Evaluation of Strategies for Enhancing Production of Low-Viscosity Liquids

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 169479, ’Evaluation of Strategies for Enhancing Production of Low-Viscosity Liquids From Tight/Shale Reservoirs,’ by G.J. Moridis, SPE, Lawrence Berkeley National Laboratory, and T.A. Blasingame, SPE, Texas A&M University, prepared for the 2014 SPE Latin American and Caribbean Petroleum Engineering Conference, Maracaibo, Venezuela, 21-23 May. The paper has not been peer reviewed. Production of low-viscosity liquids, including condensates, from tight reservoirs such as shales is severely restricted by the ultralow permeability of such formations, limiting production to a very small fraction, usually less than 5%, of the liquids in place. In this study, the authors evaluate, by means of numerical simulation, several possible strategies to enhance low-viscosity- liquid production from such reservoirs. The objectives of this effort are to remove from further consideration strategies that hold limited promise, and to identify strategies that have potential for further study. Introduction The remarkable success of gas production from tight reservoirs and shale reservoirs has not been matched by similar progress in the production of relatively- low-viscosity liquid hydrocarbons (including condensates) because of the significant challenges to liquid flow posed by the ultralow permeability of such reservoirs. Increasing the recovery of liquids from these ultralow-permeability systems even by 50% over its current very low levels not only will increase production and earnings but will have considerable wider economic implications because the increased recovery will affect reserves and the valuation of companies. The authors’ effort aims to address this issue by using numerical simulation to investigate a wide range of possible strategies for improved liquid production from tight/shale reservoirs. In essence, this is an attempt to provide a baseline mechanistic study that deploys some state-of-the-art tools in reservoir modeling. The paper focuses on determining the baseline performance of various key production methods that are considered standard in the attempt to produce low-viscosity liquids from tight reservoirs and shale-oil reservoirs. These include recovery by use of displacement methods, viscosity-reduction methods, enhanced reservoir stimulation, and combinations thereof. For a discussion of the simulation code and the underlying fundamental equations of flow and transport, please see the complete paper. Fractured-System Description and Subdomain Representation Subdomains. The fractured system in producing tight gas reservoirs and shale-gas reservoirs can be described as a set of interacting subdomains.