Table of Content

01 June 2015, Volume 37 Issue 3

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A New Experimental Apparatus for Fracturing Shale Gas Reservoir to
Enhance Permeability with Supercritical Carbon Dioxide

Xian Xuefu1，2*, Yin Hong1，2, Zhou Junping1，2, Jiang Yongdong1，2, Zhang Daochuan1，2

2015, 37(3):  1-8.  DOI: 10.11885/j.issn.1674-5086.2015.02.08.01

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The process of hydraulic fracturing of shale gas reservoir will consume large amounts of water. Duo to the high density
and diffusivity of gas，supercritical CO2 can replace water as fracturing fluid，showing a very good application prospects.
Based on this，we proposed increasing the permeability of shale gas reservoir with supercritical CO2 fracturing and independently
developed experimental device. The device is mainly composed of the CO2 booster system，triaxial loading and control
system，oil bath temperature control system，acoustic emission system，and its axial pressure control range is 0∼100 MPa，
confining pressure control range is 0∼25 MPa，maximum heating temperature is 100 ?C，specimen size is 100 mm×200 mm.
The apparatus can precisely control CO2 phase and acquire data of shale rupture stress-strain，pressure，temperature，acoustic
emission signals，and can get supercritical CO2-induced shale gas reservoir permeability dynamics of cracking shale process in
multi-field（stress，temperature，pressure）coupling conditions，providing experimental platform for supercritical CO2 fracturing
increasing shale gas reservoir permeability mechanism study.

Production Analysis of Composite Model of Five Regions for Fractured
Horizontal Wells in Shale Gas Reservoirs

Yin Hongjun1，2, Zhao Ermeng1，2, Fu Jing1，2，3, Wang Lei1，2, Zhong Huiying1，2*

2015, 37(3):  9-16.  DOI: 10.11885/j.issn.1674-5086.2015.03.04.07

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Horizontal wells with hydraulic fracturing technology have become an efficient way to produce from shale gas
reservoir. Therefore，a composite mathematical model of five regions for fractured horizontal wells in shale gas reservoirs is
established in this paper with consideration of desorption，diffusion and percolation characteristics. Then the analytical solution
is deduced in Laplace space. Based on the Stehfest numerical inversion algorithms，the analytical solution of dimensionless
production in real space is obtained，and dimensional production decline curve is plotted and analyzed. The results show that
decline curve can be divided into six different flow regimes according to the characteristics；interporosity flow coefficient
mainly influences the shape of desorption and later stages；hydraulic fracture conductivity mainly influences the shape of early
linear flow stage，permeability of the stimulated region mainly influences the shape of mid-to late stage. The greater the width
of stimulated region is，the higher the production is，and the greater the permeability is，the higher the production is，because
the fracture network after being hydraulic fractured is connected well with natural fractures. The results obtained can provide
scientific basis for reasonable analysis to production analysis for fractured horizontal wells in shale gas reservoirs.

A New Productivity Prediction Method for Fractured Horizontal Wells in
Shale Gas Reservoirs

Sang Yu1，2*, Yang Shenglai1, Guo Xiaozhe1, Cheng Hao1

2015, 37(3):  17-24.  DOI: 10.11885/j.issn.1674-5086.2014.10.08.02

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Horizontal wells with hydraulic fracturing are going to be the main method of shale gas production. Fractured shale
gas reservoirs have a variety of seepage patterns due to lots of the natural or artificial fracture and nano-scale pore. Establishment
and solution of percolation mathematical model has a strong theoretical and practical value. Equivalent simplified three linear
flow model is constructed，which includes matrix space linear seepage with desorption and adsorption，mainly equivalent natural
fracture of fracture network space linear seepage，linear seepage within the main fracture. Under the polar coordinate space
and the Laplace space，we established mathematical models for triple seepage model，and solved them. Finally，we developed
single well productivity formula of gas reservoir and bottom hole pressure formula. By applying the established model and the
analytical solution，a fractured horizontal well productivity has be calculated. Compared with the actual production，the result
shows that analytical solution based on the model can forecast production capacity.

