Thru-tubing wellbore cement bond has potential to unlock rigless P&A opportunities, optimising inspection and saving up to £550 million
Project Summary
NZTC supported BHGE to evaluate a technology that delivers cement logging through multiple casing strings, an advancement on existing solutions which can only deliver logging behind one casing or tubular. A means of inspecting the quality and quantity of cement in the annulus behind casing does not currently exist without removing the wellbore tubing. If it were possible to deploy a tool to inspect the casing annulus cement from within the tubing, additional costs could be avoided and the potential for thru-tubing and rigless abandonments could be realised.
The aim was to evaluate a number of potential delivery models and resulted in a four-month feasibility study of BHGE’s nXis multi-nodal, thru-tubing inspection system. nXis is composed of neutron, x(y)-ray, electromagnetic and ultrasonic inspection techniques. This project would provide proof of concept, showing that combining the techniques would allow defect detection and live, in-situ, 3D visualisation of wellbore defects.
Industry value:
By eliminating the requirement to removing tubing, the industry could benefit from significant cost savings by unlocking rigless abandonment opportunities.
This technology has the potential to deliver industry savings between £105-£550million, based on analysis of the anticipated UKCS P&A well count up to 2025, by assuming that between 10-50% of the subsea wells could be inspected to deliver thru-tubing abandonments.
Key results:
The project was successful, proving the concept of multi-modal joint analysis with each logging modality showing unique sensitivity to distinct geometrical and physical characteristics of the well.
Simulations confirmed the challenge and complexity of evaluating cement integrity thru-tubing for plug and abandonment applications.
Lessons learned:
Now that the initial framework has been established, planning for the next phase of the project has begun.
Future activities will include:
- The design and construction of a test fixture for evaluating the multi-modal, lab-based test articles
- To build and test pulsed-neutron/gamma-ray/acoustic-based test articles to acquire experimental data for validating and refining simulation models
- To investigate additional logging modalities with complementary responses
- To further enhance data fusion capabilities by refining algorithms through the use of acquired and refined synthetic data
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