Tempress'Mechanically-Assisted Jet Drilling project involves the development of a downhole intensifier (DHI) to boost the hydraulic pressure available in conventional coiled tubing to the level required for high-pressure jet erosion of rock. A review of high-pressure jet drilling and mechanically-assisted jet drilling was carried out to define the bottomhole assembly configuration and DHI performance specifications for coiled tubing drilling applications. Two BHA configurations were evaluated (1) mechanically-assisted jet drilling with the DHI deployed below a PDM drill motor and (2) high-pressure jet drilling with the DHI deployed upstream of a high-pressure jet drill. A hydraulic model of the DHI was coupled with a coiled tubing drilling circulation model to determine pressure and power available for jetting. Data on jet erosion of oil and gas producing formations and jet-assisted drilling was then applied to predict drilling rates. Other factors considered include steering, dogleg severity, extended reach, hole cleaning and coiled tubing pressure. The PDM will require heavy-duty bearings and a custom high-pressure seal. The drill motor/DHI combination BHA would be also be longer than a conventional motor BHA, which would limit application to long-radius well curves. The DHI/jet drill combination would be much shorter than a conventional motor and would allow high speed drilling through short radius build sections. This configuration also minimizes mechanical loads and vibrations on the BHA. Tempress will provide a DHI, a modified PDM, a mechanically-assisted jet bit and a high-pressure rotary jet drill for the project.