Santos Ltd. (South Australia Northern Territory Oil Search) is an Australian oil and gas exploration and production company, with its headquarters in Adelaide, South Australia. It owns liquefied natural gas (LNG), pipeline gas, and oil assets. It is the biggest supplier of natural gas in Australia, with its plants in the Cooper Basin in South Australia and South West Queensland supplying the eastern states of Australia. Its operations also extend to the seas off Western Australia and Northern Territory.The company has been criticised by environmentalists and others for its high level of greenhouse gas emissions, its lobbying of political parties, and various incidents causing contamination. Santos provides sponsorship of several arts festivals and bodies, charities, and the University of Adelaide's Australian School of Petroleum.
Abstract Hydraulic fracturing is one of the key stimulation methods used to enhance gas deliverability from coal seam gas (CSG) reservoirs. However, effective containment of fractures within the target coal intervals is often challenging due to the weak stress contrast between coal beds and adjacent sand-shale formations. To evaluate vertical fracture propagation and confirm the length of fracture containment along the borehole, wireline borehole acoustic data was acquired in two vertical wells before hydraulic fracturing in open hole (pre‑frac) and after hydraulic fracturing in cased hole (post‑frac). The methodology relies on comparing the pre‑ and post‑fracture acoustic signatures of the formation (Sheng-Qing Lee, Huan-Ran Li et al: 2018). The pre‑fracturing sonic data establishes the baseline of the acoustic properties such as shear wave anisotropy and acoustic behaviour of intact formations. The post‑fracturing borehole acoustic data reveal changes in acoustic wave amplitude, shear slowness, scattering, and attenuation associated with induced fractures near the borehole. Since fractures cause directional variations in acoustic energy propagation, both cross-energy based and slowness-based anisotropy serve as reliable indicators of fracture presence and orientation. The pre‑fracturing borehole acoustic data acquired in open hole showed very weak anisotropy to nearly isotropic formation, consistent with the unfractured baseline condition. In contrast, the post‑fracturing sonic data acquired in cased hole after hydraulic fracturing exhibited significantly stronger shear wave anisotropy across all three anisotropy indicators, which confirmed that the hydraulic fractures altered the formation's acoustic properties around the wellbore. The magnitude and depth distribution of these anisotropic responses showed the vertical extent of induced fractures along the borehole (relative to the perforated zones). In Well A, across Perforation Interval 1 (1237.29–1248.96 m MD), numbered by fracturing sequence from deepest to shallowest, the interpreted fracture height extends from 1256 m MD to 1219 m MD, indicating upward and downward fracture growth beyond the perforated zone. Similarly, across Perforation Intervals 3 (1162.44–1163.44 m MD) and 2 (1187.64–1202.24 m MD), the induced fracture network is interpreted to be connected from 1127 m MD to 1208.5 m MD, demonstrating vertical connectivity. These results demonstrate that high‑resolution borehole acoustic measurements using wireline logging tools, when acquired both pre‑ and post‑stimulation, can provide a robust way to quantify the fracture height growth in CSG reservoirs in addition to tight sand and unconventional reservoirs. This approach enables operators to evaluate fracture containment and optimize stimulation design to reduce the risk of hydraulic fractures propagating into non‑target formations.
Abstract Formation Isolation Valves (FIV) are integral to deepwater lower completion designs, safeguarding the well during upper completion installation. Typically, FIVs are hydraulically opened via a prescribed pressure cycle from surface. Although reliable, rare failures of the primary system necessitate contingency operations using electric-line or coiled-tubing conveyed methods. This paper shares lessons learned from a deepwater operation offshore Northern Australia, focusing on contingency planning and the role of real-time data in FIV management. Hydraulically activated FIVs commonly incorporate mechanical shifting contingencies. Industry standard practice is to have electric-line mechanical shifting assemblies on standby during upper completion activities; while coiled tubing may also be deployed, deepwater rigs often lack CT packages. In this operation, following hydraulic activation failure, an electric-line shifting tool was run and encountered obstruction approximately twenty feet above target depth. Subsequent runs of slickline bailers on electric-line tractor conveyance retrieved significant debris. The operation was paused to optimize debris removal; enhanced e-line conveyed bailers were mobilized on return, resulting in nineteen runs until the FIV ball valve was tagged. A mechanical shifting attempt produced a surface pressure response, but downhole sensor data revealed the valve remained only partially open. After flowing the well and analyzing ongoing data, a second shifting attempt achieved full FIV opening. This operation highlighted two critical factors: robust contingency planning and data-driven decision-making. Even highly dependable FIVs can fail; it is imperative to collaborate with manufacturers on root cause analyses and specific mitigation strategies. In this case, incomplete wellbore clean-up was identified as the principal reason for impaired hydraulic actuation; thus, electric-line conveyed suction tools should be considered essential, alongside mechanical shifting tools. Real-time monitoring—including suction pump torque, actuator displacement and force, as well as shifting tool radial force—enabled informed operational choices and near-instant confirmation of debris removal and FIV status, substantially reducing risk and uncertainty. Experience from this operation has prompted reconsideration of contingency design factors such as shifting tool selection (mechanical vs. e-line), debris tolerance of FIVs, suction tool efficiency, and operational turnaround in high-temperature environments. The systematic integration of real-time data into contingency execution delivers substantial improvements in operational reliability for deepwater completions.
