and reservoir conditions accurately, whether to pre-screen a proposed operation or troubleshoot an existing project, requires data from rock samples taken using an array of different equipment for observation, measurement and chemical analysis. “However, micro-CT scanning is the key technology, as it is central to providing a true picture to our clients. We have found that simple before-and-after permeability measurements on a sample can be a misleading metric to predicting oil or gas flow impairment. “Much more accurate is being able to look at the deposition or removal of solids such as clay fines to see how they have migrated, which shows the physical alteration. A major advantage of CT is that it can separate materials based on their density characteristics. Tree- dimensional change modelling from scan data using Avizo visualisation and analysis software is an excellent tool for seeing how the rock is actually altering over time.”

RAPID SUBCONTRACT SCANNING Micro-CT scanning adds value to Premier, Corex’s formation damage testing procedures by aiding interpretation and reducing risk to operators. Rock samples flown down from Aberdeen to Tring are typically 25 to 38mm in diameter and 25 to 50mm long. A team of Nikon Metrology applications engineers is on call and has at its disposal six of the company’s machines

Ian Patey (right) and Leigh Wright (left) from Premier, Corex

to perform subcontract inspection. Turnaround time for Premier Corex’s receipt of results is two days, including flights. Patey says: “We carried out an internet

ABOVE A Premier, Corex rock core sample undergoing subcontract micro-CT analysis at Nikon Metrology’s centre in Tring, Hertfordshire ABOVE LEFT: Premier, Corex has developed a more accurate method of predicting the flow of oil or gas from a well by monitoring in 3D the migration of solids in core samples using CT scan data from Nikon Metrology and Avizo software

search at the outset and identified Nikon as likely to be the best provider of contract CT services due to the company’s size and the fact that it is a commercial organisation rather than a university or R&D centre. We also liked the reassurance of working with the manufacturer of the equipment. Te service we receive is always professional and prompt and the imaging capability of their systems is excellent.” High-resolution micro-CT scanning is non-destructive and can reveal bedding features, fractures, cements and heterogeneities that are smaller than one micron. Te images and data sets produced can show grain size and shape, pore size and network, cements and mineralogy and can potentially visualise fluids and saturation. Te resolution of a typical medical CT scanner would be sufficient to show coarse features but not individual grains, pores, micro-fractures, voids and fine features. Conventional testing techniques such as scanning electron microscopy and thin section are commonly used to understand what has happened within core samples and they provide valuable data. However, they are destructive testing procedures and unable to examine the entire volume of a core sample to show distribution of damage quickly or cost-efficiently, so there is potential to miss the mechanisms involved. Premier, Corex has a patent (GB (granted): GB2524810 and US (publication

number): US2017108483) to take its rock core analytical services a step forward by using volumetrics to quantify the alteration to the sample over time. Micro-CT scanning will be pivotal to its successful application. Te idea is to segregate the damage mechanisms by simulating them in 3D using the virtual scan model, with the flexibility to anticipate how the rock structure will alter under the influence of a single change, a second change, or both. Te technique is being developed to include the ability to overlay combinations of up to seven variables, providing a powerful analytical and predictive tool. Results are supplied in short turnaround times as easy-to-understand, customer- tailored reports with still images or complete data sets. If required, interpretation of results can be carried out. Alternatively, training sessions are available enabling customers to operate X-ray or CT systems themselves to carry out their own inspections at centres around the UK. Te microfocus sources produced in

Tring exclusively for Nikon Metrology’s own CT systems reveal very fine detail. Exclusive, high-flux, rotating targets enable fast scanning times. Te non-destructive technique preserves the item under examination, which can often be expensive, enabling material analysis, assembly evaluation and metrology CT. Accurate simultaneous measurement of internal and external dimensions is possible, plus comparison with CAD models and GD&T (geometric dimensioning and tolerancing). l 11

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