Best Practices Acquired in Ecuador, to Complete Horizontal Wells with Low Formation Pressure
Authors: Proaño A. , Aponte J. , Duque G. , Portales G. , Quinde B. 
Published: April 2024

This paper aims to present the best practices acquired in Ecuador, Orient Basin, from 2016 until 2023, during the completion of 25 horizontal wells with low reservoir formation pressure and an average of 1,000 feet of horizontal section. This analysis covers three main risks identified during completion activities: wellbore instability during calibration trip and run-in-hole slotted Liner, formation damage, and mechanical properties of slotted Liner machined from original tubing.

Regarding wellbore stability, geomechanics has been established as input to determine the limits during calibration tripping and running slotted Liner. The limits recommended in this study are relating to maximum allowable pressure, maximum flow rate, and maximum velocity of tripping in and out, according to maintaining equivalent circulating density (ECD) in a safety margin.

To minimize the formation damage, compatibility tests between the completion fluid and reservoir fluid were performed. Concerning the breakdown pill, the study presents how it acts over mud cake to get dissolve it. To determine the mechanical properties of the slotted Liner, destructive tests were conducted to determine the maximum resistance to tension, compression, and torsion.

Wellbore instability is analyzed considering pore pressure, lithology changes, and induced fracturing. In addition, formation collapse, sand flow, and unwanted communication with neighboring wells can cause operational problems and affect production. Proper geomechanics evaluation and proper design are essential to mitigate these risks.

To minimize formation damage, this paper establishes the best practices applied in compatibility tests of completion fluid between reservoir fluid, permeability returns, thermal stability, and emulsion formation. Regarding breakdown pumping and action, it shows the considerations to take in calculations, flow regime, and how the breakdown acts over mud cake to get dissolve it.

The mechanical properties for the slotted tubular showed up to an 80 percent reduction in torque, 36 percent for collapse, 14 percent for tension limits and 5 percent for tension limits when compared with the original tubular. The calculated properties were then uploaded on specialized torque-drag and tubing design software where the new limits for run-in-hole and the lower completion were defined. Having the new limits is essential to adjusting tripping speed, picking-up and slack-off limits, and torque & rotation parameters during the execution phase.

Horizontal completions present various risks that demand careful consideration. Wellbore instability, including differential sticking and collapse, may compromise completion progress and result in costly interventions. Excessive frictional forces could lead to issues during tripping in of slotted Liner. This paper aims to establish a guideline during the completion of horizontal wells that could help to engineering and operation team, to anticipate the risks and elaborate a systematic plan considering the different options in front of variation during the execution phase.

In the last two decades Ecuador has been a hotspot location for infill wells. The reservoirs that have been producing since the 1970's now have significantly reduced their formation pressure to near (or below) dew point. In order to improve the recovery factor of these depleted wells, ESP systems were introduced in the basin.

Five years ago, a field operator determined the potential to increase the recovery factor by drilling horizontal infill wells in the lower U and lower T sandstones reservoirs. The horizontal drilling campaign included drilling and complete 5 horizontal wells in the first year, and based on the operations and production results the campaign would be continued for 21 more wells. From a well construction point of view an integrated solution was implemented to tackle the multiple challenges that the drilling and completion operations represented.

Referring to the well completion operation, the operator was aware that previous horizontal campaigns in offset fields showed poor results, associated with the horizontal navigation in the sandstone and the high tortuous trajectories that did not allow the lower completion reach bottom. Off-bottom lower completion equipment represented a constrain to the production of the entire horizontal section. Just in the last two decades success a total of 9 horizontal wells were completed in the basin, from which 3 had major issues installing the completion and another 5 had certain kind of restriction.

This manuscript will focus on the integrated well construction strategy that helped the field operator to perform a proper technical risk management and resulted in the successful completion of 26 horizontal wells during the last 6 years, adding an extra 30% of oil production for the field.