How do you evaluate the impact of parasequence heterogeneity on fluid flow and recovery?

1 Parasequence definition and identification

A parasequence is a relatively conformable succession of genetically related beds or bedsets bounded by marine flooding surfaces or their correlative surfaces. Parasequences can be identified by their vertical stacking patterns, facies changes, and biostratigraphic markers. Parasequences can be grouped into parasequence sets, which are bounded by major flooding surfaces, and form the building blocks of systems tracts within a sequence.

2 Parasequence heterogeneity and fluid flow

Parasequence heterogeneity refers to the variability in the petrophysical and geomechanical properties of the rocks within and between parasequences. Parasequence heterogeneity can be caused by factors such as sediment supply, accommodation space, depositional energy, diagenesis, and tectonics. Parasequence heterogeneity can influence the fluid flow in the reservoir by creating barriers or conduits for fluid movement, affecting the connectivity and continuity of the pore network, and modifying the relative permeability and capillary pressure of the fluids.

3 Parasequence heterogeneity and recovery

Parasequence heterogeneity can also affect the recovery of hydrocarbons from the reservoir by influencing the displacement efficiency, sweep efficiency, and drainage efficiency of the production process. Parasequence heterogeneity can create preferential flow paths or bypassed zones for the injected fluids, resulting in uneven sweep and low displacement. Parasequence heterogeneity can also trap residual oil or gas in isolated pores or compartments, reducing the drainage efficiency and increasing the residual saturation.

4 Parasequence heterogeneity evaluation methods

To evaluate the impact of parasequence heterogeneity on fluid flow and recovery, several methods can be used, depending on the data availability and the scale of interest. These methods include core analysis, well logging, seismic interpretation, geostatistical modeling, and reservoir simulation. Core analysis can provide detailed information on the rock properties and fluid distribution at the pore scale. Well logging can measure the vertical and lateral variations of the rock properties and fluid contacts at the wellbore scale. Seismic interpretation can identify the parasequence boundaries and geometries at the field scale. Geostatistical modeling can generate realistic representations of the parasequence heterogeneity at the reservoir scale. Reservoir simulation can predict the fluid flow and recovery behavior under different scenarios at the reservoir scale.

5 Parasequence heterogeneity evaluation applications

Evaluating the impact of parasequence heterogeneity on fluid flow and recovery can have various applications for reservoir characterization, management, and optimization. For example, by understanding the parasequence heterogeneity, one can better estimate the original oil or gas in place, determine the optimal well locations and trajectories, design the most effective injection and production strategies, monitor the reservoir performance and identify any issues, and optimize the recovery factor and economic value of the reservoir.

6 Parasequence heterogeneity evaluation case studies

Several case studies have demonstrated the importance and benefits of evaluating the impact of parasequence heterogeneity on fluid flow and recovery in different types of reservoirs. For instance, in a clastic reservoir in the North Sea, parasequence heterogeneity was used to explain the anomalous water production and pressure behavior observed in some wells. In a carbonate reservoir in the Middle East, parasequence heterogeneity was used to improve the reservoir modeling and simulation accuracy and reduce the uncertainty in the recovery forecasts. In a tight gas reservoir in North America, parasequence heterogeneity was used to optimize the hydraulic fracturing design and enhance the gas production and recovery.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?