Modeling and Interpretation of Downhole Temperature in a Horizontal Well with Multiple Fractures

Abstract

Downhole temperature data obtained by either temperature logging or fiber-optic cables has been used to evaluate stimulation treatments and post-stimulation performance of horizontal wells with multiple fractures. Qualitative detection of transverse fractures, poor zonal isolation, and inflow locations is possible; however downhole temperature behavior in those wells is not fully understood from the theoretical modeling perspective.

In this study, comprehensive numerical flow and thermal models for a horizontal well with multiple fractures are presented. The well experiences single phase water flow during injection and shut-in, and gas-water two-phase flow during production. These models are formulated for reservoir and wellbore domains using mass, momentum and energy conservation in transient conditions. These models are coupled to obtain profiles of wellbore and sandface temperature as one of the solutions. These models enable us to simulate field operations in multistage fracturing treatments; injection and shut-in occur alternately for each stage from toe to heel with sufficient zonal isolation. Following the stimulation treatments, these models are used to simulate temperature behavior during production in gas-water two phase flow.

The developed model is applied for several synthetic cases. These case studies show capabilities of the developed model to simulate downhole temperature behavior during processes of injection, shut-in and production. A single fracture case shows injected fluid lowers temperature in the fracture below the geothermal temperature even after one month of shut-in. This affects the temperature interpretation during production. The initial temperature is different than the geothermal temperature, as assumed by previously published work. A synthetic case with five fractures show capabilities of detection of fracture locations from the shut-in temperature profile. The temperature profiles obtained during production show different characteristics of the wellbore temperature and sandface temperature due to fluid mixing in the wellbore.

The developed model was also applied to field cases. One of the field cases shows possibility to evaluate relative fracture length based on the shut-in temperature behavior, and the results are consistent with other measurements qualitatively. The model was also applied for flow profiling of a field case. The estimated flow profile by this work is consistent with the interpretation by production logging tool and the temperature model by a single phase gas. These field cases show capabilities of the temperature interpretation to obtain further understanding of the downhole conditions in a horizontal well with multiple fractures.