Table of Content

01 August 2012, Volume 34 Issue 4

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地质勘探

Outcrop Sequence Stratigraphy of the Ordovician in Xishui，Guizhou

Liu Zhicheng;Zhang Tingshan;Wanyan Qiqi;Yang Yang;Yang Wei

2012, 34(4):  1-12. 

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According to the outcrop and the analyses of the carbon and oxygen isotopes，this paper discusses the identified
stratigraphic sequence surfaces and the response of carbon and oxygen isotopes for the Ordovician formation of Xishui Region
in Guizhou Prvince，and carbon and oxygen isotopes. The result shows the Ordovician system can be divided six three-order
sequences，which include two I-type and two II-type and two III-type sequence surfaces. In the third-order stratigraphic sequence，
13C in system of the advance of sea and the high water level displays trends of increase and decrease respectively. The
responses of carbon and oxygen isotope can effectively reflect the stacking patterns of parasequences form forth order sequence.
Meter-scale cycle has developed two modes in this area during Ordovician period：one is L–M meter-scale cycle type，and the
other is Subtidal meter-scale cycle type.

Sequence Lithofacies Paleography of Leikoupo Formation，Sichuan Basin

Li Ling;Tan Xiucheng;Zhou Suyan;Zou Chun

2012, 34(4):  13-22. 

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The inconsistence in different mining areas of the stratigraphic division schemes of Leikoupo Formation，Sichuan
Basin，and the fact that on the karst zone strata sloughed off effected by Early Indosinian movement，brings about a problem
of stratigraphic classification and lithofacies paleographic reconstitution. Guided by sequence stratigraphy theories and
methods，this paper collates and stipulates the stratigraphic division schemes of Leikoupo Formation on the basin interior and
reconstructs stratic lithofacies paleography by using quarternary bedding as constructive units. High precision lithofacies paleographic
study demonstrates that Sichuan Basin of Leikoupo stage was in restricted-evaporated sea environment and that
platform edge developed near Songpan-Ganzi oceanic trough in northwest Sichuan，where the grain bank of platform internal
and fringe constitutes the main prospecting parts of Leikoupo Formation. The evolution of lithofacies paleography indicates
that the bed form of basin transformed from dipping eastward to westward by the way of“seesaw”in the period of Leikoupo
Formation deposition. Even in the early stage of sequence Ideposition，it still remained what the topographic configuration took
on as in early Triassic，which was high westward and low eastward，while the eastward dipping trend disappeared gradually in
sequenceIII depositional period. Yet，after that period there presented a miniature of uplift-hollow framework in the sequence
IV—V depositional period on the basin interior. From sequence VI on，the bed form uplift-hollow framework differentiated
intensively accompany with the intensity of the tectonic compression movement，forming macro-thick gypsolyte basin，whose
depocencer had an apparent westward dipping trend in the depositional period of sequence VI—X.

East Uplift of C–P Shale Gas Accumulation Geological Condition Analysis

Yu Peng

2012, 34(4):  23-28. 

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The analysis of the East uplift well’s logging and core data，and the results of the organic geochemistry and the
experiment analysis about the intended interval samples reveal that the East uplift of Upper Paleozoic Carboniferous-Permian
mudstone has larger thickness，spreads widely and stably，with main type III kerogen，abundance index（TOC>2.0%），and high
thermal evolution（Ro=1.5%2.6%），which means there has mother rock conditions of shale gas reservoir. Dark mudstone with
high organic carbon content for adsorption states of shale gas provides abundant carrier，and microfracture development provides
excellent reservoir space for the free state of shale gas. At the same time，high quartz mineral content（average SiO2>40%），
makes the lithology brittle and easy to form crack，which comply with in accordance with engineering fracture condition. Some
drilled wells in the Carboniferous-Permian mudstone section have the prevalence of gas logging total hydrocarbon anomaly，
which indicate that the East uplift of Upper Paleozoic carboniferous-Permian has larger shale gas exploration potential.

The Evolution of Turpan–Hami Jurassic Prototype Basin and its Controlon the Distribution of Source Rocks

Liu Yuhu;Zhao Dandan;Liu Xingwang;Wang Yadong;Zheng Jianjing

2012, 34(4):  29-39. 

