Application of geomechanical model to analyse wellbore stability and determination of safe mud weight window for drilling operation and engineering
Abstract
In designing the drilling plans for exploration and development wells in Vietnam, the casing depth and seat as well as mud weight have mainly been calculated and selected using the conventional well design, which is based on the fracture pressure and pore pressure with a safety margin of about 0.5ppg. The selection of a large mud weight window increases well costs for drilling mud and chemicals. The increasing of mud weight properties will also reduce the life span of mud circulation system such as mud pumps, top drive, high pressure pipes and hoses, surface safety valves, etc. and other risks may occur to reduce the rig’s operation efficiency. On the other hand, inappropriate mud weight selection results in nonoptimal casing seat, thus increasing well costs and cost of drilling operation. Hence, the authors propose to apply a geomechanical model to predict the wellbore stability, on that basis to select the optimal mud window based on the real data collected from Hai Thach field, Nam Con Son basin.
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