| Title | Determining Porosity and Permeability in Laminated Sandstones for Combined CO2-geothermal Reservoir Utilization |
|---|---|
| Authors | Saismruti PRADHAN, Inga MOECK, Ben ROSTRON |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Thomas-Stieber method, sand fraction, porosity, laminated sandstones |
| Abstract | The utilization of hydrothermal porous reservoirs for a combined use of CO2 storage and heat extraction referred to as CO2-Plume-Geothermal requires the identification of highly porous clean sandstone beds.Recognition of clean sandstones within thin shaly beds in heterogeneous sandstones and determination of their petrophysical properties from well log measurements is a challenging problem in reservoir evaluation. Direct log interpretation values do not represent the true layer properties, but rather an average of multiple beds, resulting in significant underestimation of the reservoir quality. An interpretation methodology called the Thomas-Stieber method has been discussed here in order to better characterize thin beds and maximize reservoir potential.This method allows the identification of clean sandstone sections in heterogeneous sandstones. Clean sandstones represent generally the high-porosity sections and thus good reservoirs. The quantification of such reservoirs may also help to delineate highly productive injection zones in laminated sandstone relevant for unconventional hydrocarbon, geothermal reservoirs and as well as CO2 storage sites. The porosity and permeability thus obtained can be used to estimate the heterogeneous migration pathways and distribution of injected CO2. The same methods can also be used to identify pay zones in heterogeneous sandstones hosting hydrothermal resources. In order to estimate the productivity and injection of CO2 into these heterogeneous sandstones, it is essential to identify the volume and porosity of shale in the shaly sand units. Porosity in shaly sands varies with the amount and distribution of the clay minerals within the reservoir because the shale can be distributed through the sand in different ways, such as laminated, dispersed, structural, or any combination of these. With each of these configurations different gamma ray responses can be expected and this variable response can be used to determine the shale configuration. So, gamma ray logs and porosity logs are used to estimate the shale type and volume. Our results can thus help in the identification of target zones for CO2 injection, their efficient measurement and also in estimating stored thermal fluid in sedimentary hydrothermal resources. |