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The effects of 8 typhoons which passed by coldcore eddy (CCE) areas in the South China Sea (SCS) from 1997 to 2009 were observed and evaluated. The changes in the preexisting CCE acted upon by typhoons were described by eddy kinetic energy (EKE) and eddy available gravitational potential energy (EAGPE). The mechanical energy of CCE was estimated from a two-layer reduced gravity model. Comparing with the scenario that typhoon passes by the region without CCEs, the preexisting CCE area plays an important role in the increase of chlorophyll-a (chl-a) concentration in the CCEs impacted by the typhoons. The preexisting chl-a in CCE is about 25%~45% (8%~25%) of postexisting chl-a in CCE for higher (slower) transit speed typhoons. If the EAGPE of CCE increases greatly after typhoon passing by with slow transit speed, so does the chl-a in the CCE area. The EKE (EAGPE) changes of the preexisting CCE are in the order of O(1014~1015 J). EKE and EAGPE of CCE are dominantly enhanced by typhoon with slow transit speed (<3 m/s) and the posttyphoon EAGPE is always larger than posttyphoon EKE for 8 cases. The maximum EAGPE change of the preexisting CCE reaches 5.11×1015 J, which was induced by typhoon Hagibis. [ABSTRACT FROM AUTHOR]

Abstract: In order to increase the rate of penetration (ROP) and to reduce cost, we tested detritus for mineral components to study the lithological characters of the deep-sea complex formation of Western South China Sea oilfields. The prediction models of rock mechanics parameters were established based on the experiments results of the uniaxial compressive strength (UCS), drillability, hardness, plasticity and abrasivity tests of cores sampled from the complex formation. We plotted profiles of rock mechanics parameters of 30 wells and three dimensional (3D) drillability planes using the log data to reveal the complex formations distribution and their rock mechanical properties. Then, the rock breaking mechanism of complex formation of cone and PDC bit are studied. According to rock mechanics characteristic of complex formation and adjacent well drilling data, we recommend the bit structure, drilling methods and drilling parameters for the northern Gulf Basin (NGB) and Pearl River Mouth Basin (PRMB) oilfields. The research results are used to guide the drilling work of Z-10-9-1 and Z-11-1-8AS1 well in the NGB and C-14-2-1 well in the PRMB, compared with the adjacent wells, the average drilling footage and ROP increase by 98% and 117.8%, respectively. [Copyright &y& Elsevier]