Lithologic Reservoirs

There is a large amount of remaining oil in reservoir after water flooding. How to recover remaining oil efficiently and economically is a main task in old oilfields. The remaining oil in reservoirs is by low sweep efficiency and low displacement efficiency. The low displacement efficiency of reservoirs is usually caused by residual oil in water flooded area. The residual oil is formed by Jamin effect of capillary pressure. Higher injection rate of water may overcome Jamin effect and increase the displacement efficiency of oil, however it wastes water and is not allowed by common engineering conditions. Long term water flooding can also increase the displacement efficiency of oil, but it wastes water too and has not economic benefit. Buoyance drive can increase the displacement efficiency of oil by elimination of Jamin effect, and even the displacement efficiency of oil can be raised to the final limit of 100%. For middle or high permeability reservoirs, periodical injection of water can be used to increase the displacement efficiency of oil by buoyance drive and cut down the cost of water injection for higher economic profit of oilfield development.

Several issues in studies on fine-grained sedimentary rocks

Zhou Lihong,Pu Xiugang,Deng Yuan,Chen Shiyue,Yan Jihua,Han Wenzhong

2016, Vol.28(1): 6–15 Abstract ( 552 ) PDF (791 KB) ( 813 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.002

There are huge oil and gas resources in fine-grained sedimentary rocks. Researchers pay less attention to it compared to coarser sediments. Classification, lithofacies and brittleness evaluation of fine-grained sedimentary rocks remain a relatively weak research field. Based on the X-ray diffraction data, fine-grained sedimentary rocks were divided into 12 types of rock in four main categories by means of a three-unit division system. The three units are carbonate minerals, clay minerals and felsic minerals. Meanwhile, fine-grained sedimentary rocks were named according to the concrete content of special mineral. The study of lithofacies is mainly focused on the differences in components, texture, structure, reservoir physical properties, source rock character and oil-bearing property. A great emphasis should be placed on sedimentary environment, sedimentary progress and dynamical mechanism of different lithofacies to identify advantaged lithofacies for oil and gas exploration. Brittleness of fine-grained sedimentary rocks is of vital significance to the fracturing effect. Due to the demerits of elastic parameters method and mineral constituent method which are commonly used to evaluate the brittleness of fine-grained sedimentary rocks, a new accurate and rational method should be proposed.

Characteristics and evaluation of reservoir spaces of shale gas （ oil ） in Da ’ anzhai member of Ziliujing Formation in Sichuan Basin

Zheng Rongcai,Guo Chunli,Liang Xiwen,Chang Hailiang,Lu Bingxiong

2016, Vol.28(1): 16–29 Abstract ( 524 ) PDF (2004 KB) ( 749 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.003

It is generally accepted that the Da’anzhai member of the Lower Jurassic Ziliujing Formation in Sichuan Basin is tight reservoir and has great difficulties in prospecting. Based on the description of field sections and drilling cores, analysis of thin sections and FESEM, the reservoir characteristics of Da’anzhai member were studied in combination with the data of lithofacies paleogeography, logging, porosity and permeability. It is identified that the Da’anzhai member is a typical unconventional reservoir with ultra-low porosity and permeability, and the reservoirs have fracture-dissolved pores, caves and fractures. The lake slope facies between shallow lake shell beach and semideep and deep lacustrine are favorable for reservoir development. The reservoir space is composed of different sizes of various fractures, dissolved pores, caves and dissolved fractures, grain boundary pores （fracture）, intragranular dissolved pores, intercrystalline pores and so on, as well as nm-μm level organic pores （fracture） and interlamination pores （fracture） of clay minerals. The development conditions of reservoirs can be summarized as three major elements of “layer, facies and position”. The layer element refers to the second sub-member, which has stable regional distribution, large thickness, high content of organic matters and fragile minerals in mud shale and well-developed nm-μm level organic pores and interlamination pores （fracture） of clay minerals in substrate rock. The facies element refers to the lake slope facies belt composed of interbedded black shale and shell limestones with uneven thickness, in which high-density fractures formed during the diagenesis stage due to differential compaction. The position element refers to where multi-type and multi-stage fracture and dissolution diagenesis were superposed, it is the location of relatively high quality reservoir in the tight reservoirs, and is also the “sweet spot” of the oil shale gas （oil） in Da’anzhai member.

