Technical Paper: Integration of Time-Based Dynamics Simulation with Milling and Underreaming System to Implement Reliable Single Trip Solution in Plug and Abandonment Operation

Society: SPE
Paper Number: 178866
Presentation Date: 2016
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A trip-saving well abandonment technology was recently developed to prepare wellbores for the installation of abandonment barriers where poor annular cement quality exists at the required plug location. The trip-saving technology uses a hybrid section milling and underreaming single-trip BHA design to remove casing from the wellbore and underream to virgin formation, eliminating all potential leak paths from the cement barrier. This single-trip BHA is a step change in conventional industry practice whereby the service is typically provided in two dedicated trips: one to mill and one to underream. This paper presents the successful application of the single-trip BHA with the aid of a time-based simulation system in a challenging environment.

The single-trip BHA was required by an operator in The Netherlands, where challenging well conditions and abandonment requirements resulted in the need for underreaming to a 20-in hole size from a wellbore tool restriction OD of 8.5-in. This ultrahigh-ratio reamer arm opening generates significant dynamic loadings on the BHA. To achieve a successful single-trip operation, a 3D time-based drilling dynamic simulation system was employed as a technical solution to ensure:

  • Maximum ROP to meet customer requirements while balancing with BHA limits of operation.
  • Intended underreamer behavior to create a concentric and balanced hole opening across the full hole profile.

The dynamic simulation first carried out a prerun parametric sensitivity study to identify the optimal parameters with high ROP and low vibration/stick-slip ratio. Then the underreamer off-center distance was examined to ensure sufficient new virgin rock exposure in all directions for subsequent cement plug setting.

This dynamic simulation outcome was the creation of a prejob planning roadmap which enabled the job to be executed seamlessly at the rig site whilst achieving the customer Plug and Abandonment (P&A) objectives and ensuring the optimal utilization of each component of the single-trip BHA. The prejob planning roadmap was calibrated against operational performance by recorded stable operation data, observed good reamer arm dull conditions, and good caliper-logged hole quality. In addition, the field data were found to be highly in line with the simulation predictions, validating the accuracy of the time-based dynamic simulation system.

The single-trip operation saved the operator more than 49 h of rig time in abandoning the well. The successful application demonstrated the capability of not only the single-trip BHA, but also the calibrated dynamic simulation which saved substantial rig time and delivered a reliable single-trip service. The the successful operation not only reduced operator costs, but also reduced HSE exposure with less BHA handling on the rig floor.

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