Table of Content

01 August 2016, Volume 38 Issue 4

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Theoretical Analysis of Low Permeability Composite Reservoir Using#br# Finite Element Method

ZHANG Liehui1*, ZHANG Ruihan1, JIANG Hexu2, KONG Ling2, SHE Juan2

2016, 38(4):  1-8.  DOI: 10.11885/j.issn.1674-5086.2014.09.26.02

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Low permeability reservoir has strong heterogeneity and poor property，and stimulation is often needed to achieve
industrial productivity. Based on the heterogeneous reservoirs development practices and the relationship between added resistance
gradient and displacement pressure gradient and mobility，a well test model of added resistance gradient of composite
reservoir is established and solved by finite element method. Then the characteristic curves are gained and analyzed. The
results show that differences between the composite reservoir area have a significant impact on the dynamic characteristics of
the bottom hole pressure. Because of the added resistance gradient，dimensionless pressure and pressure derivative in log-log
well test plot goes upward gradually，but the amplitude is lower than that of the traditional pseudo threshold pressure gradient
method.

The Comparative Study of Natural Gas Accumulation Characteristics#br# Between Puguang and Yuanba Reef-bank Gas Field

DUAN Jinbao*

2016, 38(4):  9-18.  DOI: 10.11885/j.issn.1674-5086.2015.06.17.11

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Systematic correlation between the Puguang and Yuanba Gas Fields can guide the natural gas prospecting in adjacent
area and reef-bank oil-gas field in other basin. Using the chemical and isotopic composition of natural gases，thin sections，
porosity data，and geophysical data，the systematic contrastive research of the origin and resource of nature gas，the scale and
property of reservoir，the trap type and process of migration-accumulation，the tectonic deformation and preservation condition
between Puguang and Yuanba gas field are summarized. The gas reservoir characters are reflected in four aspects. The difference
in carbon isotopic composition of natural gas is related to the thermal evolution and hydrocarbon precursor types of the source
rock. The scale of source rock and hydrocarbon potential of Puguang Gas Field is better than Yuanba. The main reservoir
of Puguang Gas Field is the oolitic beach dolomite of Feixianguan Formation. In contrast，the reef and the backreef beach
dolomite of Changxing Formation is the primary reservoir type of Yuanba. The gas reservoir type of Puguang is structurallithologic
reservoir，however，Yuanba is lithologic gas reservoir，with a relatively weak adjustment and reconstruction in the
late stage than Puguang. Because of the superposition of multi-phase tectonic movement，fault-fracture system is relatively
developed in both Puguang and Yuanba gas field，but regional giant halite cap rock makes most of the gas reserved. The central
position of source rock kitchen and sufficient oil-cracking gas，and unbroken halite cap rock are the key to the formation of the
two gas fields.

Reservoir Characteristics and Main Controlling Factor of the Third#br# Member of Xujiahe Formation in Yuanba Gas Reservo

WANG Hao1，2*, ZHOU Wen2, ZHANG Chong2

2016, 38(4):  19-26.  DOI: 10.11885/j.issn.1674-5086.2014.10.23.04

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Researches have been done on the lithologic character，physical property，reservoir space，and main controlling
factor of the tight sand reservoir of the third member of Xujiahe Formation in Yuanba gas reservoir. The analysis of physical
data and observation of thin section reveals that the lithology of sandstone reservoir is mainly coarse to medium calcarenaceous
sand-stone with some medium to fine detritus quartz sandstone；calcarenaceous sandstone reservoir space is mainly secondary
dissolved pore，with intergranular dissolved pores and crevices. Reservoir property is characteristic of low porosity and high
permeability. Reservoir model is crevice and porosity reservoir. Sedimentary process controls the calcarenaceous sandstone
reservoir development of the third Member of Xujiahe Formation in Yuanba gas reservoir. Underwater distributary channel
deposit is the major microfacies in the calcarenaceous sandstone reservoir. Denudation and tectonic disruption are the major
geologic factors. The research results are of significance in the exploration and development of the third Member of Xujiahe
Formation in Yuanba gas reservoir.