Controlling factors of effective reservoirs in glutenite body of the fourth member of Shahejie Formation in Yong 1 block, Dongying Sag

Cao Gang,Zou Jingyun,Qu Quangong,Hou Jiagen

2016, Vol.28(1): 30–37 Abstract ( 458 ) PDF (1306 KB) ( 329 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.004

The glutenite body of the fourth member of Shahejie Formation in Yong 1 block of Dongying Sag is characterized by huge thickness, multi-period superposition and serious heterogeneity, and the development rule of effective reservoirs is unclear, which leads to poor development effect. Based on core observation, combined with rock thin sections, casting thin sections, mercury intrusion parameters and petrophysics, the main geological factors influencing its physical properties were systematically studied. The results indicate that this area is fan-delta deposition, with both onshore and underwater deposition. The physical properties of glutenite reservoir are mainly influenced by sedimentary condition and diagenesis, between which there is a relation. Sedimentary condition determines that different microfacies have different combination of lithofacies, and this difference also affects the reservoir properties. The braided channel in fan delta front is rich in pebbled sandstone facies and medium-coarse sandstone facies with better physical property, and it is favorable for in the deveolpment of effective reservoirs. On the other hand, the front fan delta has higher content of fine siltstone, with poor physical properties, so it can not serve as the development area of effective reservoirs.

Diagenesis and pore evolution of Carboniferous volcanic reservoirs in Dixi area, Kelameili Gas Field

Liu Xiaohong,Feng Mingyou,Xi Aihua,Yan Xiaorong,Wu Yu,Liu Chang

2016, Vol.28(1): 38–48 Abstract ( 502 ) PDF (2180 KB) ( 597 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.005

Characteristics of pores evolution of Carboniferous volcanic reservoirs in Dixi area, Kelameili Gas Field, are difficult to predict as the result of obviously complex diagenesis. On the basis of core observation and description, combined with the analysis of cast thin section, scanning electron microscopy, cathodoluminescence, electron microprobe, X-ray diffraction and inclusion, the diagenesis and pore evolution of volcanic reservoirs in the study area were studied. Considering the influence factors and sign of diagenesis, the diagenesis stage would be divided into four periods: condensation stage, post-magmatic hydrothermal stage, weathering and leaching stage and buried stage. Original pores and cracks were mainly formed in condensation stage and decreases drastically under the alteration and infilling of minerals in the post-magmatic hydrothermal stage, when pore porosity down to the lowest value. Weathering fragmentation, dissolution and leaching caused the formation of secondary fract ures and dissolved pores, which improves the volcanic reservoir properties. The destruction of the original pores and the formation of secondary dissolved pores are both occurred in burial diagenesis stage. Mechanical compaction affects the preservation of original pores, while infilling of minerals make the disappearance of the original pores in whole or in part, which plays a negative role to volcanic reservoirs. Benefiting from variety of secondary pores and cracks produced from the dissolution and tectonic fragmentation, the volcanic rock develops into high-quality reservoirs.

Characteristics and origin of clay minerals of Taiyuan Formation in eastern Ordos Basin

Qin Xiaoli,Li Rongxi,Xi Shengli,Li Xin

2016, Vol.28(1): 49–57 Abstract ( 441 ) PDF (1073 KB) ( 788 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.006

Taiyuan Formation in eastern Ordos Basin is typical tight sandstone reservoir, with high content of clay minerals, so it has great influence on reservoir evaluation and natural gas exploration. Based on the analysis of petrography and geochemistry, the characteristics and origin of clay minerals of sandstone reservoir of Taiyuan Formation in eastern Ordos Basin were studied. The result shows that the reservoir sandstone of Taiyuan Formation is with high content of clay minerals, which is mainly of illite and kaolinite. The illite is characterized by high content of Al2O3 and K2O and low content of FeO and MgO, and the Al2O3 content of kaolinite is more than that of typical kaolinite. Sr/Ba ratio of illite and kaolinite is less than 1. Meanwhile, illte and kaolinte are enriched in LREE, depleted in HREE, characterized by downwards sloping and some extent of δ Eu and δ Ce anomaly. Petrographical and geochemical characteristics show that illites and kaolinites are all related with hydrothermal fluid. Combined with tectonic-burial history and authigenic diagenetic minerals sequences, it is revealed that hydrothermal diagenesis began with the early Cretaceous thermal anomaly in Ordos Basin. Hydrocarbon fluid formed by thermal evolution of coal-bearing source rocks came into reservoir sandstone of Taiyuan Formation, which leads to the hydrothermal alteration to form large quantity of illtes, kaolinites and other authigenic minerals.

