Table of Content

01 February 2017, Volume 39 Issue 1

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The Surface Features of the Quartz Sand Grains in Zhuhai Formation of Baiyun Deep-water Area, the Pearl River Mouth Basin

XING Zuochang, LIN Changsong, QIN Chenggang, ZHANG Zhongtao, WANG Siqi

2017, 39(1):  1-11.  DOI: 10.11885/j.issn.1674-5086.2015.09.04.03

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Due to the hardness and chemical stability of quartz grains, their surfaces contain numerous microtextures that are formed during transport and deposition by various geological forces. These microtextures can provide evidence for interpreting sedimentary environments and transport mechanisms. The causes of sedimentary quartz grain surface microtextures in the Zhuhai Formation, Baiyun deep-water area, can be divided into three categories, mechanical, chemical, and mechanicalchemical, with 26 subclasses. The most dominant characteristics are subangular shape, V-shaped percussion cracks, straight/curved grooves and scratches, upturned plates, and abrasion fatigue. Sedimentary deposition in the late-Zhuhai Formation in the study area is characterized by medium transport distance, high-energy hydrodynamics(upper flow regime), and saltation. Although the specific sedimentary environment significance of the microfeatures remains to be addressed, this study provides new ideas and evidence for understanding sedimentary processes.

Reservoir Quality Evaluation of Carbonates in the Zhujiang Formation of the Early Miocene Pearl River Mouth Basin

LAN Yefang, HUANG Sijing, ZHOU Xiaokang, MA Yongkun

2017, 39(1):  12-24.  DOI: 10.11885/j.issn.1674-5086.2015.02.07.01

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Core observation, thin section identification, and physical property analysis show that the carbonate reservoir quality of the Lufeng, Huizhou, and Liuhua areas in the Pearl River Mouth Basin is significantly different. The carbonate reservoir quality of the Huizhou area is the lowest of the three areas because of extensive cementation; the reservoir has a visual porosity and an average permeability below 1 mD. Extensive dissolution, including early meteoric and burial dissolution, generates a great amount of secondary porosity, such as intergranular pores, mold pores, alter-large pores and geode pores, in the Liuhua area, which contributes to more than 80% of the whole thin section porosity. The carbonates of this area have the highest porosity and permeability, high porosity and permeability correlation coefficient, and low cutoff porosity. Therefore, the best carbonate reservoir was developed in the Liuhua area. Early cementation is very helpful for the preservation of the primary porosity in the Lufeng area, where the dissolution is much weaker than in the Liuhua area, which makes the porosity in the Lufeng area approximately equal to that of the Liuhua area. However, its permeability is much lower than that of the Liuhua area due to the low connectivity of the primary porosity and the cutoff porosity is the highest. Thus, the Lufeng area is characterized by medium carbonate reservoir quality.

Sedimentary Characteristics and Factors Controlling the Shell Beach in the Da'anzhai Member of the Central Sichuan Basin

HOU Gangfu, NI Chao, CHEN Wei, GU Mingfeng, HAO Yi

2017, 39(1):  25-34.  DOI: 10.11885/j.issn.1674-5086.2015.03.31.04

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Core and microscope observations reveal that the three types of rocks in the Jurassic Da'anzhai Member of the Central Sichuan Basin, which include shell limestone, muddy shell limestone, and shaly shell limestone, are the sedimentary products of the shell beach in the shallow-semi-deep lake environment. We determined the following sedimentary microfacies on the shell beach based on logging and seismic facies studies: main beach, beach wing, and slope before beach. The distribution of the microfacies is controlled by the ancient landform. The main beach is distributed on the underwater paleo-uplift, the beach wing surrounds the uplift, and the slope is distributed in the transitional area between the underwater paleo-uplift and the depocenter. The evolution and migration of the shell beach is controlled by the lake level changes. When the lake level rises, the shell beach migrates from the low uplift of the depocenter to the periphery uplift of the basin. When the lake level declines, the shell beach migrates from the periphery uplift of the basin to the low uplift of the depocenter.

