Evaluating the Prospect of Oil Production in Tight Winterhouse Formation Rocks in Western Newfoundland

Abstract

The Winterhouse Formation (Port au Port Peninsula, western Newfoundland, Canada) is a lateral equivalent to the Utica and Macasty formations farther west. With hydrocarbon stains and odours as a guide towards a common and regional upper Ordovician hydrocarbon system, Winterhouse rocks may yet contain their own suite of source reservoir and seal strata, with coarser, sandier beds perhaps playing host to other varieties of conventional and unconventional hydrocarbon traps. Hence, addressing basic properties of fluid transmission is an important and unknown variable that needs to be addressed for this formation. In this pilot study, Mercury Intrusion Porosimetry (MIP) is applied to measure the petrophysical properties of a single tight (low porosity, low permeability) quartz-carbonate sandstone sample from a Winterhouse outcrop. As a tool, Mercury Intrusion Porosimetry is strongly dependent on conformity of sample size and shape as a determinant of pore accessibility. Hence two sample types (i) plugs and (ii) cuttings (both real and artificial) are analyzed to explore aspects of core and cuttings preparation and data reduction work flow measurements of storage and transport properties. For artificial "cuttings" a horizontal 2.5 cm core plug and rock fragments are crushed and sieved to replicate fine and coarse fractions. For porosimetry, a Micromeretrics AutoPore IV porosimeter with a maximum pressure of 33,000 psi is used to determine the porosity, pore size distribution, surface area, and bulk density of all samples. Additionally, the FEI Quanta 650 Field Emission Gun (FEG) SEM is used to take images of the pore structure. Mineralogy is determined from the GXMAP measurement mode within FEI Mineral Liberation AnalyzerTM software. A comprehensive analysis corroborating results from MIP and SEM indicates that for these tight rocks, and namely, outcrop plugs, artificial cuttings, and real drill cuttings from a nearby well, all show a similar spectrum of results, but smaller coarse fragments are recommended for reliability. In terms of the Winterhouse strata, it is clear that some of this rock is very tight and highly cemented, but that it also possesses fractures and high permeability values which may make it a good unconventional reservoir. These porosity-permeability results are simply a beginning in a search to understand the petrophysical properties of the strata on the western coast of Newfoundland. The western part of Newfoundland has seen extensive oil exploration efforts in the last few decades, these efforts have resulted in little success. A large degree of this is due to the complex geological history and overall lack of knowledge concerning the structure and diagenesis of these rocks (Cooper et al, 2001). This study will support the new sampling programs in the hope of gaining new insights into potential oil exploitation.