Diagenesis of Jurassic and its influence on reservoir properties in Niudong area, eastern Altun foreland

Wu Zhixiong,Wang Bo,Zhao Jian,Zou Kaizhen,Zhou Fei,Xiong Kun

2016, Vol.28(1): 58–64 Abstract ( 486 ) PDF (809 KB) ( 631 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.007

Based on the data of cores, cast thin sections, scanning electronic microscope and physical properties, the reservoir characteristics of Jurassic in Niudong area of Altun foreland in northern margin of Qaidam Basin were studied, and the controlling factors of reservoir development were analyzed. The results show that clastic reservoirs of Jurassic are mainly of feldspathic litharenite and lithic arkose; primary intergranular pore, dissolved pore and fracture are the main reservoir space types, and the dissolved pore is the key factor for improving the reservoir properties; diagenesis has great influence on the reservoir properties. Compaction and cementation made the reservoir properties poor, but dissolution and fracturing improved the reservoir properties.

Sedimentary environment and reservoir characteristics during depositional stage of Es 3 in Gaobei ramp region

Yang Xiaoli,Dong Xuehua,Guo Aihua,Chen Qiyan,Wang Hailong

2016, Vol.28(1): 65–71 Abstract ( 494 ) PDF (943 KB) ( 390 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.008

It is important for the prediction of effective reservoir distribution and analysis of reservoir characteristics to study the sedimentary environment of basin. Based on the study about petrology, sedimentary structure, palaeobiology, sedimentary sequence and electrofacies, the sedimentary environment of the third member of Shahejie Formation（Es3） in Gaobei ramp region of Jidong Oilfield was studied. It is revealed that the sedimentary environment of Es3 is fan delta-shallow lake facies. The evolutionary process is represent that lake was shrinking and fan delta was growing at Es33 period, lake was growing and fan delta was shrinking at Es32 period, and lake was shrink again, fan delta was growing again at Es31 period. There are two relatively independent sedimentary zones in the study area, which are caused by the uplift of central tectonic zone with NE trend in Gaoshangpu Oilfield. Meanwhile, the control role of sedimentary environment on reservoir development was discussed. It is considered that fan delta underwater distributary channel and mouth bar are the main lithosomic bodies for reservoir sand body. The distribution and development scale of reservoir sand body are controlled by the characters of fan delta development. The lithological changes on the horizontal and vertical are caused by the change of sedimentary environment. And it is the important cause of strong reservoir heterogeneity.

Fractal characterization of casting thin sections ： A case study from Kunbei area in Qaidam Basin

Chen Gengxin,Liu Yingru,Guo Ning,Wang Aiping,Chang Haiyan,Zhang Tingjing

2016, Vol.28(1): 72–76 Abstract ( 1299 ) PDF (537 KB) ( 499 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.009

The conventional analysis of pore structure of casting thin sections is mainly limited to qualitative description of the picture. Effective information of pore structure can be obtained by using the image processing technology to calculate the fractal dimensions of pores. The quantitative relations of the fractal dimensions with porosity, sedimentary microfacies and productivity index were established. The fractal dimensions represent porosity and sorting features synthetically. The larger the porosity is, the better the sorting and connectivity are, and the larger the fractal dimension will be. In the Qie 6 reservoir in Kunbei area of Qaidam Basin, the fractal dimension limit between distributary channel and river mouth bar is 1.83, which can be used to distinguish microfacies. The fractal dimension has a quantificational positive-correlation with productivity index, so it can be used to predict the productivity index. By the fractal mathematics method, the semi-quantitative characterization of the pore structure of casting thin sections can be realized.

