New correlations for etched fracture width and half-length of acid-fractured wells

Acid fracturing is one of the most efficient well stimulation techniques in carbonate reservoirs. Estimation of well productivity after fracturing is an important issue in acid fracturing design and production engineering analysis. There are some correlations, available in the literature, for estimation of effective wellbore radius of hydraulically fractured wells. However, fracture etched width and its half-length must be known to use these correlations and, to our best knowledge, a simple and correct method for prediction of these parameters has not been reported yet.

This paper presents a couple of correlations for estimation of etched fracture width and fracture half-length considering acid-rock interactions, reservoir and operational parameters. To develop and verify the proposed correlations, we used a large data bank produced by our in-house simulator, which models one-dimensional acid flow through a single hydraulic fracture considering acid-rock reaction and also fluid leakoff to the matrix. The governing equations are solved numerically using finite difference approach and the results were compared with a commercial simulator for verification. It is also explained how the values of etched fracture width and fracture half length, estimated by our new correlations, can be used in the available correlations for prediction of effective wellbore radius.