Table of Content

28 June 2013, Volume 34 Issue 3

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Characteristics and controlling factors of natural gas migration and accumulation in the Upper Jurassic Penglaizhen Formation of Chengdu Sag

Tang Yu, Lü Zhengxiang, Ye Sujuan, Meng Wanbin

2013, 34(3):  281-287.  doi:10.11743/ogg20130301

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The Upper Jurassic Penglaizhen Formation gas pool in Chengdu sag is a secondary gas pool with its gas being sourced from the Upper Triassic source rocks over 3 km beneath the reservoirs.Due to the long vertical distance between the reservoir and source rocks,the gas migration path and mechanism are assumed to be of particular importance.The gas-bearing sandstones are widely distributed in the Penglaizhen Formation and have great heterogeneity,thus study of the principal controlling factors on gas accumulation is critical to understanding its heterogeneity.Analyses of gas sources,original gas compositions,isotopic compositions,dry coefficient,and iC₄/nC₄ demonstrate that the major hydrocarbon migration pathways are source-rock-connected faults and permeable carrier beds through which gas is capable of migrating with high efficiency.Hydrocarbon exploration and exploitation indicate that source-rock-rooted faults and good-quality reservoirs.The existence of source rock-rooted faults is the indispensable condition for gas accumulation in the Penglaizhen Fm in Chengdu sag.The rational combination between the source rock-rooted faults and reservoirs and the poroperm charateristics of reservoirs further influence the enrichment of gas.Gas is highly enriched in the downdip areas where the sandstones have good poroperm characteristics and are connected with or near to the source rock-rooted faults.The study results are valuable for gas exploration and development and can increase success rate in drilling prolific and commercial wells.

Microscopic occurrence of oil in tight sandstones and its relation with oil sources—a case study from the Upper Triassic Yanchang Formation, Ordos Basin

Niu Xiaobing, Feng Shengbin, Liu Fei, Wang Chengyu, Zheng Qinghua, Yang Xiao, You Yuan

2013, 34(3):  288-293.  doi:10.11743/ogg20130302

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Identifying pore distribution of tight reservoirs and the microscopic occurrence of oil in pores of different scales is critical to understand the characteristics of tight oil.In this study,tight sandstone samples from Yanchang Formation,Ordos Basin,were investigated through Nuclear Magnetic Resonance (NMR) experiment.Nano-scale pores are common in the tight sand of Yanchang Fm and macro-scale,medium-scale,small-scale,micro-scale and nano-scale pores co-exist in the samples.The microscopic occurrence of oil in multiple-scale pores are compared between near-source reservoir and far-source reservoir.In near-source reservoirs,oil exists in all kinds of pores and the micro-pores and nano-pores are saturated with oil.In contrast,in far-source reservoirs,oil selectively occur in macro-scale and medium-scale pores and nano-pores contains no oil.The abnormal pressure caused by hydrocarbon-generation in Chang 7 layer is believed to be the main controlling factor for different occurrences of oil in multi-scale pores in tight reservoir.This provides a theoretical basis for understanding the distribution of tight oil reservoir.It is concluded that the upper Chang 8,the Chang 7 and lower Chang 6 reservoirs within the distribution area of Chang 7 source rock are the main potential targets for tight oil exploration in the future.

Geologic conditions for hydrocarbon accumulation in Chang-9 oil reservoir of the Yanchang Formation,Ordos Basin

Shi Baohong, Yao Jingli, Zhang Yan, Zhang Lei, Yang Yajuan, Li Hui

2013, 34(3):  294-300.  doi:10.11743/ogg20130303

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This paper analyzes the geologic conditions of hydrocarbon accumulation in the Chang-9 reservoir of Ordos Basin.The oil in the Chang-9 reservoir is mixed oil sourced from both the overlying Chang-7 and Chang-9 itself.However,oil in the Chang-9 reservoir in Zhidan area is only sourced from Chang-9 source rocks,without any contribution from the Chang-7 source rocks.The oil mainly occurs in the first segment of Chang-9 oil reservoir.Reservoirs are mainly of distributary channel sandstone of braided river delta plain facies and underwater distributary channel sand of delta front facies,with some turbidites of semi-deep lake facies.Lithology of Chang-9 reservoir is dominated by lithic arkose with well-developed primary inter-granular pores,low porosity and permeability.The physical properties of the Chang-9 oil reservoirs show great lateral variation.In Jiyuan area,the sandstone feature in coarse grain,well-developed inter-granular pores and good poroperm characteristics.In contrast,in Luochuan area,the carbonate cemented sandstone has poor poroperm characteristics due to poor development of pores.According to the relationship between source rocks and reservoirs,two source rock-reservoir combination patterns were identified in Chang-9 oil reservoirs,i.e."upper sourcing" pattern and "indigenously sourcing" pattern.Jiyuan area is the most favorable for further exploration based on comprehensive analysis.

