Lithologic Reservoirs

In order to deepen the fine exploration of Jurassic-Paleogene lithologic reservoirs in the oil-rich zones of the western Turpan Depression of Turpan-Kumul Basin,based on well-seismic matching fourth-order sequence framework establishment,systemically fine depositional system was deeply studied and spatial distribution was depicted. The result shows that establishment of the fourth-order sequence framework based on well-seismic matching is the maximum study unit for understanding fine depositional system,the two-step horizon-reservoir calibration is a key step for the matching analysis of logging calibration to seismic,and the lateral variation analysis of seismic reflection within isochronous sequence framework is core for the deep understanding of contacting and evolution of different sedimentary bodies. It is considered that the differential tectonic activities of Tianshan orogenic belt in the north and the Jueluotage orogenic belt in the south are main controlling factors for the lateral migration of depositional system,the underwater distributary channel sandstone within braided river delta front is the main type of reservoir,and lateral up-dipping and pinching out sand bodies attaching to paleo-topographic setting are favorable for extend lithologic reservoir exploration in Pubei,Putaogou,Shenquan and Shengnan areas of western Turpan Depression. Under the guidance of this understanding,good result has been achieved in the exploration of lithologic reservoirs in oil-rich zones of western Turpan Depression.

Accumulation conditions of Lower Paleozoic shale gas and its resources in northeastern Chongqing

JIANG Shengling, WANG Shengxiu, HONG Keyan, ZHU Liangliang, HU Xiaolan

2017, Vol.29(5): 11–18 Abstract ( 397 ) PDF (16409 KB) ( 537 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.002

In order to evaluate Paleozoic shale gas potential in northeastern Chongqing,based on the methods of filed outcrops survey,experimental test and mathematical statistics,the distribution,source rock and reservoir conditions of Lower Cambrian Shuijingtuo Formation and Upper Ordovician Wufeng-Longmaxi Formation were comprehensively analyzed. These shale rocks are characterized by high organic carbon content,high maturity, appropriate thickness and mainly type I kerogen. The results of field shale desorption show that the average gas content is 1.07 m3/t and 2.30 m3/t respectively. The siltstone and fine sandstone are easy for fracturing due to more quartz and other detrital components. These characteristics provide a favorable material basis and reservoir space for shale gas accumulation. Evaluated with conditional probability volume method,the shale gas resources of Shuijingtuo Formation and Wufeng-Longmaxi Formation are 0.42×1012m3 and 0.38×1012m3 respectively.Chengkou and Wuxi should be favorable areas for shale gas exploration in the northeastern Chongqing.

Geochemical characteristics and accumulation process of natural gas of Xujiahe Formation in southern Sichuan Basin

WANG Peng, SHEN Zhongmin, HE Chongkang, CHEN Gang, PAN Shulin, WANG Junze

2017, Vol.29(5): 19–27 Abstract ( 329 ) PDF (1677 KB) ( 693 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.003

Based on the geochemical analysis data,the characteristics,origin,hydrocarbon accumulation stages and process of natural gas of Xujiahe Formation in southern Sichuan Basin were analyzed. The results show that the drying coefficient of natural gas is greater than 0.85,the gas composition is mainly alkane,some contains H2S,which is the most remarkable feature of gas component of Xujiahe Formation in southern Sichuan Basin. The δ13C1,δ13C2 and δ13C3 values are -43.17‰ to -30.80‰,-33.81‰ to -24.90‰ and -28.65‰ to -22.70‰,respectively, which has the characteristics of positive carbon isotope. The analyses of carbon isotope and light hydrocarbon show that the natural gas is dominated by coal type gas,with some oil type gas existing. The coal type gas is mainly derived from coal-bearing source rocks of Xujiahe Formation,and the oil type gas is mainly derived from underlying marine strata. Base on the hydrocarbon accumulation history,there are mainly three stages of gas accumulation of Xujiahe Formation:(1)From the middle of Late Jurassic to Early Cretaceous,the coal-bearing source rocks of Xujiahe Formation generated a small amount of coal type gas,and then the gas accumulated in Xujiahe Formation.(2)During the Late Cretaceous,the coal-bearing source rocks of Xujiahe Formation generated a large amount of coal type gas,which then accumulated in Xujiahe Formation,and this stage is the most important accumulation period.(3)During Himalayan movement,some oil type gas derived from underlying strata and entered reservoir of Xujiahe Formation along the fault,the fluid charging is the origin of abnormal high temperature inclusions and higher H2S content.

