Table of Content

01 June 2016, Volume 38 Issue 3

Previous Issue    Next Issue

Sedimentary Characteristics and Evolution of the Upper Sinian#br# Doushantuo Formation in the North of Middle Yangtze Area

SHAN Changan1, ZHANG Tingshan1*, ZHANG Zhao2, GUO Junjie1，3

2016, 38(3):  1-10.  DOI: 10.11885/j.issn.1674-5086.2014.09.17.02

Asbtract ( 326 )   HTML   PDF (885KB) ( 925 )  

References | Related Articles | Metrics

A large set of dark grey to black colored mudstone and shale deposited in the middle to lower part of the upper
Sinian Doushantuo Formation in the middle Yangtze Platform，most of which are deeply buried in the Basin and with a good
shale gas resource potential. Based on drilling cores and outcrop section investigation，a systematical study on fundamental
geology was carried out. We also analyzed the sequence stratigraphy and sedimentary facies of the Doushantuo Formation，and
established regional stratigraphic framework. The lithology of the upper Sinian Doushantuo Formation is characteristic of four
different lithofacies，and the thickness of which is different in drilling cores and outcrop sections with variation ranges from 90
to 250 m. In general，the stratum is thickening along the direction of northwest to southeast. Doushantuo Formation was divided
into a second-order sequence（SS1），which contains four third-order sequences（SQ1、SQ2、SQ3、SQ4）. Sedimentary facies of
Doushantuo Formation were subdivided into tidal-flat and platform with three subfacies as open platform，shallow water shelf
and intra-platform basin respectively. In Doushantuo period，the sedimentary environments of Doushantuo Formation varied
from southeast to northwest as open platform and restricted platform in the study area，intra-platform basin face in the area of
Huajipo，Well X1 and Jiuliya.

Hydrocarbon Source Evaluation and Oil Source Contrast of the#br# Yanchang Formation in Fu-Huang Exploration Area，Ordos Basin

TANG Jianyun1，2*, SHI Zheng3, SONG Hongxia4, ZHANG Lin1，2, CHEN Yubao5

2016, 38(3):  11-20.  DOI: 10.11885/j.issn.1674-5086.2015.10.20.01

Asbtract ( 297 )   HTML   PDF (491KB) ( 839 )  

References | Related Articles | Metrics

To evaluate the hydrocarbon potential and to establish oil source of oil-bearing series in exploration area，we studied
the hydrocarbon source rock and the crude oil by means of organic petrology and geochemistry. The results show that the
Chang 7 hydrocarbon source rocks are highly abundant in organic matter，and the organic matter is type I II1 of high maturity，
and is good hydrocarbon source rock；the major organic matter type of Chang 6 hydrocarbon source rock is type III II2，
with type I II2 at a minor scale，and is medium-good hydrocarbon source rock with organic matter maturity high maturity；
the Chang4+5 hydrocarbon source rock is of medium high organic matter abundance，mainly with type III，and type II2 at
a minor scale，and is non-poor source rocks organic matter with low-maturity maturity. Crude oil properties of Chang 4+5
and Chang 6 hydrocarbon source rocks are all medium mature oil depositing in continental freshwater lake. Chang4+5，Chang
6 and Chang 7 hydrocarbon source rocks all contribute to the reservoir，among which the Chang 7 hydrocarbon source rocks
contribute the mostand the dark mudstone of Chang4+5 contribute less. The Chang 7 hydrocarbon source rocks found in the
study area expanded the distribution of hydrocarbon source rocks in Ordos Basin，and is of great significance for guiding
thefuther exploration of oilfield.