Palaeogene Fault System and Hydrocarbon Accumulation in East#br# Wushi Sag

HU Desheng*, DENG Yong, ZHANG Jianxin, ZUO Qianmei, HE Weijun

2016, 38(4):  27-36.  DOI: 10.11885/j.issn.1674-5086.2014.11.07.01

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Paleogene complex fault system has always been a key factor in the success of oil and gas exploration in East Wushi
Sag. In this article the time of faults movement，their classification and the structural evolution are studied. The results show
that the evolution of East Wushi sag can be divided into weak rifting stage in Paleocene -Early Eocene，strong rifting stage in
Middle-Late Eocene and strike-slip weak stretching stage in Oligocene. Besides，3 sets of fault systems can be recognized：
the early fault system formed in Changliu Formation to Liushagang Section 3 Formation sedimentary stage（T100 T86），the
late fault system formed during Liushagang Section 2 Formation to Weizhou Formation sedimentary stage（T83 T60）and
succession fault system formed in all the Palaeogene time（T100 T86）. In addition，stretching structure，strike-slip structure and
inversion structure have been found in study area. While the tectonic controls on the distribution of source rock and the filling
evolution of sediment systems has been discussed，as well as the fault activity impacts on the trap formation，distribution，and
the accumulation of hydrocarbon. Based on the analysis of the elements of reservoir formation，the central uplift and the north
tilted fault block are the favorable prospecting areas. And the research has some guidance and reference value for the future oil
and gas exploration，target evaluation and preference，and geological research.

Geological Modeling of Fractured Volcanic Reservoir in Jinlong2#br# Oilfield，Xinjiang

DENG Xili1，2*, LI Shunming1, KONG Chuixian3, HE Hui1, JIANG Qingping3

2016, 38(4):  37-47.  DOI: 10.11885/j.issn.1674-5086.2014.11.17.01

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Recent years，the volcanic reservoirs of Jiamuhe Formationin the eastern slope belt of Zhongguai Uplift，northwestern
Junggar Basin，are key blocks for increasing storage and production in Xinjiang Oilfield. The geological modeling
of this area are made difficult by factors such as volcanic lithological facies and volcanic architecture identification，fracture
characterization and multi-medium parameter processing. This paper，based on lithological facies identification，elaborately
characterizes and quantitatively predicts the fractures by means of conventional loggings，FMI，pre-and post-stack seismic data.
Offset cut-off processing，azimuth non-equalization，super-bin stack and cokriging correction are adopted to assure the accuracy
of fracture prediction by pre-stack azimuth anisotropy. In the end，we applied the methodology of“hierarchy modeling+ equivalent
processing”to establishing a tectonic model reflecting fault-fracture system feature and an equivalent continuum parameter
model reflecting dual-medium flow feature，which lays foundation for fractured volcanic reservoir numerical simulation.

Relationship Between Unusual Index of Soil Acid Hydrolysis#br# Hydrocarbon and Chang 8 Oil Pool in Xifeng Oil Area

CHENG Dangxing1，2*, DENG Xiuqin1，2, SUN Bo1，2, LI Jihong1，2, GUO Zhengquan1，2

2016, 38(4):  48-55.  DOI: 10.11885/j.issn.1674-5086.2014.04.05.05

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Based on the three longitudinal and a transverse geochemistry section data in Xifeng area，the article intends to test
the applicability of acid hydrolysis hydrocarbon to oil exploration in Ordos Basin. By analyzing the interference factors，the
background level and geochemistry threshold on geochemistry data，we established the congruent relationship between unusual
index of soil acid hydrolysis hydrocarbon and deep Chang 8 oil pool in Yanchang deposit. The results show that the unusual
geochemistry index of heavy hydrocarbon is consistent with that of soil acid hydrolysis hydrocarbon methane and correspond
well with the deep Chang 8 oil pool. The high geochemistry unusual level of methane and heavy hydrocarbon geochemical
index often correspond with oilfield scale reserve area or industrial oil flow area，while the lower geochemistry unusual level
always corresponds with areas of bad or no indication of oil and gas.