Unconventional reservoir characteristics of Upper Permian Lucaogou Formation in southern margin of Junggar Basin

WANG Zhenghe, YU Qian

2017, Vol.29(5): 28–35 Abstract ( 330 ) PDF (11579 KB) ( 409 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.004

In order to deepen unconventional resources in Fukang-Urumqi zone,southern margin of Junggar Basin, based on field investigation,core observation,slice identification,sample testing,the unconventional reservoir characteristics of Upper Permian Lucaogou Formation were studied. The results show that unconventional reservoir was formed with tree types lithic facies,such as silt-based fine-grained sedimentary rock,clay-based finegrained sedimentary rocks and carbonates. The density of the carbonaceous fine-grained clastic rocks of upper, middle and lower member of Lucaogou Formation are 2.3-2.8 g/cm3,2.3-2.4 g/cm3,2.4-2.5 g/cm3 respectively. Their porosity is dominant with 0-2.0%,and permeability is dominant with 0-0.1mD,specific surface area is dominant with 0.1-0.5 cm2/g and 1.0-2.0 cm2/g. There is an apparent negative correlation between the density and TOC content of fine-grained clastic rock. It is considered that reservoirs space is mainly composed of nanometermicron micropores and two-phases structural fractures.

Geological controls on hydrocarbon accumulation of Chang 2 oil reservoir in Ordos Basin:a case from Renshan area, Yongning Oilfield

XIEWei, WANG Yanfeng, LI Hong

2017, Vol.29(5): 36–45 Abstract ( 411 ) PDF (27318 KB) ( 490 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.005

To discuss the geological controls on hydrocarbon accumulation of Chang 2 reservoirs in Yongning Oilfield, Ordos Basin,based on testing results of fifty core samples,ninety-well logging and oil production data, Chang 2 sedimentary microfacies and sandstone reservoir properties were analyzed.The Chang 2 sedimentary system is meandering fluvial,including channel sandbars,natural levees,and flood plains. Channel sandbars are mainly composed of fine to medium grained arkose and debris-arkosic sandstones.The grain sizes of channel sandstones are fining upward and appear "two-segments" in granulation curves. Chang 213 sandstones is the best reservoir with average porosity of 11.6%. The pores of Chang 213 reservoir are mainly residual intergranular pores and secondary dissolution pores. The cementation of chlorite coating,authigenic kaolinite and dissolution of feldspars and detritus are important diageneses in the sandstones. The crystallinity of authigenic illites ranges from 0.57 to 0.88, which indicates an "A stage" of burial middle digenetic stage. According to analysis of sedimentary facies,reservoir properties,regional structures and distributions of source rocks,the hydrocarbon accumulations of Chang 2 reservoirs are considered to be controlled by the local nose-like structures and the distance from source rocks. Southwestern Renshan area is potential for Chang 2 oil exploration.

Sedimentary facies of Neogene Sanya Formation in Changchang Sag, Qiongdongnan Basin

CAI Jia

2017, Vol.29(5): 46–54 Abstract ( 434 ) PDF (28996 KB) ( 200 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.006

The Changchang Sag is an important potential hydrocarbon exploration area in the eastern Qiongdongnan Basin. The Neogene Sanya Formation is a set of huge marine sandstone and mudstone stratum,and it can be divided into two members,all of which are important reservoirs. Based on data of logging,heavy minerals,paleontology and seismic sections,the provenance and the sedimentary system of Sanya Formation were analyzed. There are five kinds of sedimentary systems,including coastal,neritic,deltaic,bathyal and submarine fan system. Changchang Sag is a large marine depression in northern South China Sea during the sedimentary period of Sanya Formation. Under the coaction of paleogeomorphology and provenance input,a large submarine fan was formed,which is characterized by great thickness,good physical properties and basin axial distribution. The the largest high-quality sandstone in the huge submarine fan has unique advantage of reservoir accumulation in Changchang Sag. The structural-lithologic reservoirs are the most realistic prospects for deepwater hydrocarbon exploration in Qiongdongnan Basin,which is formed by its superposition with structure.