Recognition of Effective Fractures Within the Oil Shale in the Fourth#br# Member of Funing Formation in Northern Jiangsu Basin

WANG Haifang*

2016, 38(3):  21-27.  DOI: 10.11885/j.issn.1674-5086.2014.08.27.02

Asbtract ( 242 )   HTML   PDF (458KB) ( 951 )  

References | Related Articles | Metrics

To investigate the distribution of shale oil in the fourth Member of Paleogene Funing Formation（E1 f 4）in Northern
Jiangsu Basin，the fractures contained in borehole cores were surveyed and describedin detail；the carbon and oxygen isotopes
within shale matrix and filling calcite were determined，and with consideration of the burial history and hydrocarbon generation
history，the genetic types of fractures and their features are summarized，the formation stages are divided and effective fractures
are discerned. We conclude that the fractures in E1 f 4 can be classified into four categories：strike-slip shear fracture，normal
shear fracture，reverse shear fracture and bedding fracture；the development of fractures can be divided into five stages：on the
first stage strike-slip shear fractures were formed in Wubao movement；on the second stage normal shear fractures were formed
in early Zhenwu movement；on the third stage bedding fractures were formed in mid Sanduo movement；on the fourth stage
normal shear fractures were formed in the late Sanduo movement and on the fifth stage reverse compressional shear fractures
were formed in the end of Sanduo movement. Among these five stages，no oil occurs in the first，second and fifth stages
of fractures while abundant oil appears in the third and fourth stages of fractures with obvious gas logging abnormality and
therefore the third and fourth stages of fractures are effective ones for oil exploration.

Petroleum Geological Condition of Cretaceous in Liupanshan Basin#br# and Favorable Areas Prediction

XIE Qing1*, YANG Xingke1, JIANG Kuan2, YANG Longwei1

2016, 38(3):  28-36.  DOI: 10.11885/j.issn.1674-5086.2016.03.06.03

Asbtract ( 320 )   HTML   PDF (566KB) ( 696 )  

References | Related Articles | Metrics

Liupanshan Basin is located in the joint of southwestern margin of North China block and Qilian - Qinling structure
belt. It′s under a complex system. According to field investigation，there distribute much oil and gas of Cretaceous，which indicates
that the basin has oil production potential. But the entire basin is of low degree of prospecting，and great differences exist
in research data and in determination of target layers of exploration. Using field investigation，experimental analysis methods
and gravity-magnetic materials，in-depth research and evaluation are made on development situation of the hydrocarbon source
rock and characteristics of reservoir and reservoir−forming combination in Cretaceous reservoir，and we get the breakthrough
findings：Liwaxia group belongs to class III medium reservoir，and Madongshan and Naijiahe groups belong to class IV the
poor reservoir；large sets of sandstone development in Paleogene can be a favorable Cretaceous reservoir of oil and gas；organic
matter of the hydrocarbon source rock is of sapropelic-mixed type with high degree of thermal evolution，and is favorable for
hydrocarbon generation. Three kinds of exploration areas and five favorable local tectonic positions have been predicted. The
research results have an important guiding significance to further exploration of oil and gas in Liupanphan Basin.

Method and Development Model of Strata Correlation on Residual Strata#br# of Chunguang Oilfield

LI Weicai1，2*, YANG Xiaopei3, WANG Kejie3, ZHAO Rui4

2016, 38(3):  37-45.  DOI: 10.11885/j.issn.1674-5086.2014.06.04.03

Asbtract ( 186 )   HTML   PDF (2509KB) ( 646 )  

References | Related Articles | Metrics

Chunguang oilfield is located on the Chepaizi uplift in western Junggar Basin，which has undergone multi-phase
intense tectonic movements，and is characteristic of a serious strata loss，and uneven distribution of the residual strata. Using
seismic，core and log data，and based on the stratigraphic base level cycle analysis and on the stratigraphic contact，we made
researches on methods for residual stratigraphic correlation of the Paleogene and Cretaceous strata in Chunguang oilfield，
and established a stratigraphic model，which is instructive to the subdivision and contrast of the residual strata. Results show
that the subdivision and contrast of the Paleogene and Cretaceous strata in Chunguang oilfield can be isochronous，through
the stratigraphic framework established on different levels of sequence boundary identification and analysis of stratigraphic
cyclicity. Comparison methods vary for different genetic types of formations. The strata correlation method and contrast
principle established in the paper are applicable to small layer contrast of Chunguang oilfield，and can be used to effectively
identify the missing formations and thickness of different genetic types of formations.

