Table of Content

25 June 2003, Volume 24 Issue 2

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RESERVORING CHARACTERISTICS ANALYSIS OF GASFIELDS IN CHINA

Wang Tingbin

2003, 24(2):  103-110.  doi:10.11743/ogg20030201

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There are some differences in reservoiring conditions between oil and natural gas, dynamic equilibrium theory of gas migration,accumulation and reservoiring would then be regarded as the basic method to study the reservoiring characteristics of natural gas. Two key factors,volume and time of gas accumulation, can be used to sum up the complicated reservoiring courses of gasfields in China, including: super-late (Neogene-Quaternary) hydrocarbon generating and resevoiring type; late (Eogene-Neogene) hydrocarbon generating reservoiring type; early (mainly in Mesozoic) hydrocarbon generation and accumulation,and lately (Neogene-Quaternary) reservoired and finalized; and early (mainly in Mesozoic) hydrocarbon generating and reservoiring type.Although there are great differences of reservoiring characteristics in different type basins, the tectonic evolutional history in Himalayan period has played an important role in controlling the reservoiring and distribution of natural gas in China, which can be concluded as promotion and destruction, and the former is dominant. There are currently three main regions of natural gas exploration in China, including foreland basins in west-central China, three large cratonic composite basins (Sichuan basin,Ordos basin and Tarim basin),and offshore rift and continental margin basins. The study shows that the most prolific regions in China are those basins and depressions which have dominantly been reservoired and finalized in late and super-late periods.

SYSTEMATOLOGY IN RESEARCH OF RESERVOIRING THEORY──DISCUSSION FROM PETROLEUM SYSTEM

Song Guoqi

2003, 24(2):  111-115.  doi:10.11743/ogg20030202

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A system is an organic integer with a certain function, which consists of several factors to be related to and interacting on each other. Systematology is a science studying the common characteristics,nature, principle and regularity of objective reality system. Complying with systematology idea, reservoiring theory system has been studied to have different levels and structures. Petroleum system refers to the geological factors and geological processes which are necessary for oil and gas migration and accumulation. Various exploration stages,research aims and recognitions would have different requirements to theoretical system. Development of reservoiring theory should have be based on theory of petroleum system,be guided by theory of composite hydrocarbon accumulation zone,and reflect the evolution of reservoiring theory to be from materials description-mechanism analysis-regularity summarization. Presently, a further study of dynamic reservoiring processes need the reservoiring theory regarding the migration pathway system as key factor so as to predict effectively oil and gas reservoirs.

INDOSINIAN NAPPE STRUCTURE AND ITS HYDROCARBON SIGNIFICANCE IN HEFEI BASIN AND NORTH HUAIYANG TECTONIC ZONE

Cao Gaoshe, Li Xuetian, Liu Deliang, Zhou Songxing, Gao Yijun

2003, 24(2):  116-122.  doi:10.11743/ogg20030203

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On the basis of analysing drilling and logging data and geophysical profiles, nappe structures in north Huaiyang tectonic zone have been studied,and the existence,pattern, dynamic background and hydrocarbon significance of Indosinian nappe structures have also been discussed.It is suggested that the unified nappe structural system might be composed of north Huaiyang tectonic zone and Hefei basin in Indosinian period, and the dynamic background might be resulted from the intra-continental subduction of deep crust of North China plate towards the inner orogenic zone.The Indosinian tectonic movement belongs to typical continental structures,and the thrusting nappe structures formed in the Indosinian period might be favorable to hydrocarbon preservation.