The Inner Architecture of Debouch Bar Reservoir and its Influence on#br# Remaining Oil Distribution

YANG Shengxian*, YAN Ke

2016, 38(4):  56-62.  DOI: 10.11885/j.issn.1674-5086.2014.06.26.04

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In order to reveal the inner structure of debouch bar reservoir，to enhance the accuracy of remaining oil description，
and to guide reservoir development and adjustment，a typical debouch bar of delta front reservoir in the Es2−8 Formation of
Shengtuo Oilfield was characterized by close spacing architectural analysis. The study shows that the depositional interfaces
in debouch bar can be classified into 5 levels. The fifth level interface restricts the composite debouch bar，which is thick
stable mudstone. The top boundary of the fifth level interface presents a nearly horizontal attitude，and the bottom boundary
presents an S shape attitude. The fourth level interface restricts the single debouch bar，which is mainly the muddy or calcareous
intercalation with inclined attitude in the slope break belt，and a nearly horizontal attitude in the lake floor plain. The S shape
foreset configuration and the independent sand body in contemporaneous deposit are the essential architectural features of the
single debouch bar. The third level interface restricts the accretion sand body in the single debouch bar，the attitude of which
is oblique or parallel with the fourth level interface. There are two kinds of foreset configuration in the accretion sand body. S
shape and oblique crossing shape. At the later stage of extra-high water cut，the inner structure of the debouch bar reservoir
displays a very high efficiency control effect on remaining oil distribution. The ubiquitous S shape forest configuration controls
the low saturation and homogeneous distribution of the remaining oil；the regional oblique crossing shape foreset configuration
controls the differential distribution of the remaining oil，and the architecture of independent sand body in contemporaneous
deposit controls the sectional enrichment of the remaining oil.

Mechanism and Process Analysis of Calcareous Precipitation in the#br# Syndepositional Stage

SHAN Jingfu1*, ZHANG Qian2, PENG Miao2, GUO Bing3, GAO Huaixi4

2016, 38(4):  63-70.  DOI: 10.11885/j.issn.1674-5086.2014.10.22.02

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The caliche in the superficial arcose in paleodepositional environments is one of the important factors affecting
reservoir physical property. In paleodepositional surface environments，the concentration of calcium is generally in the form
of plates and flakes. The paper points out the origin of the Ca2+，the conditions of the concentration of the Ca2+ and the
mechanism and dominant factors of the caliche formation through physical-chemical study. The results show that the Ca2+
is dissociated from silicon aluminate particles，which is closely connected with the existence of the atmospheric acidic water.
When the climate is dry，with the evaporation larger than precipitation，the lake surface keeps decreasing，the river diverts or
the transition flow blocked，etc.，which are all beneficial for the decomposition of the heavy calcium carbonate，thus making
the plate-like and flaky caliches widely scattered. Therefore，we hold that a clear understanding of the mechanism and dominant
factors of calcium concentration is of significance in the efficient exploitation in the late period of production.

Seismic Attribute Analysis of Shallow-water Deltaic Sand Body Prediction

LIU Hao1, GUO Yishan2*, ZHAO Chunchen3, XIA Yueyang1

2016, 38(4):  71-81.  DOI: 10.11885/j.issn.1674-5086.2014.10.31.07

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The shallow-water deltaic sand body is excellent reservoir in Neogene strata of the Bohai Bay. However，as there is a
lack of well data in the new 3D seismic survey，the relation between the shallow-water deltaic sand bodies and seismic responses
is still obscure. It is difficult to depict the sand bodies precisely. In order to discuss the parasequence sand body distribution in
work area X in Huanghekou sag，this paper summarizes the relationship between the lithological combinations and the seismic
attributes in lower Minghuazhen submember ，based on the high-frequency sequences division. Using the seismic forward
modeling，the we establish the geophysical model of sand bodies and depicts the pss1 pss11 level sequence sand bodies of
Minghuazhen submember in a deliberate way，by making use of RMS amplitude attributes of 90? phase conversion seismic
data. The result proves the relationship between the amplitude of seismic profiles and sand body concentration. The high RMS
amplitude figure demonstrates the thick sand bodies（or the corresponding compound thick level）. The middle amplitude figure
normally corresponds to massive mudstone clipping thick-middle thick sandstones，and low amplitude figure shows the barely
developed sand bodies. These results match noticeably with the well drilling s data. Therefore，it is feasible to predict the
shallow-water deltaic sand body by using the seismic attributes.

