Pore structure and fluid uptake of the Yeso, Abo, and Cisco Formations in the Permian Basin in southeast New Mexico, USA

Abstract

There is a need for a petrophysical understanding of producing formations in the Northwest Shelf in southeast New Mexico. Working with six rotary sidewall core samples (dolomite, limestone, and sandstone), we have investigated the utility of mercury injection capillary pressure (MICP), contact angle, fluid imbibition, as well as logging analyses to evaluate the characteristics of pore structure and fluid uptake of the Yeso (Paddock and Blinebry members), Abo, and Cisco Formations. Results from MICP tests provide a variety of pore structure data including bulk and particle densities, porosity, pore-throat size distribution, permeability, and tortuosity. Two Abo dolomite samples indicate the highest porosities at greater than 15%, compared with 4%–7% for the other two dolomite samples from the Paddock and Blinebry members within the Yeso Formation. Most of the pore-throat sizes for these samples fall within the range of [Formula: see text]. The only exceptions are the Paddock member sample, which possesses a higher percentage of larger pores ([Formula: see text]), and the dolomite sample from the Cisco Formation, which has most of its pore-throat sizes falling within the range of [Formula: see text]. From contact angle measurements, all samples are found to be oil-wet because n-decane spreads onto the rock surface much quicker than the other hydrophilic fluids (deionized water and brine). Imbibition tests reveal well-connected pore networks in all samples, with the highest values of imbibition slopes being recorded for the Abo samples. In addition, we used the crossplot of porosity and water saturation obtained from log analyses to derive a value for permeability at field scales. The porosity and permeability values, from log analyses as well as laboratory MICP and gas pycnometry-permeameter measurements, and at different observational scales, are generally consistent. The overall results provide a snapshot of the pore structure characteristics, from limited samples but using integrated approaches and scales, of these formations.