The Tian Mountain Front Block in North Border of Tarim Basin is very complicated, such as ultra-thick composite gypsum-salt formation, high pressured brine layer, ultra-high temperature hydrocarbon zone, fragmented formation widely distributed in this Block, and narrow mud density window, so abnormal high pressure formations and high collapse stress formations are widely distributed in the Tian Mountain Front Block, which brings enormous challenge to drilling engineering.
Traditionally the oil-gas wells in this area are drilled using high-density water-based drilling fluids (WBM), however, significant non-productive time (NPT) and low rate of penetration (ROP) are easily encountered in dealing with borehole instability, stuck pipe, high pressured brine influx and downhole losses in the process of drilling the gypsum-salt formations or fractured pay zones. To meet the need of drilling operation in the Tian Mountain Front Block, a kind of high-temperature high-density non-aqueous fluids (NAF) is used in drilling engineering. So far, NAF system has been recommended to run for 56 wells in this Block, achieving quite good results.
Ultra-high density NAF system (>2.50 g/cm3) as well as corresponding well killing fluid (up to 2.85 g/cm3) has been developed, and successfully applied to drill through the gypsum-salt formations of six wells in KES 9 Block, and wellbore stability as well as regular hole diameter could be achieved.
This paper presents a study on the successful application of NAF in the Tian Mountain Front Block, and evaluates the potential technical benefits that this NAF technology might provide to petroleum development and production.