Source-sink analysis and sedimentary facies of the first member of Liushagang Formation in WZA area,Beibuwan Basin

ZHANG Hui, WU Zijin, ZHOUWei, YU Xinghe, SUN Le, HU Yong, TAN Chengpeng

2017, Vol.29(5): 55–66 Abstract ( 310 ) PDF (12377 KB) ( 434 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.007

There is no clear understanding of the types and distribution of sedimentary system of the first member of Liushagang Formation,which is major oil exploration target in WZA area of Weixinan Sag,Beibuwan Basin. It is difficult to correlation of continuity of sand bodies for further oil exploration. Combined with core,logging and seismic data,sedimentary system and sedimentary microfacies types were determined by the method of source-sink analysis. Three provenances,two types of sedimentary system and over ten types of sedimentary microfacies are identified in WZA area. The WZA is a catchment area around three provenances from direction of NWW,SWW and SEE. The meandering river delta sedimentary system developed in western and southern WZA, and turbidite fan sedimentary system developed in eastern WZA. The result is helpful for sweet reservoir characterization in oilfields of WZA,WZB,WZC,WZD and WZE.

Characteristics and distribution of Lower-Middle Ordovician grain bank in mid-eastern Tarim Basin

JIANG Haijian, CHEN Qianglu, QIAO Guilin, CAO Zicheng, CHU Chenglin

2017, Vol.29(5): 67–75 Abstract ( 328 ) PDF (35594 KB) ( 579 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.008

There are several new gas discoveries in Shuntuoguole area of mid-eastern Tarim Basin in recent years. So,it is necessary to re-understanding Lower-Middle Ordovician carbonate sedimentary facies for further exploration. Based on cores,thin sections,logging and seismic data,the characteristics,evolution and distribution of Lower-Middle Ordovician carbonate sedimentary facies were analyzed. Grain bank developed in variety of facies such as low-energy grain bank in the restricted platform,middle to high-energy grain bank facies and middle to lowenergy grain bank facies in open platform,bank facies and reef facies on margin of platform. In Yingshan period, grain bank facies widely developed in gentle slope and low-lying zone of intraplatform in Shuntuoguole area, which open platform grain bank increased local strata thickness. With rapid uprising of sea level,In Yijianfang period,open platform extended to whole Shuntuoguole area,grain bank migrated to Gucheng area and northern Shuntuoguole area. Platform is the key factor to develop grain bank,and the sea level change controls the process and pattern of grain bank.

Characteristics and controlling factors of low permeability reservoirs of the third member of Dongying Formation in northwestern margin of Bozhong Sag

PANG Xiaojun, DAI Liming, WANG Qingbin, LIU Shilei, FENG Chong

2017, Vol.29(5): 76–88 Abstract ( 314 ) PDF (71848 KB) ( 446 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.009