Distribution and sealing effectiveness of Middle-Lower Cambrian evaporite cap rocks in the southeastern Sichuan Basin

Xu Mei'e, Zhang Rongqiang, Peng Yongmin, Chen Xia, Feng Jufang

2013, 34(3):  301-306.  doi:10.11743/ogg20130304

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Based on correlation of outcrop section with wellbore pofile and in combination with seismic inversion under the constraint of broadband,this paper analyzed the distribution of the Middle-Lower Cambrian evaporite cap rocks in the southeast of Sichuan Basin.It also discussed the sealing effectiveness of the evaporite cap rocks based on study of the tectonic evolution of Sichuan Basin and its periphery.In the southeastern Sichuan Basin,the Middle-lower Cambrian evapo-rites are widely distributed in northeast direction with two thickness centers,and the distribution of evaporites coincides perfectly with the trap distribution.During the Caledonian and Indosinian period,sealing capacity of the Middle-Lower Cambrian evaporites was not destroyed,so they could serve as effective seals for the Sinian ancient oil (gas) accumulations.Whereas,their sealing capacity was lost during the Yanshan and Himalayan period,thus the ancient oil (gas) accumulations in the Dingshan-Lingtanchang area were not effectively preserved.As the Middle-Lower Cambrian evaporite cap rocks to the west of Qiyueshan fault were not destroyed completely post-Indosinian movement,they could effectively seal the presalt Sinian oil (gas) accumulation,thus this area is favorable for petroleum exploration in the pre-salt strata in southeastern Sichuan Basin.

Comprehensive evaluation on the sealing capability of cap rocks in tight sandstone gasfield—a case study from Guang’an gasfield in the Sichuan Basin

Shi Jijian, Li Lili, Lü Yanfang, Yang Jun, Li Shouying

2013, 34(3):  307-314.  doi:10.11743/ogg20130305

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In this paper,we chose several parameters that are closely related with sealing capacity of cap rock,such as cap rock thickness,displacement pressure,pressure coefficient,damage of fault to cap rock and vertical sealing ability.In combination with the concept of sealing effectiveness of cap rock,we proposed a comprehensive evaluation method of cap rock sealing capability.Based on statistics of reserve abundance and cap rock attributes of large tight sandstone gasfields in China,we took the lower limit of each cap rock evaluation parameter necessary for the formation of large gasfield with high reserve abundance as its homogenization standard value.Case study of the regional cap rock of the 5th Member of Xujiahe Formation in Guang'an gas field shows that the cap rock thickness is 30-200 m,displacement pressure is 5.5-9.5 MPa,the pressure coefficient is 1.05-1.50,the fault activity is strong,vertical sealing capacity of the fault is poor,and the sealing effectiveness of cap rock is good.Calculation with the comprehensive evaluation formula obtains a composite sealing capacity evaluation index in the range of 0.04-0.24,indicating that the cap rock of the 5th Member of Xujiahe Formation is capable of sealing gas in reservoirs with ultra-low reserve abundance.The index is high in the west but low in the east as a whole.The play fairways predicted by this method basically coincide with the present exploration results of the 5^th Member in the Xujiahe Formation.

