Table of Content

01 February 2016, Volume 38 Issue 1

Previous Issue    Next Issue

Characteristics and Calculation Method for Gas Content of Upper#br# Paleozoic Shales in the Eastern Margin of Ordos Basin

GUO Shaobin1, ZHAO Keying2*

2016, 38(1):  1-9.  DOI: 10.11885/j.issn.1674-5086.2014.02.15.01

Asbtract ( 286 )   HTML   PDF (812KB) ( 963 )  

References | Related Articles | Metrics

Shale sequences are well developed in the Carboniferous–Permian transition facies，Ordos Basin. Researchers have
done many studies on shales in upper Paleozoic of the Ordos Basin. With few drilling data，however，not enough researches
have been carried out on the eastern margin of the basin. In order to clarify the characteristic and gas bearing of shales in the
eastern margin of the basin，according to the characteristic of sedimentary，geochemistry，lithology，physical property and the
experiments of isothermal adsorption and nuclear magnetic resonance of samples from Taitou，the shales were analyzed. It
is found that Taiyuan formation has the best condition for shale gas formation which is 25 meters thick，abundant in organic
matter，and is in the stage of producing gaseous hydrocarbon，the shale is of high content of non swellable clay minerals and
equally distributed crack/micro fractures. We also offer the calculation formula of gas adsorption using parameters of depth
and content of organic carbon and improve the calculation accuracy of free volume through calculating effective porosity. It
has been verified that the calculation of air content conforms to the actual situation，and the method is simple and practical by
relevant data from Well Y88 in Ordos Basin.

Effects of Diagenesis and Reservoir of the Urho Formation in#br# Manan Region

CHEN Bo1，2*, YOU Xincai3, ZHANG Yin4, ZHANG Shuncun1, SHI Jian1

2016, 38(1):  10-20.  DOI: 10.11885/j.issn.1674-5086.2014.05.29.03

Asbtract ( 293 )   HTML   PDF (1447KB) ( 794 )  

References | Related Articles | Metrics

Using core observation，casting thin sections identification，scanning electron microscopy（SEM），X-ray diffraction
analysis method with logging and mud logging data，the characteristics of reservoir sandstone，diagenesis and its influence on
reservoir physical property of the Permian Urho Formation in Manan region，Junggar Basin were studied. The results show that
the reservoir rock types in the study area are mainly conglomerate，and a small amount of sandstone；reservoir compositional
maturity and textural maturity are low. At present，the reservoir in the study area is mainly at the middle diagenetic stage B
period，and reservoir experienced complicated diagenesis；the main diagenesis that has a greater influence on the reservoir
property includes compaction，cementation and dissolution；the compaction effect of the reservoirs in the study area is the most
devastating，being root of low porosity and low permeability reservoirs；cementation has two-sided influence on reservoir on
the one hand. On the other hand，cement reduces the reservoir porosity，but also resists the compaction stress to a certain
extent，and provides the material foundation for the later dissolution. The reservoir in the study area is deeply buried，and has
experienced strong compaction and cementation. Therefore，reservoir property is poor，but is improved by the dissolution of
secondary pore，which is an important approach to relatively high quality reservoirs in the study area under the background of
low porosity and low permeability.

Controlling Effect of Tectonic Evolution on Deposition and Hydrocarbon#br# Accumulation in Weibei Sag

SUN Yaoting1，2*, LI Yulan1, XU Haoqing2, GUO Lili2

2016, 38(1):  21-29.  DOI: 10.11885/j.issn.1674-5086.2013.07.02.01

Asbtract ( 215 )   HTML   PDF (1346KB) ( 841 )  