GROWING CHARACTERISTICS OF CHANGYUAN FAULT AND HALF-GRABEN EVOLUTION IN DONGPU DEPRESSION

Sun Simin, Peng Shimi, Wang Xinwen

2003, 24(2):  123-125.  doi:10.11743/ogg20030204

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Through analysis of distribution features of vertical displacement in different geological periods,the growing process of Changyuan fault has been inversed,which might be originated from two isolated fault segments.This study shows Changyuan fault has different growing characteristics in different geological periods.It consisted of the two individual normal faults in the Es₄ depositional stage,they were joined together and became one fault in the Es₃ depositional stage.However,each segment still had its own displacement features as independent normal fault,i.e.the largest vertical displacement to be in the central part of the fault segment,and became smaller and smaller to both ends.Both fault segments separately controlled the half-grabens,with displacement deficit on the joining site,where a transverse uplift was formed separating the half-graben.An integrated fault system had been successively formed in the Es₄ to Dongying stage.The depo-center then began to migrate toward the central part of Changyuan fault, the transverse uplift began to subside,and an unified half-graben was then formed on the hanging wall of Changyuan fault.

VOLCANIC MASSIF AND SEDIMENTARY FACIES BELTS CONTROLLED BY XUJIAWEIZI FAULT TERRACE BELTS IN SONGLIAO BASIN

Cheng Rihui, Wang Pujun, Liu Wanzhu, Shan Xuanlong, Chen Shumin

2003, 24(2):  126-129,135.  doi:10.11743/ogg20030205

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A series of fault terrace belts were found in Xujiaweizi fault depression, from the margin to the center of the depression, in late Juassic to early Cretaceous.The synsedimentary faults,controlling the generation of fault terrace belts,segmented the secondary geological units,such as uplift belt,slope belt and hollow zone.Xujiaweizi fault-depression can be divided into north and south regions:the former consists of west and east two half-grabens;while the latter is composed of three half-grabens.Each half-graben generally consists of basin-margin uplift,steep-slope fault terrace,hollow zone and gentle-slope fault terrace.There is a secondary uplift between two half-grabens. The development of fault terrace belts controlled the topographies from the margin to the sag in the basin, and hence controlled the types of depositional facies and their distributions,too. Moreover, volcanic activities induced by faulting or associated with faulting resulted in the infilling of volcanic materials in the basin,and the transformation of secondary tectonic pattern and topography in the basin, which would, therefore, controlled the types and distribution of sedimentary facies.It is susgested that the distribution of volcanic massifs and sedimentary facies have been controlled by the fault terraces in Xujiaweizi fault depression.Such control should have been affected by multiple factors, and cannot be easily explained with a single meachanism.

HYDROCARBON ORIGIN AND RESERVOIRING HISTORY OF BAIMIAO FIELD IN DONGPU DEPRESSION

Feng Jianhui, Tan Yuming, Luo Xiaoping, Wang Weidong, Pan Changchun, Sheng Guoying, Fu Jiamo

2003, 24(2):  130-135.  doi:10.11743/ogg20030206

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Baimiao field,located in the southern part of Dongpu depression, is mainly a condensate gas field,with oil ring at the bottom.The study of biomarkers indicates that the oil in different parts of the structures might be derived from various source rocks.The crude oil in deeper positon (bottom and flank) has been originated from the 2nd submember source rock of 3rd member,Shahejie Fm (Es₃²),and that in the higher part of the structure top has been originated from the Es₃³, Es₃⁴ and even Es₄ source rocks.The former, in comparison to the latter, is characterized by relatively abundant oleanane,gammacerane,C₃₀ diahopane and C₂₉Ts,high values of Ts/Tm and diasterane/regular steranes ratios, and high C₂₉ββ/(αα+ββ)and 20S/(R+S) indexes of C₂₉ steranes. The low values of C₂₉ββ/(αα+ββ)and 20S/(R+S)of C₂₉ steranes indicate the source rocks of Es₃³ and Es₃⁴ submembers might generate hydrocarbons at early maturation stage.

