Abstract
An extremely important and often challenging problem associated with drilling inclined wellbores is maintaining mechanical stability. A number of analytical and numerical models are available in the industry, which aid in evaluating the degree of stability expected in a given wellbore. Application of these models requires input of formation rock properties, which are sometimes difficult and costly, or even impossible to obtain Complicating matters, even with the availability and input of these data, the stability models often inaccurately predict the mud weights necessary to maintain the mechanical stability.1–3
A stability analysis was performed to determine the feasibility of drilling a high angle well (63 degrees) from a Gulf of Mexico platform. Due to the lack of core data, the rock strength properties of the shale sections had to be estimated from prior drilling data.
A case study is presented to compare the estimated required mud weights to the actual mud weights needed to drill the high angle well. The procedures used to determine the pore pressure, fracture gradient, overburden and in-situ stress state are also discussed. Both the commercial and in-house software applications used in this analysis are briefly described and evaluated.
In addition, the potential for developing an empirical model to estimate the rock strength properties of shales is examined.
