Reservoir quality evaluation using sedimentological and petrophysical characterization of deep-water turbidites: A case study of Tariki Sandstone Member, Taranaki Basin, New Zealand

Abstract

The current study aims to ascertain the reservoir characteristics of the Tariki Sandstone Member of the Otaraoa Formation, Taranaki Basin, New Zealand. This study was carried out by integrating the comprehensive petrophysical evaluation, sedimentological and petrographic studies, as well as well log analysis by using data from six wells. The porosity-permeability relationship is used to divide the samples of the Tariki Sandstone Member into reservoir and non-reservoir facies. A thorough petrophysical analysis shows that the maximum porosity values fluctuate between 16.6% and 22.1%, while permeability ranges from 102 mD to 574 mD, which indicates fair to good reservoir quality. Moreover, the Tariki sandstone represents six hydraulic flow units with a high reservoir quality index and flow zone indicator representing good reservoir characteristics. The pore size varies between nano and megapores with dominant macropores. Based on the sedimentological and petrographic analysis, the Tariki Sandstone Member is classified as a combination of subarkose, arkose, and lithic arkose with fine to medium and moderately to moderately well-sorted grains. The main diagenetic factor affecting the reservoir quality is cementation, which occupied all the pores with calcite. On the bright side, the secondary pores are developed due to the dissolution of calcite cement and few grains. The well log analysis demonstrates the presence of low clay volume ranging from 0.3% to 3.1%, fair to good effective porosity values between 13.6% and 15.9%, net pay thickness from 18.29 m to 91.44 m, and hydrocarbon saturation from 56% to 77.9%. The findings from this study revealed that the Tariki Sandstone Member possesses fair to good reservoir quality and hydrocarbon potential, which indicate submarine fans as appealing hydrocarbon reservoirs. This study can be used in similar depositional environments elsewhere in the world.