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Leak-Off Mechanism and Pressure Prediction for Shallow Sediments in Deepwater Drilling

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Journal of Ocean University of China 2018年第1期17卷 65-71页

作者： TAN Qiang deng jingen SUN Jin LIU Wei YU Baohua State Key Laboratory of Petroleum Resources and Prospecting ChinaUniversity of Petroleum-Beijing Key Laboratory of Marine Georesources and Prospecting (Hainan Province) Institute of Deep-Sea Science and Engineering Chinese Academy of Science

Deepwater sediments are prone to loss circulation in drilling due to a low overburden gradient. How to predict the magnitude of leak-off pressure more accurately is an important issue in the protection of drilling safety and the reduction of drilling cost in deep water. Starting from the mechanical properties of a shallow formation and based on the basic theory of rock-soil mechanics, the stress distribution around a borehole was analyzed. It was found that the rock or soil on a borehole is in the plastic yield state before the effective tensile stress is generated, and the effective tangential and vertical stresses increase as the drilling fluid density increases; thus, tensile failure will not occur on the borehole wall. Based on the results of stress calculation, two mechanisms and leak-off pressure prediction models for shallow sediments in deepwater drilling were put forward, and the calculated values of these models were compared with the measured value of shallow leak-off pressure in actual drilling. The results show that the MHPS(minimum horizontal principle stress) model and the FIF(fracturing in formation) model can predict the lower and upper limits of leak-off pressure. The PLC(permeable lost circulation) model can comprehensively analyze the factors influencing permeable leakage and provide a theoretical basis for leak-off prevention and plugging in deepwater drilling.

关键词： deepwater drilling shallow sediments leak-off mechanism leak-off pressure

Resolution of the Chiral Drugs

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Chemical Research in Chinese Universities 2001年第Z1期17卷 218-219页

作者： deng jingen The Engineering Center of Research and Development for Chiral Technology Chengdu Institute of Organic Chemistry Chinese Academy of Sciences

Chiral drugs are generally not permitted to be used in racemic form so that unintended side effects and unnecessary environmental hazards are avoided. Moreover, homochiral molecules are required immediately to progress key toxicological and clinical studies in the drug discovery. One series of technologies which can rapidly supply homochiral compounds is the separation of racemates, and of those the technique of crystallization of diastereomers is extremely effective-principally because it is simple to operate and it affords both enantiomers. In classical resolution via diastereoisomeric salt formation, the resolved compounds are limited to a given racemic acid or base and the choice of a suitable resolving agent for a racemic target compound is achieved by time-consuming trial-and-error procedure.

关键词： environmental hazards drug discovery side effects used in

Fracture development during disposal of hazardous drilling cuttings by deep underground injection: A review

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第5期14卷 1652-1670页

作者： Shuai Zhang Yongcun Feng Bin Li jingen deng Tie Geng Jincai Zhang College of Petroleum Engineering China University of PetroleumBejing102249China State Key Laboratory of Petroleum Resources and and Prospecting China University of PetroleumBeijing102200China Oilflied Chemicals Division China Oilfield Services LimitedLangfang065201China Sinopec Tech Houston HoustonTXUSA

Drilling fluids with complicated compositions are becoming more common as the oil and gas industry develops. The production of hazardous cuttings is increasing, which not only stifles the oil and gas industry’s development but also poses a severe environmental threat. Deep underground re-injection is a cost-effective and efficient method for dealing with hazardous cuttings. Numerous experiments and numerical studies on cuttings re-injection have been conducted in the past thirty years. However, there is still a divergence of views on the fracture development in the process of cuttings re-injection. A comprehensive review of existing studies is necessary to help researchers advance this technology. This paper provides a review of the fundamental studies on fracture behaviors during the deep underground re-injection of drilling cuttings. The limitations of the existing studies are also discussed to inspire new research endeavors.

