Development of Well Complexity Index to Improve Risk and Cost Assessments of Oil and Gas Wells

摘要

The Well Complexity Index (WCI) is composed of Drilling Complexity Index (DCI) and Planning Complexity Index (PCI). The DCI addresses mainly subsurface challenges encountered during drilling operations (including those related to drilling rigs, equipment, weather, etc.). The PCI addresses surface challenges such as logistics, geopolitics, environments, and climate. Wintershall has developed a Drilling Complexity Index and a Planning Complexity Index, which are simple systems used to rate the complexity of well planning and operations during the project evaluation and gated planning phases; from the conceptual or pre-screening phase through the detailed design phase to the execution phase. The development & evaluation of Wintershall's Well Complexity involved the following tasks: 1. Definition and ranking of factors that influence a well's complexity, splitting them in surface and sub-surface factors. 2. Development of a simple method(s) to measure the planning complexity of a well; also called planning complexity index. The planning complexity index is a single value that represents the complexity of planning the well. 3. Development of simple method(s) to measure the drilling complexity of a well; also called drilling complexity index. The drilling complexity index is a single value that represents the complexity for drilling the well. 4. Testing and calibrating of both numbers for different well types (exploration, appraisal and development) in various project phases and countries and comparison of the results. 5. Comparison of Wintershall well complexity to other publicly available complexity indices and verification of the validity via an independent outside contractor. 6. Using Wintershall well complexity tool to compare wells independently of the trajectory, type, geographical location, pressure, geology, etc. 7. Comparing Wintershall Drilling Complexity Index tool to Rushmore's RDI and Dodson's MRI. Both numbers represent early warning indicators that are often based on limited information. They can be used in the risk management process to identify potential risks and areas of concerns. Human and financial resources can also be allocated accordingly; based on the complexity of the drilling project.