Abstract

Data acquisition design and implementation challenges for mature reservoirs which are targets for Improved Oil Recovery (IOR) applications are discussed in this paper. Examples are provided for Shallow-Shelf Carbonate (SSC) reservoirs in the Permian basin of west Texas.

What Are Mature Reservoirs? Mature reservoirs are defined as properties with additional recovery potential by implementation of advanced reservoir characterization tools and techniques, reservoir management, and/or changes in recovery mechanisms. Attributes of mature reservoirs are depicted in Figure 1, which shows the importance of reservoir characterization as a function of field-development stage. Reservoir characterization and an understanding of heterogeneity become more important for maturing reservoirs as these factors have a profound impact on future reservoir development and management strategies. Mature reservoirs are typically characterized by some type of secondary drive mechanism. A change to a tertiary mode or implementation of other IOR methods may be necessary to extend the economic limit and productive life of the field.

In recently discovered reservoirs, advances in reservoir management technologies and practices allow operators the opportunity to implement timely, judicious, and integrated data acquisition programs (Raza, 1992; Wiggins and Startzman, 1990; Jackson et al., 1993). Typically, data acquisition focuses on use of a team approach (Thakur, 1994; Satter et al., 1993) as illustrated in Figure 2.

A team approach is also important to achieve data acquisition objectives in mature reservoirs. However, the data acquisition situation may be very different from that of “new” reservoirs. The desire and need for IOR may be critical as the economic limit may be rapidly approaching and data required for IOR may not be available. Smaller reservoir size and lower remaining reserves may present economic constraints toward the acquisition of essential data for the implementation of many IOR methods. The lack of production, fluid properties, and other data in the earlier stages of field development may present uncertainties in history matching with numerical simulation methods. This results in unreliable reservoir performance forecasts for IOR. Often, the implementation of data acquisition programs in mature reservoirs present opportunities to enhance near-term reservoir performance through effective reservoir management.

Data acquisition strategies for properties which are being considered for abandonment are not addressed in this paper. Redevelopment of these properties is often required to exploit behind pipe potential and undeveloped zones or horizons.