The oil-gas exploitation techniques of the piedmont tectonic formation of Tarim Basin are facing a great challenge. Due to the ultra-high temperature (up to 180 °C), high pressure (mud weight up to 2.6 s.g.), ultra-thick composite gypsum-salt formations (thickness up to 4137 m), high pressure brine layer, significant non-productive time (NPT) and low rate of penetration (ROP) are encountered in dealing with borehole instability, stuck pipe, high pressure brine influx and downhole losses. To meet the need of drilling operation in the piedmont tectonic formation, a kind of high-temperature high density oil-based drilling fluid system known as UDM-2 drilling fluid system is developed.

UDM-2 drilling fluid system has excellent comprehensive properties, and it could resolve the contradiction between safety drilling of complicated deep wells and formation complexity. UDM-2 drilling fluid system has been recommended to run for about 60 wells in this block, resulting in very good results.

Three sets of plugging technology for oil-based drilling fluids are applied successfully in the gypsum-salt formations or pay zones, and the total volume of loss of UDM-2 drilling fluids to the formation is significantly reduced from the beginning of the project, so the drilling time and cost can be saved remarkably.

The large-scale application of UDM-2 drilling fluid technology has brought great economic and social benefits, and provides a strong technical support for efficient production and development of upper-deep oil and gas resources in Tarim Basin.

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