Heavy oil accumulation characteristics of the Orinoco heavy oil belt

Liu Yaming, Xie Yinfu, Ma Zhongzhen, Zhou Yubing, Wang Dandan

2013, 34(3):  315-322.  doi:10.11743/ogg20130306

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Based on the theory of oil and gas accumulation,the heavy oil accumulation conditions and characteristics of the Orinoco heavy oil belt were analyzed,and the exploration direction was pointed out.The Orinoco heavy oil belt is situated in the foreland slope region of low relief.Tectonic activity is weak and several small normal faults are developed in this region.The Upper Cretaceous Guayuta Group neritic shale is the main source rock,which features in large thickness,high abundance of organic matter and large hydrocarbon generation potential.The main reservoirs are sandstones of delta facies in the Miocene Oficina Formation and Oligocene Merecure Formation.They are characterized by large sheet-like distribution,stable thickness in East-West direction but decreasing thickness southwards,shallow buried depth,low degree of cementation,high porosity and high permeability,thus their reservoir properties are supreme.There are multiple seals such as regional cap rocks and bitumen overlying the reservoir,mudstone layers between reservoirs,and the underlying pre-Cretaceous basement at the side of reservoirs.The main trap type is lithologic stratigraphic trap.Fault,unconformity and connected sandstones are the major hydrocarbon migration pathways.Oil became viscose due to biodegradation during the long distance migration in the late Miocene and large-scale accumulation in Pliocene-Pleistocene.The accumulation of heavy oil has the characteristics of excellent source-reservoir-seal combination,long migration distance and strong viscosifying action.The accumulation model of heavy oil is long distance migration and biodegradation,large scale centralized accumulation in shallow reservoirs.Resources potential is huge in the Orinoco heavy oil belt.The Oficina formation is the key exploration target.The western part of the Orinoco heavy oil belt is the major exploration domain.Stratigraphic traps are the key trap type.

Distribution and significance of high-resistivity carbonates of Ordovician Yingshan Formation of northern slope of Tazhong area,Tarim Basin

Hua Xiaoli, Luo Chunshu, Lü Xiuxiang, Yu Hongfeng, Wang Xiang, Zhang Jinhui, Sun Xijia, Hua Qiao

2013, 34(3):  323-331.  doi:10.11743/ogg20130307

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The Ordovician oil reservoirs in Tarim Basin are highly heterogeneous with a complex distribution pattern of fluids.Drilling data,mud logging and well logging data were integrated to analyze the lithology and thickness of high-resistivity layers in the Yingshan Formation.Well tie profiles of each wellblock and inner-outer zones based on single well histograms were generated and the distribution patterns of these high-resistivity carbonates were mapped.The lithology of high resistivity layers in the Yingshan Formation is mainly micritic limestone.They occur as layered bright yellow on imaging logs and show spatial distribution featuring in "lateral unstableness and vertical superimposition".Examination of rock mineral cast thin sections of high resistivity layers indicates that the high resistivity layers were formed mainly by mechanical-chemical filling and selective dissolution by atmospheric water.In addition,the thickness of high resistivity layer correlate well with properties of oil in the underlying reservoir,daily oil/gas production and gas/oil ratio.With increasing thickness of high resistivity layer,daily oil/gas production and gas/oil ratio increase,while density and viscosity of oil decrease,suggesting that high resistivity layers could have a certain control on underlying oil and gas distribution.The high resistivity layers in the Yingshan Formation could act as a set or multiple sets of subtle local seals for the underlying reservoir.

Material responses and accumulation patterns in cyclic sediment records of continental clastic rocks：taking the Paleogene Kongdian Formation of Wangjiagang area in Jiyang Depression as an example

Tan Xianfeng, Tian Jingchun, Huang Jianhong, Lin Xiaobing, Ma Jianwei

2013, 34(3):  332-341.  doi:10.11743/ogg20130308

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Cyclic sediment records contain rich geological information.Taking the Paleogene Kongdian Formation in Wangjiagang area in Jiyang Depression as an example,this paper studied the characteristics of material response in the cyclic sediment records of continental clastic rocks.Three kinds of cycles including color,lithology and grain size were identified in the continental clastic deposits accumulated during the gradual shrinking of lake level in Wangjiagang area and the genetic mechanism of these cycles is intermittent fluctuation of the Salt Lake level.Vertically from gray to red strata,the mineral cycle features in progressively increasing contents of quartz and potassium feldspar,decreasing contents of plagioclasite and calcite,and increasing content of anhydrite.The mineral cycles and color cycles have a good coupling relationship.The cycles also have a certain coupling relationship with element enrichment.Vertically,the contents of major elements such as Al,Ca,Fe and Mg have an increasing trend;while the contents of trace element Sr,Ba,Ga and Co have an increasing trend.The cycles also have a certain coupling relationship with element ratios,especially Fe/Mn and V/Ni ratios,which show multiple cycles.It is confirmed that sedimentary cycles of the continental clastic rocks in Wangjiagang area have relatively significant coupling relationship with mineral contents and element enrichment,and the former directly control the latter.Late diagenetic fluid modification influences material response and coupling patterns of the cycles through material exchange.

