Objectives/Scope Underground hydrogen storage (UHS) has been raising more interest to safely and cost-effectively store hydrogen at large-scale to help the transition from fossil fuel to sustainable energy and to achieve net-zero emission target. During hydrogen subsurface storage particularly in depleted gas reservoirs, the wellbore plays an important role in injection and reproduction to meet seasonal energy demand. However, it is still unclear how wellbore cement would react with stored hydrogen in the presence of formation brine, which may effect long-term cement integrity. We thus performed thermodynamic modelling on cement reactions with hydrogen and water at reservoirs conditions. Methods, Procedures, Process The dissolution of individual components of cement including C3S, C2S, C3A, C4AF and gypsum of Class G/H, and potential precipitation of twenty secondary minerals were simulated at an infinite time scale at reservoir temperature and pressure (representing the worst case scenario of cement degradation from geochemical perspective; in real case, the degree of cement degradation would be much less than the results from thermodynamic modelling as it is a time-dependent process). The extent of cement mineral reactions with hydrogen was compared with that of methane and carbon dioxide to assess the wellbore cement integrity during UHS compared to UGS and CCS. Results, Observations, Conclusions The cement hydration process would lead to the transformation of the major cement compositions C3S and C2S to C1.5SH (CSH) and portlandite. Adding hydrogen would only slightly change the percentage of C1.5SH and portlandite and generate a small fraction of new mineral mackinawite. As a comparison, adding methane would generate a considerable amount of calcite. When CO2 is involved, all CSH compounds would transform to calcite through the cement carbonation process. Overall, the compositional mineral phases of cement after cement hydration is more closed to the case involving H2 compared to CH4 and CO2, implying a relatively low risk of wellbore cement degradation during UHS. Novel/Additive Information Our work underlines the importance of incorporating geochemical modelling in hydrogen geo-storage evaluation when using existing old wells and new drilled wells.
Oil production from Cooper/Eromanga started in 1978, peaked in the 1980s and began a steady decline. Oil production from the Western Flank commenced in 2002 and has steadily increased. In the year until July 2014, a total of 8.6 million BBL of oil was produced from 16 active fields along the Western Flank, bringing the cumulative total to 24 million BBL. Western Flank oil has underpinned a ten-fold growth in market capitalisation in four listed Australian companies: Beach Energy, Drillsearch Ltd, Senex Energy and Cooper Energy. Two sandstone plays dominate the Western Flank petroleum geology: the Namur Sandstone low-relief structural play and the mid-Birkhead stratigraphic play. The use of 3D seismic has improved the definition of both plays, increased exploration success and optimised field appraisal and development drilling. Success rates have improved despite most Namur structural closures being close to the resolution margin for depth conversions (less than 8 m). Seismic attribute mapping is being refined in the more difficult search for mid-Birkhead stratigraphic traps with recent exploration discoveries indicating improved success. Reservoir properties in the Namur are excellent with multi-Darcy permeability, unlimited aquifer strength, low gas/oil ratio (GOR) and low residual oil saturation. This combination leads to an oil recovery factor greater than 75%. Initial free-flow production rates commonly exceed 6,000 BBL per a day. The mid-Birkhead reservoir is also of high quality but the lack of a strong aquifer drive reduces primary recovery. New and re-processed 3D seismic and water-flood projects are expected to drive further discoveries, reserve and production growth.
Structural closures on the western flank of the Patchawarra Trough in the Cooper–Eromanga Basin are truly low relief; drilling opportunities regularly target hydrocarbon columns of similar magnitude to the uncertainty of depth prediction. Improving the accuracy and precision of depth prediction will reduce risk for drilling opportunities, and improve drilling success rates. A detailed study of the near surface geology (surface to ~500 m depth) of the western flank of the Patchawarra Trough has been undertaken to better understand the effect of observed geological variations of the near surface on depth prediction at deeper target levels. The stratigraphic interval investigated includes the top of the Eromanga Basin and the entire Lake Eyre Basin, which is sparingly studied and routinely overlooked in the statics and velocity modelling process. This study analysed recently acquired cased-hole sonic logs in conjunction with gamma logs and mudlog data to map out the observed geological variations, and construct a 3D velocity model of the near surface. Variations of layer thickness and seismic velocity were input into Monte Carlo simulations to investigate sensitivities of each formation on two-way travel time and depth prediction. This investigation has found that velocity variations of the Weathered Winton Formation, and thickness variations of the Namba Clastics have the greatest impact on imaging of structures at depth. Independently, these have the potential to completely conceal or create structures in the time domain. Continued efforts in improved understanding of the near surface will subsequently lead to enhanced imaging of structures, which can then be used in the mapping of structural closures in petroleum exploration and development.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.