Numerical Investigation for Developing Conventional Tight-Oil Formations in the Middle East

Abstract

The rise in oil production in the United States during the last decade resulted from the development of unconventional tight-oil resources. These are oil accumulations in low permeability formations, which are either source rocks or in a proximity to a source rock. There are other types of tight-oil resources that are located in conventional reservoirs with a low permeability matrix. These can be referred to as conventional tight-oil formations. The objective of this paper is to investigate the characteristics of the development strategies for these formations and how they are compared to unconventional tight-oil resources. Using reservoir data representing the properties of the tight-oil formations in the Middle East, a numerical study has been conducted by a commercial simulator with dual-porosity option. The model can simulate the drilling and the hydraulic fracturing in the reservoir. In addition, the model is coupled with geomechanics to capture the stress changes in the formation. The effects of the natural fracture corridors and water production from nearby aquifers on the performance of conventional tight-oil formations are also studied. Sensitivity analysis is conducted on reservoir data, such as the initial reservoir pressure and initial movable water saturation. The simulation results show that, as in the unconventional tight-oil plays, horizontal wells with hydraulic fractures are the best approach to develop conventional tight-oil formations. However, wider spacing of these horizontal wells is warranted if they are intersecting the natural fracture corridors. High water production from nearby aquifers or high initial water saturation is a major challenge and could jeopardize the development outcomes. In addition, lower initial pressure compared to unconventional tight-oil plays may undermine the initial rates, and, unless the matrix permeability is high enough for sustained economic rates, conventional tight-oil resources may not have some of the favorable features of unconventional tight-oil project economics. This paper illustrates the factors affecting of the development strategies for conventional tight-oil formations. Most of the studies available in the literature focus on the development of conventional high/medium permeability formations or unconventional tight-oil formations. This paper provides insights into the development for a different category of oil resources that has a high potential in the Middle East and other parts of the world.