For many years, bullhead systems to reduce water production have received a great deal of attention from the oil- and gas-production industry. Water production becomes a major problem as fields mature, leading to higher levels of scale, greater lift requirements, more load on fluid-handling facilities, and increased environmental concerns. Because of the completion techniques used in many wells, protecting the hydrocarbon producing interval effectively during a water-control treatment is not always practical or cost-effective. Bullhead systems offer treatments that do not require zonal isolation and are designed to reduce water production with little or no reduction in oil or gas production.
Previous papers have discussed the laboratory development of a new water reduction system based on the use of a hydrophobically modified polymer. This paper will outline the field implementation of this squeeze-matrix access reservoir-targeting (SMART) water reduction system and will describe some of the successes (and failures) in its implementation. Even though bullhead systems such as this do not seal off water zones and, therefore, do not have the capability to completely stop water production, it will be demonstrated that SMART treatments can be economically attractive. While field-wide, multiwell treatments are attractive from the viewpoint of fully assessing system capabilities, single-well treatments can be beneficial to small and large operators alike.
Excessive water production from hydrocarbon reservoirs is one of the most serious problems in the oil industry. Watercut greatly affects the economic life of producing wells, and it is estimated that unwanted water production costs the petroleum industry about $45 billion a year in the United States alone.1,2 These costs include the expense to lift, dispose of, or reinject this water, as well as the capital cost of surface facility construction, water treatment, and efforts to ensure environmental regulations are met.2
Many methods are available to mitigate water production problems. Among the chemical methods, both sealing and nonsealing systems have been in use for many years. Nonsealing systems are also referred to as bullhead systems, disproportionate permeability modifiers, and relative permeability modifiers (RPMs). RPMs are typically dilute polymer solutions that adsorb onto the pore walls of the formation flowpaths. A large number of such polymer systems have been promoted through the years, and a large volume of literature has been devoted to this topic. One relatively common theme mentioned for such systems has been that they are best applied to layered, heterogeneous formations without reservoir crossflow.
A previous paper3 described the SMART polymer upon which this work is focused. The polymer is a hydrophobically modified water-soluble polyDMAEMA (HMpolyDMAEMA). In the referenced work, the following conclusions were discussed:
Hydrophobic modification appears to improve the brine permeability reduction for both polyacrylamide and polyDMAEMA.
The hydrophobic modification of polyDMAEMA improves the brine permeability reduction in high-permeability sandstone cores at residual oil saturation.
The target goals of 80% brine permeability reduction and much lower oil permeability reduction have been met with the HMpolyDMAEMA.