Reservoir Connectivity: Definitions, Strategies, and Applications

Snedden, John W.¹, Peter J. Vrolijk², Larry T. Sumpter¹, Mike L. Sweet¹, Kevin R. Barnes¹, Elijah White¹, M. Ellen Meurer³ (1) ExxonMobil Upstream Research Company, Houston, TX (2) ExxonMobil Upstream Research Co, Houston, TX (3) ExxonMobil Upstream Research Co, Houston,

Reservoir connectivity and compartmentalization is a critical area of research and business application. Surveying the general terrain of reservoir connectivity reveals significant differences among companies and academics in how it is defined, measured, modeled, and acted upon. However, almost all agree that connectivity is a function of the field structural framework, reservoir stratigraphy, and fluid characteristics.

Our approach to reservoir connectivity is to define two entities: "static" and "dynamic" connectivity. Static connectivity describes the native state of a field, prior to production start-up. Evaluation of static connectivity is the basis for proper assessment of original hydrocarbons in place and prediction of fluid contacts in unpenetrated compartments.

Dynamic connectivity describes movement of fluids once production has begun. Initiation of production actually perturbs the original fluid distributions as pressure and saturation changes proceed in a non-systematic fashion across field compartments. Barriers and baffles play a varying role over the field life, in some cases breaking down over time, suggesting that these are not true compartment boundaries. Analysis of dynamic connectivity is essential to estimating ultimate recovery from a field.

We have developed a technology called "Reservoir connectivity analysis" (RCA) to investigate field compartments and associated connections. A compartment is precisely defined as a trap which has no internal boundaries (e.g., faults, channel margins) which would allow fluids to reach equilibrium at more than one elevation (over geologic time scales). Connections between compartments include fault juxtaposition windows and erosional scours between channels. Examples of RCA application and its impact on our fields are discussed. In these mature producing fields, RCA has explained production anomalies, generated new drill well opportunities, and boosted field reserves above original estimates