Case Study: Drilling Horizontal Exploration Shale Gas Wells Efficiently by Collaboration of Subsurface and Drilling Teams Utilizing Geosciences Technology

Abstract

Talisman Energy currently operates and pilots wells in frontier areas for shale gas development. Wellbore stability, and well control issues are the largest contributors to additional costs and non-productive time (NPT) while drilling exploratory, outpost, and wildcat wells. This is a hindrance to many logging and evaluating functions in pilot wells, which are critical to assessing future development decisions. Offset wells are relied upon to guide drilling decisions but in many exploration and frontier areas the nearest relevant offset well may be far away to even be geologically or structurally analogous. Tighter budgets, lower commodity costs, and commitment to lean culture mean that wells need to be drilled with as few surprises as possible by continuously executing the ‘no drilling surprises’ model adapted by other companies. This can be accomplished through continuous improvement cycles and collaborative approach between drilling and sub surface teams. In Talisman's frontier areas, the only laterally extensive sub surface data available before a well is drilled is 2D seismic. Although sometimes overlooked, this can provide critical data about the structural features that might contribute to drilling NPT. An example could be subtle structures that might cause the well to deviate more than normal due bedding inclination or drastic changes in bed dips due to structure. Using a combination of seismic interpretation and geomechanical software, we have been able to accurately predict shear failure and pore pressure gradients along with geohazards that correlate to actual drilling events in pilot wells. This is done to predict a safe mud weight window, horizontal stress directions, and magnitudes for easier drilling operations. Usually, there is a critical disconnect from prognosis to execution. To avoid this problem, the same team that assists the asset in the wellbore stability modeling monitors the drill and makes recommendations to the drilling team as events occur. In shale gas operations, where pilot wells are critical to the assessment of long term development, accelerating the learning curve is essential. Through this collaborative approach between the asset, geomechanics, real time monitoring, and the drilling operations teams; we have been able to drastically reduce well time and costs.