Hydraulic Fracture Diagnosis Using Chemical Tracers

Abstract

In this paper, the use of a single-well tracer test for hydraulic fracture diagnosis is explored. Existing methods for hydraulic fracture diagnosis (e.g. well logging and pressure transient testing) often do not provide accurate or unique solutions, so improved methods are needed. The principle behind the use of tracers for hydraulic fracture diagnosis is the dominance of the fracture on the flow field in a hydraulically fractured reservoir and the strong influence of fracture parameters on the flow field. This will be reflected in the tracer response curves of a single-well tracer test in a fractured well, making the tracer test diagnostic of the fracture and its parameters. Several kinds of tracers (conservative, sorbing, reactive and partitioning) have been tested for their diagnostic value by numerical modeling. The major factors of influence on the tracer response have been identified. These factors are combined in a ratio, the tracer influence ratio, which can be used for the estimation of the product of fracture length and fracture height. The tracer behavior is dispersion dominated, which implies that the tracer dispersivity must be known for the tracer test interpretation, or it could be estimated from another tracer test in the same well ormore » another well in the formation. Extensive sensitivity analyses have indicated that the tracer test is only mildly sensitive to a large number of variables which is beneficial for the purpose of hydraulic fracture diagnosis. A conservative tracer appears to be the best candidate for hydraulic fracture diagnosis using a single-well test since it has the largest diagnostic value when the tracer test is optimized.« less