Video: Exploiting Shale Creep Deformation to Create Annular Barriers for Well Plugging and Abandonment: Experimental Investigation and Numerical Simulation
- Saeid Enayatpour (Hildebrand Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, TX, USA) | Akshay Thombare (Metarock Laboratories, Houston, TX, USA) | Munir Aldin (Metarock Laboratories, Houston, TX, USA) | Eric van Oort (Hildebrand Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, TX, USA)
- Document ID
- Society of Petroleum Engineers
- Publication Date
- Document Type
- 2019. Copyright is retained by the author. This presentation is distributed by SPE with the permission of the author. Contact the author for permission to use material from this video.
- Creep Deformation, Shale Creep, Well Plugging, Shale Barrier, Well Abandonment
- 0 in the last 30 days
- 0 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 7.00|
|SPE Non-Member Price:||USD 12.00|
Oil and gas wells produce hydrocarbons for a limited number of years, and at the end of their production life they need to be plugged and abandoned. This process has to be done in a safe and economic way. Creep deformation of shale rock in uncemented casing sections may simplify well abandonments considerably. Creep can close the annular gap between a shale formation and an uncemented section of a casing string, generating a barrier that prevents hydrocarbons from flowing to the surface on the annular side. Wells with such a "shale-as-a-barrier" generated by creep now only require abandonment plugs on the inside of the casing, without the need for installation of additional annular barriers. This may eliminate such operations as casing milling and casing pulling, thereby allowing e.g. offshore abandonments to be done rigless, at significantly reduced cost.
This paper presents the first results of an experimental investigation and numerical modeling study into the nature of the "shale-as-a-barrier" phenomenon. Specifically, we focus on laboratory and field scale numerical simulation of creep behavior of North Sea Lark shale rock for oil and gas well plug and abandonment purposes. In our Finite Element simulations of the shale creep phenomenon, we have used the time-hardening creep model, which assumes a non-linear relationship between creep strain and stress, temperature and time. The model parameters were obtained from a curve fit of laboratory experimental results conducted for a creeping shale. Then, using the experimentally-derived parameters, numerical simulation was performed for a laboratory scale model and result was validated against laboratory results. Once this validation had taken place, the model size was extended to the field scale for prediction of annular closure time and barrier formation. Simulations show a strong correlation between rock stiffness and annular gap closure time, as expected; hence, the success of any "shale-as-a-barrier" project is a distinct function of shale rock stiffness. Lowering near-wellbore stiffness artificially may accelerate annular barrier creation of slowly creeping shale formations.