The Nature and Significance of Shortcut Seismic Reflection in#br# the LS Area in Qiongdongnan Basin

YING Mingxiong*, CHEN Dianyuan, LIU Jianying, LIU Shiyou, CHEN Zuyin

2016, 38(3):  46-54.  DOI: 10.11885/j.issn.1674-5086.2014.09.18.08

Asbtract ( 299 )   HTML   PDF (1469KB) ( 590 )  

References | Related Articles | Metrics

The prestack seismic in COSCO offset gathers low frequency（frequency of 25 Hz），near offset gathers on the performance
of high frequency（frequency reached 45 Hz），and the high-frequency signal attenuates rapidly along offset direction.
We made analysis of prestack speed spectrumand of shortcut；we also carried out forward modeling of drilling data and did a
comparative analysis. The results exclude the possibility of multiple waves of strong near-offset-frequency energy reflection.
As the thin interbedded reservoir distribution in the target area is under the influence of tuning effects，AVO analysis cannot
accurately detect hydrocarbon reservoir. After identifying combinations of reservoir characteristics by forward modeling，we
eliminated the reflective effect of short cut thin bed，and then made AVO analysis of the target area，and finally achieved well
seismic match，which also verified frequency dependent AVO technique is applicable in the region. Besides，we significantly
improved the main frequency of the data after dominant channel stacking，thus improved the accuracy of reservoir prediction
in the horizontal and vertical directions. The results proves the applicability of AVO analysis technology in the target area.

Seismic Description Technique of Turbidite Fan of Dongying Formation in#br# Jinzhou A Area，Northern Liaozhong Subdepression

ZHANG Zhijun*, ZHOU Donghong

2016, 38(3):  55-64.  DOI: 10.11885/j.issn.1674-5086.2014.06.17.02

Asbtract ( 244 )   HTML   PDF (997KB) ( 848 )  

References | Related Articles | Metrics

It is very difficult to identify internal reflection structure and seismic response characteristics of different turbidite
fan in Dongying formation of Jinzhou A area，northern Liaozhong subdepression of Bohai Oilfield. To solve this problem，we
describe turbidite fan by seismic data in this study. Firstly，we study the formation mechanism of the turbidite fan. Secondly，
we analyze the sedimentary characteristics，lithologic structure，well logging and seismic response characteristics of different
sub-facies，based on the typical characteristics of lithology and composite structure of the wells in this area. Thirdly，we build
different types of turbidite fan models for seismic forward modeling，and study the characteristics of the turbidite seismic
response. Finally，we get the plane distribution features of turbidite fan based on different seismic attributes. The research
results predict the favorable reservoir area of the turbidite fan in Dongying formation of Jinzhou A area，northern Liaozhong
subdepression，thus it has a great significance in guiding the exploration in this area.

A Study on Probability Inversion Technology

FAN Tingen1，2*, HUANG Xuri1, HU Guangyi2, WANG Zongjun2, Yin Cheng1

2016, 38(3):  65-74.  DOI: 10.11885/j.issn.1674-5086.2014.11.06.03

Asbtract ( 222 )   HTML   PDF (2178KB) ( 671 )  

References | Related Articles | Metrics

The limited vertical resolution of post-stack constraint sparse pulse inversion method has difficulty meeting the
needs of development. However，by using the probability inversion technique，we get the inversion results by introducing
Bayesian posterior probability to put the uncertainty of seismic，well logs and geology information into probability，and then
we draw random samples from the posterior probability distribution through Markov Chain，and finally make the optimal
expectation obtained by Monte Carlo method as the inversion results. The technology can satisfy the needs of oil development
as it combines the advantages of the high resolution of well with good representation ability of seismic lateral tendency，and can
effectively improve the seismic resolution. The multi-solution of the seismic inversion can be effectively reduced by realizing
lots of equal probability results. The uncertainty analysis of reservoir description is more suitable to geological regularity and
geological understanding when the probability thought is considered. During the research in meandering river sedimentary in
some offshore oilfield，this method has obtained good application effect in sand body superimposed relationship recognition，
sand body boundary recognition，well pattern deployment，and well location optimization.

