Multistage Acid Stimulation Uses Straddle Packer, Real-Time Telemetry
Authors: Carpenter Chris 
Published: July 2023

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204830, “Multistage Acid Stimulation for ICD Screens Completion Using Straddle Packer and Real-Time Telemetry Coiled Tubing,” by Qadir Looni, SPE, Malik M. Humood, SPE, and Ahmed A. Mousa, Saudi Aramco, et al. The paper has not been peer reviewed.

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The authors describe in the complete paper how the combination of a straddle-packer system and a downhole real-time telemetry system was used to acid-stimulate up to 38 stages successfully and monitor the behavior of the straddle packer continuously during diversion of multistage acid treatment of screens while maintaining packer-seal integrity and downhole pressure. In addition, the study also provides lessons learned from implementation of multistage packers with real-time telemetry for successful diversion of acid treatment uniformly across screens in a horizontal well.

Introduction
Use of inflow control devices (ICDs) is a preferred completion technique in producing multilayer reservoirs from a single well while allowing the optimal production profile along the completed intervals by managing the drawdown from the reservoir to the wellbore. This study focuses on controlled acid treatment of a high number of ICDs in a single well.
Two options existed for achieving optimal acid placement in the subject well with 38 ICDs during treatment, chemical and mechanical diversion. Mechanical diversion is the preferred option because it ensures the most-accurate fluid diversion during stimulation. Once the methodology was confirmed, the next step was to identify the optimal bottomhole assembly (BHA) with a packer element that could be set and unset 38 times in a single coiled tubing (CT) run. The final step in the feasibility study was to obtain real-time bottomhole data to ensure adherence to operational parameters during the interventions. More specifically, a casing collar locator (CCL) reading for depth accuracy, CT downhole pressure for ensuring the packer-set value, and downhole annular pressure to check pressure differences along the packer elements were needed. This required fiber-optic (FO)-enabled CT to acquire real-time communication with downhole tools.

Methodology
The challenges associated with treatment of ICD screens using a straddle-packer system to divert the treatment mechanically include successfully locating the ICD and placing it across the straddle-packer system, monitoring the pressures inside and outside the CT to confirm the treatment affecting the targeted ICD, and not involving an already-treated ICD. In addition, when treating more than 38 ICDs in a well, maintaining the integrity of the straddle-packer elements is necessary to reduce treatment time per stage and maximize the number of stages that can be treated in a run.
Another challenging aspect of mechanically treating the ICD screen is the CT reach. A common practice to extend CT pipe reach is selection of a larger-diameter pipe, but, considering the weight capabilities of the rig crane, increasing the pipe size proved problematic.