Interpretation of Wellbore Temperatures Measured using Distributed Temperature Sensors during Hydraulic Fracturing

Abstract

Abstract Tight gas plays often have multiple lenses of producing formations. Limited entry completions became the most cost effective method to complete and produce tight gas wells in these layered reservoirs. The rate and volume of fracturing fluid injected into the different layers has an important role in determining the fracture characteristics. However, due to the restriction of down-hole equipments, it is very challenging to obtain specific injection rate for each perforated zone. Temperature variations in the well bore, outside the casing, are available using new technology such as distributed temperature sensor (DTS) fiber optic cables. The main objective of this study is to relate the well bore temperature changes as measured by DTS data to the wellbore and fractured interval injection rates during a multizone fracturing process. We develop a forward simulation model, based on mass and energy conservation, for calculating the temperature profile and temperature history in the wellbore and in the rock surrounding the wellbore. The model allows for liquid flow into the fractured interval. Subsequently, the model is integrated with an inverse estimation algorithm which is used to estimate flow rates both in the wellbore and into the fractured interval. The estimation algorithm is based on a gradient search method. Our estimation results show a good comparison of the temperature profiles with that observed in the field by using DTS. Also, the model is able to estimate a flow rate history consistent with total field injection volume. This work enables an accurate and quick interpretation of the wellbore DTS data to determine the interval injection rates during a hydraulic fracturing process. Knowledge of accurate interval injection rates and the corresponding fracture characteristics can be useful in designing better limited entry completion that can optimize the fracture length using rate control.