A Study on Fluid Prediction Based on the Classification of Sensitive#br# Seismic Attributes

ZHAO Zhongquan1*, HE Zhenhua2, WAN Xiaoming1, SHUAI Qingwei1

2016, 38(3):  75-81.  DOI: 10.11885/j.issn.1674-5086.2014.04.13.03

Asbtract ( 218 )   HTML   PDF (767KB) ( 792 )  

References | Related Articles | Metrics

The ability to identify gas-bearing and water-bearing sands of nine fluid identification factors has been compared，
and the results show that the High-Sensitivity-Fluid-Identification-Factor has a strong ability to identify. The neural network
and the Principal-Component-Analysis-neural-network are applied to high-quality 3-D data of HSFIF to perform the waveform
analysis during the gas bearing interval in study area L of basin-S and good mapping effect has been achieved. The facies
maps were analyzed and compared with the logging′interpretation. It proves the application of the PCA-neural network method
can greatly reduce the difficulty of seismic facies interpretation of the map. In this paper，the application range of waveform
classification is extended from seismic-sedimentary-facies analysis and reservoir prediction to the analysis and processing of
the fluid factors in the target layers，thereby we can predict the fluid in layers. It is a new kind of valuable complement to fluid
identification and prediction by using fluid factor only in profile and slice. It is the first time that the waveform classification
techniques has been applied to fluid prediction. We believe that the method along with the results of other explanations has a
guiding significance to reduce exploration risk and enhance drilling success rate.

Analysis of the Spatial Characteristics of Au Elements and Comparative#br# Studies on Anomaly Extraction Method

ZHANG Nannan1，2*, ZHOU Kefa1，2, CHENG Wanwen1，2

2016, 38(3):  82-89.  DOI: 10.11885/j.issn.1674-5086.2014.08.28.03

Asbtract ( 212 )   HTML   PDF (758KB) ( 626 )  

References | Related Articles | Metrics

Extraction of information in geochemical anomalies has long been geologists′concerns. In this paper，we use the
collected 1：20 millions of geochemical data of the western Junggar area to analyze spatial variability of the Au elements，and
interpolate it. By using the C-A model of fractal and the traditional method，we obtain different anomaly threshold values. We
compare the method of extracting geochemical anomalies information based on the traditional method and fractal technique.
The result proves that the spatial distribution of Au elements is characteristic of isotropic with medium correlation；the fractal
method is better than the traditional one. Fractal technology and known gold deposits agree better，as it can avoid the omission
of abnormal information. The result has certain guiding significance for further prospection works in this area.

A Novel Well Productivity Model of Carbonate Reservoir Matrix#br# Acidizing Considering Wormhole

JI Guofa1*, YANG Zhaozhong1, LI Xiaogang1, LIU Wentao2, ZHOU Han3

2016, 38(3):  90-94.  DOI: 10.11885/j.issn.1674-5086.2014.03.06.05

Asbtract ( 252 )   HTML   PDF (362KB) ( 732 )  

References | Related Articles | Metrics

We studied the wormhole effect on the well productivity which conventional well productivity model of matrix
acidizing in carbonate reservoir did not take into consideration. On the basis of the wormhole growth model in radial geometry
and the equivalent permeability model，this paper established a new well productivity model considering wormhole. Based on
the laboratory experiment data of carbonate core displacement by 15% HCl，we selected the optimal acid injection velocity and
the optimal pore volume to breakthrough，and calculated the effective dominant wormhole length and diameter and equivalent
permeability in post-stimulation area near wellbore. Then we calculated the well productivity，and compared it with the real
productivity，and the result shows that when considering the wormhole，the new model is accurate and reliable. This research
presents a new method to predict the well productivity for matrix acidizing in carbonate reservoir.

