Data-Driven Performance Analysis for Candidate Recognition: A Case Study in a Giant Heterogeneous Carbonate Reservoir

Abstract

In the whole lifecycle of reservoir development, periodic intervention in wells is the daily work of reservoir management, which is essential to production maintenance and workover activity. The identification of actionable plan at well-by-well level is time consuming and inefficient, especially for reservoirs with a considerable amount of wells. Over-reliance on engineer experience also increase uncertainties over reliable plan. The workflow for candidate screening provides a systematic and efficient approach to dealing with this issue. Prior to commencing the process, reservoir static model and dynamic model were updated to meet recent reservoir performance. The first step was to identify potential wells in two ways, including the typical diagram indicating the relationship between production performance and reservoir properties, and the modified heterogeneity index method introduced by Del Castillo et al. After completing candidate recognition, diagnostic analysis was conducted to determine root causes through dynamic analysis of injection/production performance at well/pattern level. Finally, comprehensive evaluation and forecast for workover activities were carried out in terms of technical and economic aspects, which will facilitate appropriate decision making. This workflow has successfully been applied to a giant heterogeneous carbonate reservoir with gas cap. The identified candidates can be categorized into four types. The whole/partial gas cusping wells with a sharp/gradual increasing trend in gas-oil ratio (GOR) are influenced by gas cap. The gas channeling wells with uneven sweep efficiency are attributed to the injected gas overriding in heterogeneous reservoir. The water cusping wells with medium water cut are influenced by bottom aquifer. Accordingly, an integrated optimization plan is proposed to mitigate the outlined risks. The recompletion strategy with Autonomous Inflow Control Device (AICD) and sliding sleeves is recommended for gas/water cusping wells, and results are phenomenal in terms of segmented isolation of high GOR/water cut intervals and delaying gas/water breakthrough. The converting from gas injection to tapered water-alternating-gas (TWAG) through increasing the ratio of water-to-gas in a step wise process has been implemented for gas channeling wells, and an improved conformance is observed. The TWAG project appears to be promising because of high gas/water utilization efficiency and reduced gas cost. This methodological approach provides a generic workflow for conducting an integrated analysis of workover candidates screening and plan making. Reservoir performance will be monitored and maintained in order to ensure efficient reservoir management practice.