Formation Testing and Evaluation in Challenging Wellbore Conditions: An East Asia Case Study

Abstract

Evaluating hydrocarbon columns, reservoir fluid types, contacts and productivity has been challenging in East Asia, especially when open hole well challenges are encountered. Initial openhole attempts are at times unsuccessful in proving significant hydrocarbon potential mainly due to severe losses, high differential pressure or bad hole conditions. The need for a new formation evaluation strategy became necessary to secure critically needed data for the prospect evaluation. The objectives, apart from establishing the presence of hydrocarbon column, is to optimise well drilling execution in a safe and timely manner. In addition to losses challenge, wells encounter hole stability issues with shale being overpressured and potential presence of H 2 S, whereby its level need to be determined onsite for completion strategy.To meet the objectives of these wells, an alternative formation testing and sampling strategy has been adapted. The reservoir fluid evaluation was postponed until the open hole was cased. The formation evaluation with Wireline Formation Tester (WFT) was performed in two stages, the first stage was to confirm the presence of cement isolation at the hydrocarbon intervals, and the 2nd stage was to perforate intervals at the zones of interest to confirm the hydrocarbon columns by downhole fluid analysis and sampling.This case study will discuss reservoir rock and fluid evaluation in cased hole with WFT. Reservoirs of interests are successfully evaluated and representative samples are successfully acquired without any operational issues. Recommended evaluation strategy and best practice supported by field data will also be presented in this paper