Improvements of Sampling and Pressure Measurements with a New Wireline Formation Tester Module in Carbonate Reservoirs

A multilayer hydrocarbon reservoir in Abu Dhabi land is in an appraisal stage before experiencing an extensive field production operation. The hydrocarbon reservoir, having medium to low permeabilities, consists of a number of carbonate layers with their associated oil-water contacts. One of the challenges is to sample hydrocarbons in tighter layers as well as to measure valid reservoir pressures to determine oil-water contacts. While the goal is to accomplish the objectives with wireline formation testers (WFT) in openhole conditions, stationary times during logging are limited due to wellbore conditions. The time limit has been a longstanding challenge in the layers having especially lower permeabilities (<1md). A typical sampling operation involves advanced modules of WFT including a Dual-Packer and an Insitu Fluid Analyzer to identify fluid types and provide downhole compositions with densities. Reservoir pressures are measured generally with Single-Probe modules. The new WFT inlet module is introduced first time in Abu Dhabi across the carbonate formations to accelerate the stationary operations. The new inlet module showed an improvement over a Dual-Packer and a Single-Probe modules in several aspects: (1) Stationary times during sampling are reduced due to very low interval volumes in comparison to a Dual-Packer module and up to 60% faster oil breakthrough times are achieved. (2) Tight zone pressures are measured as fast as a Single-Probe module with lower supercharging effects. (3) Set and retract times are shortened so that a new sampling method of a set-retract-reset is developed without exceeding stationary times. This paper summarizes the recent achievements by reducing risks associated with long stationary times. The field benefits are demonstrated in two separate WFT operations by comparing data qualities and job efficiencies in the same reservoir layers. Results show faster sampling, more accurate pressure and permeability measurements in the carbonate reservoir.