A robust methodology to select the best lost circulation treatment using decision tree analysis

Abstract

Lost circulation is a unique challenge unlike other factors contributing to non-productive time (NPT). Due to the variability in the nature and type of lost circulation prone formations, there is no universal solution to this challenge. This publication presents a new approach to guide the decision-making process of which and when to apply a certain treatment as compared to another. If implemented correctly, a significant reduction in NPT related to lost circulation can be expected. In addition, the examination of the cost of each treatment and the NPT was conducted. Lost circulation events for three carbonate formations which are the Dammam (dolomite), Hartha (limestone), and Shuaiba (limestone) were gathered from over 1000 wells. The treatments were categorized based on the type of loss, cost, and type of formations. This work uses decision tree analysis (DTA) and expected monetary value (EMV) in the decision-making process. Thousands of treatment scenarios were considered to treat partial, severe, and complete losses. Two criteria were utilized to choose the treatment strategies for each type of loss. The first criterion is that the treatment strategy has to have the lowest EMV, and the second criterion is the treatment strategy has to be practically applicable in the field. Both criteria have to be met in order to choose the treatment strategy. All treatment strategies end up with liner hanger if the lost circulation did not stop after applying all treatments. Moreover, this study provides comprehensive treatment strategies to handle lost circulation in three carbonate formations to assist the drilling personnel to deal with lost circulation efficiently and cost-effectively. This study provides a new method to select the best lost circulation treatment strategy for each type of loss and three carbonate formations. Due to the inconsistency of methods to respond to the lost circulation problem, this study can serve a reference to handle lost circulation in any formation worldwide.