Quantitative Evaluation of Carbon Dioxide Content in Natural#br# Gas Reservoir with Logging Data

HE Shenglin1, ZHAO Jun2*, ZHOU Jiaxiong1, ZHANG Hairong1, WANG Di2

2016, 38(4):  82-88.  DOI: 10.11885/j.issn.1674-5086.2014.06.05.01

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When carbon dioxide exists in gas zone，pore fluid composition and logging response are getting more complex
because of the presence of hydrocarbon gas，non-hydrocarbon gas and irreducible water. The extra conductivity caused by the
dissolution of carbon dioxide is absolutely weak and no apparent regulation exists in it，which makes qualitative identification
and quantitative calculation of carbon dioxide very difficult. According to the different influence of methane and carbon dioxide
on thermal neutron moderation and diffusion，this paper builds the carbon dioxide quantitative calculation model with porosity
logging methods based on neutron′s long and short spacing counting rates. Then，in consideration of the logging response
features of methane and carbon dioxide with reservoir at high temperature and high pressure，and by using porosity and saturation
data，we adopted the optimization method based on rock′s physical volume model and calculated the content of each fluid
composition. The effect is proven to be reliable through comparison between the interpretation results and testing conclusion.

Thermal Recovery Effect Evaluation of Multi-thermal Fluid#br# Stimulation in Offshore Heavy Oilfield

ZHU Guojin, YU Huajie*, ZHENG Wei, TAN Xianhong, WANG Lei

2016, 38(4):  89-94.  DOI: 10.11885/j.issn.1674-5086.2014.03.28.02

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Oilfield A is the first pilot test spot of thermal recovery in offshore unconventional heavy oil field. The development
effect will directly affect the future development of offshore unconventional heavy oil resources. Based on production performance
of thermal recovery well in Oilfield A，the influence of edge water on the development effect of thermal recovery wells
was analyzed，and we proposed distance from thermal recovery well to edge water to be more than 200～300 m. A comparison
between normal and thermal production of the same well，and between the production of thermal recovery well and adjacent
normal production well in the same layer showed that early productivity and the first annual oil production of thermal recovery
wells are both 1.5 to 2.0 times as normal production wells. Integrated evaluation method was performed using bottom hole
temperature and productivity index data，and we analyzed the valid period of thermal recovery well，which is between 240 to
339 days，298 days on average. The values of cycle average capacity，oil production and oil-steam ratio were compared to the
pre-drilling design value，and the results showed that without considering sand control technology，drill string problems and
reservoir property change，thermal recovery wells have reached the expected results of the first cycle，with the average capacity
of 5 m3/d，cycle oil production of 1.80×104 m3；and the incremental oil production of 0.7×104 m3. The thermal recovery effect
of multi-thermal fluid stimulation is obvious，and will guide the development of other offshore unconventional heavy oil field.

Influence of Stress-sensitivity on Development Index in Dongfang 1—1#br# Gas Field

GUO Ping1*, ZHAO Zihan1，2, WANG Zhouhua1, LEI Hao3, YANG Yang4

2016, 38(4):  95-100.  DOI: 10.11885/j.issn.1674-5086.2014.07.10.02

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Medium deep Huangliu Formation in the Dongfang 1-1 gas field is a typical reservoir of abnormally high pressure.
The pressure coefficient is at 1.9～2.3，so it is stress sensitive in development. By means of laboratory core experiments and
numerical simulation，we carried out a systematic research in order to understand the effect of stress sensibility of this field
on production performance. The research reveals that the variation of confining pressure and permeability showed relatively
regular exponential variations. As stress-sensitivity has influence on gas well pressure distribution and the pressure drop funnel，
differential pressure is the biggest near the well bore. Because of the stress-sensitivity，the period of stabilized production of the
Dongfang gas field becomes 5.00 years from 5.75 years，and the final recovery of this field decreased by 1.92%. These results
offer a very important guidance for researching and designing production performance of a gas reservoir with abnormally high
pressure.

Research on Well Patterns and Fracture Models for Fractured#br# Horizontal Well in Ultra-low Permeability Reservoir

TAO Zhen*, TIAN Changbing, XIONG Chunming, ZHAO Ruidong

2016, 38(4):  101-109.  DOI: 10.11885/j.issn.1674-5086.2014.05.05.02

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In order to extend the water-free production period，to improve well production and oil recovery，and to reduce water
cut rising of fractured horizontal well，the formula of water flooding front is deduced in this article，and the horizontal well
patterns，fracture models，horizontal section length，fracture penetration ratio and the row spacing are optimized by reservoir
numerical simulation and reservoir engineering. The results show that the five-spot well pattern is of higher oil recovery and
lower water cut rising，compared with the seven-spot well pattern. Among the equal-length fracture model，dumbbell-shaped
model and spindle-shaped model，the spindle-shaped model gives the highest cumulative oil production，oil recovery and the
longest water-free production period，and the spindle-shaped model gives the lowest water cut with the same oil recovery. In
the ultra-low permeability reservoir，the shorter the horizontal section，the higher the oil recovery. When the horizontal length
is more than 500 m，the payback period increases and the net present value decreases with the increase of horizontal length.
When the optimal fracture penetration ratio is 0.7，the optimal row space is 300 m. The results have certain significance for
researches on horizontal well patterns and fracture models of similar reservoirs.