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The prototype of Turpan–Hami Basin mainly evolved from the Early Middle Jurassic rift basin into Late Jurassic
foreland basin during Jurassic period. The prototype of basin evolution of this period controlled the tectonic sedimentary
patterns，changed the ancient geography，ancient climate conditions adjusted accordingly，and in this particular context of the
ancient landscapes of the period deposited a series of important hydrocarbon source rock. Early in the Jurassic period，under the
warm and humid climates，the Turpan–Hami Basin deposited rivers and lakes，swamp layer system，in which the vast deposits
of dark lacustrine mudstone，carbonaceous mudstone and coal became the most important source rocks. Late Jurassic，the basin
changed into the foothills and fluvial deposition under the arid climate conditions，with little hydrocarbon source rocks. The
Lower and Middle Jurassic Badaowan and Xishanyao Coal Measures are the main source rocks of this period，Middle Jurassic
Qiketai lacustrine deposition to semi-deep lake deposition，is a secondary hydrocarbon basin source rock.

Adsorption Capacity of Shale Gas and Controlling Factors from the WellYuye 1 at the Southeast of Chongqing

Wu Jingshu;Yu Bingsong;Li Yuxi

2012, 34(4):  40-48. 

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Gas shales is important unconventional gas reservoirs in which much of the gas is stored in the adsorbed state. In order
to study adsorption capacity of natural gas and controlling factors of Longmaxi Formation in Lower Silurian from Well Yuye 1 at
the southeast of Chongqing，a series of measurements including pore structure and volume，mineral composition，total organic
carbon（TOC），vitrinite reflectivity（Ro）and adsorption isotherms are made. The results show that saturated adsorption VL are
1.253.90 m3/t with an average of 2.17 m3/t；Langmuir pressure constant pL are 1.909.48 MPa with an average of 3.69 MPa.
Saturation adsorption capacity has a negative correlation with micropores volume，and a positive correlation with mesopores
volume and macropores volume. The clay mineral influence adsorption capacity of the shale through controlling micropore and
mesopore volume，while quartz through controlling macropore volumes. Organic carbon content on the adsorption capacity
of shale may be mainly due to its control over development of the macropores. In addition，the strong adsorption for gaseous
hydrocarbons due to characteristics of the surface hydrophobicity and dissolution of gaseous hydrocarbons in the amorphous
structure of asphalt have a certain impact. When Ro> 2.0%，there is a positive correlation between saturation adsorption capacity
and Ro，which may be related with the development of microfractures in the organic matter with high maturity resulting in the
increase of macropore volume.

Research on the Quantitative Description Method of SandyConglomerate Core

Yan Jianping;Zheng Shengli

2012, 34(4):  49-54. 

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The drilling core is precious geological material for the study of hydrocarbon zone and hydrocarbon reservoir. Core
image is the surface image of drilling core by using high resolution core image acquisition instruments. When image resolution
is high enough，the sediment characteristics in core image can be clearly recognized. The paper introduces the application of
core image in sandy conglomerate core diameter，area and psephicity calculation，and so on. It is expected to provide some
help for exploration of subtle reservoirs gradually deepen.

Evaluation of Uncertainties for Pore-pressure Taking Eaton Method asan Example

Zang Yanbin;Wang Ruihe;Wang Zizhen;Zhang Rui;He Yingming;

2012, 34(4):  55-61. 

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In view of the difficulties the uncertainty of pore-pressure brought to the drilling engineering design and construction，
the concept of pore pressure uncertainty is present，and the calculation model for pore pressure uncertainty is derivated for Eaton
method. An example is analyzed using synthesis data from PG block in northeast Sichuan region. The method presented here
gives the range and main influencing factors of pore pressure uncertainty，and the influence law of related factors to uncertainty.
The calculated results are in correspondence with actual mud density and the results of gas production test，which proves that
the evaluation method of pore pressure uncertainty is feasible，the results has high accuracy and validity.

Study on the Fracture Characteristics of Complex Tight Formation

Liu Hongqi;Liu Shiqiong;Liu Jing

2012, 34(4):  62-68. 

