Successful Exploration Drilling in a Very Narrow Mud Weight Window with Crossflow Using Automated Managed Pressure Drilling: a Case History in Mexico East

Abstract

The well used for this study, 301, was originally considered "un-drillable". A steep pore pressure ramp combined with loss zones resulted in a cross-flow environment that was very difficult to control, as the drilling window was effectively reduced to less than 0.09g/cc. The ability to precisely control the pressure profile in the annulus is one distinct advantage of Managed Pressure Drilling (MPD). In worst case scenarios with very narrow pore pressure and fracture gradient windows, the tight drilling margin may require the use of an automated MPD system. The system can precisely apply surface back pressure to maintain a balance of flow into and out of the well by maintaining a constant bottom hole pressure and replacing the friction pressure losses in the annular space when the rig pumps are off.During the execution of the well 301, all Automated MPD benefits were applied (Dynamic FIT's, Dynamic Flow Checks and CBHP control) to detect and control kicks, identifying and control ballooning effects and maintaining the bottom hole pressure within the high pressure tight window between 2.426 and 2.451 g/cm 3 . Proper selection, configuration and continuous calibration of the hydraulics simulations during drilling operations was critical to drill the production section and successfully reach target depth. This paper presents the hydraulics modeling during the planning phase and techniques used during execution with the automated MPD system. Following two previous failed attempts, the 301 well was the first successful well to penetrate the reservoir in the Camaronero field, proving automated MPD as a successful drilling technique for this field.