Lithologic Reservoirs

The basic concepts, characteristics and research significance of distributive fluvial system (DFS) were introduced. The new geological term, DFS, is advanced recently, by statistically analyzing the sedimentary systems of alluvial rivers in more than 700 continental basins using Google Earth, and it dominates all sedimentation and develops in all tectonic settings, including compressional, extensional and strike-slipping. Six criteria of discrimination of DFS, six planform types on DFS and five terminal types of DFS were recognized. The DFS sedimentary model can show the characteristics of fluvial depositional system in a larger range than the single channel facies model, which is of great significance to understand the sedimentary system of continental petroliferous basins and guide oil and gas exploration.

A new quantitative method of sedimentary facies mapping of large lacustrine depression: a case from Chang 7 reservoir in central Ordos Basin

LIN Senhu, WANG Mengshi, YUAN Xuanjun

2017, Vol.29(3): 10–17 Abstract ( 1297 ) PDF (10337 KB) ( 328 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.002

In order to meet the needs of unconventional hydrocarbon exploration nowadays and improve the accuracy and efficiency of sedimentary facies mapping,the lithofacies classification,facies distribution,lithology combination proportion and sedimentary environment evolution of Triassic Chang 7 reservoir in Ordos Basin were analyzed. There are ten types of lithology recognized from the sieve residue log plot. Five of them are dominated,including fine sandstone,argillaceous siltstone,silty mudstone,mudstone and shale,of which the thickness is about 97% of the strata. Based on core observation and statistical analysis,the thickness composition of each microfacies with the five types of lithology was established,which can be used to implement quantitative sedimentary facies mapping. By overlapping the thickness percentage isoline maps of the five types of lithology in Chang 7 reservoir,various microfacies can be intensively identified,including delta plain distributary channel,delta front subaqueous distributary channel,subaqueous distributary channel,distal bar,mouth bar,prodelta, debris flow, turbidite, semi-deep to deep lacustrine.

Relationship between micro-pore characteristics and pore structure of low permeability sandstone: a case of the fourth member of Shahejie Formation in southern slope of Dongying Sag

YAN Jianping, LIANG Qiang, GENG Bin, LAI Fuqiang, WEN Danni, WANG Zhoufeng

2017, Vol.29(3): 18–26 Abstract ( 426 ) PDF (23225 KB) ( 596 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.003

The low permeability sandstone reservoir has become an important exploration target, but the variety of micro-pore structure makes the logging response characteristics difficult to reflect reservoir features clearly. The data of mercury injection, nuclear magnetic resonance (NMR), physical properties, thin sections and CT were used to analyze the pore structure of low permeability beach bar sandstone of the fourth member of Shahejie Formation (Es4) in southern slope of Dongying Sag. The pore structure were divided into three types and five subtypes:typeⅠ (Ⅰ1 and Ⅰ2), type II (Ⅱ1 and Ⅱ2)and type Ⅲ. The pore structure type is controlled by mineral content, grain size and diagenesis. The volume and features of micropores (pore throat radius less than 0.024 8 μm) are important factors that cause the differences of pore structure types. The relationships among micropore volume, mineral content, grain size and electric properties were analyzed. It is found that mineral content and grain size affect micropore volume and features. In addition, the micropore volume is closely related to the electric properties. Logging curves are sensitive to the change of micropore volume, so it is helpful for dividing pore structure type in wellbore and identifying effective reservoirs.

Characteristics and formation mechanism of dissolved pores in tight oil reservoirs of Lucaogou Formation in Jimsar Sag

YAN Lin, RAN Qiquan, GAO Yang, CHEN Fuli, WANG Shaojun, LI Chongfei

2017, Vol.29(3): 27–33 Abstract ( 341 ) PDF (5396 KB) ( 704 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.004

Dissolved pores are well developed in tight oil reservoirs of Lucaogou Formation in Jimsar Sag, however, its controlling factors and formation mechanism are unclear. Combined with analyses of reservoir mineral composition, hydrocarbon accumulation evolution and diagenetic evolution, the data of cores, thin section, scanning electronic microscope and physical property test were used to study the pore types and characteristics, the genetic mechanism and distribution of dissolved pores of Lucaogou Formation. The results show that dissolved pores developed in terrigenous clastic rocks, endogenetic sedimentary rocks and volcanic clastic rocks, and the formation of the dissolved pores is influenced by internal and external factors. The soluble minerals such as feldspar and carbonate rocks dissolved by organic acid are the main formation way of the dissolved pores. The detritus feldspar fine sandstone reservoir in the middle of the second member of Lucaogou Formation, with well developed dissolved pores, good physical properties, large vertical thickness and stable plane distribution, is an important zone for the next tight oil exploration and development.