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Ordovician reservoir is the most important exploration and production block of Tahe Oilfield of Tarim Basin，which
has undergone multiple-period tectonic movements and paleo-karstification effects and become karst-vuggy carbonate reservoir.
The main lithologies of Yijianfang and Yingshan Formation group are calcite and dolomite. The reservoir is typical super-low
porosity and low-permeability. Investigations of outcrops，cores and scanning electron microscope（SEM）images show that in
this kind of reservoir，matrix is almost non-porous and non-permeable. The main reserving spaces，however，are fractures and
vugs，which resulted from tectonic deformation movement and，pores，caves，which occurred through karstification effects.
Among these，caves are most important spaces for hydrocarbon. Fracture is another key element for this reservoir，which has
double effects，one is that the fracture provides reserving space by itself，and the other，it is tunnel for hydrocarbon migration.
Because of the pore morphology，different size and uneven distribution of reserving spaces，this kind of reservoir has very
distinguished heterogeneous properties. We studied the characteristics of the fractures，and analysis the reason of fractures
occurring，the distribution law of fractures. By using geological simulation software，we adopted sequence Gaussian randomizing
methods，to model the fracture parameters，such as porosity，permeability and open width. The three-dimensional images
of fracture parameters model shows seriously heterogeneous of this reservoir. The simulation result shows that the fractures
modify the permeability of the Ordovician reservoir evidently.

High-density Wide Line Seismic Acquisition Technique and its Effect inComplex Mountainous Areas

Liang Xianghao;Zhou Xu;Cai Ming;Liang Xianghao;Liu Yimou

2012, 34(4):  69-74. 

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Though considerable progress on the seismic acquisition technology of mountainous areas in Tarim Basin has been
made through years of research，there are still many exploration problems need to be solved. In this paper，a method of seismic
acquisition is presented for solving the problems of low S/N ratio and poor high-dip complex structure imaging in mountainous
areas. Pertinent technical measures are adopted to enhance ability of attenuating noise，and to improve accuracy of static
correction and imaging of high-dip structure. Through application of these technical measures，imaging quality of seismic
section has been improved significantly.

Random Noise Attenuation of Seismic Signal Based on Improved EMD

Yang Kai;Liu Wei

2012, 34(4):  75-82. 

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Random noise attenuation is an important step in seismic data processing；however，most random noise attenuation
methods have some problems such as poor de-noising effect and damaging effective signals to a certain degree. Empirical
Mode Decomposition（EMD）can self-adaptively decompose the signal into multi-scale Intrinsic Mode Function（IFM）and
wavelet transform modulus maxima de-noising method is available for low S/N signals. We construct a new random noise
attenuation algorithm by combining EMD with wavelet transform modulus maxima de-noising method，which can effectively
separate signals form random noise and well improve signal to noise ratio（S/N）of seismic data. The algorithm is applied on
numerical simulation and field data for random noise attenuation. The results reveals that the de-noising effect of new algorithm
is obviously better than that of conventional EMD.

Quantitative Evaluation of Low Permeability Reservoir Diagenetic Faciesby Combining Logging and Geology

Ding Sheng;Zhong Siying;Gao Guoqiang;Liu Jian;Sun Xiaoqing

2012, 34(4):  83-87. 

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The productivity of the same sedimentary microfacies have significant difference in the south section of Gaoyou
fault low permeability reservoir. Therefore，the study of diageneticfacies is important to low permeability reservoir，in current
development phases. Based on data of cast-slice，cathodeluminescence and SEM analyses data，the present paper comprehensively
investigats types and characteristics of reservoir diagenesis of the formation in the south section of Gaoyou fault，
distinguishs types of diageneticfacies combining practical production. The reservoir of the first segment formation could be
divided into five types of diagenticfacies including slight compacted facies，middle compacted-cemented facies，middle compacted-
corroded facies，intensively compacted-cemented facies，intensively compacted-corroded facies. We discuss logging
curve features of different diagenetic facies，establish the quantitative recognition criteria and using the recognition criteria，
we recogniz the diageneticfacies of the first segment Funing formation diageneticfacies. Combining the productivity，we also
determine beneficial diageneticfacies.

石油与天然气工程

Influence of the Coefficient of Thermal Expansion on the Stress of BottomHole Rock in Gas Drilling

Zhang Hongyun;Gao Deli;Guo Boyun

2012, 34(4):  88-93. 