References | Related Articles | Metrics

The complexity of tectonic evolution in Weibei Sag results in unclear understanding of its deposition and hydrocarbon
accumulation law. Based on comprehensive analysis of well drilling，logging and seismic data，we analyzed the boundary
fracture characteristics and sedimentary evolution in Weibei Sag. Studies show that due to the Tan-Lu fault zone continuing
activities，Weibei Sag experienced four evolutionary stages：Sinistral strike-slip，Sinistral-Dextral conversion，Dextral strikeslip
and regional depression. The sinistral strike-slipping（Ek3）formed igneous basement，established the tectonic pattern of
Weibei Sag by sinking in the north and overlapping in the south. The basin hydrocarbon source rocks and fan-delta came from
E W fan delta in sinistral-dextral conversion period（Ek2）. The main reservoir-cap combination formed in dextral strike-slip
period（Ek1 Ed）. The convex′s ancient landforms characteristic formed from it controlled the hollows filling and the growth
characteristic of fan-bodies；deposition center from bottom to top evidently migrated eastward compared to subsidence center.
The Zaohu broken nose band is the main oil and gas migration and accumulation area. Tectonic uplift movement in Es4 last
stage led to rich oil and gas distributed in east and poor distribution in west. Accumulation mode is different between east and
west. Reservoir model of eastern region is single hydrocarbon accumulation period，bilateral transporting and lateral migration.
Reservoir model of western region is two hydrocarbon accumulation periods and near source gathering.

Control of Sedimentary Diagenesis on Reservoir Production Capacity#br# Evaluation in South Fault Terrace of Gaoyou Sag

ZHONG Siying1*, DING Sheng2

2016, 38(1):  30-36.  DOI: 10.11885/j.issn.1674-5086.2013.11.05.01

Asbtract ( 287 )   HTML   PDF (659KB) ( 786 )  

References | Related Articles | Metrics

Factors affecting low permeability reservoir productivity are numerous and complex，so the correct analysis and
evaluation of these factors，for low permeability reservoir development have important significance. This article excludes
engineering factors，from geological considerations，focuses on the analysis and evaluation of sedimentary and diagenetic
effects on productivity，and analysis of its mechanism taking advantage of special data such as constant-pressure mercury and
NMR. Research indicates that：the storage layer production capacity are mainly controlled by later diagenesis in Sag Gaoyou
South broken bands，and controlled by sedimentation in local small scale and the same diagenetic environments，to study its
mechanism，reservoir is mainly affected by diagenesis such as compaction，cementation，corrosion in South fault terrace of
Gaoyou Sag，to form a variety of micro-pore structure，led to significant differences of reservoir production capacity in South
fault terrace of Gaoyou Sag，so diagenetic facies studies for evaluation of low permeability reservoir productivity forecast is
significant.

Shale Gas Accumulation Conditions of Lower Jurassic in Junggar Basin

GAO Jin*, CAO Zhe

2016, 38(1):  37-45.  DOI: 10.11885/j.issn.1674-5086.2014.03.15.01

Asbtract ( 280 )   HTML   PDF (1192KB) ( 854 )  

References | Related Articles | Metrics

Junggar basin is a large petroliferous basin in western China，in which there has deposited several hydrocarbon source
rocks. Jurassic，one of the most significant gas sources，is considered to contain a huge potential of shale gas resources. Based
on drilling data，logging data，outcrop data，core data and laboratory test results of rock samples，we analyzed the shale gas
accumulation conditions through the distribution of dark shale and burial depth，organic geochemical characteristics，reservoir
conditions and gas-bearing features of lower Jurassic and predicted favorable formation and zone for shale gas exploration. Shale
interval of lower Jurassic is widely distributed. In the northwestern margin and southern margin，the dark shale is thickest. The
burial depth of lower Jurassic shale tends to deepen from north to south with a range between 1 000 m to greater than 4 500 m.
The organic carbon content is relatively high，and the main type of organic matter is III and II2，which is gas-prone. The thermal
maturity of Lower Jurassic shale is from immature to high mature. The shale reservoir is characterized by low porosity，high
clay minerals content and micro fracture for storage. The measured absorbed gas content is averaging 1.42 m3/t，the gas logging
show of dark shale is active. In addition，the in situ gas desorption test identified the existence of nature gas in lower Jurassic
shale. As a result，Lower Jurassic Badaowan shale is the favorable Formation，Shawan Dabasong region is the favorable zone
for shale gas accumulation.

Logging Evaluation of Key Issues of Xinjiang H Underground Gas#br# Storage Conversion

WANG Bin1*, QIU Enbo2, PANG Jing1, XI Yanqing3, CUI Guoqiang1

2016, 38(1):  46-52.  DOI: 10.11885/j.issn.1674-5086.2014.06.09.04

Asbtract ( 209 )   HTML   PDF (714KB) ( 814 )  

References | Related Articles | Metrics

There are many technical problems in the underground gas storage reconstruction，among which sealing property
of cap rock，reservoir characteristic and the selection of reinjection formation are key issues. Based on logging information，a
specific logging analysis is carried out on some crucial issues，such as cap rock sealing ability，reservoir quality and distribution
and sewage rejection formation selection in the process of reconstructing Junggar Basin H underground gas storage. We find
out that the Hunderground gas storage has thick cap rock，poor physical property，wide distribution and sound sealing ability.
The E1-2z2 reservoir has features such as wide distribution，great stablility，large thickness，good physical property and good
connectivity，which can meet the requirement of constructing underground gas storage for the reservoir permeability space.
Through water layer well logging and evaluation of Dushanzi Formation，we believe Anjihai Formation and Shawan Formation，
Shawan Formation are the most reasonable sewage reinjection layers.

