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Productivity enhancement in multilayered coalbed methane reservoirs by radial borehole fracturing

petroleum Science 2022年第6期19卷 2844-2866页

作者： Rui-Yue Yang Gen-Sheng Li Xiao-Zhou Qin Zhong-Wei Huang Jing-Bin Li Mao Sheng Bin Wang State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing102249China

Coalbed methane(CBM)is an important unconventional natural *** of multilayered CBM reservoir is still facing the challenge of low production *** borehole fracturing,which integrates radial jet drilling and hydraulic fracturing,is expected to create complex fracture networks in multilayers and enhance CBM *** main purpose of this paper is to investigate the mechanisms and efficacy of radial borehole fracturing in increasing CBM production in multiple ***,a two-phase flow and multi-scale 3 D fracture network including radial laterals,hydraulic fractures and face/butt cleats model is established,and embedded discrete fracture model(EDFM)is applied to handle the complex fracture ***,effects of natural-fracture nonuniform distribution are investigated to show the advantages of targeted stimulation for radial borehole ***,two field CBM wells located in eastern Yunnan-western Guizhou,China were presented to illuminate the stimulation efficiency by radial borehole *** results indicated that compared with vertical well fracturing,radial borehole fracturing can achieve higher gas/water daily production rate and cumulative gas/water production,approximately 2 times *** communications to cleats and sweet spots and flexibility in designing radial borehole parameters in different layers so as to increase fracture-network complexity and connectivity are the major reasons for production enhancement of radial borehole ***,the integration of geology-engineering is vital for the decision of radial borehole fracturing designing *** key findings of this paper could provide useful insights towards understanding the capability of radial borehole fracturing in developing CBM and coal-measure gas in multiple-thin layers.

关键词： Coalbed methane Multilayered coal beds Radial borehole fracturing Complex fracture networks Cleats distribution

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Petrology and geochemistry of the Carboniferous cutinite-rich coals from the Hequ area of Shanxi Province, China

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Science China Earth Sciences 2022年第10期65卷 2018-2032页

作者： Daofu SONG Tieguan WANG Ping LI Jiadong YAN Xiangji ZHENG State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing 102249China

Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich *** petrology and geochemistry of the samples were analyzed using microscopic examination, proximate and ultimate analysis,rock pyrolysis, and gas chromatography-mass spectrometry(GC-MS). The cutinites in Haochuan(HC) coals are predominantly of the thin-walled type, whereas those in the Jingzigou(JZG) coals are predominantly thick-walled. The variable thickness of cutinites in different coals is related to the environment in which the coal-forming plants grew. Compared with typical Ⅲ kerogens, HC and JZG bituminous coals are characterized by high volatile matter yields and hydrogen contents due to the elevated hydrogen-rich cutinite content. Pyrolysis data indicate that these cutinite-rich coals can be expected to generate commercial liquid and gaseous hydrocarbons. Pristane(Pr) and phytane(Ph) are both abundant in the samples, with the Pr/Ph ratios for both the HC and JZG coals being >3.0, indicating moderate maturity and oxic peat depositional conditions. The C>>C>Cnormalized relative abundance of regular steranes is consistent with a dominant contribution from higher *** hopanes in the coals also suggest a substantial organic matter input from bacteria, which are common inhabitants of peat and coal. Palynology studies indicate that pteridophytes are likely to be the most common coal-forming plants. A gymnosperm contribution is also indicated by the presence of tetracyclic diterpenes. Massive accumulations of cuticles as cutinite in coal are rare and account for only a small proportion of coals worldwide. However, cutinite-rich coals are found in the northern margin of the North China Craton, in the Taiyuan Formation. The accumulation of cutinite in this area is the result of distinctive peat deposition conditions. Frequent marine transgression was an important contributing factor.