Characteristics and formation conditions of tight tuff reservoir of Tiaohu Formation in Malang Depression

XU Xiongfei, WEN Chuanjiang, LI Yuping, REN Zhongyue, XIAO Dongsheng, FENG Yaqin

2017, Vol.29(3): 34–41 Abstract ( 294 ) PDF (50535 KB) ( 505 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.005

The tight tuff reservoir of Tiaohu Formation in Malang Depression has become one of the key fields for exploration in Santanghu Basin in recent years. The reservoir characteristics and formation conditions are of great significance for deepening the exploration of tight tuff reservoir in Santanghu Basin. Based on the data of core observation,thin sections,whole rock X-ray diffraction,field-emission scanning electron microscope and mercury capillary pressure,the micro-characteristics of tight tuff reservoir were studied,and the distribution of tight tuff reservoir were characterized according to the data of amplitude,frequency by combining drilling and seismic method. The results show that the tight tuff reservoirs are mainly composed of crystal chips and glass chips,and rich in organic matter,with devitrified pores developed. The reservoir has the features of medium porosity,ultra-low permeability and high oil saturation. The stable shallow-semi deep lacustrine environment which is lacking of terrigenous materials is the key for forming tight tuff reservoir,volcanic depression within a certain range from the volcanic apparatus controls the distribution of effective tight tuff reservoir,and devitrification and dissolution are critical for improving the reservoir properties of tuff. The volcanic depressions in the northern slope area of Malang Depression are favorable for the development of tight tuff reservoir,the west blocks of L1 well and east blocks of L104 well,south west blocks of M7 well in Malang Depression are the next favorable targets for tight oil exploration.

Controlling factors of Carboniferous volcanic reservoirs and favorable reservoir prediction in Xiquan area, Junggar Basin

HE Xianying, LIU Yong, XU Xuelong, LIU Bangxing, ZHANG Shuncun

2017, Vol.29(3): 42–51 Abstract ( 334 ) PDF (17940 KB) ( 504 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.006

The volcanic reservoirs of Carboniferous in Xiquan area of Junggar Basin are characterized by smallscale volcanic body, and the main controlling factors are not clear. On the basis of core observation and thin section identification, combined with logging, analysis and test data, a statistical analysis of the lithologies of Carboniferous in Xiquan area was carried out. The main controlling factors of reservoir physical properties and its distribution law were analyzed. The results show that the lithology in the southern structural belt is mainly composed of andesite, volcanic breccia and tuff, and mainly tuff, sedimentary rock and andesite in the northern structural belt. The reservoir properties in the southern structural belt are obviously better than that in the northern structural belt, of which the main controlling factors are lithology, lithofacies, tectonic movement and weathering leaching. The volcanic facies, such as volcanic breccia and tuff in the southern structural belt, the overflow facies of andesite in the northern structural belt, and their overlap zones with the structure highs and the fracture development, are favorable plays for hydrocarbon exploration.

Sedimentary facies and favorable reservoir prediction of Cretaceous Xiagou Formation K₁g₁³ in Ya'erxia area, Jiuquan Basin

YUAN Bochao, XIAO Wenhua, WEI Haoyuan, WEI Deqiang

2017, Vol.29(3): 52–65 Abstract ( 475 ) PDF (80542 KB) ( 385 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.007

The submember of the first member of Cretaceous Xiagou Formation (K1g13)is one of the main oilproducing intervals in Ya'erxia area, Jiuquan Basin. However, the understanding of its sedimentary facies and influencing factors and distribution of favorable reservoirs are unclear. Based on the data of core, well logging, oil production test, the sedimentary facies and favorable reservoir distribution of K1g13 in Ya'erxia area were discussed. The results show that fan delta-lacustrine and nearshore subaqueous fan-lacustrine sedimentary systems are mainly developed in K1g13, which can be further divided into eight types of subfacies and 16 types of microfacies, and the favorable reservoir distribution is controlled by sedimentary facies belt and dissolution zone. The subaqueous distributary channel and mouth bar are the main favorable sedimentary facies belts. The secondary dissolved pores are the main reservoir spaces, and their development is mainly controlled by the content of feldspar, debris and matrix, and burial depth. By superposing the dissolution zone and favorable microfacies on the structural map, the distribution of favorable reservoirs of K1g13 was predicted:east to well Yaxi 1-1 and well Yaxi 116, west to well Yaxi 115 and well Liu 10, south to well Yaxi 5, and north to well Yaxi 112.

