Analysis of drill stem testing technology of the Malm carbonate rocks of the Carpathian Foothills, in the aspect of geological research and exploration decisions

Abstract

1. InTRoDUcTIonThe credibility of drill stem tests results performed with DST tools depends largely on the technology used. The Polish Oil and Gas Company most commonly use double-cycle drill stem tests, which, in the case of inflow to DST tool oil or reservoir water, enable among others the evaluation of [1, 2]:‒ changes of permeability of reservoir rocks in closer and more distant parts of the near-wellbore area test with DST,‒ change of yield index in the first and in the second sampling cycle,‒ relieving the given horizon of reservoir rocks from the repression of the column of the drilling mud.In the case of natural gas inflow to DST and mud spacer self-acting outflow from DST column, the technology of drill stem test changes from double-cycle to multi-cycle with clas-sical open flow operation. Thanks to open the flow operation, it is possible to remove the mud from bottom hole and declogging the near-wellbore area rocks.The Baker Inflatable type tool allows us to perform selective reservoir test, mostly in open hole sections of boreholes but also in the case of large caverns in borehole walls [1]. Then the inflow of reservoir fluid is from a predetermined interval of wellbore. This allows to shutoff the inflow of bottom water to the DST tool and reduces forming the water cone.