关键词： Cutinite-rich coal Carboniferous Coal petrology Geochemistry Hequ area

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Expulsive force in the development of C02 sequestration:application of SC-C02 jet in oil and gas extraction

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Frontiers in Energy 2019年第1期13卷 1-8页

作者： Haizhu WANG Gensheng LI Zhonghou SHEN State key laboratory of petroleum resources and Engineering China University of PetroleumBeijing 102200China

With the rapid development of global economy,an increasing amount of attention has been paid to the emission of greenhouse gases,especially *** recent years,dominated by the governments around the world,several significant projects of CO2 sequestration have been ***,due to the huge investment and poor economic effects,the sustainability of those projects is not *** CO2(SC-CO2)has prominent advantages in well drilling,fracturing,displacement,storage,plug and scale removal within tubing and casing,which could bring considerable economic benefits along with CO2 *** this paper,based on physicochemical properties of SC-CO2 fluid,a detailed analysis of technical advantages of SC-CO2 applied in oil and gas development is ***,the implementation processes of SC-CO2 are also *** the first time,a recycling process is presented in which oil and gas are extracted and the CO2 generated could be restored underground,thus an integrated technology system is *** the recent interests in the development of enhancing hydrocarbon recoveries and CO2 sequestration,this approach provides a promising techni?que that can achieve these two goals simultaneously.

关键词： CO2 sequestration SC-CO2 jet well drilling fracturing oil and gas

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Petrology and organic geochemistry of the Baishaping and Damaidi Devonian cutinitic liptobioliths,west of the Kangdian Uplift,China

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petroleum Science 2022年第5期19卷 1978-1992页

作者： Dao-Fu Song Tie-Guan Wang Ping Li Mai Zhang An-Liang Liu Jia-Dong Yan State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing 102249China

Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land *** Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,and unusually high cutinite content(>50%),belonging to typical cutinitic *** are bituminous coals and have a suppressed vitrinite *** with typical typeⅢkerogen,these liptobioliths are characterized by extremely high yields of volatile matter and high hydrogen contents owing to their enhanced cutinite *** indicated by pyrolysis and elemental analysis results,the Devonian cutinitic liptobioliths are dominated by typeⅠ-Ⅱkerogens and have an excellent potential to generate liquid *** Baishaping cutinitic liptobioliths are mainly composed of ribbon-like thick-walled cutinites,with small amounts of thin-walled *** is only present in trace amounts and is dominated by ***,the Damaidi Devonian coals are primarily composed of ribbon-like thin-walled cutinites,followed by collotelinites which are usually sandwiched by *** different petrological characteristics of the Baishaping and Damaidi liptobioliths might indicate a structural variation in the coal-forming plant cuticles and two distinct coal-forming *** molecular bio markers in the Devonian coals are mainly composed of C_(18)-C_(20)tetracyclic diterpenoids,which are assumed to be the dominant soluble constituent of the Devonian land-plant cuticles and might have played an important role in early land plant *** molecules include aromatic tetracyclic diterpenoids,3-5 ring polycyclic aromatic hydrocarbons and their methylated counterparts,and C_(16)-and C_(18)-monocarboxylic acids.n-Alkanes are present only in small *** molecular composition of the cutinite-rich coals is unexpected,because cuticular waxes are one of the most important sources of *** general,the petrology and geochemistry

关键词： Coal chemistry Macerals Hydrocarbon potential Plant cuticles Tetracyclic diterpenoids

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Analytical method for evaluating stress field in casing-cement-formation system of oil/gas wells

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Applied Mathematics and Mechanics(English Edition) 2017年第9期38卷 1273-1294页

作者： Wei LIU Baohua YU Jingen DENG State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing 102249China

In this paper, we present an analytical method for evaluating the stress field within a casing-cement-formation system of oil/gas wells under anisotropic in-situ stresses in the rock formation and uniform pressure within the casing. The present method treats the in-situ stresses in the formation as initial stresses since the in-situ stresses have already developed in the formation before placement of cement and casing into the well. It is demonstrated that, via this treatment, the present method excludes additional displacements within the formation predicted by the existing method, and gives more reasonable stress results. An actual tight-oil well is analyzed using the present and existing analytical methods, as well as the finite element method. Good agreement between the analytical results and the finite element analysis （FEA） results is obtained, validating the present method. It is also evident that, compared with the present method, the existing method overestimates the compressive stress level within the casing and the cement. Finally, the effects of elastic properties of the formation, cement, and inner pressure of casing on stresses within the casing and cement are illustrated with a series of sensitivity analyses.