New Method to Study the Skin Factor of Horizontal Gas-well
After Staged Acidizing

Li Xiaoping1*, Yan Ningping1，2, Yuan Lin3, Zhang Liehui1

2015, 37(3):  25-30.  DOI: 10.11885/j.issn.1674-5086.2015.03.04.01

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Horizontal well staged acidizing with packer has been an important stimulation treatment to achieve uniform acidizing
in anisotropic reservoir，so the study of skin factor after staged acidizing is of great importance. Based on the elliptic
damage zone near the horizontal gas well，the authors take by into consideration the uniform treatment by acids and influence
of residual acid back flow on gas flow in the reservoir，and dividing the flow problem of composition area in elliptic damage
zone into three flow problems in homogeneous region，taking advantage of resistance superposition theory，we eventually get a
new method to calculate the skin factor of horizontal gas well after staged acidizing. The case study shows the local skin factor
of horizontal gas well after staged acidizing becomes smaller from the heel to toe-end along the direction of wellbore；it also
decreases with the increase of acidifying radius and permeability of acidizing zone，but increases with the increase of maximum
immersion radius. The study in this paper will offer an new approach to the calculation of the skin factor of horizontal gas well
after acidizing.

Experimental Study on Permeability Evolution in
Propped Shale Fracture

Hou Lei1*, Derek Elsworth2, Sun Baojiang1, Wang Jintang1

2015, 37(3):  31-37.  DOI: 10.11885/j.issn.1674-5086.2015.03.10.03

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In the process of shale gas fracturing exploitation，the permeability of propped shale fracture is one of the key
factors that affect the fracture conductivity. This work focuses on the effects of swelling and embedment on permeability in
propped shale using experimental method. The Pulse test method was used to measure the permeability of adsorbed gas and
non-adsorbed gas. The permeability of He，which is a non-adsorbing gas，in both granite and shale was measured for references.
The reduction of permeability in shale is caused by the existence of proppant embedment. The“U shape”feature is observed in
CO2 permeability curve，which indicates that the swelling also has a significant effect on the permeability in shale. Compared
with the permeability curve of He，the CO2 permeability is even lower and achieves the minimum value at the pressure condition
around the Langmuir pressure.

Diffusion Seepage Model for Fractured Horizontal Well
in Shale Gas Reservoir

Guo Xiaozhe1*, Zhou Changsha2

2015, 37(3):  38-44.  DOI: 10.11885/j.issn.1674-5086.2014.11.19.01

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To determine the effect of gas diffusion affection in the shale gas reservoirs with the desorption-adsorption and
nano-scale pore on fractured horizontal well productivity analysis，we established the seepage mathematic model and analyzed
quantitatively the production. In the study，we used the three linear seepage mechanism，Knudsen diffusion mechanism and
diffusion of the added value of permeability formula to draw the relation chart of Knudsen number under different pore diameters
with reservoir pressure，and derived the single well productivity equation to be used for the actual production prediction.
Analysis of the diffusion of shale gas reservoir was carried out in 3 aspects，which are the pore size，reservoir pressure and gas
reservoir depth，and reference is given to consider the diffusion of various indicators. Results show that under the condition of
the reservoir pressure，the smaller the porosity of the reservoir，the greater the influence of diffusion effect is on capacity；and
for large pore reservoir，when the bottom hole pressure is lower than the threshold of the calculated in the model，the diffusion
effect should not be ignored.

Multistage Fractured Horizontal Well Numerical Simulation and
Application for Tight Oil Reservoir

Jiang Ruizhong, Xu Jianchun*, Fu Jianbin

2015, 37(3):  45-52.  DOI: 10.11885/j.issn.1674-5086.2014.12.21.02

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With further progress of oilfield development all over the world，more and more tight oil reservoirs are being put in
production. This paper established a mathematical model of multistage fracturing horizontal wells，and the multistage fractured
horizontal well numerical simulation software was developed. The new software is verified by using the commercial software
Eclipse. We matched the actual production data using this new software. Analysis was made about the fracture conductivity，
SRV volume，SRV permeability，nonlinear coefficients，and initial pressure. Results show that the new software can effectively
simulate multistage fracturing horizontal wells in the tight oil reservoir and reflect the nonlinear flow features. In order to
increase productivity，the fracture flow capacity，SRV volume，and SRV permeability should be appropriately increased. On
the other hand，the non-Darcy flow decreases the well productivity.

