Conformance-polymer systems have been successfully applied for many years to control undesired water production from hydrocarbon wells. However, currently available polymers present a number of limitations for high-temperature wells (>250°F) in terms of providing longer gelation times and acceptable thermal stability. This paper presents the successful field implementation of an organically crosslinked polymer (OCP) for high-temperature applications in southern Mexico. The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). To date, more than 450 jobs have been performed with the OCP system around the world to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel pack isolation, fracture shutoff, and/or casing-leak repair. Originally, the OCP system had a limited working temperature range from 100° to 250°F. The upper placement temperature of the system was ~250°F because, above this temperature, pumping times were too short. A recently developed carbonate retarder allows reasonable placement times up to 350°F, without the need for cooling down the formation to obtain enough pumping time. The retarder is not detrimental to the thermal stability of the system. An overview of case histories that used OCP in southern Mexico is presented in this paper. In addition, the development results of the high-temperature conformance polymer are discussed in terms of (1) gelation-time measurement and (2) effectiveness to limit permeability to water and thermal stability in sandpack flow tests at elevated temperatures. To date, more than 70 jobs have been successfully performed worldwide with the OCP at temperatures higher than 250°F. Introduction Excessive water production from hydrocarbon reservoirs is one of the most serious problems in the oil industry. Water cut greatly affects the economic life of producing wells. Unwanted water production is estimated to cost the petroleum industry about $45 billion each year, although accurate records of water production are difficult to obtain (Conformance Technology Manual 1996; Curtice and Dalrymple 2004). The southern region of Mexico presents a major challenge with water management as well. Water production results in extra disposal costs, scale buildup, reduced oil production, and eventually well abandonment (with associated workover costs). Consequently, producing zones are often abandoned in an attempt to avoid excessive water production, even when intervals still retain large volumes of recoverable hydrocarbons. Although natural fractures have a positive effect on oil flow, they also negatively impact water and/or gas flow caused by coning effects or high-permeability streaks between the producing hydrocarbon zone and intervals above and/or below. If these zones contain high mobile-water saturation, they soon will impact the productivity of the hydrocarbon zone. Early water breakthrough caused by edge-water flowing through faults or natural fractures is another common problem in this region. In addition, many of these formations with high-water-management problems produce from intervals with bottomhole temperatures higher than 250°F, hence the need for a high-temperature, porosity-fill sealant in this temperature range.

Conformance-polymer systems have been successfully applied for many years to control undesired water production from hydrocarbon wells. However, currently available polymers present a number of limitations for high-temperature wells (>250°F) in terms of providing longer gelation times and acceptable thermal stability. This paper presents the successful field implementation of an organically crosslinked polymer (OCP) for high-temperature applications in southern Mexico. The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneamine (PEI). To date, more than 450 jobs have been performed with the OCP system around the world to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel pack isolation, fracture shutoff, and/or casing-leak repair. Originally, the OCP system had a limited working temperature range from 100° to 250°F. The upper placement temperature of the system was ~250°F because, above this temperature, pumping times were too short. A recently developed carbonate retarder allows reasonable placement times up to 350°F, without the need for cooling down the formation to obtain enough pumping time. The retarder is not detrimental to the thermal stability of the system. An overview of case histories that used OCP in southern Mexico is presented in this paper. In addition, the development results of the high-temperature conformance polymer are discussed in terms of (1) gelation-time measurement and (2) effectiveness to limit permeability to water and thermal stability in sandpack flow tests at elevated temperatures. To date, more than 70 jobs have been successfully performed worldwide with the OCP at temperatures higher than 250°F. Introduction Excessive water production from hydrocarbon reservoirs is one of the most serious problems in the oil industry. Water cut greatly affects the economic life of producing wells. Unwanted water production is estimated to cost the petroleum industry about ﹩45 billion each year, although accurate records of water production are difficult to obtain (Conformance Technology Manual 1996; Curtice and Dalrymple 2004). The southern region of Mexico presents a major challenge with water management as well. Water production results in extra disposal costs, scale buildup, reduced oil production, and eventually well abandonment (with associated workover costs). Consequently, producing zones are often abandoned in an attempt to avoid excessive water production, even when intervals still retain large volumes of recoverable hydrocarbons. Although natural fractures have a positive effect on oil flow, they also negatively impact water and/or gas flow caused by coning effects or high-permeability streaks between the producing hydrocarbon zone and intervals above and/or below. If these zones contain high mobile-water saturation, they soon will impact the productivity of the hydrocarbon zone. Early water breakthrough caused by edge-water flowing through faults or natural fractures is another common problem in this region. In addition, many of these formations with high-water-management problems produce from intervals with bottomhole temperatures higher than 250°F, hence the need for a high-temperature, porosity-fill sealant in this temperature range.

