Reservoir Characterization Utilizing Advanced Geochemical Measurements Acquired at Surface
Authors: Qubaisi Khalid , Haceb Mohamed , Ahmed Haitham , Magnier Caroline 
Published: October 2023

Surface technologies and mud logging services are evolving tools that contribute today to unlocking complex geological settings, which will successfully define oil and gas potentials in a petroleum province. The paper aims to demonstrate the utilization of advanced cuttings analysis and microscopic observations to characterize chemical compositions of reservoirs, describe source rocks, confirm hydrocarbon potential and outline strategies for optimized well placement.

Returned mud brings cuttings to the surface which are usually collected near the well shaker. Acquired rock samples can be studied at the rig site to differentiate stratigraphic units and underline potential reservoirs or source rock levels within a hydrocarbon prone basin. Cuttings analyses are commonly performed with the objective of enhancing the knowledge that is obtainable from sediments. Cuttings data are processed using an on-site laboratory equipment specifically adapted to rock geochemistry. The acquired cuttings are described with high-definition digital microscopes to assess primary geological observations such as mineral content, assemblage, grain size, and homogeneity. These samples will undergo geochemical characterization via a Source Rock Analyzer (SRA). An SRA would assist in evaluating source rock through Total Organic Carbon (TOC) and provides indicators for hydrocarbon volatility using a pyrolysis. The Mineral content and their elemental composition are quantified, respectively, by X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF).

This paper will reveal that there is a difference in the thermal maturity of the organic matter and other pyrolysis parameters, which give indications of the kerogen type, thermal cracking level and define the hydrocarbon potential of the source rocks. The advanced evaluation will show that deeper sediments contain marine source kerogen (type II organic matter) and present high potential productive zones. XRD lithofacies analysis indicates a variation in the mudstone mineral content and gives a better mineral constitution of the carbonate rock matrix. The difference in trace elements measured by XRF is correlated to sedimentological depositional environments. All the mineral alterations validate the level variation of the anoxicity of organic matter during deposition.

The results will conclude that the integration of advanced surface data, digital cutting photos, in-depth cutting analysis, and advanced gas will provide a better evaluation of the hydrocarbon reservoir for an optimized well placement strategy. Furthermore, integrated results acquired optimized the identification of higher organic porosity zones in low permeability reservoirs along the well bore prior to downhole logging planning and further operations.

The hydrocarbon fluid type from advanced gas analyses describes a high potential source rock reservoir, and the presence of wet gas/condensates confirmed the expected fluid in place from the preliminary results made by pyrolysis.