Pre-drill Well Gradients Estimation using Seismic Data

The need to have an estimation of pore gradient, fracture gradient and overburden gradient prior to drilling a new well is essentially a key requirement to well planners. When planning to drill a new well, the prediction of well gradients consisting of pore, fracture and overburden gradient can be effectively made using data from offset wells such as well logs and drilling parameters. However, when considering drilling a wildcat well in a new area with no offset wells in the surrounding, the estimation of well gradients becomes critical. Drilling in an unknown area with no knowledge of the subsurface pressure distribution poses a great risk to operators economically and operationally. Hence to reduce the risk associated with wildcat wells, this project employs seismic data (two-way time and average velocity) to estimate the pre-drill well gradients from a developed C++ computer program. Pre-drill well gradients estimated from seismic data will provide a good background concerning the formation pressures and possible overpressured zones to be encountered during drilling operations. This will prompt the drilling engineer to design a safe and sound mud weight and casing program that will effectively enable the operator to drill a wildcat well with minimum risk. Sophisticated drilling software such as Drillworks, WellCheck and Landmark are used to transform seismic data into pressure gradients; however obtaining the license for a given software suite is difficult and expensive.