First Application of Progressing Cavity Pumps for Appraisal Well Testing in the Ugandan Albertine Graben Basin

Abstract

Summary Over 28 production well tests and two interference tests have been conducted in the Albertine Graben basin in Uganda since the first oil discovery in 2006. The Uganda crude is moderately viscous, and low-gas/oil ratio (GOR), and later discoveries were mostly in shallow lower-energy systems. In addition, Uganda crude has relatively high pour points and wax appearance temperatures (WATs), which result in flow-assurance challenges during production testing operations. Production challenges brought about by the low energy scenario are offset by high formation permeability (mostly in the multi-Darcy range). Field X was discovered in 2008 by Well X-1, and subsequently appraised by several wells. Zone 1 of Well X-1 was production tested under natural flow without a rig. Although hydrocarbons were brought to surface successfully during the testing operation, the maximum flow rate achieved was approximately 262 BOPD, and a stable flow rate could not be sustained. Fluid-segregation effects distorted the early-time data. In addition, flow-assurance challenges prevented acquisition of late-time response from the pressure buildup (PBU). Therefore, important dynamic information, particularly in regard to flow barriers, was not obtained. A change in completion philosophy was proposed after detailed analysis of the test results. Well X-1 was retested with a new completion design incorporating real-time surface-readout (SRO) pressure and temperature monitoring capability, a hydraulically controlled inflow control valve (ICV), a progressing cavity pump (PCP), and a surface-controlled electrical heat trace system. High-quality well-test data was acquired, and the real-time data was used extensively throughout operations to optimize flow and buildup periods and well operating envelopes. Several challenges were faced during the first completion run, leading to the use of the contingent insert PCP system to retest Zone 1. This paper highlights the first application of a PCP completion in Uganda and describes the challenges faced during the completion and well-testing operation. The experience from Well X-1 has demonstrated that high-quality exploration and appraisal well-test data can be acquired using a PCP completion. Similar well-completion designs will be used in Uganda for appraisal of other discoveries.