The third member of Dongying Formation(E3d3) developed typical fan delta glutenite reservoirs in the northwestern margin of Bozhong Sag,however,the understanding of diagenetic evolution and controlling factors of the reservoirs are unclear. Based on the data of cores,wall cores,cast thin slice,scanning electron microscope, physical properties,combined with the burial history and hydrocarbon filling history,the diagenetic evolution and its influence on physical properties of fan delta glutenite reservoirs of E3d3 were studied. The results show that the reservoirs are macroscopically dominated by heterogeneously supported conglomerates,granular supporting conglomerates,conglomerate sandstones,medium-coarse sandstones,followed by fine sandstones; and are microscopically dominated by feldspar lithic sandstone and lithic feldspathic sandstone,with the lithic being mainly of volcanic rocks,followed by metamorphic rocks. The reservoirs have low permeability,and the reservoir space is composed of intergranular dissolved pores,followed by primary intergranular pores. The diagenetic environment underwent a change from neutral to acidic(meteoric water leaching),alkaline,acidic,alkaline,acidic to alkaline. Continuous compaction after meteoric water leaching and the cementation of carbonate and clay minerals under alkaline conditions are the fundamental reasons for the low permeability,whereas the meteoric water leaching and dissolution in acidic environments are the main reason for the formation of secondary pores,and the continuous hydrocarbon filling is conductive to the preservation of reservoir pores since 7 Ma. The alkaline fluid environment formed by organic acid decarboxylation since 1.5 Ma is easy to form carbonate cementation and illite filling,which is the ultimate cause for the formation of low permeability reservoirs.

Identification of Ordovician karstic paleochannels and its accumulation significance in Halahatang area

DAI Dongdong, FANG Qifei, WAN Xiaoguo, CAI Quan

2017, Vol.29(5): 89–96 Abstract ( 356 ) PDF (19076 KB) ( 336 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.010

The paleo-karst landforms formed in the Ordovician Lianglitage Formation after the deposition of carbonate rocks in the Halahatang area,which is favorable for the formation of high-yielding hydrocarbon reservoirs, but its complexity brings high exploration risk. The seismic,drilling and logging data were applied to optimize the automatic identification of riverbed erosion depth,RGB mixing three primary colors,amplitude attribute extraction and seismic reflection structure analysis,and six groups of river channel and 47 underground river channels in the Ordovician carbonate rocks were identified. The study shows that the reservoir is closely related to the underground river system,and there are three types of underground river system including inflow,outflow and aquifer cave,and the former two types are predominant. This underground river system is the main mechanism of the formation of large-scale fractured-vuggy reservoirs,and it is also the foundation for the large-scale hydrocarbon enrichment areas. The reservoirs with this genesis become the key targets of exploration and development. This identification method of carbonate karstic paleochannels is significant for favorable reservoir prediction, hydrocarbon enrichment area optimization,exploration and development in paleo-karst area.

Quantitative evaluation of carbonate reservoir pore structure based on fractal characteristics

LIU Hangyu, TIAN Zhongyuan, XU Zhenyong

2017, Vol.29(5): 97–105 Abstract ( 411 ) PDF (4523 KB) ( 432 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.011

Pore structure of large scale porous limestone reservoir with strong heterogeneity is very complex,so it is difficult to evaluate its pore structure of Mishrif Formation of W oilfield in Iraq. Based on thin section observation, porosity and permeability test and mercury injection capillary pressure test,fractal theory was applied to quantitative pore structure evaluation,and the pore fractal dimension criterion for reservoir type classification was established. There are two types of reservoir pore structure fractal characteristics. Some samples called "single segment" perform obvious fractal character overall. Others called "multiple segments" have distinct large pore throat system and small pore throat system which perform unique fractal characters respectively while have no uniform fractal character overall. The complexity and heterogeneity of pore structure of porous limestone can be reflected by fractal dimension,the greater the fractal dimension,the more complex pore structure,and the more conspicuous segmental character in the relationship between capillary pressure and water saturation,the stronger the heterogeneity. The samples were classified based on the fractal dimension combined with porosity and permeability distribution of the samples. The majority of type Ⅰ-Ⅱ and type Ⅲ-Ⅳrespectively corresponded to "multiple segments" and "single segment" fractal characteristics. It has an important guiding significance for the quantitative evaluation of pore structure to similar carbonate reservoir.