New WAG Injection Model Based on the Produced Gas Density#br# Variation for Enriched-gas Flooding

WANG Shengkui1，2*, ZHANG Weidong3, YUAN Xiangchun1, WEI Xuguang3, CAI Maojia4

2016, 38(3):  95-100.  DOI: 10.11885/j.issn.1674-5086.2013.12.30.01

Asbtract ( 186 )   HTML   PDF (682KB) ( 821 )  

References | Related Articles | Metrics

When using the WAG models proposed in the literatures，different slug conclusions are obtained by using common
indexes such as oil recovery，TRF，cumulative net cash flow and NPV. The reason is that the WAG design method has
neglected the quantitative relationship between the injected enriched-gas volume and the amount of remaining oil in the swept
region. In this paper，an efficient optimization and design method is proposed and developed for water-alternating-gas injection
model（EWAG）injection process. The proposed technique is able to quantitatively determine the sizes of the enriched-gas slug
and water slug for each cycle of the water-alternating-gas（WAG），as well as the total number of injection cycles. Applying this
method provides this opportunity to implement the WAG scenario more efficiently and economically. The numerical simulation
showed that in comparison with other conventional WAG scenarios with traditional optimization approaches，the EWAG has
the obvious advantages of evaluation indices，such as the oil recovery factor and cumulative net cash flow.

Dynamic Behavior of Drilling Fluid Leakage in Naturally#br# Fractured Formations

LI Daqi1，2*, LIU Sihai1，2, KANG Yili3, ZHANG Hao4

2016, 38(3):  101-106.  DOI: 10.11885/j.issn.1674-5086.2014.06.05.04

Asbtract ( 235 )   HTML   PDF (594KB) ( 787 )  

References | Related Articles | Metrics

Lost circulation usually occurs in naturally fractured formation. It is very important to understand the dynamic behavior
of drilling fluid losses in lost circulation prevention and control. A one-dimensional infinite fracture model for describing
Herschel-Buckley fluid drilling fluid loss was established，and was used to investigate the effect of differential pressure，fracture
aperture and drilling fluid rheological property on fluid loss rate and ultimate loss volume. The results show that the loss
rate curve can be divided into three segments in double logarithmic coordinate. The first and the third segment are straight
line，and the middle segment is an arc. The fluid loss rate increases nonlinearly as fracture aperture and differential pressure
increases，and decreases as consistency factor，flow behavior index，and yield stress increase. Fracture aperture and loss rate do
not conform to the cubic law relationship. Ultimate loss volume increases linearly as the differential and the square of fracture
width increase，and decreases as yield stress and flow behavior index increase，with nothing to do with the consistency factor.
These results are useful to distinguish mud loss types and take reasonable lost circulation prevention and control measures.

Researches on Improving Sweep Efficiency After Water Breakthrough in#br# Ultra-low Permeability Heterogeneous Reservoir

WANG Wei1*, YANG Hui2, HUANG Chunxia1, JIANG Shaojing1, YUE Xiangan3

2016, 38(3):  107-113.  DOI: 10.11885/j.issn.1674-5086.2014.04.13.02

Asbtract ( 294 )   HTML   PDF (694KB) ( 800 )  

References | Related Articles | Metrics

Focusing on the water channeling and the bad results of profile control in ultra-low permeability reservoir，the
laboratory simulation experiments were conducted to study the anti-channeling and expanding sweep volume methods. The
experiments of profile control and oil displacement were run in the reservoir models with interlayer heterogeneity，which shows
that，the water injection pressure after profile control is higher than that in mid-high permeability reservoir，and it is difficult to
improve the sweep efficiency in ultra-low permeability reservoir. Gas flows along water channeling path when injected directly
after water flooding. Injecting gas after profile control can not only reduce the subsequent injection pressure but also improve
the recovery by about 7.8%. The recovery can be improved by about 9.6% in the intermittent gas injection process after gas
flooding. Therefore，injecting gas after profile control can be used after water channeling in ultra-low permeability reservoir to
effectively expand sweep volume and improve the recovery.