Experimental Researches on Relative Permeability Curve of Complex#br# Fracture System

PAN Yi1*, WANG Panrong2, SONG Daowan3, DONG Yajuan3, SUN Lei1

2016, 38(4):  110-116.  DOI: 10.11885/j.issn.1674-5086.2014.05.26.05

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Oil-water relative permeability curve of fracture system is very important in the waterflooding process of naturally
fractured reservoirs. We designed and made a series of large size physical model of fracture system based on the geological
charac- teristics of a certain fractured carbonate reservoir. Oil-water relative permeability curves were measured by using
unsteady-state method．The influence of fracture density and average fracture aperture on oil-water relative permeability curves
was studied. The results show that the shape of relative permeability curve is close to X curve type，and common percolation area
of two phases turns wide. When the irreducible water saturation increases，the common percolation area of two phases reduces
with the fracture density growing. With greater fracture density，the structure becomes more complex，the irreducible water
saturation in the phase permeability curve greater，and the range of the two-phase percolation area smaller，and the position of
the seepage point gradually moves to the right.

The Impact of Longtime Shutdown on Oilfield Development Discipline

LI Yuhong*, CHANG Yuwen, WU Xianghong, FENG Min, HUANG Qizhi

2016, 38(4):  117-122.  DOI: 10.11885/j.issn.1674-5086.2014.12.30.04

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Long time shutdown of oilfield has a significant influence on oilfield development discipline，recoverable reserves
and recovery ratio. It is an important factor in the adjustment of oilfield development. By analyzing the production performance
before and after the shutdown period and by comparing the oil rate and water cut performance，the oil rate profile influenced by
the shutdown of the oilfield was studied. This study starts from the practical situation of oil reservoirs and lays an emphasis on
practical oilfield production data analysis. The curve of water-cut vs. recovery percent of reserves，the dimensionless forecasting
models，the production decline model and water flooding curves were applied to predict the recoverable reserves and recovery
ratio before and after the shutdown period. In addition，by mutual authentication of different reservoir engineering methods，
the impact of the longtime shutdown on the oilfield development and reservoir characteristics can be analyzed. It has shown
some positive outcomes because of the buildup of the producing energy，the redistribution and movement of the underground
fluid. This research fills the gap in researches on influence of long-term shutdown and provides a new angle of analyzing oilfield
discipline in similar oil reservoirs.

Research on Formation Pressure Predictionin in Ansai Area Infilling

WANG Yongming1，2*, WU Xuesheng1，2, ZHOU Wenjun1，2

2016, 38(4):  123-129.  DOI: 10.11885/j.issn.1674-5086.2014.06.09.03

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Ansai Oilfield infill experimental zone is located in the mid-west Wangyao zone. After long-time development，the
composite water cut reaches 58.9%，geological reserves recovery degree 11.8%；formation pressure system is in disorder，and
natural fracture and fracture cracks co-exist. Therefore，the prediction of formation pressure of encryption test wells is difficult
and drilling safety is at risk. Based on the analysis of Ansai experimental area and on the basis of geological characteristics，we
studied the difference between formation pressure in the process of water injection and the original formation pressure，trying
to accurately determine reservoir pressure distribution water after injection. We introduced the seepage theory of fractured
formation after water injection in the process of the formation pressure prediction，and suggest calculation method for infilled
wellbore formation permeability tensor of complex crack formation and prediction methods for infilling of formation pressure.
Applying these methods to the prediction of formation pressure of experimental zone in Ansai produced highly accurate results
that satisfy the need of safe drilling fluid density window The influence of the characteristic of cracks on infill well formation
pressure is also analyzed，which can provide practical guidance for infill well drilling safety.

