Pushing the Limits of Coiled Tubing to Address the Challenges of Matrix Stimulation in Multi-Lateral Extended Reach Power Water Injector

Abstract

In Middle East carbonate reservoirs, power water injector (PWI) wells are typically completed with long openhole laterals. The reservoir contact provides pressure support and enhances sweep efficiency in the low-transmissibility reservoirs. Due to the wells deviation and length, coiled tubing (CT) interventions are required to successfully enter and identify each lateral, as well as to remove formation damage by pumping the matrix stimulation treatment across entire laterals. During such CT interventions, laterals are accessed thanks to a hydraulically operated lateral identification tool (LIT), while the stimulation treatment is pumped through a ball-drop-activated high-pressure jetting nozzle (HPJN). LIT and HPJN are efficiently operated by monitoring downhole pressure values both inside and outside of the bottomhole assembly, in real time thanks to CT fiber-optic telemetry. Those downhole pressure readings further assist in optimizing the pumping rate during the job, while keeping it below the fracturing pressure. Finally, the telemetry provides support for gamma ray (GR) logging, which facilitates depth control and lateral identification. This study features a case history during which the matrix stimulation treatment was conducted in two separate CT runs for both laterals of the well. For the first run, the CT initially entered L-0 following the natural path of the well, whereas L-1 was accessed by activating the LIT. Correct lateral entry was confirmed by matching the acquired GR readings with reference logs. After successfully accessing L-1 and reaching its maximum depth, a ¾-in. ball was dropped to isolate the LIT and activate the HPJN for stimulation. During the second run, as the CT entered L-0, GR monitoring was used to confirm lateral accessibility. The stimulation treatment was pumped after reaching maximum depth and isolating the HPJN. During the stimulation of each lateral, 20% viscoelastic diverting acid was utilized for diverting from high-intake zones and 20% HCl to stimulate damaged/tight zones. This operation illustrates how downhole pressure gauge readings are used to sequentially operate the LIT efficiently and activate the HPJN, as well as to pump the matrix stimulation treatment below the fracturing pressure. Real-time GR readings, meanwhile, are used for depth control and to correctly identify laterals.