Relative Permeability Modifier and Scale Inhibitor Combination in Fracturing Process at San Francisco Field in Colombia, South America

Abstract

Abstract Water production in the San Francisco field in Colombia is characterized by a severe carbonate scaling tendency, particularly in the lower Caballos zone. Following several fracture stimulation treatments which incorporated RPM (Relative Permeability Modifier) in San Francisco field, it was observed that, although the RPM decreased the anticipated water production, there was an undesirable effect in regard to scaling problems. Some wells ended up losing a portion of the increased production which had been gained by using the RPM fracturing process. This decrease in production was attributed to carbonate scaling after the wells were back on production for several months. A well candidate was chosen (San Francisco 60) and laboratory flow tests were performed in representative cores to determine if a detrimental impact would occur in regard to the ability of the RPM to function properly when the scale inhibitor was part of a combined treatment. Based on these results, a combined fracturing treatment which incorporated a water reduction agent (RPM) in combination with a scale inhibitor was performed in the SF 60 well. To our knowledge, this was the worlds first combined application of an RPM and scale inhibitor in a hydraulic fracture treatment. Further, this new systematic approach to two very difficult problems yielded excellent results: Following the treatment, the well increased production by almost 10 fold while at the same time, water cut was reduced by 30%. This procedure reduced the cost of water management and associated scaling problems, which had been common in this field. This new system has created many more fracture stimulation opportunities which in the past had not been considered economically attractive. The work described in this paper is the result of a true team effort (operator/Service company) and describes the focus in solving several production problems (as experienced in San Francisco field) which resulted in a multi-purpose treatment. The net result of the method developed is fewer required stimulation/workover jobs while maintaining the same or increased hydrocarbon production, and less water (which also translates into lower lifting costs). This paper will present the following:Data illustrating the type of production problems being experienced in the San Francisco fieldThe results of approaching the water production issues and scaling tendencies individuallyThe laboratory evaluation techniques and data obtained when combining the individual treatments into a "system"The resulting "job design," treatment, and production response when the combination stimulation/water control/scaling treatment was actually put into practice. Introduction San Francisco is a mature field located in the Middle Magdalena Valley basin in Colombia. This field mainly produces oil [approximately 20,000 barrels of oil per day (BOPD)] from two zones in the Caballos formation: Upper Caballos (UKB) and Lower Caballos (LKB). Development wells are between 3,000 to 5,000 ft and completed in 7-in. cased holes with an average bottomhole static temperature (BHST) of 120°F.1–3 Permanent workover and stimulation are required to maintain production because the following damage mechanisms are associated with the production process in this field:Calcium carbonate scaling (associated with formation water)Organic scaling (paraffin/asphaltenes)Water production (particularly in the wells influenced by the water-injection process in the UKB zone) The RPM treatment for the test well in this field required several phases of operation. Background information, laboratory testing, candidate selection, methodology and operation, benefit agreements, and treatment evaluation are described in the following sections.