Annuli pressure if not controlled and managed may result in uncontrolled release of high-pressure hydrocarbon fluids from reservoir to the surface. This may cause loss of life, damage to environment, and tarnish the reputation of the company. In this paper, two potential pathways for reservoir fluid to reach the surface through annuli have been examined, and recommendations were provided to diagnose and manage annulus pressures within safe operating limits.
Integrated well integrity assessment to diagnose the root-cause of annulus pressure involved using various tools to measure key parameters needed to make an accurate assessment of root-cause of annulus pressure. For example, thermal numerical models and lab tests were conducted to simulate thermal effects in the well and analyze annulus fluid samples, respectively. Furthermore, echometer was used to measure fluid-level in the annuli, whereas logging tools such as spectral noise, high-precision temperature etc. were used to identify source of any reservoir fluid ingress.
Multiple diagnostic, surveillance and management workflows for outer and inner annuli have been developed. Experiences in implementing these workflows for hundreds of wells in the field have been described and lessons learned have been discussed. Special attention has been paid to the cases with confirmed or suspected lost barriers. Appropriate, cost-efficient levels of diagnostics have been selected and employed to ensure safe operations. Decision trees on how to manage wells with annulus pressures have been discussed, in particular related to planning and execution of pressure bleed-offs, annulus top-ups with heavier fluids, etc. Based on decision trees, cost-efficient levels of diagnostics have been selected and employed to ensure safe operations.
This work provides insights on various tools to diagnose and cost-effectively manage the pressure in the annulus by combining the available tools and software. Company-specific annulus pressure management strategies have been developed and successfully employed to safely operate wells with annulus pressure.