Naylor-1 site: monitoring
The dedication of the Naylor-1 well to sub-surface monitoring makes the subsurface monitoring program extremely thorough. As carbon dioxide migrates through the storage formation, researchers will obtain an accurate picture using physical and chemical methods to predict its behaviour for the life of the project. The chemical make-up of fluids in the monitoring well (Naylor-1) will tell researchers when the carbon dioxide arrives in the depleted Naylor field.
3.965 BCF of natural gas was produced from Waarre C and A units (mainly Waarre C) through the Naylor-1 Well, which was patched and suspended in early 2004, then converted by CO2CRC into an observation well for geophysical and geochemical monitoring of CO2 from the CRC-1 injection well.
An integrated bottom-hole geochemical and
geophysical assembly was lowered into the
Naylor-1 well in a “workover completion”
operation from 25 September – 7 October
2007. The 130 foot long assembly was installed with a rigid truss and lifted with a 70 tonne crane. Eleven reels fed cables through special sheaves which were manually tied to ¾” sucker rods. Well control was maintained throughout by topping the well up with 2% KCl brine.
The integrated bottom-hole assembly (pictured top-right) is an integrated system for:
- geochemical fluid sampling to detect presence of CO2 and monitor injected tracers using three sets of U-tubes;
- continuous pressure and temperature measurements with the P/T gauges;
- continuous monitoring for microseismic events with an array of triaxial geophones;
- discrete High Resolution Travel Time Resolution (HRTT) measurements across the gas water contact (GWC), and
- Vertical Seismic Profiling (VSP) imaging from an array of geophones/hydrophones
Naylor-1 bottom-hole assembly
The system design includes:
- seventeen geophones and three hydrophones
- three geophones and three hydrophones below the packer in the Waarre C Formation
- three component geophones above the packer; and
- an array of eight single component geophones above these
- three U-tubes for geochemical sampling - one in each of the following zones: in the gas; below the gas-water contact (GWC) and in the water zone.
- two pressure/temperature guages below the packer in the Waarre C Formation
Downhole fluid sampling
High quality well bore fluid and gas samples were collected at reservoir pressure from multiple levels to detect the CO2 arrival at Naylor-1 and to characterise chemical changes associated with the CO2 arrival. Samples are analysed in laboratory for their chemical and isotopic composition.
During injection, the CO2 migrated from CRC-1 to accumulate below the residual methane cap at the Naylor-1 well pushing the gas-water contact (GWC) down. The U-tube system, developed by Lawrence Berkeley National Laboratory (LBNL) and the CO2CRC, makes it possible to sample the deep groundwater.