Deepwater Oil and Gas Well Annulus Pressure Management Strategy

Abstract

Deepwater oil and gas wells have complex well body structure, and the multi-layer closed annulus structure formed by free section and sealed section tubing column is easy to absorb heat and generate expansion pressure. In deepwater drilling operation, the rise in temperature of the closed casing annulus is easy to produce the phenomenon of rising annulus pressure, and due to the special characteristics of the underwater wellhead device, it is not possible to release the annulus pressure between the casing, and the high annulus pressure will lead to casing extrusion and deformation, which will seriously threaten the safety and integrity of the wellbore. In order to ensure the smooth progress of deepwater drilling operations and reduce operational risks, corresponding methods and strategies are proposed for the management of annulus pressure in deepwater oil and gas wells. A variety of measures and products have been developed worldwide for engineering measures of annulus pressure management, including optimization of well structure and cementing design, use of rupture discs, foam casing and vacuum tubing, and other measures. This paper analyzes five major categories of prevention methods and control techniques for deepwater oil and gas wells well annulus confinement pressure, which are increasing casing strength (stiffness level, wall thickness), eliminating expanding fluid, blocking heat transfer, balancing fluid thermal expansion and releasing annulus confinement pressure management strategies. Measures to control annulus pressure by increasing casing strength (stiffness level, wall thickness), fully sealing the annulus, vacuum insulated tubing, foam casing, nitrogen foam isolation fluid, non-circumferential pipe shoes and rupture disc casing tools and analyzing their engineering advantages and disadvantages. According to the engineering application experience, the use of rupture disk casing tool to alleviate the annular pressure is currently the most widely used and stable and reliable means in the world. And according to the theoretical knowledge and engineering practice of annular pressure management, the basic strategy of annular pressure management is summarized when rupture disk is adopted as the main means of annular pressure management.