Pressure and rate transient analysis of artificially lifted drawdown tests using cyclic Pump Off Controllers

Abstract

Abstract In this paper it is shown that the classical well testing equations, with minor adaptations, may be extended to intermittently produced Pump Off Controller (POC) wells. We develop a framework for using the well-known well test equations on continuous POC well testing data. Two types of controller will be examined: the timer-based POC and the load-cell based POC. For the former, a modified constant rate drawdown test will be presented. For the latter, it will be shown that a modified constant flowing bottomhole pressure drawdown test can be applied, or if preferred, a more rigorous type curve. The proposed method has the advantage of allowing approximate determination of reservoir properties at low cost, using frequently available production data. As ageing oilfields frequently have hundreds of wells producing under artificial lift, it is not economical to perform a traditional well test on all wells. Using the proposed method, it is possible to test every well in a field without the expense of a Pressure Build Up (PBU) survey. The high level interpretation is not intended to compare to a high resolution PBU and pressure derivative study, but it does serve as a very useful tool in scoping analysis. The method is useful for identifying wells with high skin or low permeability. Examples shown in this paper validate the theory against a numerical model and shed new light on POC transient decline field data.