Exploring the Diagnostic Capability of RTA Type Curves

Abstract The cost intensive oil and gas industry dictates the use of techniques which maximize quality information while minimising rig time. Continuous improvement in data acquisition techniques as well as data interpretation methods has been seen in the recent past. One such modern data interpretation method is the "Rate Transient Analysis (RTA)". Pressure Transient Analysis (PTA) and Rate Transient Analysis (RTA) has been the industry practice for analysis of pressure data. PTA is mainly used for analysis of short-term conventional well test while RTA is used mainly for analysis of pressure and rate data over a long time span. RTA can also be termed as a modern Decline Curve Analysis (DCA) method. Traditional DCA deals with pseudo steady state flow regime and is an empirical / semi empirical method. However RTA deals with transient state flow and the RTA flow equations have analytical origin. RTA is known to give convincing estimates of reservoir parameters when low frequency (weekly or monthly) production data is available. However recently, considerable amount of work has been done to study the applicability of RTA on high frequency well test data. The utility of PTA for well test interpretation is well known among reservoir engineers and it has a rich literature base. However there exists several "complex scenarios" where conventional PTA interpretation becomes non feasible. Under these scenarios RTA proves to be a promising interpretation tool. Also a large pool of literature is available on the diagnostic capabilities and sensitivity analysis of the PTA type curves. What is not available in literature is the diagnostic power and sensitivity analysis of RTA diagnostic plots. Owing to the need of RTA as a modern data interpretation tool, this paper discusses the diagnostic capability of RTA type curves by generating synthetic models of complex reservoir systems (numerical well test modelling & simulation) and studying the sensitivity of various reservoir parameters on the RTA type curves.