This paper presents the successful field implementation of a conformance polymer (CP) system used to control undesired gas production in the Cantarell field, a naturally fractured offshore carbonate reservoir in southern Mexico. Gas control is a challenge in this field because high gas-oil ratios (GORs) force the operator to prematurely abandon wells because of gas-handling facility constraints, leaving substantial oil reserves in place. Case histories are presented in which the CP system was successfully applied to reduce undesired gas production to an acceptable level. The CP treatments were tailed in with foam cement to avoid overdisplacement in these fractured, depleted formations. The CP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneamine (PEI). To date, more than 700 jobs have been performed with the CP system around the world, mostly to address excessive water production problems, such as coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and/or casing-leak repair. Similarly, this system provides excellent gas shutoff properties as well. The operating temperature range of this system is from 60 to 350°F. The CP system has been successfully applied to sandstone, carbonate, and shale formations requiring a conformance treatment. This system has been successfully tested to withstand a differential pressure of at least 2,500 psi and is resistant to acid, CO2, and H2S environments. One of the most demanding scenarios for this type of polymer system is stopping gas production, especially in this reservoir where the operator must deal with a combination of high matrix permeability (3 to 10 darcy) and natural fractures. These CP treatments have proven to be economical gas shutoff solutions in difficult well/reservoir environments, yielding significant reduction of gas and/or increased oil production. A detailed description of the wells treated with the CP systems is presented along with one-year production rates after the treatment.

This paper documents efforts to seek alternative and effective treatments for stimulating wells in southern Mexico. It was desired to make treatments more selective, stimulating only areas of oil without contacting contributing areas of water or gas. Stimulation treatments were performed using coiled tubing (CT) and a fluidic oscillator to generate waves of fluid.In the southern region of Mexico, the commercial production of hydrocarbons is in reservoirs that are naturally fractured carbonates with permeability of 25-150 mD, porosities of 5-15%, and are depleted as a result of exploitation. Also, the progress of oil-water contact and gas-oil contact present challenges when designing treatments for stimulation.The damage mechanisms encountered in these wells included blockage by water, paraffin, asphaltenes, and scale depositions, which were generated in the near-wellbore area of the well.To enhance the effect of the stimulation systems, the fluidic oscillator was used to generate a frequency of impact of 300 to 600 Hz on the formation, weakening the damage and efficiently removing it.Commonly, in the southern region of Mexico, 90% of the stimulation treatments are bullheaded; however, in highly deviated wells with two or more pay zones, the use of CT with the fluidic oscillator offers an alternative to increase the effectiveness of acid placement.The synergy of CT, the generation of fluid waves, and the selection system for optimal acid flow through each hole have led to significant results of reduced cost, time, and, in turn, optimizing the volumes of systems required to stimulate wells.In this paper, results achieved by carrying out selective stimulation treatments as well as technical and economic benefits of using CT and the generation of fluid waves as an alternative stimulation treatment for oil wells are presented.

fax 01-972-952-9435. AbstractThis paper presents the results of a successful application of a new-generation polymeric relative permeability modifier (RPM) that enables treatments to reduce water cut without workover equipment. The new RPM can be bullheaded into open intervals without the need for isolating water zones from hydrocarbon zones. This treatment was applied to several wells in the Pemex southern region. As a result of the treatment, the productive life of the wells has been extended, with a gradual decrease in water cut. These results indicate high potential profitability values for mature fields with high water cut requiring a simple, low-cost treatment without the need for workover equipment or shut-in times. The new treatment can increase the hydrocarbon recovery percentage in sands that in all probability otherwise would be destined for abandonment.This paper describes the treatment methodology, which begins with problem identification and an understanding of the origin of the water breakthrough. Next, the paper describes the new technology, which uses hydrophobically modified watersoluble polymers and explains how applying such polymers can control water selectively. In addition, the detailed execution of the treatment is described, followed by the very positive production results of the treatment. The results of this low-investment, high-profit technology are very promising for other wells under similar conditions in which workovers with conventional technologies would be cost prohibitive.