New evidences of reefs,shoals and sedimentary facies of the Changxing Formation in Western Hubei and Eastern Chongqing area

Wang Bijn, Zhang Shiwan, Guo Zhanfeng, Chen Miankun, Liu Xinmin

2013, 34(3):  342-348.  doi:10.11743/ogg20130309

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Platform margin facies belts surrounding Kaijiang-Liangping continental shelf are favorable for the development of large gas field.The distribution of the continental shelf controls the distribution of reef and shoal facies belts.In order to accurately map the distribution of reef and shoal facies belts,the core,cutting and thin section data were integrated to systematically analyze the grain size,fossil composition and structure types.Moreover,3D seismic data were used to predict the appearance and distribution of the reefs and shoals,and the sedimentary faces in Changxing Formation were mapped by integrating drilling and outcrops data.The nearly NS-trending dome-shaped Jianzhuxi bioherm is of typical platform margin facies.The shoal-facies dolomite at the bottom of the bioherm is large in lateral distribution and its major part is located in the east of the bioherm and is closely interconnected with the platform.The Kaijiang-Liangping continental shelf extends southeastwards across the western part of the Jianzhuxi bioherm and is connected with to West Hubei marine basin.The Jianzhuxi bioherm is located in the same platform margin facies belts with that of the bioherms in Puguang areas.

Sedimentary characteristics of Yingcheng Formation in Sujiatun area, Lishu Rift in Songliao Basin

Yang Tebo, Wang Hongyu, Fan Tailiang, Liu Zhenhua, Hao Yuejuan, Wei Yuan, Yang Fan

2013, 34(3):  349-356.  doi:10.11743/ogg20130310

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The Yingcheng Formation in Sujiatun area,Lishu Rift in Songliao Basin,has good conditions for the formation of petroleum reservoirs.However,the level of research is low in this area.The paper is to identify favorable reservoir facies belt through study of sedimentary microfacies and sandstone reservoir conditions.The theories of sedimentoloy and high-resolution sequence stratigraphy were applied and the cores,mud logging,well logging,seismic data and palaeogeomorphology data were integrated.The study revealed that lacustrine and braided river delta sedimentary facies are predominant in the study area.Furthermore,eight sedimentary microfacies were identified,including distributary channel,underwater distributary channel,underwater interdistributary,month bar,distal bar,sheet-like sand,mudflats and bank bars.And the main characteristics of sandstones of sedimentary microfacies are described.The Yingcheng Formation was divided into 4 Members,6 fourth-order sequences and 7 sand groups.The sedimentary facies distribution and their temporal and spatial evolution of each sand group(SG) were discussed.The transgressive surface to maximum lake flooding surface occurred at the end of deposition of the Ying-1 Member (SG2),and the overlying SG3 is the most favorable reservoir.Analyses of plain distribution of sedimentary facies and reservoir reveal two main braided channels with good stacked distributary channel sand bodies and reservoir properties.The main braided channels in combination with late nose structure are the most favorable areas for the development of structural-lithologic traps and lithology traps.

Fuzzy mathematics-based reservoir evaluation in the southeastern Pre-Caspian Basin

Zhu Wei, Gu Shaoqiu, Cao Zijian, Zhang Guoyi

2013, 34(3):  357-362.  doi:10.11743/ogg20130311

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Kazakhstan Pre-Caspian Basin is a craton marginal foreland basin located in the southeast edge of East European Platform and is one of the main petroliferous regions in Caspian Sea.Terrigenous clastic rocks were widely developed during the Triassic-Jurassic in southeastern Pre-Caspian Basin.The reservoirs are dominated by sandstone and siltstone of shallow marine shelf facies,shoals facies and delta facies.The poroperm characteristics of the reservoirs are medium porosity and moderate permeability as a whole.The well logging interpretation shows that the reservoirs physical properties and pore texture are of strong heterogeneity.Based on fuzzy mathematics evaluation,this paper optimized the geological factors through multiple regression analysis and smallest secondary multiplication,recognized porosity,permeability,oil saturation and sand thickness as the key geological factors,and established fuzzy mathematical model.The new model overcomes the complexity and subjectivity caused by various uncertainties that are common in traditional reservoir evaluation.Multiple model comparison reveals that the favorable reservoirs in this area are J₂Ⅱ and TⅡ.

