Well stimulation for production or injection enhancement in mature fields is a key and challenging task. Loss of reservoir energy due to pressure depletion coupled with complex damage scenarios existing in adverse petro physical environments can become restrictive factors for the proper performance of conventional liquid based chemical stimulation systems. Main limitations are normally related to high interfacial tensions preventing optimal well´s clean up and cost-effective achievable penetrations. This work presents a new well stimulation concept in which the carrying system is gas instead of liquid. The overall study will be presented in 2 parts. Part I will discuss basic physical questions related to treatment durability as a function of deployment method (continuous dispersion vs liquid batch gas displacement) for at least two damage scenarios of particular interest: asphaltene deposition and condensate blockage. A basic mechanistic simulation is also presented for benefit estimations at well scale. Part II will focus on field trials design and execution using micellar and/or fluoropolymer type of chemistries that exhibited the best performance when tested under laboratory conditions. Experiments herein presented were done in formation sandstone cores simulating reservoir conditions. It is shown that natural gas when used as the carrying system to deploy conventional asphaltene dissolution and condensate removal chemistries enhances both Ko re-establishment and treatment durability as compared to equivalent liquid-based applications. Additional studies are being performed to maximize the effectiveness of the GaStim concept. Sensibilities to gas type (N2, CO2), added chemical and dosages as long as field trial documentation will be presented in part II of the present work.GaStim concept is presented as a novel chemical stimulation technique potentially allowing deeper penetrations and better chemical adsorptions. Its potential, although still not fully undiscovered, is certainly supported by higher Ko reestablishment values and longer treatment durabilities observed.

This work presents the concept, progression, execution and results for a successful field implementation for a new technique to create insitu blocking foams in a gas condensate naturally fractured reservoir by the injection of the foaming agent dispersed in the hydrocarbon gas stream. This new technique aims at simplifying the operation and reducing the footprint and costs for the deployment of EOR foams in gas injection based projects. It also helps to overcome the disadvantage of limited reservoir volume of influence obtained by the SAG technique. The selected field area for the pilot was confirmed to be naturally fractured dominated both by the production and gas injection performance. The field area had only one oil producer and one gas injector, so monitoring the results of the pilot was simplified. The operation was carefully planned so that a ramp up in foamer solution concentration could be implemented at the field, and the response of the gas injector well could be monitored in real time. Additionally, a gas tracer program was implemented to track the fly times of the gas prior and after the dispersed foam treatment. About 1000 Bbls of foaming solution were dispersed in the hydrocarbon gas stream in one gas injector of a gas condensate Piedemonte field, whose injectivity performance was confirmed to be highly influenced by the natural fractures. Base gas injection conditions were about 30 MM scfd at 3800 psi WHIP. Once the dispersed foamer injection started, the gas injectivity in the well was progressively reduced to the point of increasing the WHIP to ~5000 psi, and the final gas rate was half of the base. The oil production well influenced by this injector changed its performance showing an increasing ramp in oil production and a reduction of the gas oil ratio (GOR) after the dispersed chemical injection period. The tracking of the gas tracers evidenced a delay in the gas fly times between the injector and the producer wells of two fold (63 days Vs 28 days), as a consequence of the dispersed foam treatment. This is the first time a successful foam EOR field pilot is done in a naturally fractured reservoir by the injection of the foaming agent dispersed in a hydrocarbon gas stream. It is believed this new foams technique could also be extended to other non-condensable gases at field operating conditions like CO2, Nitrogen, Air, and Flue Gas.

This paper presents the development and successful implementation of the Foams technology as an effective EOR mechanism to improve the sweep efficiency of the gas injection in the Piedemonte fields. It also shows the process of optimization of the technology to adapt it to the Piedemonte operating conditions, which is based on massive hydrocarbon gas reinjection, and how this process led us to be at a state of the art position in this technology. The methodology to adapt and further develop the foam EOR technology in Piedemonte was based on the Capital Value Process (CVP). It starts with a screening exercise, passes through a technical assurance including applicability, fluids compatibility, modeling and coreflooding tests at reservoir conditions. Finally, the specific solution is implemented in the field to confirm effectiveness. Initially the foams were deployed using the conventional Surfactant Alternating Gas (SAG) technique, but then the technology was optimized to better suit the operating conditions of the fields, and the last interventions have been done dispersing the foamer chemical in the gas stream. This technology has been implemented in most of the fields in the Piedemonte and has proved success since the early implementation pilots in 2011. Implementation started in the Cusiana field, which is a matrix dominated system, and then moved to the naturally fractured and low porosity reservoirs located in the Recetor and Floreña fields. In all the cases, the implementation of foams has rendered positive results reflected in incremental oil production and flattening of the Gas Oil Ratio (GOR) at the influenced producer wells. The new developed dispersed Foams technology has been as effective as the conventional SAG in the jobs performed so far, with the advantages of requiring less surface equipment, and water consumption than SAG jobs. Benefits from Foams implementations so far add up to about 0.65 MM STB. Main conclusions from this project are i) The foams EOR technology is fully applicable in the Piedemonte fields to improve the gas sweep efficiency and increase final oil recovery. ii) A new foam deployment technique based on the injection of the foamer chemical dispersed in the gas stream was developed, and proved effectiveness at the field. The work is innovative in two ways: i) Effectiveness of foam as a technology to improve gas sweep efficiency in naturally fractured dominated systems was proved. ii) A new foam deployment technique based on the injection of the foamer chemical dispersed in a non-condensable gas stream was developed. Also this new foam EOR technique can be extrapolated to any other field operated under gas injection.