CHARACTERISTICS OF STRESS FIELD IN UPPER SHAXIMIAO FORMATION,XINCHANG GASFIELD

Wu Zhijun, Yang Yu, Liu Yingkai

2003, 24(2):  136-139.  doi:10.11743/ogg20030207

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The directional distribution and deformation intensity of structures in Xinchang gasfield,located in the center of western sag in Sichuan basin, have been found to be largely different from those on both sides. As a whole,Xinchang gasfield is in the weak deformation area, it might have been reversely twisted in NS direction and compressed in WE direction during Indosinian to later Yanshan movements,and only the EW direction compressional stress field that occurred during the middle Himalayan deformation stage is relatively evident.The structure is of weak deformation type with only a few little faults,and rarely with stress fields traces in cores.The characteristics of stress field are as follows: the main direction of largest horizontal stress is about 150°,the largest and smallest principal stresses (σ_v and σ_n) are both nearly horizontal,and the largest principal stress is slightly larger than the vertical stress (σ_H) of rock strata and fracturing stress of rock.

SEDIMENTARY SYSTEMS AND EVOLUTION CHARACTERISTICS OF LOWER TERTIARY LIUSHAGANG FORMATION IN FUSHAN SAG

Liu Lijun, Kuang Hongwei, Tong Yanming, Wang Yun

2003, 24(2):  140-145.  doi:10.11743/ogg20030208

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Through composite method of geological, log, seismic and core analyses, depositional system of Eogene Liushagang Fm in Fushan sag has been studied. Braided delta and lacustrine facies are two major depositional systems developed in Liushagang Fm. The braided delta facies can be divided into three sub-facies: delta plain sub-facies, delta front sub-facies and pro-delta sub-facies based on depositional environment and sedimental features. Among which,the delta front sub-facies constitutes the main body of sediments characterized by abundant sedimentary structures, such as the lateral-accretionary cross beddings. The lacustrine depositional system can also be divided into four sub-facies, i.e. shallow lacustrine, moderate lacustrine,deep lacustrine and sublacustrine fan sub-facies.The sublacustrine fan deposit is relatively well developed and characterized by the interbeddings of sand bodies,glutinites, and mudstone and shales.It is vertically characterized by progading and composite stacking,and thickening and coursening upward sequences. The lateral evolution of Liushagang Fm shows the evolutional patterns of sediments from basin center to basin margin to be sublacustrine fan,deep lacustrine, moderate lacustrine,delta front,and delta plain.The sediments have mainly sourced from the southern part of Fushan sag. Very thick black mudstone occurring in the 2nd member of Liushagang Fm constitutes the main oil source rock and caprock;while the thick sandbodies in braided delta front sub-facie belt, developed in the 1st member and 3rd member of Liushagang Fm,would be good reservoirs,both of them would constitute a good combination of source,reservoir and cap rocks.The Liushagang Fm in Fushan sag would,therefore,be the target of further exploration.

STUDY OF SEDIMENTARY CHARACTERISTICS OF SUBAQUEOUS FAN IN EASTERN SLOPE OF CHENGDAO

Yuan Xiangchun, Zhong Jianhua, Gao Xilong, Sun Xirui, Li Zhaoyan

2003, 24(2):  146-151.  doi:10.11743/ogg20030209

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Sand body in the 3rd member of Dongying Fm in eastern slope of Chengdao is controlled by subaqueous channel,with subaqueous fan to be characterized by both traction and turbidity current sediments. The petrographic facies include hybrid matrix-supported gravelly sandstone, pebbled sandstone, argillaceous-supported sandstone and sandy siltstone,which are mainly characterized by coarse-grained sediments. Depositional beddings such as graded bedding,massive bedding,parallel bedding, cross-bedding and wave bedding,are well developed;and depositional structures including slump,convolute and load-dehydration,are also developed very well.Obvious channel downcutting has been recognized in the seismic profiles,which appears as wide semi-lens—being flat on the top and being slightly convex at the bottom;and the spontaneous potential log shows positive rhythm,with columnar and box-like shapes changing respectively from high amplitude to medium amplitude,which are closely related to different lithology and different depositional facies.On the basis of lithology, and electric and reservoir property analyses,depositional facies in this area can be divided into 7 micro-facies,including subaqueous channel,interchannel unconcentrated flow, interchannel splay, subaqueous levee,interchannel mudflat, river mouth lobe and sheet sand microfacies.