The Solution of Composite Reservoir Model Based on Bessel Function of#br# Imaginary Argument SN Algorithm

LI Tiejun*, TONG Liyuan, GUO Dali, CUI Linpeng, YANG Wujian

2016, 38(3):  114-120.  DOI: 10.11885/j.issn.1674-5086.2013.12.19.09

Asbtract ( 226 )   HTML   PDF (649KB) ( 609 )  

References | Related Articles | Metrics

Analytical solution of composite reservoir model which considers wellbore storage and skin effect is complex in
its form and curve shocks occur in the conventional numerical solving process. Therefore，it is necessary to make researches
on accuracy of numerical solution. Firstly，the real space solution is obtained by using the stehfest numerical inversion to the
analytical solution of Laplace space dimensionless pressure. After that，by analyzing the form of the solution，we determine the
solving of the Bessel function of imaginary argument is the key to numerical solution of the model. Then we present sectional
numerical（SN）algorithm of Bessel function of imaginary argument whose calculation accuracy of results can be comparable to
the Matlab. The curves of the infinite，constant pressure and closed outer boundary conditions obtained by the above algorithm
are smooth and complete. What′s more，the program runs fast enough to well satisfy the requirements of well test analysis and
is suitable for composite reservoir well testing analysis.

A Literature Review of Researches on Drillstring Vibration Suppression

DONG Guangjian1*, CHEN Ping1, DENG Yuanzhou2, GUO Zhaoxue1

2016, 38(3):  121-134.  DOI: 10.11885/j.issn.1674-5086.2013.12.19.03

Asbtract ( 279 )   HTML   PDF (887KB) ( 1310 )  

References | Related Articles | Metrics

Control of drill string vibration and shockis an important basis for track optimizing，wellbore design and precise
control，optimization of drilling parameters，improving drilling speed and intelligent drilling. In deep water，ultra-deep water，
deep well，ultra deep well，hard and brittle shale gas formations and gas drilling operations，cluster wells，directional wells
and other special drilling technologies are employed，but these complex wells increases losses by vibration and shock. We
systematically explained and compared the forms and methods of performance evaluation of the drill string vibration and shock
and divided the drill string vibration and shock into passive control，active control and semi-active control. Based on a summarization
and recent classification of critical control methods and the structure and principle of critical controlling equipments，
we focused on the representative achievements and made a comparative analysis of the corresponding methodological characteristics，
equipments and application range，which resulted in the procedures of drill string vibration and shock control and
revealed the direction of future research.

Bubble Rise Velocity in Herchel-Bulkley Fluid of Drilling Annulus

YIN Junyu1，2*, ZHOU Yingcao1, ZHANG Hui2, JIANG Hongwei1, ZHU Lei1，2

2016, 38(3):  135-143.  DOI: 10.11885/j.issn.1674-5086.2014.02.20.01

Asbtract ( 254 )   HTML   PDF (544KB) ( 733 )  

References | Related Articles | Metrics

Bubble motion laws in drilling annulus is an important part of borehole multiphase flow research. Among which
bubble rise velocity is a key parameter. The accuracy of borehole multiphase flow description highly depends on the accuracy
of bubble/gas rise velocity of each flow pattern. In the view of this，according to the void fraction，the drilling annulus flow
is divided into four patterns and then the analysis of bubble or gas motion characteristic of every pattern is carried out. The
calculation methods of single bubble slip velocity and aspect ratio in Infinite media are summarized. Apparent viscosity round
bubbles has been corrected through the Herchel-Bulkley reheology model. Through the contrastive analysis of case study
among several formulas of single bubble′s slip velocity in Herchel-Bulkley fluid，the Rodrigue′s formula is considered as
an improvement compared to the Harmathy′s formula and can be the optimal formula of bubble rise velocity in bubbly flow
pattern. The modification of calculation formulas of bubble slip velocities with regard to void fraction，bubble size and the angle
of borehole has been adopted to correct the slip velocities in four flow patterns. For the bubble slip velocity in the transforming
pattern，the liner method is proposed. The case study is applied in the relationship between bubble rise velocity and void fraction.
Finally，bubble rise velocity can be acquired through the method of drift model

Application of Mixed Integer Linear Program in Optimization of#br# Drilling Rig Mobilization

LIU Ang*, XIE Gang, OU Jin

2016, 38(3):  144-149.  DOI: 10.11885/j.issn.1674-5086.2013.12.04.03

Asbtract ( 213 )   HTML   PDF (327KB) ( 645 )  

