In-Situ Geochemical Analysis of Rock Samples from Simultaneous Wells Enables Field-Wide Formation Characterization in Real-Time

Abstract

A field-based, portable geochemical laboratory provided Real-Time geochemical rock analysis from 23 stratigraphic wells drilled in the Lusitanian Basin (onshore Portugal), in order to characterize an unconventional resource play. A dedicated workflow involving field personnel, operations teams and remote data users optimized rock measurements and facilitated data interpretation.

This type of workflow, and the approach to make the most of a novel data set, can benefit drilling operations across the border. The technique was developed to support in particular the characterization of shale intervals on a number of adjacent wells, but both the technology applied and the workflow developed are adapt to single-well operations and conventional reservoirs.

The geochemical analysis system analyzed 500 rock samples from 21 shallow stratigraphic wells, outcrops and existing deep legacy wells throughout the Lusitanian basin, from very shallow to depths of more than 2000 m. The targets were three separate organic-rich intervals of Jurassic age. For each sample the complete analysis was carried out on-site and comprised: elemental composition analysis, mineralogy analysis, independent measurement of Total Organic Carbon (TOC) and Pyrolysis. The organic data were the more crucial ones: TOC results combined with Pyrolysis provided accurate information of the amount of hydrocarbons that can be generated by the rock (S2), the rock maturity (Tmax) and the kerogene type (Hydrogen Index), characterizing the organic matter.

The sum of equipment, analytical technique and workflow utilized represented a novel approach to unconventional resource play evaluation. The organic geochemical analyzers utilized in the project have been specifically developed and built for field utilization, permitting to obtain accurate results on a large number of samples in a short time. These results are usually provided by remote laboratories, resulting in delayed responses and the impossibility to react while operating. In other cases, data sets which generate new information are not utilized due to the lack of a proper decision making process which takes them into account. This work model solves all these issues with an integrated approach and allows to adjust and to optimize an ongoing drilling campaign real-time according to the incoming results as well as to interpret the novel geochemical dataset together with the new well data and existing geologic information early on.