HYDROCARBON RESERVOIR TYPES RELATED TO HALITE IN PALEOGENE, NORTHERN DONGPU DEPRESSION

Xu Juzhen, Zhang Xiaoyi, Zhang Hong, He Yanmei

2003, 24(2):  152-156.  doi:10.11743/ogg20030210

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Dongpu depression is a typical salt-lake basin in Bohai Bay region.Two sets of halites have been deposited in the two Paleogene depositional cycles.The halites in the 3rd member of Shahejie Fm (Es₃) can be divided into three sub-units: the 4th sub-member (Es₃⁴),3rd sub-member (Es₃³),and 2nd sub-member (Es₃²),which mostly distribute near the central uplift belt in northern Dongpu depression. Halites have been compacted and become very tight,which would become barriers and result in higher geotemperature and formation pressure in the underneath stra-ta,and would be favorable to the transformation of organic matters in the underlying source rocks into oil and gas. Meanwhile, halite is also a good cap rock, and would be in plastic state under high temperature and high pressure condition. Because of the barrier and deformation of the halites, multiple reservoir types related to halites have been formed, such as graben-like anticlinal oil and gas reservoirs in the upper part of the halite, oil and gas reservoirs laterally blocked by halite, anticlinal oil and gas reservoirs under the halites and lithological oil and gas reservoirs. As a result of the shifting of halite depocenters during the deposition of Es₃,there are always sandstones under the Es₃⁴, Es₃³ and Es₃² halites, which would become relatively good combination of reservoir and cap rock,and even result in very rich accumulations of oil and gas beneath the halites in central uplift belt. Although the Es 1 halite is thin, its distribution area is large and it would still play the key role in the hydrocarbon accumulation in the 2nd member of Shahejie Fm (Es₂). Much attention should be further paid to those areas, such as deep horst belt under the Es₃⁴ halites in eastern Wenliu,the Es₃² Wen 93 fan between the halites in eastern Wenliu, the Qianliyuan sag in eastern Dongpu depression and Haitongji sag in western Dongpu depression.

SEDIMENTARY CHARACTERISTICS AND RESERVOIR SIGNIFICANCE OF EOGENE Es₃ FAN DELTA IN GUBEI OILFIELD,ZHANHUA DEPRESSION

Yang Jianping, Zhao Weiwei, Jiang Zaixing

2003, 24(2):  157-161.  doi:10.11743/ogg20030211

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Various types of fan delta systems have been developed in different evolution stages of faulted basin. Being controlled by the supply rate of sediments, expansion rate of available space and nature of lake basin's boundary fault, four types of fan deltas have been deposited in the 3rd member of Shahejie Fm(Es₃) in Gubei oilfield. Retrograding fan delta has been deposited along with the transgression of the lake in the early and middle Es₃ ;and the prograding fan delta has been deposited during the regression of the lake in late Es₃.There are obviously different sedimentary characteristics, reservoir distribution and reservoir quality between the steep fan delta and the gentle one, the latter has better reservoir quality with an average porosity of 18.2% and average permeability of 293×10^-3 μm², because it has relatively shallow burial depth and weak diagenesis.In addition, the microfacies of sediments would also control the reservoir quality.The glutenites deposited in subaqueous distributary channels in front of the fan delta have the best reservoir quality with an average porosity and permeability of 20.5% and 350×10^-3 μm²,respectively.The deep lacustrine dark-colored mudstones constitutes the major hydrocarbon source and cap rocks, and the glutenites deposited in front of the fan delta are relatively good reservoirs,which would constitute a good combination of source,reservoir and cap rocks. The Es₃ would,therefore,be the target of further exploration.