关键词： Hazardous drilling cuttings Cuttings disposal Cuttings re-injection Fracture development Multiple fractures

Borehole stability in naturally fractured rocks with drilling mud intrusion and associated fracture strength weakening:A coupled DFN-DEM approach

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1565-1581页

作者： Yaoran Wei Yongcun Feng Zhenlai Tan Tianyu Yang Xiaorong Li Zhiyue Dai jingen deng College of Petroleum Engineering China University of Petroleum (Beijing)Beijing102249China State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum (Beijing)Beijing102249China College of Safety and Ocean Engineering China University of PetroleumBeijing102249China

Borehole instability in naturally fractured rocks poses significant challenges to *** mud invades the surrounding formations through natural fractures under the difference between the wellbore pressure(P w)and pore pressure(P p)during drilling,which may cause wellbore ***,the weakening of fracture strength due to mud intrusion is not considered in most existing borehole stability analyses,which may yield significant errors and misleading *** addition,only limited factors were analyzed,and the fracture distribution was *** this paper,the impacts of mud intrusion and associated fracture strength weakening on borehole stability in fractured rocks under both isotropic and anisotropic stress states are investigated using a coupled DEM(distinct element method)and DFN(discrete fracture network)*** provides estimates of the effect of fracture strength weakening,wellbore pressure,in situ stresses,and sealing efficiency on borehole *** results show that mud intrusion and weakening of fracture strength can damage the *** is demonstrated by the large displacement around the borehole,shear displacement on natural fractures,and the generation of fracture at shear *** intrusion reduces the shear strength of the fracture surface and leads to shear failure,which explains that the increase in mud weight may worsen borehole stability during overbalanced drilling in fractured formations.A higher in situ stress anisotropy exerts a significant influence on the mechanism of shear failure distribution around the ***,the effect of sealing natural fractures on maintaining borehole stability is verified in this study,and the increase in sealing efficiency reduces the radial invasion distance of drilling *** study provides a directly quantitative prediction method of borehole instability in naturally fractured formations,which can consider the discrete fracture network,mud intrusion,and as

关键词： Borehole stability Naturally fractured rocks Weakening of fracture strength Discrete fracture network Distinct element method

Numerical Simulation of Mechanical Compaction of Deepwater Shallow Sediments

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Journal of Ocean University of China 2018年第1期17卷 53-64页

作者： SUN Jin WU Shiguo deng jingen LIN Hai ZHANG Hanyu WANG Jiliang GAO Jinwei Laboratory of Marine Geophysics&Geo-Resources Institute of Deep-Sea Science and EngineeringChinese Academy of SciencesSanya 572000China Qingdao National Laboratory for Marine Science and Technology Qingdao 266237China College of Earth Sciences University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing 102249China CNOOC China Limited Tianjin Branch Tianjin 300451China

To study the compaction law and overpressure evolution in deepwater shallow sediments, a large-strain compaction model that considers material nonlinearity and moving boundary is formulated. The model considers the dependence of permeability and material properties on void ratio. The modified Cam-Clay model is selected as the constitutive relations of the sediments, and the deactivation/reactivation method is used to capture the moving top surface during the deposition process. A one-dimensional model is used to study the compaction law of the shallow sediments. Results show that the settlement of the shallow sediments is large under their own weight during compaction. The void ratio decreases strictly with burial depth and decreases more quickly near the seafloor than in the deeper layers. The generation of abnormal pressure in the shallow flow sands is closely related to the compaction law of shallow sediments. The two main factors that affect the generation of overpressure in the sands are deposition rate and permeability of overlying clay sediments. Overpressure increases with an increase in deposition rate and a decrease in the permeability of the overlying clay sediment. Moreover, an upper limit for the overpressure exists. A two-dimensional model is used to study the differential compaction of the shallow sediments. The pore pressure will still increase due to the inflow of the pore fluid from the neighboring clay sediment even though the deposition process is interrupted.

关键词： mechanical compaction deepwater shallow sediments compaction law shallow water flow overpressure evolution

A parallel approach to direct resolution of albuterol

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Chinese Science Bulletin 2010年第25期55卷 2814-2816页

作者： ZHONG QingLin PENG XiaoHua WU TongFei FU FangMin CUI Xin ZHU Jin deng jingen National Engineering Research Center of Chiral Drugs and Key Laboratory of Asymmetric Synthesis & Chirotechnology of Sichuan Province Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu 610041 China

A library consisting of a series of O,O'-diaryzoyl-L-(-)-tartaric acids (2) was designed and synthesized. The substituent on the aromatic ring of 2 significantly affects the diastereomeric excess and efficiency of the resolution of racemic albuterol (1). Excel-lent resolving reagent 2a was selected for the resolution of rac-1 via the parallel approach. However,a family of three resolving reagents failed to improve the resolution efficiency of rac-1.