Fractal Characteristics of Fracture of Xujiahe Formation in Fault-fold Belt of Central Yuanba Area

FAN Cunhui, TAO Jiali, ZHOU Kun, HU Feng, HUANG Wei

2017, 39(1):  35-42.  DOI: 10.11885/j.issn.1674-5086.2016.03.08.02

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Fractures in the rock masses of the Xujiahe Formation in the fault-fold belt of the central Yuanba area of the Sichuan Basin are characterized by good self-similarity and fractal characteristics that are attributed to the tectonic stress field. Thus, this research is conducted with respect to the fractal characteristics of fault developments in the Xujiahe Formation, as well as factures in the rock core. The box-covering method was employed in this study to derive the fractal dimension values of faults and fractures. Further, using the fracture density in the core, mathematical formulae were adopted to fit the capacity dimensions of faults in each sub-area, as well as factures in the rock core, where the quantitative relation thereof was established. In this manner, the favorable fracture development zone of the Xujiahe Formation in the fault-fold belt of the central Yuanba area of the Sichuan Basin is obtained. The results show that the areas where the fractal dimension value of fractures in the Xujiahe Formation exceeds 1.45 belong to the fracture development zones, which are characterized by a high level of oil and gas enrichment and accumulation. The areas with fractal dimension values ranging from 0.95 to 1.45 are the relatively developed fracture zones, while areas with less than 0.95 are underdeveloped fracture zones.

Characteristics of CBM Reservoirs and Their Resource Potential in the Southern Sichuan Basin

JIANG Yuqiang, LUO Mingsheng, ZHANG Hu, WANG Yong, GAN Hui

2017, 39(1):  43-52.  DOI: 10.11885/j.issn.1674-5086.2015.10.06.15

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According to the results of several coalbed methane(CBM) resource evaluations, the coal in the southern Sichuan Basin is mainly anthracite, similar to that of the Qinshui Basin. The coal bed in the southern Sichuan Basin contains a large amount of CBM resources due to the high degree of coal metamorphism, strong adsorption capacity, and large gas content. The CBM reservoir characteristics in the southern Sichuan Basin, such as the coal layer distribution, coal rock quality, pore-fracture features, gas content, and isothermal adsorption features of the coal beds, were analyzed and the coal reservoir quality and CBM resource potential were evaluated in this study using logging and CBM parameter well data. The results show that the regional coal development is unstable because of an overall great burial depth and high degree of coal metamorphism. The coal reservoirs have a large Langmuir volume, high gas content, good gas quality, high gas saturation, small Langmuir pressure, and small critical desorption pressure. The comprehensive evaluation shows that the CBM reservoir has a good quality and great potential; however, its development is relatively difficult. Therefore, suitable mining technology is needed. We selected the Changning-Xuyong block as the experiment area for CBM exploration and development to determine CBM evaluation methods and effective mining technologies.

The Key Parameters and Reservoir-forming Characteristic of Tight Oil of Dodsland Field Viking Formation

ZHENG Min, WANG Wenguang, LI Peng, LI Jianzhong, WU Xiaozhi

2017, 39(1):  53-62.  DOI: 10.11885/j.issn.1674-5086.2015.10.22.03

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Tight oil is considered a realistically superior, unconventional oil and gas resource. However, systematic standards regarding various key parameters of tight oil such as estimated ultimate recovery (EUR), recoverable coefficient, and oil-gas resource abundance have not yet been effectively established in China. Standard values from mature tight oil calibration areas in other countries are often used as reference. This study conducts an in-depth analysis on a tight oil calibration area of the Viking Formation at Dodsland Field located in the Alberta Basin in western Canada in order to examine the oil-gas reservoir conditions and characteristics. The tight oil reserves and ultimate recovery of Viking Formation are evaluated using the Monte Carlo method and the EUR method, based on which the recoverable coefficient and oil-gas resource abundance are also determined. The results have shown that: 1) the tight oil reserves of the Viking Formation at Dodsland Field are 5.39×10⁸ t, of which the recoverable reserves are 0.79×10⁸ t; 2) according to the study results of the calibration area, the geological resource abundance is evaluated to be 37.799×104 t/km², of which the recoverable resource abundance is 5.565×104 t/km², and 3) the recoverable coefficient of the evaluation area is 14.7%. Based on the analysis of oil-gas geological characteristics of the tight reservoir at Viking Formation, a basic parameter system featuring tight oil-gas geological conditions can be constructed.

