Multistage Acid Stimulation for ICD Screens Completion Using Straddle Packer and Real-Time Telemetry Coil Tubing

Inflow Control Devices (ICD) (Fig. 1) is a part of the well completion to help optimizing the production by equalizing the reservoir inflow. Multiple ICD can be installed in the completion at a long section, as each ICD going to partially choke the flow. Completing wells with ICD is one of the most common techniques that is used to maintain uniform production across multi-layer reservoirs. One of the challenges in such completions is to achieve a uniform matrix acid stimulation across these screens due to well deviation and length of the screens. In most cases an effective diversion method is required during acid treatment to ensure all the screens are treated uniformly for maintaining homogeneous production across the reservoir. Over the time, wells with ICD screens show decline in production due to plugged screens which necessitates immediate action. In most cases remedy is to acid treat all ICD screens on individual basis using straddle packer System and real-time telemetry coil system due to requirements of diversion method, criticality of the packer setting depth and downhole pressure monitoring. Multistage acid stimulation for ICD screens is achieved using straddle packer's system with real-time telemetry coiled tubing (CT). The real-time telemetry coil system ensures depth accuracy – as each ICD port length is not more than couple of inches – and monitoring of pressures and straddle packer system's integrity during multistage acid stimulation across the horizontal screens. This operation involves challenges of properly setting the packer to selectively treat each ICD screen by mechanically diverting the acid treatment while maintaining seal integrity in each stage and re-using it multiple times. After drifting and wellbore conditioning run, the multi-set straddle packer system is deployed on real-time telemetry coil (fiber-optic enabled) for multistage acid treatment. Starting from total depth, the real-time CCL readings are utilized successfully to identify the first screens joint allowing the packer system to be stationed across the required screen. The packer elements are then energized to divert the acid treatment fluid into the targeted screen Thru the coil and exiting from per adjusted nozzles between the Packers; this diversion is confirmed by monitoring bottom hole pressure inside and outside the coil tubing string. Upon completion of the acid treatment of the ICD screens the tension-compression sub of telemetry coil system confirmed the elements is de-energized to make safe to move the packer without damaging the elements. The treatment is then successfully repeated across the remaining ICD screens with positive indication of diversion across each ICD screen. This study illustrates how the combination of the straddle packer System and downhole real-time telemetry system was utilized to successfully acid stimulate up to 38 stages and monitor the behavior of straddle packer continuously during diversion of multistage acid treatment of screens while maintaining packers seal integrity and downhole pressures. In addition, the study also provides lessons learned from implementation of multi-stages packers with real-time telemetry for successful diversion of acid treatment uniformly across the screens in horizontal well.

Design and Analysis of CFETR CS Coil and Pretension Structure

The coil and the pretension rod play important roles in the central solenoidal coil system of Tokamak. Therefore, the analysis of the coil and the pretension rod in the normal operating environment is essential for the facility’s construction. In this paper, the 3D model of the two parts mentioned above is built based on SolidWorks. Subsequently, the simulations are carried out to revert the real operation environments following the fields, loads, and boundary conditions. Then, we compare the official analysis results of the corresponding parts in the central solenoidal system of the China Fusion Engineering Test Reactor (CFETR) based on the results from COMSOL. Compared with the official analysis, the error is about 1.3% for the maximum magnetic field and about 0.53% error for the outer part, respectively. As for the pretension rod, simulations are carried out based on the finite element analysis software ABAQUS. The Von mises and the maximum principal stress are 140.1 MPa and 168.4 MPa, which is much lower than the material’s yield stress (205 MPa). The safety factor is 1.78, larger than the critical failure value 1. According to our results, the rationality of the CFETR central solenoidal coil system design is re-examined and verified.