关键词： near wellbore region stress evaluation anisotropic in-situ stress initialstress

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Analysis of drilling difficulty of extended-reach wells based on drilling limit theory

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petroleum Science 2022年第3期19卷 1099-1109页

作者： Wen-Jun Huang De-Li Gao MOE key laboratory of petroleum Engineering China University of PetroleumBeijing102249China State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing102249China

With the continuous increase in vertical depths and horizontal displacements of directional wells,the difficulties of drilling operations continue to increase,and more accurate methods of drilling difficulty evaluation are *** this paper,a drilling difficulty evaluation method is built by combining drilling limit model and expert ***,the concept of drilling difficulty index is introduced,and the method to calculate drilling difficulty index is ***,the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is *** last,the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea,in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is *** results indicate that extended-reach drilling in the Liuhua oilfield is on the“normal”difficulty level on average,rotary drilling in 8_(1/2)-*** is the most difficult,and the main constraint conditions are excessive torque and high *** technology upgradation,the drilling difficulties are decreased,the development control radius increases from 6.6 to 11.4 km,and the maximum horizontalto-vertical ratio increases from 5.3 to ***,the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on“normal”difficulty ***,technology upgradation,especially drilling rig upgradation,is the most important development direction for extended-reach drilling in the South China Sea.

关键词： Extended-reach drilling South China Sea Drilling limit Drilling difficulty evaluation Drilling optimization design

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Prediction models of burst strength degradation for casing with considerations of both wear and corrosion

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petroleum Science 2024年第1期21卷 458-474页

作者： Jie-Li Wang Wen-Jun Huang De-Li Gao MOE key laboratory of petroleum Engineering China University of PetroleumBeijing102249China State key laboratory of petroleum resources and Prospecting China University of PetroleumBeijing102249China

Casing wear and casing corrosion are serious problems affecting casing integrity failure in deep and ultra-deep *** paper aims to predict the casing burst strength with considerations of both wear and ***,the crescent wear shape is simplified into three categories according to common mathematical ***,based on the mechano-electrochemical(M-E)interaction,the prediction model of corrosion depth is built with worn depth as the initial condition,and the prediction models of burst strength of the worn casing and corroded casing are ***,the accuracy of different prediction models is validated by numerical simulation,and the main influence factors on casing strength are *** last,the theoretical models are applied to an ultra-deep well in Northwest China,and the dangerous well sections caused by wear and corrosion are predicted,and the corrosion rate threshold to ensure the safety of casing is *** results show that the existence of wear defects results in a stress concentration and enhanced M-E interaction on corrosion depth *** accuracy of different mathematical models is different:the slot ring model is most accurate for predicting corrosion depth,and the eccentric model is most accurate for predicting the burst strength of corroded *** burst strength of the casing will be overestimated by more than one-third if the M-E interaction is neglected,so the coupling effect of wear and corrosion should be sufficiently considered in casing integrity evaluation.

关键词： Deep well Casing integrity Casing wear Casing corrosion Burst strength

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Study of deep transportation and plugging performance of deformable gel particles in porous media

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petroleum Science 2024年第2期21卷 962-973页

作者： Wen-Jing Zhao Jing Wang Zhong-Yang Qi Hui-Qing Liu National key laboratory of petroleum resources and Engineering China University of PetroleumBeijing102249China MOE key laboratory of petroleum Engineering China University of PetroleumBeijing102249China

Deformable gel particles(DGPs) possess the capability of deep profile control and flooding. However, the deep migration behavior and plugging mechanism along their path remain unclear. Breakage, an inevitable phenomenon during particle migration, significantly impacts the deep plugging effect. Due to the complexity of the process, few studies have been conducted on this subject. In this paper, we conducted DGP flow experiments using a physical model of a multi-point sandpack under various injection rates and particle sizes. Particle size and concentration tests were performed at each measurement point to investigate the transportation behavior of particles in the deep part of the reservoir. The residual resistance coefficient and concentration changes along the porous media were combined to analyze the plugging performance of DGPs. Furthermore, the particle breakage along their path was revealed by analyzing the changes in particle size along the way. A mathematical model of breakage and concentration changes along the path was established. The results showed that the passage after breakage is a significant migration behavior of particles in porous media. The particles were reduced to less than half of their initial size at the front of the porous media. Breakage is an essential reason for the continuous decreases in particle concentration, size, and residual resistance coefficient. However, the particles can remain in porous media after breakage and play a significant role in deep plugging. Higher injection rates or larger particle sizes resulted in faster breakage along the injection direction, higher degrees of breakage, and faster decreases in residual resistance coefficient along the path. These conditions also led to a weaker deep plugging ability. Smaller particles were more evenly retained along the path, but more particles flowed out of the porous media, resulting in a poor deep plugging effect. The particle size is a function of particle size before inject