Facture Modeling Research of Tight Oil Reservoir Based on Fracture Propagation Inversion Model

TANG Mingming, ZHANG Jinliang

2017, 39(1):  63-72.  DOI: 10.11885/j.issn.1674-5086.2015.07.18.01

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Fracture modeling of tight oil reservoir has become the focus of reservoir modeling technology. Because existing fracture modeling methods are mostly ignored the essential relationship between the law of fracture propagation and the distribution of fracture characteristics, and therefore impossible to give an effective information of fracture distribution. In this paper, we proposed one new fracture modeling method called stochastic extended finite element method, which is build based on fracture mechanics and multi-field Kriging method. This method established the fracture propagation inversion model firstly, based on law of fracture propagation and extended finite element method, by using annealing simulation method. Then, by integrating the Kriging system and fracture simulation system and using structure and imaging logging data, we constructed an multi-field Kriging estimation model. Finally, based on the stochastic extended finite element simulation method, we wrote a fracture modeling system software, and build the fracture propagation model and fracture distribution model of Upper Cretaceous Qingshankou Formation in Daqingzijing area. Simulation results have shown that the fracture modeling method based on stochastic extended finite element simulation could overcome the difficult of existing fracture modeling method, and improve the characterization precision of fractured reservoir.

A Study on Acoustic Velocity and Resistivity of Rocks in CO₂/Natural Gas Accumulation

ZHOU Jiaxiong, HE Shenglin, CHEN Yijian, CAI Maojia, DU Xiangyong

2017, 39(1):  73-79.  DOI: 10.11885/j.issn.1674-5086.2015.06.06.25

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The complicated geological conditions of sea basins cause difficulties in natural gas exploration. The resistance and acoustic test of rocks of natural gas accumulation under high temperature and high pressure is essential for natural gas exploration and development. This study introduced a test of resistivity and acoustic properties of core samples that were displaced by various proportions of gas/CO₂ mixture at various saturations using an SCMS-E core multi-parameter instrument with various pressures and temperatures and a maximum temperature of 180℃ and a maximum pore pressure of 50 MPa. We also used the instrument to test the change in acoustic velocity of the dry samples that were filled with the gas/CO₂ mixture of various proportions. The experimental results showed that the saturation exponent of the saturated samples changed slightly when the content of CO₂ in the displacing mixture changed, but the cementation factor remained almost unchanged. The longitudinal acoustic velocity of the dry core samples filled with gas/CO₂ mixture decreased with increases in CO₂ content. The change in shear acoustic velocity variation was not obvious when the CO₂ content changed. The test results were consistent with the analysis results by the Gassmann equation and the Batzle empirical equation.

Numerical Simulation of the Decomposition of Natural Gas Hydrates by Depressurization

LIU Jianjun, SHAO Zuliang, ZHENG Yongxiang

2017, 39(1):  80-90.  DOI: 10.11885/j.issn.1674-5086.2016.06.09.01

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Natural gas hydrate decomposition is a complicated process involving heat and mass transfer and phase transitions. We established a three-dimensional mathematical model for the gas hydrate decomposition by depressurization taking factors such as heat conduction, heat convection, gas-liquid two-phase flow, and hydrate decomposition kinetics into consideration. The effects of the bottom hole pressure, initial hydrate saturation, and absolute permeability of the reservoir on the decomposition results were analyzed using numerical simulation. The results showed that the lower the bottom hole pressure is, the faster are the gas production rate and the reservoir temperature and pressure decrease. When the initial saturation of the gas hydrate is relatively large, the decomposition rate of the early stage is faster, but that of the later stage is slower. When it is too high, it will inhibit the decomposition of the gas hydrate. The absolute permeability has little impact on the gas production; however, when the permeability is too low, the production efficiency will be lower. Therefore, a combination of the depressurization method and other methods can be used.

