Diagenetic Controls on Reservoir-Scale Enhanced Oil Recovery and CO2 Storage: A Case Study of the Morrow Sandstone, Farnsworth Unit, Texas

Abstract

Complex diagenesis of the upper Morrow B Sandstone, Farnsworth Unit, Texas, strongly impacts performance of enhanced oil recovery and CO₂ storage. Morrow Sandstone lithofacies exhibit a large range of diagenetic processes, including: dissolution of feldspar; precipitation of cements such as kaolinite, siderite, calcite, ankerite, and quartz overgrowths; and compaction. This diagenesis results in a wide variety of pore types and structures that strongly impact flow behavior in the reservoir. Permeability and porosity relationships in the reservoir have allowed classification into several hydraulic flow units, each dominated by a particular pore type. Porosity includes macroporosity with little to no clay filling intergranular pores; microporous authigenic clay-dominated regions in which intergranular porosity is filled with clay; and carbonate-cement dominated regions with little intergranular porosity. Most flow units contain more than one porosity type. In this study we examine the influence of diagenesis on reservoir-scale multiphase flow by integrating results from examination and analysis of the following data sets: thin section observations on paragenesis and types of primary and secondary porosity; X-ray CT images, to quantify and classify pore structure; mercury porosimetry, to obtain pore throat size distributions and capillary pressure curves; permeability and porosity measurements; relative permeability testing using CO₂-brine, CO₂-oil, and oil-brine fluid pairs; upscaling of flow parameters; and finally reservoir-scale simulations. This uniquely rich collection of data sets allows quantification of the performance of the reservoir using distribution of lithofacies, which are in turn determined primarily by the effect of diagenesis on pore structure and composition of pore walls and throats that are contacted by reservoir and EOR fluids. Reservoir performance using water-alternating-gas injection is simulated to demonstrate diagenetic controls on sweep efficiency and CO₂ residual trapping.

Funding for this project is provided by the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018