NRPs Protect Expensive Stainless Steel Casing for Wellbore Cleanouts in Harsh Geothermal Reservoir

Summary
Geothermal wells initially drilled in the1980s were facing casing corrosion and collapse due to 400°Facidic steam reservoir. Over the decades the casing design evolved from steel to titanium and then to expensive duplex stainless steel for corrosion resistance. Minerals from
the reservoir accumulates in the casing and surface pipelines, requiring wellbore cleanouts
and redrills every few years.

NRP Performance
Considering the stainless steel casing is prone to wear, Non-Rotating Protectors(NRPs) were used to reduce both conventional wear and galvanic corrosion from the steel drill pipe embedding material into the stainless steel casing which causes pitting and corrosion. After steel casing collapsed, a stainless steel casing was
run 24 years after the initial drill. 8 years after that, HT3 500 model NRPs were used to protect all drill pipe above the BHA during a cleanout run and drilling to extend the well depth. 4 years after that cleanout run, the casing passed a pressure test to satisfy a regulator to again extend the well depth. NRPs were used for a second time to protect the casing during a cleanout and reaming run with 500k drill pipe revolutions. NRPs have become a standard practice for extending casing life in the field.