Dynamic Propagation of Multiple Horizontal Fractures and Mutual Interference Between Induced Stresses

ZHENG Ran, LI Gensheng, ZHU Haiyan

2017, 39(1):  91-99.  DOI: 10.11885/j.issn.1674-5086.2016.09.19.02

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The X-6 Formation is located at a depth of 500-700 m in the QA Oilfield and has low porosity and low permeability. Natural high-angle fractures exist in the formation. These conditions partially satisfy the requirements for a fracture network after hydraulic fracturing but may result in relatively complex fracture patterns and introduce difficulties to the fracturing design and treatment. Firstly, triaxial tests were carried out in this work to study rock mechanical properties. A two-dimensional seepage-stress-damage-coupled finite element model of the sand- and mudstone-interlayered formation was then established. Lastly, the propagation of multiple hydraulic fractures and the stress interference mechanism of the X-6 reservoir were simulated and the influences of the pumping rate, in situ stress, and fracturing fluid viscosity on the stress interference were studied. The interference mechanism of the interaction of the hydraulic and natural fracture was revealed. We found that the reservoir has complex fracture mechanical and engineering geological conditions for complex fracture generation, providing theoretical guidance for the hydraulic fracturing of the region.

Effectiveness of Gas Injection in Fractured Vuggy Reservoirs Connected to Caves

ZHU Wenqing, CHANG Baohua, XIONG Wei, GAO Shusheng

2017, 39(1):  100-106.  DOI: 10.11885/j.issn.1674-5086.2015.05.19.03

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Oil flowing production or water injection replacement is mainly applied to carbonate reservoirs, which may result in a large quantity of oil remaining in the caverns. To solve the problem, we conducted research on the effects of gas injection in carbonate reservoirs. First, the fractured and vuggy reservoir communication cave model was simplified, and computational analysis of the adaptability of nitrogen, methane, and carbon dioxide was performed. Physical simulation was applied to flowing, water flooding, and gas injection experiments, and the gas injection development analysis method was developed. The results demonstrate that in such reservoirs, the gas displacement effect is poor with larger scale of bottom water and better physical properties of fractured and porous reservoirs. With an increase in the gas injection cycle, the fracture-cave elastic energy increases. Thus, in field production, we could carry out the gas injection operation in fracture caves, with poor physical properties in the upper fractured and porous reservoirs, and caves with smaller quantities of bottom water. Establishing linear equations of elastic production rate and compression coefficient can predict the gas volume, energy, and water cycle output parameters and provide a foundation for gas injection effect evaluation.

Features and Forecast of Water Output in Fractured Vuggy Carbonate Condensate Reservoir

KANG Bo, ZHANG Liehui, WANG Jian, FAN Kun, WANG Hong

2017, 39(1):  107-113.  DOI: 10.11885/j.issn.1674-5086.2015.07.24.01

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With increase in production, the number and water production rate of gas wells producing water in the carbonate gascondensate reservoir increases, which reduces the recovery ratio of condensate and natural oils, and impacts the overall effect of condensate gas reservoir development. This article, based on summarizing the features of the carbonate gas-condensate wells in terms of production and water production, makes an energy evaluation of the producing test wells through the flow material balance method, and studies forecast of the water output from producing test wells, with abundant supply of formation energy, according to the changing pattern of production gas-oil ratio and natural gas hydrocarbons. The results of the evaluation prove that the production gas-oil ratio reduces significantly before water output of the carbonatite gas-condensate well; the percentage of light natural gas hydrocarbon components reduces, while that of intermediate and heavy components increases.