关键词：沙丁胺醇并行方式直接解选择试剂 Excel RAC 脂肪酸酒石酸

Simultaneously improving ROP and maintaining wellbore stability in shale gas well:A case study of Luzhou shale gas reservoirs

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Rock Mechanics Bulletin

Rock Mechanics Bulletin 2024年第3期3卷 91-103页

作者： Yaoran Wei Yongcun Feng Zhenlai Tan Tianyu Yang Shuang Yan Xiaorong Li jingen deng National Key Laboratory of Petroleum Resources and Engineering China University of PetroleumBeijing102249China College of Petroleum Engineering China University of PetroleumBeijing102249China College of Safety and Ocean Engineering China University of PetroleumBeijing102249China

The ROP(rate of penetration)within the horizontal section of shale gas wells in the Luzhou oil field is low,seriously delaying the exploration and development *** is proved that reducing mud density mitigates the bottom-hole differential pressure(ΔP)and increases the ROP during overbalanced ***,wellbore collapse may occur when wellbore pressure is excessively *** is urgent to ascertain the optimal equilibrium point between improving ROP and maintaining wellbore *** safe mud weight window and the lower limit of mud density in the horizontal section of the Luzhou block are predicted using the piecewise fitting method based on conventional logging ***,the accuracy of the collapse pressure prediction was verified using the distinct element method(DEM),and the effect of wellbore pressure,in-situ stress,rock cohesion,and natural fracture density on borehole collapse was ***,a fitting model ofΔP and ROP of the horizontal section in the Luzhou block is established to predict ROP promotion potential after mud density *** field application of this approach,demonstrated in 8 horizontal wells in the Luzhou block,effectively validates the efficiency of reducing mud density for ROP *** study provides a useful method for simultaneously improving ROP and maintaining wellbore stability and offers significant insights for petroleum engineers in the design of drilling parameters.

关键词： Shale gas reservoirs ROP improvement Wellbore stability ROP promotion potential DEM

Critical condition study of borehole stability during air drilling

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Petroleum Science 2009年第2期6卷 158-165页

作者： deng jingen Zou Linzhan Tan Qiang Yan Wei Gao Deli Zhang Hanlin Yan Xiuliang MOE Key Laboratory of Petroleum Engineering China University of Petroleum Beijing 102249 China Drilling Research Institute of Changqing Oilfield Xi＇an Shaanxi 710048 China Drilling Research Institute of Shengli Oilfield Dongying Shandong 257100 China

The purpose of this paper is to establish the existence of the critical condition of borehole stability during air drilling. Rock Failure Process Analysis Code 20 was used to set up a damage model of the borehole excavated in strain-softening rock. Damage evolution around the borehole was studied by tracking acoustic emission. The study indicates that excavation damaged zone （EDZ） is formed around borehole because of stress concentration after the borehole is excavated. There is a critical condition for borehole stability; the borehole will collapse when the critical damage condition is reached. The critical condition of underground excavation exists not only in elastic and ideal plastic material but in strainsoftening material as well. The research is helpful to developing an evaluation method of borehole stability during air drilling.

关键词： Borehole stability air drilling critical condition

岩石变形及破坏过程中渗透率变化规律的实验研究

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岩石力学与工程学报 2000年第Z1期19卷 885-888页

作者：张守良沈琛邓金根中国石油天然气集团公司北京100724 胜利油田东营257000 石油大学北京102249

为流体所饱和的储层岩石或油砂受上覆压力 ,构造应力及流体压力的作用 ,钻井、完井、试井及油藏开采过程中 ,原有的应力状态受到扰动 ,在井眼或炮孔周围产生应力集中 ,岩石或油砂骨架有效应力随流体压力的衰竭而不断增大。通过不同应力... 详细信息

为流体所饱和的储层岩石或油砂受上覆压力 ,构造应力及流体压力的作用 ,钻井、完井、试井及油藏开采过程中 ,原有的应力状态受到扰动 ,在井眼或炮孔周围产生应力集中 ,岩石或油砂骨架有效应力随流体压力的衰竭而不断增大。通过不同应力状态下岩芯渗透率变化规律同步测试 ,分析了岩石渗透性与其应力状态及其力学参数间的相关关系 ,据此建立了渗透率与应力状态相关关系模型。为钻井及试采过程中防止储层损害的合理压差的确定提供了重要的科学依据。

关键词：渗透率,应力状态,相关式