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In gas drilling the high-pressure gas results in the Joule Thomson cooling effect through the nozzle which causes
significant temperature gradient at bottom hole which should result in non-uniform reduction of compressive stress in the rock
due to thermal contraction of rock. In this paper，low-temperature impact on the stress distribution of the rock in the bottom
in gas drilling the thermal expansion coefficient is random variables and constants is studies in the conditions that. The results
show that：low-temperature drilling fluid can significantly reduce the radial stress and increase the tangential stress in the near
bottom hole region. This stress condition makes the rock easy to fail by the crushing action of drill bit teeth，resulting is in the
remarkable increase in rate of penetration. When the thermal expansion coefficient is random variables and constants，the stress
distribution in the same trend，only different in values. The tangential stress is greater when thermal expansion coefficient is
random variable than when it is a constant.

Pressure Response Characteristics in Large Scale Cavity Type Reservoir

Liu Hong;Wang Xinhai

2012, 34(4):  94-99. 

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Because the multiple continuous media model couldn’t describe the flow process between large scale cave and
stratum effectively，new well-test interpretation model of fracture-cavity type reservoir need to be established to study the fluid
flow rules of heterogeneous fracture-cavity type reservoir. The cave is simplified as an equal-potential body with equal internal
pressure anywhere，and the fluid flow outside of cave conforms to Darcy law. The fracture-cavity type reservoir mathematical
model is established based on the cave system mass conservation. The cave system pressure and wellbore pressure are calculated
by direct boundary element method. The cave pressure derivative curve and wellbore pressure and pressure derivative curve in
double-log axes are plot afterwards. The research shows that：the large scale cave bears an earlier-upward and later downward
characteristics in wellbore pressure derivative curve in double-log axes is. The larger cave radius induces larger upward and
downward scale；and the earlier cave distance from well induces the upward time. The smaller cave distance from well with
same radius induces larger peak value of cave pressure derivative；and the bigger cave radius with same distance from well
induces smaller peak value of cave pressure derivative.

The New Calculation Method of Condensate Gas Well Production andReservoirs

Liao Faming;Miao Jijun;Chen Wenlong;Deng Jun;Wang Nutao

2012, 34(4):  100-104. 

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Complex phase change and re-distribution exist in gas condensate reservoir. It will produce gas condensate in
formation and the wellbore，respectively，when the pressure drop to below dew point pressure，resulting in the conversion
of mass between wellhead and bottom hole in gas production and oil production，but still follows the law of conservation of
total mass. Therefore，according to mass conservation principle，we established the oil and gas two-phase flow equations. By
introducing the two-phase pseudo-pressure function，unstable deliverability equation was derived. On this basis，we fit the
entire history of production by taking material balance equation and production data into consideration. With this method we
not only get the current gas production，but a variety of formation pressure and formation parameters. An example is then
analyzed to verify the accuracy and reliability，the method is conducive to the promotion the use of gas condensate.

Analysis and Prediction of the Deliverability Decline for Gas Well

Yang Bin;Fang Yang;Wang Guozheng

2012, 34(4):  105-109. 

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Based on the characteristics of the changes of the seepage flow parameter and fluid parameters，the change laws
of the gas well deliverability for different types of gas reservoir are proposed by using on-site testing data and experimental
analysis data of a gas well and the decline law is theoretically predicted，then the quantitative analysis and comparison with
the conventional methods are done by using the field data. In this paper，the analysis of the coefficients of the deliverability
equation changes are emphasized，and also the deliverability performance after the precipitous pressure decline is studied by
using the well test data. It is shown that the deliverability of the dry gas well is mainly controlled by the fluid parameters；
the rate of deliverability decline of the gas condensate well is affected by the composition change and the condensate dropout
when the reservoir pressure is below the dew point；the drawdown of the permeability and porosity during the development
will accelerate the deliverability decline in stress-sensitive gas field. By correcting the previous well testing data to predict the
decline performance for the above gas reservoir，it can satisfy the demand of productivity prediction and thus presents a basis
for the study of deliverability decline in gas reservoirs.

