In the Unconventional Loma Campana Oil Field, located in Neuquen, Argentina, the primary target is the Vaca Muerta shale, and the secondary target is the Quintuco carbonate. Both formations are naturally fractured and present high formation pressures and a narrow mud weight operating window. Those conditions generate operational issues (influx or fluid losses) and are the primary reason for the use of the Under Balanced Drilling (UBD) technology through problematic zones.When using conventional BHA for UBD operations, after reaching TD, it is necessary to kill the well, by increasing mud weight, in order to pull out of hole and run the casing. This heavier mud exerts high ECD during the cement job causing partial or total loses of returns. In other cases, when the formation pressures are too high to be controlled with the mud weight, it is necessary to unload the well until reservoir pressure decreases to the manageable level. This operation has high impact on both time and cost of the well.By the use of the casing drilling technology and with the knowledge of the operating window it is possible to perform managed pressure cementing (MPC). This is done by exerting back pressure needed to adjust the ECD within the operating window detected in the region of interest for each stage of the operation. With this technique there is no need to kill the well. The main goal, to reach the desired height of cement, is achieved by minimizing fluid losses and controlling influxes.This paper contains information that will help develop cementing fluid design, pump schedule, and required back pressure in each stage of cementing job.
OBJECTIVES At a time when the demand for energy is growing in Argentina, operators are seeking to improve the profitability of unconventional oilfields by drilling wells with longer lateral lengths (up to 3200 meter), allowing a larger area to be drained by single wellbore, minimizing overall development cost. This paper outlines methods and resources used to drill this long lateral well along with the limitations that arose during the planning and execution phase. METHODS, PROCEDURES, PROCESES Currently the development of the unconventional oilfield in the Loma Campana and El Orejano oil areas are established with wellbore design of 3 casing strings, drilling the production zone (Vaca Muerta) in an open hole of 6-1/8" and completing it with 5" casing; achieving horizontal lengths between 2400 m to 2600 m with a maximum of 2715 m. The current configuration of these types of wells is in a technical limit stage, due to the maximum hydraulic power that the available drilling equipment possesses and the loss of efficiency with its consequent increase in costs in the completion stage. It is for this reason and looking to increase the number of fracture stages per well, that the construction of a well of robust architecture and greater extension was considered. RESULTS, OBSERVATIONS, CONCLUSIONS The design change contemplated 3 casing of higher diameters 13 3/8," 9 5/8" and production section in 5 ½". This design requires drilling production open hole section in 8-½" diameter. This allowed to increase the lateral length to 3200 m, avoided reaching the hydraulic power limit of the drilling equipment and maintained the same design of stimulation while preserving the efficiency. ADITIONAL INFORMATION The presentation of the paper consists of the technical feasibility analysis, contemplating the uncertainties regarding drilling fluid hydraulic behavior, torque & drag, the operational results of the experience, and the resulting cost analysis.
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