Research on Neural Network Prediction Model of Reservoir Particle Size

WANG Lihua1*, LOU Yishan1, MA Xiaoyong2, CHENG Fushan1, CHEN Yu3

2016, 38(1):  53-59.  DOI: 10.11885/j.issn.1674-5086.2014.01.09.02

Asbtract ( 219 )   HTML   PDF (880KB) ( 810 )  

References | Related Articles | Metrics

According to researches at home and abroad，sand control design is based on reservoir particle size characteristic
value. LDA and SA are the conventional methods used to analyze particle size distributions. Both methods requires data through
core particle size testing. But sand control design can only use test well data，because no core at actual producing position can
be used when sand control measure is established，which can result in major errors. This article elaborates the relevance about
median grain size and gamma ray logging or density logging through researches on reservoir particle size and variety of log
curve response relation. And then through establishing sample pool of gamma ray logging or density logging and characteristic
value，and by neural network technology we trained learning network satisfing engineering requirements. Then the particle
size longitudinal distribution profile can be established according to development well logging data. This profile supplied data
basis for sand control layering design. At present，this method has been successfully used in several Chinese offshore oil field
in sand control optimization with errors below 10%.

The Analysis of the Mechanical Properties of Typical Salt Rock

WANYAN Qiqi1，2，3*, SHEN Xueming4, KOU Yanxia2，3, RAN Lina2，3

2016, 38(1):  60-67.  DOI: 10.11885/j.issn.1674-5086.2015.03.13.02

Asbtract ( 307 )   HTML   PDF (533KB) ( 716 )  

References | Related Articles | Metrics

It is studied the short term mechanical properties of samples of bedded salt in Yunying Hubei，Huaian Jiangsu and
Pingdingshan Henan by doing experiments of monopodium and triaxial compression and splitting. It also compares stratums
in different district and different depth of the pure salt rock mechanical properties. The results showed that（1）the rocks in
different area which have the biggest uniaxial compressive strength and modulus of elasticity and the smallest Poisson ratio
belong to mudstone and mud salt rock. It indicated that mudstone has bad deformation properties. The salt rock which has
different impurity will increase its compressive strength and modulus of elasticity，and its Poisson ratio is not sensitive to the
change of impurity. The compressive strength，modulus of elasticity and Poisson ratio of the pure salt rock increases with
increase of the depth of stratum，the rocks from the shallow layer in uniaxial tests have obvious compression phase.（2）the
sample in different regions increases as confining pressure peak intensity increase. The comparison of the internal friction
angle and cohesive value for different sample in different regions can be obtained，and the internal friction angle of the pure
salt rock are greater than those of other values，but the cohesion are smaller than other sample value，reflecting that the crystal
particles of pure salt rock are big，and contain less impurity.（3）the tensile strength of the pure salt rock in different regions
relative to the other samples is minimum.

Comprehensive Evaluation Method for the Low Permeability#br# Carbonate Reservoir

YANG Zhengming1，2*, JIANG Shuai1，2, ZHANG Yapu1，2, ZHU Guangya3, GUO Hekun1，2

2016, 38(1):  68-75.  DOI: 10.11885/j.issn.1674-5086.2014.08.10.02

Asbtract ( 226 )   HTML   PDF (558KB) ( 847 )  