Shear Properties of Non-Newtonian High-pour-point-oil

Wang Zhili;Yao Chuanjin;Jiang Shuai;Zhang Xiao;Li Wenzhong

2012, 34(4):  110-114. 

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The wax content and freezing point of the high-pour-point-oil in Weibei Oilfield are high. When the temperature
is below the wax precipitation point，the high-pour-point-oil behaves as a non-newtonian fluid which is greatly affected by
shear. Thus，the shear viscosity and pour point reduction experiments of non-newtonian high-pour-point-oil were conducted.
The results show that under the shear function，the viscosity of non-newtonian high-pour-point-oil is reduced greatly；the nonnewtonian
high-pour-point-oil presents shear thinning and the lower the temperature is，the more obvious the shear thinning
is；the shearing rate has greater effect on the freezing point and freezing time of non-newtonian high-pour-point-oil；under the
shear function near freezing point，the freezing point can be reduced by 56 ℃ and the freezing time is obviously prolonged；
the shearing time has little impact on the freezing point and has greater influence in freezing time and when it shears about
20 min（the rotational speed is 100 r/min），the freezing time can be prolonged by 817 min.

Laboratory Study on Dynamic Gelation Behavior and Transfer Process ofCrosslinked Polymer

Li Kexing;Qian Zhihong;Du Jinyang;Deng Xiumo;Tang Yuanchun

2012, 34(4):  115-122. 

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We simulate the injection of the gelatin and transfer process of crosslinked polymer in porous medium with long
core equipment. The experiment shows the injected crosslinked polymer can reach the design position. Influenced by dilution，
shearing and adsorption，the concentration and initial viscosity of the crosslinked polymer solution decrease lengthwisely. The
dynamic gel time prolonges to 6 times than the static gel time at the experiment condition（HPAM concentration is 0.2%）.
Compared with the sample viscosities after gelatin and the pressure change before and after plugging at different positions on
the long core，the efficient plugging distance –r is less than the design plugging distance –r′，0.67r′ < r < r′. It also shows that
the sequent water flooding after plugging can drive a few gelatin move into deep reservoir along the high permeability pool，
form the effect of flooding.

Study on the Rheological Properties of Ultra-high TemperatureDrilling Fluids

Bu Hai;Sun Jinsheng;Wang Chengbiao;Yang Zexing;Yang Yuping

2012, 34(4):  122-126. 

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The rheological properties of ultra-high temperature drilling fluids developed in our laboratory are measured using
Fann50SL HT-HP rheometer and the experimental data with the temperature from 90 ℃ to 240 ℃ were analyzed using
the regression method. The experimental results show that the apparent viscosity and plastic viscosity of ultra-high temperature
drilling fluids decrease with temperature increasing under high pressure conditions，but slightly increase in viscosity after
210 ℃. The results of regression analysis show that the Casson rheological model can describe the rheological properties of
ultra-high temperature drilling fluids under high temperature and high pressure conditions，and the mathematical model is established
to predict the apparent viscosity of ultra-high temperature drilling fluids under high temperature and high pressure
conditions. The verification by experimental data indicates that the calculation results of mathematical model keep high consistence
with the measured data，which provides scientific basis for field applications of ultra-high temperature drilling fluids.

Quantitative Evaluation of Single Well’s Water Breakthrough Types in theTahe Fractured-vuggy Reservoir

Long xu;Li Peng;Kang Zhihong;Niu Yujing;Cui Wenbin

2012, 34(4):  127-134. 

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The reservoir types in Tahe oilfield consist of cave，fracture，crack-cave，cave-fracture and fracture-vuggy，which
makes the problems complicated in the actual production，such as violent water flooding，stop ping blowout，production decline
and invalid coning water. We can evaluate the effect of different reservoir types or engineering measures on production
through the analysis of water flooding curve changes. The following two methods of water breakthrough speed were commonly
evaluated：1）evaluating water breakthrough speed quantitively according to the shape of production curve，and dividing oil
wells into types of slow rising，sudden rising and ，water and intermittent rising etc. 2）evaluating water breakthrough speed of
single well or wells simplely using the watercuts in two points of time. Based on the disadvantage of the conventional methods，
this paper makes a careful analysis in oil production curve，and forms a new dual water curves to analyze the well’s dynamic
production. By using a new evaluation parameter-water/oil ration(the slope of the fitting line，k)，we evaluate the speed of
water breakthrough quantitively. At last，the authors classified the water breakthrough types of the wells in No.4 block，in Tahe
Oilfield.

