang 2, which are typical low-permeability reservoirs. In order to obtain the regulations of flowing liquid and the characteristics of two phase flow, the water/oil displacement experiment inHarea is carried out by real sandstonemodel. Thin section analysis, physical property, scanning electronic microscope, relative permeability andmercury penetration are applied to analyze the influencing factors for the displacement efficiency in this area, which include pore structure, displacement pressure andwettability. Physical propertyhas little effect onthe displacement efficiency.

Application of grey association analysis to the study of remaining oil distribution

PENG Debing，TANG Hai，LI Chengxiang， SU Chunlei，WANG Yan，FU Chunmei

2010, Vol.22(3): 133–136 Abstract ( 494 ) PDF (534 KB) ( 522 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2010.03.027

The basic theory and thought of grey association analysis are introduced. The correlation coefficient, correlation degree and weight coefficient are obtained more reasonably and accurately through quantification of resolution coefficient. Taking X fault-block reservoir for example, five static and dynamic parameters which can influence remaining oil distribution are selected as evaluation index to expound the computation process of weight coefficient of each parameter and own grading, and a comprehensive score for remaining oil distribution is obtained. The evaluation result coincides with the actual production, which proves that this method can be applied to the remaining oil distribution evaluation in the later development.