References | Related Articles | Metrics

The low permeability carbonate reservoir is an important oil reservoir type developed overseas by PetroChina. Due
to the complex structures of microscopic pore-throat and apparent differences with low permeability sandstone reservoir，it
is necessary to research on the evaluation method of the low permeability carbonate reservoirs. Based on the test of 550 low
permeability carbonate cores，the mainstream throat radius，the movable fluid percentage，the threshold gradient and the crude
oil viscosity are determined to be the four paramenters to evaluate the low permeability carbonate reservoir. The research shows
that the throat radius changes largely at the low permeability carbonate cores with different permeability and the full diameter
cores′ gas permeability has a semi-logarithmic relationship with the percentage of movable fluid. Besides，under the condition
of same permeability，most throat radius of low permeability carbonate cores is smaller than that of low permeability sandstone，
while the movable fluid percentage of carbonate is larger than that of sandstone which is in agreement with the reservoir property.
Based on the results，four-factor classification of low permeability carbonate reservoir is put forward and the comprehensive
evaluation method is hence introduced，which is successfully applied to the evaluation of the layers in a typical low permeability
carbonate reservoir overseas.

The Effects of Crack Interaction in Multi-stage Horizontal Fracturing

LI Yongming1, CHEN Xiyu1, ZHAO Jinzhou1*, SHEN Feng2, QIAO Hongjun2

2016, 38(1):  76-83.  DOI: 10.11885/j.issn.1674-5086.2013.11.02.01

Asbtract ( 234 )   HTML   PDF (469KB) ( 874 )  

References | Related Articles | Metrics

Multi-stage horizontal fracturing has been widely used in the field with the inevitable crack interaction. Crack
interaction is conducive to initiation and extension of fractures，which forms complex fracture network and improves reservoir
conductivity. However，crack interaction also has adverse effects on hydraulic fracturing resulting in poor stimulation. Based
on the theory of elasticity，mathematical models are established to study the effects of crack interaction in multiple cluster
fractures，from the aspects of initiation pressure，fracture width and the position of fracture. The study shows that it is hard
to get successful stimulation with serious crack interaction because the phenomenon such as change of fracture width resulting
from crack interaction. To get the relationship of cluster space，fracture height and crack interaction，a sensitivity analysis is
conducted. The result indicates that the cluster space should be reasonable to avoid the adverse effects of crack interaction. The
study result contributes to the optimization of the stimulation of multiple stages horizontal well.

A New Analytical Model of Heat Communication Judgment During Heat#br# Circulation Phase of Dual-horizontal SAGD

WU Yongbin1，2*, LI Xiuluan1，2, ZHAO Rui3, ZHOU You1，2, GUO Erpeng1，2

2016, 38(1):  84-91.  DOI: 10.11885/j.issn.1674-5086.2014.03.09.01

Asbtract ( 194 )   HTML   PDF (425KB) ( 780 )  

References | Related Articles | Metrics

The effect of heat circulation by steam injection is of a great importance to the steam chamber growth rate，SAGD
ramp-up rate，steam chamber dimension along horizontal section，tapping efficiency and ultimate recovery factor for SAGD
production. While the temperature of the formation between horizontal sections of injector and producer in a SAGD wellpair
is the crucial parameter to judge whether heat communication between injector and producer is enough or whether it is rational
to convert from circulation to SAGD production phase. According to the problems that the previous analytical model only
considers the thermal properties of the formation rock，the new analytical model of calculating heat communication including
the effect of formation rock，oil and water is established. The field data of well configuration and thermal properties of formation
rock，oil and water from a SAGD production area in China is taken as an example to calculate the temperature change and
distribution during SAGD circulation phase and the results are compared with those from previous model and numerical history
match. The calculation results show that the analytical results from the model proposed in this paper have quite good agreement
(>95%) with the numerical simulation results，which justifies its feasibility and accuracy. The heat communication during
SAGD circulation phase can be determined timely by using this model and it has a significance to guide the SAGD operation
during production phase successfully.

Analytical Solution for Double-horizontal-well SAGD Electric#br# Preheating Model of Heavy Oil Reservoirs

WEI Shaolei1*, Cheng Linsong2, ZHANG Huideng2, HUANG Shijun2

2016, 38(1):  92-98.  DOI: 10.11885/j.issn.1674-5086.2013.12.18.07

Asbtract ( 272 )   HTML   PDF (532KB) ( 776 )  

References | Related Articles | Metrics

There are two preheating methods for steam assisted gravity drainage（SAGD），namely the steam circulation method
and electric preheating method. Compared with the steam circulation method，reservoir heterogeneity has a smaller influence
on the electric preheating method and the formation nearby horizontal wells can be heated evenly. Therefore，the viscosity
of oil is reduced and flowing capacity is improved. A mathematical model for SAGD electric preheating method is built and
solved analytically. According to the special well pattern，the superposition principle is employed to deal with the multi-well
interference problem. Meanwhile，variable electric power injection situation is handled. Temperature distribution at different
time is obtained with the new model. The preheating time can be predicted at a given electric power injection mode. The
research shows that in the case of constant total electric energy，increasing the electric power gradually in preheating is the best
injection method and the temperature between wells rises higher than any other injection methods.

