Abstract
The productivity of a hydraulically fractured well depends on the fracture geometry and fracture–wellbore connectivity. Unlike other fracture diagnostics techniques, flowback tracer response will be dominated only by the fractures, which are open and connected to the wellbore. Single well chemical tracer field tests have been used for hydraulic fracture diagnostics to estimate the stagewise production contribution. In this study, a chemical tracer flowback analysis is presented to estimate the fraction of the created fracture area, which is open and connected to the wellbore. A geomechanics coupled fluid flow and tracer transport model is developed to analyze the impact of (a) fracture geometry, (b) fracture propagation and closure effects, and (c) fracture complexity on the tracer response curves. Tracer injection and flowback in a complex fracture network is modeled with the help of an effective model. Multiple peaks in the tracer response curves can be explained by the closure of activated natural fractures. Low tracer recovery typically observed in field tests can be explained by tracer retention due to fracture closure. In a complex fracture network, segment length and permeability are lumped to define an effective connected fracture length, a parameter that correlates with production. Neural network-based inverse modeling is performed to estimate effective connected fracture length using tracer data. A new method to analyze chemical tracer data which includes the effect of flow and geomechanics on tracer flowback is presented. The proposed approach can help in estimating the degree of connectivity between the wellbore and created hydraulic fractures.
Highlights
The most common fracture diagnostic methods are microseismic [1,2], tiltmeter [3], well testing [4], radioactive tracers [5], chemical tracers [6,7], pressure interference [8,9,10] and water hammer measurements [11]
A sensitivity fracture closure due to geomechanical effects was modeled using the Barton-Bandis fracture closure analysis was performed to quantify the impact of fracture closure on tracer response curves, tracer model
A sensitivity analysis was performed to quantify the impact of fracture closure on tracer recovery, and hydrocarbon production
Summary
The most common fracture diagnostic methods are microseismic [1,2], tiltmeter [3], well testing [4], radioactive tracers [5], chemical tracers [6,7], pressure interference [8,9,10] and water hammer measurements [11]. Single-well chemical tracer tests for hydraulic fracture diagnosis were first investigated by Gardien et al [6] They used tracer flowback simulations to investigate the influence of fracture geometry on the shape of the tracer response curve. Tian et al [22] presented a partitioning chemical tracer-based method to estimate fracture volume These studies were based on static planar bi-wing fracture geometry and constant fracture conductivity during flowback. Li et al [24] improved previous tracer flowback analysis by conducting numerical experiments by generating the fracture network stochastically, and modeling tracer transport in discrete fracture networks.
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