Transient Pressure Analysis of Inclined Fracture in Tight Gas Reservoirs

Jia Pin1*, Cheng Linsong1, Li Caiyun2, Huang Shijun1, Liu Hongjun1

2015, 37(3):  53-62.  DOI: 10.11885/j.issn.1674-5086.2014.11.19.06

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In view of the inclined hydraulic fracture formed by slant well fracturing，the numerical model for fracture flow was
derived based on the discrete fracture segments and the analytical model for reservoir flow was established by combining slant
plane source function and the superposition principle. A semianalytical model for inclined fracture was developed by coupling
the numerical fracture flow model and the analytical reservoir flow model dynamically in this paper. The flow regimes were
defined，the corresponding pressure or derivate analytical equations were derived and the effect of reservoir and fracture parameters
on transient responses was investigated. The results show that there are five flow regimes including fracture/formation
bilinear flow，formation linear flow，early radial flow，pseudo-compound linear flow and later pseudo-radial flow for inclined
fracture in the absence of the effect of wellbore storage. The wellbore afterflow caused by wellbore storage may mask the fracture/
formation bilinear flow. The period of the effect of the inclination angle and permeability anisotropy on transient pressure
is very long，which will last to later pseudo-radial flow. The existence and duration of fracture/formation bilinear flow and
formation linear flow is only determined by dimensionless fracture conductivity. Finally，a field test in fractured directional
well from Suliger Gas Field verified the validity of the model.

Simulation of Gas Flow in Nano-scale Pores of Shale Gas Deposits

Duan Yonggang1*, Cao Tingkuang1, Yang Xiaoying1, Zhang Ying2, Wu Guiping1

2015, 37(3):  63-68.  DOI: 10.11885/j.issn.1674-5086.2015.03.16.03

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As an important unconventional natural gas resources，shale gas has aroused wide concern. Shale-gas deposits are
abundant in nano-scale pores. However，the study on the gas flow mechanism is still inadequate，which restricts the efficient
development of shale gas reservoirs. For nanometer pores，a novel single component mathematical model of shale gas which
takes into consideration the adsorption-desorption of shale gas，the surface diffusion of the adsorbed phase，Darcy flow，and
slip flow as well as Knudsen diffusion is proposed. The simulation results show that for shale matrix containing a large number
of nano-scale pores，methane adsorbed on the pore，the seepage flow and Knudsen diffusion all exert influences on gas flow and
make the apparent permeability much higher than absolute permeability. The smaller the pore size and the lower the pressure
is，the larger the difference between the apparent permeability and absolute permeability is. The study of the impact of various
transport mechanisms on gas flow is helpful to understand the process of shale gas production and to guide the development of
shale gas reservoir.

Research Progress of Seepage Mechanics in Rock Mass
Affected by Mining

Chen Zhanqing, Yu Bangyong*

2015, 37(3):  69-76.  DOI: 10.11885/j.issn.1674-5086.2015.03.05.06

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Seepage mechanics in rock mass affected by mining（SMRMAM）is a discipline which is based on the seepage
instability hypothesis. In this paper，some basic information about SMRMAM，the engineering background and foundations
of mathematics，several research directions，are presented. The research progress is introduced in three aspects，experiments，
nonlinear behavior and complex behavior. Finally，the development tendency of SMRMAM is prospected. SMRMAM has
a great potential for development. With the changing of energy structure，the environmental requirements for coal mining
will be more stringent，and the challenge for SMRMAM will be more severe. As a consequence，in the field of SMRMAM，
the experimental subjects will be further expanded；the modern mathematics theory will get more widely used；the study on
complex behavior will further；the application of qualitative theory on differential dynamic system will develop SMRMAM
into discipline with distinct characteristic；the study on SMRMAM，with boundary conditions changing over time，will prompt
SMRMAM to mature.

Mechanism and Control Methods of the Working Fluid Damages in
Fractured Tight Reservoirs