A Bottomhole Drillability Model in Spherical Symmetric Coordinates

SHI Xiangchao1*, TAO Zuwen1，2, MENG Yingfeng1, ZHAO Xiangyang1，3, TAO Yun4

2016, 38(4):  130-135.  DOI: 10.11885/j.issn.1674-5086.2014.09.03.05

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Aiming at bottomhole drillability in complex stress conditions，experimental and theoretical studies were carried
out in this paper，including drillability and uniaxial compressive strength tests. A bottomhole drillability model was established
in spherical symmetric coordinates，based on the elasticity theory and Drucker-Prager strength criterion. A case was done
according to the drillability test data and well logging data from sandstone reservoir in Xujiahe group. The results show that
bottomhole drillability increases with the increase of fluid column pressure in wellbore. Bottomhole drillability also increases
along the radial direction. This drillability model can well reflect the law of bottomhole drillability and contributes to BHA
optimization design.

Division of Oxidation Stage of Heavy Oil in the Process of#br# in-situ Combustion

JIANG Haiyan1，2*, YUAN Shibao1，2, LI Yang3, NAN Yefei4, WANG Peng5

2016, 38(4):  136-142.  DOI: 10.11885/j.issn.1674-5086.2014.09.09.05

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In-situ combustion is an important replacement method for heavy oil steam stimulation. The division of the reaction
stage of heavy oil oxidation has great influence on the ignition of in-situ combustion and even production. Thermogravimetric（
TG）experiment was conducted to study the oxidation process of a certain heavy oil sample mixed with quartz sand，
and the oxidation process was described in detail by combining the multi-peak shape of thermal weight loss rate curve with
Multi-component oxidation theory of heavy oil，and four stages of weight loss were identified：earlier LTO（low temperature
oxidation），later LTO，fuel deposition and HTO（high temperature oxidation），and the demarcation points were clearly defined.
Compared with the conventional understanding of the three stage oxidation of heavy oil，the four stage method is more capable
of describing the characteristics of low temperature range，long time consuming and complex reaction. The Flynn-Wall-Ozawa
method is used to calculate the activation energy of each stage，which is quite different from that of the conventional division.
The results have reference value for heat supply in ignition period of in-situ combustion of heavy oil reservoir.

Study on Barium Sulfate Scale Model Based on Chemical Kinetics

LI Hongjian1*, CHEN Man1, SHI Xiangchao1, TANG Xin2, WANG Deyu2

2016, 38(4):  143-148.  DOI: 10.11885/j.issn.1674-5086.2014.01.08.04

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Reaction of ions in porous media were not the same as in common water solution Diffusion and reaction coefficients
in porous media had to be calculated by fitting core scale model with measured outlet barium concentration in core flooding
test. The original solvers of both core and formation scale model made the assumptions that barium and sulfate ion ratio should
be far less than 1，which largely restricted the model′s application. By using Lobatto and Newton methods to solve core scale
model without the assumption upon ion ratio we obtained the formation scale model，and modified the coefficient of second
order term in the control equation. We also studied the effects of different dimensionless diffusion coefficients，dimensionless
reaction coefficients and influence of ion ratios on impedance coefficient of formation scale model when injecting low sulfate
seawater. The results showed that low sulfate seawater could greatly lower the ion ratio and would decrease the impedance
coefficient greatly，and that with the same percentage of decrease in ion ratio and dimensionless reaction coefficient，the former
would result in greater reduction of impedance coefficient.

Research of Dynamic Frictional Drag and Deformation of Running Drill#br# String in Liner Cementing

LIAN Zhanghua1*, ZHENG Jianxiang1, ZHANG Ying1, SHI Lei2, MU Fengying3

2016, 38(4):  149-156.  DOI: 10.11885/j.issn.1674-5086.2014.04.18.03

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This paper systematically studies the dynamic frictional drag and deformation of running drill string in liner cementing.
The objective of the research is to evaluate the safety of the running drill string in liner cementing. At first，according to
the structure size of drill string assembly and wellbore configuration size，the mechanical model of drill string under the fluid
frictional drag was constructed，and the analytical mathematical model of the frictional drag and deformation of drill string
caused by the flow of injected fluid in liner cementing was derived. And then，based on the structure size of drill string assembly
and the fluid property of multi-densities and variable volume fluids in drill string，the analytical mathematical model of the
depth of multi-densities fluid varying with the injecting time was deduced. Based on these mathematical models，the software，
which evaluates the safety of the running drill string in liner cementing，was applied to well LG63 in Sichuan，and proved to be
reliable and applicable. The research results indicate that under the action of the multi-densities fluid in the running drill string，
the mathematical models and the software can find out the pumping fluid rate when the alternate load occurs in the running drill
string，and optimize the parameters of safe operation of the running drill string. It provides a reliable means and approach for
the safety evaluation of running drill string caused by the dynamic frictional drag and deformation string in liner cementing.