A Full Cycle Productivity Prediction Model of Fractured Horizontal#br# Well in Tight Oil Reservoirs

WEI Yi1，2*, RAN Qiquan1，2, TONG Min1，2, WANG Zhiping1，2

2016, 38(1):  99-106.  DOI: 10.11885/j.issn.1674-5086.2013.11.14.03

Asbtract ( 239 )   HTML   PDF (786KB) ( 777 )  

References | Related Articles | Metrics

In tight oil reservoirs，the pore throat is of nano/micro-scale，the seepage channel is narrow，and the particle size
is small. As a result，the physical characteristics of reservoirs is very poor，and the microscale effect is significant. The
percolation is strongly affected by the matrix and fracture deformation. Due to complex reservoir characteristics and percolation
mechanism，the drainage radius in the matrix is small，there isn′t natural production capacity，which makes it difficult to
effectively develop tight oil reservoir. At present，the long horizontal well drilling technology with volume hydraulic fracturing
has been widely used to realize economic and economic development of tight oil. Under this mode，the production process can
be divided into three stages：early stage，transition period，and late stage. Accordingly，the flow field of fractured horizontal well
is divided into three regions，in which flow medium，seepage mechanism，and factors affecting the productivity are different. To
be consistent with the actual production，the productivity equations of three stages were established respectively，and eventually
a full cycle productivity prediction model was established considering the whole production process. By applying the model to
practical examples，calculated values are basically similar to actual values. The results show that the model can be applied to
practical tight oil reservoirs to predict the productivity of fracturing horizontal wells and analyze the effects of some factors on
oil production，thus the results of analysis play a guiding role in the development of tight oil reservoirs.

Modified Isothermal Adsorption Model of Shale Gas

ZHANG Yuelei1，2，3*, LI Dahua1，2，3, WANG Qinghua4, GUO Dongxin1，2，3

2016, 38(1):  107-112.  DOI: 10.11885/j.issn.1674-5086.2013.11.05.05

Asbtract ( 274 )   HTML   PDF (512KB) ( 959 )  

References | Related Articles | Metrics

When using Langmuir model and modified double Langmuir model on heterogeneity medium shale isotherm adsorption，
the experimental data fitting accuracy and stability is not high. We launched a study on new isotherm adsorption
equation. The study transforms the adsorption characteristics of different adsorption media within the adsorption system into
the actual effect of system pressure，and corrects the pressure for double Langmuir model，getting a new P-Langmuir isotherm
adsorption model，which is suitable for multi-adsorption-media system. The model is applied to fitting adsorption isotherm
experimental data of 21 samples of Yuye 1 shale gas well in the Southeast of Chongqing and the result shows that average errors
of Langmuir model are between -0.012 8 m3/t and 0.021 2 m3/t，D-Langmuir model between -0.003 64 m3/t and 0.021 2 m3/t，
and all the values of the correlation coefficient R2 of the P-Langmuir model are between 0.992 5 and 0.999 8，and that average
errors of 21 samples are between -0.003 25 m3/t and 0.003 21 m3/t. Compared to the Langmuir equation and double Langmuir
equation，P-Langmuir model is of higher fitting accuracy and better stability，has some practical significance for more
accurately evaluating shale gas adsorption.

A Study on Temperature Effect of Water Displacement Efficiency in High#br# Pour Point Oil Reservoir

XU Feng1，2*, WU Xianghong2, MA Kai2, FENG Min2, TIAN Xiao2

2016, 38(1):  113-118.  DOI: 10.11885/j.issn.1674-5086.2013.12.02.08

Asbtract ( 324 )   HTML   PDF (485KB) ( 779 )  

