Publications

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This report summarizes the work performed in the prioritization of cavern access wells for remediation and monitoring at the Bayou Choctaw Strategic Petroleum Reserve site. The grading included consideration of all 15 wells at the Bayou Choctaw site, with each active 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, Bryan Mound, and West Hackberry Strategic Petroleum Reserve Sites.

A Hydrostatic Column Model (HCM) was developed to help differentiate between normal "tight" well behavior and small-leak behavior under nitrogen for testing the pressure integrity of crude oil storage wells at the U.S. Strategic Petroleum Reserve. This effort was motivated by steady, yet distinct, pressure behavior of a series of Big Hill caverns that have been placed under nitrogen for extended period of time. This report describes the HCM model, its functional requirements, the model structure and the verification and validation process. Different modes of operation are also described, which illustrate how the software can be used to model extended nitrogen monitoring and Mechanical Integrity Tests by predicting wellhead pressures along with nitrogen interface movements. Model verification has shown that the program runs correctly and it is implemented as intended. The cavern BH101 long term nitrogen test was used to validate the model which showed very good agreement with measured data. This supports the claim that the model is, in fact, capturing the relevant physical phenomena and can be used to make accurate predictions of both wellhead pressure and interface movements.

Bryan Mound 5 ( BM5 ) and West Hackberry 9 ( WH9 ) have the potential to create a significant amount of new storage space should the caverns be deemed "leach - ready". This study discusses the original drilling history of the caverns, surrounding geology, current stability, and, based on this culmination of data, makes a preliminary assessment of the leach potential for the cavern. The risks associated with leaching BM5 present substantial problems for the SPR . The odd shape and large amount of insoluble material make it difficult to de termine whether a targeted leach would have the desired effect and create useable ullage or further distort the shape with preferential leaching . T he likelihood of salt falls and damaged or severed casing string is significant . In addition, a targeted le ach would require the relocation of approximately 27 MMB of oil . Due to the abundance of unknown factors associated with this cavern, a targeted leach of BM5 is not recommended. A targeted leaching of the neck of WH 9 could potentially eliminate or diminis h the mid - cavern ledge result ing in a more stable cavern with a more favorable shape. A better understanding of the composition of the surrounding salt and a less complicated leaching history yields more confidence in the ability to successfully leach this region. A targeted leach of WH9 can be recommended upon the completion of a full leach plan with consideration of the impacts upon nearby caverns .

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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.

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U.S. Strategic Petroleum Reserve (SPR) oil storage cavern West Hackberry 117 was tested under extended nitrogen monitoring following a successful mechanical integrity test in order to validate a newly developed hydrostatic column model to be used to differentiate between normal "tight" well behavior and small-leak behavior under nitrogen. High resolution wireline pressure and temperature data were collected during the test period and used in conjunction with the hydrostatic column model to predict the nitrogen/oil interface and the pressure along the entire fluid column from the bradenhead flange nominally at ground surface to bottom of brine pool. Results here and for other SPR caverns have shown that wells under long term nitrogen monitoring do not necessarily pressurize with a relative rate (P N2 /P brine) of 1. The theoretical relative pressure rate depends on the well configuration, pressure and the location of the nitrogen-oil interface and varies from well to well. For the case of WH117 the predicted rates were 0.73 for well A and 0.92 for well B. The measured relative pressurization rate for well B was consistent with the model prediction, while well A rate was found to be between 0.58-0.68. A number of possible reasons for the discrepancy between the model and measured rates of well A are possible. These include modeling inaccuracy, measurement inaccuracy or the possibility of the presence of a very small leak (below the latest calculated minimum detectable leak rate).

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This presentation describes crude oils, their phase behavior, the SPR vapor pressure program, and presents data comparisons from various analytical techniques. The overall objective is to describe physical properties of crude oil relevant to flammability and transport safety