References | Related Articles | Metrics

Drilling operation is capital intensive in oilfield development，and drilling rig service fee makes up a major part in
drilling investment. Thus，to assist management in decision making and to improve IRR of the investment，a Mixed Integer
Linear Program（MILP）is proposed to optimize drilling rig mobilization in the development of Halfaya Oilfield in Iraq. Instead
of scheduling rig mobilization for each individual year，the MILP integrates information of the entire development period to
make mobilization plan throughout the whole period. Given the scope of work specified in development plan，the MILP searches
for the optimal solution，namely，the numbers of drilling rigs of each type needed every year，with the objective of minimizing
total cost and meeting annual workload. As expected，the optimal solutions evolve and the objective function improves as
more information is taken into account. In addition，the MILP is adaptive and works well in dynamic setting，such as varying
length of development period and workloads. The paper first introduces linear programming to drilling rig mobilization and
will extend applications of operation research techniques in oil and gas industry.

A Study on Damage Reduction Mechanism of Acid Preflushing During#br# Hydraulic Fracturing

LIU Pingli1*, LAN Xitang2, LI Nianyin1, LUO Zhifeng1, LIU Shujie3

2016, 38(3):  150-155.  DOI: 10.11885/j.issn.1674-5086.2014.03.28.01

Asbtract ( 175 )   HTML   PDF (587KB) ( 671 )  

References | Related Articles | Metrics

Hydraulic fracturing is an effective way to develop low permeability reservoir. However，halfway gelout，fracturing
fluid residue and filtrate damage often reduce stimulation effect. On-site application of acid pretreatment fracturing technology
has been proved to be able to reduce damage during fracturing，but the damage reduction mechanism of acid pretreatment
remains unclear. In this paper，molecular dimensions of guar gum under both conventional and acidic conditions are quantitatively
observed by using laser particle analyzer（LPSA）. Principle factors affecting the damage of gelout fluid to matrix in
acidic environment are also researched here. In addition，microanalysis of damaged core edge after injecting gelout fluid and
acid fluid is conducted by means of scanning electron microscope（SEM）. We can draw conclusions from the results：molecular
dimension of guar gum after gelout is significantly reduced under acidic condition，and the reduction of molecular dimension
plays more important role than acidic environment in decreasing damage；acid fluid is able to effectively remove damage caused
by fracturing fluid，increase core permeability，and form corrosion channels.

An Experimental Study on Influencing Factors of Dissolution Effect of#br# Barium Sulfate Scale

LI Hongjian1*, SUN Jianbo1，2, LI Ran1, YU Xiaowei1, WANG Deyu3

2016, 38(3):  156-161.  DOI: 10.11885/j.issn.1674-5086.2014.12.03.01

Asbtract ( 211 )   HTML   PDF (507KB) ( 761 )  

References | Related Articles | Metrics

To study the influence factors of the dissolving effect of scale dissolving solvent DEED，we conducted weight loss
method experiments on the effects of solvent concentration，temperature，time and pH value on scale dissolving. First，we
analyzed the scale-dissolving mechanism of DEED via chemical methods through which the main functional groups of DEED
that can chelate Ba2+ are found. As a result，the reason behind different scale dissolving effects under various conditions can
be explained more accurately and reasonably. Then，a number of experiments were conducted to study the influence factors
of scale dissolving effect of the agent. Under the experimental conditions，when the concentration of scale-dissolving agent is
9%，the highest dissolving rate of 82.41% would be attained. The scale dissolving time and temperature have a great impact
on scale dissolution. With the increase of acting time，scale dissolving rate gradually increases，and the scale dissolving rate
increases greatly during first the 24 hours，which satisfies the requirement of field application. With a 24-hour dissolving time，
dissolving rate increases from 32.02% to 82.88% as temperature increases from 25 ?C to 85 ?C. On the other hand，the pH
value has a significant influence on the dose of carboxyl ionization and chelating performance of scale dissolving agent，thus
affecting scale dissolving effect of the agent. With a 24-hour dissolving time，dissolving rate increases from 8.37% to 81.26%
as pH value increases from 6 to 12. Thus alkaline pre-flush injection is recommended in oil field operation.