The Long Core Experiment and Numerical Simulation Research onAsphaltic Oil with CO2 Flooding

Huang Lei;Jia Ying;Quan Yiping;Sun Lei

2012, 34(4):  135-140. 

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Gas injection especially carbon dioxide injection may cause asphaltene deposit. In this paper，in order to analyze the
deposition trend and the influence of deposition on oil recovery，the multiphase multicomponent numerical model considering
asphaltene deposition，adsorption and plugging is established. Then，based on long core flooding experiment，the fitting data
indicate that the oil recovery calculated by this numerical model is closer to experiment results than that by regular model.
Finally，the asphaltene deposition tendency during CO2 flooding is discussed，which indicate that higher accumulation of
deposited asphaltene is shown primarily at the injection part of the core. Meanwhile，adsorbed asphaltene，also accumulated
at the inlet side of the core，is desorbed gradually with the gas injection. asphaltene deposition front accord with injected gas
front，which indicates that injected carbon dioxide is the main reason for asphaltene deposition.

Research and Application on the Chemical Huffing and Puffing Technologyof Heavy Oil Fault Block Reservoir

Tang Gang;Bo Chunhui;Liu Chengjie;Tang Cunzhi;Qin Yancai

2012, 34(4):  141-146. 

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The heavy oil reservoir in Shengli Oilfield is typically double-low unit. The present recovery is very low，and
exploitation is difficult because of poor reservoir development and fluid properties. Due to the serious problems of high-pressure
steam injection and poor steam injection effect and low-cycle oi1 production in the reservoir，this paper studies improvement
of heavy oi1 properties through injection CO2，FSP oil-soluble viscosity reducer. According to the geological characteristics of
reservoirs，the different chemical huffing and puffing technology are applied in wells of different development characteristics.
It achieved obvious effects of oil incremental.

油气化学工程与化工

Synthesis and Characterization of Temperature-tolerant and Salt-resistantPolymer Hydrogel

Cui Sihua;Zhang Suian;Guan Baoshan

2012, 34(4):  147-152. 

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A polymer hydrogel is studied which is available for high temperature and high salinity condition，the
SSS/AMPS/bentonite polymer hydrogel is prepared in the lab. The properties of the hydrogel are evaluated using the change
of water absorbency in salt solutions of different concentration，different temperatures and different time and the carrier fluid
is optimized. By single core flow experiment，the shutoff capacity and erode resistant of the block agent are studied. The
results show：the water absorbency and strength keep constant under 80130 ℃ for 60 days；the water absorbency can reach
12.00 g
g&#1048576;1 in the salt solution of 30%；the polymer hydrogel has well property of temperature-tolerant and salt-resistant. The
hydrogel is not swollen in the oil containing 40% water inside within 3 hours. The shutoff efficiency of high permeable formation
and medium permeable formation are 99.96% and 96.41% respectively；the efficiency can still reach 95.12% and 94.43%
after 30PV eroding.

Application of the Optics Principle to Study the Deposition Process ofCrude Oil Asphalt

Su Junlin;Ma Zhongliang;Ren Mao;Chu Qi

2012, 34(4):  153-157. 

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Effect of precipitator on the stability of blend（crude oil / toluene）has been investigated with Turbiscan Lab
dispersion-stability analyzer. Experiments are performed by mixing varying content of precipitators into the blend（10%by vol.
crude oil and 90%by vol. toluene）. Based on the intensity variation of the transmitted and backscattered light with time，the dynamical
precipitation and aggression process with time can be clearly described and the instability mechanisms of blend（crude
oil / toluene）can be easily studied. In addition，Turbiscan Lab dispersion-stability analyzer can be effectively to quantitatively
analyze the piratical size and aggression and precipitation rate. The results show that both aggression rate and precipitation rate
experienced substantial increased from 192.216 μm/min to 5 332.12 μm/min and from 0.17 μm/min to 0.46 μm/min，Particle
size increases from 10 μm to 53.4 μm，respectively，with percentages of precipitator content going up from 80%to 90.9%.