Kang Yili1*, Zhang Dujie1, You Lijun1, Xu Chengyuan1, Yu Haifeng2

2015, 37(3):  77-84.  DOI: 10.11885/j.issn.1674-5086.2015.03.16.04

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Fractured tight gas reservoirs is characteristic of developed natural fractures which lead to lost circulation of working
fluid and induce formation damage. In order to study the damage mechanism of working fluids indifferent operations and to find
out prevention strategies，based on the Xujiahe formation and Zhenzhuchong formation in the Jiulongshan Structure in western
Sichuan Basin which is a fractured tight gas reservoir，we carried out the damage evaluation experiments of drill-in fluid and
the working fluids order contact. The experimental results show that the damage grades of blocks induced by the filtrate of
drill-in fluid，the drill-in fluid and the drill-in fluid solids range from medium to intensely and reduce gradually；the average
permeability dynamic damage grade of the fractured samples is intense；the working fluid order contact would strengthen the
damage degree. The analysis of the damage mechanism of different operations shows that water phase trapping，solid plugging
are the major mechanism of working fluids damage；the damage induced by different working fluid would be superimposed，
and increased the damage range. Based on the results，we constructed the damage patterns of lost circulation，and suggest using
the modified shielding plugging drill-in fluid to improve sealing ability and change the rock wettability can prevent the working
fluid damage effectively. Identification of damage range with lost circulation data can provide guidance for acidizing.

Study on Occurrence Feature of Fluid and Effective Development in
Tight Sandstone Oil Reservoir

Yang Zhengming*, Luo Yutian, He Ying, Guo Hekun, Zhao Yuji

2015, 37(3):  85-92.  DOI: 10.11885/j.issn.1674-5086.2015.03.07.04

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The occurrence feature of fluid in tight oil cores with different permeability was studied using nuclear magnetic
resonance（NMR）and centrifuge. The results indicate that the low limit of throat radius for movable fluid in tight oil reservoir
is 0.05 µm；the fluid percentage controlled by the nanometer throat radius rise；sharply as permeability decreases，the movable
fluid percentage controlled by the nanometer throat radius rises gradually as permeability decrease，the fluid and movable fluid
percentage which was controlled by the micron throat radius was a sharp drop as permeability decreases；the fluid and movable
fluid percentage controlled by the submicron throat radius first increases and then decreases as permeability decreases. Based
on the above findings，the effect of different wells combinations and different development scheme on effective development
was studied with reservoir numerical simulation technique. The results reveal that development effect of CO2 injection for
replenishing energy in staged fracturing horizontal wells is the best，and water injection takes second place，while depletion
gets the worst effect.

Predicting Models for Heating Area of Cyclic Steam Stimulation in
Horizontal Well of Thin Interbedded Reservoirs

Shi Lihua1*, Zhao Xisen1, Guo Shangping2, Wang Yan1, Lu Chao3

2015, 37(3):  93-97.  DOI: 10.11885/j.issn.1674-5086.2015.03.19.01

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Accurately predicting period of heating steam stimulation area of horizontal well is very important for the development
of heavy oil reservoir. The current forecast radius formula contains a double integral，which makes the calculating process
complicated and time consuming. In this paper，by Marx Langenheim vertical well heating range formula as the theoretical
basis，and on the basis of in-depth study，we simplified calculation of heating model，and established a simplified model of
horizontal well cyclic steam heating，which is with simple relationship type，easy to solve and convenient to apply. Oilfield
actual parameters are calculated and analyzed，and the results show that using the improved formula can get relatively accurate
result，which verifies the accuracy of the formula.

Temperature Sensitivity Experiment on Ultra-low Permeability
Sandstone Reservoir

Meng Xuangang*, Guo Xiao, Gao Tao

2015, 37(3):  98-102.  DOI: 10.11885/j.issn.1674-5086.2015.01.26.03

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The influence of temperature on the permeability of sandstone is controversial，and there are only a few studies on the
effect of temperature on permeability sensitivity in sandstone reservoirs. In this paper，experiment of effect of temperature on
permeability and stress sensitivity is conducted on a core from an ultra-low permeability reservoir，Yanchang Oilfield. In door
physical simulation is taken as study method. Results show that，under low confining pressure（3.0 MPa），when temperature
increases from 30 ?C to 150 ?C，permeability decreases by 13.47%，and stress sensitivity increases by 3.8%. When confining
pressure is 20.0 MPa，permeability stays unchanged when temperature increases from 30 ?C to 150 ?C. Stress sensitivity is
stronger under higher temperature.

