A Novel Combination of Friction Reducers and a Customized 2-in. CT String Design Allows TD Achievement in Iraq's Deepest Horizontal Well

Abstract After drilling the longest horizontal openhole section in Iraq (2705 m) with a final depth of 5462.5 m, the operator required coiled tubing (CT) to reach the bottom of the well and perform a customized stimulation treatment to increase and help improve well injectivity. A novel procedure to reduce drag between the well sections (cased and openhole) with CT was designed and implemented as follows: Run in hole (RIH) and position the CT at the casing shoe.Bullhead a metal-to-metal friction reducer (M2MFR) to fill the tubing-CT annulus space.RIH while pumping a rock-to-metal friction reducer (R2MFR) at a minimal rate with the well shut-in to spot the system in the openhole section. This R2MFR system consists of an acidic viscoelastic-based fluid that removes dislodged cuttings and conditions the openhole surface to reduce friction. The RIH procedure was executed per the design without the requirement for any vibrating-type extended-reach tools (ERTs), and the target depth (TD) was reached as predicted using force modeling simulations. Dual injection stimulation with 15% hydrochloric acid (HCl) and a viscoelastic acid diverter was pumped to address high permeability contrast in the openhole sections. Well injectivity increased from 8,928 BWPD at 1,620 psi to 15,408 BWPD at 25 psi. Friction coefficients were matched with the operation's real-time data and compared with previous interventions to validate the data used in the design simulation. A 42% reduction in the casedhole section (from 0.36 to 0.21) and a 61% reduction in the openhole section (from 0.46 to 0.18) were observed. How proper fluid selection and string design can improve CT reach capability in deeper wells without the use of additional tools or an increase in operator costs are discussed. TD was reached, which allowed full stimulation of the openhole section and resulted in maximum water injection into the well, the operator's primary goal.