石油机械工程及其他

Experimental Research on Mechanical Properties and Erosion of the DrillString in Gas Drilling

Li Dongyang;Wang Leichao;Zhang Tao;Wang Qianqian

2012, 34(4):  158-164. 

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The drill sting for the gas drilling is impacted in the process of crushing rock，so the alternating stress occurre.
Alternating stress changes is aggravated by the rotating drill string，and the drill string is also erosion by debris，so the failure
is accelerated. The main failure form of drill string is fatigue fracture，which is inseparable from the drill string，so the research
on mechanical properties and erosion of the drill string in gas drilling，mastering the drill string stress change rules and erosion
law of drill string are the basic work to reducing and preventing the drill string failure. This work has very important meaning
for increasing the safety and reducing the cost in gas drilling. The drill string of gas drilling in the situation of vibration and
erosion in the case of different combination drilling tools by using an experiment device which can simulate the situation is
studied in this paper. The experiment shows that using centralizer will reduce the alternating stress value range up to 40%，and
using centralizer and shock absorber at the same time will reduce the alternating stress value range up to 50%. The centralizer
and the shock absorber used together will reduce the alternating stress greatly and extend the alternating stress function cycle，
thus the probability of failure of the drill string will be reduced.

Maximum Suspended Length of Production Pipeline

Ma Tingxia;Wu Jinqiang;Tang Yu;Hu Hao;Li Anjun

2012, 34(4):  165-173. 

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The external load（such as geology landslide，collapse，loose soil deposition，collapsible loess，earthquakes，water
damage，etc.）caused by complex geological features and poor natural conditions along long-distance the pipeline will result
in a large span of vacancy of the pipeline. Slightly inciting the large deformation of the pipeline，a large area of vacancy，the
local deformation or stress concentration，resulting in greater displacement and stress，buckling or creep，or even badly cause
pipeline rupture，producing pipeline safety hazards. We establish suspended pipeline model in this paper，calculate maximum
suspended length of X52 refined oil pipeline by using the theory of elastic foundation，large deflection beam theory，pipeline
soil interaction，Winkler presumption model and considering the geometric nonlinearity and soil physical nonlinearity on the
basis of Lan–Cheng–Yu，Deyang，Shijiangting oil pipeline large area suspended for flood water.

博导论评

Numerical Simulation on Non-planar Propagation of Hydraulic Fracture inNaturally Fractured Formations

Zhao Jinzhou;Ren Lan;Hu Yongquan;Pei Yu

2012, 34(4):  174-180. 

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Complex propagation system of multi-branched，non-planar fractures in naturally fractured formations commonly
occurs due to the effect of natural fractures，which greatly differs from bi-wing，symmetric and planar fracture generated in the
homogeneous formations. Therefore，the conventional hydraulic fracture extending model is no longer adaptable，and there’s an
urgent need to develop a new model to simulate the propagation pattern and geometry of induced fracture in naturally fractured
formations when hydraulic fracture extends along natural fractures. Based on the equivalent planar fracture of propagation
pathway of hydraulic fracture re-orientating along natural fractures，this paper established the mathematical model of hydraulic
fracture non-planar re-orientation propagation and provided corresponding numerical solution. The calculation results show
that the induced fracture width at re-orientation propagation section reduces apparently and the treating pressure increases when
hydraulic fracture extends along natural fractures. Analysis of influence factors shows that the larger differential horizontal stress
and approaching angles are，the more the fracture width at re-orientation propagation section reduces；the higher volumetric
rate and fracturing fluid viscosity are，the larger the whole extension fracture width including re-orientation propagation section
is. It is clear that differential horizontal stress and approaching angles are negative factors but volumetric rate and fracturing
fluid viscosity are positive factors for that proppant transports along hydraulic induced fracture. For this purpose，raising
volumetric rate and fracturing fluid viscosity can reduce fracturing risk in naturally fractured formations. This research in this
paper realizes non-planar extending features of hydraulic fracture and offers a theoretical basis for fracturing design in naturally
fractured formations. Therefore，it has importantly theoretical value and practical significance.