Operational Procedures and Applications of a Wireline Formation Tester to Accurately Characterise the Gas Composition of Stacked Multiple Pools in the North Malay Basin

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAn accurate knowledge of reservoir fluid composition, specifically the concentration of hydrocarbon gases and noncombustible gases such as carbon dioxide, is a key factor in the commercial assessment of upstream gas projects at the exploration and field appraisal drilling stages, and in development planning.The precise measurement of reservoir fluid composition requires the acquisition of a representative sample of formation fluid, free of drilling fluids and other contaminants. Traditionally, Drill Stem Tests have offered the most reliable method to obtain this information. However, the cost of this method limits its application in gas accumulations comprised of multiple, stacked, separate pools where the individual reservoir fluid compositions need to be well known.Carigali Triton Operating Company Sdn. Bhd. (CTOC), Operator of Block A-18, JDA on behalf of its Shareholders, Petronas Carigali (JDA) Sdn. Bhd., Triton Oil Company of Thailand (JDA) Limited and Triton Oil Company of Thailand Inc., is now consistently able to acquire reservoir fluid samples which are confirmed by on-site advanced chromatography, and calibrated by Drill Stem Tests to be fully representative of insitu native reservoir fluid compositions. This has been achieved through the use of a wireline formation tester with an enhanced pump-out capability and a downhole fluid analyser, together with the development and implementation of key operational procedures for performing the logging operation.The accuracy and reliability of the technique has been proven and refined over the sixteen-well exploration program in Block A-18, where downhole conditions can be hostile, and tool operating time has exceeded 40 hours. This technique has enabled the Operator to obtain specific and accurate information on the fluid composition of individual reservoirs, and therefore reduce appraisal and development uncertainties, in a fraction of the time which would have been needed for conventional Drill Stem Testing, and at a fraction of the cost. This paper describes the tool, together with the techniques that have been implemented at the well site to obtain representative reservoir fluid samples in an efficient and costeffective manner. Wireline Formation Tester Drill Stem Test results from the Block A-18 exploration and appraisal program to date are compared to demonstrate the accuracy and reliability of the methods employed.