STRESS SENSITIVITY AND POROPERM LOWER LIMIT OF DELIVERABILITY IN THE LOW-PERMEABILITY RESERVOIR

Wang Xiujuan, Zhao Yongsheng, Wen Wu, Chi Bo, Sun Yu

2003, 24(2):  162-166.  doi:10.11743/ogg20030212

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core samples collected from Yushulin,Chaoyanggou and Toutai oilfields to the east of Daqing placanticline have been tested with the CMS-200 porosity and permeability tester.For the sake of observing the stress sensitivity of low permeability reservoir during the oilfield exploitation, initial pressure (initial formation pressure) and maximum confining pressure (maximum overburden pressure)have been chosen;and the recovery time of simulated pressure have properly been prolonged,due to the consideration of the protracted nature of field's waterflood development and the rheological property of the rocks. Experimental results show that the low-permeability reservoir is relatively sensitive to stress change, i.e. the permeability will have a relatively large decrease with the increase of stress.However, permeability has also recovered to a certain degree with the waterflooding to be prolonged, and the degree of recovery is related to the extent of initial permeability: the degree of recovery is greater with higher initial permeability; vice versa. Especially the low-permeability reservoir with permeability of less than 1.0×10^-3 μm² is very sensitive to stress change,and the resulting solid-liquid coupling effect is also very evident.The permeability of 1.0×10^-3 μm² can then be referred to as the limit of reservoir's stress sensitivity.From the viewpoint of oilfield development, the solid-liquid coupling effect will do more harm than good, so exploitation of low-permeability reservoirs should,as far as possible,be kept at the foramtion pressure to eliminate the influence of solid-liquid coupling. Except the factors of reservoir reformation and advanced development technique,the influence of solid-liquid coupling must also be considered while determining the low limit of productivity. It is suggested that the lower limit of productivity can be set at permeability ≥1.0×10^-3 μm² for reference while making strategic decision.

APPLICATION OF TEMPERATURE-RESISTANT AND SALT-RESISTANT TERNARY COPOLYMER(AMPS) IN HIGH-TEMPERATURE AND HIGH SALINITY RESERVOIRS

Wu Yingchuan

2003, 24(2):  167-170.  doi:10.11743/ogg20030213

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Ternary copolymer of AMPS/AM/AMC₁₄S has been synthesized by using the method of initiation polymerization. Experimental evaluation of indoor basic properties shows that the ternary copolymer has relatively good temperature-resistance and salt-resistance. Under the condition of 90℃ and brine water with salinity of 16×10⁴ mg/L, the viscosity of AMPS copolymer with concentration of 3 000 mg/L has a retention rate of 39.5% when the temperature of AMPS's solution rises from 30℃ to 90℃;and this solution,after a 90-day ageing test, the viscosity of AMPS copolymer has a retention rate of 61.3% under the same condition. However,the viscosity of ternary copolymer solution has not been obviously reduced with the increase of calcium ion concentration, while the viscosity of HPAM solution has been reduced by 89%.The ternary copolymer produced during trial production has been tested in the Wei 18-4 well group, when driving liquid of polymer has been transferred to water driving, developing pressure also changes from 15.4 MPa to 13.5 MPa, all the water cuts in 4 wells are 2.5 percent less than that before polymer being injected, and daily oil production has been increased,i.e. 2～4 t more than that before polymer being injected.