An Experimental Study on Reservoir Damage Mechanisms of DF1 1
Low Permeability Loose Sandstone Gas Reservoir

Tang Guangrong1*, Zhao Feng2, Li Yuelin1

2015, 37(3):  103-108.  DOI: 10.11885/j.issn.1674-5086.2014.07.03.01

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Low permeability loose sandstone gas reservoir is characteristic of such as small pore throat size，high sensitive
mineral content，high capillary pressure，loose reservoir cementing at the same time. In the process of drilling and completion，
the formation damage is easy to occur. In this paper，taking the second sequence of Yinggehai formation which is low
permeability loose sandstone gas reservoir of DF1 1 gas field in the south China sea as the research object，according to the
characteristics of gas reservoir and combining the field construction technological process，we improved the working fluids
damage evaluating methods of the oil and nature gas industrial standard，and systematically evaluated the main damage mechanisms
of low permeability loose sandstone gas reservoir. The research results indicate that during drilling and completion，
the organic solid plugging and water blocking are the main damage mechanisms of the PRD drilling and completion fluids；the
damage degree of fine particles migration during production is weak. The results gotten from the improved evaluating methods
conform to the field practice better. 5 percent of big size rigid plugging particle is suggested to mix into the PRD drilling fluid，
to reduce the invasion degree into gas reservoir of the organic solid phase，and liquid phase. Adding 6% of gel breaker amount
in the completion fluid，the efficiency of gel breaking will be improved.

Upscaling Algorithm for Heterogeneous Porous Media by Using
the Finite Analytic Method

Liu Zhifan*, Liu Zhifeng, Wang Xiaohong

2015, 37(3):  109-114.  DOI: 10.11885/j.issn.1674-5086.2015.03.04.06

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An algorithm for solving upscaled tensor permeability by using the finite analytic method is proposed，which is
suitable for the flow field described by the linear Darcy′s law. Adoptingthe double periodic boundary condition proposed by
Durlofsky，the proposed algorithm can provide the upscaled full tensor permeability with high efficiency. Only with 2×2 or
3×3 subdivisions，the proposed algorithm can provide rather accurate solutions，where the convergent speed is independent of
the permeability heterogeneity. In contrast，when using the traditional numerical schemes to simulate flow through a strong
heterogeneous porous medium，the refinement ratio for the grid cell needs to increase dramatically to get an accurate result.

A Study on the Prediction Method of Well-testing Curve Type of New Wells

Liu Wendong1*, Liu Xingquan2

2015, 37(3):  115-121.  DOI: 10.11885/j.issn.1674-5086.2015.02.05.02

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When deploying monitoring well and setting appropriate time for well test，accurate prediction of well logging curve
types undoubtedly has important significance. Based on the principle of multiple discriminant analysis we combine the reality
well test curve types and the well logging and production performance data of oilfield monitored wells，we optimize the well and
reservoir parameters through repeated screening parameters. In the end，we established a model considering reservoir thickness，
moisture content，logging permeability and the oil production. The result of the error rates is 9.09% and the coincidence rate
is 85.7%，which means the model can be used in anticipation for logging curve type. This method provides a scientific and
reasonable guidance for workers to formulate reasonable testing time，optimize the monitoring well and improve the quality of
monitoring results.

Adjustment Technology of Well Pattern in Gudong No.2 Block Ng5 Based
on Segmentation Variable Streamline Method

Gao Jutong*

2015, 37(3):  122-128.  DOI: 10.11885/j.issn.1674-5086.2015.03.07.05

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In view of No.2 Block Ng5 adopted water flooding after 2011 in the later development period，which brought many
problems，including the well casing damage resulted in imperfect well pattern and large reserves out of control，prominent
interlayer contradictions，relatively fixed well pattern，ineffective exploitation of plane interlayer remaining oil，low oil recovery
and so on. Therefore，in the study area we to implement segmentation variable flow pattern adjustment. In the study，we can
adjust well pattern and transform streamline by subdivision of strata，modifying layer of old wells and drilling new wells.
According to study the remaining oil by modeling and numerical simulation technology，we find the remaining oil in the shunt
line and between the oil wells is still adequate and has further potential to improve oil recovery.

