Reservoir Permeability from Wireline Formation Testers

Abstract

Abstract Permeability is an essential parameter in order to properly define well and reservoir performance. Permeability is also relevant in overall reservoir management and development, including reservoir simulation, gravity drainage, flood performance, assessment of gas or water coning. Attempts to derive reservoir permeability with wireline formation testers started in the 70s, calculating drawdown mobility from pretests taken with a single probe. However, despite drawdown mobility provides valuable information about reservoir behavior, it is not comparable to reservoir permeability traditionally measured with Drill Stem Tests (DST). This is due to its limited depth of investigation, the upscaling difficulties and the fact that probe type tools do not develop a complete radial flow regime. In the 90s the introduction of the latest generation of wireline formation testers, equipped with straddle packer modules able to develop radial flow with radius of investigation in the order of tens of meters, enabled measurement of permeability at reservoir scale. These tests, called miniDST or IPTT (Interval Pressure Transient Testing), represent in some cases a valid alternative to conventional DST tests, especially for the environmental, safety and the economic aspects. MiniDST/IPTT method is here described, from the design phase, very important in order to obtain a reliable test, to final interpretation, with a critical review of the method applicability, its limitations and comparison versus traditional DST. Latest developments in terms of hardware and interpretation techniques are included. Case histories are also provided in order to demonstrate the IPTT application, its integration with the other permeability sources and the reservoir model, including comparison between simulated reservoir deliverability and measured well test rates.