High-resolution sequence stratigraphy of alluvial fan: a case from Guantao Formation in SAGD development zone of Du 84 block, Shuyi area, Liaohe Depression

LI Chen, FAN Tailiang, GAO Zhiqian, QIAO Xiaohui, FU Wei

2017, Vol.29(3): 66–75 Abstract ( 303 ) PDF (2836 KB) ( 655 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.008

In order to recognize the distribution of remaining oil and guide the oil development in SAGD (Steam Assisted Gravity Drainage)development zone,the data of core,well logs and seismic were applied to study the stratigraphic sequence model of Guantao Formation in SAGD development zone of Du 84 block,Shuyi area,Liaohe Depression. The results show that Guantao Formation could be divided into one long-term sequence cycle (LSC),four middle-term sequence cycles (MSC)and ten short-term sequence cycles (SSC). Based on accommodation changes,SSC types include typeⅠ, Ⅱ, Ⅲ,Ⅳ and Ⅴ. Based on MSC isochronous unit,vertically SSC type is related to its position in MSC. The preserve degree of MSC is controlled by its position in LSC,and MSC formed in the ascending hemicycle of LSC can preserve more different SSC types. In a single MSC,the accommodation of SSC would gradually increase along source direction. The SSC type in Guantao Formation is related to the reservoir physical properties. The position of high quality reservoir is located in the border between root-fan and middle-fan or in the intra-middle-fan,and this position is always formed in the early or middle stage in the ascending hemicycle of MSC.

Integrated dynamic and static identification method of fracturedvuggy carbonate reservoirs: a case from the Ordovician in Tarim Basin

CHENG Fei

2017, Vol.29(3): 76–82 Abstract ( 354 ) PDF (26401 KB) ( 483 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.009

The carbonate reservoirs are characterized by strong heterogeneity, anisotropy and complex genetic mechanism. The vuggy, caves and fractures are associated with each other in variety of different genesis, formation mechanisms and scales in a Ordovician carbonate reservoir of Tarim Basin, thus it is difficult to classify carbonate reservoir types by using single static data. The static and dynamic data from 145 wells and their response characteristics in different types of reservoirs were analyzed, and well testing permeability, wellbore storage coefficient, well control radius, acid fracturing pressure of pump off, cumulative production hydraulic curve, drilling blowdown leakage, seismic reflection characteristics and logging curve were selected to establish the identification model of carbonate reservoirs. The reservoirs were divided into three types:cavity-fracture, cavity and fractured-vuggy. This method overcomes the limitation of identifying reservoir types by single factor in the past, ex-pands the research methods of the combination of dynamic and static methods, and provides a basis for the identification of carbonate reservoirs.

Characteristics and main controlling factors of shale gas reservoirs: a case from Longmaxi Formation in Baojing area, NW Hunan province

HU Bowen, LI Bin, LU Dongsheng, LUO Qun, LI Jianxin, WANG Yilin

2017, Vol.29(3): 83–91 Abstract ( 448 ) PDF (24684 KB) ( 567 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.010

