Sediment-petrographical analysis of the Delft Sandstone

Abstract

The Delft Geothermal Project is an ongoing study in search for the best way to produce renewable energy from the Delft Sandstone Member. So far, a homogeneous reservoir model, a study of the regional geology and a study of the fluid flow and heat transfer have been made. For these studies, information is used from the Moerkapelle oil field located twelve kilometers to the east of Delft. Because of the oil production there, a wealth of subsurface data is available. This thesis used for the first time borehole cuttings data from the well DEL-03. DEL-03 is less then one kilometer away from the proposed drill site. The aim of this thesis is to discover vertical heterogeneity within the Delft Sandstone Member with a sediment-petrographical analysis. With the use of thin slides of the cuttings of DEL-03 a sedimentary analysis has been made using a polarizing microscope. It goes more deeply into mineralogical content and cement types. Examination of the cuttings with fluorescent light and chloroform proved the absence of residual bitumen, which is a needed for the production of hot water. Also a grain size analysis has been made which was inconclusive. The content of sandstone in the borehole cuttings analysis does not correspond with the results of the spontaneous potential log of DEL-03. Siderite present as cement in these sections is the cause of this contradiction. The siderite cement has a high influence on the porosity and permeability which is also concluded in the petrographical study of thin slides of plugs of MKP-11. Porosity is detected with the use of the software Image Analysis while the permeability is calculated with the Karman-Kozeny equation. The porosities in the upper part of the Delft Sandstone Member beneath Moerkapelle showed relatively high values and therefore a relative high permeability. The results of this thesis can be used, together with the many images gathered, as a database for a heterogeneous reservoir model.