A New Approach to Hydraulic Fracturing With Relative Permeability Modifiers

Abstract

In Colombia, relative permeability modifiers (RPMs) are often included in fracturing fluids to limit water production in wet producers. However, the results of their application are mixed. Since many reservoirs have an oil/water contact, or are close to an oil/water contact with poorly defined barriers, the fracture propagates into the water with minimal leakoff of the RPM into the fracture faces. In theory, the RPM polymer present in the interstitial water of the fracturing fluid leaks off into the fracture faces, as the hydraulic fracture propagates. For this to occur requires an inefficient fluid with high fluid loss. However, the properties of RPM fracturing fluids are similar to those of conventional fracturing fluids, highly viscous with leakoff control to ensure adequate fracture geometry and proppant placement. These properties favour vertical height growth of the hydraulic fracture and limit RPM leakoff into the fracture faces. These limitations led to the development of a new fluid and placement techniques, with the objective of increasing the success rate of hydraulic fracturing in wet producers. A linear fluid comprised of polyacrylamide and polysaccharide polymers with a viscosity enhancer. The viscosity of which can be adjusted between 100 and 200 cp at 100 sec-1 over a wide range of temperatures. The relatively low viscosity of the fluid aids in limiting the net pressure and the risk of fracture height growth, in formations with low stress profiles. The addition of fibers provides a mechanical means to suspend and transport proppant, when deemed necessary. Hence, high fluid viscosity is no longer required for efficient proppant transport. By adjusting the ratio and concentration of the polymers, it is possible to independently adjust the viscosity and leakoff control of the fluid as a function of the formation permeability and stress profile. Doing so ensures that the desired fracture geometry is achieved while ensuring adequate leakoff to treat the fracture faces. A fracturing campaign using this newly developed fluid in a mature field in Colombia resulted in an incremental oil production of 12%, while decreasing the water cut by 13%. This demonstrated that reservoirs that were not previously considered candidates for hydraulic fracturing can now be treated without increasing the water/oil ratio (WOR). The use of this fluid, along with a new treatment design methodology, makes it possible to hydraulically fracture reservoirs with, or close to, an oil/water contact. This effectively extends the life of mature fields that are approaching their economic limits.