Method for Field Evaluation of Drag Reduction Effect of Natural Gas#br# Drag Reduction Agent

HUANG Zhiqiang1, MA Yachao1, LI Qin1*, WANG Nan1, CHANG Weichun2

2016, 38(4):  157-165.  DOI: 10.11885/j.issn.1674-5086.2014.02.20.03

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The appropriate use of natural gas DRA can effectively reduce the energy consumption during long-distance transportation
and improve the capacity of the pipeline. Scientific evaluation of the drag reduction effect is the key to the appropriate
use of natural gas DRA in the field. However，there exist some limitations in the drag reduction effect evaluation methods
currently used in the field production，thus these evaluation methods cannot meet the need of the pipeline transportation. With
consideration of the drag reduction mechanism and the requirements of pipeline transportation，we analyzed and improved
the three evaluation methods used at home and abroad，and proposed two new evaluation methods. After comparing the five
methods according to the fuzzy comprehensive evaluation theory，we identified the combination of gas transmission efficiency
coefficient evaluation and hydraulic friction coefficient evaluation as the most appropriate evaluation method. Based on the
research results，we developed a natural gas pipeline DRA drag reduction evaluation software. The test results of the software
from the application to a gas pipeline not only agreed well with the actual situation，but also met the need of both the technical
officers and the production managers. The software is approved by the field staff as it was simple and easy to use.

Research on Allowable Movement Speeds of Downward Drill Pipe in#br# Gasliquid Two Phase in MFC Drilling Operations

KONG Xiangwei1，2*, LIN Yuanhua2, HE Qiuyun3, QIU Yijie2

2016, 38(4):  166-172.  DOI: 10.11885/j.issn.1674-5086.2014.04.27.02

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For the problems of allowable downward movement speed of drill pipe in gas-mud two phase during MFC drilling
operations，this paper establishes the semi-empirical model for allowable downward movement speeds of drill pipe at different
well depth by considering gas slippage，resistance between flowing phase and annulus wall，back pressure and pressure
difference in bottom hole. The variation characteristics of allowable downward movement speeds of drill pipe are acquired by
adopting the method of computer programming. The results show that when the drill pipe moving downward，increasing back
pressure will lead to the decrease of void fraction，increase of gas-liquid two-phase density and effective pressure imposed on
the bottom hole，which will further result in the decrease of allowable downward movement speeds of drill pipe. When the
gas influx rate in the bottom hole is increased，the pressure in bottom hole will be reduced to less than the formation pressure.
At that time，the allowable downward movement speeds of drill pipe can be increased because the increasing surge pressure
can eliminate a part of pressure difference between bottom hole and formation. The allowable downward movement speeds of
drill pipe should be decreased with the decrease of safety pressure difference. During the MFC drilling operation，the precise
calculation of allowable downward movement speeds of drill pipe can improve the effectiveness of drilling.

Diagenesis and Porosity Evolution of Kepingtage Formation in#br# Shuntuoguole Block

PENG Jun1, ZHANG Hanbing1*, LU Ming2, LI Bin1, XIA Qingsong1

2016, 38(4):  173-182.  DOI: 10.11885/j.issn.1674-5086.2015.12.28.03

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This paper systematically studies the diagenetic types，classification of diagenetic stages and diagenetic sequences，
and builds the porosity evolution process. The study shows that the Kepingtage Formation reservoir in Shuntuoguole area，
mainly consisting of lithic sandstone，the lithic quartz sandstone and feldspathic litharenite，is poor in physical property. The
reservoir，which is predominantly in diagenetic stage A with some parts reaching diagenetic stage B，was mainly controlled
by compaction，cementation，erosion，metasomatism，hydrocarbon charging，and tectonic fracturing. Multiple diagenesis factors
dominated the reservoir pore evolution：compaction was the most influential with average porosity reduction of 21.82%；
cementation was the secondary with porosity reduction of about 8.18% of which calcareous cementation reduced porosity by
6.06%，and silicic cementation reduced porosity by 1.80% while clay cementation gave insignificant influence；bitumen filling
led to 2.53% porosity loss；erosion increased porosity by 3.91%.