High energy thermal device that can enable rigless P&A through in situ removal of tubing components
NZTC estimates well plugging and abandonment (P&A) represents 40-50% of decommissioning costs. Conventionally, drilling rigs are used to recover tubing and casing strings. Eliminating rigs can reduce the cost of well P&A by up to 50%.
Clearwell Technology’s development of a high energy, thermochemical device,Therm-X-Mill®, enables downhole, in-situ removal of production tubing and casing components, eliminating the requirement to recover the completion string out of the well during P&A. Deployed through tubing, via conventional well intervention methods, the technology can enable rigless P&A.
Supported by OGTC, this project addresses the Technology Leadership Board’s (TLB) challenge to cut decommissioning costs and drive efficient offshore operations. The objective was to undertake a study to develop a mathematical model to predict thermal lance burning behaviour during well P&A. By reviewing the thermodynamic properties and chemical reactions, along with experimental data, thermodynamic, chemical, energy and hydrodynamic models were assembled and used to analyse and predict the outcome of the process.
This disruptive technology offers significant cost reductions by enabling rigless P&A. This can save approximately 5 – 20 days of rig time per well abandonment.
A significantly enhanced understanding of the thermal lance combustion process and its suitability for use in oil and gas wells for thru-tubing, in-situ tubing/casing removal was obtained as a result of the study.
The project was successful in delivering the following key focus areas:
- Analysis of the thermal lance at surface and sea level conditions and prediction of its performance at depth in well bore conditions
- Development of models to quantitatively describe the operation of a thermal lance
- Examination of the potential safety risks
- Recommendations for the next stages of development
The study concluded that there is a window in which the technology will safely operate in downhole well conditions. The location and size of the window depends on the steady state temperature at the tip of the tool, which is established through interplay between the combustion reaction kinetics and the heat transfer rates.
The main challenges are the values of the intrinsic kinetics of iron combustion and how the kinetics are modified at high pressures. It is recommended to progress the technology by conducting more experiments at atmospheric pressure, including measuring the velocity of combustion while controlling several variables. Following atmospheric testing, several high-pressure experiments will be undertaken in a test cell to validate and/or inform the thermodynamic, hydrodynamic, mathematical and chemical models and will ultimately aim to confirm the stability and viability of the reaction in a simulated wellbore environment. Successful completion of the high-pressure testing will pave the way for field trials.
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