1. INTRODUCTION AND PROJECT DESCRIPTION

1.1 Reasons for Performing Project
1.2 Project Objectives
1.3 Project Execution

1. INTRODUCTION AND PROJECT DESCRIPTION

1.1 Reasons for Performing Project

Often less than half of the oil in place in reservoirs is recovered. In reservoirs where fractures play a significant role in reservoir permeability, the ultimate recovery can be less than 10% of the estimated oil in place. The remaining oil is either technically or economically unrecoverable. This unrecovered oil represents a significant potential resource for the mature petroleum industry in the United States, in which the potential for new, large discoveries of oil is small.

This project develops the DFN approach as an attractive method for improving the ultimate recovery from fractured oil reservoirs. The project focuses on development of a better understanding and design of tertiary recovery processes specifically tailored to fractured oil reservoirs. The research is designed to exploit data and collect additional information gathered during a field trial of Thermally-Assisted Gravity Segregation (TAGS), but is also applicable to other types of enhanced oil recovery processes in fractured reservoirs. Fluid-contact management, applied in advance of the TAGS process has proven its value through a 20% increase in field oil production during the previous 30 month's use at the Yates Field in Texas. The TAGS process should be applicable to many other fractured oil reservoirs in the United States.

Efforts under this project will explore and extend three areas of performance enhancement:

1. Thermally-assisted gravity segregation to improve fractured reservoir oil production through improved oil mobility and gas-cap pressure. Additional fracture network characterization will enhance continued application and economic viability of this process.
2. Completions have been deepened to demonstrate the optimum oil withdrawal efficiency by completing wells at the base of the unconfined oil columns. Fracture network characterization will improve recognition of near-well fluid "cone" management options in fractured reservoirs for efficient withdrawal.
3. Fracture network characterization will enhance the application of novel thermal recovery processes designed to economically mobilize the high oil saturation typically remaining in the matrix surrounded by highly connected fractures. The fracture network may be envisioned as a natural heat exchanger for aerial and vertical reservoir segregation of heat carrying injected steam and mobilized reservoir fluids which will then be produced from separate (poorly connected) branches of the fracture network.

1.2 Project Objectives

The project objectives are as follows:

1. Development of methods to generate 3D discrete feature network (DFN) models for fractured reservoirs in which the fractures are constrained by tectonic and geological processes;
2. Development of data analysis tools to support the development of DFN models based on data generally available for fractured reservoirs;
3. Field evaluation of the use of DFN models to predict TAGS processes at the Yates Field, TX, a major fractured reservoir.
4. Development of a state-of-the-art method for transferring technology and disseminating research results worldwide.

1.3 Project Execution

This project is being carried out as an industry and university collaboration. Golder Associates, Seattle WA provided project management. The project manager is Dr. W. Dershowitz. Golder Associates also provides technology development and demonstration, and technology transfer. Golder Associates has developed and tested the project software, and maintains the project web site for technology transfer.

Marathon Oil, Midland Texas carries out field tests and contributes project data for the project study at the Yates Field in Iraan, TX (Tracts 17 and 49). The project coordinator for Marathon Oil is Mr. Eugene Wadleigh. Marathon's participation is contributed to the project.

Theoretical development of the Hierarchical Fracture Model (HFM) and implementation of the HFM model for Tracts 17 and 49 are carried out by the Massachusetts Institute of Technology, under the supervision of Prof. H. Einstein. MIT is also responsible for technology evaluation following the Yates field application.