After evaluating multiple well profiles to determine feasibility of performing Dual Gradient Drilling (DGD), a need became apparent for a simpler screening tool that can quickly demonstrate the utility of a given DGD variation compared to other drilling methods. Subsequently, the ‘Depth Ratio method’, or ‘DRx Method’ and ‘Density Depth Ratio Matrix Method’ or ‘ρDRx Matrix Method’ have been developed. These methods utilize basic physics to evaluate DGD’s utility, and are independent of factors such as geographic location and DGD method.

DGD helps in adjusting the pressure exerted by the drilling fluids on the open wellbore and formation by conveniently splitting the annular pressure profile into two separate and manageable gradients at the ‘point of dual gradient (DGp)’. At DGp, there can be modifications to systems’ a) net energy content, b) overall mass, or c) both.

Using the ‘DRx method’ and computing a ‘ρDRx matrix’, the utility of a given DGD system performing under its minimum and maximum densities (where mass and energy changes are expressed in equivalent densities), can be evaluated. This gives a range of feasible operation for the DGD system. This information can then be compared to actual pressure profiles that are being tested for DGD, and a very quick screening for possible application of DGD can be performed.

DRx and ρDRx matrices can be applied for both ‘Normal Gradient Drilling’ (regular/abnormal pressure profiles) and pressure regression profiles (i.e., "Reverse Gradient Drilling").

You can access this article if you purchase or spend a download.