The original Mars A-14 well was drilled and completed in 1996. The well was worked over in 2000 because of a sand control failure. In 2003, the well was again shut in due to increased sand production and decreased oil production. In 2004, after slot recovery operations, the M1/M2 objectives were re-drilled.
Development drilling after years of production has become increasingly challenging because of depletion and difficult wellbore geometry. It is unavoidable to intersect both depleted and virgin pressured sands in the same interval. High mud weights required for wellbore stability coupled with a narrow Pore Pressure / Frac Gradient window elevate the risk of lost circulation, stuck pipe, and well control problems, making any sidetrack an expensive and potentially hazardous endeavor. Three sidetracks in close proximity to one another in the Gulf of Mexico in 3,000 feet of water were drilled into the same production horizons on the Mars Tension Leg Platform. Forty six drilling days were spent attempting to drill Sidetrack 1 (ST01), with 61% of that time attributed to unplanned, nonproductive activities that included wellbore instability, lost circulation, and kicks. Over 6,000 barrels of synthetic based mud were lost to formation.
Nearly 32 days were spent attempting Sidetrack 2 (ST02), with 60% of the time attributable to unplanned non-productive time; primarily fighting lost circulation and wellbore instability. Over 3,000 barrels of synthetic based mud were lost. Both Sidetracks 1 and 2 were drilled in the conventional manner. Managed Pressure Drilling (MPD) technology was employed to drill Sidetrack 3 (ST03) over a 33 day period. Seepage accounted for losses of 600 barrels of synthetic based mud. There were no recorded incidents of lost circulation, kicks, or wellbore instability that would have otherwise interrupted drilling operations. Unplanned non-productive time was less than 2%. Significant improvement in drilling efficiencies were realized utilizing Managed Pressure Drilling technologies. A direct comparison of equipment and operational technologies will be discussed.
Malloy, K.P. and Roes, V.C., “Improved Reliability of Drilling Operations Using Managed Pressure Drilling Technology: A Case Study in a Brown Field Environment,” OTC 18461, Offshore Technology Conference, Houston, Texas, April/May 2007.