Sequence stratigraphic framework and sedimentary facies of LSC3 of Yanchang Formation in Longdong area, Ordos Basin

Meng Hao,Zhong Dakang,Zhu Xiaomin,Liu Ziliang,Liao Jijia,Zhang Xiuqiang

2016, Vol.28(1): 77–87 Abstract ( 493 ) PDF (1292 KB) ( 548 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.010

Guided by the theories of high resolution sequence stratigraphy and modern sedimentology, sequence stratigraphic framework and depositional environment of Triassic Yanchang Formation in Longdong area of Ordos Basin were studied by making full use of outcrops, cores, logs and seismic data. Chang 81 -Chang 63 sublayer （LSC3） was defined as an integral long-term base level cycle and then divided into three mid-term base level cycle: MSC3-1, MSC3-2 and MSC3-3. MSC3-1 equals to Chang 81 depositional period, when the basin was in strong depression with mainly aggradation and retrogradation stacking pattern. MSC3-2 equals to Chang 73-Chang 72 depositional period, when the basin expanded rapidly and reached the maximum flood surface, and deposited dark shale in under-compensa-tion status. MSC3-1 equals to Chang 72-Chang 63 depositional period, when the basin began to shrink with mainly progradation stacking pattern. Sedimentary facies of Yanchang Formation in Longdong area was identified as braided river delta, meandering river delta, turbidite fan and lacustrine environments. In MSC3-1, there was mainly braided river delta with provenance of southwest. In MSC3-2, lacustrine environment occupied dominant position and there were turbidite deposits in deep lake. In MSC3-3, lake began to decrease, so both braided river delta from southwest and meandering river delta from northeast prograded strongly.

Fractal characteristics of lacustrine shale and marine shale

Wang Zhiwei,Lu Shuangfang,Wang Min,Tian Shansi

2016, Vol.28(1): 88–93 Abstract ( 502 ) PDF (540 KB) ( 685 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.011

Based on the low temperature nitrogen adsorption test of lacustrine shale in Songliao Basin, FHH model was used to discuss the relations of fractal dimension of nano-pore structure with specific surface area, average pore size and TOC content, and then compare the characteristics of fractal dimension between lacustrine shale and marine shale. The result shows that: （1） the nano-pores of the lacustrine shale and marine shale have obvious fractal characteristics, and the large pore （5-100 nm）, with a bigger fractal dimension, shows a higher degree of complexity than the small pore （less than 5 nm）; （2）the nano-pore structure of lacustrine shale is relatively simple, and its fractal dimension is less than that of the marine shale; （3）the fractal dimension is positively correlated with TOC content, and the TOC of lacustrine shale has weaker influence on fractal dimension; （4）the fractal dimension （D1） of lacustrine shale has a significant linear relationship with the average pore size, which shows that D1 can reflect the pore structure features of lacustrine shale, while the fractal dimension （D2） of marine shale has an exponential relationship with the specific surface area, which shows that D2 can reflect the pore specific surface area characteristics of marine shale.

Seismic prediction method of “ sweet ” reservoir in middle-deep zone: A case study from Wenchang A sag, western Pearl River Mouth Basin

Pan Guangchao,Zhou Jiaxiong,Han Guangming,Zhu Peiyuan,Liu Feng

2016, Vol.28(1): 94–100 Abstract ( 497 ) PDF (1405 KB) ( 654 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.012

Influenced by buried depth and diagenetic compaction, low porosity and low permeability reservoir developed in Paleogene in Wenchang A sag of the western Pearl River Mouth Basin. The seismic reflection characteristics were characterized by poor continuity and low signal-to-noise ratio, so it is difficult to carry out reservoir prediction and hydrocarbon detection. To solve this fundamental problem that conventional geophysical method is difficult to achieve an effective application due to the general overlay of rock physics parameters, the frequency dividing attribute technique of advantage trace was applied to qualitatively predict low porosity and low permeability reservoir by avoiding geophysical technology depending on logging petrophysical analysis results, which depends on totally seismic data. Meanwhile, based on logging petrophysical analysis results, prestack inversion based on curve reconstruction was used to semiquantitatively predict low porosity and low permeability reservoir. Through test, both the two methods have a certain effect for predicting low porosity and low permeability reservoir, so they are worthy of further promotion.

