Integrated Productivity Analysis for Revitalizing a Mature Field in Ecuador

Abstract

Abstract The Lago Agrio field is a mature field in Ecuador. Since 1972, exploitation has been focused on the Hollin reservoir, resulting in a low recovery factor in other reservoirs. The lack of interest in some zones is a result of poor or no productivity obtained during initial production testing. Currently, the field has a high number of inactive wells (65%). This paper describes an integrated productivity analysis conducted to identify well intervention opportunities and to generate a reliable portfolio in a short period of time. Based on the front-end loading (FEL) method, the workflow applied was performed in three phases. In the first phase, carried out in the first five days after analysis of 62 wells with limited information, possible causes of low productivity or inactivity of wells and possible methods to improve production were identified. Estimated production was based on inflow performance relationship curves and grouped by intervention type. During the conceptualization phase, wells with estimated production exceeding 80 BOPD were analyzed in more detail. In the definition phase, pressure transient analysis (PTA) and economic aspects were incorporated. During the visualization phase, the causes of low productivity in reservoirs were determined to be primarily a result of inconclusive initial production testing, high formation damage incurred during drilling, and/or poor primary cementing. At the end of this phase, 30 opportunities for intervention were conceptualized, ranked, and defined. Because the opportunities displayed did not significantly change during the two following phases, the applied workflow provided great reliability as a quick solution to support increasing the production by at least 3,000 BOPD. Finally, the results were corroborated during the execution phase. Percentile values between approximately P5 and P90 of production were obtained from tests for the first seven interventions (approximately 1,900 BOPD). Because of the limited quantity and quality of information and the need to obtain a workover portfolio within a short time period, the standard FEL method was modified. The described workflow could be applied in other analogous mature fields (multireservoirs with limited information and inconclusive initial testing) to generate workover selection quickly and improve well productivity.