Production of hydrocarbons in unconventional resources is determined by matrix access provided by fractures through target production intervals. Fundamentally, these fractures provide a high permeability pathway for produced fluids from the matrix to be transported to the wellbore. This work presents a new experimental capability to help develop our understanding of how hydrocarbons are mobilized out of the host rock matrix and into the fracture pathway. We've developed a system that allows for the shear generation of fractures through oil saturated core plugs while under representative subsurface stress conditions. Fluid inlet and outlet ports allow for the determination of generated fracture hydraulic aperture and collection of produced oil and gas. Several experimental methods are presented. These included in-situ x-ray real-time measurements of oil production. Oil production was observed to initiate following fracture generation and to increase with subsequent shear displacement. In contrast, gas production was most prominent following significant pressure drawdown.
The determination of petrophysical properties is essential in the accurate prediction of reservoir performance and production strategy. However, traditional techniques have long suffered from limited application to unconventional reservoir samples due to their low permeability and porosity. Alternative techniques have thus been developed to provide measurements of intact or crushed sample permeability and porosity. Pressure decay permeability measurements of intact core samples (e.g. Brace et al., 1968) can be used to estimate the liquid permeability of low-permeability samples, but not without certain assumptions. The gases used in pressure decay permeability measurements are able to access a significantly larger portion of pore space in shales that may not be applicable to the flow of oil. Crushed sample permeability (e.g. Luffel and Guldry, 1992) relies on the same principles in estimating liquid permeabilities from the gas penetration rate of crushed sample material. The inclusion of multiple phases further complicates the application of these measurements in providing no estimates for relative permeability. In light of these difficulties, instead of focusing on understanding the transport and flow of fluids within the matrix of unconventional reservoir rocks, we designed a system focused on determining the effects fracturing has on the production behavior of oil and gas out of the unconventional reservoir matrix.