References | Related Articles | Metrics

Temperature has a great effect on the rheological property of high pour point oil because of its high wax content and
high pour point. During the development of high pour point oil reservoir，wax precipitation easily occurs in the conventional
water flooding process，leading to low efficiency of water flooding，which has direct impacts on the development performances.
A series of laboratory experiments are conducted under circumstances where temperatures of injected water are different to
study the influence of temperature on the water displacement efficiency in the P high pour point oil reservoir，South Sudan.
The experiments include：one-dimensional long core live oil experiment，one-dimensional long core degassed oil experiment
and one-dimensional short core degassed oil experiment. In addition，a 3D four-phase pseudo-component model is established.
Wax precipitation is designed in the simulation model，and all the key factors are considered in the high pour point oil reservoir
simulation，making the predicting results more accurate. Laboratory investigation and numerical simulation results show that
the temperature has great impacts on the water displacement efficiency before the wax appearance temperature (WAT). When
the temperature is higher than WAT，oil viscosity is less sensitive to temperature with the temperature increasing，and the rate
of increased oil displacement efficiency decreases. So it is suggested that water temperature should be higher than WAT.

NMR Analysis of Movable Remaining Oil of Low Pemeability Reservoir

LI Haibo1，2，3*, GUO Hekun1，3, ZHOU Shangwen1, MENG Zhiqiang2，3, WANG Xuewu1，3

2016, 38(1):  119-127.  DOI: 10.11885/j.issn.1674-5086.2014.06.04.01

Asbtract ( 271 )   HTML   PDF (453KB) ( 1132 )  

References | Related Articles | Metrics

This study analyzes oil-water saturation of reservoir and high-speed centrifugal oil-water displacement experiment
by NMR respectively aiming at representative Parallel cores form sealed coring，and establishes NMR method for reservoir
movable remaining oil saturation analysis through quantitatively comparing parameters，which include reservoir remaining oil
saturation at present，relative quantity of produced oil，movable oil saturation and upper efficiency of oil displacement. The
research shows that the best centrifugal forces to set up saturated oil bound water state and to drive oil are 2.250 MPa and
0.220 MPa respectively. For four permeability level（>50、[10，50）、[1，10）and <1 mD）reservoir，produced oil saturation
are 23.49%，16.81%，8.70% and 9.99% respectively；movable oil saturation are 50.34%，43.76%，29.67% and 22.89% respectively，
and movable remaining oil saturation are 26.85%，26.95%，20.97% and 12.90% respectively. Produced oil saturation
of reservoir above 10 mD is higher than that of reservoir less 10 mD，which is obviously due to reservoir heterogeneity，but
movable remaining oil saturation of reservoir greater than 10 mD is higher because of its higher movable oil saturation. Movable
remaining oil saturation of reservoir less than 1 mD is lower than that of other reservoirs evidently.

Dynamic Simulation of the Open Process for Natural Gas Wells to#br# Inhibit Hydrate Freeze-plugging

CEN Kang1*, JIANG Xin1, YANG Jing2, ZHU Yuanxing1

2016, 38(1):  128-139.  DOI: 10.11885/j.issn.1674-5086.2013.10.31.06

Asbtract ( 312 )   HTML   PDF (1849KB) ( 801 )  

References | Related Articles | Metrics

The hydrate freeze-plugging phenomenon is easy to occur in pipelines during the open period of natural gas wells
especially for wells with high pressure. The dynamic characteristics and optimal hydrate control schemes during well opening
period，however，have not been studied systematically. So the specific dynamic models have been established to analyze
the dynamic characteristics during well opening period by Dynsim package. The influences of the fluid flowrate，installation
modes of pipelines，thickness of thermal insulation layer as well as throttling regulation schemes on throttling temperature and
pressure during well opening period have been discussed by using the dynamic models. The dynamic characteristics of heat
transfer between fluid in pipelines and ambient environment during well opening period have also been analyzed. In addition，
the optimal control schemes for hydrate inhibition during well opening period and optimization design for pipelines have also
been put forward in the paper. The results demonstrate that the fluid flowrate during well opening period has dramatical influence
on the risk of hydrate formation in pipelines. And no matter how to regulate the fluid flowrate during well opening period，
hydrate formation risk in pipelines exists all the time，especially when the flowrate remains small. In order to avoid hydrate
formation in pipelines，the fluid flowrate during well opening period should be increased as large as possible by regulating
different throttle valves simultaneously or regulating the secondary and tertiary throttle valves mainly. Meanwhile，necessary
measures like alcohol injection or heating should be done to mitigate the risk of hydrate formation. Furthermore，it is suggested
that the pipelines between wellhead and heating furnace should be buried underground without thermal insulation layer，whereas
other overhead pipelines should be covered by thermal insulation layer.

