Determination of Optimum Injection Capacity Using Pressure Transient Analysis

Abstract

Geothermal systems were divided into two classification based on its fluid, liquid dominated system and steam dominated system. Most of geothermal fields in Indonesia are liquid dominated, for example Dieng, Awibengkok-Salak, Lahendong, Ulubelu, Sibayak, and Sarulla (Saptadji, 2018). Developing a liquid dominated field had some impediments in locating injection wells. Pertamina had faced injection well problem in Tompaso Field when they had to decide whether to drill injection or production well (Hastriansyah, 2015). Hastriansyah (2015) used Nodal analysis to evaluate single well injection capacity. However, having more than two injection wells in the same cluster throws a new issue. Nodal evaluation did not evaluate inter well connection. It was questioned how much injection water that reservoir could accept. Would it be the sum of single well injection capacity or less. To answer the questions an interference test should be managed. The data have mainly been obtained by running periodic downhole pressure/temperature survey. Pressure Transient analysis was conducted to model well connectivity. Then, optimum injection capacity was determined by restricting bottom hole pressure at certain value for certain injection period in model.