Experimental Study on Oil Displacement of Aqueous Dispersion System of
Nano/Micron-sized Polymer Particles in Heterogeneous Reservoir

Long Yunqian1*, Zhu Weiyao2, Huang Xiaohe3, Wu Junjie1, Song Fuquan3

2015, 37(3):  129-137.  DOI: 10.11885/j.issn.1674-5086.2014.12.22.02

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In order to reveal deeply the effects of heterogeneity to oil displacement effect of aqueous dispersion system of
nano/micron-sized polymer particles in low permeability reservoir，heterogeneous oil displacement experiments of nano/micronsized
polymer particle were conducted by plane sandpack model and cores series and parallel combination experiment technology.
The influences of vertical heterogeneity，lateral heterogeneity and permeability ratio on oil displacement effect were
analyzed. The experimental results of plane sandpack models show aqueous dispersion system of nano/micron-sized polymer
particles reduces vertical heterogeneity of low permeability reservoir more effectively，with 9.83% higher recovery rate than in
the lateral heterogeneous models. The experimental results of core combination models show the recovery rates improved by
the aqueous dispersion system of nano/micron-sized polymer particles in cores series and parallel combination models increase
gradually with increasing permeability ratio，which have a growth of 6.65% in the core is series ones and a growth of 9.48% in
the parallel combination ones. The bigger the permeability ratio is，the greater the difference of fluid productions in low and
high permeability cores is. After the aqueous dispersion system of nano/micron-sized polymer particles injected into cores，the
fluid productions reduce gradually in high permeability cores and increase by degrees in low permeability cores.

Researches on the Pore Permeability of Core Sample Based on 3D
Micro-CT Images and Pore-scale Structured Element Models

Song Rui1, Liu Jianjun1，2*, Li Guang1

2015, 37(3):  138-145.  DOI: 10.11885/j.issn.1674-5086.2015.04.03.03

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Pore structure feature of rocks is one of the major factors which affect the reservoir storage capacity of fluids（oil，
gas and water）and the exploitation of oil and gas resources. A better understanding of pore structure characteristics is of great
significance in increasing oil and gas production and improving recovery efficiency. Based on the microscopic images of real
rocks，microscopic pore structure models are able to reproduce the complex structure of natural rock pores. On the basis of
three-dimensional CT image and segmentation technology，data of the rock porosity and pore size distribution are obtained in
this paper by Matlab programming. Furthermore，a structured grid model which reflects the pore morphology of the original
rock sample is constructed. Based on that，the permeability of the rock sample is obtained. The simulation results of the porosity
and permeability agree well with the experimental results.

Feasibility Study of Polymer Flooding in Widuri Oilfield

Tang Donglin*, Sun Pengxiao, Meng Weibin, Qian Shenhua

2015, 37(3):  146-151.  DOI: 10.11885/j.issn.1674-5086.2013.10.16.06

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Aiming at the conditions of high water cut，poor water injection effect of the sand body and the decline of output，
we study the feasibility of polymer flooding in Widuri Oilfield in the paper. The polymer system and the well injection group
are selected with the method of core test and numerical simulation. The performance evaluation experiment proves the selected
polymeric system to meet the requirement of the oilfield polymer displacement，and the ultimate recovery can be enhanced
by 21%∼25% after the polymer flooding，which is a desirable displacement effect. With the help of the numerical simulation
results，the displacement project is designed，and the ultimate recoverable reserve by water flooding is 197.9×104 bbl，but
for polymer flooding is 221.5×104 bbl，which can enhance the recovery of 6.36%. Widuri Field is successfully supported by
polymer flooding，decreasing oil production decline rates，and effectively improving oil recovery rates，and hence yielding
substantial economic benefits for CNOOC Southeast Sumatra PSC.

Time and Space Change of Permeability for Rock Mass in Dam
Abutment High Slopes of Hydropower Engineering

Li Hong1*, Tian Hongyuan1, Liu Jianjun2

2015, 37(3):  152-159.  DOI: 10.11885/j.issn.1674-5086.2015.03.05.03

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With regard to the seepage characteristics of the fractured rock mass in the dam abutment high-steep slopes for
large scale hydraulic and hydropower engineering in Southwest China，the experimental，theoretical models and numerical
simulation study results about its time and space features in the distribution changes due to natural and construction process
such as geological history，blasting excavation，support，impounding and flood discharge，rainfall，etc. are introduced. The
current research state and progress is assessed. The probing efforts and contributions from researchers in this field，who desire
to put this problem forward from qualitative to quantitative stage，are shown in the paper. It is proposed that in aspects of
the mechanism like stress-strain whole process，intensive unloading，multiple field coupling，anchorage and shotcrete，scale
effect，three dimensional pattern and monitoring in depth，further study is urgently needed in order to make the regularity clear
about the evolution of permeability of fracture rock mass in slopes along the damage and failure surrounding cracks，joints and
faults.

