Offshore deepwater cementing generally faces more challenges than onshore cementing.Shallow formations in deepwater wells often exhibit low structural strength,high porosity,and are prone to shallow gas influx and hyd...Offshore deepwater cementing generally faces more challenges than onshore cementing.Shallow formations in deepwater wells often exhibit low structural strength,high porosity,and are prone to shallow gas influx and hydrate formation.These factors require careful control of hydration heat.In this article,we examine the key factors influencing temperature fluctuations in the wellbore and develop a temperature model that accounts for the thermal effects related to cement slurry circulation and hydration.This model is then applied to a deepwater shallow formation cementing case study.The results show that:(1)When cement slurry is displaced into deep-water shallow formations,it loses heat due to seawater-induced cooling before entering the wellbore.This lowers the temperature of both the slurry and the wellbore before cement hydration begins.(2)The main production of heat due to cement hydration occurs during the pre-induction and acceleration stages.These are also the critical phases that affect formation temperature in deep-water shallow formation cementing.According to Kutasov’s semi-analytical equation,the peak heat release happens 8–12 h after cementing,resulting in a temperature rise of up to 40℃ and 30℃ for 26″and 12-1/4″boreholes,respectively.展开更多
Aiming at the shallow depth seam proximity beneath a room mining goaf, due to that the shallow depth seam is exploited using the longwall mining and overlain by thin bedrock and thick loose sands, many accidents are l...Aiming at the shallow depth seam proximity beneath a room mining goaf, due to that the shallow depth seam is exploited using the longwall mining and overlain by thin bedrock and thick loose sands, many accidents are likely to occur, including roof structure instability, roof step subsidence, damages of shield supports, and the face bumps triggered by the large area roof weighting, resulting in serious threats to the safety of underground miners and equipment. This paper analyses the overlying strata movement rules for the shallow seams using the physical simulation, the 3DEC numerical simulation and the field mea- surements. The results show that, in shallow seam mining, the overburden movement forms caved zone and fractured zone, the cracks develop continuously and reach the surface with the face advancing, and the development of surface cracks generally goes through four stages. With the application of loose blast- ing of residual pillars, reasonable mining height, and roof support and management, the safe, efficient and high recovery rate mining has been achieved in the shallow depth seam proximity beneath a room min ing goal.展开更多
Based on a shallow roadway with weakly cemented soft strata in western China, this paper studies the range and degree of plastic zones in soft strata roadways with weak cementation. Geological radars were used to moni...Based on a shallow roadway with weakly cemented soft strata in western China, this paper studies the range and degree of plastic zones in soft strata roadways with weak cementation. Geological radars were used to monitor the loose range and level of surrounding rocks. A mechanical model of weakly cemented roadway was established, including granular material based on the measured results. The model was then used to determine the plastic zone radium. The predicted results agree well with measured results which provide valuable theoretical references for the analysis of surrounding rock stability and support reinforcing design of weakly cemented roadways. Finally, a combined supporting scheme of whole section bolting and grouting was proposed based on the original supporting scheme. It is proved that this support plan can effectively control the deformation and plastic zone expansion of the roadway surrounding rock and thus ensure the long-term stable and safe mining.展开更多
The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed under...The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.展开更多
基金the financial support from Science and Technology Projects in Guangzhou(Grant number:No.2023A04J0306)supported by China Geological Survey(Grant number:No.DD20230066)High-Tech Ship Research Project of Ministry of Industry and Information(Grant number:CJ05N20).
文摘Offshore deepwater cementing generally faces more challenges than onshore cementing.Shallow formations in deepwater wells often exhibit low structural strength,high porosity,and are prone to shallow gas influx and hydrate formation.These factors require careful control of hydration heat.In this article,we examine the key factors influencing temperature fluctuations in the wellbore and develop a temperature model that accounts for the thermal effects related to cement slurry circulation and hydration.This model is then applied to a deepwater shallow formation cementing case study.The results show that:(1)When cement slurry is displaced into deep-water shallow formations,it loses heat due to seawater-induced cooling before entering the wellbore.This lowers the temperature of both the slurry and the wellbore before cement hydration begins.(2)The main production of heat due to cement hydration occurs during the pre-induction and acceleration stages.These are also the critical phases that affect formation temperature in deep-water shallow formation cementing.According to Kutasov’s semi-analytical equation,the peak heat release happens 8–12 h after cementing,resulting in a temperature rise of up to 40℃ and 30℃ for 26″and 12-1/4″boreholes,respectively.
基金provided by the National Natural Science Foundation of China (No. 51304202)the Natural Science Foundation of Jiangsu Province of China (No. BK20130190)+1 种基金the Fundamental Research Funds for the Central Universities (No. 2013QNA28)the Priority Academic Program Development of Jiangsu Higher Education Institutions (No. SZBF2011-6-B35)
文摘Aiming at the shallow depth seam proximity beneath a room mining goaf, due to that the shallow depth seam is exploited using the longwall mining and overlain by thin bedrock and thick loose sands, many accidents are likely to occur, including roof structure instability, roof step subsidence, damages of shield supports, and the face bumps triggered by the large area roof weighting, resulting in serious threats to the safety of underground miners and equipment. This paper analyses the overlying strata movement rules for the shallow seams using the physical simulation, the 3DEC numerical simulation and the field mea- surements. The results show that, in shallow seam mining, the overburden movement forms caved zone and fractured zone, the cracks develop continuously and reach the surface with the face advancing, and the development of surface cracks generally goes through four stages. With the application of loose blast- ing of residual pillars, reasonable mining height, and roof support and management, the safe, efficient and high recovery rate mining has been achieved in the shallow depth seam proximity beneath a room min ing goal.
基金provided by the National 973 Programs(No.2014CB046905)the National Natural Science Foundation of China(Nos.51274191 and 51404245)+1 种基金the Doctoral Fund of Ministry of Education(No.20130095110018)China Postdoctoral Science Foundation(No.2014M551699)
文摘Based on a shallow roadway with weakly cemented soft strata in western China, this paper studies the range and degree of plastic zones in soft strata roadways with weak cementation. Geological radars were used to monitor the loose range and level of surrounding rocks. A mechanical model of weakly cemented roadway was established, including granular material based on the measured results. The model was then used to determine the plastic zone radium. The predicted results agree well with measured results which provide valuable theoretical references for the analysis of surrounding rock stability and support reinforcing design of weakly cemented roadways. Finally, a combined supporting scheme of whole section bolting and grouting was proposed based on the original supporting scheme. It is proved that this support plan can effectively control the deformation and plastic zone expansion of the roadway surrounding rock and thus ensure the long-term stable and safe mining.
基金supported by the National Natural Science Foundation of China (Nos. 41230318, 41176077, 4130 4096)the National High-tech R&D Program of China (863) (No. 2013AA092501)+2 种基金the PhD Program Foundation of the Ministry of Education of China (No. 201301 32120014)the Fundamental Research Funds for the Central Universities (Nos. 1313017, 1362013)Major National Science and Technology Programs (No. 2016ZX 05024-001-002)
文摘The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.