The organic-rich shale of Longmaxi Formation is an important shale gas exploration horizon in Baojing area, NW Hunan Province. In order to study the characteristics of Longmaxi shale gas reservoir and gas occurrence rule, combined with field geologic investigation, the data of mineralogy, organic geochemistry, physical properties, gas-bearing property, isothermal adsorption, scanning electronic microscope and Nano-CT, were used to analyze the characteristics of lithofacies and reservoir and main controlling factors for the gas-bearing property of Longmaxi shale. The results show that three types of lithofacies are developed in the Longmaxi Formation,including carbon-silty shale, carbonaceous shale and carbon-argillaceous siltstone; the main pore types are intergranular pores, dissolved pores, intercrystalline pores, fossil pores, organic pores and micro-fractures. The main types of fractures are structural fractures and diagenetic fracture. According to the pore size, the reservoir pore can be divided into micropores, mesopores and macropores. Mesopores have the biggest contribution to the whole pore volume,followed by micropores, and the macropores have the minimum proportion in the whole pore volume. The analysis shows that the microporous volume and surface area of shale have a good positive correlation with the largest methane adsorption contents,which are both controlled by TOC content in shale. Microfractures have a good positive correlation with gas content,which indicates that the micro-fracture has an important influence on shale gas-bearing properties. The results of Nano-CT show that most of the gas flow spaces are organic pores and micro-fractures. The organic matter content and the development of micro-fractures are the main controlling factors for the enrichment of shale gas.

Permeability modeling based on the classification of beach-controlled karst dolomite reservoirs: a case from Longwangmiao Formation in Moxi-Gaoshiti area, central Sichuan Basin

SIMA Liqiang, CHEN Zhiqiang, WANG Liang, FAN Ling, CHEN Hebin, FU Yonghong

2017, Vol.29(3): 92–102 Abstract ( 316 ) PDF (8413 KB) ( 366 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.011

Reservoir permeability is greatly affected by karstification, and the applicability of existing permeability models is poor in Cambrian dolomite reservoirs of Longwangmiao Formation, Moxi-Gaoshiti area, central Sichuan Basin. The core photos, rock slices, mercury injection capillary pressure, nuclear magnetic resonance and logging data were used to classify the reservoir types according to karstification,reservoir space and pore structure. The beach-controlled karst dolomite reservoirs with strong heterogeneity were divided into karst cave type, dissolved pore type and matrix pore type. Then, new permeability models were established with physical property analysis data of full diameter core and standard plunger core by the difference between their characterization scale. Full diameter core has larger scale of representation, so as to establish the permeability interpretation model of karst cave type; standard plunger core has smaller scale of representation, so as to establish permeability interpretation models of dissolved pore type and matrix pore type. Practical application results show that, compared with the conventional Timur formula and NMR Coates model, the permeability value calculated by classified statistic models is more consistent with core analysis. This method can effectively improve the accuracy of permeability calculation in beach-controlled karst reservoirs.

Application of image enhancement technique to fracture identification based on Contourlet transform

ZHAO Wanjin, ZHOU Chunlei

2017, Vol.29(3): 103–109 Abstract ( 296 ) PDF (21178 KB) ( 643 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.012

It is difficult to identify small-scale faults and fracture zone by seismic post-stack data, and image enhancement technique has been applied in seismic processing and interpretation. Image enhancement technique based on Contourlet transform,which is characterized by multi-scale decomposition and multi-directional filtering, can be used to highlight the anisotropy of post-stack data. Seismic physical modeling analysis shows that compared with other techniques,image enhancement technique has obvious advantages in highlighting the distribution of small-scale faults and tectonic fracture zones. This technique has been successfully applied to practical production,which plays an important role in the interpretation of complex structural faults and well deployment in fractured reservoirs.

Application of facies-controlled technique to bioclastic shoal reservoir prediction in less well zones

LI Jinlei, CHEN Zuqing, WANG Liangjun, LIU Lihui, LI Jianhai

2017, Vol.29(3): 110–117 Abstract ( 290 ) PDF (13532 KB) ( 664 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.013

The bioclastic shoal reservoir has strong heterogeneity, and it is difficult to accurately predict the reservoirs and physical properties by conventional geophysical prospecting methods. A set of integrated techniques of seismic microfacies analysis, facies-controlled reservoir inversion, facies-controlled porosity prediction was formed, to predict bioclastic shoal reservoirs and their properties. The results show that facies analysis techniques of plane sedimentary facies interpretation and profile seismic facies monitoring based on the waveform clustering can be used to realize seismic microfacies analysis. Under the control of sedimentary microfacies, the low frequency model was established by filling the average velocity of lithology in each facies, and then combined with the color inversion technology, the impedance inversion could be completed. This is an effective inversion method in the less well zones. According to the results of statistical rock physical analysis, the impedance could be transformed to porosity under the control of sedimentary structure and microfacies, and then the bioclastic shoal reservoir property prediction could be realized in the less well zones. Practical application has proved that this method is effective for the prediction of bioclastic shoal reservoirs.