Effect of Gob Air Leakage and Residual Methane Emission on
Mining Stope Flow Field

Pei Guihong*, Leng Jing, Liu Yuxue, Pan Jie

2015, 37(3):  160-167.  DOI: 10.11885/j.issn.1674-5086.2015.01.22.01

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Based on the investigation of the literatures at home and abroad，and according to the seepage mechanics，rock
mechanics，mining engineering and other multi-disciplinary cross，we establish the coal mine goaf gas flow mathematical
model with the method of combining theoretical analysis and numerical calculation. By the CFD technology，we study the
leakage distribution and gas concentration field distribution of gas concentration and velocity about wind in working face，the
scope of dissolute concentration in goaf and between goaf and working face，the relationship between goaf air leakage and air
volume in working face，the decay law of air leakage rate velocity along goaf，and determine that the highest concentration of
gas is return corner in entire working face，and the highest concentration of gas in goaf is also highest concentration of gas in
entire scope. Through the simulation of different air supply volume，we describe the migration trend of gas concentration，the
relationship between the concentration of gas and air flow rate of return corner，and also find that the gas concentration gradient
is bigger in the air side，increasing the air supply volume can decrease the concentration of gas in return corner，but increases
the risk of spontaneous combustion of remaining coal. This paper reveals the goaf air leakage and the residual coal gas emission
of the influence law of stope gas flow.

Prediction of Groundwater in Minqin Oasis Based on 3D Numerical Model
Including Unconfined Aquifer and Confined Aquifer

He Xiangli*, Ye Mao, Jiang Yutong

2015, 37(3):  168-173.  DOI: 10.11885/j.issn.1674-5086.2015.03.18.03

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Based on the latest water-level data in 2011 and 2012，a groundwater numerical model including unconfined aquifer
and confined aquifer for Minqin oasis was established with Feflow software，which can simulate the regional groundwater
changes under transient conditions. The numerical model was used to predict future changes in groundwater level in the next
five years to ten years. The result indicates that a series of comprehensive measures have curbed the trend of drawdown of
groundwater level effectively under current water resources management conditions. But in the next 5 to 10 years，groundwater
levels in the Minqin oasis will be in a continuous drawdown trend with low rate. The current groundwater funnel areas in the
upstream district expand，but those distributions in the downstream district shrinks on account of the complement of water form
Qingtu Lake. But as groundwater depth in the study area increases，a new groundwater funnel turns up in Hongshaliang village.
In addition，the local plant cannot survive until the groundwater depth is less than 15 meters. The percentage of the area where
groundwater depth is less than 15 decreases year by year and area in which groundwater depth is less than 10 meters is shrinkage
on a large scale.

Experimental Research on Crack Extension and Indoor Rainfall
Infiltration of Nanyang Expansive Soil

Wang Weiwei1*, Kong Lingwei2, Zang Meng2, Zhang Chuancheng1

2015, 37(3):  174-184.  DOI: 10.11885/j.issn.1674-5086.2015.03.04.11

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The crack of expansive soil occurs when the moisture content reduces，which brings great harm to the project.
Fissured expansive soil seepage under rainfall is a typical engineering problem. In this paper，6 identical remolded Nanyang
expansive soil samples were prepared，which were dried for 96，79，63，48，39 and 30 h in the same environment，respectively.
Surface crack images at different times were obtained with digital camera，and surface fracture rate was obtained through
images analysis. To measure crack development in the deep direction，the kerosene is used for infiltration experiments，and get
the curves of oil seepage coefficient and desorption time，average moisture content，surface crack rate were secured through
experiments；the law of fissured expansive soil permeability coefficient variation was got by the indoor simulated rainfall
experiments. Through analysis of the experimental data，we find out that there exist good relationship among sample desorption
time，surface cracks rate，average moisture content，oil seepage coefficient，the starting time of rainfall runoff and infiltration
rate. In the initial infiltration，infiltration rate decay with time soon，reduces two orders of magnitude within 15 min；the initial
infiltration rate of longer dewetting samples was higher and was with faster decay；infiltration rate stabilizes in a short time；
the stabilized infiltration rate increases linearly with the surface crack rate to a peak and then decreases rapidly.