Fractal characteristics of tight sandstone reservoir using mercury intrusion capillary pressure:a case of tight sandstone reservoir in Jizhong Depression

GE Xiaobo, LI Jijun, LU Shuangfang, CHEN Fangwen, YANG Dexiang, WANG Quan

2017, Vol.29(5): 106–112 Abstract ( 358 ) PDF (1671 KB) ( 458 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.012

To evaluate the type of tight sandstone reservoir and provide theoretical basis for the exploration and development of tight oil and gas,the fractal theory,mercury intrusion capillary pressure analyses,as well as reservoir physical properties,were used to discuss the pore structure characteristics of tight sandstone reservoir in Jizhong Depression,by analyzing 11 tight sandstone samples. The results show that an evaluation method for fracture(>10 μm,in diameter),macropores(1-10 μm),mesopores(0.1-1.0 μm)and micropores(< 0.1 μm)within tight sandstone reservoir was established by mercury intrusion curves. This method was verified using fractal geometry theory. Based on the above classification,the volume contents of pores and fractures were estimated by mercury intrusion curves. Morever,three types(Ⅰ,Ⅱ and Ⅲ)of tight sandstone reservoir in Jizhong Depression were analyzed based on the distribution of pore volume,porosity,permeability,displacement pressure and mercury withdrawal efficiency. Type I tight sandstone reservoir is characterized by abundant micropores and rarely open fractures,which leads to a low permeability. Type Ⅱ tight sandstone reservoir has high open fractures but a few micropores. Type Ⅲ tight sandstone reservoir not only has abundant micropores but also has high open fractures. Two main parameters obtained from the mercury porosimetry analysis, the mercury withdrawal efficiency and permeability,reflect the totally minable potential and production rate of tight oil and gas,respectively. The more the micropores develop,the higher the mercury withdrawl efficiency is,and the simpler and more homogeneous the pore structure is. The flowing capacity is controlled by fractures and macropores. Therefore,the type Ⅲ tight sandstone reservoir in Jizhong Depression is the most appropriate to exploit.

Prestack gather residual moveout correction based on shape context and dynamic time warping

SHI Zhanzhan, TANG Xiangrong, PANG Su, CHI Yuelong

2017, Vol.29(5): 113–119 Abstract ( 318 ) PDF (29075 KB) ( 471 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.013

Prestack reflection events cannot be flatten by conventional velocity analysis and NMO,statics correction, due to anisotropy and heterogeneity of the subsurface media. This is a difficult problem for AVO attribute analysis and prestack inversion. Based on shape context and dynamic time warping(SC-DTW),a new method of prestack residual moveout correction was introduced and verified by numerical simulation(model)and example analysis. The results show that the residual moveout correction method based on SC-DTWprestack gather has better anti-noise capability,better robustness to seismic waveform distortion,and can effectively eliminate the residual moveout of prestack seismic traces. The continuous waveform of the seismic events and the amplitude characteristics are not changed,which can improve the accuracy of seismic data processing and interpretation,such as AVO attribute analysis and prestack inversion. Using waveforms similarity of prestack gathers,the method optimizes for a reference trace,and run SC-DTW calculation of each trace with reference trace in calculation window, to calculate the dynamic warping path and residual moveout correction. The utility model has better practicability and popularization value.

AVO response of different types of gas-bearing sandstone and error analysis of approximate formulas

WANG Xiujiao, HUANG Jiaqiang, JIANG Ren, ZENG Qingcai

2017, Vol.29(5): 120–126 Abstract ( 454 ) PDF (1683 KB) ( 817 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.014

Based on three common approximate formulas including Aki-Richards,Shuey and Hilterman in AVO inversion technology and four types of gas-bearing sandstone,three approximate formulas were calculated for AVO response in comparing with Zoeppritz exact value. Both relative error and incident angle curves were plotted. The results show that Aki-Richards and Shuey approximate formulas own lower approximate errors than that of Hilterman approximate formula for the interface of four class gas-bearing sandstone. The accuracy of Shuey formula rises with the increase of the incident angle. Under different reservoir conditions, three approximate formulas' calculation results possess different percentage errors and curve characteristics, and all approximate formulas are more applicable for the third type AVO response. Quantitative analysis result which is calculated by three approximate formulas in four types gas-bearing sandstones provides beneficial theoretical foundation for reservoir parameter inversion.

