Novel Solutions and Interpretation Methods for Transient, Sandface Temperature in Vertical, Dry Gas Producing Wells

Pressure-Transient-Analysis (PTA) is a technique that is routinely used by both Production and Reservoir Engineers for a variety of applications during the lifetime of a producing well. It is initially used for reservoir characterisation and, later on, for well performance monitoring and (wider) reservoir surveillance. The application of high precision, downhole, temperature sensors has resulted in PTA being complemented or replaced by Temperature-Transient-Analysis (TTA). Recent TTA research has shown that comprehensive information on the state of the near-wellbore zone and fluid flow rates and composition can potentially be derived from such measurements. However, the derivation and use of TTA solutions is challenging, due to both the small value of the measured temperature change and the more complex nature of the governing physics and equations. In particular, analysis workflows for wells producing gas or gas-liquid mixtures are still lacking since most published liquid TTA solutions cannot be applied in the presence of gas. This paper addresses the missing workflow for a (dry) gas producing well. It presents the derivation of novel analytical transient sandface temperature solutions together with the development and application of workflows for interpreting transient sandface temperature data in vertical, dry gas wells. Estimation of either the flow rate or the permeability. thickness (kh) product is demonstrated using a linearized analytical solution. Further, the radius and permeability of a near-wellbore zone of reduced permeability (due to formation damage) can be determined by tracking changes in the temperature transient using the thermal radius of investigation concept. The complete interpretation methodology has been validated by a bespoke numerical model and its application illustrated by case studies. The developed solution and workflows provides a simple and fast method for interpreting sandface temperature data. They will be invaluable for well testing and monitoring applications. It is a major step forward in the longer-Term project of developing a full-spectrum of TTA methods for multiphase (gas-liquid) producing wells.