The Bureau of Land Management (BLM), US Department of the Interior has asked Sandia National Laboratories (SNL) to perform scientific studies relevant to technical issues that arise in the development of co-located resources of potash and petroleum in southeastern New Mexico in the Secretary’s Potash Area. The BLM manages resource development, issues permits and interacts with the State of New Mexico in the process of developing regulations, in an environment where many issues are disputed by industry stakeholders. The present report is a deliverable of the study of the potential for gas migration from a wellbore to a mine opening in the event of wellbore leakage, a risk scenario about which there is disagreement among stakeholders and little previous site specific analysis. One goal of this study was to develop a framework that required collaboratively developed inputs and analytical approaches in order to encourage stakeholder participation and to employ ranges of data values and scenarios. SNL presents here a description of a basic risk assessment (RA) framework that will fulfill the initial steps of meeting that goal. SNL used the gas migration problem to set up example conceptual models, parameter sets and computer models and as a foundation for future development of RA to support BLM resource development.
The Department of Energy, in response to requests from the U.S. Congress, wishes to maintain an up - to - date table documenting the number of available full drawdowns of each of the caverns owned by the Strategic Petroleum Reserve. This information is important for assessing the SPR's ability to deliver oil to domestic oil companies expeditiously if national or world events dictate a rapid sale and deployment of the oi l reserves. What factors go into assessing available drawdowns? The evaluation of drawdown risks require the consideration of several factors regarding cavern and wellbore integrity and stability, including stress states caused by cavern geometry and oper ations, salt damage caused by dilatant and tensile stresses, the effect on enhanced creep on wellbore integrity, the sympathetic stress effect of operations on neighboring caverns. Based on the work over the past several months, a consensus has been bui lt regarding the assessment of drawdown capabilities and risks for the SPR caverns. This paper draws upon the recently West Hackberry model upgrade and analyses to reevaluate and update the available drawdowns for each of those caverns. Similar papers for the Bryan Mound, Big Hill, and Bayou Choctaw papers will be developed as the upgrades to those analyses are completed. The rationale and documentation of the methodology is described in the remainder of this report, as are the updated estimates of availab le drawdowns for the West Hackberry caverns. ACKNOWLEDGEMENTS The author would like to thank Byoung - Yoon Park, Anna Lord, Barry Roberts, Moo Lee, and David Borns for their review and support of this work.
This report presents computational analyses that simulate the structural response of crude oil storage caverns at the U.S. Strategic Petroleum Reserve (SPR) West Hackberry site in Louisiana. These analyses evaluate the geomechanical behavior of the 22 caverns at the West Hackberry SPR site for the current condition of the caverns and their wellbores, the effect of the caverns on surface facilities, and for potential enlargement related to drawdowns. These analyses represent a significant upgrade in modeling capability, as the following enhancements have been developed: a 6-million-element finite element model of the entire West Hackberry dome; cavern finite element mesh geometries fit to sonar measurements of those caverns; the full implementation of the multi-mechanism deformation (M-D) creep model; and the use of historic wellhead pressures to analyze the past geomechanical behavior of the caverns. The analyses examined the overall performance of the West Hackberry site by evaluating surface subsidence, horizontal surface strains, and axial well strains. This report presents a case study of how large-scale computational analyses may be used in conjunction with site data to make recommendations for safe depressurization and repressurization of oil storage caverns with unusual geometries and close proximity, and for the determination of the number of available drawdowns for a particular cavern.
This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve (SPR) West Hackberry site. The cavern field comprises 22 caverns. Five caverns (6, 7, 8, 9, 11) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 17 caverns (101-117) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a three-dimensional geomechanics model of the site that predicts deformations, strains, and stresses. Future leaching scenarios corresponding to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the model to capture operational practices in the field. The results of the finite element model are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern stability. The most significant results in this report are relevant to Cavern 6. The cavern is shaped like a bowl with a large ceiling span and is in close proximity to Cavern 9. The analyses predict tensile stresses at the edge of the ceiling during repressurization of Cavern 6 following workover conditions. During a workover the cavern is at low pressure to service a well. The wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension around the edge of the large ceiling span. With time, these stresses relax to a compressive state because of salt creep. However, the potential for salt fracture and propagation exists, particularly towards Cavern 9. With only 200 feet of salt between the caverns, the operational consequences must be examined if the two caverns become connected. A critical time may be during a workover of Cavern 9 in part because of the operational vulnerabilities, but also because dilatant damage is predicted under the ledge that forms the lower lobe in the cavern. The remaining caverns have no significant issues regarding cavern stability and may be safely enlarged during subsequent oil drawdowns. Predicted well strains and subsidence are significant and consequently future remedial actions may be necessary. These predicted well strains certainly suggest appropriate monitoring through a well-logging program. Subsidence is currently being monitored.