Lithology identification based on principal component analysis and fuzzy recognition

MAZheng, ZHANG Chunlei, GAO Shichen

2017, Vol.29(5): 127–133 Abstract ( 389 ) PDF (1908 KB) ( 511 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.015

It is not ideal that characterization the complex lithology is disturbed by logging curves,which are redundancies in high similarity logging parameters. Based on principal component analysis(PCA) and fuzzy recognition, to solve this problem,a method was adopt to identify the complex lithology,and verified by carbonate rocks logging data of from fifth member of Majiagou Formation in Sudong 41-33 blocks of Sulige gasfileld. The complex lithology identification methods chose six logging curves of AC,GR,Pe,CNL,DEN,RLLD firstly,which are sensitive to lithology change,then construct three comprehensive variables Y1,Y2,Y3 by principal component analysis,and finally identify lithology by fuzzy recognition method. Compared with traditional identification methods,the method eliminate the fuzziness and correlation effectively,and the accuracy rate is reached up to 86%. It is a practical and effective method of complex lithology identification,and has certain popularization and application value.

Productivity prediction method of shallow reservoir inWeibei Oilfield

CHEN Mingqiang, WANG Ning, ZHANG Yang, REN Long

2017, Vol.29(5): 134–139 Abstract ( 304 ) PDF (1462 KB) ( 456 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.016

Natural fractures have great influences on the productivity of oil wells in shallow and low permeability reservoir in Weibei Oilfield. Based on the percolation theory and fractal theory,the permeability of natural fractures was characterized by introducing fractal dimension and analyzing the development degree of natural fractures influences of the specific productivity index per-meter in shallow reservoir of Weibei Oilfield,and a productivity forecast mathematical model of vertically fractured well was established in low permeability and fractured reservoir to reveals the productivity characteristics. The results show that the permeability of the low permeability reservoir is improved effectively by natural fractures,and the productivity of the oil wells is almost increased exponentially along with the development degree of the natural fractures after fracturing. Consequently,enlarging the fracturing scale appropriately can greatly improve the productivity in natural fracture development zones when reforming the shallow reservoir. Meanwhile,it's the best to minimize the damage and pollution to the natural fractures. The results have a certain reference value for the rational development of similar reservoirs.

Enrichment mechanism and mining technology of high rank coalbed methane in Xiaolinhua coal mine, northern Guizhou

GAOWei, JIN Jun, YI Tongsheng, ZHAO Lingyun, ZHANG Manting, ZHENG Dezhi

2017, Vol.29(5): 140–147 Abstract ( 262 ) PDF (1725 KB) ( 578 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.017

To reveal the coalbed methane reservoir characteristics of Xiaolinhua coal mine in northern Guizhou, the basic geological conditions of structure,hydrogeology,coal-bearing property,reservoir and sealed condition were analyzed. The results show that the coalbed methane resources mainly occurred in the upper and lower coal measures,containing five layers coal,of which the cumulative thickness is large,the coal rank is No. 3 anthracite coal,and the original structure of coalbed is more complete. The coal reservoir is characterized by suitable burial depth,high gas content,strong adsorption and good pore connectivity,and the average coal reservoir pressure gradient is 0.87 MPa/100 m,average porosity is 2.95%,average permeability is 0.03 mD. The valuable suggestions are proposed for coalbed methane mining in target coal seam optimization,drilling technology, fracture technology and combined seam gas drainage technology. It is beneficial for coalbed methane ground development that the preservation conditions of high rank coalbed methane are advantage and the lower coal measures are better than the upper coal measures.

Remaining oil distribution pattern controlled by interlayer in A oilfield in Bohai Sea

LIU Chao, LI Yunpeng, ZHANGWei, FENG Haichao, WANG Yingchao

2017, Vol.29(5): 148–154 Abstract ( 353 ) PDF (11164 KB) ( 490 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.018