Characteristics and Mechanism of Water Production for Fractured Vuggy Carbonate Reservoirs, Halahatang Oilfiel

MIN Huajun, CHEN Lixin, WANG Lianshan, ZHANG Lei, CHEN Jun

2017, 39(1):  114-123.  DOI: 10.11885/j.issn.1674-5086.2015.03.18.02

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Water breakthrough becomes common and it is difficult to solve this problem in fractured vuggy carbonate reservoirs, such as the one in Halahatang Oilfield. Based on well data characteristics, we conducted a study on the characteristics and formation mechanisms of water producing to solve the problem. Analysis shows that different water cut shapes represent different mechanisms that are related to characteristics of production intervals. Fluctuant water production includes sets of reservoirs, and water fluctuates in the non-main production layers in the form of pent-up water. Slow-rapid increase in water cuts form in relatively homogeneous producing intervals, because of the increase in output channels and relative permeability after the water coning breaks through. A sudden increase in water cut forms when producing intervals are seriously heterogenous, and the water breaks through via main production channels. According to the characteristics of reservoirs and water producing mechanisms, measures for water control are proposed, which prove to be effective and can be widely applied.

Pressure Variation Characteristics in Bead-shaped Fractured Vuggy Carbonate Gas Reservoirs

WANG Hai, LIN Ran, ZHANG Chenyang, HUANG Binguang, MIU Changsheng

2017, 39(1):  124-132.  DOI: 10.11885/j.issn.1674-5086.2015.03.05.05

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This paper establishes a mathematical model for gas flow through bead-shaped fractured vuggy carbonate gas reservoirs based on material balance and fracture flow equations. This model could calculate the pressure variation in each vug during the gas production stage. A series of numerical calculations were conducted on the mathematical model, and then a double logarithmic curve of the bottom hole pressure(BHP) and a semi-logarithmic curve of pressure derivative were plotted. According to the semi-logarithmic curve, pressure derivative curves of vugs initially increase and then decrease; meanwhile, the derivative curves of the nearest vug from the well increases and decreases most rapidly, and its turning point presents earlier than other vugs. The double logarithmic curve could be divided into four stages-wellbore storage effect reaction stage, fracture reaction stage, vug reaction stage, and boundary reaction stage. Finally, we studied the characteristics of the double logarithmic curve from a series of models with different number/volume/arrangement of vugs and different apertures/arrangements of fractures, and it was found that the characteristics of double logarithmic curves change with the different above-mentioned parameters.

Evaluation of EOR Effect of Gas Huff-n-puff in Fractured Vuggy Carbonate Reservoirs

SU Wei, HOU Jirui, LIU Juan, ZHU Daoyi, XI Yuanyuan

2017, 39(1):  133-139.  DOI: 10.11885/j.issn.1674-5086.2015.04.24.01

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Large water-eroded caves, solution pores, and fractures are the main spaces of fractured vuggy carbonate reservoirs with strong heterogeneity. The technology of gas huff-n-puff is an effective way to improve oil recovery in such reservoirs. In this study, an indoor physical simulation apparatus was designed and produced for carbonate reservoirs in order to explore the huff-n-puff effect of different gases. The huff-n-puff effect and its mechanism for four gases(CO₂, N₂, CO₂ injected before N₂, CO₂ injected after N₂) were analyzed considering the parameters of oil change rate, gas generation rate, and cumulative gas production. The experimental results show that the huff-n-puff mechanism of the four injected gases is obvious. The lowest oil change rate was 0.422(N₂ huff-n-puff). The mixed gas (CO₂ and N₂ mixture) huff-n-puff fully develops a synergistic effect. CO₂ dissolved in crude oil decreases oil viscosity, while N₂ occupies the high positions of caves and forms a gas cap due to gravitational differentiation. The huff-n-puff effect of the gaseous mixture of CO₂ and N₂ is better than that of a single gas, and CO₂ injection after N₂ huff-n-puff can achieve the best effect with an oil change rate of 0.861. Experimental research shows that gas huff-n-puff is an effective EOR, and the huff-n-puff effect of CO₂ injected after N₂ is more remarkable.

