Cascade: a Knowledge-Based System Supporting Shoe Depths Selection and Casing Design

Abstract

CASCADE is a decisional support system for shoe depth selection and casing design in exploration and production wells. This expert system is part of the ADIS project (Advanced Drilling Information System), jointly developed by three ENI companies : AGIP, ENIDATA, SAIPEM. The purpose of ADIS is to provide drilling engineering software tools for well planning and drilling operations support both at the office and rig site, to monitor real time operations and to diagnose drilling problems. To support real-time operations, ADIS project team developed tools for satellite communication between rigs and districts or headquarters, and expert systems to monitor operations, such as the status analyzer, on-line pressure gradients forecasts, alarms monitoring and management. The communication between different applications is provided by databases, both for the real time and the off line parts. The real time database is volatile; measurements are recorded on micrologs, which are in due time stored in the permanent, off line relational database for future use. Therefore, ADIS will provide better operations support and improved accuracy in well planning, with the ultimate aim of reducing risks and costs. CASCADE is part of the well planning tools developed for ADIS project: other software tools are related to directional well planning, hydraulics modelling, temperature prediction and gradients forecast. Casing shoe depth selection, and the consequent determination of geometrical and mechanical characteristics of casings, is a crucial activity. It heavily influences well planning and affects both safety and economical aspects of drilling operations. Accurate well and casing design can significantly reduce drilling costs and risks. Currently, casing design is carried out according to several requirements : company standards, common practice procedures, drilling engineers' experience and local regulations. Therefore, the choice of the best casing parameters which meet all the requirements and minimize cost is not a trivial task. The choice of the expert systems technology exploited for the system development is related to the following topics :(a) An expert system can combine several different skills. (b) It guarantees easy and modular expanclibility with the acquisition of new experience. (c) Moreover, new experience must be taken into account in order to continuously increase the quality of the results. (d) Available data come from many sources, and all have to be considered when choosing the shoe depths' and casing's geometrical and mechanical characteristics. (e) An expert system can explicitly represent both domain and strategical knowledge that can easily be modified, added or expunged. It can also give the user a feedback on its own behaviour, and it can also be used as a training tool. The benefits for the final user are:(a) An efficient, integrated environment providing the tools the drilling engineer needs to work with. (b) Greater accuracy. (c) Access and assessment of knowledge and procedures regarding this matter. (d) Interactive, user friendly interface.