Tectonic evolution and hydrocarbon accumulation in the Solimoes Basin,Brazil

Xiong Liping, Li Jun, Wu Changwu, Li Songyang

2013, 34(3):  363-369.  doi:10.11743/ogg20130312

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Onshore Solimoes Basin in Brazil is an intra-cratonic basin,being very special in its depositional succession and its hydrocarbon accumulation mechanisms.This paper focuses on summarization of the formation and evolution of the basin,its structure and depositional characteristics and its key petroleum geologic features,as well as analysis of hydrocarbon accumulation mechanism and the main controlling factor for accumulations.The basin has experienced multiple tectonic movements,including multiple subsidence during the Paleozoic,a shear stress dominated Mesozoic age,and flexure subsidence in Cenozoic.The deformation style features in change from early normal faulting to later inversion and thrusting.The deposits in the basin are mainly of Paleozoic age,and are complicated in lithologic assemblages,consisting of siliciclastics,carbonates,evaporites,glacial deposits,igneous,etc.All the sequences are in unconformable contacts.The major source rock is the Upper Devonian shale,with high TOC value and high degree of thermal maturity.The main reservoir is the Carboniferous Jurua sandstone.The main seal interval is the Carboniferous-Permian evaporites,which is good in sealing capacity.The source rock-reservoir-seal combination is favorable.The basin has well developed structure traps,which are mainly anticlines and faulted anticlines.The petroleum geology of the basin is special in that the shallowly buried source rocks have entered gas window due to igneous intrusion.Eolian sands have good reservoir quality,with well preserved porosity due to its shallow burial depth.The unconformities and reactivated basement-rooted faults serve as the major pathways for hydrocarbon migration.The accumulation of oil and gas is controlled by the fault-related structrual traps.

New ideas about the evolution of Caohu sag in the northern Tarim Basin and its significance for petroleum geology

Yao Zewei, He Guangyu, Zheng Xiaoli, Qi Lixin, Zhang Hong'an, Yun Lu, Lin Lu, Wang Wenxia

2013, 34(3):  370-375.  doi:10.11743/ogg20130313

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The evolution of Caohu sag in northern Tarim Basin is discussed in this paper based on geological interpretation of two-dimensional seismic profiles and analysis of drilling data.We present new ideas about the evolution of Caohu sag since Paleozoic.The time and mechanism of formation of the eastern and western slopes of Caohu sag are apparently different.In the western side of the sag,the Middle-Upper Ordovician show distinct overlapping characteristics from east to west,indicating that the western slope of Caohu sag was developed mainly in the Middle Caledonian as the result of the subsiding of Caohu area and the uplifting of Akekule Uplift under the continuous regional compression.The western slope has the characteristics of depositional sag slope.While in the eastern side of the sag,the Silurian-Ordovician were strongly uplifted and eroded and underlie unconformably the Upper Devonian-Carboniferous,which in turn underlie unconformably the Triassic.This demonstrates that the eastern slope was developed in the Late Caledonian as well as the Early and Late Hercynian as the result of the intense tectonic deformation,with the Late Hercynian being the dominant.The eastern slope shows the characteristics of structural sag slope.The western side of Caohu sag is favorable for the development of Late Ordovician karst stratigraphic traps,while the eastern side is favorable for the development of overlapped lithologic traps in the Silurian,Carboniferous and Triassic,unconformity stratigraphic traps in the Upper-Middle Ordovician,as well as the karst stratigraphic traps in the Lower Ordovician.They are the major potential exploration targets in the future.

Characteristics of deep-rooted faults and their geological significances in Dachuanzhong area,Sichuan Basin

Yin Jifeng, Gu Zhidong, Li Qiufen

2013, 34(3):  376-382.  doi:10.11743/ogg20130314

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To research the deep-rooted fault system in Dachuanzhong area of Sichuan Basin,2D seismic data of 21 000 km and 3D seismic data of 3 000 km² were interpreted applying the integrated seismic interpretation technique.Three characteristics of the deep-rooted faults were revealed.The deep-rooted faults control the tectonic deformation of the seals.They cut downward into the basement and upward into the Feixianguan Formation and are associated with flower-shaped faults.The deep faults and the shallow ones have distinct characteristics,with the former being high in angle and dominated by strike-slip faults while the latter being relatively low in angle and dominated by reverse faults.A total of 172 faults were interpreted in Dachuanzhong area and their lateral extensions range from 3 to 79 km.The areal distribution of deep faults shows distinct zonation.The first zone is Weiyuan-Ziyang-Suining-Dazu area where the faults are NE-trending or nearly EW-trending.The second is Bazhong-Yilong-Guang'an area where the faults are NW-trending or nearly EW-trending.The third is Pingchang-Dazhou area where the faults are SN-trending.The deep faults control the sedimentary faces belts and the distribution of favorable sedimentary body,communicate the low porosity and tight reservoirs,effectively improve the reservoir properties and increase oil and gas production capacity.They also control the formation of local structural traps and can act as effective migration pathways for hydrocarbons from source rocks to reservoirs and control hydrocarbon accumulation of allogenic source systems.

