Analysis and Evaluation of Alternative Concepts in Modeling Tarmats To Conform to Laboratory Investigations and Field Conditions

Abstract

Black-oil reservoir simulators are universally formulated to handle a maximum of three different fluid phases-i.e., oil, water, and gas. The phase identity of tar, occurring in concentrations called "tarmats" within or marginal to petroleum reservoirs, varies widely from highly viscous hydrocarbon fluid to near-solid material. In black-oil modeling of tarmat reservoirs, therefore, considerable challenge is posed in characterizing tar as a drastic departure from the three fluid phases. No published literature provides concentrated details on tarmat modeling with an emphasis on comparative analysis and adaptability of different state-of-the-art modeling techniques. This paper compares the two approaches adopted most often to characterize tar in a modeli.e., as a highly viscous hydrocarbon fluid and as a relatively impermeable rock matrix. Other less commonly used methods that also may be reasonable are not discussed.