The Pass-through Capacity Analysis for Multi-layer Injection Strings in#br# Directional Wells

FENG Ding*, SHI Lei, Xia Chengyu, ZHANG Hong, TU Yiliu

2016, 38(3):  162-169.  DOI: 10.11885/j.issn.1674-5086.2014.03.24.01

Asbtract ( 196 )   HTML   PDF (481KB) ( 736 )  

References | Related Articles | Metrics

With the increase of water injection layers in directional wells，the pass-through capacity analysis of injection strings
becomes necessary. The pass-through capacity has great influence on the implement of multi-layer injection process，and on
the safety of oil wells and malfunction prevention of the strings. The strings consist of at least 5 packers and distributors. After
a comparison of the axial force with the friction of the injection string in maximum curvature section in the three-dimensional
coordinate system，a new approach which can be used to analyze the pass-through capacity of injection string is given. In
consideration of the factors such as borehole trajectory，curvature，borehole diameter，stratigraphic friction，casing diameter，
and the relationship between the injection string friction and pass-through capacity，a model of dynamic load and stress profile
has been established by using the mechanics and displacement method，combined with energy and kinetic analysis. The model
can be used to analyze the process of running and pulling Multi-packer injection string in directional wells or horizontal wells.
A case study is made to verify the pass-through capacity and safety of Multi-packer injection string which proved a good field
guidance.

Tool Path Simulation of Envelope Milling of Complex Helical Surface

KUANG Yuchun1*, WU Longmei2, TU Junwen3, WU Yingqiang4, DONG Zongzheng1

2016, 38(3):  170-177.  DOI: 10.11885/j.issn.1674-5086.2014.01.03.01

Asbtract ( 296 )   HTML   PDF (856KB) ( 954 )  

References | Related Articles | Metrics

In order to reduce the machining error of complex helical surface，this paper studied the algorithm about tool path of
envelope milling by transforming the dynamic meshing relationship into the space geometry problems between milling- cutter
and workpiece through time discretization and spatial discretization in machining process based on numerical simulation method.
We build three-dimensional model of milling-cutter and workpiece surface of revolution，deduce the coordinate-transformation
matrix of meshing relationship between milling-cutter and workpiece，simplify the minimal directed distance between millingcutter
and workpiece into a two-dimensional problem，set up the simulation algorithm of tool-path of milling-cutter and finally
get the parameter information of NC codes. The machining process programmed on the obtained parameters proved to be able
to produce the helical surface with required precision. Error distribution of the profile and its influencing factors are studied
too.

Hydration Experiment of Hard Brittle Shale of the Longmaxi Formation

LIU Xiangjun1，2*, XIONG Jian2, LIANG Lixi1

2016, 38(3):  178-186.  DOI: 10.11885/j.issn.1674-5086.2014.04.10.05

Asbtract ( 425 )   HTML   PDF (845KB) ( 1188 )  

References | Related Articles | Metrics

The hydration of hard brittle shale has an important influence on the borehole stability. Therefore，the hydration
experiments was done for different types of shale from the Longmaxi formation in the south region of Sichuan Basin，observations
were made to mineral composition，microstructure，hydration swelling stress，water absorption by self-priming and core
immersion. And based on observations，the paper discusses the hard brittle shale hydration process and hydration mechanism.
The result shows that the main clay mineral of shale is illite，the shape of the clay mineral particles is flake and directional
alignment. There are lots of bedding and micro-crack in the shale，which provide the operation-space and flow channel for
the hydration of shale. The hydration swelling stress and water absorption by self-priming of shale tend to ascent first before
becoming stable. The fabric of the shale has an important influence on the ascend velocity or extent. The fractures in the
surface of sample are parallel plane of bedding in the process of immersion. With the increase of immersion time，the sample
would keep its integrality or spall to pieces. The fabric and cementation type of the shale have an important influence on the
hydration swelling. The hydration of the shale is a result of coupling of physical-chemical action and mechanical action，the
former decreasing the rock fracture toughness，and the later increasing the stress intensity factor for mode-I fracture. When the
stress intensity factor is greater than the rock fracture toughness，the crack will extend or broaden.