In order to analyze distribution rule of remaining oil controlled by interlayer,the reservoir architecture and numerical simulation analysis of interlayer were carried out in Bohai A oilfield with high water cut stage. The results show that foreset imbricate interlayers are mainly composed of shale interlayer and tight sandstone interlayer,which average thickness is less than one meter. The remaining oil is controlled by position and area of interlayer. The longer the horizontal extension length of interlayer is,the greater the enrichment area of remaining oil is in the bottom zone of interlayer. In the injection well,oil well and interlayer configuration,when the production well penetrated into interlayer,interlayer has greater effect on remaining oil,which will be more enriched in bottom zone of the interlayer. Under the control of interlayer and reservoir rhythmicity,the remaining oil distribution patterns were divided into three types:interlayer top enrichment type,interlayer top-bottom enrichment type and interlayer bottom enrichment type. The results provide decision basis for adjustment,tapping potential and stabilizing oil and controlling water measures in late stage of oilfield.

Optimization of technological parameters and evaluation of reservoir adaptation by water plugging and profile control: a case from Bohai SZ36-1 oilfield

ZHANG Baokang, XU Guorui, TIE Leilei, SU Xin, LU Xiangguo, YAN Dong

2017, Vol.29(5): 155–161 Abstract ( 603 ) PDF (1594 KB) ( 610 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.019

SZ36-1 oilfield in Bohai has the characteristics of high crude oil viscosity,single well water injection quantity,and the reservoir is characterized by loose cementation,strong heterogeneity and high permeability. The water injection development resulted in breakthrough phenomenon and damaged reservoir structure,which urgently needs to be taken fluid diversion measures. Taking injection pressure,water cut and oil recovery as evaluation indexes,the effect of water shutoff and profile control joint operation on increasing oil and decreasing water and its influencing factors were studied by experiment. The results show that water shutoff agent optimization composition of 4%+ 4% starch acrylamide + 0.036% crosslinking agent + 0.012% initiator + 0.002% anhydrous sodium sulfite,plugging agent slug optimization combination 0.05 PV segment prefix plug(4% starch)+ 0.025 PV to 0.075 PV plugging agent and protective slug 0.025 PV(4% starch)+ replace segment plug 0.05 PV(polymer solution,CP=1 500 mg/L),optimization of profile control agent composition and slug combination 0.05 PV to 0.10 PV profile control agent(Cr3+ polymer gel,CP=3 500 mg/L). With the increase of reservoir heterogeneity and oil viscosity,the growth rate of oil recovery increases. The joint operation of profile control and water plugging has strong reservoir adaptability.

Microorganism preparation and application evaluation on microbial enhanced high-pour point oil recovery in Liaohe Oilfield

WANG Xiaotong, XIANG Longbin, ZHANG Yixin

2017, Vol.29(5): 162–168 Abstract ( 293 ) PDF (1587 KB) ( 535 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.05.020

The high pour-point oil is characterized by high proportion of wax,high freezing point and low fluidity, which make it difficult for development. To solve this problem,one strain of P.aeruginosa and two strains of Geobacillus were selected for microbial enhance high-pour point oil recovery research and characteristics assessment through four components analysis and the saturated hydrocarbon GC spectrum analysis. The results show that four components of oil selectively degrade by the strains:degradation rate is 23.0%-42.3%,meaning while the long carbon chain in the oil is shortened,the value of w(nC21-)/w(nC22+) and w(nC21 + nC22)/w(nC28 + nC29) increased by 0.33-0.57. The strains'capability of producing bio-surfactant was evaluated:the surface tension of P.aeruginosa fermentation broth decreases from 72.21 mN/m to 26.81 mN/m. The two strains of Geobacillus emulsify high-pour point oil with an emulsification index of 70.6% and 82.3% respectively. Based on characteristics of these three microorganisms,a novel compound microorganism preparation which is compatible with indigenous microorganisms was successfully designed. The oil viscosity decreases by 63.86% and the oil freezing point is lowered by 6℃ by this microbial preparation. Through water flooding simulation test,the preparation enhances high-pour point oil recovery by 6.46%-8.48% in the middle permeability(200 mD) and low permeability(50 mD). Afield test involved 6 wells was conducted in Liaohe Oilfield,which demonstrates the stability and high efficiency of this novel compound microorganism preparation in enhancing high freezing point oil recovery.