Numerical simulation fitting technology ： A case study from Longhupao Oilfield

Zhou Zhijun,Xue Jianglong,Zhao Libin

2016, Vol.28(1): 101–105 Abstract ( 489 ) PDF (530 KB) ( 702 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.013

Residual oil distribution study is the basis of subsequent rolling development of oilfield, and the accuracy of numerical simulation is the key for the analysis of residual oil distribution rule. Longhupao Oilfield is low permeability reservoirs controlled by lithology and structure, belonging to coastal shallow-lake facies and delta front deposition. Aimed at the geology, structure and sedimentary characteristics of Longhupao Oilfield, the reserves was fitted with virtual wells technology, PETREL-RE technology, segmentation and integration technology, partition fitting technology, endpoint calibration in stages and phase spreads. The fitting precision reached 91.6%, and the block geological reserves fitted precision error is lower than 5%. The residual distribution rule in planeand vertical was obtained, which can guide the further development of oilfield.

Influence of ground stress on resistivity logging response in tight sandstone reservoir

Chen Xiaoyu,Zhang Chengguang,Zhu Lei,Tang Jun

2016, Vol.28(1): 106–110 Abstract ( 490 ) PDF (363 KB) ( 515 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.014

Kelasu structural zone in Kuqa Depression belongs to tight sandstone reservoir which is characterized by complex formation conditions and large buried depth. Taking into account the influence of lithology, extrusion stress and other factors, it is difficult to accurately reflect the formation fluid properties by resistivity logging response.Based on studying the influence of magnitude and direction of the ground stress on the resistivity response of reservoir rocks in this area, combined with logging data, the crossplot of formation resistivity and ground stress was plotted, and the statistical data of the direction of horizontal principal stress and the formation fracture orientation in different well fields were sorted by using FMI data. The results show that with the increase of horizontal principal stress difference, the formation resistivity is exponential increasing. The correlation between the formation resistivity and the horizontal principal stress difference is better when the included angle between the direction of horizontal principal stress and the formation fracture orientation is smaller, and the correlation gets worse with the included angle increasing

Elastic and electrical properties of shales from Qiongzhusi and Longmaxi Formation

Dou Chunxia,Tang Xingong,Xiang Kui,Sun Bin,Yan Liangjun

2016, Vol.28(1): 111–116 Abstract ( 472 ) PDF (737 KB) ( 566 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.015

In order to study the elastic properties and complex resistivity of shale of Lower Cambrian Qiongzhusi Formation and Lower Silurian Longmaxi Formation in Sichuan Basin, crop samples were collected from southern Sichuan Basin,western Hubei and eastern Chongqing. Based on AutoScan-Ⅱ platform, planar scanning was conducted to shale samples to obtain the petrophysical parameters such as permeability and velocity. The result shows that the velocities of p-wave and S-wave are negatively correlated with permeability, and Young ’ s modulus and Poisson ’ s ratio are in line with shale standards, with strong compressibility. The values of four parameters of complex resistivity of shale in Longmaxi Formation decreased with the ascending of salinity in different degrees, but have less influence on dispersion curve. When the frequency is less than 10 kHz, phase angle and heterogeneous resistivity have a positive correlation with the slope of amplitude dispersion curve of complex resistivity. Through the comparison of dispersion property of different samples, it is considered that polarization effect of pyrite particles is the main factors for significant dispersion of heterogeneous resistivity and phase angle in Shizhu area of Chongqing. Because pyrite is the sign of rich organic matters, phase angle and hetero-geneous resistivity can be used as important indicators to detect target in Lower Silurian Longmaxi Formation.

