Hierarchical Organization of Flow Network in Fractured Carbonate Reservoirs: Identification and Characterization of Key Parameters

摘要

From field data, outcrop observations, and ground-waterrnflow studies, this paper illustrates that if the assessment of thernfracture network organization is effectively an important stagernof the reservoir characterization, it cannot be dissociated fromrnthe evaluation of the scale relationships, the relation withrnstratigraphy, and the distribution of fracture hydraulicrnproperties.rnIn Lacq Field, a giant gas field in a fractured carbonaternreservoir, the flow network is assessed through the use ofrndynamic data. Vertical distribution of producing zones showsrna very clear control of effective open fractures by stratigraphy,rnand therefore carbonate lithology.rnIn the same time, producing zones are not located in thernareas in which fracture density is the highest. Same results arernobtained from the observations of in-situ fracture networksrnand water incomes in a tunnel and a subsurface quarry. Itrnclearly demonstrates that fracture density is the not the drivingrnparameter for flows, and could be anti-correlated with fracturerneffective aperture.rnThe computation of equivalent permeability on fracturernmodels shows that fracture aperture distribution (and thereforernhydraulic properties distribution) is a more prevalentrnparameter for uncertainty assessment than fracturerndistribution.rnLastly, the spacing between open producing fracturesrnalong vertical or horizontal profiles show either exponential orrnpower-law experimental distributions, regarding the spatialrncorrelation between geological features. This proves thernhierarchical organization of the flows, together with the needsrnfor an evolution of the simplistic representation of a constantrnmatrix block size within each cell of the dual porosityrnreservoir model.rnThese studies enable to up-date the typology of fracturedrnreservoirs we previously published.