Laminated formations especially in muddyenvironment during deposition time are known to be very challenging in terms ofreservoir characterization and evaluation. Alternation of thin sand and mudlayers in these types of rocks imposes natural anisotropy in the distribution ofreservoir properties like porosity and permeability. This anisotropy has beenproved to be a major control on fluid flow within the reservoir which is ofparamount importance to understand and consider in reservoir developmentplanning. The aim of this work is to integrate geological information derivedfrom borehole images into interval pressure transient test (IPTT)interpretation to analyze and explain the complex flow behavior due to thecombination of formation dipping and thin laminations.A wireline formation tester dual packer module wasutilized in two offshore exploration wells to conduct an IPTT/miniDST indifferent formations including laminated muddy and sandy heterolithic formations. Several build up tests were performed to obtain valid reservoir pressure andpermeability values. A good consistency was observed in the log-log diagnosticplot from these build up tests and the pressure derivative behavior suggestsmultiple possible reservoir scenarios in this complicated geological setting. Adetailed study on borehole images and 3D near-wellbore geological modelrevealed the effects of slanted wellbore, laminated formation, highly orientedand dipping beds on the travel of pressure transient away from wellbore. Withthis geological information, a most representative reservoir model was able tobe constructed to match the IPTT data to acquire the required reservoirparameters. This paper highlights the main challenges offormation characterization in laminated muddy and sandy heterolithicformations. Special emphasis was given to resolve significant problems encounteredin pressure transient test interpretation in highly deviated wells. Slantedwellbore sections are typical in Malaysia's offshore fields as the wells aredrilled from offshore platform to intercept the formation at different angles, hence the pay zone and other petrophysical parameters are usuallyunderestimated. Attempts are made to identify and classify these challenges, and recommendations are provided toward better resolution duringinterpretation.