A Study on Matching Relationship of Polymer Microsphere Size

LIANG Shoucheng1，2*, Lü Xin1，2, LIANG Dan1，2, WEN Hongbin3

2016, 38(1):  140-145.  DOI: 10.11885/j.issn.1674-5086.2013.11.12.03

Asbtract ( 331 )   HTML   PDF (454KB) ( 676 )  

References | Related Articles | Metrics

According to the calculation formula of pore throat size of cores，average pore throat diameter of cores was calculated.
The matching relationship between the pore throat and the polymer microsphere size was researched，through analysis
of plugging effect of polymer microspheres of different sizes injected in cores. The range of ratio of polymer microsphere size
to pore throat diameter of cores was determined when stable plugging performance was obtained. Experiments were conducted
to investigate swelling properties of polymer microspheres，microsphere size change before and after shearing，plugging effect
of different size microspheres，and effect on recovery of profile control of selected polymer microspheres. The experimental
results elucidated the matching relationship between the pore throat and the polymer microsphere size，and provided experimental
evidence for size selection of polymer microsphere under different reservoir conditions. Results show that rational ratio
of polymer microsphere size to pore throat diameter is in the range 0.33～1.50，and then the polymer microsphere has stable plug
effect. When the ratio is in the range of 1.20～1.50，the polymer microsphere has both good plugging effect and good migration
ability.

Wellbore Corrosion Factors Study in NR Oilfield

LI Hongjian1, WANG Run1*, DU Qingzhen2, XIE Gang2, ZHANG Peilun3

2016, 38(1):  146-151.  DOI: 10.11885/j.issn.1674-5086.2013.11.06.02

Asbtract ( 205 )   HTML   PDF (550KB) ( 794 )  

References | Related Articles | Metrics

In view of the increasingly serious problems of corrosion in NR Oilfield，experimental study on wellbore corrosion
of produced water and influence factors of oil well are carried out. Produced water in typical wells is chosen as the research
object，The influence of corrosion time，pH value，CO2 and H2S concentration on the corrosion rate is systematically studied
by the method of static weight loss. Orthogonal experimental study is applied to investigate several factors which influence the
corrosion rate degree. Experimental results suggested that the corrosion rate reaches the maximum when the corrosion reaction
time is 24 h，then with time increasing the corrosion rate gradually decreased，after 72 h，the corrosion rate maintained constant；
The higher temperature the more serious corrosion that the effect of produced water on coupons. When the temperature gradually
increased，corrosion products turned from yellow to black. And dark red flocculent precipitate created in brown red solution.
At 65 ℃ the lower pH the more serious corrosion that the effect of produced water on the corrosion rate. The effect of H2S
concentration and CO2 concentration on corrosion rate is almost the same. The influence of several factors on corrosion rate
determined by the orthogonal experiment are put in the order of temperature，pH value，H2S concentration，CO2 concentration，
which is consistent with the single factor experimental results.

Risk Assessment Method of Gas Field Water Reinjection System in#br# East Sichuan

YANG Zhi1*, KANG Lu1, HOU Pan2, XU Li3, LI Hongzhen3

2016, 38(1):  152-157.  DOI: 10.11885/j.issn.1674-5086.2013.11.20.02

Asbtract ( 199 )   HTML   PDF (369KB) ( 1022 )  

References | Related Articles | Metrics

Water reinjection system has four subsystems，including surface treatment station，water pipelines，reinjection
wellbore and reinjection layers. When a problem develops in any part of any subsystem，the whole water reinjection system
will be paralyzed or lead to great environmental pollution，but there is not a reliable，perfect risk assessment method of gas field
water reinjection system. In this paper，all failure factors and their evaluation standards of each subsystem are summarized，and
the weight of each index is determined according to the statistical results for failure frequency of each failure factor. Complete，
practical risk evaluation method for gas field water reinjection system and each subsystem was established through combining
with the influencing factors evaluation of leakage and referring to Kent risk evaluation model. Meanwhile，two kinds of safety
grade division standard were provided. This evaluation method includes both direct evaluation on the reliability of the system
and the evaluation of the leak consequence；it can not only be used to evaluate of each subsystem but also can be used to evaluate
the whole reinjection system by weighting evaluation results of each subsystem. The risk evaluation of reinjection system in
East Sichuan Gas Fields agree with the on-site observation，which has proved the feasibility of this risk assessment method.

