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Abstract

Enhanced oil recovery (EOR) innovations have paved the way for newer, more exciting technologies that provide improved EOR processes. Among the latest advancements are new methods for describing the reservoir, improved downhole instrumentation, and new chemicals engineered to improve recovery. These are just a few of the innovations available to geoscientists and engineers in their quest for better reservoir description and applications of improved EOR processes.

The U. S. Department of Energy (USDOE) has sustained development of many of these technologies. This paper highlights some of the USDOE championed laboratory and field applications work in steamflooding, biotechnology, alkaline-surfactant-polymer (ASP) formulations and chemicals to increase carbon dioxide viscosity. Future challenges in applying EOR using microhole technology are also discussed.

Advancements in steamflooding include mechanistic studies to better understand fluid and heat flow conditions. The biotechnology work discussed used resident microflora to selectively plug porous zones and increase oil recovery. The alkaline-surfactant-polymer work summarizes the laboratory and field work conducted in support of a shallow reservoir ASP application. The laboratory search for chemicals to increase the viscosity of carbon dioxide is also discussed.

A new area of work is microhole technology-wellbores that are less than 2-1/4 inches in diameter. Included in this discussion are the challenges of developing the tools, the market, and the expectation of delivery of improved oil recovery chemicals utilizing a microhole.

Introduction

Today over 50% of the world's oil fields are under waterflood. Waterflooding is often the most promising and economical method for increasing oil recovery. Improved oil recovery (IOR) began in June 1929 with the publication of "The Disposal of Oil Field Brines" by Ludwig Schmidt and John M. Devine. This U. S. Bureau of Mines (predecessor to the oil and gas technology section of the USDOE) book is the classic waterflooding investigation. The innovations of EOR methods have since lead the way for newer, exciting technologies-technologies that when applied provide improved recovery processes.

This paper will discuss some of these innovations both from a laboratory and a field application perspective. The five areas reviewed are (1) mechanistic studies in steamflood operations, (2) biotechnology development with field applications, (3) ASP specifications and field applications, (4) carbon dioxide viscosifiers, and (5) microhole technology applied to drilling and EOR injection well applications.

Steamflooding Technology

Steamflooding technology is the most often applied EOR method. Even though this technology has been practiced for about 40 years, there are still unanswered technical questions. To address some of the questions, USDOE has been involved in sustaining steamflood research for over twenty years. One unanswered question is relative permeability measurement methods reviewed below.

Relative Permeability Laboratory Studies

The project objective¹ was to understand the limitations of conventional methods for calculating relative permeabilities. The industry standard for interpreting relative permeability measurements is the Johnson, Bossler and Neumann² (JBN) method. It is known that capillary forces affect relative permeabilities calculated by the JBN method. Errors can be introduced during low rate displacements and when calculating relative permeabilities that assume a uniform initial saturation distribution for history matching.

In this work the pressure drop and recovery data generated from 2-D numerical simulations were used to study the errors introduced in the JBN calculated relative permeability curves. The results indicate that core saturation gradients obtained from the JBN method show large errors at low water saturations.

Using the x-ray computerized tomography (CT) scanner to measure in situ saturations, it was observed that even at relatively high fluid flow rates there are saturation gradients after drainage displacements. These saturation gradients cause additional pressure drop through the core. It is therefore recommended that control experiments be conducted using some in situ saturation measurement technique to determine the extent of the capillary end effects and core saturation gradients.