Multiple Fractures Transient Response

摘要

The oil and gas industry has long recognized the inadequacy of existing theories to predict the behavior and outcome of some hydraulic fracturing treatments. Data sets compiled over the last two decades are incompatible with the conventional picture of a single planar hydraulic fracture. Multiple fracturing can occur in the near-wellbore region or far field, and the path of multiple fractures can be divergent, such that they grow out of each other's influence zone, as in the case of dendritic geometry, or narrow, as in the parallel geometry. Analytical, semi-analytical and numerical models have been developed for a well intersecting infinite conductivity vertical fracture. A hydraulically induced fracture is usually represented by a thin vertical plane that extends a finite distance from the well. The fracture is created by tensile stresses, and it exists in a single plane and grows in an orderly and predictable manner, in a pattern that can be defined as balanced. This model is not incorrect, but it is not representative of all hydraulic fracturing scenarios. This study presents an analytical model to analyze the transient flow due to near wellbore multiple fractures in homogenous and naturally fractured reservoirs. The model considers arbitrary angles between the fractures. This study also uses a numerical model to calibrate and validate the analytical model. TDS technique is also used to analyze the linear and pseudo- radial flow regimes in order to find fracture length, fracture conductivity and several conventional reservoir parameters, e.g. permeability, wellbore storage and skin factor. Multiple fractures create more surface area in direct communication with the wellbore. As a consequence greater volume of fluid can be produced from the wellbore per unit time. While fracture treatments continue to be designed using the best tools and techniques available, geometry estimates from fracture models have been difficult to verify. Pressure transient analysis is one of the fracture diagnostic techniques available to fill this knowledge gap, improving our understanding of hydraulic fracture behavior. It is an excellent calibration tool because it lets us evaluate the effective length of the fracture, which is the better length to use in history matching. Also, regardless of the application, identifying and understanding fracture complexities can lead to improved treatment designs, better completion strategies, and the potential for significant economic rewards through improved well performance and/or reduced completion cost.