The Shale Oil Potential of the Posidonia Formation in The Netherlands (2014)
This MSc thesis has been written by former intern Wouter Mezger.
During the last decade shale formations have been successfully explored in the United States and both oil and gas is currently produced from them. This successful development led to a global interest in shale formations. To assess the worldwide shale oil and gas potential, the Energy International Agency (EIA) investigated the shale formations of 43 different countries outside the U.S.. In this, the Netherlands are evaluated to contain 2.7 billion barrels (Bbbl) of Technically Recoverable oil Resources (TRR) in the Epen, Geverik and Posidonia formations. Based upon previous research, Energie Beheer Nederland (EBN) has identified shale formations as possible oil and gas plays.
This study investigates the shale oil potential of the onshore Posidionia formation in the Netherlands and evaluates the assessment of the EIA report. Fourteen Posidonia samples from 7 wells were subjected to a number of measurements on both core plugs and chips. The samples experimental methods included TGA, NMR, SEM, GRI and steady-state flow to analyze the pore size and shape of the rock matrix, the Total Organic Carbon, the maturity, the porosity, the permeability, the pore content, the fluid storage and the flow mechanism of the samples. When combined these parameters can give a prediction of the shale oil potential of a rock. In addition, the samples were tested under three different sample conditions: drier, wetter or “as-received”. This was done because the in-situ conditions, dry, wet, of the samples may affect the measurement but are not known.
The Posidionia formation is known to have generated oil and on the Van Krevelen diagram, based on maturity and TOC, samples are located in the oil generating region of the plot. From the TGA and NMR experiments it was proven that oil is present in the shale samples, although this is identified as bound or trapped oil. Based on evaluations with NMR and GRI it was found that the sample material was dried out during storage and that the samples are likely to contain movable hydrocarbons. The SEM and NMR data suggested that some samples contain pore sizes large enough to allow oil to flow through the rocks. The sample condition is shown to be a crucial parameter for the determination of porosity and permeability. Different conditions resulted in porosity differences of up to a factor of three, for the measured sample porosity. The GRI experiment has proven the molecular sieving effect, meaning that permeability decreases if a gas is used with a larger molecule size.
The results were combined to assess the heterogeneity of the formation. based on the large spread of petrophysical properties of the samples it was found that the Posidonia shale is highly heterogeneous. Therefore it is concluded that a statement regarding the technically recoverable resources cannot be made at this stage. It is recommended to evaluate fresher sample material with the same methodology as used in this study.