This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 200504, “Using MPD Well-Design Process To Optimize Design and Delivery of a Deepwater Exploration Well,” by Sharief Moghazy, SPE, Wilmer Gaviria, SPE, and Roger Van Noort, SPE, Shell, et al., prepared for the 2020 SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 21-22 April. The paper has not been peer reviewed.
The complete paper presents a case for using managed pressure drilling (MPD), and the full capabilities of its associated well-design process, to optimize all aspects of the well-delivery process in deep water, including design, safety, and subsurface data acquisition. The process was used to design and drill a deepwater exploration well with an expected pressure ramp and narrow drilling margins while acquiring valuable subsurface data.
Introduction
The operator’s only offset well in the area faced many challenges including a pressure ramp, resulting in narrow drilling margins. The team experienced several margin-related issues, such as kicks and losses, that resulted in permanent abandonment of the well without reaching the objectives.
Given those results, and the subsurface uncertainty, the operator determined that the use of MPD would have mitigated many of the risks and non-productive-time events experienced in that well. The drilling contractor procured a rig fitted with an MPD system to drill a new exploratory well. MPD and the MPD well-design process were employed to increase the likelihood of drilling the well to total depth (TD) safely and successfully by providing the capability to accomplish the following:
Account for pore pressure/fracture gradient (PPFG) uncertainty and navigate the expected pressure ramp and narrow margin sections safely by holding a constant bottomhole pressure and adjusting as needed during drilling operations
Optimize the location of the casing/liner shoes by identifying the pressure profile based on real-time pore pressure data to potentially eliminate casing/liners, streamline the well design, and retain contingency strings in the event of a more-aggressive pore-pressure ramp
Enable early kick and loss-detection capabilities and dynamic influx management to identify, react, and address downhole issues more quickly
Use dynamic formation integrity tests (DFIT), dynamic leakoff tests, and dynamic pore-pressure tests (DPPT) to identify the extremes of the drilling margin, derisk subsurface uncertainty, and make decisions while drilling
The process used hydraulics modeling to assess the feasibility of several potential scenarios and to understand the deepest possible casing points for a particular PPFG case, mud weight (MW), and well-design scheme. After a base-case well design was created, the maximum allowable kick tolerance was determined using an influx management envelope (IME) analysis, which was used as an input for an MPD operations matrix to be used during the operational phase. During the drilling of the well, the use of the MPD system and the calibration of the hydraulics model to the actual subsurface information allowed the team to continue drilling through more-benign conditions and optimize the well-design configuration.
Probabilistic Analysis of the New Plays in Petrel. Exploration Well Design Workshop