Reservoir Characterization of Fractured Gas Reservoirs Through The Integration of Dynamic Data

Abstract

The productivity and performance of fractured reservoirs are strongly controlled by the fracture network distribution. Appropriate characterization of the effective fracture network is essential to accurately quantifying production forecast and reserves. Despite the known importance, it is still very challenging to properly evaluate natural fracture connection. The S Field is a giant gas field producing from fractured reservoirs which has the capability to produce more than 800 MMscfd at the field level and individual well deliverability as high as 300 MMscfd. With the historically strong data acquisition program and recent well results being outside of the expected range, the subsurface team has completed a re-characterization study to further understand the key subsurface uncertainties and find remaining or new resource potential. Considering non-uniqueness characteristic of dynamic data analysis, reservoir engineers may tend to repeat an existing interpretation over new reservoir studies, unless there is evidence to change. The downside to this reliance is the team may miss other possible interpretations of the model that were overlooked in the past. The new model may add a new point of view in the field characterization which could explain unexpected well results. In this dynamic data evaluation, the methods primarily rely on the short-term high precision data (Pressure Transient Analysis) and the long-term dynamic production (Rate Transient Analysis). These analyses make it possible to correctly evaluate the reservoir properties around the well, such as formation permeability, well skin, drainage radius and dynamic reserves to characterize the reservoir at a larger scale and reveal the reservoir connectivity and flow barriers in the prevailing heterogeneity. Apart from the dynamic data evaluation, this paper also addressed the integration of dynamic data with the 3D seismic interpretation and geological model which define faulting or fracturing relationships that drive the well productivity. Furthermore, it helps to refine the future development strategy options for the field.