RESERVOIR CHARACTERISTICS IN CRETACEOUS BASHIJIQIKE FORMATION OUTCROP IN KUQA DEPRESSION

Hu Tao, Zhang Boqiao, Shu Zhiguo, Xia Wenjun

2003, 24(2):  171-174.  doi:10.11743/ogg20030214

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Reservoir rocks in Bashijiqike Fm outcrop are mostly of medium-grained lithic sandstone, dominated by the secondary dissolved micropores, strong-medium cementation, and weak-medium dissolved diagenetic facies. There are three genetic types of sand bodies in the Bashijiqike Fm, including sandy-braided channel sand bodies in the braided-delta plain in the 2nd member of Bashijiqike Fm, gravel-braided channel sand bodies in the braided-delta plain in the 1st member of Bashijiqike Fm,and fan delta reservoir sand bodies in the 3rd member of the Fm. On the basis of reservoir sand bodies' prototype-model, the reservoirs' architectural structure of Bashijiqike Fm outcrop can be divided into 6-grade hierarchical interfaces and 6-grade hierarchical entities, and the framework structure is of “building block” pattern. Single sand body occurs generally as tabular mass or wide lens.By contrasting with those in the subsurface,sand bodies in the outcrop area might be a little bit coarser,with higher cement content,and worse reservoir quality.The obvious differences between them might be caused by the epidiagenesis in the outcrop.

A NEW METHOD FOR STUDYING REMAINING OIL DISTRIBUTION──GREY ASSOCIATION ANALYSIS

Li Shengli, Yu Xinghe, Gao Xingjun, Wang Qingru, Liang Wei, Zhou Jin

2003, 24(2):  175-179.  doi:10.11743/ogg20030215

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Grey association analysis is a useful method with multiple parameters, i.e. through integrating many dynamic and static parameters,such as micro-facies,production well affecting factor, and etc, to predict remaining oil distribution.Moreover, through the modifying weight coefficient's calculating method with multiple major factors, it is much easier to evaluate remaining oil distribution according to different reservoirs' characteristics. This method can be divided into three steps: first, static geology study; second, dynamic production analysis; and third, synthesis valuation with grey association analysis. With grey association analysis, it is available to evaluate remaining oil distribution on HB reservoir in Xijiang 30-2 oilfield and is consistent with the actual production data.

APPLICATION OF AUTHIGENIC ILLITE K-AR DATING TO HYDROCARBON RESERVOIRING STUDY IN YANQI BASIN

Li Yonglin, Pu Cuiping, Nan Hongli, Song Jianhua

2003, 24(2):  180-183.  doi:10.11743/ogg20030216

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K-Ar dating results of authigenic illite in reservoirs indicate that charging time of gas in Bohu sag,Yanqi basin,might have roughly been divided into two phases:one is in 107.8～67.8 Ma,corresponding to Late Cretaceous;another is in 51.3～34.8 Ma,being equal to post-Eocene. Horizontally,various structures have different reservoiring stages.The reservoiring time has successively been later and later from south to north in the northern sag.The reservoiring in south and middle blocks of Baolang reservoir might have occurred in Late Cretaceous,and oil and gas have been generated in late Yanshan period;while reservoiring in north block of Baolang reservoir have occurred in Oligocene, and have been sourced from both the readjustment of primary reservoir in middle block and secondary hydrocarbon generation in Himalayan period.The reservoiring time in the southern sag might have been in later stage of Late Cretaceous.Vertically,the K-Ar dating indicates that the reservoirs in the same structural belt are younger with less buried depth,which mean that oil and gas have migrated upwards,and shallower structures have been charged from the readjustment of deeper structures.

APPLICATION OF SOURCE-SIMILAR FABRIC ANOMALY ANALYSIS IN PETROLEUM GEOCHEMICAL EXPLORATION

Liu Yunli

2003, 24(2):  184-186,190.  doi:10.11743/ogg20030217

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Source-similar fabric anomaly is used to express the comprehensive characteristics that can reflect the fabric being similar to those of light hydrocarbon component in subsurface reservoirs,which is usually necessary to have exact meanings in geology and geochemistry and reflects the change of hydrocarbon fabrics,so as to indicate more definitely the existence and location of oil/gas reservoirs.By using entropy-value analysis, Marsh distance analysis and clustering analysis,various indexes or their composite characteristics in the study area can be calculated,and the range of favorable numerical values will be determined, anomaly parameters can be chosen,and prospective areas can then be delineated.The method of source-similar fabric anomaly has been proved to have obviously more advantages than the anomaly analysis of total hydrocarbon concentration, which will have good prospects in the future.

