Overview of Tight-Gasfield Development in the Middle East and North Africa Region

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 126181, ’Overview of Tight-Gasfield Development in the Middle East and North Africa Region,’ by Ahmed Shehata, SPE, and Ahmed Aly, American University Cairo, and Lee Ramsey, SPE, Schlumberger, prepared for the 2010 SPE North Africa Technical Conference and Exhibition, Cairo, 14-17 February. The paper has not been peer reviewed. As operators turn to unconventional gas reservoirs for new supplies, the need to optimize the capacity and recovery potential from this type of reservoir has risen. There is an emerging focus on tight gas reservoirs in the Middle East and North Africa. Challenges of developing these difficult resources are presented along with the role of modern technologies in managing tight gas and in improving recovery factors and strategies for field development. Introduction Unconventional gas resources are a large component of remaining natural-gas resources in the Middle East and North Africa. Many of the developed low-permeability reservoirs are sandstone, but significant quantities of gas are produced from low-permeability carbonates, shales, and coalbeds. To optimize development, geoscientists and engineers must determine the optimum number and placement of wells, along with the drilling and completion procedures for each well. Often, more data and engineering manpower are required to understand and develop unconventional reservoirs than are required for conventional reservoirs. Challenges to Development It is important to target zones that show the greatest structural and sedimentary heterogeneity, where higher permeability creates promising pay zones. However, detecting these zones is very difficult because of limited variation in the nature of the rock and, therefore, in its acoustic impedance. Low Permeability and Low Porosity. As Fig. 1 shows, reservoir rock can be characterized by two parameters: porosity and permeability. For tight gas reservoirs, the rocks have both low porosity and low permeability, and gas, even with low viscosity, cannot move easily. To exploit such reservoirs, permeable pathways, such as fractures or multiple laterals, must be created. Producing Reservoirs. The large quantities available and long-term producibility of these natural resources make them significant. The low productivity typical of tight gas reservoirs usually is insufficient to ensure the economic viability. Therefore, as much of the reservoir volume as possible must be connected to the well. Economic Estimation. With low permeability and high geologic heterogeneity, production of tight gas assets requires high well densities and costly stimulation treatments, usually hydraulic fracturing. These tight-gas-development projects are very sensitive to gas-price fluctuations. Financial returns, therefore, depend primarily on the volume of gas that an average well delivers relative to the costs of drilling and stimulation. Tight gas fields require sophisticated drilling activity (which leads to high cost) and ongoing stimulation to maintain gas production. Therefore, the investment profile for tight gas is different from that of a conventional reservoir. Also, techniques that work in one tight basin might not work elsewhere.