Located in West Texas, the Yates field was discovered in 1926 and is one of the largest oil reservoirs in the United States. Its shallow reserves have been accessed mostly with vertical wells but, over the last few years, implementation of a horizontal well program has significantly affected the overall production performance of the field. The reservoir energy of the field is maintained by Nitrogen (N2) injection into the gas cap and field-produced water injection below the oil leg. Low reservoir pressure and highly productive rock in both the gas cap and the water zone present challenges to drilling operations whether underbalanced or conventional. These conditions caused wells drilled previously by conventional methods to incur severe lost circulation upon encountering a fracture system. This resulted in premature suspension of drilling operations and a consequent failure to achieve the desired lateral lengths.
