Cased wellbore tools for sampling and in situ testing of cement/formation flow properties

Collecting data that help to quantify potential CO2 leakage rates along abandoned wellbores is important for feasibility assessment of long-term storage of CO2 in geological formations. A field testing program was developed to investigate wellbore integrity as a component of the International Energy Agency Green House Gas Weyburn–Midale CO2 Monitoring and Storage Project. In support of this program, two downhole tools were designed and built: a pressure transient test (PTT) tool and a cement coring (CemCore) Tool. Site conditions required these tools to be operable in a 139.7 mm (5.5 in.) diameter cased borehole up to depths of 1450 m (4757 ft).The PTT tool is designed to seal two pseudo slots vertically offset by 1.45–3.68 m (57–145 in.), then to apply a user-controlled pressure to the upper slot while monitoring pressure responses at the lower slot. The two pseudo slots are created by penetrating through the casing and cement with an existing controlled perforation drilling tool. The final tool design consisted of four packers with maximal differential pressure rating of 6894 kPa (1000 psi), internal pressure and temperature sensors, and pulse injection and receiving ports. These elements are all monitored/controlled from surface and deployed on coiled tubing. The data generated using the PTT tool can be used to interpret vertical permeability of the near-well area and, most importantly, the cement sheath and its interface with casing and rock formation.The CemCore tool was developed based on an existing controlled perforation tool by adapting a cement core barrel to fit on the end of the tool's flexible drill shaft, which thus increases the radius of the tool's parallel to perpendicular transition zone. The tool was used successfully to cut 9.5 mm (3/8 in.) diameter samples that were 10.3 mm (13/32 in.) in length. In the field program the PTT tool was deployed three times with one successful test result and the CemCore tool was deployed five times with four successful core retrievals.

► Two tools were built and deployed for the Weyburn CO2-EOR project.
► One tool for measuring cement permeability behind wellbore casing.
► One tool for sampling the cement behind the casing.
► The engineering work to build the tools is presented.