Influence of overlying horizontal stratum on seismic amplitude of target zone

DENG Shuai, LIU Xuewei, WANG Xiangchun

2017, Vol.29(3): 118–125 Abstract ( 237 ) PDF (2510 KB) ( 700 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.014

Seismic amplitude is an important parameter to identify the lithology of target zone, however, it is greatly affected by overlying stratum. Based on the forward modeling, the numerical simulation of two-way wave equation was applied to study the amplitude change of seismic wave when it travels through the overlying stratum with different velocity and scale, and the relationship between the overlying stratum structure and seismic amplitude of the target zone was discussed. By building high ordered staggered-grid finite difference algorithm containing PML (perfect matching layer)attenuation coefficient and using GPU parallel acceleration, the amplitude change regularity of the target zone of 3D layered velocity model was defined. The experiment results show that the amplitude of the target zone will change accordingly with the change of reflection coefficient of the overlying stratum, and it will change abnormally especially when the reflection coefficient of overlying stratum tends to be consistent. This study results are favorable for correct lithology identification by seismic data.

Brittleness of tight gas reservoirs based on stress-strain curves

ZHANG Jie, ZHANG Chaomo, ZHANG Zhansong, ZHANG Chong, NIE Xin

2017, Vol.29(3): 126–131 Abstract ( 283 ) PDF (1989 KB) ( 720 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.015

The brittleness of rocks is one of the most important parameters in tight gas exploration and development. The higher the reservoir rock brittleness is, the more fracturing fracture develops, and the higher the production capacity will be. A variety of brittleness calculation formulas were used to establish a new calculation model of brittleness index of the Permian tight gas reservoir in northeastern Ordos Basin by researching the uniaxial compression crack mechanism of brittle rock, and the stress and strain of the first crack point and the peak under uniaxial compression. The results show that the brittleness index calculated by the new model can characterize the brittleness of the rocks effectively, because it has obvious function relationship with the brittleness calculated by static rock mechanics parameters in the experiments. Based on the fracturing effect in uniaxial compressive experiments, the new brittleness index and the initial crack point index could be used to establish the standard of reservoir fracturing effect. This result enriches the reservoir brittleness calculation method, and sets a new standard of brittleness evaluation.

Reservoir architecture of fan delta front and its oil-control models: a case of Eh₃Ⅳ3¹reservoir in Zhaowa block of Zhaowa Oilfield, Biyang Depression

LI Yan

2017, Vol.29(3): 132–139 Abstract ( 377 ) PDF (2276 KB) ( 612 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.016

In order to reveal the architecture characteristics of fan delta front reservoir and its control effects on the migration of oil and water, the data of core, well logs and production, were used to analyze the reservoir architecture and its controls on the remaining oil of Eh3Ⅳ31 in Zhaowa block based on the theory of fluvial facies reservoir architecture. The results show that the Eh3Ⅳ31 reservoir was divided into seven fifth-level architectural units which were separated by muddy interbed, calcitc-cement interbed and muddy sandy-conglomerate interbed. According to the qualitative and quantitative identification criteria of single subaqueous distributary channel or bar, the size, spatial morphology and distribution of the fifth-level architectural unit were defined under the isochronous stratigraphic framework of the fifth-level architectural unit. There are three kinds of oil-control models. The residual oil under the longitudinal and lateral facies-change oil-control models is mainly distributed in the middle and upper part of the subaqueous distributary channel and low permeability zone of non-channels, while the residual oil under the unstable interbed oil-control model is mainly distributed in the lower part of the interbed. This study is of great significance to improve the oilfield development effect.

Suitability evaluation of enhanced oil recovery by CO₂ flooding

YANG Hong, WANG Hong, NAN Yufeng, QU Yaning, LIANG Kaiqiang, JIANG Shaojing

2017, Vol.29(3): 140–146 Abstract ( 352 ) PDF (1374 KB) ( 723 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.017

In order to solve the problems that the influencing factor selection and suitability evaluation of enhanced oil recovery (EOR)by CO2 flooding are limited to qualitative or semi quantitative analysis, grey correlation analysis method was introduced to calculate the association degree and weight coefficient of the EOR influencing factors by CO2 flooding in seven CO2 flooding reservoirs, and the EOR influencing factors by CO2 flooding were quantitatively analyzed. Meantime, the suitability of CO2 flooding in reservoir was evaluated, and this method were used to evaluate CO2 flooding potential in Dingbian-Wuqi oilfield. The results show the order of EOR influence factors from strong to weak:ratio of MMP to original reservoir pressure, formation effective thickness, buried depth, crude oil viscosity underground,ground crude oil density, remaining oil saturation, reservoir temperature, porosity and permeability. The CO2 flooding is mainly for type Ⅰ and Ⅱ reservoirs in Dingbian-Wuqi oilfield, which means that it is suitable for CO2 flooding in the oilfield.

