ABSTRACT

Avoiding non-productive time and reducing the well construction cost is gaining more and more importance in the industry. For example, the process of drilling deep geothermal wells is highly challenging for several reasons, and accounts for up to 70% of the total project costs. Therefore, it is essential to search for new methods to reduce the drilling costs by optimizing both the well planning and drilling operations phases.

The proposed approach to cut costs involves pre-drilling the well during early project stages. Pre-drilling can be based on existing wells that were drilled in the same region. The analysis and implementation of the existing data form the basis of evaluated critical scenarios. These critical well sections are further evaluated by re-drilling in order to optimize operating parameters and enhance the preparation of the drilling crew.

For demonstration of the proposed approach, a case study has been conducted for a geothermal well in the Hanover, Germany, region. The obtained historic data included information about the formation, drill string and bottom hole assembly, as well as operational parameters. As some parameters were missing in the data set, initial simulations were used for estimation using the built-in models of the software simulator. In addition, an identification of potential difficulties throughout the drilling phase was performed. Applying these identified problems, different scenarios were created on the software simulator for further investigations.

Based on the simulations done, it can be demonstrated that the proposed approach is a promising solution for reducing the drilling costs of future drilling projects.

INTRODUCTION

Drilling deep wells is a key technology for accessing energy from petroleum and geothermal energy resources. In geothermal projects, the drilling costs itself amount to 70% of the costs of the whole project [1]. Thus, affordable energy prices require an optimization of the entire drilling process. This can be achieved by both higher rate of penetration and lower non-productive times (NPT). While the former aspect is greatly influenced by formation characteristics and operation parameters, the latter one is largely affected from disturbances by non-optimized technical processes. NPT are of particular interest because they delay the drilling process, which increases the costs of project. Besides technical issues, the expertise and experience of the staff also have a significant effect on the duration of disturbances.

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