关键词： Physical simulation Deformable gel particle Breakage Particle size Residual resistance coefficient

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Experimental study of the azimuthal performance of 3D acoustic transmitter stations

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petroleum Science 2016年第1期13卷 52-63页

作者： Xiao-Hua Che Wen-Xiao Qiao Xiao-Dong Ju Jun-Qiang Lu Jin-Ping Wu Ming Cai State key laboratory of petroleum resources and Prospecting China University of Petroleum key laboratory of Earth Prospecting and Information Technology China University of Petroleum

Better well logging techniques for geologic investigations are urgently needed to identify and evaluate complex *** describe a new type of 3D transmitter station with corresponding circuits and *** can be used in a promising new technique of acoustic reflection well logging,that features better azimuthal detection capabilities,as well as better investigation *** transmitter stations consist of three-level subarrays that can radiate acoustic energy in any required azimuth of 3D space by circularly exciting various combinations at different *** tested the 3D acoustic transmitter stations and obtained laboratory directivity measurements with the3 D acoustic transmitter stations for the first *** results show that the 3-d B beam width in the horizontal plane ranges from 59° to 67° as a result of phase-delayed *** main beam is steered in the vertical plane at a deflection angle that ranges from 0° to 16° when the delay time of the excitation pulse between each pair of adjacent arc arrays is gradually *** 3-d B beam width is equal to 11°,whereas the deflection angle in the vertical plane is equal to 14°.Each of the four third-level subarrays in the same circumferential direction display consistent horizontal and vertical directivities,thus satisfying the requirements of azimuthal acoustic reflection logging.

关键词： transmitter deflection logging urgently geologic satisfying azimuth exciting excitation formations

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Determination of the shedding frequency of cavitation cloud in a submerged cavitation jet based on high-speed photography images

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Journal of Hydrodynamics 2021年第1期33卷 127-139页

作者： Chi Peng Shou-ceng Tian Gen-sheng Li State key laboratory of petroleum resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China

To accurately determine the shedding frequency of the cavitation cloud in a submerged cavitation jet,the spectral analysis and the proper orthogonal decomposition(POD)for high-speed photography images are *** spectrums of 6 different kinds of image signals(the area-averaged gray level,the line-averaged gray level,the point gray level,the cavitation length,width,and area)are calculated and *** line-averaged gray level is found to be optimal in determining the shedding frequency but an accurate frequency can only be obtained in the stable-frequency zone where the cavitation cloud *** repeated experiments,the plateau-shape distribution of the main frequency is established with a deviation of 10.8%.A revised Reynolds number Re'is defined and the shedding frequency can be correlated to Re'by a power law when the cavitation number is less than *** relationship is validated by the experimental data in *** first mode of the POD characterizes the ensemble-average of the cavitation cloud while the second mode is the major part of the cavitation cloud transient *** modes 2-5 are organized in pairs,which confirms the periodic feature of the cavitation cloud in the submerged cavitation *** the nozzle exit,the modes 2-5 are symmetrically distributed in the jet shear *** shedding frequency of the cloud cavitation can also be precisely determined by performing the spectral analysis of the weighting coefficients of the mode *** paper shows that the two parameters,namely,the line-averaged gray level and the weighting coefficients of the mode 2,can be confidently used to calculate the shedding frequency of the cavitation cloud in a submerged cavitation jet.

关键词： Cavitation jet shedding frequency high-speed photography spectral analysis proper orthogonal decomposition(POD)

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