Research on Vibration Damage of Completion String in Yolotan#br# High-yield Gas Well

YANG Mingjun1, LI Haitao1*, JIANG Rui1, XIAO Kaiwen2, XIE Jiang3

2016, 38(1):  158-163.  DOI: 10.11885/j.issn.1674-5086.2014.01.03.03

Asbtract ( 230 )   HTML   PDF (592KB) ( 912 )  

References | Related Articles | Metrics

Yolotan gas field is characterized by high temperature and high pressure gas field. The high-speed gas flow in tubing
may cause erosion damage to the string，and the erosion seriously threats the security of gas production and operation. The
tubing string with packers tends to be buckled，making the fatigue wear more damaging，which is prone to cause downhole
string deformation or damage. Therefore，it is of great significance to study vibration damage and to predict fatigue life of
tubing string. We established finite element vibration model of pipe string with packer in high-yield gas wells by ANSYS. The
results of analysis of the tubing string vibration analysis show that the farther away the pipe string is from the packer the greater
the amplitude of vibration displacement，velocity and acceleration. With detail studies on axial stress，buckling damage and
neutral point changes of the whole sections of the tubing string，and analysis of the contact pressure changes over time between
buckling string and casing string in different locations and different production，this study provides quantitative data for studies
on friction and wear damage mechanism. Finally，we predict the fatigue life of string，which provides theoretical basis for
putting forward string vibration damage prevention measures.

A Rotary Control Head Bearing Temperature Prediction Model Based#br# on GA-BP Algorithm in Underbalanced Drilling

MO Li1*, WANG Jun1, WANG Jun2, WANG Luyou1

2016, 38(1):  164-169.  DOI: 10.11885/j.issn.1674-5086.2013.12.02.04

Asbtract ( 205 )   HTML   PDF (459KB) ( 802 )  

References | Related Articles | Metrics

Rotary contol head（RCH）bearing assembly withstands great dynamic load，and severe heat and abrasion resulting
from the friction force. Shorter equipment life may arise because of bearing failure caused by excessive bearing temperature.
Aiming to overcome the difficulty in precise calculating and measuring，due to various influence factors on RCH bearing
temperature，a method based on GA-BP（the optimized algorithm of BP neural network based on genetic algorithm，GA-BP）is
proposed to predict RCH bearing temperature. The bench test data of an outboard cooling and lubrication pump station RCH
was used for training and testing，and traditional neural network model（BP）was used for comparison. Results show that，the
GA-BP prediction model can realize adaptive control for RCH bearing temperature prediction process. The linear correlation
between prediction value and the expectative output comes up to 0.991 48. 95% confidence interval and mean，max，min
absolute percentage error were contrasted between GA-BP and BP，and the result shows that the approximation capability，
convergence and generalization ability of GA-BP are better than BP. With high prediction accuracy and good stability，GA-BP
model can help monitor the bearing running state，and optimization of the cooling and lubrication stuctures. The GA-BP model
has an important guiding significance in improving the overall performance of RCH.

Research Advances in Measurement and Prediction Models of Crude#br# Oil Fouling Rate Under High Temperature

YUAN Zongming1, WANG Yong1*, XIE Ying1, WANG Dapeng2

2016, 38(1):  170-180.  DOI: 10.11885/j.issn.1674-5086.2013.11.21.04

Asbtract ( 255 )   HTML   PDF (474KB) ( 941 )  

References | Related Articles | Metrics

A comprehensive review in aspect of laboratory measurement and prediction models is conducted in this paper，
and more focus is put on the analysis and development of prediction models. Both experiments and prediction models play
significant role in determining crude oil fouling rate under high temperature. As a quick access to vast amounts of valid data，
laboratory experiments，either batch stirred or recirculation test apparatus cannot directly guide fouling prevention in production.
Proper models must reflect the chemical nature of fouling，the significance of influencing factors such as physical properties，
temperature，flow rate and other different process. Although the threshold models have gained great achievements in field，
which are semi-empirical formula，the precision and applicability of most prediction models at present are limited. More
accurate models must be based on further studies on fouling mechanism. Meanwhile，according to its successful application to
description of the characters of nonlinear systems，the ANN（artificial neural network）will be a new promising prediction skill.