The Effects of Shale Interlayers on SAGD-Performance

TANG Shuai, WU Yongbin, LIU Pengcheng, ZHANG Jinchuan, LIU Yang

2017, 39(1):  140-147.  DOI: 10.11885/j.issn.1674-5086.2015.02.10.03

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SAGD performance is very sensitive to reservoir heterogeneity, and shale interlayers have a certain effect on a SAGD drainage channel with dual horizontal wells. Based on research of the Xinjiang Fengcheng oilfield, the multiple-factors numerical model characterizing a reservoir with interlayers between or above an injector-producer was established, and the SAGD performances were simulated under different interlayer distributions and horizontal and vertical locations to obtain the threshold parameters. In addition, the oil production profiles were used to detect geological architectures such as the size and the vertical location of shale barriers and act as a guide to enhance well deployment and avoid geological risk, thereby providing significant guidance for the realization of a SAGD-efficient development.

Well Cleaning Technology for Highly Deviated and Extended Reach Wells in Jidong Oilfield

XU Xiaofeng, SUN Ning, MENG Yingfeng, SONG Wei, WEI Na

2017, 39(1):  148-154.  DOI: 10.11885/j.issn.1674-5086.2015.08.04.03

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With progress in exploration and development of the Jidong oilfield, the number of highly deviated and extended reach wells is increasing year-after-year, thereby leading to the problem of well cleaning. In accordance with the characteristics of highly deviated and extended reach wells, we analyzed the causes of cutting bed and cutting transport laws, and optimized hydraulic parameters based on the hydraulic calculation mode. We simulated flow characteristics of the fluid around EHCDP by means of computational fluid dynamics(CFD), and evaluated drilling fluid materials to maintain drilling fluid properties. Taking real-time well cleaning monitoring and high efficiency drilling fluid materials into consideration, we improved the level of well cleaning from design to drilling. In addition, we formed a set of technical measures for improving flow condition of wellbores of highly deviated wells, which provides technical support for safe drilling. Application of improved technical measures to highly deviated wells shows that problems, such as bit freezing, caused by inadequate hole cleaning rarely occur during construction.

Flushing Fluid for Diesel-based Drilling Fluid Cleaning

GUO Xiaoyang, OU Hongjuan, LI Ming, GU Tao, LIU Honghua

2017, 39(1):  155-160.  DOI: 10.11885/j.issn.1674-5086.2015.06.27.02

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A diesel-based drilling fluid (DBDF) is wildly applied in complex deep wells. However, its strong adhesion to the casing and the well would severely affect the cementing quality. To solve this problem, a study on the preflush system FYJ was conducted: (1) established an optimized method of a surfactant; (2) optimized the efficient surfactants; (3) evaluated indexes referring to the fluid flushing efficiency, the properties of wetting reverse, and compatibility with drilling mud, and we obtained a flushing fluid FYJ having a good comprehensive property. The results showed that (1) Anionic/non-ionic or mixed surfactants with HLB values of 12-15 should be used in preflush systems, the minimum surface tension of the surfactant solution ((γ_min) should be close to or less than that of soaking surfaces of DBDF (γ_c≈23-27 mN/m), and the optimum addition amount of the surfactant should be greater than the critical micelle concentration (CMC value). (2) The preflush system FYJ can remove 82% of the DBDF attached to the well and casing walls, which have a strong temperature and salt resistance. (3) The preflush system FYJ provides good compatibility with DBDF and slurry, and it can effectively dilute the DBDF and slurry.

