Drilling with Liner Technology Enables Successful Sidetrack through Depleted Sands in Shallow Water Gulf of Mexico

Abstract

Abstract The maturation of fields in the Gulf of Mexico shelf means that many future sidetracks and recompletions will require drilling through depleted formations. The difficulty of drilling through such formations is especially high when adjoining zones are over-pressured since the mud weight required to maintain overbalance creates significant risk of differential sticking and lost circulation in the depleted zone. Three dump waterflood wells drilled conventionally in 2012 encountered significant problems while drilling the depleted zones. These included lost returns while cementing, hole pack-off and in one case, differential sticking which required the drill string to be severed and a sidetrack to be performed. The three wells incurred an average of 258 hours of associated NPT, which negatively affected project economics and led the operator to evaluate other drilling methods for such depleted sections. Following a detailed and collaborative planning process between the operator and an integrated service provider, it wasdecided to sidetrack an existing well and use drilling with liner (DwL) method to drill through two depleted sandstone intervals bounded by over-pressured shale zones and cement the liner to facilitate the completion of a dump flood well. There were no observed losses while drilling the entire 577 ft. interval, and also during the cement job with the liner lap testing successfully. An additional benefit was the exceptionally low formation damage observed during the subsequent frac-pack completion as compared to the previous wells. Overall, this operation suggests that DwL is an enabling technology for drilling depleted sands. In this paper the authors will describe the planning process in detail and will continue to describe how drilling with liner technology was successfully implemented to drill a sequence of depleted sands and over-pressured shale formations in a field where conventional drilling had presented many problems.