This report summarizes the work performed in the prioritization of cavern access wells for remediation and monitoring at the Bryan Mound Strategic Petroleum Reserve site. The grading included consideration of all 47 wells at the Bryan Mound site, with each well receiving a separate grade for remediation and monitoring. Numerous factors affecting well integrity were incorporated into the grading including casing survey results, cavern pressure history, results from geomechanical simulations, and site geologic factors. The factors and grading framework used here are the same as those used in developing similar well remediation and monitoring priorities at the Big Hill Strategic Petroleum Reserve Site.
This report summarizes the work performed in the prioritization of cavern access wells for remediation and monitoring at the West Hackberry Strategic Petroleum Reserve site. The grading included consideration of all 31 wells at the West Hackberry site, with each well receiving a separate grade for remediation and monitoring. Numerous factors affecting well integrity were incorporated into the grading including casing survey results, cavern pressure history, results from geomechanical simulations, and site geologic factors. The factors and grading framework used here are the same as those used in developing similar well remediation and monitoring priorities at the Big Hill and Bryan Mound Strategic Petroleum Reserve Sites.
This paper presents results of three models simulating the hydrological-mechanical behavior of a CO2 injection reservoir and the resulting effects on wellbore system (cement and casing) and seal repair materials. A critical aspect of designing effective wellbore seal repair materials is predicting thermo-mechanical perturbations that can compromise seal integrity. Three distinct computational models comprise the current modeling effort. The first model depicts bench-top experiments of an integrated seal system in an idealized scaled wellbore mock-up being used to test candidate seal repair materials. This model will be used to gain an understanding of the wellbore microannulus compressibility and permeability. The second is a field scale model that uses the stratigraphy, material properties, and injection history from a pilot CO2 injection operation to develop stress-strain histories for wellbore locations from 100 to 400 meters from an injection well. The results from these models are used as input to a more detailed model of a wellbore system. The 3D wellbore model examines the impacts of various loading scenarios on a wellbore system. The results from these models will be used to estimate the necessary thermal-mechanical properties needed for a successful repair material.
This paper presents a study of operational and abandoned large-diameter caverns and their long-term implications for oil storage facilities in domal salt. Two caverns at the U.S. Strategic Petroleum Reserves West Hackberry site, Caverns 6 and 9, present concerns due to their large diameters, unusual shapes and close proximity to each other. The Bryan Mound site has three caverns whose unusual shapes and dimensions have caused concerns about cavern collapse, sinkhole formation, and loss of accessibility to stored oil. This report presents a case study of how historical field data, computational geomechanical analyses, and the implementation of new instrumentation and historical data analyses may be used to develop site operation and monitoring plans for these caverns.
This report summarizes the work performed in developing a framework for the prioritization of cavern access wells for remediation and monitoring at the Big Hill Strategic Petroleum Reserve site. This framework was then applied to all 28 wells at the Big Hill site with each well receiving a grade for remediation and monitoring. Numerous factors affecting well integrity were incorporated into the grading framework including casing survey results, cavern pressure history, results from geomechanical simulations, and site geologic factors. The framework was developed in a way as to be applicable to all four of the Strategic Petroleum Reserve sites.
This report addresses recent well integrity issues related to cavern 114 at the Big Hill Strategic Petroleum Reserve site. DM Petroleum Operations, M&O contractor for the U.S. Strategic Petroleum Reserve, recognized an apparent leak in Big Hill cavern well 114A in late summer, 2012, and provided written notice to the State of Texas as required by law. DM has since isolated the leak in well A with a temporary plug, and is planning on remediating both 114 A- and B-wells with liners. In this report Sandia provides an analysis of the apparent leak that includes: (i) estimated leak volume, (ii) recommendation for operating pressure to maintain in the cavern between temporary and permanent fixes for the well integrity issues, and (iii) identification of other caverns or wells at Big Hill that should be monitored closely in light of the sequence of failures there in the last several years.