A new method of measuring critical liquid carrying flow rate in the variable wellbore-rate gas well: a case of multi-completion gas wells in Xihu Sag, the East China Sea

LU Kefeng, JIAN Jie, ZHANG Yanzhen, ZHU Wenjuan, XIAO Han

2017, Vol.29(3): 147–151 Abstract ( 295 ) PDF (1372 KB) ( 869 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.018

For the constant wellbore-rate gas well, the critical liquid carrying flow rate depends on cross-sectional area of wellbore. However, in the research of multi-completion gas wells in Xihu Sag of the East China Sea, there aer 39% of the survey wells with the accumulated fluid levels located at the sliding sleeves. A set of determination method of measuring critical liquid carrying flow rate in the variable wellbore-rate gas wells was formed by building a regional critical liquid carrying flow rate model with gas wells. This method includes the selection of fitting data of model coefficient X, the condition of filtering the wellbore node where is most likely to appear accumulated fluid, and the transformation method of turning the critical liquid carrying flow rate at the wellbore node to that in the whole well. The result shows that sectional flow distribution in multi-completion gas wells results more effusion than that in single layer wells and the accumulated fluid levels are usually located at the sliding sleeves. The study has certain reference significance for rational production adjustment in multi-completion gas wells.

Polymer/surfactant binary flooding in A oilfield with high temperature and high salinity

LIU Chen, WANG Kai, WANG Yefei, ZHOU Wensheng

2017, Vol.29(3): 152–158 Abstract ( 327 ) PDF (1427 KB) ( 793 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.019

Aiming at weak formation adaptability and limited temperature resistance of common polymer/surfactant system,which largely limits its application in low-permeability,high-temperature and high salinity reservoir, a binary flooding system was established based on the combination of polymer and anionic-nonionic surfactant. Through laboratory experiments,the performances of the binary flooding system were studied,such as viscosity, interfacial tension,aging stability,adsorption capacity,chromatographic fractionation effect and oil displacement efficiency. The results show that the interfacial tension between the system and the crude oil could be lowered to 10-3 mN/m while maintaining excellent stability. The saturated adsorption value of the binary flooding system is much lower than that of single system. Meanwhile,the effective distance of ultra-low interfacial ten-sion of surfactant extended from 19% to 27%. However,the chromatographic fractionation effect was not negligible. The binary flooding system,which is 0.4 PV (1 000 mg/L HF62208+0.3% NPAC),can increase oil recovery by 11% on natural core with permeability of 18.6-62.5 mD from A oilfield, indicating excellent EOR performance for low-permeability reservoirs.

Empirical formulas of relative permeability curve of water drive reservoirs

WANG Dongqi, YIN Daiyin

2017, Vol.29(3): 159–164 Abstract ( 474 ) PDF (1488 KB) ( 891 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.03.020

In the process of oilfield development, the curve fitting method and empirical formula are usually used to determine the variation of relative permeability curve of water drive reservoirs, so as to accurately simulate the oil production and water cut. When using Willhite empirical formula to fit the relationship between relative permeability and water saturation of the outlet, the fitting error is large. Especially for the relative permeability curves with small interval and sharp change, the fitting error is larger. In order to accurately characterize the changing regularity of the oil-water relative permeability curves, on the basis of the analyses of the existing formulas, Willhite empirical formula was chosen as the basic fitting formula to study the relationship between phase index and water saturation, and the oil phase and water phase index were modified. The results show that the fitting accuracy of Willhite empirical formula can be improved obviously by using binomial relation to characterize the relationship between oil-water phase index and water saturation, and the average fitting error is controlled within 8%. The improved Willhite empirical formula can characterize the changing regularity of oil and water more accurately, and has certain practicability and popularization value.