Three-dimensional geological modeling of fractured-vuggy carbonate reservoirs：a case from the Ordovician reservoirs in Tahe-Ⅳ block,Tahe oilfield

Hu Xiangyang, Li Yang, Quan Lianshun, Kong Qingying, Wang Ying, Lv Xinrui

2013, 34(3):  383-387.  doi:10.11743/ogg20130315

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Reservoir spaces of fractured-vuggy carbonates mainly,include large caverns,dissolved pores and fractures,which are varied in scale,irregular in shapes and discontinuous in distribution.There still have no effective geological modeling method for quantitative descriptions of 3D reservoir space distributions in fractured-vuggy carbonate reservoirs.In this paper,taking Tahe fractured-vuggy carbonate reservoir as an example,we put forward a 3D geological modeling method of fractured-vuggy reservoir under the constraint of multiple geological factors,i.e.two-step modeling under the control of ancient karst development pattern.In the first step,4 single-type reservoir models were established.After large cavens and large-scale fractures were identified by using seismic data,a discrete large cavern model and a discrete large-scale fracture model were established first with deterministic modeling method.Then,under the constraint of karst facies and based on development probability volumes of dissolved pores and interwell fractures,a dissolved pore model and a discrete small-scale fracture model were established by using the stochastic multi-attribute coordinated modeling method.In the second step,the 4 single-type reservoir models were merged into a 3D multiscale discrete geological model of fractured-vuggy carbonate reservoirs by using the diadochic assignment algorithm.The final model can quantitatively describe the 3D distribution of the fractured-vuggy carbonate reservoirs,and provide geological foundation for oilfield development.

Application of geosteering technology in the developent of Sulige gas field—case studies of the Su10 and Su53 blocks

Tang Qinxi

2013, 34(3):  388-393.  doi:10.11743/ogg20130316

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Sulige gas field is a typical lithology-controlled gas reservoir with low permeability,low pressure,and low abundance.Development of this gas field faces varisou challenges,such as low degree of well control in drilling area,uncertainty of micro structure in some area,strong heterogeneity of reservoir and unstable sand distribution,making horizontal well drilling being highly risky.To guarantee drilling success and increase the ratio of target penetration,we first performed high-resolution stratigraphic correlation based on proper selection of marker beds,and then carried out detailed studies of the micro structure,deposition and reservoir distribution.Based on seismic prediction of gas-bearing properties and under the constraints of structure and sedimentary facies,we built a delicate 3D geologic model with fine geologic modeling technique and micro structure forecasting technology.With this model,we mapped the reservoir distribution and micro structures before drilling operation.During drilling operation,these study results can be integrated with the drilling,mud logging,MWD data to predict the change of subsurface microstructures and rapid identification of bottom hole lithology,which in turn can be used in the real-time modification of geologic model and drilling design.

New nonlinear correction method of oil-water relative permeability curves and their application

Yang Chao, Li Yanlan, Xu Bingxiang, Zhao Qingbing

2013, 34(3):  394-399.  doi:10.11743/ogg20130317

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The relative permeability curves from laboratory measurement only represent the flow behavious of core sample and commonly do not accord with the real flow behaviors,thus they need to be corrected through history matching.However,the process of history matching is time-consuming and labor-intensive.The current study introduces a new method to correct the relative permeability curves based on the nonlinear optimization theory and accurate experimental endpoint.Based on the assumption that the relative permeability satisfies the exponential function,the theoretical water cut-recovery curve (f_w-R) is fitted to the actual fw-R curve to obtain relative permeability curves.The new method requires fewer parameters and is simple and faster.Application of the new method to Turpan-Hami Oilfield WENXI 3 block shows that the the corrected relative permeability curves fit better with the calculated relative permeability through history matching,indicating this correction method is feasible.The corrected relative permeability curves are representative and in good shape.The theoretical water cut-recovery curves obtained by using the new method are in good accordance with the real curves.

