Research progress on low-temperature rheology of high-performance ocean deepwater drilling fluids: An overview

In deepwater drilling applications, with the change of water depth and total well depth, temperature and pressure will also change significantly. The low temperature and high pressure reservoir environment makes it difficult to control the rheology of drilling fluid. The grow of rheological parameters will increase the equivalent circulation density (ECD), even lead to gelling, serious loss of drilling fluid, and increase operating costs. The drilling fluid is seriously damaged and the operation cost is increased. Combined with high pressure and temperature drop, hydrate is easy to form during drilling. Natural gas hydrate will block the pipeline, easily lead to drilling accidents, increase the risk of lost circulation, and cause economic losses. Therefore, in the drilling design stage, it is a hot issue to develop drilling fluid and treatment agent to overcome the low temperature rheological properties and the formation of natural gas hydrate. This paper summarizes various high-performance marine deepwater drilling fluid systems and additives, evaluates the variation law of rheological properties of drilling fluid systems with temperature in low temperature and high pressure environment, and also evaluates the application effect of drilling fluid in the field. Three kinds of high performance marine deepwater drilling fluid systems represented by silicate, organic salt, and synthetic base have stable rheological properties at low temperature, which effectively inhibit the formation of hydrate. Modified bentonite and temperature sensitive polymer are introduced into drilling fluid as rheology modifier, which can significantly reduce fluid viscosity and has a good application prospect.