Abstract Production optimization in mature gas fields is a complex and challenging task that requires reservoir knowledge captured over several years of production and long-term data management strategies. Traditional surveillance methods for well and reservoir performance are manual, interpretive and do not scale over several wells with high data volumes to make timely decisions. Hybrid models that blend physics and data-driven methods prove to be useful in automatic performance tracking, early detection of anomalous events, classifying actionable opportunities, and help in continuous system optimization. An automated solution was designed, consisting of 14 reservoir and production workflows to improve asset operational efficiency for a mature gas basin in Australia. The solution involves workflows that enable continuous optimization through evergreen reservoir, well and network models to maximize reservoir performance, field production capacity, opportunity generation, and exception-based surveillance. Each workflow solves specific problems from bottomhole pressure calculation to network optimization. These workflows are interlinked and together are responsible for production optimization and opportunity generation. In this paper, we discuss the application of our integrated surveillance and optimization system deployed in the Cooper Basin of Australia, and operated by Santos Ltd. The system allowed operators to quickly evaluate and identify several opportunities to improve well productivity within a short span of deployment. The system has captured 5 MM USD generated from automated production opportunity identification and classification. Self-calibrating models, integrated with reservoir and surface networks, provide improved scenario optimization for integrated asset management with a potential 14 MMscf/d uplift in field production. Several improvements in model quality were noted, as well as frequency of model calibration increased from manual updates twice a year to once every week with the automated system. The integrated system has been augmented into existing company processes of capacity determination and business planning. The solution demonstrates the effectiveness of a hybrid modeling system for automatic fields and wells performance tracking, early anomaly detection, actionable opportunity identification, and promotes continuous system optimization. Our focus is to improve asset operational efficiency, optimize production and enhance surveillance processes. The solution utilizes a new generation of hybrid modeling tools that enable continuous asset optimization. Furthermore, the solution augments the capability of engineers by providing a practical way of combining data-driven methods with our understanding of physics.
Accurate estimation of gas compressibility (Z-Factor), viscosity, and enthalpy is vital across conventional hydrocarbon production, greenhouse gas storage, and hydrogen energy applications. Legacy Z-factor correlations like Dranchuk-Abou-Kassem (DAK) and Hall-Yarborough (HY) perform well for typical natural gases but lose accuracy - and sometimes fail - at low temperatures, high pressures, or with inert-rich mixtures. Advanced frameworks such as GERG2008 address a broader range of compositions but are often impractical for spreadsheets and standard engineering workflows due to software, complexity, and compositional constraints. We present a unified thermodynamic model combining a volume-translated Peng-Robinson Equation of State (EOS) for Z-factor, density, enthalpy, Cp, and Joule-Thomson coefficient with the Lohrenz-Bray-Clark (LBC) method for viscosity. The model covers one hydrocarbon and four inert components (H2, N2, CO2, H2S), with parameters tuned to Standing-Katz, NIST, binary vapor liquid equilibrium (VLE) and publicly available experimental Z-Factor data. Validation shows accuracy equal to or better than traditional correlations from 50-300 °F and 14.7-15,000 psia, including gas condensates and associated hydrocarbon gases as well as inert and hydrogen-rich mixtures. Viscosity results closely match reference data. This approach streamlines gas property calculations with a single, analytically solved, spreadsheet-ready framework - facilitating integration into reservoir simulators and meeting the needs of both conventional and emerging carbon dioxide and hydrogen storage workflows. Additionally, in its simplest form, this analytically solvable cubic EOS-based method can be a compact, direct and robust replacement for iterative legacy methods (e.g., DAK, HY), eliminating numerical convergence issues and simplifying integration into standard engineering workflows. All calculations, regression data, and example implementations in Python and Excel VBA are available on GitHub.
The use of gaseous ozone as a means for enhancing coal seam permeability has been investigated, including the effect on subbituminous and bituminous coal from the Surat and Bowen Basins, Australia, respectively. To elucidate the oxidative mechanism, the chemical properties of the Surat coal before and after oxidation was examined using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS). Additionally, gas adsorption techniques and optical microscopy were used to assess physical changes arising from the ozone treatment. Although both the oxygen and ozone treatments (two days duration) increased the oxygen content in the molecular structure of the coal, the ozone introduced significantly more, specifically with the generation of aliphatic ester C--O groups and aromatic carbonyl/ carboxyl C--O groups. In terms of the physical structure of the coal, the micropore volume was slightly reduced by the oxygen treatment but almost eliminated by the ozone treatment. Furthermore, oxygen treatment showed little impact on the coal mass loss while ozone oxidation caused a 0.7% loss in coal weight. Additional tests on a Bowen Basin coal showed an increase in the aperture (4.37%) of a cleat after ozone treatment. These results demonstrate the potential of ozone for coal seam permeability enhancement by merging micropores and increasing cleat apertures whilst maintaining the structural integrity of the coal.
