Reservoir Management Ingredients for Optimizing the Water-Injection Performance in Small and Medium-Sized Fields

摘要

Greater Unity a multilayered clastic reservoir in Sudan is a conglomeration of number of fault blocks- lacustrine deposits of late cretaceous age. Reservoir characteristics are mostly heterogeneous with varying degree of heterogeneities both vertically and horizontally. Reservoirs are highly undersaturated and have poor aquifer support. Rapid pressure decline was observed in early phase of production, severely affecting the performance of pumps resulting into frequent failures and causing sharp production decline. Water injection in low pressure mode was resorted in some blocks. Failure rates of ESP and PCP reduced significantly as dynamic fluid level (DFL) increased noticeably, provided sufficient submergence, and improvement in efficiency of the pumps. Significant decline in injectivity in Aradeiba formation compelled to change the strategy of injection. Step rate tests were the guiding factor for selecting the low and high pressure injections and also stimulation. Paper discusses application of diagnostic methods like Hall plot, Jordan plot and other empirical relations using Pressure, injection and production data for understanding and improving the injection process. Profile modification for better conformance control gained early importance in view of smaller sizes of the pools. Nonparametric statistical method known as Spearman rank analysis has been used to understand and analyze the degree of communication between injectors and producers. This analysis quickly identifies the communication between injectors and producers, or lack of communication and helps in understanding the response of injection. Preferential flow trends are reflected by the correlation in rates between injectors and producers alongwith lead time response of injection on production. Paper illustrates the important ingredients which can add value to asset and improve the reserves and overall development strategy. Therefore, it is highlighted that success and failure of water injection project depends on why, when, where, what, how and how much to inject, plus what will happen to the formation once the water injection starts.