Novel Approach to More Effective Plug and Abandonment Cementing Techniques
- Thomas Eugene Ferg (ConocoPhillips) | Hans-Jacob Lund (ConocoPhillips) | Dan T. Mueller (ConocoPhillips) | Morten Myhre (HydraWell Intervention) | Arne G. Larsen (HydraWell Intervention) | Patrick Andersen (HydraWell Intervention) | Gunnar Lende (Halliburton) | Charles Edwin Hudson (M-I SWACO) | Cato Prestegaard (Halliburton Norway) | David Field (Halliburton Norway)
- Document ID
- Society of Petroleum Engineers
- SPE Arctic and Extreme Environments Conference and Exhibition, 18-20 October, Moscow, Russia
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 1.7 Pressure Management, 3 Production and Well Operations, 4.1.2 Separation and Treating, 1.14 Casing and Cementing, 2.2.2 Perforating, 1.14.4 Cement and Bond Evaluation, 1.6.1 Drilling Operation Management, 1.7.6 Wellbore Pressure Management, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 2 Well Completion, 1.11 Drilling Fluids and Materials, 4.1.5 Processing Equipment, 1.7.5 Well Control, 4.3.1 Hydrates, 1.6 Drilling Operations, 5.3.2 Multiphase Flow, 1.10 Drilling Equipment, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.6.11 Plugging and Abandonment, 1.1.6 Hole Openers & Under-reamers, 1.14.3 Cement Formulation (Chemistry, Properties)
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The effectiveness of a permanent abandonment plug is measured by its ability to bridge the wellbore cross section both vertically and horizontally, including all annuli, with a plugging medium which can withstand the rigors of the environment to which it is exposed (Figure 1 - Barrier Requirements). The most common method for placing a plug in cased hole with an uncemented annulus has required section milling of the casing, making a clean out run and underreaming of the open hole prior to placing a balanced cement plug. A new method is presented which creates a permanent abandonment plug through the use of a system which perforates uncemented casing, washes the annular space and then mechanically places the cement across the wellbore cross section in a single run. This paper outlines the design methods, laboratory testing and operational elements that were assessed during the development phase, as well as the results of field trials used to qualify this technique.
Traditional methods of creating an annulus barrier in uncemented casing require the removal of a section of casing by milling operations, cleaning the created open hole to remove swarf (swarf is defined as metal filings or shavings removed by a cutting tool) and other debris, underreaming the section to expose new formation and then setting a balanced cement plug. These operations can be time consuming and difficult to execute safely and effectively.
Fluids designed for section milling must have sufficient weight to keep the open hole stable and viscosity to suspend and transport swarf and debris to surface. The required fluid viscosity profile for milling operations can generate Equivalent Circulating Densities(ECD) which exceed the fracture gradient of the exposed open hole leading to losses while circulating, swabbing, well control, poor hole cleaning, and packing off of the Bottom Hole Assembly(BHA). These problems can lead to sticking of the milling, clean out or underreaming BHAs because not all swarf and skimmed casing remnants can be cleared from the wellbore. Swarf and casing debris can become strung out along the wellbore lodging in the annular and ram BOP equipment seriously effecting function. At surface, handling equipment must be positioned and installed within the return flow line after the bell nipple and in front of the shakers in order to separate and capture generated metal returns from the active mud system. An example of metal brought to surface during milling operations is included (Figure 2 - Skimmed Casing).
Health, Safety and Environmental challenges are created by the handling and disposal of the generated swarf and debris. The metal returns have sharp angular surfaces and personal protective equipment must be worn to protect hands and eyes. Environmental issues are created from the collection point on the rig to the final disposal site. These issues include classification of the material and documentation, handling, containment, tracking and transport.
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