Rock mechanics characteristic of complex formation and faster drilling techniques in Western South China Sea oilfields

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.