APPLICATION OF SR ISOTOPE TO SEDIMENTARY ENVIRONMENT ANALYSIS

Shi Zhongsheng, Chen Kaiyuan, He Hujun, Shi Jun, Liu Baojun, Liu Gang

2003, 24(2):  187-190.  doi:10.11743/ogg20030218

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With indicating significance of geochemical characteristics of Sr isotope in sedimentary environment, characteristics of Sr isotope in Eogene saline deposits in Dongpu depression have been studied. Analysis result indicates that the value of ⁸⁷Sr/⁸⁶Sr are generally higher and exceed that in the sea water,so it is inferred that Dongpu salt lake might have been an inland brine lake,and the Sr isotope in the lake water might have mainly been controlled by the silicon-aluminium rock with high ⁸⁷Sr/⁸⁶Sr(0.720?0.005)value. Variation of Sr isotope curve may reflect the climate change, and the Eogene paleo-climate in Dongpu depression has also been analyzed with this feature.It is preliminarily suggested that the climate might have been semiarid and semihumid from Es₄^up to Es₃^up,and it became more arid from Es₃^up to Es₁.

COMPREHENSIVE EVALUATION OF SEALING CAPACITY OF CLAYSTONE IN DEEP GAS RESERVOIR──AN EXAMPLE OF Es₃ CLAYSTONE CAPROCK IN DUQIAOBAI AREA IN DONGPU DEPRESSION

Tan Yuming, Ren Laiyi, Zhang Hong'an, Zhang Jinbao, Xu Juzhen, Jin Zhenhua

2003, 24(2):  191-195.  doi:10.11743/ogg20030219

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The result from the experimental analyses of the 3rd member of Shahejie Fm (Es₃) claystone's sealing capacity in the deep gas pools in Duqiaobai area in Dongpu depression shows that the variation in porosity has been controlled by depth and horizons, whereas the permeability has close relation with depth, but it is almost not affected by the horizons, and doesn't have obvious relation with porosity and other related parameters, too. The breakthrough pressure is getting greater with the increase of depth, but this trend is not very prominent. There is a close relation between the breakthrough pressure and the horizons, among which, the Es₃⁴ has the biggest breakthrough pressure, then the Es₃² comes next, and the Es₃³ has relatively low breakthrough pressure.For the sake of evaluating the sealing capacity of cap rock accurately, porosity, permeability, displacement pressure, and pore diameter have been selected as the indexes of cap rock evaluation, and weight coefficients of 0.1,0.3,0.5,and 0.1 have respectively been given to them based on their importance,so as to determine the evaluation standards caprocks of deep gas pools in Dongpu depression: when the weight coefficient is larger than 0.8,the cap rock belongs to I type, with good sealing capacity; if it is in the range of 0.6～0.8, the cap rock belongs to type Ⅱ, having moderate sealing capacity; when it is in the range of 0.5～0.55,the cap rock belongs to type Ⅲ; and if it is in the range of 0.3～0.45,the cap rock belongs to type IV; when it is less than 0.3, it is then of non-caprock.

APPLICATION OF SEISMIC ATTRIBUTE PARAMETERS TO PREDICTION OF GAS RESERVOIR IN SHENGTUO OILFIELD

Shi Wanzhong, Chen Kaiyuan, Chen Xinjun, Zhu Hongtao

2003, 24(2):  196-198.  doi:10.11743/ogg20030220

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On the basis of gas reservoirs in Shengtuo oilfield being characterized by shallow reservoir distribution, simple structure and good-quality seismic data,three parameters,amplitude, instantaneous frequency and instantaneous phase have been used and integrating with drilling data to analyze the corresponding relation between these parameters and the known gas-bearing formations.The gas-bearing interval showed while drilling has a strong amplitude in the amplitude profile, a low frequency in the instantaneous frequency profile, and phase reversal in the instantaneous phase profile. By using these characteristics,the southeastern part of Shengtuo oilfield has been predicted to be a favourable gas reservoir area.