A team from Sandia and Brookhaven National Labs is evaluating high temperature cements for the DOE Geothermal Technologies Office. work focuses on development/modification of a test system to measure dimensional changes and fluid flow on cements at elevated temperature and pressure. Our geothermal environment goals are limited to temperatures of >250C and confining pressure and pore water pressures of 40 MPa by the test system.
The lab-based system includes a pressure vessel, servo controlled axial pistons, and servo-controlled flow through pore water system. Cylindrical test samples are 7.5cm in diameter and 17cm in length. Lead jackets are sealed to pistons with knife edge seals. Displacement measurements are made in the vessel using high temperature gages; pressures and forces are measured outside the pressure vessel.
We are studying two test assembly types, solid cement and a steel cylinder sheathed with cement. Using the first assembly type, estimates of cement permeability are made. In the latter sample type, we flowed water through the inside of the steel cylinder rapidly to develop an inner to outer thermal gradient on this test geometry. A critical parameter for the well integrity in geothermal storage and production wells subjected to frequent thermal cycling is the interface between metal casing and cement composite. We will present/discuss our experimental method development and early results.