A new model for calculating effective permeability in low permeability reservoir: A case study of low permeability marine sediments reservoir in the Pearl River Mouth Basin

Ma Yongxin,Lei Xiao,Zhang Qiaoliang,Meng Lingqiang

2016, Vol.28(1): 117–122 Abstract ( 519 ) PDF (429 KB) ( 511 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.016

Effective permeability is one of the key parameters affecting low permeability reservoir development. Its methods are usually influenced by production or test precision, and generally require a specific set of processes. To solve this problem, a research is made on how to calculate effective permeability by use of the easily obtained data. Accordingly, based on the principle of equivalent flow resistance, combined Darcy formula with Poiseuille formula, a new calculation model for calculating effective permeability in low permeability reservoir was established by considering water film and introducing the concept of the effective pore throat radius. The effective pore throat radius is the difference value between the original pore throat radius and the water film thickness. The sensitivity analysis shows that the pore throat radius has the same order of magnitude with water film thickness in low permeability reservoirs.Therefore, the water film has a great impact on the effective permeability. This new model was used to calculate the permeability of A4H1 well in Wenchang 13-1 oilfield in the Pearl River Mouth Basin, the South China Sea. The permeability calculated by the new model is similar to the result of well test analysis. It is shown that the new model is reliable and can provide foundation for productivity evaluation and dynamic analysis in low permeability reservoir,and it has a favorable application prospect.

Flow model and well test curves for quadruple-media reservoirs

Jia Yonglu,Sun Gaofei,Nie Renshi,Li Jianming,Li Haike

2016, Vol.28(1): 123–127 Abstract ( 604 ) PDF (0 KB) ( 404 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.017

For fractured-vuggy quadruple-media carbonate reservoirs with micro-fractures and fractures, the percolation mechanism of large-scale fractures is inconsistent from the small-scale fractures. Using conventional multiple media models to explain quadruple-media reservoirs is inappropriate. A quadruple-media physical and mathematical model based on matrix, micro-fractures, vugs and fractures was established. By means of Laplace transformation and numerical inversion of Stehfest, the real space solution was obtained, and well test curves were drawn up. The result shows that three concaves tend to be present in the pressure derivative curve of the quardrule-media reservoir, of which the amplitude is affected by the interporosity flow coefficient and capacitance coefficient. The width and depth of the concaves are influenced by capacitance coefficient, and the timing and the ampli-tude of concave are affected by interporosity flow coefficient. More parameters present in the quadruple-media reservoirs well testing curves, and curves are more sensitive to the change of parameters. It is suitable to use the quadruple-media well testing models to interpret fractured-vuggy carbonate reservoirs with fractures and micro-fractures

Research status of CO ₂ flooding and its seismic monitoring technologies

Li Jun,Zhang Junhua,Tan Mingyou,Cui Shiling,Qu Zhipeng,Yu Jingqiang

2016, Vol.28(1): 128–134 Abstract ( 540 ) PDF (724 KB) ( 562 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.018

CO 2 flooding is a special tertiary oil recovery technology which injects the liquid CO 2 to subsurface reservoir by gas-injection wells, and then drives the oil and gas to producing wells. This technology can greatly enhanced oil recovery, and storage the CO 2 and reduce carbon emission. It is favorable both for environmental protection and oilfield production. Combining research project, based on a mass of literatures, this paper explained the fundamental principle of CO 2 flooding, summarized the development of CO 2 flooding ， pointed out the main contents of rock physics fundamental analysis, and gave the principle and implementation steps of the displacement simulation experiment.This paper focused on discussing the major monitoring technologies, such as 4D seismic, borehole seismology, microseismic, AVO and VSP ， which could provide basis for the application of CO 2 flooding.

Von Bertalanffy model for water cut prediction in water flood field

Chen Guofei,Tang Hai,Tang Cong,Liang Yi

2016, Vol.28(1): 135–138 Abstract ( 541 ) PDF (276 KB) ( 532 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2016.01.019

Based on the changing law of water cut in water flood field, Von Bertalanffy model for predicting biological growth was used to predict water cut, and the limit water cut is 1. Based on the actual data of oilfield, the value of model constant was obtained by maximum linear correlation coefficient, and a new model for predicting water cut change with developing time in water flood field. This model was validated by actual water cut value from Shengtuo Oilfield and Shuanghe Oilfield. The result shows that the relative errors of the water cut in the two fields are 4.69% and 1.12% respectively. The prediction accuracy of this model is high, therefore, it can be used to predict water cut of oilfield and guide development of water flood field.