Field Determination of Fracturing Parameters for Overpressure Calibrated Design of Hydraulic Fracturing

Abstract

ABSTRACT This paper proposes modifications to test procedures, currently in use in the industry, and presents techniques for design and analysis of hydraulic fracture tests. The proposed approach is used for an accurate determination of the fracture overpressure and the total leak-off coefficient which are necessary for the overpressure calibrated design of hydraulic fracture stimulations. The unified approach of performing and analyzing micro and minifrac tests increases the accuracy and reliability of test results. The test procedures account for the real in-situ conditions of the borehole, formation, and the created fracture. The test performance and data analysis are an on-site interactive process that quantifies these in-situ conditions and optimizes accordingly the controlling test parameters, such as the flow rate and pumped volume. The calculations used in the on-site design and analysis of hydraulic fracture tests can be programmed on a hand-held calculator. A brief discussion of the conventional micro and minifrac tests is presented. Limitations of this conventional approach are identified and illustrated by two examples. The requirements for an accurate determination of the minimum in-situ stress are formulated and modified test procedures which satisfy these requirements are proposed. The theory and procedures for the design and the interpretation of hydraulic fracture tests, uniformly used for both micro and minifrac tests, are outlined. Two field examples demonstrates the presented theory and test procedures.