Abstract
Millions of dollars are spent each year drilling in deepwater areas to prove the presence of hydrocarbons. Wireline formation testers (WFT) are able to capture and retrieve multiple, discreet hydrocarbon fluid samples at in-situ conditions. Once the sample bottles are retrieved at the surface, expeditious sample validation is critical because it provides certainty on sample type and quality. The typical process for wellsite sample validation is often very expensive and risky because it requires a full laboratory restoration apparatus, a portable lab, and trained personnel to handle high-pressure samples —often under unfavorable conditions.
The Advanced Optical Cylinder (AOC) is the latest development in single-phase sampling technology by Baker Hughes. The AOC sample chamber eliminates the high risk and costs associated with sample quality validation in the field and provide clients with very valuable and timely fluid sample data. The AOC is a nitrogen-charged sample tank that provides pressure compensation to retrieve single-phase samples; it incorporates visible-near infrared (Vis-NIR) technology to obtain spectroscopic measurements of the sample within the tank. Capturing a single-phase sample is very important because the accuracy of reservoir fluid samples provides critical information needed for optimal completion and production design. Vis-NIR spectroscopy is a well-established tool used in downhole fluid analysis that provides critical information such as fluid type, sample purity and PVT properties. With the AOC, it is now possible to verify the visible-near-infrared spectra of the captured crude oil or gas sample as soon as the tanks reach the surface, and without the need for sample transfer. Benefits include avoiding lengthy waiting periods for PVT laboratory analysis, ensuring quality samples, and enhancing critical reservoir development decisions.
The AOC provides the best method for non-invasive sample validation of the captured formation fluid sample, using a high-resolution spectrometer that easily connects to the tank (to capture detailed visible and NIR spectra of the pressurized fluid sample). The spectrum is compared to fluid analysis data acquired during WFT sampling; further VIS-NIR spectra analysis j determines contamination, GOR, bubble point, and API gravity.
Field examples are used to demonstrate the application and benefits of in-situ sample validation using the AOC.
