Reservoir Saturation Monitoring United with Production Flow Profile for Efficient Reservoir Management -Success Story of Workover Program on S.E. Gemsa Field by Combined Services "Production Logging and Pulsed Neutron Logging Tools"

Abstract

Abstract South East (S.E.) Gemsa is an oilfield located in Gulf of Suez (GOS) in Egypt. Many challenges have been faced in the reservoir and operation management of this field, such as: -Permeability contrast and water breakthrough in high permeability zones.-Non-uniform vertical water distribution.-Lack of water injection support across zones of low permeability.-Down hole scale build up.-Surface facility "bottlenecks". One of the most critical problems was non-uniform water injection breakthrough into well SE-10B, which is a key oil producer in this field. This paper describes the water diagnosis and well intervention procedure carried out on this well over a period of 2 years (2007/2009) and the results achieved. The main objectives of the conformance workover program were: -Reduce the water production.-Produce the non-contributing intervals.-Enhance the sweep efficiency by adding new intervals. SE-10B is a deviated well (41 degrees) equipped with dual completion string to allow non-commingled production from strata with differential depletion and permeability contrast across the reservoir layers. This well was producing with very high water cut (WC) 95% from both strings. The major operational concern was to diagnose the water source; hence it was decided to run the combined Production logging and Pulsed Neutron logging tools to achieve the main objective of Water Shut-off (WSO). The first logging run was in March 2007. The operator designed a workover program based on the interpretation results which showed the sources of main water contribution. Workover-2007 results tended to increase oil rate by 275% (200 bopd to 750 bopd) and WC dropped to 30% in the long string. The short string did not have any water conformance intervention during this workover; it was producing at 98% WC and was shut down. Another campaign was carried out in February 2009 for time lapse analysis and another conformance workover was implemented, which had impressive results. The short string has started producing 520 bopd with zero% WC versus mostly water before WSO. Long string has produced 1500 bopd and 25% WC versus 250 bopd and 65% WC before WSO. The workover achieved a major reduction in WC levels of both strings, and had a significant positive impact on the daily oil rate that increased considerably to more than 300% of the value before the workover. All the objectives defined were achieved. The outcome of the workover program was completely successful and exceeded operator expectations.