Structure modeling-constrained seismic inversion technology—a case study from Nanba area in Saertu oilfield,Daqing

Li Zhandong, Li Ji, Li Yang, Chen Dayou, Zhao Wei

2013, 34(3):  400-406.  doi:10.11743/ogg20130318

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This paper introduces structure modeling-constrained seismic inversion technique.It has four key components,i.e.well-seismic integrated small scale structure interpretation,rational design of geologic framework,multi-scale grid design and curve homogenization.Take SⅡ7-12 sedimentary units in Nanba area of Daqing Saertu oilfield as an example,the article summarizes the advantages of structure modeling-constrained seismic inversion over seismic inversion without structure modeling.①It can improve the accuracy of sandbody identification,especially channel sand and realize well-seismic integrated correction of sedimentary microfacies through "defining facies in wells and shapes on slices";②It can reveal the contact relationship between major thick reservoir and the main sand body,and refine the prediction of sandbodies near faults,so as to guide remaining oil potential tapping.It is concluded that structure modeling-constrained seismic inversion can lower the uncertainty of seismic inversion and is of great significance to oilfield development adjustment in later stage.

3D seismic interpretation technology and its application in reservoir description—an case from X56 block of Xingshugang oilfield,Songliao Basin

Wang Yanhui, Jiang Yan, Zhang Xiuli, Li Cao, Piao Changyong, Song Lijun, Gao Peng

2013, 34(3):  407-412.  doi:10.11743/ogg20130319

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Well-seismic integrated reservoir characterization of Daqing Changyuan oilfield at late high water cut development stage faces the challenges of small scale of description target,high requirement for predication accuracy and dense well pattern.Taking Block X56 of Xingshugang oilfield in the Songliao Basin as an example,we developed a set of technologies consisting of well-seismic integrated structure interpretation,fault identification and reservoir prediction by utilizing 3D seismic data and fine geologic study results.The capacity-dimension fractal technology is applied to recognize small faults with throw of about 5 m,solving problems of small faults identification between wells.The plane combination characteristics and extensions of faults are defined and the relationship between low amplitude structure and oil-gas distribution is determined by using well-seismic integrated structure interpretation technology.Reservoir sandbody thickness in the 1^st member of Putaohua Formation is mapped and the sandbody connectivity between wells is analyzed with the stochastic inversion technology.The coincidence rate of prediction of sandbodies with thicknes above 2 meters is more than 75%.On this basis,sedimentary microfacies map drawn only by borehole data is further revised,and the planar distribution features of channel sandbody are characterized.The well-seismic integrated 3D seismic interpretation technology has been applied in several blocks of Changyuan oilfield and the results are satisfactory.

Fuzzy neural network-based tight sandstone reservoir inversion—a case study from the Denglouku Formation in Changling 1 gas field

Ai Ning, Tang Yong, Yang Wenlong, Shen Chuanbo, Wang Yanqing, Huang Wenfang, Shang Ting

2013, 34(3):  413-420.  doi:10.11743/ogg20130320

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Fuzzy neural network reservoir inversion can avoid the integration of data of different types and scales and well preserve the data integrity,making it possible to reveal both the overall variation tendency and the local detailed features.In view of the rapid facies change and poor lateral continuity of the Denglouku Formation sandstone in the Changling1 gas field,we integrated various data including seismic,well logging,drilling and well testing and performed inversion of the sandstone thickness and porosity characters by using the fuzzy neural network theory.The following results were obtained.①The areal distributions of the Denglouku Formation sandstones in the Changling1 gas field varies greatly,with the thicker sandtone occurring mainly in areas along the Changshen 103,Changshen 1-3,Changshen 1-1 wells and the Changshen 2 well.The thickness of sandstone decreases progressively in northeast direction.The thickness of D3 layer near in the Changshen 103 well is up to 33.2m.②The major D3 and D4 pay zones in the Denglouku Formation have a relatively low porosity,averaging at only about 5%.The sandbodies with relatively high porosity(>9%)only occur in area around the Changshen 1 well.The Denglouku Formation is tight as a whole.③Comparison of the inversion results with the actual test data shows that the error of sandstone thickness is within 2.5 m and the error of the porosity is under 0.49%,indicating a high reliability of the inversion results.It is concluded that fuzzy neural network-based inversion of tight sandstone reservoirs can well reveal sandstone distribution and reservoir properties.