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

Reservoir fluid characterisation in cased-hole is often challenging especially in thinly laminated and low permeability formations. Obtaining representative reservoir fluid samples is an important step in verifying fluid type and properties in addition to reserves booking requirements. Downhole fluid analysis (DFA) provides critical information on early confirmation of fluid type, while samples are used in the lab to provide PVT and physical properties of the reservoir fluid. There are two (2) main ways to obtain fluid samples in cased-hole environment: either through subsurface sampling via wireline downhole sampling tool (WFT) or surface sampling via well testing full term (DST). Depending on the test objective, each method has its pros and cons. Subsurface sampling is normally performed in open hole. However, wellbore conditions and formation characteristics sometimes prohibit logging in open hole, hence sampling can only be performed in cased-hole. This also applies to wells which had been cased earlier than expected due to operational constraints. Conventional DST in cased-hole can be prohibitive due to many factors including cost especially if multiple layers have to be tested, not to mention environmental concerns restricting flaring. This work depicts the successful fluid sampling strategy based on case studies in East Asia reservoirs. The paper will also discuss a proposed best practice that is supported by field data.