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SANSMIC is solution mining software that was developed and utilized by SNL in its role as geotechnical advisor to the US DOE SPR for planning purposes. Three SANSMIC leach modes - withdrawal, direct, and reverse leach - have been revalidated with multiple test cases for each mode. The withdrawal mode was validated using high quality data from recent leach activity while the direct and reverse modes utilized data from historical cavern completion reports. Withdrawal results compared very well with observed data, including the location and size of shelves due to string breaks with relative leached volume differences ranging from 6 - 10% and relative radius differences from 1.5 - 3%. Profile comparisons for the direct mode were very good with relative leached volume differences ranging from 6 - 12% and relative radius differences from 5 - 7%. First, second, and third reverse configurations were simulated in order to validate SANSMIC over a range of relative hanging string and OBI locations. The first-reverse was simulated reasonably well with relative leached volume differences ranging from 1 - 9% and relative radius differences from 5 - 12%. The second-reverse mode showed the largest discrepancies in leach profile. Leached volume differences ranged from 8 - 12% and relative radius differences from 1 - 10%. In the third-reverse, relative leached volume differences ranged from 10 - 13% and relative radius differences were %7E4 %. Comparisons to historical reports were quite good, indicating that SANSMIC is essentially the same as documented and validated in the early 1980's.

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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.

Metastable water-in-crude-oil emulsion formation could occur in a Strategic Petroleum Reserve (SPR) cavern if water were to flow into the crude-oil layer at a sufficient rate. Such a situation could arise during a drawdown from a cavern with a broken-hanging brine string. A high asphaltene content (> 1.5 wt %) of the crude oil provides the strongest predictor of whether a metastable water-in-crude-oil emulsion will form. However there are many crude oils with an asphaltene content > 1.5 wt % that don't form stable emulsions, but few with a low asphaltene content that do form stable emulsions. Most of the oils that form stable emulsions are "sour" by SPR standards indicating they contain total sulfur > 0.50 wt %.

The storage caverns of the US Strategic Petroleum Reserve (SPR) exhibit creep behavior resulting in reduction of storage capacity over time. Maintenance of oil storage capacity requires periodic controlled leaching named remedial leach. The 30 MMB sale in summer 2011 provided space available to facilitate leaching operations. The objective of this report is to present the results and analyses of remedial leach activity at the SPR following the 2011 sale until mid-January 2013. This report focuses on caverns BH101, BH104, WH105 and WH106. Three of the four hanging strings were damaged resulting in deviations from normal leach patterns; however, the deviations did not affect the immediate geomechanical stability of the caverns. Significant leaching occurred in the toes of the caverns likely decreasing the number of available drawdowns until P/D ratio criteria are met. SANSMIC shows good agreement with sonar data and reasonably predicted the location and size of the enhanced leaching region resulting from string breakage.

The U.S. Strategic Petroleum Reserve implemented the first stage of a leach plan in 2011-2012 to expand storage volume in the existing Bryan Mound 113 cavern from a starting volume of 7.4 million barrels (MMB) to its design volume of 11.2 MMB. The first stage was terminated several months earlier than expected in August, 2012, as the upper section of the leach zone expanded outward more quickly than design. The oil-brine interface was then re-positioned with the intent to resume leaching in the second stage configuration. This report evaluates the as-built configuration of the cavern at the end of the first stage, and recommends changes to the second stage plan in order to accommodate for the variance between the first stage plan and the as-built cavern. SANSMIC leach code simulations are presented and compared with sonar surveys in order to aid in the analysis and offer projections of likely outcomes from the revised plan for the second stage leach.

A very important aspect of the Department of Energys (DOEs) Strategic Petroleum Reserve (SPR) program is regulatory compliance. One of the regulatory compliance issues deals with limiting the amount of volatile organic compounds (VOCs) that are emitted into the atmosphere from brine wastes when they are discharged to brine holding ponds. The US Environmental Protection Agency (USEPA) has set limits on the amount of VOCs that can be discharged to the atmosphere. Several attempts have been made to quantify the VOC emissions associated with the brine ponds going back to the late 1970s. There are potential issues associated with each of these quantification efforts. Two efforts were made to quantify VOC emissions by analyzing VOC content of brine samples obtained from wells. Efforts to measure air concentrations were mentioned in historical reports but no data have been located to confirm these assertions. A modeling effort was also performed to quantify the VOC emissions. More recently in 2011- 2013, additional brine sampling has been performed to update the VOC emissions estimate. An analysis of the statistical confidence in these results is presented here. Arguably, there are uncertainties associated with each of these efforts. The analysis herein indicates that the upper confidence limit in VOC emissions based on recent brine sampling is very close to the 0.42 ton/MMB limit used historically on the project. Refining this estimate would require considerable investment in additional sampling, analysis, and monitoring. An analysis of the VOC emissions at each site suggests that additional discharges could be made and stay within current regulatory limits.

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.