Integration of Downhole Fluid Analysis and Advanced Mud Gas Logging Reduces Uncertainty in Reservoir Evaluation

Abstract

Abstract Reservoir fluid characterization is crucial for the success of field exploration and development phases. Early detection of hydrocarbon allows accurate determination of reservoir fluid properties and plays a key role in reducing uncertainty in reservoir evaluation and future field development strategies. Advanced Mud Gas logging (AMG) system and wireline downhole fluid analysis are among the important means available in the oil and gas industry for such analyses. Each method has its limitations and advantages, therefore developing an integrated approach and workflow that combine these two different methods are important for the success of fluid sampling and for better reservoir characterization. The aim of this integration work is to improve reservoir fluid evaluation during the entire well starting from the early stage of drilling. This can be done by having reliable early hydrocarbon detection from mud logging which allows optimizing formation PVT sampling program, and helps to develop correlations for the benefit of fluid evaluation in future wells. This work presents a successful integration of mud logging and downhole formation fluid analysis for better reservoir fluid characterization in an offshore Malaysia field. Advanced Mud Gas logging was run to provide early formation fluid evaluation, which was utilized to design and optimize formation fluid sampling, PVT lab work and further DST requirement. By using AMG, it was possible to identify the significant changes observed on fluid composition (C1-C5, C6-C8 range) and also to distinguish potentially fine variations within the possibly same fluid type. Based on these results detailed fluid evaluations and sampling points were suggested. In addition several potential hydrocarbon/water contacts were identified. Wireline formation tester (WFT) was also run for downhole fluid identification (DFA) and to acquire representative fluid samples in addition to reservoir pressure and fluid mobility. This paper also presents strategies used for fluid analysis and sampling to provide accurate fluid characterization in a challenging environment. The methodology, workflow, analysis, and applications of this field study are presented in this work. Introduction Accurate measurement and evaluation of reservoir fluid properties become ever more complex especially in challenging drilling environments coupled with complex reservoir formations. Various methods are available nowadays for reservoir fluid characterization but each method has its own limitations and advantages. Therefore the advance in individual technologies alone may not provide a complete answer to the formation fluid evaluation task. To reduce this uncertainty and improve reservoir fluid evaluation, an integrated approach that combines various methods such as Advanced Mug Gas Logging (AMG), wireline Downhole Fluid Analysis (DFA) and PVT lab analysis is developed. These measurements can complement one other. This approach is based on early continuous detection of reservoir fluid type at surface from mud logging combined with fluid properties measurements under downhole conditions at a specific depth in order to provide comprehensive fluid properties that address the reservoir fluid characterization requirements.