Cooperative Research Centre for Greenhouse Gas Technologies

This study evaluates the accuracy of generating pseudo-capillary pressure curves from laboratory NMR (NMR) anal. and NMR wireline log data by comparing threshold pressures and curve characteristics to rock-derived mercury injection capillary pressure (MICP) anal.Accurate production of pseudo-capillary pressure curves from NMR data could negate or reduce the need for expensive and rig-time-consuming core acquisition and subsequent MICP anal.Successful application of this technique will allow production of pseudo-capillary pressure curves for large stratigraphic intervals at a significantly reduced cost and help to better constrain petroleum reserves and improve near field exploration prediction outcomes.The Tindilpie-11 well in the Cooper Basin, Australia, was used as a case study because of extensive existing conventional ore anal. and presence of an NMR wireline log covering the sampled intervals in the Permian-aged Patchawarra Formation.Six core samples underwent MICP and laboratory NMR analyses, with capillary pressure curves generated for each method.Six pseudo-capillary pressure curves were also generated from the NMR wireline log data at the coincident sample depths.The pseudo-capillary pressure curves generated from laboratory NMR data closely resemble the MICP results (mean threshold pressure error of 0.63 MPa absolute [91.4 psi]) and proved the applicability of this approach.The NMR wireline log data used is an average over a ∼1.6 m interval, which has likely led to discrepancies when compared with laboratory NMR pseudo-capillary pressure curves and MICP curves.Nonetheless, this study confirms the applicability of using laboratory NMR data to generate pseudo-capillary pressure curves that resemble MICP results.Continued development of NMR log technol. and reduced logging speeds will improve the data resolution and ultimately provide high d. NMR data that can be used to create pseudo-capillary pressure curves for large stratigraphic intervals at a significantly reduced cost.KEY POINTSPseudo-capillary pressure curves derived from NMR data.Reservoir characterization requiring minimal rock acquisition for ground truthing.

In practice, carbon capture processes in CCS (Carbon Capture and Storage) consist of two main units: the carbon dioxide (CO₂) capture plant and the CO₂ compression unit.This study considered a hybrid capture system that combined both the capture and the compression units.In doing so, the conventional multi-stage CO₂ compression unit was replaced with a low-temperature carbon capture separation and pressurising step.The advantages of replacing the compression unit are two-folds: firstly, the low-temperature separation unit can further purify the CO₂ stream and secondly, it produces liquid CO₂ that can be pumped to the supercritical state required for transportation and sequestration.In order to take advantage of the extra CO₂ purification of the low-temperature separation unit, a vacuum swing adsorption (VSA) was used as the initial CO₂ recovery stage.A hybrid process has a higher degree of freedom available and therefore a Multi-Objective Optimization (MOO) technique in combination with heat integration was used to optimize the total shaft work and the overall CO₂ recovery rate of the capture process.The MOO provided a range of optimal solutions where the total shaft work increased with the total CO₂ being recovered by the hybrid process.However, a min. optimum was determined for the total specific shaft work required at an overall recovery rate of 88.9%, which required 1.40 GJ/(t CO₂ captured).

The performance of a 4-bed/16-step vacuum swing adsorption cycle containing three pressure equalization (PE) steps has been analyzed in order to understand the role played by the multiple PE steps in the process performance.The cycle was designed for CO₂ capture from a feed gas mixture of 15% CO₂/85 %N₂, with zeolite ×13 adsorbent from UOP (PSO2HP).Simulations were performed with the help of the com. Aspen Adsorption simulator to help interpret the exptl. results.It was found that CO₂ loading decreased only slightly, but N₂ loading decreased significantly and uniformly across the bed after each PE step.Thus, while CO₂ working capacity remained almost constant, working selectivity and CO₂ product purity increased with the number of PE steps.An exptl. purity of 91.3 mol% CO₂ could be obtained at a recovery of 77% at 3 kPa desorption pressure, with a cycle containing 3 pressure equalization steps.Specific energy consumption (calculated with a constant pump efficiency of 70 %) was calculated as 0.3 MJ/kg CO₂, which was lower than the 1 and 2 pressure equalization cycles.We evaluated 2-bed and 3-bed cycles containing one and two pressure equalization steps resp., by means of simulation in order to compare their performance with the base 4-bed 3PE cycle.For a constant recovery of 75-77%, CO₂ product purities increase by 7.4 and 4.2% (relative) in going from 1PE, to 2PE and 3PE cycles resp., at an evacuation pressure of 3 kPa.Specific energy consumption also decreased with the number of PE steps, owing to the lowering of the starting pressure for desorption and some savings in repressurization energy with the number of PE steps.The specific energy dropped by 13 % in going from 1PE to 2PE and 3PE steps.However, the extra beds and extra cycle time required for the 3PE steps led to a reduction in productivity by almost 33% in going from the 2PE to 3PE cycles.The choice for including addnl. PE steps therefore relies on the tradeoff of capital and operating costs which is strongly location and project specific.