Collapse Risk for Deviated Borehole in Shale Formations Based on True-triaxial Strength Criterion

MA Tianshou, YANG Zixin, CHEN Ping, GUO Zhaoxue

2017, 39(1):  161-168.  DOI: 10.11885/j.issn.1674-5086.2015.07.10.24

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The Mohr-Coulomb(M-C)criterion is commonly used in the analysis of wellbore stability. Consequently, the result of wellbore stability analysis is conservative because the influence of intermediate principal stress(σ₂) is ignored. Therefore, in this study, the influence of σ₂ is considered to derive a true-triaxial Mogi-Coulomb(MG-C) criterion, and the applicability of the M-C, Drucker-Prager(D-P), and MG-C criteria were evaluated by fitting the true-triaxial data of the Yuubari shale. The relative collapse risk was analyzed for these three criteria based on the poro-elastic stress distribution model of the deviated well. The results show that the fitting result of MG-C is the best as it can accurately predict the influence of σ₂, and the rock strength increases at first and then decreases with increasing σ₂. The distribution rule of the relative collapse risk for deviated wellbore is basically the same for the above three criteria. The result of M-C is slightly higher, while that of D-P is slightly lower, and that of MG-C is optimal, which can accurately predict the impact of σ₂. Thus, MG-C criterion is applicable to the analysis of collapse pressure. Moreover, the material constants of the MG-C criterion can be determined by conventional triaxial rock mechanics parameters(cohesion and friction angle), which led to MG-C convenience to apply. The wellbore stability can get a continuous collapse pressure profile with logging data analysis.

Schematic Design of Erosion Test on Cementing Sliding Sleeves in Fracturing Operations

WANG Guorong, QIAN Quan, YANG Changhai, WEI Liao, GUO Zhaohui

2017, 39(1):  169-176.  DOI: 10.11885/j.issn.1674-5086.2015.07.01.23

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New downhole tool inventions should be used after severe tests because the accurate simulation of the actual working conditions is very important. This study explains a four-serial-parallel pump test model to simulate erosion with the creation of a large discharge and high sand content when cementing sliding sleeves were in the operating mode. First, the equipment connection scheme was hypothesized for a two-parallel pump model according to the field test conditions. Then, the equipment connection was designed so that the pump lift in the pipelines reached 35.82 m based on detailed theoretical calculation. With this figure and the H-Q characteristic curve of the actual measurement of one centrifugal pump, the equipment connection was set up as a four-serial-parallel pump model. The simulation results showed that the scheme met the erosion requirements for a large discharge (4.5 to 7.0 m³/min) and high sand content (volume ratio of 25%) and had a large allowance. Furthermore, the test showed that in all fracturing operations, different numbers of sliding sleeve eyelets influenced the overall pipeline pressure loss, test flow, and pump efficiency.

Emulsification Behavior and Electro-chemical Dehydration Method of Produced Liquid in High Concentration Polymer Flooding Wells

ZHANG Hongqi, LIU Yang, WANG Zhihua, XU Mengmeng

2017, 39(1):  177-184.  DOI: 10.11885/j.issn.1674-5086.2015.05.06.04

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Owing to the oil-water separation efficiency of produced liquid with high concentration polymer flooding and its impact on conventional AC-DC electric fields, the emulsification behavior and dehydration method of these types of emulsions were studied. Many evaluation methods were used for the gathering conditions, such as phase-inversion characteristics, electronegativity, distribution of emulsified oil-particle diameters, interface properties, micro-morphology of emulsions, and oil-water separation bottle tests. A dehydration experimental device with a pulsed power supply was established, and the adaptability of high concentration polymer flooding produced liquid was assessed. The results indicate that the emulsified behavior of produced liquid in high concentration polymer flooding wells was closely related to an increase in polymer concentration. Increasing the polymer concentration enhanced the electronegativity and decreased the phase inversion points of emulsions to different degrees. Furthermore, difficulties of coalescence and phase separation increased because the high polymer concentration promoted the formation of a viscoelastic interfacial film. The oil-water separation effect can be improved in the dehydration process of a pulse power supply electric field with demulsifiers, and the dehydration operational stability can be perfected.