Summary

Here we present a recently developed pyrolysis technique called LIPS (Laser Induced Pyrolysis System) that can be used for a high-resolution definition of total organic carbon (TOC) contents in core samples. Typically, LIPS measurements are performed on a centimeter scale, and hence, the system collects roughly 10,000 TOC values on a 100 meter core. High-resolution TOC-logs are useful to allocate even very thin organic-rich intervals in shale oil / gas plays (also oil shale). The high data densities from LIPS TOC-logs can also be used to calculate more representative average rock properties for selected stratigraphic intervals. Moreover, high-resolution TOC logs can be used to calibrate other well log data such as gamma-ray logs. We have successfully applied the new LIPS technique on several cores coming from oil shale (e.g., Green River) and shale gas (e.g., Barnett) wells in the US and elsewhere.

Introduction

Organic-matter-rich shales can be hundreds of meters thick; however, vertical variability e.g., in terms of organic matter content can be high as on a meter-scale or less [1]. Under suitable thermal maturities these shales become source and reservoir rocks. As many of the thin shale intervals are likely to be hydraulically disconnected such self-sourced " micro-reservoirs" may host fluids of variable composition. For proper resource evaluations and production forecasts it is therefore fundamental to assess kerogen and hydrocarbon fluid properties at high vertical resolution.

The most widely employed methodology to characterize organic matter content and kerogen type is Rock-Eval pyrolysis. The technology has been developed about 30 years ago to assess source rock kerogens in conventional petroleum systems [2]. Depending on the rock sample type (e.g., core, SWC, cutting) the frequency of Rock-Eval analyses will vary; however commonly the vertical resolution is not higher than meter by meter, and hence, rock characteristics of intercalated intervals are not imaged by conventional LECO, Rock-Eval or SRA analyses results.

To acquire high-resolution TOC-logs on drill cores (1 data point / centimeter) a new technique called LIPS (Laser Induced Pyrolysis System) has been developed. The LIPS instrument was originally designed to identify thin tar mats in carbonate reservoirs which may act as permeability barriers. However, high-resolution TOC-logs are also useful to allocate thin organic-rich intervals in shales and to calculate representative average TOC contents for selected stratigraphic intervals. High-resolution TOC logs can also be used for an improved calibration of well log data such as gamma-ray logs.

URTeC 1581024

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