Predicting Reservoir Fluid Properties from Drill Cuttings: Application of GPC-UV Method for Reservoir Fluid Analysis

Abstract

Drill cuttings are readily available for all wells we drill. Geochemical analysis has been employed to estimate key oil properties, such as API density and viscosity. However, most studies focus on drill cuttings with water-based mud. Identifying reservoir fluids in highly contaminated drill-cutting samples becomes a significant challenge when drilling wells with oil-based mud. Consequently, there is a high business demand for predicting reservoir fluid properties from drill cuttings with oil-based mud. In 2015, Gel Permeation Chromatography (GPC) coupled with ultraviolet (UV) absorbance detection was introduced in the upstream industry. Elias and Gelin demonstrated the capability of the GPC-UV method to predict API gravity from drill-cutting samples with oil-based mud in unconventional reservoirs. This study extended the GPC-UV approach to conventional reservoirs across multiple fields from the Norwegian Continental Shelf and other global assets. We developed a multiple-wavelength method instead of fixed wavelength detection to explore correlations between GPC-UV detections and reservoir fluid properties. The drill cuttings used in this study are from multiple fields from the Norwegian Continental Shelf and other global assets, where oil-based mud was consistently used for well drilling. Consequently, extracts from these cutting samples are contaminated by oil-based mud. Utilizing the GPC-UV method revealed clear oil peaks with the oil-based mud response appearing on the baseline. Correlating these results with GPC-UV data from stock tank oil samples and known reservoir fluid properties enables qualitative determination of fluid type (gas, oil, or water) and estimation of API from new drill cutting samples. A digital solution based on machine learning, leveraging broad GPC-UV measurements, is needed to improve prediction accuracy further. While ongoing studies aim to establish a comprehensive database of GPC-UV measurements for stock tank oil and drill-cutting extracts, the GPC-UV method demonstrates impressive potential for analyzing reservoir fluids in challenging drill-cutting samples. Given the widespread availability of drill-cutting samples, this new method offers a cost-efficient and accurate means of determining reservoir fluid properties without resorting to downhole measurements or sampling. This method could fulfill the vision of considering "every piece of cutting as a PVT sample," with applications ranging from well placement and reservoir management to production optimization, flow assurance, and plug & abandonment.